研 究 方 法 作 業 報 告 四
光
電
工
程
研
究
所
中英文專利的搜尋
組別 : 第 五 組
學生 : M94L0102 謝 侑 融
M94L0207 楊 欽 堯
一、中華民國專利
先直接進入『智慧財產局』首頁(網址 : http://www.tipo.gov.tw/)
、點選『專利』欄位
進入之後、選擇『專利資料檢索』
進入之後、點選『中華民國專利公報檢索』
進入之後、勾選全部(如紅色圈起來)、然後在按確定
先由『簡易檢索』搜尋、在不限欄位裡輸入欲尋找的關鍵字『TiO2』
結果找到 1109 筆資料
由於筆數太大所以改輸入另一個關鍵字『photocatalyst』、年份不限、
輸入完之後再按『執行檢索』
、共找到 6 筆資料如下 :
第 1 筆 of 本國專利發明公開公報
專利類型
發明
公告/公開號 200536901
專利名稱
光觸媒之塗覆組成物=COATING COMPOSITION OF
PHOTOCATALYST
專利影像
公告/公開日 2005/11/16
期
公報卷期
0322
申請日期
0940315
申請案號
094107908
國際分類號 C09D-001/11
發明人/地址 酒谷能彰 SAKATANI, YOSHIAKI 日本;
/國家
酙口誠一 SAKAGUCHI, SEIICHI 日本
申請人/地址 住友化學股份有限公司 SUMITOMO CHEMICAL COMPANY, LIMITED
/國家
日本;
朝日化學工業股份有限公司 ASAHI CHEMICAL COMPANY, LIMITED
日本
專利代理人 林志剛
摘要
一種光觸媒塗覆組成物,其包括光觸媒、烷氧化矽、鋯化合物、膠態矽石、
及液態介質,其中鋯化合物含量(以鋯原子計)為烷氧化矽莫耳含量(以矽原
子計)之 0.3 至 3 倍,該光觸媒塗覆組成物可形成具有高黏合力黏合至基材
的光觸媒塗覆膜。
專利範圍
一種光觸媒塗覆組成物,其包括光觸媒、烷氧化矽、鋯化合物、膠態矽石、
及液態介質,其中鋯化合物含量(以鋯原子計)為烷氧化矽莫耳含量(以矽原
子計)之 0.3 至 3 倍,該光觸媒塗覆組成物可形成具有高黏合力黏合至基材
的光觸媒塗覆膜。
第 2 筆 of 本國專利發明公開公報
專利類型
發明
公告/公開號 200530028
專利名稱
光觸媒片、其接合方法以及其製造方法 = PHOTOCATALYST SHEET,
METHOD FOR ADHESION AND PRODUCING THE SAME
專利影像
公告/公開日 2005/09/16
期
公報卷期
0318
申請日期
0931214
申請案號
093138687
國際分類號 B32B-027/00
發明人/地址 豊田宏 TOYODA, HIROSHI 日本;
/國家
阿部和廣 ABE, KAZUHIRO 日本;
中田貴之 NAKATA, TAKAYUKI 日本
申請人/地址 太陽工業股份有限公司 TAIYO KOGYO CORPORATION 日本
/國家
專利代理人 洪武雄 ;
陳昭誠
摘要
本發明係提供基材或光觸媒含有層之樹脂不會被光觸媒粒子分解、光觸媒
片之間容易接合、且可獲得光觸媒之光氧化還原效用之光觸媒片、其接合
方法及其製造方法。光觸媒片(1b)由纖維等基材(2)及包覆在基材(2)雙面
之覆膜層(3)所構成,覆膜層(3)係使經磷灰石包覆之光觸媒粒子(4)分散並
以樹脂加以固定而成之光觸媒含有層。此時,在光觸媒含有層表面之經磷
灰石包覆之光觸媒粒子(4),係以具有從光觸媒含有層表面露出之部分之形
式固定。將光觸媒片(1b)彼此接合時,係在不除去各光觸媒片(1b)之光觸媒
含有層之情況下使接合面互相重疊、熱熔著而接合。
專利範圍
本發明係提供基材或光觸媒含有層之樹脂不會被光觸媒粒子分解、光觸媒
片之間容易接合、且可獲得光觸媒之光氧化還原效用之光觸媒片、其接合
方法及其製造方法。光觸媒片(1b)由纖維等基材(2)及包覆在基材(2)雙面
之覆膜層(3)所構成,覆膜層(3)係使經磷灰石包覆之光觸媒粒子(4)分散並
以樹脂加以固定而成之光觸媒含有層。此時,在光觸媒含有層表面之經磷
灰石包覆之光觸媒粒子(4),係以具有從光觸媒含有層表面露出之部分之形
式固定。將光觸媒片(1b)彼此接合時,係在不除去各光觸媒片(1b)之光觸媒
含有層之情況下使接合面互相重疊、熱熔著而接合。
專利類型
新型
公告/公開號 M259809
專利名稱
以理化、生化衛材統合水療、洗淨及環保等多功能之電腦馬桶健康裝置
專利影像
公告/公開日 2005/03/21
期
公報卷期
3209
申請日期
0930428
申請案號
093206552
國際分類號 E03D-009/08 ; E03D-009/02
發明人/地址 李振邦 臺北市大安區安和路 1 段 90 巷 20 號 2 樓
/國家
申請人/地址 李振邦 臺北市大安區安和路 1 段 90 巷 20 號 2 樓;
/國家
木股弘巳 日本
專利代理人 黃世興 臺北市中山區建國北路 3 段 82 號 2 樓
專利範圍
1.一種以理化、生化衛材統合水療、洗淨及環保等多功能之電腦馬桶健康
裝置,係包括:
一水療裝置連接一淨水裝置彼設於一機殼之中,該水療裝置主要為一水療
噴嘴架設於電腦馬桶座上俾將淨水噴射入用者之肛門與直腸中以沖洗糞
便、化解便秘者;以及
一淨氣裝置安裝於該機殼內,以吹出除臭、殺菌帶有負離子有益健康之淨
化空氣者。
2.如申請專利範圍第 1 項之以理化、生化衛材統合水療、洗淨及環保等多
功能之電腦馬桶健康裝置,其中該淨水裝置及該淨氣裝置,係分別藉電氣石
(tourmaline)、光觸媒( photocatalyst )及有效(或有用)微生物群(effective
microorganisms)等理化、生化衛材以發揮除臭、殺菌、及淨化水質與空
氣,兼具保健與環保之多功能者。
3.如申請專利範圍第 1 項之電腦馬桶健康裝置,其中該淨水裝置係包括一
溫水箱其內置入該理化、生化衛材以淨化水質且提供溫水以沖洗人體腸
道、肛門者。
4.如申請專利範圍第 2 項之電腦馬桶健康裝置,其中該光觸媒係以二氧化
鈦製得,彼於光照射下會發生光觸媒作用分解病毒,以殺菌、淨化水質及空
氣者。
5.如申請專利範圍第 1 項之電腦馬桶健康裝置,其中該淨水裝置係設有導
管直接連通電腦馬桶座之前噴頭及後噴頭,以供應前噴洗、後噴洗所需之
淨化溫水流者。
6.如申請專利範圍第 1 項之電腦馬桶健康裝置,其中該水療裝置係包括:
一噴嘴;一輸水管連接該淨水裝置以輸入淨化溫水流者;一支架連設於一座
板上,該座板置於馬桶座上者,該支架用以撐連該輸水管之出口端以可拆卸
地插裝該噴嘴於該輸水管出口端上者。
7.如申請專利範圍第 6 項之電腦馬桶健康裝置,其中該座板藉底部所連設
之至少一對吸盤吸附於馬桶座或瓷座上者。
8.如申請專利範圍第 6 項之電腦馬桶健康裝置,其中該噴嘴製成一長管,於
頂部中央開設一主噴孔,向上噴水入人體直腸之中;於鄰頂部之水管周圍開
設多個下斜噴孔,以側向噴出水流稍微向下以沖洗便物沿著肛門以重力方
向下流進入馬桶之中者。
9.如申請專利範圍第 6 項之電腦馬桶健康裝置,其中該噴嘴係製作為可拋
棄型(disposable),用完就丟,以維衛生者。
10.如申請專利範圍第 1 項之電腦馬桶健康裝置,其中該淨氣裝置係包括:
紫外光燈或加熱燈、風扇、網具等,係設於該機殼內,該網具內及機殼內係
裝入前述之理化、生化衛材含有電氣石、光觸媒及有效微生物群者,令空
氣進入機殼后,透過此等衛材將空氣淨化、除臭,並釋出有益於人體之負離
子及遠紅外線,由設於該機殼上之出風口吹出至馬桶座所處之浴廁內,以提
供一除臭、淨化、環保、健康之清新空氣者。
圖式簡單說明:
第 1 圖係本新型之斜視示意圖。
第 2 圖係本新型之水療裝置示意圖。
第 3 圖係該噴嘴之示意圖。
第 4 圖係本新型之調控裝置示意圖。
第 4 筆 of 本國專利發明公開公報
專利類型
發明
公告/公開號 200507936
專利名稱
光觸媒塗佈液、光觸媒膜及光觸媒構件= PHOTOCATALYST COATING
SOLUTION, PHOTOCATALYST FILM AND PHOTOCATALYST
MEMBER
專利影像
公告/公開日 2005/03/01
期
公報卷期
0305
申請日期
0930429
申請案號
093112043
國際分類號 B01J-035/02 ; C09D-185/00
發明人/地址 田中尚樹 TANAKA, NAOKI 日本;
/國家
鈴木宏和 SUZUKI, HIROKAZU 日本;
小池匡 KOIKE, TADASHI 日本
申請人/地址 宇部日東化成股份有限公司 UBE-NITTO KASEI CO., LTD. 日本
/國家
專利代理人 林志剛
摘要
發明係關於超親水性、暗處的超親水維持性能等優異的光觸媒功能,且可
於有機基材上形成具良好耐久性的光觸媒膜,且安定性優異之光觸媒塗佈
液,以及使用其形成之光觸媒膜;提供包合(A)銳鈦礦型結晶構成之氧化鈦
微粒子;(B)膠體二氧化矽;以及(C)鈦烷氧化物;以加水分解.縮合物構成的
黏合劑,且基於固體成分全體的量,(A)成分含有量為 5-50 質量%(B)成分含
有量,其固體成分為 25-75 質量%,以及(C)成分含有量,以 TiO2,換算其固體
成分為 10-55 質量%之光觸媒塗佈液,以及使用該塗佈液形成的光觸媒膜。
專利範圍
發明係關於超親水性、暗處的超親水維持性能等優異的光觸媒功能,且可
於有機基材上形成具良好耐久性的光觸媒膜,且安定性優異之光觸媒塗佈
液,以及使用其形成之光觸媒膜;提供包合(A)銳鈦礦型結晶構成之氧化鈦
微粒子;(B)膠體二氧化矽;以及(C)鈦烷氧化物;以加水分解.縮合物構成的
黏合劑,且基於固體成分全體的量,(A)成分含有量為 5-50 質量%(B)成分含
有量,其固體成分為 25-75 質量%,以及(C)成分含有量,以 TiO2,換算其固體
成分為 10-55 質量%之光觸媒塗佈液,以及使用該塗佈液形成的光觸媒膜。
第 5 筆 of 本國專利公報 (民國 89-迄今)
專利類型
發明
公告/公開號 00586923
專利名稱
具有光催化作用塗層的人工水晶體
專利影像
公告/公開日 2004/05/11
期
公報卷期
3114
申請日期
2002/10/25
申請案號
091125130
國際分類號 A61F-002/14
發明人/地址 蔡明霖 臺北市文山區興隆路四段一四五巷六十四號三樓 中華民國;
/國家
鄭盛文 新竹市建中一路三十七號十七樓之五 中華民國;
郭宗南 新竹市光復路二段二九八巷九弄十七號四樓 中華民國;
彭素珍 臺北市中正區永春街一五四巷四弄三十九號 中華民國
申請人/地址 蔡明霖 臺北市文山區興隆路四段一四五巷六十四號三樓 中華民國;
/國家
鄭盛文 新竹市建中一路三十七號十七樓之五 中華民國;
郭宗南 新竹市光復路二段二九八巷九弄十七號四樓 中華民國;
彭素珍 臺北市中正區永春街一五四巷四弄三十九號 中華民國
專利代理人 惲軼群 臺北市松山區南京東路三段二四八號七樓;
陳文郎 臺北市松山區南京東路三段二四八號七樓
摘要
本發明揭示一種人工水晶體,其中該人工水晶體的光
學水晶體本體的至少一個表面的至少一部份被塗覆以一由
一光觸媒( photocatalyst )所構成的光催化作用塗層,藉此,
在一光束通經該光學水晶體本體時,該光催化作用塗層被
活化而釋出自由基氧化分解沾附於光學人工水晶體本體表
面的微生物與水晶體上皮細胞,降低白內障病人手術後併
發症[諸如眼內炎(endophthalmitis)與續發性白內障
(after-cataract)]的發生率。
專利範圍
1.一種人工水晶體,其包含:
一光學水晶體本體(optic lens body),其具有一前表面與一後表面;
一從該光學水晶體本體側向延伸而出的水晶體置放構件,用以將該光學水
晶體本體安置在一使用者的一個眼球內;以及
一光催化作用塗層,其係由一光觸媒所構成,且被塗覆在該光學水晶體本體
的前表面與後表面之至少一者的至少一部份上,藉此,在一光束通經該光學
水晶體本體時,該光催化作用塗層被活化而釋出會展現抗微生物效用之自
由基。2.如申請專利範圍第 1 項之人工水晶體,其中該光催化作用塗層被
塗覆在該光學水晶體本體之前表面上。3.如申請專利範圍第 2 項之人工水
晶體,其中該光催化作用塗層被塗覆在該光學水晶體本體之前表面的一個
會接觸一使用者的一眼的眼前房之區域上。4.如申請專利範圍第 1 項之人
工水晶體,其中該光催化作用塗層被塗覆在該光學水晶體本體之後表面
上。5.如申請專利範圍第 4 項之人工水晶體,其中該光催化作用塗層被塗
覆在該光學水晶體本體之後表面的一個會接觸一使用者的一眼的水晶體
囊袋之區域上。6.如申請專利範圍第 1 項之人工水晶體,其中該光催化作
用塗層被塗覆在該光學水晶體本體之前表面與後表面上。7.如申請專利範
圍第 1 項之人工水晶體,其中該光觸媒係擇自於下列群組:一種鈦氧化物、
ZnO、SnO2.WO3.CaTiO3.MoO3.NbO5.KNbO3.SrTiO3.CdSe、
Fe2O3.Ta2O5.Tix(Zrl-x)O2(其中 x=0 或 1)以及 CdS。8.如申請專利範圍
第 7 項之人工水晶體,其中該光觸媒係為一擇自於下列群組中的鈦氧化物:
一氧化鈦、二氧化鈦、三氧化二鈦以及五氧化三鈦。9.如申請專利範圍第
8 項之人工水晶體,其中該光觸媒係為二氧化鈦(TiO2)。10.如申請專利範
圍第 1 項之人工水晶體,其中該光催化作用塗層具有一厚度係介於
2nm-200nm 之範圍內。11.如申請專利範圍第 1 項之人工水晶體,其中該
光學水晶體本體係由一擇自於下列群組中的物質所製成:聚甲基丙烯酸甲
酯、矽酮聚合物或丙烯酸聚合物。12.如申請專利範圍第 1 項之人工水晶
體,其中該水晶體置放構件與該光學水晶體本體是一體成型製造的。13.如
申請專利範圍第 1 項之人工水晶體,其中該水晶體置放構件與該光學水晶
體本體是分開製造的。14.如申請專利範圍第 1 項之人工水晶體,其中該水
晶體置放構件包括兩個腳架,該等腳架各有一端部被側向地連接於該光學
水晶體本體上。15.如申請專利範圍第 14 項之人工水晶體,其中該腳架係
以一擇自於下列群組的物質所製成:聚甲基丙烯酸甲酯、聚丙烯或聚偏氟
乙烯。16.一種用以製造一人工水晶體之方法,其包含下列步驟:
(a)提供一人工水晶體,該人工水晶體包含有:一具有一前表面與一後表面
之光學水晶體本體;以及一從該光學水晶體本體側向延伸而出的水晶體置
放構件,用以將該光學水晶體本體安置在一使用者的一個眼球內;以及
(b)將一光觸媒塗覆於該光學水晶體本體的至少一個表面的至少一部份上
而形成一光催化作用塗層。17.如申請專利範圍第 16 項之方法,其中步驟
(b)是藉由至少一種選自於下列之方式來進行:蒸鍍法、濺鍍法、化學氣相
沉積法、電漿化學氣相沉積法以及物理氣相沉積法。18.如申請專利範圍
第 16 項之方法,其中在步驟(b)中,該光催化作用塗層被形成在該光學水晶
體本體之前表面上。19.如申請專利範圍第 18 項之方法,其中在步驟(b)後,
該光催化作用塗層被形成在該光學水晶體本體之前表面的一個會接觸一
使用者的一眼的眼前房之區域上。20.如申請專利範圍第 16 項之方法,其
中在步驟(b)後,該光催化作用塗層被形成在該光學水晶體本體之後表面
上。21.如申請專利範圍第 20 項之方法,其中在步驟(b)後,該光催化作用塗
層被形成在該光學水晶體本體之後表面的一個會接觸一使用者的一眼的
水晶體囊袋之區域上。22.如申請專利範圍第 16 項之方法,其中在步驟(b)
後,該光催化作用塗層被形成在該光學水晶體本體之前表面與後表面上。
23.如申請專利範圍第 16 項之方法,其中步驟(b)所用的光觸媒係擇自於下
列群組:一種鈦氧化物、ZnO、
SnO2.WO3.CaTiO3.MoO3.NbO5.KNbO3.SrTiO3.CdSe、
Fe2O3.Ta2O5.Tix(Zrl-x)O2(其中 x=0 或 1)以及 CdS。24.如申請專利範
圍第 23 項之方法,其中步驟(b)所用的光觸媒係為一擇自於下列群組中之
鈦氧化物:一氧化鈦、二氧化鈦、三氧化二鈦或五氧化三鈦。25.如申請專
利範圍第 24 項之方法,其中步驟(b)所用的光觸媒係為二氧化鈦(TiO2)。26.
如申請專利範圍第 16 項之方法,其中在步驟(b)之後,一具有一厚度範圍在
2nm-200nm 之間的光催化作用塗層被形成。27.如申請專利範圍第 16 項
之方法,其中該水晶體本體係以一擇自於下列群組中的物質所製成:聚甲基
丙烯酸甲酯、矽酮聚合物或丙烯酸聚合物。28.如申請專利範圍第 16 項之
方法,其中在步驟(a)提供的人工水晶體中,該水晶體置放構件與該光學水
晶體本體是一體成型製造的。29.如申請專利範圍第 16 項之方法,其中在
步驟(a)提供的人工水晶體中,該水晶體置放構件與該光學水晶體本體是分
開製造的。30.如申請專利範圍第 16 項之方法,其中在步驟(a)提供的人工
水晶體中,該水晶體置放構件包括兩個腳架,該等腳架各有一端部被側向地
連接於該光學水晶體本體上。31.如申請專利範圍第 30 項之方法,其中該
腳架係以一擇自於下列群組的物質所製成:聚甲基丙烯酸甲酯、聚丙烯或
聚偏氟乙烯。圖式簡單說明:
第 1 圖是一示意平面圖,其中顯示一個適用於本發明的人工水晶體的結構;
第 2 圖為第 1 圖中所示的人工水晶體的一個示意剖面圖;
第 3 圖是一示意透視圖,其中顯示另一種適用於本發明的可摺疊式平板狀
(plate-type)人工水晶體的結構;
第 4 圖為一剖視圖,其顯示在一光學水晶體本體之前表面與後表面上各形
成有一光催化作用塗層;
第 5 圖為沿第 4 圖所示虛線所取區域之一部分放大的剖視圖,其顯示有一
光催化作用塗層被形成在一光學水晶體本體的前表面上;
第 6A 圖為一示意平面圖,其顯示一於前表面上形成有一光催化作用塗層
的人工水晶體被置於一眼球內,並有一光束通經該人工水晶體的光學水晶
體本體前表面之情形;
第 6B 圖為一示意平面圖,其顯示一於後表面上形成有一光催化作用塗層
的人工水晶體被置於一眼球內,並有一光束通經該人工水晶體的光學水晶
體本體後表面之情形;
第 7A 圖為一示意透視圖,其顯示將帶有由 TiO2 所構成的光催化作用塗層
的光學水晶體本體測試樣品置放於一試驗盤的井孔內,以進行細菌或細胞
生長抑制試驗;
第 7B 圖為一試驗盤井孔之放大剖面圖,其顯示一光學水晶體本體測試樣
品被放在一試驗盤的一個井孔內,且被覆蓋以一細胞懸浮液,再以 UV 光予
以照射處理之示意圖;
第 8 圖為一柱狀圖,其顯示帶有與未帶有由 TiO2 所構成的光催化作用塗層
的人工水晶體對於大腸桿菌的分解效果,其中以 MDA 數值作為測定指標;
第 9 圖為一柱狀圖,其顯示帶有與未帶有由 TiO2 所構成的光催化作用塗層
的人工水晶體對於大腸桿菌存活率的影響;
第 10 圖為一柱狀圖,其顯示帶有與未帶有由 TiO2 所構成的光催化作用塗
層的人工水晶體對於人類水晶體上皮細胞生長之分解效果,其中以 MDA
數值作為測定指標;以及
第 11 圖為一柱狀圖,其顯示帶有與未帶有由 TiO2 所構成的光催化作用塗
層的人工水晶體對於人類水晶體上皮細胞菌存活率之影響。
第 6 筆 of 本國專利公報 (民國 89-迄今)
專利類型
發明
公告/公開號 00452605
專利名稱
紫外線遮蔽材料及其製造方法
專利影像
公告/公開日 2001/09/01
期
公報卷期
2825
申請日期
1998/10/08
申請案號
087116667
國際分類號 C23C-020/06
發明人/地址 松田泰宏 日本 日本
/國家
申請人/地址 日揮化學股份有限公司 日本 日本
/國家
專利代理人 陳燦暉 台北巿城中區武昌街一段六十四號八樓;
洪武雄 台北巿城中區武昌街一段六十四號八樓;
陳昭誠 台北巿武昌街一段六十四號八樓
摘要
本發明係有關紫外線遮蔽材料及其製造方法者。其目
的在提供一種不使由氧化鈦、氧化鈦水合物等或將這些物
質擔持於表面上之無機物質所構成之紫外線遮蔽機能物質
表現所具有的光催化劑( photocatalyst )機能,不使經擔
持及分散之有機基材光老化,而能夠僅表現紫外線遮蔽機
能的紫外線遮蔽材料,以及以黏土礦物包覆紫外線遮蔽機
能物質之方法。詳言之,係以將紫外線遮蔽機能物質以黏
土礦物包覆為其特徵之將紫外線遮蔽材料及紫外線遮蔽機
能物質以黏土礦物包覆而成之紫外線遮蔽材料的製造方法
,該製造方法以包括
a)使黏土礦物分散於溶劑中之步驟、
b)使紫外線遮蔽機能物質分散於溶劑中之步驟、
c)將前述步驟 a)及 b)中製得之 2 種分散液混合並包覆之步
驟、
d)使前述混合物進行固液分離之步驟、
e)將前述步驟 d)製得之固形物加熱之步驟、
為其特徵之使紫外線遮蔽機能物質以黏土機能物質以黏土
礦物包覆之方法。
專利範圍
1.一種紫外線遮蔽材料,係以將紫外線遮蔽機能物質以黏土礦物加以包覆
為其特徵者,其中紫外線遮蔽機能物質於該紫外線遮蔽材料中之含量為 16
至 83 重量%。2.如申請專利範圍第 1 項之紫外線遮蔽材料,其中該點土礦
物為頁狀矽酸鹄(phillosilicate)者。3.如申請專利範圍第 2 項之紫外線遮蔽
材料,其中該頁狀矽酸鹄為綠多水高嶺土(smectite)、蛭石(vermiculite)、以
及雲母(mica)者。4.如申請專利範圍第 1 至 3 項中任一項之紫外線遮蔽材
料,其中該紫外線遮蔽機能物質係送自氧化鈦、氧化鈦水合物、擔持有氧
化鈦及/或氧鈦水合物之無機物質中至少一種者。5.一種紫外線遮蔽材料之
製造方法,該方法包括下列步驟:
a)使黏土礦物分散於溶劑中之步驟、
b)使紫外線遮蔽機能物質分散於溶劑中之步驟、
c)將前述步驟 a)及 b)製得之 2 種分散液混合並包覆之步驟、
d)使前述混合物進行固液分離之步驟、
e)將前述步驟 d)製得之固形物加熱之步驟。6.如申請專利範圍第 5 項之紫
外線遮蔽材料製造方法,其中該步驟 e)之加熱係在 60℃以上 350℃以下之
溫度中加熱到在 110℃乾燥減量為 3 至 15wt%範圍者。7.如申請專利範圍
第 5 項之紫外線遮蔽材料之製造方法,其中該黏土礦物係頁狀矽酸鹄者。
8.如申請專利範圍第 7 項之紫外線遮蔽材料之製造方法,其中該頁狀矽酸
鹄係綠多水高嶺土、蛭石、及雲母者。9.如申請專利範圍第 5 至 8 項中任
一項之紫外線遮蔽材料之製造方法,其中該紫外線遮蔽機能物質係選自氧
化鈦、氧化鈦水合物、擔持有氧化鈦及/或氧化鈦水合物之無機物質中至
少一種者。圖式簡單說明:
第一圖分別表示實施例 1(a)及比較例 1(b)中製得粉體之 UV 反射光譜。
第二圖表示實施例 1 及比較例 2 中製得粉體之膨潤及分散前後的粒度分
布。
第三圖表示實施例 2 及比較例 3.4 中製得粉體之作為光催化劑機能之氧化
分解性能。
雜項資料
勘誤表(第 28 卷第 33 期)
原
2833.25.txt
始
資
料
更
更 正第 087116667 號 專利案 之 申請 專利 範圍 :
正
專
利
原
(原 刊於第 28 卷 第 25 期第 452605 號 公告 )
刊
來
源
正
申 請 專利 範圍 :
2.如申 請專 利範 圍第 1 項 之紫 外 線遮 蔽材 料 ,其中 該點 土礦 物 為
頁 狀 矽酸 鹄(phillosilicate)者。
4.如申 請專 利範 圍第 1 至 3 項 中 任一 項之 紫外 線遮 蔽材料 ,其中 該
紫 外 線遮 蔽機 能物 質係 送自氧 化 鈦、氧化 鈦水 合物、擔持 有 氧化
鈦 及 /或 氧鈦 水合 物之 無機 物質 中 至少 一種 者。
誤
申 請 專利 範圍 :
2.如申 請專 利範 圍第 1 項 之紫 外 線遮 蔽 材 料,其中 該黏 土礦 物 為
頁 狀 矽酸 鹄(phillosilicate)者。
4.如申 請專 利範 圍第 1 至 3 項 中 任一 項之 紫外 線遮 蔽材料 ,其中 該
紫 外 線遮 蔽機 能物 質係 選自氧 化 鈦、氧化 鈦水 合物、擔持 有 氧化
鈦 及 /或 氧鈦 水合 物之 無機 物質 中 至少 一種 者。
接下來改用『進階搜尋』來搜尋看看、輸入關鍵字『TiO2 and
photocatalyst』
總共找到 2 筆資料
第 1 筆 of 本國專利發明公開公報
專利類型
發明
公告/公開號 200507936
專利名稱
光觸媒塗佈液、光觸媒膜及光觸媒構件= PHOTOCATALYST COATING
SOLUTION, PHOTOCATALYST FILM AND PHOTOCATALYST
MEMBER
專利影像
公告/公開日 2005/03/01
期
公報卷期
0305
申請日期
0930429
申請案號
093112043
國際分類號 B01J-035/02 ; C09D-185/00
發明人/地址 田中尚樹 TANAKA, NAOKI 日本;
/國家
鈴木宏和 SUZUKI, HIROKAZU 日本;
小池匡 KOIKE, TADASHI 日本
申請人/地址 宇部日東化成股份有限公司 UBE-NITTO KASEI CO., LTD. 日本
/國家
專利代理人 林志剛
摘要
發明係關於超親水性、暗處的超親水維持性能等優異的光觸媒功能,且可
於有機基材上形成具良好耐久性的光觸媒膜,且安定性優異之光觸媒塗佈
液,以及使用其形成之光觸媒膜;提供包合(A)銳鈦礦型結晶構成之氧化鈦
微粒子;(B)膠體二氧化矽;以及(C)鈦烷氧化物;以加水分解.縮合物構成的
黏合劑,且基於固體成分全體的量,(A)成分含有量為 5-50 質量%(B)成分含
有量,其固體成分為 25-75 質量%,以及(C)成分含有量,以 TiO2 ,換算其固
體成分為 10-55 質量%之光觸媒塗佈液,以及使用該塗佈液形成的光觸媒
膜。
專利範圍
發明係關於超親水性、暗處的超親水維持性能等優異的光觸媒功能,且可
於有機基材上形成具良好耐久性的光觸媒膜,且安定性優異之光觸媒塗佈
液,以及使用其形成之光觸媒膜;提供包合(A)銳鈦礦型結晶構成之氧化鈦
微粒子;(B)膠體二氧化矽;以及(C)鈦烷氧化物;以加水分解.縮合物構成的
黏合劑,且基於固體成分全體的量,(A)成分含有量為 5-50 質量%(B)成分含
有量,其固體成分為 25-75 質量%,以及(C)成分含有量,以 TiO2 ,換算其固
體成分為 10-55 質量%之光觸媒塗佈液,以及使用該塗佈液形成的光觸媒
膜。
第 2 筆 of 本國專利公報 (民國 89-迄今)
專利類型
發明
公告/公開號 00586923
專利名稱
具有光催化作用塗層的人工水晶體
專利影像
公告/公開日 2004/05/11
期
公報卷期
3114
申請日期
2002/10/25
申請案號
091125130
國際分類號 A61F-002/14
發明人/地址 蔡明霖 臺北市文山區興隆路四段一四五巷六十四號三樓 中華民國;
/國家
鄭盛文 新竹市建中一路三十七號十七樓之五 中華民國;
郭宗南 新竹市光復路二段二九八巷九弄十七號四樓 中華民國;
彭素珍 臺北市中正區永春街一五四巷四弄三十九號 中華民國
申請人/地址 蔡明霖 臺北市文山區興隆路四段一四五巷六十四號三樓 中華民國;
/國家
鄭盛文 新竹市建中一路三十七號十七樓之五 中華民國;
郭宗南 新竹市光復路二段二九八巷九弄十七號四樓 中華民國;
彭素珍 臺北市中正區永春街一五四巷四弄三十九號 中華民國
專利代理人 惲軼群 臺北市松山區南京東路三段二四八號七樓;
陳文郎 臺北市松山區南京東路三段二四八號七樓
摘要
本發明揭示一種人工水晶體,其中該人工水晶體的光
學水晶體本體的至少一個表面的至少一部份被塗覆以一由
一光觸媒( photocatalyst )所構成的光催化作用塗層,藉此,
在一光束通經該光學水晶體本體時,該光催化作用塗層被
活化而釋出自由基氧化分解沾附於光學人工水晶體本體表
面的微生物與水晶體上皮細胞,降低白內障病人手術後併
發症[諸如眼內炎(endophthalmitis)與續發性白內障
(after-cataract)]的發生率。
專利範圍
1.一種人工水晶體,其包含:
一光學水晶體本體(optic lens body),其具有一前表面與一後表面;
一從該光學水晶體本體側向延伸而出的水晶體置放構件,用以將該光學水
晶體本體安置在一使用者的一個眼球內;以及
一光催化作用塗層,其係由一光觸媒所構成,且被塗覆在該光學水晶體本體
的前表面與後表面之至少一者的至少一部份上,藉此,在一光束通經該光學
水晶體本體時,該光催化作用塗層被活化而釋出會展現抗微生物效用之自
由基。2.如申請專利範圍第 1 項之人工水晶體,其中該光催化作用塗層被
塗覆在該光學水晶體本體之前表面上。3.如申請專利範圍第 2 項之人工水
晶體,其中該光催化作用塗層被塗覆在該光學水晶體本體之前表面的一個
會接觸一使用者的一眼的眼前房之區域上。4.如申請專利範圍第 1 項之人
工水晶體,其中該光催化作用塗層被塗覆在該光學水晶體本體之後表面
上。5.如申請專利範圍第 4 項之人工水晶體,其中該光催化作用塗層被塗
覆在該光學水晶體本體之後表面的一個會接觸一使用者的一眼的水晶體
囊袋之區域上。6.如申請專利範圍第 1 項之人工水晶體,其中該光催化作
用塗層被塗覆在該光學水晶體本體之前表面與後表面上。7.如申請專利範
圍第 1 項之人工水晶體,其中該光觸媒係擇自於下列群組:一種鈦氧化物、
ZnO、SnO2.WO3.CaTiO3.MoO3.NbO5.KNbO3.SrTiO3.CdSe、
Fe2O3.Ta2O5.Tix(Zrl-x)O2(其中 x=0 或 1)以及 CdS。8.如申請專利範圍
第 7 項之人工水晶體,其中該光觸媒係為一擇自於下列群組中的鈦氧化物:
一氧化鈦、二氧化鈦、三氧化二鈦以及五氧化三鈦。9.如申請專利範圍第
8 項之人工水晶體,其中該光觸媒係為二氧化鈦( TiO2 )。10.如申請專利範
圍第 1 項之人工水晶體,其中該光催化作用塗層具有一厚度係介於
2nm-200nm 之範圍內。11.如申請專利範圍第 1 項之人工水晶體,其中該
光學水晶體本體係由一擇自於下列群組中的物質所製成:聚甲基丙烯酸甲
酯、矽酮聚合物或丙烯酸聚合物。12.如申請專利範圍第 1 項之人工水晶
體,其中該水晶體置放構件與該光學水晶體本體是一體成型製造的。13.如
申請專利範圍第 1 項之人工水晶體,其中該水晶體置放構件與該光學水晶
體本體是分開製造的。14.如申請專利範圍第 1 項之人工水晶體,其中該水
晶體置放構件包括兩個腳架,該等腳架各有一端部被側向地連接於該光學
水晶體本體上。15.如申請專利範圍第 14 項之人工水晶體,其中該腳架係
以一擇自於下列群組的物質所製成:聚甲基丙烯酸甲酯、聚丙烯或聚偏氟
乙烯。16.一種用以製造一人工水晶體之方法,其包含下列步驟:
(a)提供一人工水晶體,該人工水晶體包含有:一具有一前表面與一後表面
之光學水晶體本體;以及一從該光學水晶體本體側向延伸而出的水晶體置
放構件,用以將該光學水晶體本體安置在一使用者的一個眼球內;以及
(b)將一光觸媒塗覆於該光學水晶體本體的至少一個表面的至少一部份上
而形成一光催化作用塗層。17.如申請專利範圍第 16 項之方法,其中步驟
(b)是藉由至少一種選自於下列之方式來進行:蒸鍍法、濺鍍法、化學氣相
沉積法、電漿化學氣相沉積法以及物理氣相沉積法。18.如申請專利範圍
第 16 項之方法,其中在步驟(b)中,該光催化作用塗層被形成在該光學水晶
體本體之前表面上。19.如申請專利範圍第 18 項之方法,其中在步驟(b)後,
該光催化作用塗層被形成在該光學水晶體本體之前表面的一個會接觸一
使用者的一眼的眼前房之區域上。20.如申請專利範圍第 16 項之方法,其
中在步驟(b)後,該光催化作用塗層被形成在該光學水晶體本體之後表面
上。21.如申請專利範圍第 20 項之方法,其中在步驟(b)後,該光催化作用塗
層被形成在該光學水晶體本體之後表面的一個會接觸一使用者的一眼的
水晶體囊袋之區域上。22.如申請專利範圍第 16 項之方法,其中在步驟(b)
後,該光催化作用塗層被形成在該光學水晶體本體之前表面與後表面上。
23.如申請專利範圍第 16 項之方法,其中步驟(b)所用的光觸媒係擇自於下
列群組:一種鈦氧化物、ZnO、
SnO2.WO3.CaTiO3.MoO3.NbO5.KNbO3.SrTiO3.CdSe、
Fe2O3.Ta2O5.Tix(Zrl-x)O2(其中 x=0 或 1)以及 CdS。24.如申請專利範
圍第 23 項之方法,其中步驟(b)所用的光觸媒係為一擇自於下列群組中之
鈦氧化物:一氧化鈦、二氧化鈦、三氧化二鈦或五氧化三鈦。25.如申請專
利範圍第 24 項之方法,其中步驟(b)所用的光觸媒係為二氧化鈦( TiO2 )。
26.如申請專利範圍第 16 項之方法,其中在步驟(b)之後,一具有一厚度範圍
在 2nm-200nm 之間的光催化作用塗層被形成。27.如申請專利範圍第 16
項之方法,其中該水晶體本體係以一擇自於下列群組中的物質所製成:聚甲
基丙烯酸甲酯、矽酮聚合物或丙烯酸聚合物。28.如申請專利範圍第 16 項
之方法,其中在步驟(a)提供的人工水晶體中,該水晶體置放構件與該光學
水晶體本體是一體成型製造的。29.如申請專利範圍第 16 項之方法,其中
在步驟(a)提供的人工水晶體中,該水晶體置放構件與該光學水晶體本體是
分開製造的。30.如申請專利範圍第 16 項之方法,其中在步驟(a)提供的人
工水晶體中,該水晶體置放構件包括兩個腳架,該等腳架各有一端部被側向
地連接於該光學水晶體本體上。31.如申請專利範圍第 30 項之方法,其中
該腳架係以一擇自於下列群組的物質所製成:聚甲基丙烯酸甲酯、聚丙烯
或聚偏氟乙烯。圖式簡單說明:
第 1 圖是一示意平面圖,其中顯示一個適用於本發明的人工水晶體的結構;
第 2 圖為第 1 圖中所示的人工水晶體的一個示意剖面圖;
第 3 圖是一示意透視圖,其中顯示另一種適用於本發明的可摺疊式平板狀
(plate-type)人工水晶體的結構;
第 4 圖為一剖視圖,其顯示在一光學水晶體本體之前表面與後表面上各形
成有一光催化作用塗層;
第 5 圖為沿第 4 圖所示虛線所取區域之一部分放大的剖視圖,其顯示有一
光催化作用塗層被形成在一光學水晶體本體的前表面上;
第 6A 圖為一示意平面圖,其顯示一於前表面上形成有一光催化作用塗層
的人工水晶體被置於一眼球內,並有一光束通經該人工水晶體的光學水晶
體本體前表面之情形;
第 6B 圖為一示意平面圖,其顯示一於後表面上形成有一光催化作用塗層
的人工水晶體被置於一眼球內,並有一光束通經該人工水晶體的光學水晶
體本體後表面之情形;
第 7A 圖為一示意透視圖,其顯示將帶有由 TiO2 所構成的光催化作用塗
層的光學水晶體本體測試樣品置放於一試驗盤的井孔內,以進行細菌或細
胞生長抑制試驗;
第 7B 圖為一試驗盤井孔之放大剖面圖,其顯示一光學水晶體本體測試樣
品被放在一試驗盤的一個井孔內,且被覆蓋以一細胞懸浮液,再以 UV 光予
以照射處理之示意圖;
第 8 圖為一柱狀圖,其顯示帶有與未帶有由 TiO2 所構成的光催化作用塗
層的人工水晶體對於大腸桿菌的分解效果,其中以 MDA 數值作為測定指
標;
第 9 圖為一柱狀圖,其顯示帶有與未帶有由 TiO2 所構成的光催化作用塗
層的人工水晶體對於大腸桿菌存活率的影響;
第 10 圖為一柱狀圖,其顯示帶有與未帶有由 TiO2 所構成的光催化作用
塗層的人工水晶體對於人類水晶體上皮細胞生長之分解效果,其中以 MDA
數值作為測定指標;以及
第 11 圖為一柱狀圖,其顯示帶有與未帶有由 TiO2 所構成的光催化作用
塗層的人工水晶體對於人類水晶體上皮細胞菌存活率之影響。
二、美國專利
先進入美國專利商標局網站(http://www.uspto.gov/)、進入之後點選
『Search』、之後再選擇『Quick Search』
、進入頁面如下 :
輸入關鍵字『TiO2 and photocatalyst』結果共找到 74 筆資料、由於太
多筆數、所以改用其他的關鍵字搜尋。
再輸入關鍵字『TiO2 thin film』、
『photocatalyst』
總共找到 4 筆資料
點選第一筆專利號碼、詳細內容如下 :
(1
United States Patent
Boire ,
of
4)
6,846,556
et al.
January 25, 2005
Substrate with a photocatalytic coating
Abstract
The subject of the invention is a glass-, ceramic- or vitroceramic-based substrate (1)
provided on at least part of at least one of its faces with a coating (3) with a photocatalytic
property containing at least partially crystalline titanium oxide. It also relates to the
applications of such a substrate and to its method of preparation.
Inventors: Boire; Philippe (Paris, FR); Talpaert; Xavier (Paris, FR)
Assignee: Saint-Gobain Glass France (Paris, FR)
Appl. No.: 116164
Filed:
April 5, 2002
428/325; 359/580; 359/582; 359/585; 359/586;
427/164; 427/165; 427/167; 428/432; 428/701;
428/702
Current U.S. Class:
B32B 017/06; C23C016/00
Intern'l Class:
428/325,428,432,701,702 427/164,165,167,255
Field of Search:
359/580,582,585,586
References Cited [Referenced By]
U.S. Patent Documents
3630796
Dec., 1971
Yokozawa et al.
4017661
Apr., 1977
Gillery.
4112142
Sep., 1978
Schroder et al.
4238276
Dec., 1980
Kinugawa et al.
4485146
Nov., 1984
Mizuhashi et al.
4544470
Oct., 1985
Hetrick.
4888038
Dec., 1989
Herrington et al.
4892712
Jan., 1990
Robertson et al.
5028568
Jul., 1991
Anderson et al.
5032241
Jul., 1991
Robertson et al.
5035784
Jul., 1991
Anderson et al.
5304394
Apr., 1994
Sauvinet et al.
5308805
May., 1994
Baker et al.
5342676
Aug., 1994
Zagdoun.
5348805
Sep., 1994
Zagdoun et al.
5368892
Nov., 1994
Berquier.
5389427
Feb., 1995
Berquier.
5478783
Dec., 1995
Higby et al.
5505989
Apr., 1996
Jenkinson.
5514454
May., 1996
Boire et al.
5525406
Jun., 1996
Goodman et al.
5547823
Aug., 1996
Murasawa et al.
5580364
Dec., 1996
Goodman et al.
5616532
Apr., 1997
Heller et al.
5618579
Apr., 1997
Boire et al.
5698262
Dec., 1997
Soubeyrand et al.
5735922
Apr., 1998
Woodward et al.
5745291
Apr., 1998
Jenkinson.
5749931
May., 1998
Goodman et al.
5751484
May., 1998
Goodman et al.
5755845
May., 1998
Woodward et al.
5764415
Jun., 1998
Nelson et al.
5773086
Jun., 1998
McCurdy et al.
5853866
Dec., 1998
Watanabe et al.
5854169
Dec., 1998
Heller et al.
5869187
Feb., 1999
Nakamura et al.
5939201
Aug., 1999
Boire et al.
5961843
Oct., 1999
Hayakawa et al.
6001462
Dec., 1999
Purvis et al.
6013372
Jan., 2000
Hayakawa et al.
6027766
Feb., 2000
Greenberg et al.
6027797
Feb., 2000
Watanabe et al.
6037289
Mar., 2000
Chopin et al.
6045896
Apr., 2000
Boire et al.
6054227
Apr., 2000
Greenberg et al.
6068914
May., 2000
Boire et al.
6090489
Jul., 2000
Hayakawa et al.
6103360
Aug., 2000
Caldwell et al.
6103363
Aug., 2000
Boire et al.
6106955
Aug., 2000
Ogawa et al.
6210779
Apr., 2001
Watanabe et al.
6228480
May., 2001
Kimura et al.
6238738
May., 2001
McCurdy.
6322881
Nov., 2001
Boire et al.
6326079
Dec., 2001
Philippe et al.
6387844
May., 2002
Fujishima et al.
Foreign Patent Documents
0 544 577
Jun., 1993
EP.
0 581 216
Feb., 1994
EP.
2 320 499
Jun., 1998
GB.
2 320503
Jun., 1998
GB.
2 324098
Oct., 1998
GB.
2 355 273
Apr., 2001
GB.
5-3149281
Dec., 1978
JP.
63-100042
May., 1988
JP.
5-302173
Nov., 1993
JP.
7-99425
Mar., 1995
JP.
7-117600
Apr., 1995
JP.
7-182019
Jun., 1995
JP.
7-182020
Jun., 1995
JP.
7-205019
Jul., 1995
JP.
8-119673
May., 1996
JP.
8-164334
Jun., 1996
JP.
8-313705
Nov., 1996
JP.
9-173783
Jul., 1997
JP.
9-227157
Sep., 1997
JP.
9-227158
Sep., 1997
JP.
9-235140
Sep., 1997
JP.
9-241037
Feb., 1999
JP.
WO 96/13327
May., 1996
WO.
WO 96/29375
Sep., 1996
WO.
WO 97/07069
Feb., 1997
WO.
WO 97/10186
Mar., 1997
WO.
WO 98/06510
Feb., 1998
WO.
WO 98/08675
Feb., 1998
WO.
WO 00/75087
Dec., 2000
WO.
428/325.
WO 01/10790
Feb., 2001
WO.
WO 01/72652
Oct., 2001
WO.
Other References
Masanari Takahashi et al., "Pt-TIO.sub.2 Thin Films on Glass Substrates as
Efficient Photocatalysts," Journal of Materials Science, 24 (1988) pp.
243-246.
S. Fukayama et al., Highly Transparent and Photoactive TIO.sub.2 Thin Film
Coated on Glass Substrate, Abstract No. 735, pp. 1102-1103, 187.sup.th
Electrochemical Society Meeting, Reno, NV, May 21-26, 1995, and attached
fascimile transmission from The British Library indicating that the date of
availability for public use was Mar. 29, 1995.
D.R. Uhlmann, "Glass: Science and Technology," vol. 2, Processing I, pp.
253-283, 1984.
GlassFAQs, GlassFACTS.com, pg. 1-5.
JP 88-158890, Abstract Only, Derwent JP 860243762, Glass Article Difficult
Soil Coating Thin Titanium Di Oxide Coating Contain Platinum@ Rhodium
Palladium@.
Chemical Abstracts,, 116: 89612a, Sokolov, et al., "Selective Activation of
Smooth Surfaces of Glass and Ceramic Articles Before Chemical
Metalization," Abstract Only.
International Search Report for PCT/FR96/01421.
International Preliminary Examination Report for PCT/FR96/01421.
H.H. Dunken, Glass Surfaces, Treatise on Materials Science and Technology,
vol. 22, pp. 1-75, 1982.
Toshiya Watanabe et al., Photocatalytic Activity of TIO2 Thin Film under
Room Light, in Photocatalytic Purification and Treatment of Water and Air,
pp. 747-751, 1993, Ollis et al., Eds.
The Japan Times, May 21, 2002, Tuesday, Race for Technology, pp. 2-5,
from LexisNexis.
P. Chartier, Verre, Glass Institute, vol. 3, No. 3-Jun. 1997, pp. 5-12, French
document with English Translation.
Pt-TiO.sub.2 Thin Films on Glass Substrates as Efficient Photocatalysts,
Journal of Materials Science, 24 (1989), pp. 243-246, Document DI cited in
the Opposition under Tab A.
EP A 581-216, Okada et al., Feb. 2, 1994, Document D2 cited in the
Opposition under Tab A; Document D17 cited in the Opposition under Tab C.
Preparation of TiO.sub.2 Fine Particles Supported on Silica Gel as
Photocatalyst, Yasumori et al., Journal of the Ceramic Society of Japan, 102
(1994), Document D5 cited in the Opposition under Tab A.
Photocatalytic Properties of TiO.sub.2, Wold, Chem. Mater., 1993, 5, pp.
280-283, Document D6 cited in the Opposition under Tab A.
Kristallstruktur und Optische Eigenshaften von Dunnen Organogenen
Titanoxyd-Schichten Auf Glasunterlagen [Crystal Structure and Optical
Properties of Thin Organogenic Titanium Oxide Layers on Glass Substrates],
Bach et al., Thin Solid Films I (1967/68), pp. 255-276, and English
tranlation, Document D7 cited in the Opposition under Tab A.
US 5,165,972, Porter, Nov. 24, 1992, Document D8 cited in the Opposition
under Tab A.
US 4,485,146, Mizuhashi et al., Nov. 27, 1984, Document D9 cited in the
Opposition under Tab A.
EP 816 466, Hayakawa et al., Jan. 7, 1998, Document D11 cited in the
Opposition under Tab A; Document D4 cited in the Opposition under Tab C;
Document D2 cited in the Opposition under Tab D.
The Effect of Substrate Temperature on the Properties of Sputtered Titanium
Oxide Films, Meng et al., Applied Surface Science 65/66 (1993) pp. 235-239,
Document D12 cited in the Opposition under Tab A.
Sol-Gel-Derived TiO.sub.2 Film Semiconductor Electrode for Photocleavage
of Water, Yoko et al., J. Electrochem Soc., vol. 138(8), Aug. 1991, pp.
2279-2284, Document D13 cited in the Opposition under Tab A.
Dip-Coating of TiO.sub.2 Films Using a Sol Derived From Ti(O-iPr).sub.4
-diethamolamine-H.sub.2 O-i-PrOH System, Takahashi et al., Journal of
Materials Science 23 (1988), pp. 2259-2266, Document D14 cited in the
Opposition under Tab A.
A Structural Investigation of Titanium Dioxide Photocatalysts, Bickley, et al.,
Journal of Solid State Chemistry 92, 1991, pp. 178-190, Document D15 cited
in the Opposition under Tab A.
Highly Transparent and Photoactive TiO2 Thin Film Coated on Glass
Substrate, Fukayama et al., Abstract 735, 187.sup.th Electrochemical Society
Meeting, Mar. 29, 1995, Document D4 cited in the Opposition under Tab A;
Document D1 cited in the Opposition under Tab B; Document D5a cited in
the Opposition under Tab C.
EP 684,075, Wantanabe et al., Jun. 15, 1995 and the front page of WO
95/15816, Watanabe et al., Jun. 15, 1995, which is an equivalent of EP
684,075 and contains an English abstract, Document D10 cited in the
Opposition under Tab A; Document D2 cited in the Opposition under Tab B;
Document D4 cited in the Opposition under Tab D.
EP 650 938 A1, Boire et al., May 3, 1995, Document D3 cited in the
Opposition under Tab B.
Oxide Layers Deposited from Organic Solutions, H. Schroeder in Physics of
Thin Films: Advances in Research and Development, pp. 105-112, vol. 5,
1969 Academic Press, Document D4 cited in the Opposition under Tab B;
Document D5 cited in the Opposition under Tab D.
EP 737 531A1, Fujishima et al., Oct. 16, 1996, Document D3 cited in the
Opposition under Tab A; Document D5 cited in the Opposition under Tab B;
Document D16 cited in the Opposition under Tab C.
JP 267476/94, Fujishima et al., publication date not listed, and Derwent
WPIndex abstract; corresponds to EP 737 513A, (submitted herewith under
Tab 17); WO 96/13327 (of record; published on May 9, 1996); and U.S.
6,387,844 (of record), Document D5a cited in the Opposition under Tab B;
Document D3 cited in the Opposition under Tab D.
WO 97/07069, Heller, Feb. 27, 1997, Document D6 cited in the Opposition
under Tab B; Opposition under Tab B; Document D1 cited in the Opposition
under Tab D.
JP 63-100042, Kume et al., May 2, 1988, Document D7 cited in the
Opposition under Tab B; Document D8 cited in the Opposition under Tab C.
EP 0 071 865A2, Mizuhashi et al., Feb. 16, 1983, Document D8 cited in the
Opposition under Tab B.
GB 2,031,756A, Gordon, Apr. 30, 1980, Document D9 cited in the
Opposition under Tab B.
EP 0 348 185 B, Jenkins et al., Dec. 27, 1989, Document D10 cited in the
Opposition under Tab B.
JPA 63-5301 Matsushita Electric Works (assignee), Jan. 11, 1988, and
Derwent WPIndex abstract, Document D2 cited in the Opposition under Tab
C.
JPA 63-5304, Matsushita Electric Works (assignee), Jan. 11, 1988, and
Derwent WPIndex abstract, Document D7 cited in the Opposition under Tab
C.
JP 91042/1986, Yokoishi, May 9, 1986, Document D9 cited in the Opposition
under Tab C.
JPA 7-222928, Chikuni et al., Aug. 22, 1995, and Derwent WPIndex abstrac;
equivalent of WO 95/15816 (submitted herewith)) and U.S. 5,853,866 (of
record), 6,210,779 (submitted hereiwth), 6,294,246 (submitted herewith), and
6,294,247 (submitted herewith), Document D11 cited in the Opposition
under Tab C.
JPA 1-218635, Hitachi LTD (assignee), Feb. 29, 1988, and Derwent WPIndex
abstract, Document D12 cited in the Opposition under Tab C.
JPA 7-111104, Fujishima et al., Apr. 25, 1995, and Derwent WPIndex
abstract, Document D14 cited in the Opposition under Tab C.
Preparation of Transparent TiO.sub.2 Thin Film Photocatalyst and Its
Photocatalytic Activity, Negishi et al., Chemistry Letters 1995, No. 9, pp.
841-842, Document D3a cited in the Oppositon under Tab D.
EP 633 064, Murasawa et al., Jan. 11, 1995, Document D3 cited in the
Opposition under Tab C.
EP 590 477, Ogawa et al., Apr. 6, 1994, Document D10 cited in the
Opposition under Tab C; Document D6 cited in the Opposition under Tab D.
EP 675 086, Okada et al., Oct. 4, 1995, Document D7 cited in the Opposition
under Tab D.
JP-A-5 253 544, Toto LTD (assignee), Oct. 5, 1995, and Derwent WPIndex
abstract, Document D1 cited in the Oppositon under Tab C; Document D8
cited in the Opposition under Tab D.
JP-A-6-65012, Agency of Ind. Sci. & Technology (assignee), Mar. 8, 1994,
and Derwent WPIndex abstract, Document D6 cited in the Opposition under
Tab C; Document D9 cited in the Opposition under Tab D.
US 4,898,789, Finley, Feb. 6, 1990, Document D10 cited in the Opposition
under Tab D.
EP 636 702, Shimizu et al., Feb. 2, 1995, Document D11 cited in the
Opposition under Tab D.
US 5,348,805, Zagdoun et al., Sep. 20, 1994, Document D12 cited in the
Opposition under Tab D.
Electrical and Electrochemical Properties of TiO.sub.2 films Grown by
Organometallic Chemical Vapour Deposition, Takahashi et al., J. Chem. Soc.,
Farady Trans 1, 1982, 78, pp. 2563-2571, Document D13, cited in the
Opposition under Tab D.
US 4,997,576, Heller et al., Mar. 5, 1991, Document D14 cited in the
Opposition under Tab D.
US 5,342,676, Zagdoun, Aug. 30, 1994, Document D15 cited in the
Opposition under Tab D.
EP 489 621, Zagdoun et al., Jun. 6, 1992, Document D13 cited in the
Opposition under Tab C.
Apr. 30, 2000 Letter from Mrs. Colette Ward, Patent Litigation Enquiries,
British Library, Document CW1 cited in the Opposition under Tab B.
WO 95/15816, Watanabe et al., Jun. 15, 1995, Equivalent to JPA 7-222928
submitted herewith under Tab 27.
US 6,210,779, Watanabe et al., Apr. 3, 2001, Equivalent to JPA 7-222928
submitted herewith under Tab 27.
US 6,294,246, Wantanabe et al., Sep. 25, 2001, Equivalent to JPA 7-222928
submitted herewith under Tab 27.
US 6,294,247, Wantanabe et al., Sep. 25, 2001, Equivalent to JPA 7-222928
submitted herewith under Tab 27.
Primary Examiner: McNeil; Jennifer
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt, P.C.
Parent Case Text
This application is a Continuation of application Ser. No. 09/923,353, filed on Aug. 08,
2001, pending, which is a continuation of application Ser. No. 09/615,910, filed Jul.
13, 2000, now U.S. Pat. No. 6,326,079, which is a continuation of application Ser. No.
09/029,855, filed on May 28, 1998, now U.S. Pat. No. 6,103,363, which was
originally filed as PCT/FR96/01421 on Sep. 13, 1996.
Claims
What is claimed is:
1. A coated substrate which is a glass, ceramic or vitro-ceramic substrate provided on
at least a portion of one of its faces with a coating having photocatalytic properties,
and comprising titanium oxide at least partially crystallized in the anatase form, and
wherein the coating has a refractive index of from about 2.30 to about 2.35.
2. The coated substrate of claim 1, which is a glass substrate.
3. The coated substrate of claim 1, which is a ceramic substrate.
4. The coated substrate of claim 1, which is a vitro-ceramic substrate.
5. The coated substrate of claim 1, wherein the titanium oxide is in the form of
crystallites having an average size of between 0.5 and 100 nm.
6. The coated substrate of claim 1, wherein the titanium oxide is in the form of
crystallites having an average size of between 1 and 50 nm.
7. The coated substrate of claim 1, wherein the titanium oxide is in the form of
crystallites having an average size of between 10 and 40 nm.
8. The coated substrate of claim 1, wherein the titanium oxide is in the form of
crystallites having an average size of between 20 and 30 nm.
9. The coated substrate of claim 1, wherein coating is deposited by chemical vapor
deposition followed by annealing.
10. The coated substrate of claim 1, wherein the coating has a thickness between 5 nm
and 1 micron.
11. The coated substrate of claim 1, wherein the coating has a thickness between 5 nm
and 100 nm.
12. The coated substrate of claim 1, wherein the coating has a thickness between 10
and 80 nm.
13. The coated substrate of claim 1, wherein the coating has a thickness between 20
and 50 nm.
14. A process for a producing a coated substrate as claimed in claim 1, comprising:
chemical vapor depositing at least one titanium precursor on at least part of at least
one face of a glass-, ceramic-, or vitroceramic-based substrate, to produce a
photocatalytic coating containing at least partially crystalline titanium oxide,
wherein
the crystalline titanium oxide is in the form of crystallites with an average size of
between 0.5 and 100 nm, and the thickness of the coating is between 5 nm and 1
micron.
15. The process of claim 14, wherein the substrate is glass.
16. The process of claim 14, wherein the substrate is a float-glass.
17. The process of claim 14, wherein the coating containing the at least partially
crystalline titanium oxide has a degree of porosity of 65 to 99%.
18. The process of claim 14, wherein the coating containing the at least partially
crystalline titanium oxide has a degree of porosity of 70 to 99%.
19. The process of claim 14, wherein the coating containing the at least partially
crystalline titanium oxide has a degree of porosity of 70 to 90%.
20. The process of claim 14, wherein the crystalline titanium oxide is in the form of
crystallites with an average size of between 0.5 and 60 nm.
21. The process of claim 14, wherein the crystalline titanium oxide is in the form of
crystallites with an average size of between 1 and 50 nm.
22. The process of claim 14, wherein the crystalline titanium oxide is in the form of
crystallites with an average size of between 10 and 40 nm.
23. The process of claim 14, wherein the crystalline titanium oxide is in the form of
crystallites with an average size of between 20 and 30 nm.
24. The process of claim 14, wherein the thickness of the coating containing the at
least partially crystalline titanium oxide is between 5 nm and 100 nm.
25. The process of claim 14, wherein the thickness of the coating containing the at
least partially crystalline titanium oxide is 10 nm to 80 nm.
26. The process of claim 14, wherein the thickness of the coating containing the at
least partially crystalline titanium oxide is between 5 nm and 20 nm.
27. The process of claim 14, wherein the crystalline titanium oxide is in the form of
crystallites and the thickness of the coating containing the at least partially crystalline
titanium oxide is at least two times greater than the mean diameter of the crystallites.
28. The process of claim 14, wherein the crystalline titanium oxide is in the anatase
form, in the rutile form, or in the form of a mixture of anatase and rutile.
29. The process of claim 14, wherein the titanium oxide is crystalline with a degree of
crystallization of at least 25%.
30. The process of claim 14, wherein the titanium oxide is crystalline with a degree of
crystallization of between 30 and 80%.
31. The process of claim 14, wherein the surface of the coating containing the at least
partially crystalline titanium oxide has a contact angle with water of less than 5 after
exposure to light radiation.
32. The process of claim 14, wherein the surface of the coating containing the at least
partially crystalline titanium oxide has a contact angle with water of less than 1 after
exposure to light radiation.
33. The process of claim 14, wherein the RMS roughness of the coating containing
the at least partially crystalline titanium oxide is between 2 and 20 nm.
34. The process of claim 14, wherein the RMS roughness of the coating containing
the at least partially crystalline titanium oxide is between 5 and 20 nm.
35. The process of claim 14, wherein the chemical vapor deposition is conducted at a
temperature of 400 to 600.degree. C.
36. The process of claim 14, wherein the chemical vapor deposition is conducted at a
temperature of 400 to 600.degree. C.
37. The process of claim 14, wherein the titanium precursor is a titanium halide.
38. The process of claim 14, wherein the titanium precursor is an organometallic
titanium compound.
39. The process of claim 14, wherein the titanium precursor is a titanium alcoholate.
40. The process of claim 14, wherein the titanium precursor is TiCl4.
41. The process of claim 14, wherein the titanium precursor is selected from the group
consisting of Ti(OiPr)4, titanium diisopropoxide diacetylacetonate, titanium
tetraoctyleneglycolate, and titanium acetylacetonate.
42. The process of claim 14, wherein the coating containing the at least partially
crystalline titanium oxide also contains at least one additive capable of accentuating
the photocatalytic activity of the titanium oxide.
43. The process of claim 14, further comprising incorporating metal particles or
particles based on such a metal into the coating, wherein the metal is selected from the
group consisting of cadmium, tin, tungsten, zinc, cerium, and zirconium.
44. The process of claim 14, further comprising inserting into the crystal lattice of the
titanium oxide at least one the metal is selected from the group consisting of niobium,
tantalum, iron, bismuth, cobalt, nickel, copper, ruthenium, cerium, and molybdenum.
45. The process of claim 14, further comprising covering at least part of the coating
containing the at least partially crystalline titanium oxide with a layer of metal oxides
or salts, wherein the metal is selected from the group consisting of iron, copper,
ruthenium, cerium, molybdenum, vanadium, and bismuth.
46. The process of claim 14, wherein the coating containing the at least partially
crystalline titanium oxide also contains an amorphous or partially crystalline oxide or
mixture of oxides of the silicon oxide, tin oxide, zirconium oxide, or aluminum oxide
type.
47. The process of claim 14, further comprising coating at least a portion of the
coating containing the at least partially crystalline titanium oxide with a noble metal.
48. The process of claim 47, wherein the noble metal is selected from the group
consisting of platinum, rhodium, silver, and palladium.
49. The process of claim 14, wherein
the substrate is coated with at least one thin layer, wherein the thin layer has an
anti-static function, a thermal function or an optical function, or forms a barrier to the
migration of alkali metals; and
the coating containing the at least partially crystalline titanium oxide is coated on the
thin layer.
50. The process of claim 49, wherein the thin layer has an anti-static function.
51. The process of claim 50, wherein the thin layer is based on a conductive material
of the metal type or of the doped metal oxide type.
52. The process of claim 51, wherein the thin layer is based on ITO, SnO2:F, ZnO:F,
ZnO:Al, ZnO:Sn or a metal oxide which is stoichiometrically deficient in oxygen.
53. The process of claim 52, wherein the metal oxide which is stoichiometrically
deficient in oxygen is SnO2-x or ZnO2-x, wherein x<2.
54. The process of claim 49, wherein the thin layer has a thermal function.
55. The process of claim 54, wherein the thin layer is based on a conductive material
of the metal type or of the doped metal oxide type.
56. The process of claim 55, wherein the thin layer is based on ITO, SnO2:F, ZnO:F,
ZnO:Al, ZnO:Sn or a metal oxide which is stoichiometrically deficient in oxygen.
57. The process of claim 56, wherein the metal oxide which is stoichiometrically
deficient in oxygen is SnO2-x or ZnO2-x, wherein x<2.
58. The process of claim 49, wherein the thin layer has an optical function.
59. The process of claim 58, wherein the thin layer is based on a conductive material
of the metal type or of the doped metal oxide type.
60. The process of claim 59, wherein the thin layer is based on ITO, SnO2:F, ZnO:F,
ZnO:Al, ZnO:Sn or a metal oxide which is stoichiometrically deficient in oxygen.
61. The process of claim 60, wherein the metal oxide which is stoichiometrically
deficient in oxygen is SnO2-x or ZnO2-x, wherein x<2.
62. The process of claim 58, wherein the thin layer is based on an oxide or on a
mixture of oxides with a refractive index which is intermediate between that of the
coating containing the at least partially crystalline titanium oxide and that of the
substrate.
63. The process of claim 62, wherein the thin layer is composed of A1203, SnO2,
1n203, silicon oxycarbide, or silicon oxynitride.
64. The process of claim 49, wherein the thin layer forms a barrier to the migration of
alkali metals.
65. The process of claim 64, wherein the thin layer is based on silicon oxide, silicon
nitride, silicon oxynitride, silicon oxycarbide, A1203:F, or aluminum nitride.
66. The process of claim 14, wherein the coating containing the at least partially
crystalline titanium oxide is the final layer of a stack of anti-glare layers.
67. The process of claim 14, wherein the coating containing the at least partially
crystalline titanium oxide is deposited in at least two successive stages.
68. The process of claim 14, wherein the coating containing the at least partially
crystalline titanium oxide is subjected, after deposition, to at least one heat treatment
of the annealing type.
Description
The invention relates to glass-, ceramic- or vitroceramic-based substrates, more
particularly made of glass, in particular transparent substrates, which are furnished
with coatings with photocatalytic properties, for the purpose of manufacturing glazing
for various applications, such as utilitarian glazing or glazing for vehicles or for
buildings.
There is an increasing search to functionalize glazing by depositing at the surface
thereof thin layers intended to confer thereon a specific property according to the
targeted application. Thus, there exist layers with an optical function, such as
so-called anti-glare layers composed of a stack of layers alternatively with high or low
refractive indices. For an anti-static function or a heating function of the anti-icer type,
it is also possible to provide eleclxically conducting thin layers, for example based on
metal or doped metal oxide. For an anti-solar or low-emissivity thermal function for
example, thin layers made of metal of the silver type or based on metal oxide or
nitride may be used. To obtain a "rain-repellent" effect, it is possible to provide layers
with a hydrophobic nature, for example based on fluorinated organosilane and the like.
However, there still exists a need for a substrate, particularly a glazing, which could
be described as "dirt-repellent", that is to say targeted at the permanence over time of
the appearance and surface properties, and which makes it possible in particular to
render cleaning less frequent and/or to improve the visibility, by succeeding in
removing, as they are formed, the dirty marks which are gradually deposited at the
surface of a substrate, in particular dirty marks of organic origin, such as finger marks
or volatile organic products present in the atmosphere, or even dirty marks of
condensation type.
In point of fact, it is known that there exist certain semiconductive materials based on
metal oxides which are capable, under the effect of radiation of appropriate
wavelength, of initiating radical reactions which cause the oxidation of organic
products; they are generally referred to as "photocatalytic" or alternatively
"photoreactive" materials.
The aim of the invention is then to develop photocatalytic coatings on a substrate
which exhibit a marked "dirt-repellent" effect with respect to the substrate and which
can be manufactured industrially.
The object of the invention is a glass-, ceramic- or vitroceramic-based substrate, in
particular made of glass and transparent, provided on at least part of at least one of its
faces with a coating with a photocatalytic property containing at least partially
crystalline titanium oxide. The titanium oxide is preferably crystallized "in situ"
during the formation of the coating on the substrate.
Titanium oxide is in fact one of the semi-conductors which, under the effect of light in
the visible or ultraviolet range, degrade organic products which are deposited at their
surface. The choice of titanium oxide to manufacture a glazing with a "dirt-repellent"
effect is thus particularly indicated, all the more so since this oxide exhibits good
mechanical strength and good chemical resistance: for long-term effectiveness, it is
obviously important for the coating to retain its integrity, even if it is directly exposed
to numerous attacks, in particular during the fitting of the glazing on a building site
(building) or on a production line (vehicle) which involves repeated handlings by
mechanical or pneumatic prehension means, and also once the glazing is in place,
with risks of abrasion (windscreen wipers, abrasive rag) and of contact with
aggressive chemicals (atmospheric pollutants of SO.sub.2 type, cleaning product, and
the like).
The choice has fallen, in addition, on a titanium oxide which is at least partially
crystalline because it has been shown that it had a much better performance in terms
of photocatalytic property than amorphous titanium oxide. It is preferably crystallized
in the anatase form, in the rutile form or in the form of a mixture of anatase and rutile,
with a degree of crystallization of at least 25%, in particular of approximately 30 to
80%, in particular close to the surface (the property being rather a surface property).
(Degree of crystallization is understood to mean the amount by weight of crystalline
TiO.sub.2 with respect to the total amount by weight of TiO.sub.2 in the coating).
It has also been possible to observe, in particular in the case of crystallization in
anatase form, that the orientation of the TiO.sub.2 crystals growing on the substrate
had an effect on the photocatalytic behaviour of the oxide: there exists a favoured
orientation (1, 1, 0) which markedly promotes photocatalysis.
The coating is advantageously manufactured so that the crystalline titanium oxide
which it contains is in the form of "crystallites", at least close to the surface, that is to
say of monocrystals, having an average size of between 0.5 and 100 nm, preferably 1
to 50 nm, in particular 10 to 40 nm, more particularly between 20 and 30 nm. It is in
fact in this size range that titanium oxide appears to have an optimum photo-catalytic
effect, probably because the crystallites of this size develop a high active surface area.
As will be seen in more detail subsequently, it is possible to obtain the coating based
on titanium oxide in many of ways:
by decomposition of titanium precursors (pyrolysis techniques: liquid pyrolysis,
powder pyrolysis, pyrolysis in the vapour phase, known as CVD (Chemical Vapour
Deposition), or techniques associated with the sol-gel: dipping, cell coating, and the
like),
by a vacuum technique (reactive or non-reactive cathodic sputtering).
The coating can also contain, in addition to the crystalline titanium oxide, at least one
other type of inorganic material, in particular in the form of an amorphous or partially
crystalline oxide, for example a silicon oxide (or mixture of oxides), titanium oxide,
tin oxide, zirconium oxide or aluminium oxide. This inorganic material can also
participate in the photo-catalytic effect of the crystalline titanium oxide, by itself
exhibiting to a certain extent a photocatalytic effect, even a weak effect compared
with that of crystalline TiO.sub.2, which is the case with tin oxide or amorphous
titanium oxide.
A layer of "mixed" oxide thus combining at least partially crystalline titanium oxide
with at least one other oxide can be advantageous from an optical viewpoint, very
particularly if the other oxide or oxides are chosen with a lower index than that of
TiO.sub.2 : by lowering the "overall" refractive index of the coating, it is possible to
vary the light reflection of the substrate provided with the coating, in particular to
lower this reflection. This is the case if, for example, a layer made of TiO.sub.2
/Al.sub.2 O.sub.3, a method for the preparation of which is described in Patent
EP-0,465,309, or made of TiO.sub.2 /SiO.sub.2 is chosen. It is necessary, of course,
for the coating to contain however a TiO.sub.2 content which is sufficient to maintain
a significant photocatalytic activity. It is thus considered that it is preferable for the
coating to contain at least 40% by weight, in particular at least 50% by weight, of
TiO.sub.2 with respect to the total weight of oxide(s) in the coating.
It is also possible to choose to superimpose, with the coating according to the
invention, a grafted oleophobic and/or hydrophobic layer which is stable or resistant
to photocatalysis, for example based on the fluorinated organosilane described in U.S.
Pat. No. 5,368,892 and U.S. Pat. No. 5,389,427 and on the perfluoroalkylsilane
described in Patent Application FR 94/08734 of Jul. 13, 1994, published under the
number FR-2,722,493 and corresponding to European Patent EP-0,692,463, in
particular of formula:
CF.sub.3 --(CF.sub.2).sub.n --(CH.sub.2).sub.m --SiX.sub.3
in which n is from 0 to 12, m is from 2 to 5 and X is a hydrolysable group.
To amplify the photocatalytlc effect of the titanium oxide of the coating according to
the invention, it is possible first of all to increase the absorption band of the coating,
by incorporating other particles in the coating, in particular metal particles or particles
based on cadmium, tin, tungsten, zinc, cerium or zirconium.
It is also possible to increase the number of charge carriers by doping the crystal
lattice of the titanium oxide by inserting therein at least one of the following metal
elements: niobium, tantalum, iron, bismuth, cobalt, nickel, copper, ruthenium, cerium
or molybdenum.
This doping can also be carried out by surface doping only of the titanium oxide or of
the combined coating, surface doping carried out by covering at least part of the
coating with a layer of metal oxides or salts, the metal being chosen from iron, copper,
ruthenium, cerium, molybdenum, vanadium and bismuth.
Finally, the photocatalytic phenomenon can be accentuated by increasing the yield
and/or the kinetics of the photocatalytic reactions, by covering the titanium oxide, or
at least part of the coating which incorporates it, with a noble metal in the form of a
thin layer of the platinum, rhodium, silver or palladium type.
Such a catalyst, for example deposited by a vacuum technique, in fact makes it
possible-to increase the number and/or the lifetime of the radical entities created by
the titanium oxide and thus to promote the chain reactions leading to the degradation
of organic products.
In an entirely surprising way, the coating exhibits in fact not one property but two, as
soon as it is exposed to appropriate radiation, as in the visible and/or ultraviolet field,
such as sunlight: by the presence of photocatalytic titanium oxide, as already seen, it
promotes the gradual disappearance, as they are accumulated, of dirty marks of
organic origin, their degradation being caused by a radical oxidation process.
Inorganic dirty marks are not, themselves, degraded by this process: they therefore
remain on the surface and, except for a degree of crystallization, they are in part easily
removed since they no longer have any reason to adhere to the surface, the binding
organic agents being degraded by photocatalysis.
However, the coating of the invention, which is permanently self-cleaning, also
preferably exhibits an external surface with a pronounced hydrophilic and/or
oleophilic nature which results in three very advantageous effects:
hydrophilic nature makes possible complete wetting of the water which can be
deposited on the coating. When a water condensation phenomenon takes place,
instead of a deposit of water droplets in the form of condensation which hampers
visibility, there is in fact a continuous thin film of water which is formed on the
surface of the coating and which is entirely transparent. This "anti-condensation"
effect is in particular demonstrated by the measurement of a contact angle with water
of less than 5.degree. after exposure to light, and
after running of water, in particular of rain,; over a surface which has not been treated
with a photocatalytic layer, many drops of rainwater remain stuck to the surface and
leave, once evaporated, unattractive and troublesome marks, mainly of inorganic
origin. Indeed, a surface exposed to the surrounding air is rapidly covered by a layer
of dirty marks which limits the wetting thereof by water. These dirty marks are in
addition to the other dirty marks, in particular inorganic marks (crystallizations and
the like), contributed by the atmosphere in which the glazing bathes. In the case of a
photoreactive surface, these inorganic dirty marks are not directly degraded by
photocatalysis. In fact, they are in very large part removed by virtue of the hydrophilic
nature induced by the photo-catalytic activity. This hydrophilic nature indeed causes
complete spreading of the drops of rain. Evaporation marks are therefore no longer
present. Moreover, the other inorganic dirty marks present on the surface are washed,
or redissolved in the case of crystallization, by the water film and are thus in large
part removed. An "inorganic dirt-repellent" effect is obtained, induced in particular by
rain,
in conjunction with a hydrophilic nature, the coating can also exhibit an oleophilic
nature which makes possible the "wetting" of the organic dirty marks which, as with
water, then tend to be deposited on the coating in the form of a continuous film which
is less visible than highly localized "stains". An "organic dirt-repellent" effect is thus
obtained which operates in two ways: as soon as it is deposited on the coating, the
dirty mark is already not very visible. Subsequently, it gradually disappears by radical
degradation initiated by photocatalysis.
The coating can be chosen with a more or less smooth surface. A degree of roughness
can indeed be advantageous:
it makes it possible to develop a greater active photocatalytic surface area and thus
induces a greater photocatalytic activity,
it has a direct effect on the wetting. The roughness in fact enhances the wetting
properties. A smooth hydophilic surface will be even more hydrophilic once rendered
rough. "Roughness" is understood to mean, in this instance, both the surface
roughness and the roughness induced by a porosity of the layer in at least a portion of
its thickness.
The above effects will be all the more marked when the coating is porous and rough,
resulting in a superhydrophilic effect for rough photoreactive surfaces. However,
when exaggerated, the roughness can be penalizing by promoting incrustation or
accumulation of dirty marks and/or by bringing about the appearance of an optically
unacceptable level of fuzziness.
It has thus proved to be advantageous to adapt the method for deposition of TiO.sub.2
-based coatings so that they exhibit a roughness of approximately 2 to 20 nm,
preferably of 5 to 15 nm, this roughness being evaluated by atomic force microscopy,
by measurement of the value of the root mean square or RMS over a surface area of 1
square micrometre. With such roughnesses, the coatings exhibit a hydrophilic nature
which is reflected by a contact angle with water which can be less than 1.degree.. It
has also been found that it is advantageous to promote a degree of porosity in the
thickness of the coating. Thus, if the coating consists only of TiO.sub.2, it preferably
exhibits a porosity of the order of 65 to 99%, in particular of 70 to 90%, the porosity
being defined in this instance indirectly by the percentage of the theoretical relative
density of TiO.sub.2, which is approximately 3.8. One means for promoting such a
porosity comprises, for example, the deposition of the coating by a technique of the
sol-gel type involving the decomposition of materials of organometallic type: an
organic polymer of polyethylene glycol PEG type can then be introduced into the
solution, in addition to the organometallic precursor(s): on curing the layer by heating,
the PEG is burnt off, which brings about or accentuates a degree of porosity in the
thickness of the layer.
The thickness of the coating according to the invention is variable; it is preferably
between 5 nm and 1 micron, in particular between 5 and 100 nm, in particular
between 10 and 80 nm, or between 20 and 50 nm. In fact, the choice of the thickness
can depend on various parameters, in particular on the targeted application of the
substrate of the glazing type or alternatively on the size of the TiO.sub.2 crystallites in
the coating or on the presence of a high proportion of alkali metals in the substrate.
It is possible to arrange, between the substrate and the coating according to the
invention, one or a number of other thin layers with a different or complementary
function to that of the coating. It can concern, in particular, layers with an anti-static,
thermal or optical function or promoting the crystal-line growth of TiO.sub.2 in the
anatase or rutile form or of layers forming a barrier to the migration of certain
elements originating from the substrate, in particular forming a barrier to alkali metals
and very particularly to sodium ions when the substrate is made of glass.
It is also possible to envisage a stack of alternating "anti-glare" layers of thin layers
with high and low indices, the coating according to the invention constituting the final
layer of the stack. In this case, it is preferable for the coating to have a relatively low
refractive index, which is the case when it is composed of a mixed oxide of titanium
and of silicon.
The layer with an anti-static and/or thermal function (heating by providing it with
power leads, low-emissive, anti-solar, and the like) can in particular be chosen based
on a conductive material of the metal type, such as silver, or of the doped metal oxide
type, such as indium oxide doped with tin ITO, tin oxide doped with a halogen of the
fluorine type SnO.sub.2 :F or with antimony SnO.sub.2 :Sb or zinc oxide doped with
indium ZnO:In, with fluorine ZnO:F, with aluminium ZnO:Al or with tin ZnO:Sn. It
can also concern metal oxides which are stoichiometrically deficient in oxygen, such
as SnO.sub.2-x or ZnO.sub.2-x with x<2.
The layer with an anti-static function preferably has a surface resistance value of 20 to
1000 ohms.square. Provision can be made for furnishing it with power leads in order
to polarize it (feeding voltages for example of between 5 and 100 V). This controlled
polarization makes it possible in particular to control the deposition of dust with a size
of the order of a millimeter capable of being deposited on the coating, in particular
dry dust which adheres only by an electrostatic effect: by suddenly reversing the
polarization of the layer, this dust is "ejected".
The thin layer with an optical function can be chosen in order to decrease the light
reflection arid/or to render more neutral the colour in reflection of the substrate. In
this case, it preferably exhibits a refractive index intermediate between that of the
coating and that of the substrate and an appropriate optical thickness and can be
composed of an oxide or of a mixture of oxides of the aluminium oxide Al.sub.2
O.sub.3, tin oxide SnO.sub.2, indium oxide In.sub.2 O.sub.3 or silicon oxycarbide or
oxynitride type. In order to obtain maximum attenuation of the colour in reflection, it
is preferable for this thin layer to exhibit a refractive index close to the square root of
the product of the squares of the refractive indices of the two materials which frame it,
that is to say the substrate and the coating according to the invention. In the same way,
it is advantageous to choose its optical thickness (that is to say the product of its
geometric thickness and of its refractive index) similar to lambda/4, lambda being
approximately the average wavelength in the visible, in particular from approximately
500 to 550 nm.
The thin layer with a barrier function with respect to alkali metals can be in particular
chosen based on silicon oxide, nitride, oxynitride or oxycarbide, made of aluminium
oxide containing fluorine Al.sub.2 O.sub.3 :F or alternatively made of aluminium
nitride. In fact, it has proved to be useful when the substrate is made of glass, because
the migration of sodium ions into the coating according to the invention can, under
certain conditions, detrimentally affect the photocatalytic properties thereof.
The nature of the substrate or of the sublayer furthermore has an additional advantage:
it can promote the crystallization of the photocatalytic layer which is deposited, in
particular in the case of CVD deposition.
Thus, during deposition of TiO.sub.2 by CVD, a crystalline SnO.sub.2 :F sublayer
promotes the growth of TiO.sub.2 mostly in the rutile form, in particular for
deposition temperatures of the order of 400.degree. to 500.degree. C., whereas the
surface of a soda-lime glass or of a silicon oxycarbide sublayer rather induces an
anatase growth, in particular for deposition temperatures of the order of 400.degree. to
600.degree. C.
All these optional thin layers can, in a known way, be deposited by vacuum
techniques of the cathodic sputtering type or by other techniques of the thermal
decomposition type, such as solid, liquid or gas phase pyrolyses. Each of the
abovementioned layers can combine a number of functions but it is also possible to
superimpose them.
Another subject of the invention is "dirt-repellent" (organic and/or inorganic dirty
marks) and/or "anti-condensation" glazing, whether it is monolithic or insulating
multiple units of the double glazing or laminated type, which incorporates the coated
substrates described above.
The invention is thus targeted at the manufacture of glass, ceramic or vitroceramic
products and very particularly at the manufacture of "self-cleaning" glazing. The latter
can advantageously be building glazing, such as double glazing (it is then possible to
arrange the coating "external side" and/or "internal side", that is to say on face 1
and/or on face 4). This proves to be very particularly advantageous for glazing which
is not very accessible to cleaning and/or which needs to be cleaned very frequently,
such as roofing glazing, airport glazing, and the like. It can also relate to vehicle
windows where maintenance of visibility is an essential safety criterion. This coating
can thus be deposited on car windscreens, side windows or rear windows, in particular
on the face of the windows turned towards the inside of the passenger compartment.
This coating can then prevent the formation of condensation and/or remove traces of
dirty finger mark, nicotine or organic material type, the organic material being of the
volatile plasticizing type released by the plastic lining the interior of the passenger
compartment, in particular that of the dashboard (release sometimes known under the
term "fogging"). Other vehicles such as planes or trains can also find it advantageous
to use windows furnished with the coating of the invention.
A number of other applications are possible, in particular for aquarium glass, shop
windows, green houses, verandas, or glass used in interior furniture or street furniture
but also mirrors, television screens, the spectacle field or any architectural material of
the facing material, cladding material or roofing material type, such as tiles, and the
like.
The invention thus makes it possible to funcationalize these known products by
conferring on them anti-ultraviolet, dirt-repellent, bactericidal, anti-glare, anti-static or
antimicrobial properties and the like.
Another advantageous application of the coating according to the invention consists in
combining it with an electrically controlled variable absorption glazing of the
following types: electrochromic glazing, liquid crystal glazing, optionally with
dichroic dye, glazing containing a system of suspended particles, viologen glazing
and the like. As all these glazing types are generally composed of a plurality of
transparent substrates, between which are arranged the "active" elements, it is then
possible advantageously to arrange the coating on the external face of at least one of
these substrates.
In particular in the case of an electrochromic glazing, when the latter is in the
coloured state, its absorption results in a degree of surface heating which, in fact, is
capable of accelerating the photocatalytic decomposition of the carbonaceous
substances which are deposited on the coating according to the invention. For further
details on the structure of an electrochromic glazing, reference will advantageously be
made to Patent Application EP-A-0,575,207, which describes an electrochromic
laminated double glazing, it being possible for the coating according to the invention
preferably to be positioned on face 1.
Another subject of the invention is the various processes for obtaining the coating
according to the invention. It is possible to use a deposition technique of the pyrolysis
type which is advantageous because it in particular makes possible the continuous
deposition of the coating directly on the float-glass strip when a glass substrate is used.
The pyrolysis can be carried out in the solid phase, from powder(s) of precursor(s) of
the organo-metallic type.
The pyrolysis can be carried out in the liquid phase, from a solution comprising an
organometallic titanium precursor of the titanium chelate and/or titanium alcoholate
type. Such precursors are mixed with at least one other organometallic precursor. For
further details on the nature of the titanium precursor or on the deposition conditions,
reference will be made, for example, to Patents FR-2,310,977 and EP-0,465,309.
The pyrolysis can also be carried out in the vapour phase, which technique is also
denoted under the term of CVD (Chemical Vapour Deposition), from at least one
titanium precursor of the halide type, such as TiCl.sub.4, or titanium alcoholate of the
Ti tetraisopropylate type, Ti(OiPr).sub.4. The crystallization of the layer can
additionally be controlled by the type of sublayer, as mentioned above.
It is also possible to deposit the coating by other techniques, in particular by
techniques in combination with the "sol-gel". Various deposition methods are possible,
such as "dipping", also known as "dip coating", or a deposition using a cell known as
"cell coating". It can also concern a method of deposition by "spray coating" or by
laminar coating, the latter technique being described in detail in Patent Application
WO-94/01598. All these deposition methods in general use a solution comprising at
least one organometallic precursor, in particular titanium of the. alcoholate type,
which is thermally decomposed after coating the substrate with the solution on one of
its faces or on both its faces.
It can be advantageous, moreover, to deposit the coating, whatever the deposition
technique envisaged, not in a single step but via at least two successive stages, which
appears to promote the crystallization of titanium oxide throughout the thickness of
the coating when a relatively thick coating is chosen.
Likewise, it is advantageous to subject the coating with a photocatalytic property,
after deposition, to a heat treatment of the annealing type. A heat treatment is essential
for a technique of the sol-gel or laminar coating type in order to decompose the
organometallic precursor(s) to oxide, once the substrate has been coated, and to
improve the resistance to abrasion, which is not the case when a pyrolysis technique is
used, where the precursor decomposes as soon as it comes into contact with the
substrate. In the first case, as in the second, however, a post-deposition heat treatment,
once the TiO.sub.2 has been formed, improves its degree of crystallization. The
chosen treatment temperature can in addition make possible better control of the
degree of crystallization and of the crystalline nature, anatase and/or rutile, of the
oxide.
However, in the case of a substrate made of soda-lime glass, multiple and prolonged
annealings can promote attenuation of the photocatalytic activity because of an
excessive migration of the alkali metals from the substrate towards the photoreactive
layer. The use of a barrier layer between the substrate, if it is made of standard glass,
and the coating, or the choice of a substrate made of glass with an appropriate
composition, or alternatively the choice of a soda-lime glass with a surface from
which alkali metals have been eliminated make it possible to remove this risk.
Other advantageous details and characteristics of the invention emerge from the
description below of non-limiting implementational examples, with the help of the
following figures:
FIG. 1: a cross-section of a glass substrate provided with the coating according to the
invention,
FIG. 2: a diagram of a sol-gel deposition technique, by so-called "dip coating" the
coating,
FIG. 3: a diagram of a so-called "cell coating" deposition technique,
FIG. 4: a diagram of a so-called "spray coating" deposition technique,
FIG. 5: a diagram of a deposition technique by laminar coating.
As represented very diagrammatically in FIG. 1, all the following examples relate to
the deposition of a so-called "dirt-repellent" coating 3, essentially based on titanium
oxide, on a transparent substrate 1.
The substrate 1 is made of clear soda-lime-silica glass with a thickness of 4 mm and a
length and width of 50 cm. It is obvious that the invention is not limited to this
specific type of glass. The glass can in addition not be flat but bent.
Between the coating 3 and the substrate 1 is found a thin optional layer 2, either based
on silicon oxycarbide, written as SiOC, for the purpose of constituting a barrier to the
diffusion of the alkali metals and/or a layer which attenuates light reflection, or based
on tin oxide doped with fluorine SnO.sub.2 :F, for the purpose of constituting an
anti-static and/or low-emissive layer, even with a not very pronounced low-emissive
effect, and/or a layer which attenuates the colour, in particular in reflection.
EXAMPLES 1 TO 3
Examples 1 to 3 relate to a coating 3 deposited using a liquid phase pyrolysis
technique. The operation can be carried out continuously, by using a suitable
distribution nozzle arranged transversely and above the float-glass strip at the outlet of
the float-bath chamber proper. In this instance, the operation is carried out
non-continuously, by using a moveable nozzle arranged opposite the substrate 1
already cut to the dimensions shown, which substrate is first heated in an oven to a
temperature of 400 to 650.degree. C. before progressing a constant speed past the
nozzle spraying at an appropriate solution.
EXAMPLE 1
In this example, there is no optional layer 2. The coating 3 is deposited using a
solution comprising two organometallic titanium precursors, titanium diisopropoxide
diacetylacetonate and titanium tetraoctyleneglycolate, dissolved in a mixture of two
solvents, the latter being ethyl acetate and isopropanol.
It should be noted that it is also entirely possible to use other precursors of the same
type, in particular other titanium chelates of the titanium acetylacetonate, titanium
(methyl acetoacetato), titanium (ethyl acetoacetato) or alternatively titanium
triethanolaminato or titanium diethanolaminato type.
As soon as the substrate 1 has reached the desired temperature in the oven, i.e. in
particular approximately 500.degree. C., the substrate progresses past the nozzle
which sprays at room temperature, using compressed air, the mixture shown.
A TiO.sub.2 layer with a thickness of approximately 90 nm is then obtained, it being
possible for the thickness to be controlled by the rate of progression of the substrate 1
past the nozzle and/or the temperature of the said substrate. The layer is partially
crystalline in the anatase form.
This layer exhibits excellent mechanical behaviour. Its resistance to abrasion tests is
comparable with that obtained for the surface of the bare glass.
It can be bent and dip coated. It does not exhibit bloom: the scattered light
transmission of the coated substrate is less than 0.6% (measured according to the
D.sub.65 illuminant at 560 nm)
EXAMPLE 2
Example 1 is repeated but inserting, between the substrate 1 and coating 3, an
SnO.sub.2 :F layer 2 with a thickness of 73 nm. This layer is obtained by powder
pyrolysis from dibutyltin difluoride DBTF. It can also be obtained, in a known way,
by pyrolysis in the liquid or vapour phase, as is for example described in Patent
Application EP-A-0,648,196. In the vapour phase, it is possible in particular to use a
mixture of monobutyltin trichloride and of a fluorinated precursor optionally in
combination with a "mild" oxidant of the H.sub.2 O type.
The index of the layer obtained is approximately 1.9. Its surface resistance is
approximately 50 ohms.
In the preceding Example 1, the coated substrate 1, mounted as a double glazing so
that the coating is on face 1 (with another substrate 1' which is non-coated but of the
same nature and dimensions as the substrate 1 via a 12 mm layer of air), exerts a
colour saturation value in reflection of 26% and a colour saturation value in
transmission of 6.8%.
In this Example 2, the colour saturation in reflection (in the goldens) is only 3.6% and
it is 1.1% in transmission.
Thus, the SnO.sub.2 :F sublayer makes it possible to confer, on the substrate,
anti-static properties due to its electrical conductivity and it also has a favourable
effect on the colorimetry of the substrate, by making its coloration markedly more
"neutral", both in transmission and in reflection, which coloration is caused by the
presence of the titanium oxide coating 3 exhibiting a relatively high refractive index.
It is possible to polarize it by providing it with a suitable electrical supply, in order to
limit the deposition of dust with a relatively large size, of the order of a millimeter.
In addition, this sublayer decreases the diffusion of alkali metals into the
photocatalytic TiO.sub.2 layer. The photocatalytic activity is thus improved.
EXAMPLE 3
Example 2 is repeated but this time inserting, between substrate 1 and coating 3, a
layer 2 based on silicon oxycarbide with an index of approximately 1.75 and a
thickness of approximately 50 nm, which layer can be obtained by CVD from a
mixture of SiH.sub.4 and ethylene diluted in nitrogen, as described in Patent
Application EP-A-0,518,755. This layer is particularly effective in preventing the
tendency of alkali metals (Na.sup.+, K.sup.+) and of alkaline-earth metals (Ca.sup.++)
originating from the substrate to diffuse towards the coating 3 and thus the
photocatalytic activity is markedly improved. As it has, like SnO.sub.2 :F, a refractive
index intermediate between that of the substrate (1.52) and of the coating 3
(approximately 2.30 to 2.35), it also makes it possable to reduce the intensity of the
coloration of the substrate, both in reflection and in transmission, and overall to
decrease the light reflection value R.sub.L of the said substrate.
The following Examples 4 to 7 relate to depositions by CVD.
EXAMPLES 4 TO 7
EXAMPLE 4
This example relates to the deposition by CVD of the coating 3 directly on the
substrate 1 using a standard nozzle, such as that represented in the above-mentioned
Patent Application EP-A-0,518,755. Use is made, as precursors, either of an
organometallic compound or of a metal halide. In this instance, titanium
tetraisopropylate is chosen as organometallic compound, this compound being
advantageous because of its high volatility and its large working temperature range,
from 300 to 650.degree. C. In this example, deposition is carried out at approximately
425.degree. C. and the TiO.sub.2 thickness is 15 nm.
Tetraethoxytitanium Ti(O-Et).sub.4 may also be suitable and, as halide, mention may
be made of TiCl.sub.4.
EXAMPLE 5
It is carried out similarly to Example 4, except that, in this instance, the 15 nm
TiO.sub.2 layer is not deposited directly on the glass but on a 50 nm SiOC sublayer
deposited as in Example 3.
EXAMPLE 6
It is carried out as in Example 4, except that, in this instance, the thickness of the
TiO.sub.2 layer is 65 nm.
EXAMPLE 7
It is carried out as in Example 5, except that, in this instance, the thickness of the
TiO.sub.2 layer is 60 nm.
From these Examples 4 to 7, it is found that the substrates thus coated exhibit good
mechanical behaviour with respect to the abrasion tests. In particular, no delamination
of the TiO.sub.2 layer is observed.
EXAMPLE 8
This example uses a technique in combination with the sol-gel using a deposition
method by "dipping", also known as "dip coating", the principle of which emerges
from FIG. 2: it consists in immersing the substrate 1 in the liquid solution 4 containing
the appropriate precursor(s) of the coating 3 and in then withdrawing the substrate 1
therefrom at a controlled rate using a motor means 5, the choice of the rate of
withdrawal making it possible to adjust the thickness of solution remaining at the
surface of the two faces of the substrate and, in fact, the thickness of the coatings
deposited, after heat treatment of the latter in order both to evaporate the solvent and
to decompose the precursor or precursors to oxide.
Use is made, for depositing the coating 3, of a solution 4 comprising either titanium
tetrabutoxide Ti(O-Bu).sub.4, stabilized with diethanolamine DEA in the molar
proportion 1:1, in an ethanol-type solvent containing 0.2 mol of tetrabutoxide per litre
of ethanol, or the mixture of precursors and of solvents described in Example 1.
(Another precursor, such as titanium (diethanolaminato)dibutoxide, can also be used).
The substrates 1 can contain SiOC sublayers.
After withdrawal from each of the solutions 4, the substrates 1 are heated for 1 hour at
100.degree. C. and then for approximately 3 hours at 550.degree. C. with the
temperature raised gradually.
A coating 3 is obtained on each of the faces, which coating is in both cases made of
highly crystal-line TiO.sub.2 in the anatase form.
EXAMPLE 9
This example uses the technique known as "cell coating", the principle of which is
recalled in FIG. 3. It relates to forming a narrow cavity, delimited by two substantially
parallel faces 6,7 and two seals 8, 9, at least one of these faces 6, 7 consisting of the
face of the substrate 1 to be treated. The cavity is then filled with the solution 4 of
precursors) of the coating and the solution 4 is withdrawn in a controlled way, so as to
form a wetting meniscus, for example using a peristaltic pump 10, leaving a film of
the solution 4 on the face of the substrate 1 as this solution is withdrawn.
The cavity 5 is then maintained for at least the time necessary for drying. The film is
cured by heat treatment. The advantage of this technique, in comparison with "dip
coating", is in particular that it is possible to treat only a single one of the two faces of
the substrate 1 and not both systematically, unless a masking system is resorted to.
The substrates 1 comprise thin layers 2 based on silicon oxycarbide SiOC.
Example 6 uses respectively the solutions 4 described in Example 8. The same heat
treatments are then carried out in order to obtain the TiO.sub.2 coating 3.
The coating 3 exhibits good mechanical durability.
Under an SEM (scanning electron microscope), a field effect appears in the form of
"grains" of mono-crystals with a diameter of approximately 30 nm. The roughness of
this coating induces wetting properties which are enhanced with respect to a
non-rough coating.
These same solutions 4 can also be used to deposit coatings by "spray coating", as
represented in FIG. 4, where the solution 4 is sprayed in the form of a cloud against
the substrate 1 statically, or by laminar coating, as represented in FIG. 5. In the latter
case, the substrate 1, held by vacuum suction against a support 11 made of stainless
steel and Teflon, is passed over a tank 12 containing the solution, in which solution is
partially immersed a slotted cylinder 14, and the combined tank 12 and cylinder 14
are then moved over the whole length of the substrate 1, the mask 13 preventing
excessive evaporation of the solvent from the solution 4. For further details regarding
this latter technique, reference will advantageously be made to the abovementioned
Patent Application WO-94/01598.
Tests were carried out on the substrates obtained according to the above examples in
order to characterize the coatings deposited and to evaluate their "anti-condensation"
and "dirt-repellent" behaviour.
Test 1:
This is the test of the condensation aspects. It consists in observing the consequences
of the photocatalysis and of the structure of the coating (level of hydroxyl groups,
porosity, roughness) on the wetting. If the surface is photo-reactive, the carbonaceous
microcontaminants which are deposited on the coating are continually destroyed and
the surface is hydrophilic and thus anti-condensation It is also possible to carry out a
quantitative evaluation by suddenly reheating the initially coated substrate, stored in
the cold or simply by blowing over the substrate, by measuring if condensation
appears and, in the affirmative, at what time, and by then measuring the time
necessary for the disappearance of the said condensation.
Test 2:
It relates to the evaluation of the hydrophilicity and the oleophilicity at the surface of
the coating 3, in comparison with those of the surface of a bare glass, by measurement
of contact angles of a drop of water and of a drop of DOP (dioctyl phthalate) at their
surfaces, after having left the substrates for one week in the surrounding atmosphere
under natural light, in the dark and then having subjected them to UVA radiation for
20 minutes.
Test 3:
It consists in depositing, on the substrate to be evaluated, a layer of an organosilane
and in irradiating it with UVA radiation so as to degrade it by photocatalysis. As the
organosilane modifies the wetting properties, measurements of contact angle of the
substrate with water during the irradiation indicate the state of degradation of the
grafted layer. The rate of disappearance of this layer is related to the photocatalytic
activity of the substrate.
The grafted organosilane is a trichlorosilane: octadecyltrichlorosilane (OTS). The
grafting is carried out by dipping.
The test device is composed of a turntable rotating around from 1 to 6 low pressure
UVA lamps. The test specimens to be evaluated are placed in the turntable, the face to
be evaluated on the side of the UVA radiation. Depending on their position and the
number of lamps switched on, each test specimen receives a UVA irradiation varying
from 0.5 W/m.sup.2 to 50 W/m.sup.2. For Examples 1, 2, 3, 8 and 9, the irradiation
power is chosen as 1.8 W/m.sup.2 and, for Examples 4 to 7, as 0.6 W/m.sup.2.
The time between each measurement of the contact angle varies between 20 min and
3 h, depending on the photocatalytic activity of the test specimen under consideration.
The measurements are carried out using a goniometer.
Before irradiation, the glasses exhibit an angle of approximately 100.degree.. It is
considered that the layer is destroyed after irradiation when the angle is less than
20.degree..
Each test specimen tested is characterized by the mean rate of disappearance of the
layer, given in nanometers per hour, that is to say the thickness of the organos-lane
layer deposited divided by the irradiation time which makes it possible to reach a final
stationary value of less than 20.degree. (time for disappearance of the organosilane
layer).
All the preceding examples pass Test 1, that is to say that, when the substrates coated
with the coating are blown on, they remain perfectly transparent, whereas a highly
visible layer of condensation is deposited on non-coated substrates.
The examples were subjected to Test 2: the coated substrates, after exposure to UVA
radiation, exhibit a contact angle with water and with DOP of not more than 5.degree..
In contrast, a bare glass under the same conditions exhibits a contact angle with water
of 40.degree. and a contact angle with DOP of 20.degree..
The results of the substrates coated according to the above examples in Test 3 are
combined in the table below.
Test 3, of wetting,
at 1.8 W/m.sup.2 UVA
Substrate
(in nm/h)
Example 1 (TiO.sub.2 on bare glass)
0.03
Example 2 (TiO.sub.2 on SnO.sub.2 :F)
Example 3 (TiO.sub.2 on SiOC)
Example 8 (TiO.sub.2 on 50 nm SiOC)
0.1
0.2
5
Example 9 (TiO.sub.2 on 50 nm SiOC)
5
Bare glass
0
Test 3, of wetting,
at 0.6 W/m.sup.2 UVA
Substrate (CVD)
(in nm/h)
Example 4 (TiO.sub.2 on bare glass)
<0.05 nm/h
Example 5 (TiO.sub.2 on SiOC)
4
Example 6 (TiO.sub.2 on bare glass)
Example 7 (TiO.sub.2 on SiOC)
9
19.5
From the table, it can be seen that the presence of sublayers, in particular of SIOC,
promotes the photocatalytic activity of the coating containing the TiO.sub.2, by its
barrier effect to alkali metals and alkaline-earth metals which can migrate from the
glass (comparison of Examples 4 and 5 or 6 and 7).
It is also observed that the thickness of the coating containing the TiO.sub.2 also plays
a role (comparison of Examples 1 and 3): for a TiO.sub.2 coating with a thickness
greater than the mean size of the monocrystals or "crystallites", a better photocatalytic
effect is obtained.
Indeed, it could be observed that the TiO.sub.2 coatings obtained by CVD exhibit the
most advanced crystallization, with crystallite sizes of the order of 20 to 30 nm. It can
be seen that the photocatalytic activity of Example 6 (65 nm of TiO.sub.2) is
markedly greater than that of Example 4 (15 nm of TiO.sub.2 only). It is therefore
advantageous to provide a TiO.sub.2 coating thickness at least two times greater than
the mean diameter of the crystallites which it contains. Alternatively, as in the case of
Example 5, it is possible to retain a TiO.sub.2 coating with a thin thickness but then to
choose to use a sublayer of an appropriate nature and with an appropriate thickness
for promoting as far as possible the crystalline growth of TiO.sub.2 from the "first"
layer of crystallites.
It could be observed that the crystallization of the TiO.sub.2 was somewhat less
advanced for the coatings deposited by a technique other than CVD. Here again,
however, everything is still a matter of compromise: a less advanced crystallization
and an a priori lower photocatalytic activity can be "compensated for" by the use of a
deposition process which is less expensive or less complex, for example. Moreover,
the use of an appropriate sublayer or the doping of the TiO.sub.2 can make it possible
to improve the photocatalytic behaviour, if necessary.
It is also confirmed, from the comparison of Examples 2 and 3, that the nature of the
sublayer influences the crystallization form and, in fact, the photocatalytic activity of
the coating.
(2
United States Patent
Hurst ,
of
4)
6,840,061
et al.
January 11, 2005
Coatings on substrates
Abstract
A process for the production of a photocatalytically active self-cleaning coated substrate,
especially a glass substrate, which comprises depositing a titanium oxide coating on the
surface of the substrate by contacting it with a fluid mixture containing a source of
titanium and a source of oxygen, the substrate being at a temperature of at least 600.degree.
C. The coated surface has good durability, a high photocatalytic activity and a low visible
light reflection. Most preferably the deposition temperature is in the range 645.degree. C.
to 7200.degree. C. which provides especially good durability. The fluid mixture preferably
contains titanium chloride and an ester, especially ethyl acetate. Also disclosed is a self
cleaning coated substrate, especially a glass substrate, having high photocatalytic activity
and low visible light reflection and a durable self-cleaning coated glass.
Inventors: Hurst; Simon James (Runcorn, GB); Ammerlaan; Johannes Andreas
Maria (Eindhoven, NL); McCurdy; Richard Joseph (Aurora, IL)
Assignee: Libbey-Owens-Ford Co. (Toledo, OH); Pilkington PLC (Merseyside,
GB)
Appl. No.: 587970
Filed:
June 6, 2000
Foreign Application Priority Data
Jun 08, 1999[GB]
9913315
65/60.51; 65/60.5; 65/99.1; 65/99.4
Current U.S. Class:
C03C 017/245
Intern'l Class:
65/60.5,60.51,60.52,60.53,99.1,99.4
Field of Search:
References Cited [Referenced By]
U.S. Patent Documents
4123244
Oct., 1978
Leclercq et al.
4329379
May., 1982
Terneu et al.
4351267
Sep., 1982
Kalbskopf et al.
4751149
Jun., 1988
Vijayakumar et al.
4878934
Nov., 1989
Thomas et al.
4971843
Nov., 1990
Michelotti et al.
4997576
Mar., 1991
Heller et al.
5041150
Aug., 1991
Grundy et al.
5194161
Mar., 1993
Heller et al.
5256616
Oct., 1993
Heller et al.
5308458
May., 1994
Urwin et al.
5393593
Feb., 1995
Gulotta et al.
5505989
Apr., 1996
Jenkinson.
5580364
Dec., 1996
Goodman et al.
118/305.
5853866
Dec., 1998
Watanabe et al.
5939194
Aug., 1999
Hashimoto et al.
6013372
Jan., 2000
Hayakawa et al.
6027766
Feb., 2000
Greenberg et al.
6027797
Feb., 2000
Watanabe et al.
6037289
Mar., 2000
Chopin et al.
6054227
Apr., 2000
Greenberg et al.
6090489
Jul., 2000
Hayakawa et al.
6110528
Aug., 2000
Kimura et al.
Foreign Patent Documents
684075
Jun., 1995
EP.
737513
Oct., 1996
EP.
0901991
Mar., 1999
EP.
2150044
Jun., 1978
GB.
1523991
Sep., 1978
GB.
1524326
Sep., 1978
GB.
1510587
Oct., 1978
GB.
63-100042
May., 1988
JP.
WO 97/07069
Feb., 1997
WO.
WO 97/97069
Feb., 1997
WO.
WO 97/10186
Mar., 1997
WO.
WO 98/06675
Feb., 1998
WO.
WO 98/41480
Sep., 1998
WO.
WO 98/41480
Sep., 1998
WO.
Other References
Journal of Materials Science Letters 9 (1990) 316-319, Kamata et al.; "Rapid
Formation of TiO.sub.2 Films By A Conventional CVD Method" no month
available.
Photocatalytic Activity of TiO2 Thin Film Under Room Light (in
Photocatalytic Purification and Treatment of Water and Air; eds. D.F. Ollis
and H, Al-Ekabi, p. 747 (1993), no month available.
427/218.
Hass, Georg; Thun, Rudolf E., Ed.; Physics of Thin Films; vol. 5 Academic
Press, New York, 1969, p. 237, pp. 304-306, no month available.
Pierson, Hugh O.; Handbook of Chemical Vapor Deposition (CVD); Noyes
Publications, Park Ridge, NJ, 1992, pp. 231-237, no month available.
Takashi, Manasari et al.; "PT-TIO2 Thin Films on Glass Substrates as
Efficient Photcatalysts"; J. Mat. Sci., 24 (1989) 243, no month available.
Fukayama, S. etal.; "Highly Tranparent and Photoactive TIO2 Thin Film
Coated on Glass Substrate"; 187th Electochemical Society Meeting, Abstract
No. 735, Extened Abstracts 95-1 (Available at Least by Mar. 1995).
Weinberger, B.R. et al.; "Titanium Dioxide Photocatalysts Produced by
Reactive Magnetron Sputtering"; Appl. Phys. Lett. 66 (1995) 2409, no month
available.
Kiernan, Vincent; "A Clearer View for Car Drivers"; New Scientist, Aug. 26,
1995, p. 19.
Paz, Y; Luo, A.; "Photooxideative Self-Cleaning Transparent Titanium
Dioxide Films on Glass"; J. Mater.Res., 10 (Nov. 1995) 2482.
Primary Examiner: Vincent; Sean
Attorney, Agent or Firm: Marshall & Melhorn, LLC
Claims
What is claimed is:
1. A process for the production of a durable photocatalytically active coated glass
which comprises depositing a photocatalytically active titanium oxide layer on the
surface of a glass ribbon formed during a float glass production process, said layer
having a thickness of 30 nm or less and a photoactivity of greater than
5.times.10.sup.-3 cm.sup.-1 min.sup.-1, by contacting the surface of the ribbon with a
gaseous mixture comprising a source of titanium while the ribbon is at a temperature
of from 625.degree. to 720.degree. C.
2. A process as claimed in claim 1 wherein the ribbon is at a temperature in the range
670.degree. C. to 720.degree. C.
3. A process as claimed in claim 1 wherein the gaseous mixture comprises titanium
tetraethoxide as the source of titanium.
4. A process as claimed in claim 1 wherein the gaseous mixture comprises titanium
chloride as the source of titanium and an ester other than a methyl ester.
5. A process as claimed in claim 4 wherein the ester comprises an alkyl ester having
an alkyl group with a .beta. hydrogen.
6. A process as claimed in claim 4 wherein the ester comprises a carboxylate ester.
7. A process as claimed in claim 4 wherein the ester is an alkyl ester having a C.sub.2
to C.sub.4 alkyl group.
8. A process as claimed in claim 7 wherein the ester comprises an ethyl ester.
9. A process as claimed in claim 8 wherein the ester comprises ethyl acetate.
10. A process as claimed in claimed in claim 4 wherein the ester is the only source of
oxygen in the fluid mixture.
11. A process as claimed in claim 1 wherein the process is performed at substantially
atmospheric pressure.
Description
BACKGROUND OF THE INVENTION
This invention relates to a process for producing photocatalytically active coated
substrates, in particular, but not exclusively, it relates to a process for producing
photocatalytically active coated glass and such coated glass.
It is known to deposit thin coatings having one or more layers, with a variety of
properties, on to substrates including on to glass substrates. One property of interest is
photocatalytic activity which arises by the photogeneration, in a semiconductor, of a
hole-electron pair when the semiconductor is illuminated by light of a particular
frequency. The hole-electron pair can be generated in sunlight and can react in humid
air to form hydroxy and peroxy radicals on the surface of the semiconductor. The
radicals oxidise organic grime on the surface. This property has an application in
self-cleaning substrates, especially in self-cleaning glass for windows.
Titanium dioxide may be an efficient photocatalyst and may be deposited on to
substrates to form a transparent coating with photocatalytic self-cleaning properties.
Titanium oxide photocatalytic coatings are disclosed in EP 0 901 991 A2, WO
97/07069, WO 97/10186, WO 98/41480, in Abstract 735 of 187th Electrochemical
Society Meeting (Reno, Nev., 95-1, p.1102) and in New Scientist magazine (26 Aug.
1995, p.19). In WO 98/06675 a chemical vapour deposition process is described for
depositing titanium oxide coatings on hot flat glass at high deposition rate using a
precursor gas mixture of titanium chloride and an organic compound as source of
oxygen for formation of the titanium oxide coating.
It has been thought that relatively thick titanium oxide coatings need to be deposited
to provide good photocatalytic activity. For example, in WO 98/41480 it is stated that
a photocatalytically active self-cleaning coating must be sufficiently thick so as to
provide an acceptable level of activity and it is preferred that such a coating is at least
about 200 .ANG. and more preferably at least about 500 .ANG. thick (the measured
thickness of the titanium oxide coatings produced in the Examples all being in the
range 400 .ANG. to 2100 .ANG.).
However, a problem of relatively thick titanium oxide coatings is high visible light
reflection and thus relatively low visible light transmission. This problem is
recognised in the article in New Scientist magazine in relation to coated windscreens,
where it is suggested that to reduce the effect of high reflection, dashboards might
have to be coated in black velvet or some other material that does not reflect light into
a coated windscreen.
EP 0 901 991A2 referred to above, relates to photocatalytic glass panes with a coating
of titanium oxide of a particular crystal structure characterised by the presence of
particular peaks in its X-ray diffraction pattern. The specification contemplates a
range of coating thickness (with the specific Examples all having thickness in the
range 20 nm to 135 nm, the thinner coatings being less photocatalytically active than
the thicker coatings). The specification also contemplates a range of deposition
temperatures from as low as 300.degree. C. to as high as 750.degree. C., but prefers
temperatures in the range 400.degree. C. to 600.degree. C., and in all the specific
Examples of the invention the titanium dioxide layer is deposited at a temperature in
or below this preferred range.
The applicants have now found that by depositing the titanium oxide coatings at
higher temperatures, especially temperatures above 600.degree. C., they are able to
achieve coatings with an enhanced photocatalytic activity for a given thickness,
enabling the same photocatalytic performance to be achieved with thinner coatings.
Such thinner coatings tend to have, advantageously, lower visible light reflection and,
apparently in consequence of their higher deposition temperature, improved durability,
especially to abrasion and temperature cycling in a humid atmosphere.
SUMMARY OF THE INVENTION
The present invention accordingly provides a process for the production of a
photocatalytically active coated substrate which comprises depositing a titanium
oxide coating on the surface of a substrate by contacting the surface of the substrate
with a fluid mixture containing a source of titanium and a source of oxygen, said
substrate being at a temperature of at least 600.degree. C., whereby the coated surface
of the substrate has a photocatalytic activity of greater than 5.times.10.sup.-3
cm.sup.-1 min.sup.-1 and a visible light reflection measured on the coated side of
35% or lower.
Preferably, the substrate is at a temperature in the range 625.degree. C. to 720.degree.
C., more preferably the substrate is at a temperature in the range 645.degree. C. to
720.degree. C.
Advantageously, the fluid mixture comprises titanium chloride as the source of
titanium and an ester other than a methyl ester. Thus, in a preferred embodiment, the
present invention provides a process for the production of a photocatalytically active
coated substrate which comprises depositing a titanium oxide coating having a
thickness of less than 40 nm on a substrate by contacting a surface of the substrate
with a fluid mixture comprising titanium chloride and an ester other than a methyl
ester.
The process may be performed wherein the surface of the substrate is contacted with
the fluid mixture when the substrate is at a temperature in the range 600.degree. C. to
750.degree. C.
Preferably, the ester is an alkyl ester having an alkyl group with a .beta. hydrogen (the
alkyl group of an alkyl ester is the group derived from the alcohol in synthesis of an
ester and a .beta. hydrogen is a hydrogen bonded to a carbon atom .beta. to the oxygen
of the ether linkage in an ester). Preferably the ester is a carboxylate ester.
Suitable esters may be alkyl esters having a C.sub.2 to C.sub.10 alkyl group, but
preferably the ester is an alkyl ester having a C.sub.2 to C.sub.4 alkyl group.
Preferably, the ester is a compound of formula: R--C(O)--O--C(X)(X')--C(Y)(Y')--R',
where R and R' represent hydrogen or an alkyl group, X, X', Y and Y' represent
monovalent substituents, preferably alkyl groups or hydrogen atoms and wherein at
least one of Y and Y' represents hydrogen.
Suitable esters that may be used in the process of the present invention include: ethyl
formate, ethyl acetate, ethyl propionate, ethyl butyrate, n-propyl formate, n-propyl
acetate, n-propyl propionate, n-propyl butyrate, isopropyl formate, isopropyl acetate,
isopropyl propionate, isopropyl butyrate, n-butyl formate, n-butyl acetate and t-butyl
acetate.
Preferably, the ester comprises an ethyl ester, more preferably the ester comprises
ethyl formate, ethyl acetate or ethyl propionate. Most preferably the ester comprises
ethyl acetate.
The fluid mixture may be in the form of a liquid, especially dispersed as a fine spray
(a process often referred to as spray deposition), but preferably the fluid mixture is a
gaseous mixture. A deposition process performed using a gaseous mixture as
precursor is often referred to as chemical vapour deposition (CVD). The preferred
form of CVD is laminar flow CVD, although turbulent flow CVD may also be used.
The process may be performed on substrates of various dimensions including on sheet
substrates, especially on cut sheets of glass, or preferably on-line during the float
glass production process on a continuous ribbon of glass. Thus, preferably, the process
is performed on-line during the float glass production process and the substrate is a
glass ribbon. If the process is performed on line, it is preferably performed on the
glass ribbon whilst it is in the float bath.
An advantage of performing the process on-line is that coatings deposited on-line tend
to be durable and in particular to have good abrasion and chemical resistance.
An on-line deposition process is preferably, and other deposition processes may be,
performed at substantially atmospheric pressure.
In a particularly preferred embodiment there is provided a process for the production
of a durable photocatalytically active coated glass which comprises depositing on the
surface of a glass substrate a photocatalytically active titanium oxide layer by
contacting the surface of the substrate, which is at a temperature in the range
645.degree. C. to 720.degree. C., preferably in the range 670.degree. C. to 720.degree.
C. with a fluid mixture containing a source of titanium.
As noted above, the applicants have found that by depositing the titanium oxide at
high temperature, a coating of relatively high photocatalytic activity for its thickness
may be produced and, as coatings of reduced thickness tend to have lower reflection,
the invention also provides novel products having an advantageous combination of
high photocatalytic activity with moderate or low light reflection.
Thus, the present invention, in another aspect, provides a photocatalytically active
coated substrate comprising a substrate having a photocatalytically active titanium
oxide coating on one surface thereof, characterised in that the coated surface of the
substrate has a photocatalytic activity of greater than 5.times.10.sup.-3 cm.sup.-1
min.sup.-1 and in that the coated substrate has a visible light reflection measured on
the coated side of 35% or lower.
High photocatalytic activity is advantageous because the amount of contaminants
(including dirt) on the coated surface of the photocatalytically active coated substrate
will be reduced quicker than on substrates with relatively low photocatalytic activity.
Also, relatively quick removal of surface contaminants will tend to occur at low levels
of UV light intensity.
Photocatalytic activity for the purposes of this specification is determined by
measuring the rate of decrease of the integrated absorbance of the infra-red absorption
peaks corresponding to the C--H stretches of a thin film of stearic acid, formed on the
coated substrate, under illumination by UV light from a UVA lamp having an intensity
of about 32 W/m.sup.2 at the surface of the coated substrate and a peak wavelength of
351 nm. The stearic acid may be formed on the coated substrate by spin casting a
solution of stearic acid in methanol as described below.
Preferably, the coated surface of the substrate has a photocatalytic activity of greater
than 1.times.10.sup.-2 cm.sup.-1 min.sup.-1, more preferably of greater than
3.times.10.sup.-2 cm.sup.-1 min.sup.-1.
Low visible light reflection is advantageous because it is less distracting than high
reflection and, especially for glass substrates, low visible light reflection corresponds
to high visible transmission which is often required in architectural and especially
automotive applications of glass.
Preferably, the coated substrate has a visible reflection measured on the coated side of
20% or lower more preferably of 17% or lower and most preferably of 15% or lower.
In most embodiments of the invention the substrate will be substantially transparent
and in a preferred embodiment of the invention the substrate comprises a glass
substrate. Usually the glass substrate will be a soda lime glass substrate.
Where the substrate is a soda lime glass substrate or other alkali metal ion containing
substrate, the coated substrate preferably has an alkali metal ion blocking underlayer
between the surface of the substrate and the photocatalytically active titanium oxide
coating. This reduces the tendency for alkali metal ions from the substrate to migrate
into the photocatalytically active titanium oxide coating which is advantageous
because of the well known tendency of alkali metal ions to poison semiconductor
oxide coatings, reducing their activity.
The alkali metal ion blocking underlayer may comprise a metal oxide but preferably
the alkali metal ion blocking layer is a layer of silicon oxide. The silicon oxide may
be silica but will not necessarily be stoichiometric and may comprise impurities such
as carbon (often referred to as silicon oxycarbide and deposited as described in GB
2,199,848B) or nitrogen (often referred to as silicon oxynitride).
It is advantageous if the alkali metal ion blocking underlayer is thin so that it has no
significant effect on the optical properties of the coating, especially by reducing the
transparency of a transparent coated substrate or causing interference colours in
reflection or transmission. The suitable thickness range will depend on the properties
of the material used to form the alkali metal ion blocking layer (especially its
refractive index), but usually the alkali metal ion blocking underlayer has a thickness
of less than 60 nm and preferably has a thickness of less than 40 nm. Where present,
the alkali metal ion blocking underlayer should always be thick enough to reduce or
block migration of alkali metal ions from the glass into the titanium oxide coating.
An advantage of the present invention is that the photocatalytically active titanium
oxide coating is thin (contributing to the low visible reflection of the coated substrate)
but the coated substrate still has excellent photocatalytic activity. Preferably, the
titanium oxide coating has a thickness of 30 nm or lower, more preferably the
titanium oxide coating has a thickness of 20 nm or lower and most preferably the
titanium oxide coating has a thickness in the range 2 nm to about 20 nm.
The present invention is also advantageous because depositing thin titanium oxide
coatings requires less precursor and the layers can be deposited in a relatively short
time. A thin titanium oxide coating is also less likely to cause interference colours in
reflection or transmission. However, a particular advantage is that the visible light
reflection of a thin titanium oxide coating is low which is especially important when
the coated substrate is coated glass. Usually the required visible light transmission of
the coated glass will determine the thickness of the titanium oxide coating.
Preferably, the coated surface of the substrate has a static water contact angle of
20.degree. or lower. Freshly prepared or cleaned glass has a hydrophilic surface (a
static water contact angle of lower than about 40.degree. indicates a hydrophilic
surface), but organic contaminants rapidly adhere to the surface increasing the contact
angle. A particular benefit of coated substrates (and especially coated glasses) of the
present invention is that even if the coated surface is soiled, irradiation of the coated
surface by UV light of the right wavelength will reduce the contact angle by reducing
or destroying those contaminants. A further advantage is that water will spread out
over the low contact angle surface reducing the distracting effect of droplets of water
on the surface (e.g. from rain) and tending to wash away any grime or other
contaminants that have not been destroyed by the photocatalytic activity of the surface.
The static water contact angle is the angle subtended by the meniscus of a water
droplet on a glass surface and may be determined in a known manner by measuring
the diameter of a water droplet of known volume on a glass surface and calculated
using an iterative procedure.
Preferably, the coated substrate has a haze of 1% or lower, which is beneficial because
this allows clarity of view through a transparent coated substrate.
In preferred embodiments, the coated surface of the substrate is durable to abrasion,
such that the coated surface remains photocatalytically active after it has been
subjected to 300 strokes of the European standard abrasion test. Preferably, the coated
surface remains photocatalytically active after it has been subjected to 500 strokes of
the European standard abrasion test, and more preferably the coated surface remains
photocatalytically active after it has been subjected to 1000 strokes of the European
standard abrasion test.
This is advantageous because self-cleaning coated substrates of the present invention
will often be used with the coated surface exposed to the outside (e.g. coated glasses
with the coated surface of the glass as the outer surface of a window) where the
coating is vulnerable to abrasion.
The European standard abrasion test refers to the abrasion test described in European
standard BS EN 1096 Part 2 (1999) and comprises the reciprocation of a felt pad at a
set speed and pressure over the surface of the sample.
In the present specification, a coated substrate is considered to remain
photocatalytically active if, after being subjected to the European abrasion test,
irradiation by UV light (e.g. of peak wavelength 351 nm) reduces the static water
contact angle to below 15.degree.. To achieve this contact angle after abrasion of the
coated substrate will usually take less than 48 hours of irradiation at an intensity of
about 32 W/m.sup.2 at the surface of the coated substrate.
Preferably, the haze of the coated substrate is 2% or lower after being subjected to the
European standard abrasion test.
Durable coated substrates according to the present invention may also be durable to
humidity cycling (which is intended to have a similar effect to weathering). Thus, in
preferred embodiments of the invention, the coated surface of the substrate is durable
to humidity cycling such that the coated surface remains photocatalytically active
after the coated substrate has been subjected to 200 cycles of the humidity cycling test.
In the present specification, the humidity cycling test refers to a test wherein the
coating is subjected to a temperature cycle of 35.degree. C. to 75.degree. C. to
35.degree. C. in 4 hours at near 100% relative humidity. The coated substrate is
considered to remain photocatalytically active, if, after the test, irradiation by UV
light reduces the static water contact angle to below 15.degree..
In a further preferred embodiment, the present invention provides a durable
photocatalytically active coated glass comprising a glass substrate having a coating on
one surface thereof, said coating comprising an alkali metal ion blocking underlayer
and a photocatalytically active titanium oxide layer, wherein the coated surface of the
substrate is durable to abrasion such that the coated surface remains photocatalytically
active after it has been subjected to 300 strokes of the European standard abrasion test.
In this embodiment, the coated glass preferably has a visible light reflection measured
on the coated side of 35% or lower, and the photocatalytically active titanium oxide
layer preferably has a thickness of 30 nm or lower. Thin coatings are durable to
abrasion which is surprising because previously it has been thought that only
relatively thick coatings would have good durability.
In a still further embodiment, the present invention provides a coated glass
comprising a glass substrate having a photocatalytically active titanium oxide coating
on one surface thereof, characterised in that the coated surface of the glass has a
photocatalytic activity of greater than 4.times.10.sup.-2 cm.sup.-1 min.sup.-1,
preferably greater than 6.times.10.sup.-2 cm.sup.-1 min.sup.-1 and more preferably
greater than 8.times.10.sup.-2 cm.sup.-1 min.sup.-1 and in that the coated glass has a
visible light reflection measured on the coated side of less than 20%.
Coated substrates according to the present invention have uses in many areas, for
example as glazings in windows including in a multiple glazing unit comprising a first
glazing pane of a coated substrate in spaced opposed relationship to a second glazing
pane, or, when the coated substrate is coated glass, as laminated glass comprising a
first glass ply of the coated glass, a polymer interlayer (of, for example,
polyvinylbutyral) and a second glass ply.
In addition to uses in self-cleaning substrates (especially self-cleaning glass for
windows), coated substrates of the present invention may also be useful in reducing
the concentration of atmospheric contaminants. For example, coated glass under
irradiation by light of UV wavelengths (including UV wavelengths present in sunlight)
may destroy atmospheric contaminants for example, nitrogen oxides, ozone and
organic pollutants, adsorbed on the coated surface of the glass. This use is particularly
advantageous in the open in built-up areas (for example, in city streets) where the
concentration of organic contaminants may be relatively high (especially in intense
sunlight), but where the available surface area of glass is also relatively high.
Alternatively, the coated glass (with the coated surface on the inside) may be used to
reduce the concentration of atmospheric contaminants inside buildings, especially in
office buildings having a relatively high concentration of atmospheric contaminants.
The invention is illustrated but not limited by the following drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a graph of photocatalytic activity of coated glass produced by a process
according to the invention as a function of the thickness of the titanium oxide layer.
FIG. 2 illustrates apparatus for on line chemical vapour deposition of coatings
according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In FIG. 1 the coated glasses were produced using an on-line CVD process as
described in the Examples, below. The open circles 1 relate to titanium oxide layers
deposited using titanium tetrachloride as titanium precursor, and the crosses 2 relate to
titanium oxide layers deposited using titanium tetraethoxide as titanium precursor.
The layers of the coating may be applied on line onto the glass substrate by chemical
vapour deposition during the glass manufacturing process. FIG. 2 illustrates an
apparatus, indicated generally at 10, useful for the on line production of the coated
glass article of the present invention, comprising a float section 11, a lehr 12, and a
cooling section 13. The float section 11 has a bottom 14 which contains a molten tin
bath 15, a roof 16, sidewalls (not shown), and end walls 17, which together form a
seal such that there is provided an enclosed zone 18, wherein a non-oxidising
atmosphere is maintained to prevent oxidation of the tin bath 15. During operation of
the apparatus 10, molten glass 19 is cast onto a hearth 20, and flows therefrom under a
metering wall 21, then downwardly onto the surface of the tin bath 15, forming a float
glass ribbon 37, which is removed by lift-out rolls 22 and conveyed through the lehr
12, and thereafter through the cooling section 13.
A non-oxidising atmosphere is maintained in the float section 11 by introducing a
suitable gas, such as for example one comprising nitrogen and 2% by volume
hydrogen, into the zone 18, through conduits 23 which are operably connected to a
manifold 24. The non-oxidizing gas is introduced into the zone 18 from the conduits
23 at a rate sufficient to compensate for losses of the gas (some of the non-oxidizing
atmosphere leaves the zone 18 by flowing under the end walls 17), and to maintain a
slight positive pressure above ambient pressure. The tin bath 15 and the enclosed zone
18 are heated by radiant heat directed downwardly from heaters 25. The heat zone 18
is generally maintained at a temperature of about 1330.degree. F. to 1400.degree. F.
(721.degree. C. to 760.degree. C.). The atmosphere in the lehr 12 is typically air, and
the cooling section 13 is not enclosed. Ambient air is blown onto the glass by fans 26.
The apparatus 10 also includes coaters 27, 28, 29 and 30 located in series in the float
zone 11 above the float glass ribbon 37. The precursor gaseous mixtures for the
individual layers of the coating are supplied to the respective coaters, which in turn
direct the precursor gaseous mixtures to the hot surface of the float glass ribbon 37.
The temperature of the float glass ribbon 37 is highest at the location of the coater 27
nearest the hearth 20 and lowest at the location of the coater 30 nearest the lehr 12.
The invention is further illustrated by the following Examples, in which coatings were
applied by laminar flow chemical vapour deposition in the float bath on to a moving
ribbon of float glass during the glass production process. In the Examples two layer
coatings were applied to the glass ribbon.
All gas volumes are measured at standard temperature and pressure unless otherwise
stated. The thickness values quoted for the layers were determined using high
resolution scanning electron microscopy and optical modelling of the reflection and
transmission spectra of the coated glass. Thickness of the coatings was measured with
an uncertainty of about 5%. The transmission and reflection properties of the coated
glasses were determined using an Hitachi U-4000 spectrophotometer. The a, b and L*
values mentioned herein of the transmission and/or reflection colour of the glasses
refer to the CIE Lab colours. The visible reflection and visible transmission of the
coated glasses were determined using the D65 illuminant and the standard CIE
2.degree. observer in accordance with the ISO 9050 standard (Parry Moon airmass 2)
The haze of the coated glasses was measured using a WYK-Gardner Hazeguard+haze
meter.
The photocatalytic activity of the coated glasses was determined from the rate of
decrease of the area of the infrared peaks corresponding to C--H stretches of a stearic
acid film on the coated surface of the glass under illumination by UVA light. The
stearic acid film was formed on samples of the glasses, 7-8 cm square, by spin casting
20 .mu.l of a solution of stearic acid in methanol (8.8.times.10.sup.-3 mol dm.sup.-3)
on the coated surface of the glass at 2000 rpm for 1 minute. Infra red spectra were
measured in transmission, and the peak height of the peak corresponding to the C--H
stretches (at about 2700 to 3000 cm.sup.-1) of the stearic acid film was measured and
the corresponding peak area determined from a calibration curve of peak area against
peak height. The coated side of the glass was illuminated with a UVA-351 lamp
(obtained from the Q-Panel Co., Cleveland, Ohio, USA) having a peak wavelength of
351 nm and an intensity at the surface of the coated glass of approximately 32
W/m.sup.2. The photocatalytic activity is expressed in this specification either as the
rate of decrease of the area of the IR peaks (in units of cm.sup.-1 min.sup.-1) or as
t.sub.90% (in units of min) which is the time of UV exposure taken to reduce the peak
height (absorption) of a peak in the wavelength area down to 10% of its initial value.
The static water contact angle of the coated glasses was determined by measuring the
diameter of a water droplet (volume in the range 1 to 5 .mu.l) placed on the surface of
the coated glass after irradiation of the coated glass using the UVA 351 lamp for about
2 hours (or as otherwise specified).
EXAMPLES 1-15
A ribbon of 1 mm thick soda lime float glass advancing at a lehr speed of 300 m/hour
was coated with a two-layer coating as the ribbon advanced over the float bath at a
position where the glass temperature was in the range of about 650.degree. C. to about
670.degree. C. The float bath atmosphere comprised a flowing gaseous mixture of
nitrogen and 9% hydrogen at a bath pressure of approximately 0.15 mbar.
Layer 1 (the first layer to be deposited on the glass) was a layer of silicon oxide.
Layer 1 was deposited by causing a gaseous mixture of monosilane (SiH.sub.4, 60
ml/min), oxygen (120 ml/min), ethylene (360 ml/min) and nitrogen (8 litres/min) to
contact and flow parallel to the glass surface in the direction of movement of the glass
using coating apparatus as described in GB patent specification 1 507 966 (referring
in particular to FIG. 2 and the corresponding description on page 3 line 73 to page 4
line 75) with a path of travel of the gaseous mixture over the glass surface of
approximately 0.15 m. Extraction was at approximately 0.9 to 1.2 mbar. The glass
ribbon was coated across a width of approximately 10 cm at a point where its
temperature was approximately 670.degree. C. The thickness of the silica layer was
about 20 to 25 m.
Layer 2 (the second layer to be deposited) was a layer of titanium dioxide. Layer 2
was deposited by combining separate gas streams comprising titanium tetrachloride in
flowing nitrogen carrier gas, ethyl acetate in flowing nitrogen carrier gas and a bulk
flow of nitrogen of 8 l/min (flow rate measured at 20 psi) into a gaseous mixture and
then delivering (through lines maintained at about 250.degree. C.) the gaseous
mixture to coating apparatus consisting of an oil cooled dual flow coater. The pressure
of the nitrogen carrier and bulk nitrogen gases was approximately 20 pounds per
square inch. The gaseous mixture contacted and flowed parallel to the glass surface
both upstream and downstream along the glass ribbon. The path of travel of the
gaseous mixture downstream was about 0.15 m and upstream was about 0.15 m with
extraction of about 0.15 mbar. Titanium tetrachloride and ethyl acetate were entrained
in separate streams of flowing nitrogen carrier gas by passing nitrogen through
bubblers containing either titanium tetrachloride or ethyl acetate. The flow rates of the
nitrogen carrier gases are described in Table 1 (the flow rates were measured at 20
psi). The titanium tetrachloride bubbler was maintained at a temperature of 69.degree.
C. and the ethyl acetate bubbler was maintained at a temperature of 42.degree. C. The
estimated flow rates of entrained titanium tetrachloride and entrained ethyl acetate are
also described in Table 1 for each of the Examples 1 to 15.
The properties of the two-layer coatings were measured. Values of the thickness of
layer 2 (the titanium oxide layer), and values of the visible reflection measured on the
coated side, L* and haze of the coated glasses are described in Table 2 for the
Examples 1-15. The haze of each coated glass was below 0.2%.
The photocatalytic activity and static water contact angle of the coated glasses were
determined. The initial peak height and initial peak area of the IR peaks
corresponding to the stearic acid C--H stretches, the photocatalytic activity, the static
water contact angle and t.sub.90% for the Examples 1-15 are described in Table 3.
The thickness of the titanium oxide layer, surprisingly has little effect on
photocatalytic activity.
EXAMPLES 16-19
Examples 16-19 were conducted under the same conditions as Examples 1-15 except
that the bath pressure was approximately 0.11 mbar, extraction for deposition of the
silica undercoat (layer 1) was approximately 0.7 mbar, the titanium tetrachloride
bubbler was maintained at a temperature of approximately 100.degree. C., the ethyl
acetate bubbler was maintained at a temperature of approximately 45.degree. C. and
the delivery lines were maintained at a temperature of approximately 220.degree. C.
The flow rates of nitrogen carrier gas, and the estimated flow rates of entrained
titanium tetrachloride and entrained ethyl acetate are disclosed for each of the
examples 16-19 in Table 1.
Values of the estimated thickness of layer 2 (the titanium oxide layer), and values of
visible reflection measured on the coated side, L* and haze of the coated glasses are
described in Table 2 for each of the Examples 16-19.
The initial peak height and initial peak area of the IR peaks corresponding to the
stearic acid C--H stretches, the photocatalytic activity, t.sub.90% and the static water
contact angle and for each of the Examples 16-19 are described in Table 3.
The photocatalytic activity of the Examples 16-19 was not substantially greater than
that of the Examples 1-15 despite the thicker titanium oxide (and hence more
reflective) coatings.
TABLE 1
Nitrogen Carrier Gas
Example
Flow Rates to Bubblers
(l/min, measured at 20 psi) TiCl.sub.4 Ethyl Acetate
Ethyl Acetate flow rate
flow rate
TiCl.sub.4 Bubbler
Bubbler
(l/min)
(l/min)
1
2
0.16
0.12
1
0.3
0.032
0.024
0.46
0.14
3
4
5
6
7
8
9
10
11
12
0.12
0.08
0.12
0.12
0.08
0.08
0.04
0.04
0.04
0.16
0.45
0.2
0.15
0.75
0.3
0.5
0.1
0.15
0.25
0.1
0.024
0.016
0.024
0.024
0.016
0.016
0.008
0.008
0.008
0.032
0.21
0.09
0.07
0.35
0.14
0.23
0.05
0.07
0.12
0.05
13
14
15
16
17
18
19
0.08
0.16
0.16
0.1
0.08
0.06
0.04
0.1
0.4
0.2
0.5
0.4
0.3
0.2
0.016
0.032
0.032
0.088
0.070
0.053
0.035
0.05
0.19
0.09
0.27
0.22
0.16
0.11
TABLE 2
Example
1
Thickness of Visible reflection
titanium oxide of coated glass
L* value of
Haze
layer (nm)
(%)
coated glass (%) (%)
15
14.1
44
0.12
2
14.3
13.9
44
3
14.2
13.2
43
4
11.3
11.4
40
5
12.1
12.1
41
6
11.0
a
a
7
8
a
a
8
7.2
9.7
37
9
6.1
9.1
36
10
5.6
9
36
11
4.6
8.7
35
12
13
15.6
16.0
15.4
a
46
a
14
17.5
16.2
47
15
16
17
20.3
a
ca 68
19.5
28.4
29.1
51
47.8
58.4
0.07
0.12
0.08
0.08
0.07
0.11
0.04
0.05
0.07
0.06
0.1
0.13
0.14
0.37
0.1
0.3
18
ca 32
25.9
55.6
19
ca 27
a not measured
20.5
50.2
0.24
0.2
TABLE 3
IR Peaks corresponding to
stearic acid film C-H
stretches (2700-3000 cm.sup.-1)
PhotoStatic
Initial Peak
Initial
catalytic
Water
cm.sup.-1
Height
(arbitrary
Peak
Area
units)
(cm.sup.-1)
Activity
Contact
(.times.10.sup.-2
Angle
t.sub.90%
Example
min.sup.-1) (.degree.)
(min)
1
2
3
4
0.030
0.0331
0.0311
0.0324
1.04
1.15
1.08
1.13
9.4
10.4
12.2
6.8
17
15
13
14
.+-.
.+-.
.+-.
.+-.
5
1
2
1
10
10
8
15
5
6
7
8
9
10
11
12
13
0.0287
0.028
0.0343
0.0289
0.0289
0.0278
0.0344
0.0291
0.0289
1.00
0.98
1.20
1.03
1.01
0.97
1.20
1.02
1.01
8.2
8.8
10.8
6.6
6.5
6.2
5.4
10.2
9.1
16
15
15
16
14
18
18
12
14
.+-.
.+-.
.+-.
.+-.
.+-.
.+-.
.+-.
.+-.
.+-.
3
1
1
1
2
2
1
1
2
11
10
10
14
14
14
20
9
10
14
15
16
17
18
19
0.0269
0.0331
0.0227
0.026
0.0225
0.0258
0.94
1.15
0.79
0.91
0.79
0.90
9.4
8.7
17.8
10.2
10.1
10.1
15 .+-. 2
15 .+-. 2
12
12
13
16
9
12
4
8
7
8
EXAMPLES 20-27
The Examples 20-27 were conducted under the same conditions as Examples 1-15
except that layer 2 was deposited from a gaseous mixture comprising titanium
tetraethoxide entrained in nitrogen carrier gas by passing the carrier gas through a
bubbler containing titanium tetraethoxide maintained at a temperature of 170.degree.
C. The flow rates of nitrogen carrier gas (measured at 20 psi) and titanium
tetraethoxide are described in Table 4 for each of the Examples 20-27. The flow rate
of bulk nitrogen gas was 8.5 l/min (measured at 20 psi).
The properties of the two-layer coatings were measured. Values of the thickness of
layer 2 (the titanium oxide layer), and values of the visible reflection measured on the
coated side and haze of the coated glasses are described in Table 5 for the Examples
20-27. The haze of each coated glass was below 0.7%.
The photocatalytic activity and static water contact angle of the coated glasses were
determined. The initial peak height and initial peak area of the IR peaks
corresponding to the stearic acid C--H stretches, the photocatalytic activity and
t.sub.90%, and the static water contact angle for each of the Examples 20-27 are
described in Table 6.
EXAMPLES 28 AND 29
The Examples 28 and 29 were conducted under the same conditions as Examples
20-27 except that the titanium tetraethoxide bubbler was maintained at a temperature
of 168.degree. C. and the bath pressure was 0.11 mbar. Data relating to Examples
28-29 equivalent to data for Examples 20-27 are described in Tables 4, 5 and 6.
TABLE 4
Nitrogen Carrier Gas Flow Rates to
Example
20
21
22
23
24
25
Titanium tetraethoxide bubbler Titanium ethoxide flow
(l/min, measured at 20 psi)
rate (l/min)
0.25
0.014
0.15
0.008
0.2
0.011
0.25
0.014
0.3
0.017
0.35
0.019
26
0.2
0.011
27
28
29
0.1
0.6
0.4
0.006
0.030
0.020
TABLE 5
Example
20
21
Thickness of titanium Visible reflection of Haze
oxide layer (nm)
coated glass (%)
(%)
13
a
0.4
13
a
0.29
22
23
24
a
25
26
27
28
29
Not measured
16
18
24
15.7
a
a
0.29
0.28
a
26
9.9
4.7
38.3
31.9
a
10.9
8.8
35.2
28.4
0.61
0.19
0.29
0.29
0.22
TABLE 6
IR Peaks corresponding to
stearic acid film C-H
stretches (2700-3000 cm.sup.-1)
PhotoStatic
Initial Peak
Initial
catalytic
Water
Height
Peak
Activity
Contact
(arbitrary
Area
(.times.10.sup.-2
cm.sup.-1
Angle
t.sub.90%
Example
units)
(cm.sup.-1)
0.027
0.031
0.024
0.030
0.029
0.953
1.095
0.838
1.029
1.015
min.sup.-1) (.degree.)
(min)
20
21
22
23
24
5.7
5.7
3.6
7.1
7
19 .+-.
a
15 .+-.
11 .+-.
17 .+-.
5
15
17
2
3
3
21
13
13
25
a
0.031
1.071
7.4
13 .+-. 4
13
26
0.031
27
0.029
28
0.021
29
0.024
Not measured
1.085
0.998
0.733
0.848
4.4
3.2
3.6
3.3
21 .+-. 3 22
16 .+-. 5 28
13
18
14
23
EXAMPLES 30-42
In Examples 30 to 42, two-layer coatings were applied by on line CVD to a float glass
ribbon across its full width of approximately 132 inches (3.35 m) in the float bath
during the float glass production process. The apparatus used to deposit the coating is
illustrated in FIG. 2. The float bath atmosphere comprised nitrogen and 2% by volume
hydrogen. Bath pressure was 0.15 mbar.
The two layer coating consisted of a silicon oxide layer deposited first on the float
glass ribbon and titanium oxide layer deposited on to the silicon oxide layer. The
precursor chemistry of the gaseous mixtures used to deposit the coating was the same
as that used in Examples 1-15. The temperature of deposition of the layers was varied
by using different coaters 27, 28, 29 or 30 (referring to FIG. 2). Coater 27 located
nearest the hearth being hottest and coater 30 located nearest the lehr being coolest. In
Examples 30-33 and 42 two coaters (28 and 29 in Examples 30-33 and coaters 27 and
28 in Example 42) were used to deposit the silicon oxide coating. The benefit of using
two coaters to deposit the silicon oxide layer is that longer production run times are
possible.
The gaseous mixture used to deposit the silicon oxide layer for Examples 30 to 41
consisted of the following gases at the following flow rates: helium (250 l/min),
nitrogen (285 l/min), monosilane (2.5 l/min), ethylene (15 l/min) and oxygen (10
l/min). For Example 42, the same gases and flow rates were used except for
monosilane (2.3 l/min), ethylene (13.8 l/min) and oxygen (9.2 l/min). Where two
coaters were used to deposit the silicon oxide layer in Examples 30 to 42, the above
flow rates were used for each coater.
In Examples 30-42 the deposition temperatures (i.e. the temperature of the float glass
ribbon under the coater corresponding to each of the coaters 27-30) was as indicated
in Table 7. The temperatures in Table 7 have an uncertainty of about .+-.50.degree. F.
(.+-.28.degree. C.). The extraction for each coater was at approximately 2 mbar.
TABLE 7
Coater
27
28
29
30
Approx. Temperature of Glass Ribbon
1330.degree. F. (721.degree. C.)
1275.degree. F. (690.degree. C.)
1250.degree. F. (677.degree. C.)
1150.degree. F. (621.degree. C.)
Titanium tetrachloride (TiCl.sub.4) and ethyl acetate were entrained in separate
nitrogen/helium carrier gas streams. For the evaporation of TiCl.sub.4 a thin film
evaporator was used. The liquid TiCl.sub.4 was held in a pressurised container (head
pressure approx 5 psi). This was used to deliver the liquid to a metering pump and
Coriolis force flow measurement system. The metered flow of the precursor was then
fed into a thin film evaporator at a temperature of 110.degree. F. (43.degree. C.). The
TiCl.sub.4 was then entrained in the carrier gas (helium) and delivered to the mixing
point down lines held at 250.degree. F. (121.degree. C.). The ethyl acetate was
delivered in a similar way. The liquid ethyl acetate was held in a pressurised container
(head pressure approx 5 psi). This was used to deliver the liquid to a metering pump
and Coriolis force flow measurement system. The metered flow of the precursor was
then fed into a thin film evaporator at a temperature of 268.degree. F. (131.degree. C.).
The evaporated ethyl acetate was then entrained in the carrier gas (helium/nitrogen
mixture) and delivered to the mixing point down lines held at approximately
250.degree. F. (121.degree. C.).
The TiCl.sub.4 and ethyl acetate gas streams were combined to form the gaseous
mixture used to deposit the titanium oxide layer. This mixing point was just prior to
the coater.
The line speed of the float glass ribbon, the temperature of deposition of the silicon
oxide and temperature of deposition of the titanium oxide layers and the flow rates of
the He/N.sub.2 bulk carrier gas and the flow rate of TiCl.sub.4 and ethyl acetate are
described for Examples 30-42 in Table 8.
The coated float glass ribbon was cooled and cut and the optical properties and
photocatalytic activity of samples determined. Table 9 describes the haze, optical
properties in transmission and reflection (visible percent transmission/reflection and
colour co-ordinates using the LAB system) of the samples. The coated glasses were
subjected to abrasion testing in accordance with BS EN 1096, in which a sample of
size 300 mm.times.300 mm is fixed rigidly, at the four corners, to the test bed
ensuring that no movement of the sample is possible. An unused felt pad cut to the
dimensions stated in the standard (BS EN 1096 Part 2 (1999)) is then mounted in the
test finger and the finger lowered to the glass surface. A load pressure on the test
finger of 4N is then set and the test started. The finger is allowed to reciprocate across
the sample for 500 strokes at a speed of 60 strokes/min .+-.6 strokes/min. Upon
completion of this abrasion the sample is removed and inspected optically and in
terms of photocatalytic activity. The sample is deemed to have passed the test if the
abrasion results in a change in transmission of no more than .+-.5% when measured at
550 nm and the coated substrate remains photocatalytically active which means that,
after the test irradiation by UV light for 2 hours reduces the static water contact angle
to below 15.degree..
The glasses were also subjected to a humidity cycling test in which the coating is
subjected to a temperature cycle of 35.degree. C. to 75.degree. C. to 35.degree. C. in 4
hours at near 100% relative humidity.
The static water contact angle of the coated glasses as produced and after 130 minutes
of UV irradiation (UVA 351 mm lamp at approximately 32 W/m.sup.2) and after 300,
500 and/or 1000 strokes of the European standard abrasion test described in Table 10.
The contact angle of the abraded samples was determined after irradiation for 2 hours.
The samples deposited at the higher temperatures of 1330-1250.degree. F. (721.degree.
C. to 677.degree. C.) were photocatalytically active even after 1000 European
standard abrasion strokes or after 200 humidity cycles. The photocatalytic activity in
terms of t.sub.90% of the coated glasses as produced and after 300, 500 and/or 1000
strokes of the European standard abrasion test and after 200 humidity testing cycles
are described in Table 11. In Table 11, the term Active indicates that the coated glasses
were photocatalytically active but that t.sub.90% was not determined.
TABLE
8
Titanium
Oxide Layer
Lineof
Flow
Silica layer
Flow Rates
Rates of Precursors
Speed
Deposition
Deposition
Carrier
Gases
TiCl.sub.4 Ethyl Acetate
Example (m/min) Temperature/.degree. C. Temperature/.degree.
C. He L/min
N.sub.2 L/min cc/min
cc/min
30
10.9
690 & 677
621
300
300
6.3
16.3
31
10.9
690 & 677
621
300
300
6.3
32
16.3
10.9
690 & 677
621
300
6.3
33
16.3
10.9
690 & 677
621
300
6.3
34
6
16.3
10.9
690
621
300
10.9
690
621
300
10.9
690
621
300
37
10.9
690
677
300
5.5
38
14.7
10.9
690
677
300
5.5
39
14.7
10.9
690
677
300
5.5
14.7
300
300
300
16
300
35
6
16
300
36
6
16
300
300
300
40
10.9
690
677
300
5.5
41
4
14.7
6.5
721
690
300
721 & 690
677
300
300
300
10.7
42
12.1
300
9.5
25.4
Example
TABLE 9
Film Side Reflection
R (%)
L*
a
b
30
31
32
33
34
35
36
Transmission
T (%) L*
a
Haze
b
(%)
14.2
14.6
14.6
13.8
13.6
13.8
12.9
44.5
45.1
45.1
44.0
43.7
43.9
42.6
0.3 -10.3 84.3 93.6
0.3 -10.4 84.5 93.7
0.3 -10.5 84.3 93.6
0.3 -9.8 85.5 94.1
0.1 -8.7 84.8 93.8
0.1 -8.8 85.4 94.1
0.1 -8.2 85.8 94.2
-1.2
-1.1
-1.1
-1.1
-1.1
-1.1
-1.1
3.6
3.4
3.6
2.9
2.7
2.6
2.5
0.11
0.30
0.12
0.15
0.12
0.11
0.14
37
12.6
38
11.9
39
11.5
40
11.6
41
a
42
14
a Not Measured
42.2
41.0
40.4
40.6
a
44.3
0.1
0.1
0.0
0.0
a
0.1
-1.1
-1.1
-1.1
-1.1
a
-1.1
2.3
1.7
1.8
1.8
a
3.1
0.08
0.07
0.10
0.08
a
0.14
Example
30
31
32
-7.9
-6.9
-6.5
-6.6
a
-9.9
86.1
87.1
87.2
86.9
a
84.8
94.4
94.8
94.8
94.7
a
93.8
TABLE 10
Static Water Contact Angle (.degree.) after
Number of Abrasion Strokes
0 (after
0
irradiation 130 min UV) 300
500
1000
2.3
3.3
failed
2.0
3.2
failed
a
a
failed
33
2.0
34
a
35
2.0
36
2.1
37
2.2
38
2.0
39
1.9
40
2.2
41
7.8
42
4.7-5.3
a Not measured
3.2
failed
a
3.2
3.4
3.3
3.1
3.1
3.2
7.8
4.7-5.3
failed
failed
failed
<15
<15
<15
<15
10.1
5.6-9.8
TABLE 11
Example
30
31
32
33
34
35
36
37
38
39
40
41
42
t.sub.90% (min) after
Number of Abrasion Strokes
0
300
500
1000
7.5 failed
18.5 failed
8.5 failed
8
failed
21
failed
4
failed
8.5 failed
15.5
Ca. 2160
18.5
Ca. 2160
17
Ca. 2160
18.5
Ca. 2160
a
45
ca. 2160
2800
t.sub.90% (min) after
200 Humidity Cycles
failed
failed
failed
failed
failed
failed
failed
Active
Active
Active
Active
Active
Active
a Not measured
(3
United States Patent
Hayakawa ,
et al.
of
4)
6,830,785
December 14, 2004
Method for photocatalytically rendering a surface of a substrate
superhydrophilic, a substrate with a superhydrophilic photocatalytic surface,
and method of making thereof
Abstract
The surface of a substrate is coated with an abrasion-resistant photocatalytic coating
comprised of a semiconductor photocatalyst. upon irradiation by a light having a
wavelength of an energy higher than the bandgap energy of the photocatalyst, water is
chemisorbed onto the surface in the form of hydroxyl groups (OH.sup.-) whereby the
surface of the photocatalytic coating is rendered highly hydrophilic. In certain
embodiments, the surface of a mirror, lens, or windowpane is coated with the
photocatalytic coating to exhibit a high degree of antifogging function. In another
embodiment, an article or product coated with the photocatalytic coating is disposed
outdoors and the highly hydrophilic surface thereof is self-cleaned as it is subjected to
rainfall. In a still another embodiment, an article is coated with the photocatalytic coating
and, when the article is soaked in, rinsed by or wetted with water, fatty dirt and
contaminants are readily released without resort to a detergent.
Inventors: Hayakawa; Makoto (Kita-kyushu, JP); Kojima; Eiichi (Kita-kyushu,
JP); Norimoto; Keiichiro (Kita-kyushu, JP); Machida; Mitsuyoshi
(Kita-kyushu, JP); Kitamura; Atsushi (Kita-kyushu, JP); Watanabe;
Toshiya (Kita-kyushu, JP); Chikuni; Makoto (Kita-kyushu, JP);
Fujishima; Akira (Kawasaki, JP); Hashimoto; Kazuhito (Yokohama, JP)
Assignee: Toto Ltd. (Fukuoka-ken, JP)
Appl. No.: 374344
Filed:
August 13, 1999
Foreign Application Priority Data
Mar 20, 1995[JP]
7/099425
Apr 06, 1995[JP]
7/117600
Jun 14, 1995[JP]
7/182019
Jun 14, 1995[JP]
7/182020
Jul 08, 1995[JP]
7/205019
Nov 09, 1995[JP]
7/326167
Dec 22, 1995[JP]
7/354649
427/553; 134/1
Current U.S. Class:
B05D 003/06; B08B 003/00; B08B 007/00; B08B
017/00
Intern'l Class:
427/553,554,555,556,581 134/1
Field of Search:
References Cited [Referenced By]
U.S. Patent Documents
3347816
Oct., 1967
Krauss et al.
3451833
Jun., 1969
Bonitz et al.
3640712
Feb., 1972
Field et al.
3871881
Mar., 1975
Mikelsons.
3976497
Aug., 1976
Clark.
4661372
Apr., 1987
Mance
4954465
Sep., 1990
Kawashima et al.
4955208
Sep., 1990
Kawashima et al.
5547823
Aug., 1996
Murasawa et al.
5593737
Jan., 1997
Meinzer et al.
5594585
Jan., 1997
Komatsu.
5595813
Jan., 1997
Ogawa et al.
5616532
Apr., 1997
Heller et al.
5643436
Jul., 1997
Ogawa et al.
5755867
May., 1998
Chikuni et al.
5759251
Jun., 1998
Nakamura et al.
106/286.
5854708
Dec., 1998
Komatsu et al.
359/507.
5859086
Jan., 1999
Freund et al.
427/553.
5874125
Feb., 1999
Kanoh et al.
427/553.
5989787
Nov., 1999
Kanoh et al.
427/553.
6037289
Mar., 2000
Chopin et al.
427/169.
6045903
Apr., 2000
Seino et al.
427/165.
6055085
Apr., 2000
Nakashima et al.
359/241.
6071606
Jun., 2000
Yamazaki et al.
428/325.
427/553.
427/553.
6090489
Jul., 2000
Hayakawa et al.
427/301.
6103363
Aug., 2000
Boire et al.
427/164.
6165256
Dec., 2000
Hayakawa et al.
6165619
Dec., 2000
Ikenaga et al.
427/387.
6193378
Feb., 2001
Tonar et al.
359/603.
6194346
Feb., 2001
Tada et al.
502/224.
6335061
Jan., 2002
Kanamori et al.
427/515.
6637336
Oct., 2003
Suda et al.
101/465.
6673433
Jan., 2004
Saeki et al.
428/323.
6679978
Jan., 2004
Johnson et al.
427/585.
6680135
Jan., 2004
Boire et al.
428/702.
2003/0003304
Jan., 2003
Ohtsu
428/412.
2003/0027000
Feb., 2003
Greenberg et al.
427/255.
2003/0181329
Sep., 2003
Tanaka et al.
502/338.
2003/0207028
Nov., 2003
Boire et al.
427/226.
2003/0213391
Nov., 2003
Suda et al.
101/463.
2003/0220194
Nov., 2003
Sakatani et al.
502/350.
2004/0009361
Jan., 2004
Street et al.
428/482.
2004/0028911
Feb., 2004
Hurst et al.
427/255.
Foreign Patent Documents
0433915
Jun., 1991
EP.
0590477
Apr., 1994
EP.
1022588
Jul., 2000
EP.
149281/78
Dec., 1978
JP.
61-83106
Apr., 1986
JP.
61-91042
May., 1986
JP.
63-100042
May., 1988
JP.
1218635
Aug., 1989
JP.
1-218635
Aug., 1989
JP.
1288321
Nov., 1989
JP.
3101926
Apr., 1991
JP.
4-174679
Jun., 1992
JP.
5-302173
Nov., 1993
JP.
106/13.
6298520
Oct., 1994
JP.
6315614
Nov., 1994
JP.
7051646
Feb., 1995
JP.
7113272
May., 1995
JP.
8119673
May., 1995
JP.
7171408
Jul., 1995
JP.
60-221702
Nov., 1995
JP.
8164334
Jun., 1996
JP.
8313705
Nov., 1996
JP.
9173783
Jul., 1997
JP.
9-173783
Jul., 1997
JP.
9-224793
Sep., 1997
JP.
9-227157
Sep., 1997
JP.
9227157
Sep., 1997
JP.
9-227158
Sep., 1997
JP.
9227158
Sep., 1997
JP.
9235140
Sep., 1997
JP.
9-235140
Sep., 1997
JP.
9241037
Sep., 1997
JP.
9-241037
Sep., 1997
JP.
WO9511751
May., 1995
WO.
Other References
Derwent Abstract of CN 1421496 A, Jun. 4, 2003.*
Highly Transparent and Photoactive TIO2 Thin Film Coated on Glass
Substrate, S. Fukayama 1996 with Translation (date & month, not given or
not Translated).
Highly Transparent and Photoactive TIO2 Thin Film Coated on Glass
Substrate, S. Fukayama, Mar. 20, 1995, The Electrochemical Society of
Japan with Translation.
Preparing Catalyst Using Metal Alkoxide (no date, no author) (In Translation
or Apparent) with Translation partial.
"Highly Transparent and Photoactive TIo2 Thin Film Coated on Glass
Substrates" from the 187th Electrochemical Society meeting, Reno 21-26,
May 1994 Extended Abstracts 95-1 (for abstract 735 p1102) Fukayama S, et
al.
Derwent Abstract (008031514) of Japanese Pat. # JP 1218635 A, Published
Only 1.sup.st Page Supplied and incomplete, Aug. 31, 1989, Hitach Ltd.
Derwent Abstract (008117612) of Japanese Pat. #JP1288321 A, Pub. Nov.
20, 1989, to Matsushita Elec. Ind. Co.
(Abstracts of Japan (70 M 1138)) Japanese Abstract #3-101926 A, Pub. Apr.
26, 1991, "Demisting Plastic", to Noguchi.
Abstract of Japanese JP6278241 A, Pub. Oct. 4, 1994 "Building Material",
Hasegawa et al.
Transparent, Photocatalytic TiO2 Film Formed on Glass, Japan Chemical
Week, p 4, Dec. 15, 1994.
Primary Examiner: Padgett; Marianne
Attorney, Agent or Firm: Jones Day
Parent Case Text
This application is a continuation of application Ser. No. 08/933,886 filed Sep. 19,
1997, now U.S. Pat. No. 6,013,372, which is a continuation-in-part of International
application Ser. No. PCT/JP96/00733 filed Mar. 21, 1996 and which designated the
United States.
Claims
What is claimed is:
1. A method of preventing or reducing fogging of a surface of a composite when
subjected to humid conditions, comprising:
providing a composite with a surface, said composite comprising a substrate and a
photocatalytic surface layer, said photocatalytic surface layer comprising a
photocatalyst;
subjecting the photocatalyst to photoexcitation by exposing the composite to sunlight
to render the surface of the composite hydrophilic, wherein, after said photoexcitation,
the surface of the composite has a water wettability of less than 10.degree. in terms of
the contact angle with water; and
subjecting the composite to humidity that is sufficient to induce fogging of said
substrate if said photocatalytic surface layer were absent.
2. The method of claim 1, wherein, after said photoexcitation, the surface of the
composite has a water wettability of less than 5.degree. in terms of the contact angle
with water.
3. The method of claim 1, wherein, after said photoexcitation, the surface of the
composite has a water wettability of about 0.degree. in terms of the contact angle with
water.
4. The method of claim 1, wherein said photocatalyst is selected from the group
consisting of TiO.sub.2, ZnO, SnO.sub.2, SrTiO.sub.3, WO.sub.3, Bi.sub.2 O.sub.3
and Fe.sub.2 O.sub.3.
5. The method of claim 4, wherein said photocatalytic surface layer further comprises
a metal selected from the group consisting of Ag, Cu and Zn.
6. The method of claim 4, wherein said photocatalytic surface layer ether comprises a
metal selected from the group consisting of Pt, Pd, Rh, Ru, Os and Ir.
7. The method of claim 1, wherein said substrate comprises glass.
8. The method of claim 1, wherein, said substrate comprises glass containing alkaline
network modifier ions, and wherein said composite further comprises a film disposed
between said substrate and said photocatalytic surface layer, said film preventing ions
from diffusing from said substrate into said photocatalytic surface layer.
9. The method of claim 8, wherein said film comprises silica.
10. The method of claim 1, wherein said photocatalytic surface layer further
comprises silica or silicone.
11. The method of claim 1, wherein said photocatalytic surface layer consists
essentially of said photocatalyst.
12. A method for maintaining a surface of a composite in a clean state when subjected
to dirt in air and precipitation, comprising:
providing a composite with a surface, said composite comprising a substrate and a
photocatalytic surface layer, said photocatalytic surface layer comprising a
photocatalyst;
subjecting the photocatalyst to photoexcitation by exposing the composite to sunlight
to render the surface of the composite hydrophilic, wherein, after said photoexcitation,
the surface of the composite has a water wettability of less than about 20.degree. in
terms of the contact angle with water;
subjecting said composite to dirt in air or precipitation; and
washing away the dirt on the surface of the composite by occasional contact with
water.
13. The method of claim 12, wherein, after said photoexcitation, the surface of the
composite has a water wettability of less than 10.degree. in terms of the contact angle
with water.
14. The method of claim 12, wherein, after said photoexcitation, the surface of the
composite has a water wettability of less than 5.degree. in terms of the contact angle
with water.
15. The method of claim 12, wherein, after said photoexcitation, the surface of the
composite has a water wettability of about 0.degree. in terms of the contact angle with
water.
16. The method of claim 12, wherein said photocatalyst is selected from the group
consisting of TiO.sub.2, ZnO, SnO.sub.2, SrTiO.sub.3, WO.sub.3, Bi2O.sub.3 and
Fe.sub.2 O.sub.3.
17. The method of claim 16, wherein said photocatalytic surface layer further
comprises a metal selected from group consisting of Ag, Cu and Zn.
18. The method of claim 16, wherein said photocatalytic surface layer further
comprises a metal selected from the group consisting of Pt, Pd, Rh, Ru, Os and Ir.
19. The method of claim 12, wherein said substrate comprises glass containing
alkaline network modifier ions, and wherein said composite further comprises a film
disposed between said substrate and said photocatalytic surface layer, said film
preventing ions from diffusing from said substrate and photocatalytic surface layer.
20. The method of claim 19, wherein said film comprises silica.
21. The method of claim 12, wherein said substrate is a tile, a portion of the body of a
motor vehicle, an inner panel of a building, or an outer panel of a building.
22. The method of claim 12, wherein said photocatalytic surface layer further
comprises silica.
23. The method of claim 12, wherein said photocatalytic surface layer consists
essentially of said photocatalyst.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates broadly to the art of rendering and maintaining a surface
of a substrate highly hydrophilic. More particularly, the present invention relates to
the antifogging art wherein the surface of a transparent substrate such as a mirror, lens
and sheet glass is made highly hydrophilic to thereby prevent fogging of the substrate
or formation of water droplets. This invention is also concerned with the art wherein
the surface of a building, windowpane, machinery or article is rendered highly
hydrophilic in order to prevent fouling of, to permit self-cleaning of or to facilitate
cleaning of the surface. This invention also relates to a hydrophilifiable member
having a surface layer which is capable of having an extremely small contact angle
with water, a method for rendering the member hydrophilic, a method for forming a
hydrophilifiable surface layer, and a coating composition for forming a
hydrophilifiable surface layer.
2. Description of the Prior Art
It is often experienced that, in the cold seasons, windshields and window-glasses of
automobiles and other vehicles, windowpanes of buildings, lenses of eyeglasses, and
cover glasses of various instruments are fogged by moisture condensate. Similarly, in
a bathroom or lavatory, it is often encountered that mirrors and eyeglass lenses are
fogged by steam.
Fogging of the surface of an article results from the fact that, when the surface is held
at a temperature lower than the dew point of the ambient atmosphere, condensation of
moisture in the ambient air takes place to form moisture condensate at the surface.
If the condensate particles are sufficiently fine and small so that the diameter thereof
is on the order of one half of the wavelength of the visible light, the particles cause
scattering of light whereby window-glasses and mirrors become apparently opaque
thereby giving rise to a loss of visibility.
When condensation of moisture further proceeds so that fine condensate particles are
merged together to grow into discrete larger droplets, the refraction of light taking
place at the interface between the droplets and the surface and between the droplets
and the ambient air causes the surface to be blurred, dimmed, mottled, or clouded. As
a result, an image viewed through a transparent article such as sheet glass may
become distorted, or the reflected image in a mirror may be disturbed.
Similarly, when windshields and window-glasses of vehicles, windowpanes of
buildings, rearview mirrors of vehicles, lenses of eyeglasses, or shields of masks or
helmets are subjected to rain or water splash so that discrete water droplets are
adhered to the surface, their surface is blurred, dimmed, mottled, or clouded, resulting
in the loss of visibility.
The term "antifogging" as used herein and in the appended claims is intended to mean
broadly the art of preventing or minimizing occurrence of optical trouble resulting
from fogging, growth of condensate droplets or adherent water droplets mentioned
above.
The antifogging art can significantly affect safety and efficiency in a variety of setting.
For example, the safety of vehicles and traffic can be undermined if the windshields,
window-glasses or rearview mirrors of vehicles are fogged or blurred. Fogging of
endoscopic lenses and dental mouth mirrors may hinder proper and accurate diagnosis,
operation and treatment. If cover glasses of measuring instruments are fogged, a
reading of data will become difficult.
The windshields of automobiles and other vehicles are normally provided with
windshield wipers, defrosting devices and heaters so as to avoid visibility problems,
which arise particularly in the cold seasons and under rainy conditions. However, it is
not commercially feasible to install this equipment on the side windows of a vehicle,
or on the rearview mirrors arranged outside of the vehicle. similarly, it is difficult, if
possible at all, to mount such antifogging equipment on windowpanes of buildings,
lenses of eyeglasses and endoscopes, dental mouth mirrors, shields of masks and
helmets, or cover glasses of measuring instruments.
As is well-known, a simple and convenient antifogging method conventionally used
in the art is to apply onto a surface an antifogging composition containing either a
hydrophilic compound such as polyethylene glycol or a hydrophobic or
water-repellent compound such as silicone. However, the disadvantage of this method
is that the antifogging coating thus formed is only temporary in nature and is readily
removed when rubbed or washed with water so that its effectiveness is prematurely
lost.
Japanese Utility Model Kokai Publication No. 3-129357 (Mitsubishi Rayon) discloses
an antifogging method for a mirror wherein the surface of a substrate is provided with
a polymer layer and the layer is subjected to irradiation by ultraviolet light, followed
by treatment with an aqueous alkaline solution to thereby form acid radicals at a high
density whereby the surface of the polymer layer is rendered hydrophilic. Again,
however, it is believed that, according to this method, the hydrophilic property of the
surface is degraded as time elapses because of adherent contaminants so that the
antifogging function is lost over time.
Japanese Utility Model Kokai Publication No. 5-68006(Stanley Electric) discloses an
antifogging film made of a graftcopolymer of an acrylic monomer having hydrophilic
groups and a monomer having hydrophobic groups. The graftcopolymer is described
as having a contact angle with water of about 50.degree.. It is therefore believed that
this antifogging film does not exhibit a sufficient antifogging capability.
Isao Kaetsu "Antifogging Coating Techniques for Glass", Modern Coating Techniques,
pages 237-249, published by Sogo Gijutsu Center (1986), describes various
antifogging techniques used in the prior art. The author Mr. Kaetsu nevertheless
reports that the prior art antifogging techniques, which consist of rendering a surface
hydrophilic, suffer from significant problems which must be overcome in reducing
them to practice, and, further reports that the conventional antifogging coating
techniques seemingly come up against a barrier.
Accordingly, an object of the invention is to provide an antifogging method which is
capable of realizing a high degree of visibility in a transparent substrate such as a
mirror, lens or glass.
Another object of the invention is to provide an antifogging method wherein the
surface of a transparent substrate such as a mirror, lens or glass is maintained highly
hydrophilic for an extended period of time.
Still another object of the invention is to provide an antifogging method wherein the
surface of a transparent substrate such as a mirror, lens and glass is almost
permanently maintained highly hydrophilic.
A further object of the invention is to provide an antifogging coating which has an
improved durability and abrasion resistance.
Another object of the invention is to provide an antifogging coating which can be
readily applied onto a surface requiring antifogging treatment.
Yet another object of the invention is to provide an antifogging transparent substrate
such as a mirror, lens or glass, as well as a method of making such an antifogging
transparent substrate, wherein the substrate surface is maintained highly hydrophilic
for an extended period of time to thereby provide a high degree of antifogging
property for an extended period.
In the fields of architecture and painting, it has been pointed out that growing
environmental pollution tends to inadvertently accelerate fouling, contamination or
soiling of exterior building materials, including outdoor buildings themselves and the
coatings thereon.
In this regard, air-borne grime and dust particles are allowed under fair weather
conditions to fall and deposit on roofs and outer walls of buildings. When it rains, the
deposits are washed away by rainwater and are caused to flow along the outer walls of
the buildings. Furthermore, air-borne grime is captured by rain and is carried onto
surfaces (such as outer walls) of outdoor structures and buildings, where the grime
may flow along or down the surface. For these reasons, contaminant substances are
caused to adhere onto the surface along the paths of rainwater. As the surface is dried,
a striped pattern of dirt, stain or smudge will appear on the surface.
The dirt or stain thus formed on the exterior building materials and exterior coatings
consists of contaminant substances which include combustion products such as carbon
black, city grime, and inorganic substances such as clay particles. The diversity of the
fouling substances is considered to make the antifouling countermeasures complicated
(Yoshinori KITSUTAKA, "Accelerated Test Method For soiling on Finishing
Materials of External Walls", Bulletin of Japan Architecture Society, vol. 404
(October 1989), pages 15-24). Hitherto, it has been commonly considered in the art
that water-repellent paints such as those containing polytetra-fluoroethylene (PTFE)
are desirable to prevent fouling or soiling of exterior building materials and the like.
Recently, however, it is pointed out that, in order to cope with city grime containing a
large amount of oleophilic components, it is rather desirable to render the surface of
coatings as hydrophilic as possible ("Highpolymer", vol. 44, May 1995, page 307).
Accordingly, it has been proposed in the art to coat a building with a hydrophilic
graftcopolymer (Newspaper "Daily Chemical Industry", Jan. 30, 1995). Reportedly,
the coating film presents a hydrophilicity of 30-40.degree. in terms of the contact
angle with water.
However, in view of the fact that inorganic dusts, which may typically be represented
by clay minerals, have a contact angle with water ranging from 20 to 50.degree. (so
that they have affinity for graftcopolymer having a contact angle with water of
30-40.degree.), it is considered that such inorganic dusts are apt to adhere to the
surface of the graftcopolymer coating and, hence, the coating is not able to prevent
fouling or contamination by inorganic dusts.
Also available in the market are various hydrophilic paints which comprise acrylic
resin, acryl-silicone resin, aqueous silicone, block copolymers of silicone resin and
acrylic resin, acryl-styrene resin, ethylene oxides of sorbitan fatty acid, esters of
sorbitan fatty acid, acetates of urethane, cross-linked urethane of polycarbonatediol
and/or polyisocyanate, or cross-linked polymers of alkylester polyacrylate. However,
since the contact angle with water of these hydrophilic paints is as large as
50-70.degree., they are not suitable to effectively prevent fouling by city grimes
which contain large amount of oleophilic components.
Accordingly, a further object of the invention is to provide a method for rendering a
surface of a substrate highly hydrophilic and antifouling.
Another object of the invention is to provide a method wherein the surface of
buildings, window glasses, machinery or articles is rendered highly hydrophilic to
thereby prevent fouling of or to permit self-cleaning of or to facilitate cleaning of the
surface.
Yet another object of the invention is to provide a highly hydrophilic antifouling
substrate, as well as a method of making thereof, which is adapted to prevent fouling
of or to permit self-cleaning of or to facilitate cleaning of the surface.
In certain apparatus, formation of moisture condensate on a surface thereof often
hampers operation of the apparatus when condensate has grown into droplets. In heat
exchangers, for example, the heat exchanging efficiency would be lowered if
condensate particles adhering to radiator fins have grown into large droplets.
Accordingly, another object of the invention is to provide a method for preventing
adherent moisture condensate from growing into larger water droplets wherein a
surface is made highly hydrophilic to thereby permit adherent moisture condensate to
spread into a water film.
DISCLOSURE OF THE INVENTION
The present inventors have found that, upon photoexcitation, a surface of a
photocatalyst is rendered highly hydrophilic. Surprisingly, it has been discovered that,
upon photoexcitation of photocatalytic titania with ultraviolet light, the surface
thereof is rendered highly hydrophilic to the degree that the contact angle with water
becomes less than 10.degree., more particularly less than 5.degree., and even reached
about 0.degree..
Based on the foregoing findings, the present invention provides, broadly, a method for
rendering a surface of a substrate highly hydrophilic, a substrate having a highly
hydrophilic surface and a method of making such a substrate. According to the
invention, the surface of the substrate is coated with an abrasion-resistant
photocatalytic coating comprised of a photocatalytic semiconductor material.
Upon irradiation for a sufficient time with a sufficient intensity of a light having a
wavelength which has an energy higher than the bandgap energy of the photocatalytic
semiconductor, the surface of the photocatalytic coating is rendered highly
hydrophilic to exhibit a super-hydrophilicity. The term "super-hydrophilicity" or
"super-hydrophilic" as used herein refers to a highly hydrophilic property (i.e., water
wettability) of less than about 10.degree. in terms of the contact angle with water.
Similarly, the term "superhydrophilification" or "superhydrophilify" refers to
rendering a surface highly hydrophilic to the degree that the contact angle with water
becomes less than about 10.degree.. It is preferred that a super-hydrophilic drophilic
surface have a water wettability of less than about 5.degree..
The process of superhydrophilification of a surface resulting from photoexcitation of
a photocatalyst cannot be explained presently with any certainty. seemingly,
photocatalytic superhydrophilification is not necessarily identical with
photodecomposition of a substance arising from photocatalytic redox process known
hitherto in the field of photocatalyst. In this regard, the conventional theory admitted
in the art regarding the photocatalytic redox process was that electron-hole pairs are
generated upon photoexcitation of the photocatalyst, the electrons thus generated
acting to reduce the surface oxygen to produce superoxide ions (O.sub.2.sup.-), the
holes acting to oxidize the surface hydroxyl groups to produce hydroxyl radicals
(.multidot.OH), these highly active oxygen species (O.sub.2.sup.- and .multidot.OH)
then acting to decompose a substance through redox process.
However, it seems that the superhydrophilification phenomenon provoked by a
photocatalyst is not consistent, in at least two aspects, with the conventional
understanding and observation regarding the photocatalytic decomposition process of
substances. First, according to a theory widely accepted hitherto, it has been believed
that, in a certain photocatalyst such as rutile and tin oxide, the energy level of the
conduction band is not high enough to promote the reduction process so that the
electrons photoexcited up to the conduction band remain unused and become
excessive whereby the electron-hole pairs once generated by photoexcitation undergo
recombination without contributing in the redox process. In contrast, the present
inventors have observed that the super-hydrophilification process by a photocatalyst
takes place even with rutile and tin oxide, as described later.
Secondly, the conventional wisdom was that the decomposition of substances due to
photocatalytic redox process is not developed unless the thickness of a photocatalytic
layer is greater than at least 100 nm. Conversely, the present inventors have found that
photocatalytic superhydrophilification occurs even with a photocatalytic coating
having a thickness on the order of several nanometers.
Accordingly, it is believed (though it cannot be confirmed with certainty) that the
superhydrophilification process caused by a photocatalyst is a phenomenon somewhat
different from photodecomposition of substances resulting from the photocatalytic
redox process. As described later, it has been observed that superhydrophilification of
a surface does not occur unless a light having an energy higher than the band gap
energy of the photocatalyst is irradiated. It is considered that, presumably, the surface
of a photocatalytic coating is rendered superhydrophilic as a result of water being
chemisorbed thereon in the form of hydroxyl groups (OH.sup.-) under the
photocatalytic action of the photocatalyst.
Once the surface of the photocatalytic coating has been made highly hydrophilic upon
photoexcitation of the photocatalyst, the hydrophilicity of the surface will be
sustained for a certain period of time even if the substrate is placed in the dark. As
time elapses, the superhydrophilicity of the surface will be gradually lost because of
contaminants adsorbed on the surface hydroxyl groups. However, the
superhydrophilicity will be restored when the surface is again subjected to
photoexcitation.
To initially superhydrophilify the photocatalytic coating, any suitable source of light
may be used which has a wavelength of an energy higher than the band gap energy of
the photocatalyst. In the case of those photocatalysts such as titania for which the
photoexciting wavelength is in the ultraviolet range of the spectrum, the ultraviolet
light contained in the sunlight may advantageously be used as the photoexciting light
source if the sunlight impinges upon the substrate coated by the photocatalytic coating.
When the photocatalyst is to be photoexcited indoors or at night, an artificial light
source may be used. In the case where the photocatalytic coating is made of silica
blended titania as described later, the surface thereof can readily be rendered
hydrophilic even by a weak ultraviolet radiation contained in the light emitted from a
fluorescent lamp.
After the surface of the photocatalytic coating has once been superhydrophilified, the
superhydrophilicity may be maintained or renewed by a relatively weak light. In the
case of titania, for example, maintenance and restoration of the superhydrophilicity
may be accomplished to a satisfactory degree even by a weak ultraviolet light
contained in the light of indoor illumination lamps such as fluorescent lamps.
The photocatalytic coating of the present invention exhibits super-hydrophilicity even
if the thickness thereof is made extremely small. It presents a sufficient hardness
when made, in particular, from a photocatalytic semiconductor material comprising a
metal oxide. Therefore, the present photocatalytic coating may have an adequate
durability and abrasion resistivity.
Superhydrophilification of a surface may be utilized for various applications. In one
aspect of the invention, this invention provides an antifogging method for a
transparent member, or provides an antifogging transparent member, or provides a
method of making an antifogging member. According to the invention, a transparent
member is prepared, and the surface of the transparent member is coated with a
photocatalytic coating.
The transparent member may include a mirror such as a rearview mirror for a vehicle,
a bathroom or lavatory mirror, a dental mouth mirror, or a road mirror; a lens such as
an eyeglass lens, optical lens, photographic lens, endoscopic lens, or light projecting
lens; a prism; a windowpane for a building or control tower; a windowpane for a
vehicle such as an automobile, railway vehicle, aircraft, watercraft, submarine,
snowmobile, ropeway gondola, pleasure garden gondola and spacecraft; a windshield
for a vehicle such as an automobile, railway vehicle, aircraft, watercraft, submarine,
snowmobile, motorcycle, ropeway gondola, pleasure garden gondola and spacecraft; a
shield for protective or sporting goggles or mask including diving mask; a shield for a
helmet; a show window glass for chilled foods; or a cover glass for a measuring
instrument.
Upon subjecting the transparent member provided with the photocatalytic coating to
irradiation by a light to thereby photoexcite the photocatalyst, the surface of the
photocatalytic coating will be superhydrophilified. Thereafter, in the event that
moisture in the air or steam undergoes condensation, the condensate will be
transformed into a relatively uniform film of water without forming discrete water
droplets. As a result, the surface will be free from the formation of a light diffusing
fog.
Similarly, in the event that a windowpane, a rearview mirror of a vehicle, a
windshield of a vehicle, eyeglass lenses, a helmet shield, or other substrate is
subjected to a rainfall or a splash of water, the water droplets adhering onto the
surface will be quickly spread over into a uniform water film thereby preventing
formation of discrete water droplets which would otherwise hinder visibility through,
or reflection from, the substrate.
Accordingly, a high degree of view and visibility is secured so that the safety of
vehicle and traffic is secured and the efficiency of various activities improved.
In another aspect, this invention provides a method for self-cleaning a surface of a
substrate wherein the surface is superhydrophilified and is self-cleaned by rainfall.
This invention also provides a self-cleaning substrate and a method of making thereof.
The substrate may be any of a variety of articles, including an exterior member,
window sash, structural member, or windowpane of a building; an exterior member or
coating of a vehicle such as automobile, railway vehicle, aircraft, and watercraft; an
exterior member, dust cover or coating of a machine, apparatus or article; and an
exterior member or coating of a traffic sign, various display devices, and
advertisement towers, that are made, for example, of metal, ceramics, glass, plastics,
wood, stone, cement, concrete, a combination thereof, a laminate thereof, or other
materials. The surface of the substrate is coated with the photocatalytic coating.
Since the building, or machine or article disposed outdoors, is exposed to the sunlight
during the daytime, the surface of the photocatalytic coating will be rendered highly
hydrophilic. Furthermore, the surface will occasionally be subjected to rainfall. Each
time the superhydrophilified surface receives a rainfall, dust and grime and
contaminants deposited on the surface of the substrate will be washed away by rain
whereby the surface is self-cleaned.
As the surface of the photocatalytic coating is rendered highly hydrophilic to the
degree that the contact angle with water becomes less than about 10.degree.,
preferably less than about 5.degree., particularly equal to about 0.degree., not only
city grime containing large amounts of oleophilic constituents but also inorganic dusts
such as clay minerals will be readily washed away from the surface. In this manner,
the surface of the substrate will be self-cleaned and kept clean to a high degree under
the action of nature. This will permit, for instance, to eliminate or largely reduce
cleaning of windowpanes of towering buildings.
In still another aspect, this invention provides an antifouling method for a building,
window glass, machine, apparatus, or article wherein the surface thereof is provided
with a photocatalytic coating and is rendered highly hydrophilic to prevent fouling.
The surface thus superhydrophilified will prevent contaminants from adhering to the
surface when rainwater which is laden with contaminants originating from air-borne
dust and grime flows down along the surface. Therefore, in combination with the
above-mentioned self-cleaning function performed by rainfall, the surface of the
building and the like may be maintained in a high degree of cleanliness for an
extremely long period of time.
In a further aspect of the invention, a photocatalytic coating is provided on a surface
of an apparatus or article, such as an exterior or interior member of a building, or a
windowpane, household, toilet bowl, bath tub, wash basin, lighting fixture,
kitchenware, tableware, sink, cooking range, kitchen hood, or ventilation fan, said
apparatus or article being made from metal, ceramics, glass, plastics, wood, stone,
cement, concrete, a combination thereof, a laminate thereof, or other materials, and
the surface is photoexcited as required.
When these articles which are fouled by oil or fat are soaked in, wetted with or rinsed
by water, fatty dirt and contaminants will be released from the superhydrophilified
surface of the photocatalytic coating and will be readily removed therefrom.
Accordingly, for example, a tableware fouled by oil or fat may be cleansed without
resort to a detergent.
In another aspect, this invention provides a method for preventing growth of
condensate droplets adhering to a substrate or for causing adherent water droplets to
spread into a uniform water film. To this end, the surface of the substrate is coated
with a photocatalytic coating.
Once the surface of the substrate has been super-hydrophilified upon photoexcitation
of the photocatalytic coating, moisture condensate or water droplets that have come to
adhere to the surface will be spread over the surface to form a uniform aqueous film.
By applying this method, for example, to radiator fins of a heat exchanger, it is
possible to prevent fluid passages for a heat exchange medium from being clogged by
condensate; thus the present invention may be used to enhance the heat exchange
efficiency. Also, when this method is applied to a mirror, lens, windowpane,
windshield, pavement, or other such surface, it is possible to promote drying of the
surface after wetting with water.
The present inventors have further discovered that hydrophilification of a surface
layer made of a photocatalyst results from water molecules being physisorbed onto
the surface under the photocatalytic action of the photocatalyst.
Based on this discovery, the present invention further provides a method and a
composite wherein a substrate is coated with a surface layer comprised of a
photocatalyst and wherein upon photoexcitation of the photocatalyst the molecules of
water are physisorbed by hydrogen bonding onto the surface layer to thereby form a
layer of physisorbed water of a high density.
As a layer of physisorbed water is formed on the surface of the photocatalytic layer,
the surface is readily hydrophilified to a high degree. Due to the presence of the layer
of physisorbed water, the hydrophilicity of the surface is maintained for a long period
of time even after photoexcitation is discontinued, thereby minimizing the loss of
hydrophilicity over time. Moreover, when the photocatalyst is photoexcited again, the
hydrophilicity of the surface is readily recovered within a short period of time of
irradiation or with a weak irradiation intensity.
These features and advantages of the invention as well as other features and
advantages thereof will become apparent from the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows the energy level of the valance band and the conduction band of various
semiconductor photocatalysts usable in the present invention;
FIGS. 2A and 2B are schematic cross-sectional views in a microscopically enlarged
scale of the photocatalytic coating formed on the surface of a substrate and showing
the hydroxyl groups being chemisorbed on the surface upon photoexcitation of the
photocatalyst;
FIGS. 3-5, 7 and 9 are graphs respectively showing the variation, in response to time,
of the contact angle with water of various specimens in the Examples as the
specimens are subjected to irradiation of ultraviolet light;
FIG. 6 shows Raman spectra of a surface of photocatalytic coating made of silicone;
FIGS. 8 and 16 are graphs showing the result of pencil hardness tests;
FIG. 10 is a graph showing the relationship between the thickness of the
photocatalytic coating and the capability of the coating to decompose methyl
mercaptan;
FIGS. 11A and 11B are front and side elevational views, respectively, of outdoor
accelerated fouling testing equipment;
FIGS. 12-15 are graphs showing the contact angle with water versus the molar ratio of
silica in silica-blended titania;
FIG. 17 is a graph showing to what degree various surfaces having different
hydrophilicity are fouled by city grime and sludge;
FIGS. 18A-18C are graphs showing the variation, in response to time, of the contact
angle with water when ultraviolet light having different wavelengths is irradiated on
the surface of the photocatalytic coating;
FIGS. 19A and 19B, FIGS. 20A and 20B, FIGS. 21A and 21B, FIGS. 22A and 22B,
and FIGS. 23A and 23B, respectively, are graphs showing the infrared absorption
spectrum of the surface of the photocatalytic coating; and,
FIG. 24 is a schematic cross-sectional view in a microscopically enlarged scale of the
surface of the photocatalytic coating and showing molecules of water physisorped
onto the surface upon photoexcitation of the photocatalyst.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A substrate having a surface requiring super-hydrophilification is prepared and is
coated with a photocatalytic coating. In the case where the substrate is made from a
heat resistive material such as metal, ceramics and glass, the photocatalytic coating
may be fixed on the surface of the substrate by sintering particles of a photocatalyst
as described later. Alternatively, a thin film of the amorphous form of a precursor of
the photocatalyst may be first formed on the surface of the substrate and the
amorphous photocatalyst precursor may then be transformed into photoactive
photocatalyst by heating and crystallization.
In the case where the substrate is formed of a non heat-resistive material such as
plastic or is coated with a paint, the photocatalytic coating may be formed by applying
onto the surface a photooxidation-resistant coating composition containing the
photocatalyst and by curing the coating composition, as described later.
When an antifogging mirror is to be manufactured, a reflective coating may be first
formed on the substrate and the photocatalytic coating may then be formed on the
front surface of the mirror. Alternatively, the reflective coating may be formed on the
substrate subsequent to or during the course of the step of coating of the photocatalyst.
Photocatalyst
The most preferred example of the photocatalyst usable in the photocatalytic coating
according to the invention is titania (TiO.sub.2). Titania is harmless, chemically stable
and available at a low cost. Furthermore, titania has a high band gap energy and,
hence, requires ultraviolet (UV) light for photoexcitation. This means that absorption
of the visible light does not occur during the course of photoexcitation so that the
coating is free from the problem of coloring which would otherwise occur due to a
complementary color component. Accordingly, titania is particularly suitable to coat
on a transparent member such as glass, lens and mirror.
Both the anatase and rutile forms of titania may be used. The advantage of the anatase
form of titania is that a sol in which extremely fine particles of anatase are dispersed
is readily available on the market so that it is easy to make an extremely thin film. on
the other hand, the advantage of the rutile form of titania is that it can be sintered at a
high temperature so that a coating that has excellent strength and abrasion resistance
can be obtained. Although the rutile form of titania is lower in the conduction band
level than the anatase form as shown in FIG. 1, it may be used as well for the purpose
of photocatalytic superhydrophilification.
It is believed that, when a substrate 10 is coated with a photocatalytic coating 12 of
titania and the coating is subjected to photoexcitation by UV light, water is
chemisorbed on the surface in the form of hydroxyl groups (OH.sup.31) as a result of
the photocatalytic action, as shown in FIG. 2A. As a result, the surface becomes
superhydrophilic.
Other photocatalysts which can be used in the photo-catalytic coating according to the
invention may include a metal oxide such as ZnO, SnO.sub.2, SrTiO.sub.3, WO.sub.3,
Bi.sub.2 O.sub.3, or Fe2O.sub.3, as shown in FIG. 1. It is believed that, similar to
titania, these metal oxides are apt to adsorb the surface hydroxyl groups (OH.sup.-)
because the metallic element and oxygen are present at the surface.
As shown in FIG. 2B, the photocatalytic coating may be formed by blending particles
14 of photocatalyst in a layer 16 of metal oxide. In particular, the surface can be
hydrophilified to a high degree when silica or tin oxide is blended in the photocatalyst
as described later.
Thickness of Photocatalytic Coating
In the case that the substrate is made of a transparent material as in the case of glass, a
lens and a mirror, it is preferable that the thickness of the photocatalytic coating is not
greater than 0.2 .mu.m. With such a thickness, coloring of the photocatalytic coating
due to the interference of light can be avoided. Moreover, the thinner the
photocatalytic coating is, the more transparent the substrate can be. In addition, the
abrasion resistance of the photocatalytic coating is increased with decreasing
thickness.
The surface of the photocatalytic coating may be covered further by an
abrasion-resistant or corrosion-resistant protective layer or other functional film
which is susceptible to hydrophilification.
Formation of Photocatalytic Layer by Calcination of Amorphous Titania
When the substrate is made of a heat resistive material such as metal, ceramics and
glass, one of the preferred methods for forming an abrasion resistant photocatalytic
coating which exhibits the superhydrophilicity of such a degree that the contact angle
with water becomes as small as 0.degree. is to first form a coating of the amorphous
form of titania on the surface of the substrate and to then calcine the substrate to
thereby transform by phase transition amorphous titania into crystalline titania (i.e.,
anatase or rutile). Formation of amorphous titania may be carried out by one of the
following methods.
(1) Hydrolysis and Dehydration Polymerization of Organic Titanium Compound
To an alkoxide of titanium, such as tetraethoxytitanium, tetraisopropoxytitanium,
tetra-n-propoxytitanium, tetrabuthoxytitanium, or tetramethoxytitanium, is added a
hydrolysis inhibitor such as hydrochloric acid and ethylamine, the mixture being
diluted by alcohol such as ethanol or propanol. While subjected to partial or complete
hydrolysis, the mixture is applied to the surface of the substrate by spray coating, flow
coating, spin coating, dip coating, roll coating or any other suitable coating method,
followed by drying at a temperature ranging from the ambient temperature to
200.degree. C. Upon drying, hydrolysis of titanium alkoxide will be completed to
result in the formation of titanium hydroxide which then undergoes dehydration
polymerization whereby a layer of amorphous titania is formed on the surface of the
substrate.
In lieu of titanium alkoxide, other organic compounds of titanium such as chelate of
titanium or acetate of titanium may be employed.
(2) Formation of Amorphous Titania from Inorganic Titanium Compound
An acidic aqueous solution of an inorganic compound of titanium such as TiCl.sub.14
or Ti(So.sub.4).sub.2 is applied to the surface of a substrate by spray coating, flow
coating, spin coating, dip coating, or roll coating. The substrate is then dried at a
temperature of 100-200.degree. C. to subject the inorganic compound of titanium to
hydrolysis and dehydration polymerization to form a layer of amorphous titania on the
surface of the substrate. Alternatively, amorphous titania may be formed on the
surface of the substrate by chemical vapor deposition of TiCl.sub.4.
(3) Formation of Amorphous Titania by sputtering
Amorphous titania may be deposited on the surface of the substrate by bombarding a
target of metallic titanium with an electron beam in an oxidizing atmosphere.
(4) Calcination Temperature
Calcination of amorphous titania may be carried out at a temperature at least higher
than the crystallization temperature of anatase. Upon calcination at a temperature of
400-500.degree. C. or more, amorphous titania may be transformed into the anatase
form of titania. Upon calcination at a temperature of 600-700.degree. C. or more,
amorphous titania may be transformed into the rutile form of titania.
(5) Formation of Diffusion Prevention Layer
When the substrate is made of materials such as glass or glazed tile which contains
alkaline network-modifier ions (e.g., sodium), it is preferable that an intermediate
layer of silica and the like is formed between the substrate and the layer of amorphous
titania prior to calcination. This arrangement prevents alkaline network-modifier ions
from being diffused from the substrate into the photocatalytic coating during
calcination of amorphous titania. As a result, superhydrophilification may be
accomplished to the degree that the contact angle with water becomes as small as
0.degree..
Photocatalytic Layer of Silica-Blended Titania
Another preferred method of forming an abrasion resistant photocatalytic coating
which exhibits the superhydrophilicity of such a degree that the contact angle with
water approaches or is equal to 0.degree. is to form on the surface of the substrate a
photocatalytic coating comprised of a mixture of titania and silica. The ratio of silica
to the sum of titania and silica (by mole percent) may be 5-90%, preferably 10-70%,
more preferably 10-50%. The formation of a photocatalytic coating comprised of
silica-blended titania may be carried out by any of the following methods.
(1) A suspension containing particles of the anatase form or rutile form of titania and
particles of silica is applied to the surface of a substrate, followed by sintering at a
temperature less than the softening point of the substrate.
(2) A mixture of a precursor of amorphous silica (e.g., tetraalkoxysilane such as
tetraethoxysilane, tetraisopropoxysilane, tetra-n-propoxysilane, tetrabuthoxysilane,
and tetramethoxysilane; silanol formed by hydrolysis of tetraalkoxysilane; or
polysiloxane having a mean molecular weight of less than 3000) and a crystalline
titania sol is applied to the surface of a substrate and is subjected to hydrolysis where
desired to form silanol, followed by heating at a temperature higher than about
100.degree. C. to subject the silanol to dehydration polymerization to thereby form a
photocatalytic coating wherein titania particles are bound by amorphous silica. In this
regard, if dehydration polymerization of silanol is carried out at a temperature higher
than about 200.degree. C., polymerization of silanol is accomplished to a high degree
so that the alkali resistance of the photocatalytic coating is enhanced.
(3) A suspension comprised of particles of silica dispersed in a solution of a precursor
of amorphous titania (e.g., an organic compound of titanium such as alkoxide, chelate
or acetate of titanium; or an inorganic compound of titanium such as TiCl.sub.4 and
Ti(So.sub.4).sub.2) is applied to the surface of a substrate and then the precursor is
subjected to hydrolysis and dehydration polymerization at a temperature ranging from
the ambient temperature to 200.degree. C. to thereby form a thin film of amorphous
titania wherein particles of silica are dispersed. Then, the thin film is heated at a
temperature higher than the crystallization temperature of titania but lower than the
softening point of the substrate to thereby transform amorphous titania into crystalline
titania by phase transition.
(4) Added to a solution of a precursor of amorphous titania (e.g., an organic
compound of titanium such as an alkoxide, chelate or acetate of titanium; or an
inorganic compound of titanium such as TiCl.sub.4 or Ti(SO.sub.4).sub.2) is a
precursor of amorphous silica (e.g., a tetraalkoxysilane such as tetraethoxysilane,
tetraisopropoxysilane, tetra-n-propoxy-silane, tetrabuthoxysilane, or
tetramethoxysilane; a hydrolyzate thereof, i.e., silanol; or a polysiloxane having a
mean molecular weight of less than 3000) and the mixture is applied to the surface of
a substrate. Then, these precursors are subjected to hydrolysis and dehydration
polymerization to form a thin film made of a mixture of amorphous titania and
amorphous silica. Thereafter, the thin film is heated at a temperature higher than the
crystallization temperature of titania but lower than the softening point of the
substrate to thereby transform amorphous titania into crystalline titania by phase
transition.
Photocatalytic Layer of Tin Oxide-Blended Titania
Still another preferred method of forming an abrasion resistant photocatalytic coating
which exhibits the superhydrophilicity of such a degree that the contact angle with
water is equal to 0.degree. is to form on the surface of a substrate a photocatalytic
coating comprised of a mixture of titania and tin oxide. The ratio of tin oxide to the
sum of titania and tin oxide may be 1-95% by weight, preferably 1-50% by weight.
Formation of a photocatalytic coating comprised of tin oxide-blended titania may be
carried out by any of the following methods.
(1) A suspension containing particles of the anatase form or rutile form of titania and
particles of tin oxide is applied to the surface of a substrate, followed by sintering at a
temperature less than the softening point of the substrate.
(2) A suspension comprised of particles of tin oxide dispersed in a solution of a
precursor of amorphous titania (e.g., an organic compound of titanium such as
alkoxide, chelate or acetate of titanium; or an inorganic compound of titanium such as
TiCl.sub.4 or Ti(SO.sub.4).sub.2) is applied to the surface of a substrate and then the
precursor is subjected to hydrolysis and dehydration polymerization at a temperature
ranging from the ambient temperature to 200.degree. C. to thereby form a thin film of
amorphous titania wherein particles of tin oxide are dispersed. Then, the thin film is
heated at a temperature higher than the crystallization temperature of titania but lower
than the softening point of the substrate to thereby transform amorphous titania into
crystalline titania by phase transition.
Silicone Paint Containing Photocatalyst
A further preferred method of forming a photocatalytic coating which exhibits the
superhydrophilicity of such a degree that the contact angle with water is equal to
0.degree. is to use a coating composition wherein particles of a photocatalyst are
dispersed in a film forming element of uncured or partially cured silicone
(organopolysiloxane) or a precursor thereof.
The coating composition is applied on the surface of a substrate and the film forming
element is then subjected to curing. Upon photoexcitation of the photocatalyst, the
organic groups bonded to the silicon atoms of the silicone molecules are substituted
with hydroxyl groups under the photocatalytic action of the photocatalyst, as
described later with reference to Examples 13 and 14, whereby the surface of the
photocatalytic coating is superhydrophilified.
This method provides several advantages. Since the photocatalyst-containing silicone
paint can be cured at ambient temperature or at a relatively low temperature, this
method may be applied to a substrate formed of a non-heat-resistant material such as
plastics. The coating composition containing the photocatalyst may be applied
whenever desired by way of brush painting, spray coating, roll coating and the like on
any existing substrate requiring superhydrophilification of the surface.
Superhydrophilification by photoexcitation of the photocatalyst may be readily
carried out even by the sunlight as a light source.
Furthermore, in the event that the coating film is formed on a plastically deformable
substrate such as a steel sheet, it is possible to readily subject the steel sheet to plastic
working as desired after curing of the coating film and prior to photoexcitation. Prior
to photoexcitation, the organic groups are bonded to the silicon atoms of the silicone
molecules so that the coating film has an adequate flexibility. Accordingly, the steel
sheet may be readily deformed without damaging the coating film. After plastic
deformation, the photocatalyst may be subjected to photoexcitation whereupon the
organic groups bonded to the silicon atoms of the silicone molecules will be
substituted with hydroxyl groups under the action of photocatalyst to thereby render
the surface of the coating film superhydrophilic.
It is believed that the photocatalyst-containing silicone paint has a sufficient
resistance to photooxidation action of the photocatalyst because it is composed of the
siloxane bond.
Another advantage of the photocatalytic coating made of photocatalyst-containing
silicone paint is that, once the surface has been rendered superhydrophilic, the
super-hydrophilicity is maintained for a long period of time even if the coating is kept
in the dark and a further advantage is that the superhydrophilicity can be restored even
by the light of an indoor illumination lamp such as fluorescent lamp.
Examples of the film forming element usable in the invention include
methyltrichlorosilane, methyltribromosilane, methyltrimethoxysilane,
methyltriethoxysilane, methyltriisopropoxysilane,methyltri-t-buthoxysilane;
ethyltrichlorosilane, ethyltribromosilane, ethyltrimethoxysilane, ethyltriethoxysilane,
ethyltriisopropoxysilane, ethyltri-t-buthoxysilane; n-propyltrichlorosilane,
n-propyltribromosilane, n-propyltrimethoxysilane, n-propyltriethoxysilane,
n-propyltriisopropoxysilane, n-propyltri-t-buthoxysilane; n-hexyltrichlorosilane,
n-hexyltribromosilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane,
n-hexyltriisopropoxysilane, n-hexyltri-t-buthoxysilane; n-decyltrichlorosilane,
n-decyltribromosilane, n-decyltrimethoxysilane, n-decyltriethoxysilane,
n-decyltriisopropoxysilane, n-decyltri-t-buthoxysilane; n-octadecyltrichlorosilane,
n-octadecyltribromosilane, n-octadecyltrimethoxysilane, n-octadecyltriethoxysilane,
n-octadecyltriisopropoxysilane, n-octadecyltri-t-buthoxysilane; phenyltrichlorosilane,
phenyltribromosilane, phenyltrimethoxysilane, phenyltriethoxysilane,
phenyltriisopropoxysilane, phenyltri-t-buthoxysilane; tetrachlorosilane,
tetrabromosilane, tetramethoxysilane, tetraethoxysilane, tetrabuthoxysilane,
dimethoxydiethoxysilane; dimethyldichlorosilane, dimethyldibromosilane,
dimethyldimethoxysilane, dimethyldiethoxysilane; diphenyldichlorosilane,
diphenyldibromosilane, diphenyldimethoxysilane, diphenyldiethoxysilane;
phenylmethyldichlorosilane, phenylmethyldibromosilane,
phenylmethyldimethoxysilane, phenylmethyldiethoxysilane; trichlorohydrosilane,
tribromohydrosilane, trimethoxyhydrosilane, triethoxyhydrosilane,
triisopropoxyhydrosilane, tri-t-buthoxyhydrosilane; vinyltrichlorosilane,
vinyltribromosilane, vinyltrimethoxysilane, vinyltriethoxysilane,
vinyltriisopropoxysilane, vinyltri-t-buthoxysilane; trifluoropropyltrichlorosilane,
trifluoropropyltribromosilane, trifluoropropyltrimethoxysilane,
trifluoropropyltriethoxl silane, trifluoropropyltriisopropoxysilane,
trifluoropropyltri-t-buthoxysilane; gamma-glycidoxypropylmethyldimethoxysilane,
gamma-glycidoxypropylmethyldiethoxysilane,
gamma-glycidoxypropyltrimethoxysilane gamma-glycidoxypropyltriethoxysilane,
gamma-glycidoxypropyltriisopropoxysilane,
gamma-glycidoxypropyltri-t-buthoxysilane; gamma-methacryloxypropylmethyl
dimethoxysilane, gamma-methacryloxypropylmethyldiethoxysilane,
gamma-methacryloxypropyltrimethoxysilane,
gamma-methacryloxypropyltriethoxysilane gamma-methacryloxypropyltriisopropoxy
silane,
gamma-methacryloxypropyltri-t-buthoxysilane ;gamma-aminopropylmethyldimethox
ysilane, gamma-aminopropylmethyldiethoxysilane,
gamma-aminopropyltrimethoxysilane,gamma-aminopropylmethyldimethoxysilane,
gamma-aminopropyltriisopropoxysilane, gamma-aminopropyltri-t-buthoxysilane;
gamma-mercaptopropylmethyldimethoxysilane,
gamma-mercaptopropylmethyldiethoxysilane,
gamma-mercaptopropyltrimethoxysilane, gamma-mercaptopropyltriethoxysilane,
gamma-mercaptopropyltriisopropoxysilane,
gamma-mercaptopropyltri-t-buthoxysilane; .beta.-(3,4-epoxycyclohexyl)ethyltrimetho
xysilane, .beta.-(3,4-epoxycyclohexyl)ethyltriethoxysilane; partial hydrolizates of any
of the foregoing; and mixtures of any of the foregoing.
To ensure that the silicone coating exhibits a satisfactory hardness and smoothness, it
is preferable that the coating contains (by mole percent) more than 10% of a
three-dimensionally cross-linking siloxane. In addition, to provide an adequate
flexibility of the coating film yet assuring a satisfactory hardness and smoothness, it is
preferred that the coating contains less than 60% (by mole percent) of a
two-dimensionally cross-linking siloxane. Furthermore, to enhance the speed that the
organic groups bonded to the silicon atoms of the silicone molecules are substituted
with hydroxyl groups upon photoexcitation, it is desirable to use a silicone wherein
the organic groups bonded to the silicon atoms of the silicone molecules are n-propyl
or phenyl groups. In place of silicone having siloxane bonds, an organopolysilazane
having silazane bonds may be used.
Addition of Antibacterial Enhancer
The photocatalytic coating may be doped with a metal such as Ag, Cu and Zn.
Doping of the photocatalyst with a metal such as Ag, Cu or Zn may be carried out by
adding a soluble salt of such metal to a suspension containing particles of the
photocatalyst, the resultant solution being used to form the photocatalytic coating.
Alternatively, after forming the photocatalytic coating, a soluble salt of such metal
may be applied thereon and may be subjected to irradiation of light to deposit the
metal by photoreduction.
The photocatalytic coating doped with a metal such as Ag, Cu or Zn is capable of
killing bacteria adhered to the surface. Moreover, such photocatalytic coating inhibits
growth of microorganisms such as mold, algae and moss. As a result, the surface of a
building, machine, apparatus, household, article and the like can be maintained clean
for a long period.
Addition of Photoactivity Enhancer
The photocatalytic coating may additionally be doped with a metal of the platinum
group such as Pt, Pd, Rh, Ru, Os or Ir. These metals may be similarly doped into the
photocatalyst by photoreduction deposition or by addition of a soluble salt.
A photocatalyst doped with a metal of the platinum group develops an enhanced
photocatalytic redox activity so that decomposition of contaminants adhering on the
surface will be promoted.
Photoexcitation and UV Irradiation
For antifogging purposes (e.g., with respect to a transparent member such as glass, a
lens or a mirror), it is preferable that the photocatalytic coating be formed from a
photocatalyst such as titania that has a high band gap energy and can be photoexcited
only by UV light. In such event, the photocatalytic coating does not absorb visible
light so that glass, a lens or a mirror, or other such transparent member, would not be
colored by a complementary color component. The anatase form of titania may be
photoexcited by a UV light having a wavelength less than 387 nm, with the rutile
form of titania by a UV light having a wavelength less than 413 nm, with tin oxide by
a UV light having a wavelength less than 344 nm, with zinc oxide by a UV light
having a wavelength less than 387 nm.
As a source of UV light, a fluorescent lamp, incandescent lamp, metal halide lamp,
mercury lamp or other type of indoor illumination lamp may be used. As the
antifogging glass, lens or mirror, or other transparent member, is exposed to UV light,
the surface thereof will be superhydrophilified by photoexcitation of the photocatalyst.
In a situation where the photocatalytic coating is exposed to sunlight as in the case of
a rearview mirror of a vehicle, the photocatalyst will advantageously be photoexcited
spontaneously by the UV light contained in the sunlight.
Photoexcitation may be carried out, or caused to be carried out, until the contact angle,
with water, of the surface becomes less than about 10.degree., preferably less than
about 5.degree., particularly equal to about 0.degree.. Generally, by photoexciting at a
UV intensity of 0.001 mW/cm.sup.2, the photocatalytic coating will be
superhydrophilified within several days to the degree that the contact angle with water
becomes about 0.degree.. Since the intensity of the UV light contained in the sunlight
impinging upon the earth's surface is about 0.1-1 mW/cm.sup.2, the surface will be
superhydrophilified in a shorter time when exposed to the sunlight.
In the case that the surface of the substrate is to be self-cleaned by rainfall or to be
prevented from adhesion of contaminants, the photocatalytic coating may be formed
of a photocatalyst which can be photoexcited by UV light or visible light. If the
articles covered by the photocatalytic coating are disposed outdoors, they will
ordinarily be subjected to irradiation of the sunlight and to rainfall.
When the photocatalytic coating is made of titania-containing silicone, it is preferable
to photoexcite the photocatalyst at such an intensity to ensure that a sufficient amount
of the surface organic groups bonded to the silicon atoms of the silicone molecules are
substituted with hydroxyl groups. The most convenient method therefor is to use the
sunlight.
Once the surface has been made highly hydrophilic, the hydrophilicity is sustained
even during the night. Upon exposure again to the sunlight, the hydrophilicity will be
restored and maintained.
It is preferable that the photocatalytic coating is superhydrophilified in advance before
the substrate coated by the photocatalytic coating according to the invention is offered
for use to the user.
EXAMPLES
The following Examples illustrate the industrial applicability of the invention from
various aspects.
Example 1
Antifogging Mirror--Antifogging Photocatalytic Coating with Interleaved Silica
Layer
6 parts by weight of tetraethoxysilane Si(OC.sub.2 H.sub.5).sub.4 (Wako JunYaku,
Osaka), 6 parts by weight of pure water, and 2 parts by weight of 36% hydrochloric
acid as a hydrolysis inhibitor were added to 86 parts by weight of ethanol as a solvent
and the mixture was stirred to obtain a silica coating solution. The solution was
allowed to cool for about 1 hour since the solution evolved heat upon mixing. The
solution was then applied on the surface of a soda-lime glass plate of 10 cm square in
size by the flow coating method and was dried at a temperature of 80.degree. C. As
drying proceeds, tetraethoxysilane was hydrolyzed to first form silanol Si(OH).sub.4
which then underwent dehydration polymerization to form a thin film of amorphous
silica on the surface of the glass plate.
Then a titania coating solution was prepared by adding 0.1 parts by weight of 36%
hydrochloric acid as a hydrolysis inhibitor to a mixture of 1 part by weight of
tetraethoxy-titanium (Ti(OC.sub.2 H.sub.5).sub.4)(Merck) and 9 parts by weight of
ethanol, and the solution was applied to the surface of the above-mentioned glass
plate by the flow coating method in dry air. The amount of coating was
45 .mu.g/cm.sup.2 in terms of titania. As the speed of hydrolysis of
tetraethoxytitanium was so high, hydrolysis of tetraethoxytitanium partially
commenced during the course of coating so that formation of titanium hydroxide
Ti(OH).sub.4 started.
Then the glass plate was held at a temperature of about 150.degree. C. for 1-10
minutes to permit completion of the hydrolysis of tetraethoxy-titanium and to subject
the resultant titanium hydroxide to dehydration polymerization whereby amorphous
titania was formed. In this manner, a glass plate was obtained having a coating of
amorphous titania overlying the coating of amorphous silica.
This specimen was then fired or calcined at a temperature of 500.degree. C. in order
to transform amorphous titania into the anatase form of titania. It is considered that,
due to the presence of the coating of amorphous silica underlying the coating of
amorphous titania, alkaline network-modifier ions (such as sodium ions present in the
glass plate) were prevented from diffusing from the glass substrate into the titania
coating during calcination.
Then a reflective coating of aluminum was formed by vacuum evaporation deposition
on the back of the glass plate to prepare a mirror to thereby obtain #1 specimen.
After the #1 specimen was kept in the dark for several days, a UV light was irradiated
on the surface of the specimen for about one hour at a UV intensity of 0.5
mW/cm.sup.2 (the intensity of UV light having an energy higher than the band gap
energy of the anatase form of titania, i.e., the intensity of UV light having a
wavelength shorter than 387 nm) by using a 20 W blue-light-black (BLB) fluorescent
lamp (Sankyo Electric, FL20BLB) to obtain #2 specimen.
For the purposes of comparison, a reflective coating of aluminum was formed by
vacuum evaporation deposition on the back of a glass plate provided neither with
silica nor titania coating, the product being placed in the dark for several days to
obtain #3 specimen.
The contact angle, with water, of the #2 and #3 specimens was measured by a contact
angle meter (Kyowa Kaimen Kagaku K.K. of Asaka, Saitama, Model CA-X150). The
resolving power at the small angle side of this contact angle meter was 1.degree.. The
contact angle was measured 30 seconds after a water droplet was dripped from a
micro-syringe onto the surface of the respective specimens. In the #2 specimen, the
reading of the contact angle meter was Of so that the surface exhibited
superhydrophilicity. In contrast, the contact angle with water of the #3 specimen was
30-40.degree..
Then the #2 and #3 specimens were tested for antifogging capability, as well as to see
how adherent water droplets would spread over the surface. Assessment of the
antifogging capability was done by filling a 500 ml beaker with 300 ml of hot water at
about 80.degree. C., and thereafter placing each specimen on the beaker for about 10
seconds with the front surface of the mirror directed downwards, and then inspecting
immediately thereafter the presence or absence of a fog on the surface of the specimen
and inspecting how the face of the tester reflected.
With the #3 specimen, the surface of the mirror was fogged by steam so that the
image of the observer's face was not reflected well. However, with the #2 specimen,
no fogging was observed at all and the face of the tester was clearly reflected.
Assessment of the spreading of adherent water droplets was carried out by dripping
several water droplets from a pipette onto the mirror surface of each specimen
inclined at an angle of 45.degree., rotating the mirror into a vertical position, and
thereafter inspecting how the droplets adhered and how the face of the observer
reflected.
With the #3 specimen, dispersed discrete water droplets which were obstructive to the
eye adhered on the mirror surface. As a result, the reflected image was disturbed by
the refraction of light due to adherent droplets so that it was difficult to observe the
reflected image with clarity. In contrast, with the #2 specimen, water droplets adhered
onto the mirror surface were allowed to spread over the surface to form a relatively
uniform water film without forming discrete water droplets. Although a slight
distortion of the reflected image due to the presence of the water film was observed, it
was possible to recognize the reflected image of the tester's face with a sufficient
clarity.
Example 2
Antifogging Mirror--Photocatalytic Coating Comprising Silica-Blended Titania
A thin film of amorphous silica was formed on the surface of a mirror (made by
Nihon Flat Glass, MFL3) in a manner similar to Example 1.
Then a coating solution was prepared by admixing 0.69 g of tetraethoxysilane (Wako
JunYaku), 1.07 g of a sol of the anatase form of titania (Nissan Chemical Ind., TA-15,
mean particle size of 0.01 .mu.m), 29.88 g of ethanol, and 0.36 g of pure water. The
coating solution was applied on the surface of the mirror by spray coating process.
The mirror was held at a temperature of about 150.degree. C. for about 20 minutes to
subject tetraethoxysilane to hydrolysis and dehydration polymerization to thereby
form on the mirror surface a coating wherein particles of the anatase form of titania
were bound by a binder of amorphous silica. The ratio by weight of titania to silica
was 1.
After the mirror was kept in the dark for several days, a UV light was irradiated by the
BLB fluorescent lamp for about one hour, at a UV intensity of 0.5 mW/cm.sub.2 to
obtain #1 specimen. The contact angle with water at the surface of the mirror was
measured by the same contact angle meter as used in Example 1 and the reading of
the contact angle meter was 0.degree..
Then, in the manner similar to Example 1, the antifogging capability and the
spreading of adherent water droplets were assessed with respect to the coated #1
specimen, as well as to an "MFL3" mirror specimen not provided with a
photocatalytic coating. In the test for antifogging property, with the coated #1
specimen, no fog was observed at all and the tester's face was clearly reflected, in
contrast to the uncoated "MFL3" mirror wherein a fog was observed on the surface of
the mirror so that the image of the tester's face was not clearly reflected. In the
inspection for spreading of adherent water droplets, with the uncoated "MFL3" mirror,
water droplets remained as droplets on the surface, causing refraction of light and
thereby disturbing the reflected image, so that it was difficult to clearly observe the
reflected image. With the coated #1 specimen, in contrast, water droplets on the
mirror were spread over the surface to form a relatively uniform water film and,
although a slight distortion was observed in the reflected image due to the presence of
the water film, it was possible to recognize the reflected image of the tester's face with
sufficient clarity.
Example 3
Antifogging Eyeclass Lens
First, a thin film of amorphous silica was formed in a manner similar to Example 1 on
both sides of an eyeglass lens commercially available on the market.
Then, the coating solution similar to that of Example 2 was spray coated on both sides
of the lens and the lens was held at a temperature of about 150.degree. C. for about 20
minutes to subject tetraethoxysilane to hydrolysis and dehydration polymerization to
thereby form on each side of the lens a coating wherein particles of the anatase form
of titania were bound by a binder of amorphous silica.
After the lens was kept in the dark for several days, it was irradiated with UV light
from a BLB fluorescent lamp for about one hour at a UV intensity of 0.5
mW/cm.sup.2. When the contact angle with water at the surface of the lens was
measured by the same contact angle meter as used in Example 1, the reading of the
contact angle meter was 0.degree.. This lens was mounted to the right-hand side of a
pair of eyeglasses, with an ordinary lens being mounted for the purposes of
comparison to the left-hand side.
When, several hours later, the tester wore the glasses and took a bath for about 5
minutes, the ordinary lens on the left was fogged with steam so that the eyesight was
lost. However, formation of fog was not observed at all on the right-hand lens coated
with the photocatalytic coating that had been subjected to UV irradiation.
As the tester then intentionally directed a shower on the glasses, obstructive water
droplets adhered on the left-hand ordinary lens so that a view was interrupted.
However, water droplets on the right-hand lens promptly spread into a water film so
that a sufficient view, with adequate clarity, was secured.
Example 4
Antifogging Glass--7 nm Thick Titania Coating
A solution containing a chelate of titanium was applied to the surface of a soda-lime
glass plate (10 cm square in size) and the titanium chelate was subjected to hydrolysis
and dehydration polymerization to form amorphous titania on the surface of the glass
plate. The plate was then calcined at a temperature of 500.degree. C. to form a surface
layer of crystals of the anatase form of titania. The thickness of the surface layer was
7 nm.
The surface of the thus obtained specimen was first subjected to irradiation with UV
light for about one hour, at a UV intensity of 0.5 mW/cm.sup.2, by using a BLB
fluorescent lamp. The contact angle with water of the surface of this specimen was
measured by a contact angle meter (made by ERMA, Model G-I-1000, the resolving
power at the small angle side being 3.degree.), and the reading of the contact angle
meter was less than 3.degree..
Then, while irradiating with UV light at a UV intensity of 0.01 mW/cm.sup.2 by
using a 20 W white fluorescent lamp (Toshiba, FL20SW), the variation, in response to
time, of the contact angle was measured. The results are plotted in the graph of FIG. 3.
It will be noted from the graph that the surface of the specimen was maintained highly
hydrophilic even by a weak UV light emitted from the white fluorescent lamp.
This Example illustrates that the surface of the photocatalytic titania coating can be
maintained highly hydrophilic even though the thickness thereof is made as extremely
small as 7 nm. This is very important in preserving the transparency of a substrate
such as a windowpane.
Example 5
Antifogging Glass--20 nm Thick Titania coating
A surface layer of anatase-form titania crystals was formed on the surface of a
soda-lime glass plate in a manner similar to Example 4. The thickness of the surface
layer was 20 nm.
Similar to Example 4, the surface of the thus obtained specimen was first subjected to
irradiation with UV light for about one hour, at a UV intensity of 0.5 mW/cm.sup.2,
by using a BLB fluorescent lamp. Then, the variation in response to time of the
contact angle was measured while subjecting the specimen to irradiation with UV
light at a UV intensity of 0.01 mW/cm.sup.2, by using a white fluorescent lamp. The
results are shown in the graph of FIG. 4. In this Example, too, the surface of the
specimen was maintained highly hydrophilic by a weak UV light emitted from a
white fluorescent lamp.
Example 6
Antifogging Glass--Effect of Calcination Temperature of Amorphous Titania
In a manner similar to Example 1, a thin film of amorphous silica was first formed on
the surface of soda-lime glass plates (each 10 cm square in size) and then a thin film
of amorphous titania was coated thereon to obtain a plurality of specimens.
These glass plates were then calcined at temperatures of 450.degree. C., 475.degree.
C., 500.degree. C., and 525.degree. C., respectively. Upon inspection by the powder
X-ray diffraction method, the presence of crystalline titania of the anatase form was
detected in the specimens calcined at 475.degree. C., 500.degree. C., and 525.degree.
C. so that transformation of amorphous titania into the anatase form crystalline titania
was confirmed in these specimens. However, in the specimen calcined at 450.degree.
C., the anatase form of titania was not detected.
The surface of the thus obtained specimens was first subjected to irradiation with UV
light for about three hours, at a UV intensity of 0.5 mW/cm.sup.2, by using a BLB
fluorescent lamp. Then, the variation in response to time of the contact angle was
measured by the contact angle meter (CA-X150) while subjecting the specimen to
irradiation with UV light, at a UV intensity of 0.02 mW/cm.sup.2, by using a white
fluorescent lamp. The results are shown in Table 1.
TABLE 1
Contact Angle (.degree.)
Calcination
immed. aft
Temp (.degree. C.) BLB irradn
450
10
475
0
500
0
525
0
3 days
later
13
0
0
0
9 days
later
15
0
0
0
14 days
later
23
0
0
0
As will be apparent from Table 1, it was found that, in the specimens which were
calcined at temperatures of 475.degree. C., 500.degree. C., and 525.degree. C.,
respectively, and in which the formation of anatase crystals were confirmed, the
contact angle was maintained at 0.degree. and the surface of the glass plate was
maintained superhydrophilic as long as irradiation with UV light by a white
fluorescent lamp was continued. In contrast, it was observed that the coating of
amorphous titania of the specimen calcined at 450.degree. C. did not exhibit
photocatalytic activity so that the contact angle increased as time elapsed.
When a blow of breath was blown upon the specimens calcined at temperatures of
475.degree. C., 500.degree. C., and 525.degree. C., respectively, no formation of fog
was observed on the specimen surfaces.
Example 7
Antifogging Glass--Effect of Alkaline Network Modifier Ion Diffusion
A titania coating solution similar to Example 1 was prepared and was applied by the
flow coating method on the surface of a soda-lime glass plate (10 cm square in size).
Similar to Example 1, the amount of coating was 45 .mu.g/cm.sup.2 in terms of titania.
The glass plate was similarly held at a temperature of about 150.degree. C. for 1-10
minutes to form amorphous titania on the surface of the glass plate. The specimen was
then calcined at a temperature of 500.degree. C. to transform amorphous titania into
the anatase form of titania.
After keeping the specimen in the dark for several days, UV light was irradiated on
the surface of the specimen for about one hour, at a UV intensity of 0.5 mW/cm.sup.2,
by using a BLB fluorescent lamp. Thereafter, the contact angle with water was
measured by the contact angle meter (CA-X150), which indicated a contact angle of
3.degree..
It is considered that the reason why the contact angle for this specimen was not
reduced to 0.degree. is that because, contrary to Example 1, the specimen of this
Example was not provided with a silica layer interleaved between the glass substrate
and the titania layer. Thus, the alkaline network-modifier ions (such as sodium ions)
were allowed to diffuse from the glass substrate into the titania coating during
calcination at 500.degree. C., whereby the photocatalytic activity of titania was
hindered.
It is therefore believed that, in order to realize the superhydrophilicity of such a
degree that the contact angle with water is equal to 0.degree., it is preferable to
provide an intermediate layer of silica as in Example 1.
Example 8
Antifogging Glass--Formation of Amorphous Titania By Sputtering
A film of metallic titanium was deposited by sputtering on. the surface of a soda-lime
glass plate (10 cm square in size). The glass plate was then calcined at a temperature
of 500.degree. C. Upon inspection by the powder X-ray diffraction method, formation
of the anatase form of titania was observed on the surface of the glass plate. Metallic
titanium was apparently oxidized into the anatase form by calcination.
Soon after calcination, the surface of the specimen was subjected to irradiation with
UV light, at a UV intensity of 0.5 mW/cm.sup.2, by using a BLB fluorescent lamp.
The contact angle with water was then measured by the contact angle meter
(CA-X150) to monitor the variation in response to time of the contact angle, while
irradiation continued. The results are shown in the graph of FIG. 5. As will be
apparent from the graph, the contact angle with water was kept less than 3.degree..
This experiment illustrates that, even in the case where the photocatalytic coating is
formed by sputtering, the surface of a glass plate is maintained highly hydrophilic
upon UV irradiation.
Example 9
Antifogging Glass--UV Intensity of 800 Lux
A thin film of amorphous silica was formed on the surface of a 10 cm-square
soda-lime glass plate in a manner similar to Example 1.
Then the coating solution of Example 2 was applied by spray coating on the surface
of the glass plate. The glass plate was then held at a temperature of about 150.degree.
C. for about 20 minutes whereby a coating in which particles of the anatase form of
titania were bound by a binder of amorphous silica was formed on the surface of the
glass plate. The ratio by weight of titania to silica was 1.
After being kept in the dark for several days, the glass plate was subjected to
irradiation with UV light for about one hour, at a UV intensity of 0.5 mW/cm.sup.2,
by a BLB fluorescent lamp. After UV irradiation, the contact angle with water of the
surface of the glass plate was measured by the contact angle meter (CA-X150) and it
was found that the contact angle was 0.degree..
Thereafter, the specimen was subjected to irradiation with UV light for 4 days, at a
UV intensity of 0.004 mW/cm.sup.2 (800 lux), by using a white fluorescent lamp.
While the specimen was under UV irradiation, the contact angle at the surface thereof
was maintained less than 2.degree.. When 4 days later a blow of breath was blown
upon the specimen, formation of fog was not observed.
In this way, it was confirmed that, even with a weak UV light such as is available for
indoor illumination achieved, for example, by a white fluorescent lamp, the surface of
the glass plate was maintained highly hydrophilic and fogging of the glass plate was
prevented.
Example 10
Antifogging Glass--Effect of Silica-to-Titania Blending Ratio
Next, tetraethoxysilane (Wako JunYaku), a sol of the anatase form of titania (Nissan
Chemical Ind., TA-15), ethanol, and pure water were admixed in varying rate to
prepare four kinds of coating solutions having different tetraethoxysilane-to-titania sol
blending ratios. The ratios of tetraethoxysilane to titania sol were selected so that,
after tetraethoxysilane was converted into amorphous silica, the ratio of silica to the
sum of silica plus titania was equal, by mole percent, to 10%, 30%, 50%, and 70%,
respectively.
Each of the coating solutions was applied by spray coating on the surface of a 10
cm-square soda-lime glass plate which was then held at a temperature of about
150.degree. C for about 20 minutes to subject tetraethoxysilane to hydrolysis and
dehydration polymerization. Thus, a coating in which particles of the anatase form of
titania were bound by a binder of amorphous silica was formed on the surface of the
glass plate.
After being kept in the dark for a week, the specimens were subjected to irradiation
with UV light for about one hour, at a UV intensity of 0.3 mW/cm.sup.2, by a BLB
fluorescent lamp. After UV irradiation, the contact angle with water was measured for
the surface of the respective specimens using the contact angle meter (CA-X150). The
contact angle was 0.degree. throughout all the specimens.
Thereafter, two specimens with coatings having 30% by mol and 50% by mol of silica,
respectively, were subjected to irradiation with UV light for 3 days, at a UV intensity
of 0.004 mW/cm.sup.2, by using a white fluorescent lamp. While the specimens were
under irradiation, the contact angle at the surface thereof was maintained less than
3.degree..
Example 11
Antifogging Glass--Rutile Form Photocatalytic Coating
A titania coating solution was prepared by adding 0.1 part by weight of 36%
hydrochloric acid as a hydrolysis inhibitor to a mixture of 1 part by weight of
tetraethoxytitanium (Ti(OC.sub.2 H.sub.5).sub.4) (Merck) and 9 parts by weight of
ethanol. The solution was then applied to the surface of a plurality of quartz glass
plates (10 cm square in size) by the flow coating method in dry air. The amount of
coating was 45 .mu.g/cm.sup.2 in terms of titania.
The glass plates were then held at a temperature of about 150.degree. C. for 1-10
minutes to subject tetraethoxytitanium to hydrolysis and dehydration polymerization
whereby a coating of amorphous titania was formed on the surface of each glass plate.
These specimens were then calcined at temperatures of 650.degree. C. and 800.degree.
C., respectively, to subject amorphous titania to crystallization. Upon inspection by
the powder X-ray diffraction method, it was found that the crystal form of the
specimen calcined at 650.degree. C. was of the anatase form while the crystal form of
the specimen calcined at 800.degree. C. was of the rutile form.
After keeping the thus obtained specimens in the dark for a week, they were subjected
to irradiation with UV light for 2 days, at a UV intensity of 0.3 mW/cm.sup.2, by a
BLB fluorescent lamp. After UV irradiation, the contact angle was measured. The
contact angle with water of the surface was 0.degree. throughout all the specimens.
It will be understood from the foregoing that a surface can be maintained highly
hydrophilic not only in the case that the photocatalyst is the anatase form of titania
but also in the case that the photocatalyst is the rutile form.
For this reason, it seems that the phenomenon of photocatalytic
superhydrophilification is not altogether the same as the photocatalytic redox reaction.
Example 12
Antifogging Glass--Transmittance Test
In a manner similar to Example 1, a thin film of amorphous silica was first formed on
the surface of a soda-lime glass plate (10 cm square in size) and then a thin film of
amorphous titania was coated thereon. The glass plate was then calcined at a
temperature of 500.degree. C. to transform amorphous titania into the anatase form of
titania. The specimen thus obtained was kept in the dark for several days. Then the
specimen was placed in a desiccator (24.degree. C. in temperature and 45-50% in
humidity) housing a BLB fluorescent lamp and was subjected to irradiation with UV
light for one day, at a UV intensity of 0.5 mW/cm.sup.2, to obtain #1 specimen. The
contact angle with water of the #1 specimen as measured was 0.degree..
Then the #1 specimen was taken out of the desiccator and was promptly positioned
above a warm bath held at 60.degree. C. and transmittance was measured 15 seconds
later. The transmittance as measured was divided by the initial transmittance to
calculate a change in transmittance caused by any fog formed through condensation of
steam.
In a manner similar to Example 7, the surface of a glass plate was coated by the
anatase form of titania to obtain #2 specimen. The #2 specimen was placed in the
desiccator and was subjected to irradiation with UV light, at a UV intensity of 0.5
mW/cm.sup.2, until the contact angle with water became equal to 3.degree..
The #2 specimen was then placed in a dark place. The #2 specimen was taken out of
the dark place at different time points and each time the contact angle with water was
measured. In addition, at each point, the #2 specimen was placed in the desiccator
(24.degree. C. in temperature and 45-50% in humidity) until the temperature was
equalized whereupon, in a manner similar to the #1 specimen, the #2 specimen was
promptly placed above a warm bath held at 60.degree. C. and the transmittance was
measured 15 seconds later to derive a change in transmittance caused by a fog formed
by condensation of steam.
For purposes of comparison, the contact angle with water was also measured with
respect to commercially marketed flat glass, acrylic resin plate, polyvinylchloride
(PCV) plate and polycarbonate (PC) plate, respectively. Thereafter, each of these
materials was placed in a desiccator, held under the same condition, to equalize the
temperature and was then promptly placed above a warm bath held at 60.degree. C.,
the transmittance being similarly measured 15 seconds later whereby a change in
transmittance caused by a fog formed by condensation of steam was calculated.
The results are shown in Table 2.
TABLE 2
Specimen
#1
#2 (3 hrs later)
#2 (6 hrs later)
Contact Angle with
Change in
Water (.degree.) Transmittance (%)
0
100
5.0
100
7.7
100
#2 (8 hrs later)
#2 (24 hrs later)
#2 (48 hrs later)
#2 (72 hrs later)
Flat Glass
Acrylic Resin Plate
PVC Plate
PC Plate
8.2
17.8
21.0
27.9
40.6
64.5
75.3
86.0
100
89.8
88.5
87.0
45.5
60.6
44.7
49.0
As will be apparent from Table above, it was confirmed that an extremely high
antifogging capability could be achieved if the contact angle with water was not
greater than 10.degree..
Example 13
Photocatalyst-Containing Silicone Coating
This Example is related to the discovery that a coating of a certain high molecular
weight compound and containing a photocatalyst is rendered highly hydrophilic when
subjected to irradiation with UV light.
As substrates, aluminum plates (10 cm square in size) were used. Each of the
substrates was first coated with a silicone layer to smooth the surface. To this end, a
first component "A" (silica sol) and a second component "B" (trimethoxymethylsilane)
of the coating composition "Glaska" marketed by Japan Synthetic Rubber Co. (Tokyo)
were mixed with each other in such a manner that the ratio by weight of silica to
trimethoxymethylsilane was equal to 3. The resultant coating mixture was applied on
each of the aluminum substrates and was subjected to curing at a temperature of
150.degree. C. to obtain a plurality of aluminum substrates (#1 specimens) each
coated with a base coating of silicone of 3 .mu.m in thickness.
Then, the #1 specimens were coated with a high-molecular-weight coating
composition containing a photocatalyst. In order to prevent a film forming element of
the coating composition from being degraded by photooxidation action of the
photocatalyst, silicone was selected as the film forming element.
More specifically, a sol of the anatase form of titania (Nissan Chemical Ind., TA-15)
and the first component "A" (silica sol) of the above-mentioned "Glaska" were
admixed. After dilution by ethanol, the above-mentioned second component "B" of
"Glaska" was further added thereto to prepare a titania containing coating
composition. The coating composition was comprised of 3 parts by weight of silica, 1
part by weight of trimethoxymethylsilane, and 4 parts by weight of titania.
The coating composition was applied onto the surface of the #1 specimens and was
cured at a temperature of 150.degree. C. to obtain #2 specimens coated with a top
coating wherein particles of the anatase form of titania were dispersed throughout a
coating film of silicone.
Then the #2 specimens were subjected to irradiation with UV light for 5 days, at a UV
intensity of 0.5 mW/cm.sup.2, by using a BLB fluorescent lamp to obtain #3
specimens. When the contact angle with water of the surface of these specimens was
measured by the contact angle meter (made by ERMA), surprisingly the reading of
the contact angle meter was less than 3.degree..
The contact angle of the #2 specimens measured prior to UV irradiation was
70.degree.. The contact angle of the #1 specimens as measured was 90.degree.. Then,
the #1 specimens were subjected further to irradiation with UV light for 5 days under
the same condition as the #2 specimens and the contact angle thereof was measured,
the contact angle as measured being 85.degree..
From the foregoing, it has been discovered that, notwithstanding the fact that silicone
inherently is substantially hydrophobic, silicone is rendered highly hydrophilic when
it contains a photocatalyst and provided that the photocatalyst is photoexcited by
irradiation with UV light.
Example 14
Raman Spectroscopic Analysis
By using a mercury lamp, the #2 specimen of Example 13 was subjected to irradiation
with UV light for 2 hours, at a UV intensity of 22.8 mW/cm.sup.2, to obtain #4
specimen. The #2 specimen prior to UV irradiation and the #4 specimen subsequent to
UV irradiation were subjected to Raman spectroscopic analysis. For the purposes of
comparison, a UV light was irradiated upon the #1 specimen under the same
conditions and the specimen was subjected to Raman spectroscopic analysis prior to
and subsequent to UV irradiation. Raman spectra are shown in the graph of FIG. 6. In
the graph of FIG. 6, the Raman spectra of the #1 specimen prior to and subsequent to
UV irradiation are shown by the single curve #1 because they are identical.
Referring to the graph of FIG. 6, in the Raman spectrum of the #2 specimen, a
dominant peak is noted at the wavenumber 2910 cm.sup.-1 corresponding to the
symmetrical stretching of the C--H bond of the sp.sup.3 hybrid orbital and a salient
peak is observed at the wavenumber 2970 cm.sup.-1 indicating the inverted
symmetrical stretching of the C--H bond of the sp.sup.3 hybrid orbital. It can
therefore be concluded that the C--H bonds are present in the #2 specimen.
In the Raman spectrum of the #4 specimen, no peak is found at the wavenumbers
2910 cm.sup.-1 and 2970 cm.sup.-1. Instead, a broad absorption band peaking at the
wavenumber 3200 cm.sup.-1 and corresponding to the symmetrical stretching of the
O--H bond is observed. It is therefore concluded that, in the #4 specimen, there is no
C--H bond but, instead, the O--H bonds are present.
In contrast, in the Raman spectrum of the #1 specimen, a dominant peak at the
wavenumber 2910 cm.sup.-1 corresponding to the symmetrical stretching of the C--H
bond of the sp.sup.3 hybrid orbital as well as a salient peak at the wavenumber 2970
cm.sup.-1 corresponding to the inverted symmetrical stretching of the C--H bond of
the sp.sup.3 hybrid orbital are noted throughout the points of time prior to and
subsequent to UV irradiation. Accordingly, it is confirmed that the C--H bonds are
present in the #1 specimen.
From the foregoing, it is considered that, when silicone which contains a
photocatalyst is subjected to irradiation with UV light, the organic groups bonded to
the silicon atoms of the silicone molecules as represented by the general formula (1)
below are substituted with the hydroxyl groups under the action of the photocatalyst
so that a derivative of silicone is formed at the surface as shown by the formula (2).
##STR1##
where R represents alkyl or aryl group. ##STR2##
Example 15
Antifogging Plastic Plate--Antifogging Coating of Photocatalyst-Containing Silicone
The surface of a plastic substrate was first coated with a silicone layer to prevent the
substrate from being degraded by the photocatalyst.
To this end, a coating solution was prepared in a manner similar to Example 13 by
admixing the first and second components "A" and "B" of the above-mentioned
"Glaska" of Japan Synthetic Rubber Co. such that the ratio by weight of silica to
trimethoxymethylsilane was equal to 3. The coating solution was applied on the
surface of 10 cm-square acrylic resin plates, and each plate was then cured at a
temperature of 100.degree. C. to obtain a plurality of acrylic resin plates (1 specimens)
each coated with a base coating of silicone of 5 .mu.m in thickness.
Next, a sol of the anatase form of titania (Nissan Chemical Ind., TA-15) and the first
component "A" of the above-mentioned "Glaska" were admixed and, after diluted by
ethanol, the second component "B" of "Glaska" was added thereto to prepare four
kinds of coating solutions having different compositions. The compositions of these
coating solutions were such that the ratio by weight of titania to the sum of titania plus
silica plus trimethoxymethylsilane was equal to 5%, 10%, 50%, and 80%, respectively.
These coating solutions were applied, respectively, onto the surface of the acrylic
resin plates coated with the silicone layer and were cured at a temperature of
100.degree. C. to obtain #2-#5 specimens each coated with a top coating wherein
particles of the anatase form of titania were dispersed throughout a coating film of
silicone.
Then the #1-#5 specimens were subjected to irradiation with UV light by a BLB
fluorescent lamp for maximum 200 hours, at a UV intensity of 0.5 mW/cm.sup.2, and
the contact angle with water of the surface of these specimens was measured by the
contact angle meter (made by ERMA) at different time points to see the variation in
response to time of the contact angle. The results are shown in the graph of FIG. 7.
As will be understood from the graph of FIG. 7, in the #1 specimen, which was not
provided with A titania-containing coating, no appreciable change in the contact angle
with water resulted from UV irradiation.
In contrast, in each of the #2-#5 specimens (each of which had a titania-containing top
coating), it will be noted that upon UV irradiation the surface was rendered
hydrophilic to the degree that the contact angle with water became less than
10.degree..
In particular, it will be understood that, in the #3-#5 specimens wherein the titania
content was greater than 10% by weight, the contact angle with water became less
than 3.degree..
Furthermore, it will be noted that in the #4 and #5 specimens having a titania contents
of 50% by weight and 80% by weight, respectively, the contact angle with water
became less than 3.degree. within a relatively short time of beginning UV irradiation.
When a blow of breath was blown upon the #4 specimen, no formation of fog was
observed. After keeping the #4 specimen in the dark for 2 weeks, the contact angle
with water was measured by the contact angle meter (CA-X150) and was found to be
less than 3.degree..
Example 16
Pencil Scratch Test
A pencil scratch test was conducted to ascertain the abrasion resistance of the
titania-containing top coating.
In a manner similar to Example 15, a plurality of 10 cm-square acrylic resin plates
were first coated with a base coating of silicone of 5 .mu.m in thickness and were then
coated with a top coating having varying titania content. In these plates, the titania
content of the top coating was 50% by weight, 60% by weight, and 90% by weight,
respectively.
According to the method H8602 of the Japanese Industrial Standard (JIS), the surface
of the specimens was scratched by various pencil leads to find the hardest pencil lead
by which the top coating was peeled off. A similar test was also conducted for a
specimen which was coated only with the base coating. The results are shown in the
graph of FIG. 8.
The top coating having a titania content of 90% by weight was peeled off by a pencil
lead of hardness 5B, but the top coating having a titania content of 60% by weight
was able to withstand a pencil lead of hardness H and showed an adequate abrasion
resistance. The abrasion resistance of the top coating apparently increases with
decreasing titania content.
Example 17
Effect of coating Thickness
In a manner similar to Example 13, a plurality of 10 cm-square aluminum plates were
first coated with a base coating of silicone of 5 .mu.m in thickness and were then
coated with an anatase-containing top coating of varying thickness to obtain a
plurality of specimens. The thickness of the top coating of the #1 specimen was
0.003 .mu.m, the thickness of the top coating of the #2 specimen being 0.1 .mu.m, the
thickness of the top coating of the 43 specimen being 0.2 .mu.m, the thickness of the
top coating of the #4 specimen being 0.6 .mu.m, and the thickness of the top coating
of the #5 specimen being 2.5 .mu.m.
While subjecting the respective specimens to irradiation with UV light, at a UV
intensity of 0.5 mW/cm.sup.2, by using a BLB fluorescent lamp, the variation in
response to time of the contact angle with water of the surface of the specimens was
measured by the contact angle meter (made by ERMA). The results are shown in the
graph of FIG. 9.
As will be apparent from the graph of FIG. 9, regardless of the thickness of the
coating, the surface of the respective specimens was rendered highly hydrophilic
within 50 hours of UV irradiation to the degree that the contact angle with water
became less than 3.degree.. It will be noted in particular that, even with the
titania-containing top coating of the thickness of less than 0.2 .mu.m, a sufficient
photocatalytic activity was achieved to the degree that the top coating surface was
rendered highly hydrophilic. In this regard, it is known that a transparent layer is
colored due to interference of light when the thickness of the layer exceeds 0.2 .mu.m.
This Example illustrates that, by limiting the thickness of the top coating to 0.2 .mu.m
or less, the surface of the top coating can be made highly hydrophilic while
preventing coloring thereof due to interference of light.
Next, the #1-#5 specimens were tested for the capability thereof to photodecompose
methyl mercaptan. Each specimen was placed, separately, in a desiccator of 11 liters
in volume made of UV permeable quartz glass, and nitrogen gas containing methyl
mercaptan was introduced therein in such a manner that the methyl mercaptan
concentration equaled 3 ppm. A 4 W BLB fluorescent lamp was placed within the
desiccator at a distance of 8 cm from the specimen to irradiate the specimen, at a UV
intensity of 0.3 mW/cm.sup.2. By sampling gas in the desiccator 30 minutes later, the
methyl mercaptan concentration was measured by gas chromatography and the
removal rate of methyl mercaptan was calculated. The results are shown in the graph
of FIG. 10.
The graph of FIG. 10 indicates that the photodecomposition capability of the
photocatalytic coating vis-a-vis methyl mercaptan increases with increasing coating
thickness. It is found that the photocatalytic photodecomposition capability was
clearly affected by the thickness of the photocatalytic layer. In view of the results
shown in FIG. 9, it seems that the photocatalytic superhydrophilification process is not
necessarily identical with the photocatalytic redox process known hitherto in the field
of photocatalyst.
Example 18
Highly Hydrophilic Photocatalytic Coating of Titania-Containing Silicone
In a manner similar to Example 13, a 10 cm-square aluminum plate was first coated
with a base coating of silicone of 5 .mu.m in thickness.
Then, a sol of the anatase form of titania (Nissan Chemical Ind., TA-15) and the
second component "B" (trimethoxymethylsilane)of the above-mentioned "Glaska"
were admixed with each other and the mixture was diluted by ethanol to prepare a
coating composition containing titania. The ratio by weight of trimethoxymethylsilane
to titania was equal to 1.
The coating composition was applied onto the surface of the aluminum plate and was
cured at a temperature of 150.degree. C. to form a top coating wherein particles of the
anatase form of titania were dispersed throughout a coating film of silicone. The
thickness of the coating was 0.1 .mu.m.
Then the specimen was subjected to irradiation with UV light for a day, at a UV
intensity of 0.5 mW/cm.sup.2, by using a BLB fluorescent lamp. When the contact
angle with water of the surface of this specimen was measured by the contact angle
meter (CA-X150), the reading of contact angle was 0.degree..
The specimen was kept in the dark for 3 weeks and the contact angle with water was
measured each week. The measured contact angle is shown in Table 3.
TABLE 3
immed. after
irradiation 1 week later
0.degree.
2.degree.
2 weeks later
1.degree.
3 weeks later
3.degree.
As will be understood from Table 3, once the surface has been superhydrophilified,
superhydrophilicity will be sustained for a substantially long time period even in the
absence of photoexcitation.
Example 19
Antibacterial Enhancer--Ag-Added Photocatalyst
In a manner similar to Example 1, a thin film of amorphous silica and a thin film of
amorphous titania were formed in sequence on the surface of a 10 cm-square
soda-lime glass plate and the glass plate was then calcined at a temperature of
500.degree. C. to transform amorphous titania into the anatase form of titania,
whereby #1 specimen was obtained.
Then an aqueous solution containing 1% by weight of silver lactate was applied onto
the surface of the #1 specimen, and the specimen was subjected to irradiation with
UV light for one minute by operating a 20 W BLB fluorescent lamp positioned at a
distance of 20 cm from the specimen whereby #2 specimen was obtained. Upon UV
irradiation, silver lactate underwent photoreduction to form silver deposit and the
surface of the specimen was rendered hydrophilic under the photocatalytic action of
titania. The #1 specimen was also subjected to UV irradiation under the same
conditions.
When the contact angle with water of the #1 and #2 specimens was measured by the
contact angle meter (made by ERMA), the contact angle in both specimens was less
than 3.degree.. When a blow of breath was blown upon these specimens, no formation
of fog was observed. For the purposes of comparison a substrate of soda-lime glass,
without coating, was tested, and it was found that the contact angle with water was
50.degree. and a fog was readily formed upon blowing of breath.
Then, the #1 and #2 specimens as well as the uncoated soda-lime glass plate were
tested for antibacterial capability. A liquid culture prepared by shake cultivating
colibacillus (Escherichia coli W3110 stock) for a night was subjected to centrifugal
washing and was diluted with sterilized distilled water by 10,000 times to prepare a
bacteria containing liquid. 0.15 ml of the bacteria containing liquid (equivalent to
10000-50000 CFU) was dripped on three glass slides which were then brought into
intimate contact with the #1 and #2 specimens and the uncoated soda-lime glass plate,
respectively, all of which had previously been sterilized by 70% ethanol. The
specimens and the uncoated plate were then subjected to irradiation from a white
fluorescent lamp placed in front of the glass slides for 30 minutes, at an intensity of
3500 lux. Thereafter, the bacteria containing liquid of respective specimens was
wiped by a sterilized gauze and was recovered in 10 ml of physiological saline and
the liquid thus recovered was applied for inoculation on a nutrient agar plate for
culture at 37.degree. C. for a day. Thereafter, the colonies of colibacillus formed on
the culture was counted to calculate the survival rate of colibacillus. The result was
that in the #1 specimen and the soda-lime glass plate the survival rate of colibacillus
was greater than 70%, but the survival rate was less than 10% in the #2 specimen.
This experiment demonstrates that, when the photocatalyst is doped with Ag, the
surface of the substrate is not only rendered highly hydrophilic but also becomes
antibacterial.
Example 20
Antibacterial Enhancer--Cu-Added Photocatalyst
In a manner similar to Example 1, a thin film of amorphous silica was formed on the
surface of each of a plurality of 10 cm-square soda-lime glass plates to obtain a
plurality of #1 specimens.
Then, similar to Example 1, a thin film of amorphous titania was formed on the
surface of one #1 specimen which was then calcined at a temperature of 500.degree. C.
to transform amorphous titania into the anatase form titania. Then an ethanol solution
containing 1 weight percent of copper acetate was applied by spray coating onto the
surface of one specimen and, after drying, the specimen was subjected to irradiation
with UV light for one minute by a 20 W BLB fluorescent lamp positioned at a
distance of 20 cm from the specimen, to thereby subject copper acetate to
photoreduction deposition and, thus, to obtain a #2 specimen wherein crystals of
titania were doped with copper. As inspected by the eye, the #2 specimen presented an
adequate light transmittance.
A soda-lime glass plate as well as the #2 specimen and the #1 specimen (without
titania coating) immediately after fabrication were tested for antifogging capability
and the contact angle with water measured. The antifogging test was done by blowing
a blow of breath upon the specimen to produce a fog on the specimen surface and by
inspecting for the presence or absence of particles of moisture condensate, using a
microscope. The contact angle was measured by the contact angle meter (made by
ERMA). The results are shown in Table 4.
TABLE 4
Immediately After Preparation of Specimen
#2 Specimen
#1 Specimen
Soda-Lime Glass
Contact Angle with
Water (.degree.)
10
Antifogging
Property
no fog
9
50
no fog
fogged
Further, after being subjected to irradiation with UV light for a month, at a UV
intensity of 0.5 mW/cm.sup.2, by a BLB fluorescent lamp, the #2 and #1 specimens
and the soda-lime glass plate were tested in a similar manner for antifogging
capability and contact angle. The results are shown in Table 5.
TABLE 5
After 1 Month of UV Irradiation
Contact Angle with
Antifogging
Water (.degree.)
Property
#2 Specimen
3
no fog
#1 Specimen
49
fogged
Soda-Lime Glass
53
fogged
Then, the #2 and #1 specimens immediately after preparation and the soda-lime glass
plate were tested for antibacterial capability in a manner similar to that described in
Example 19. The result was that in the soda-lime glass plate and the #1 specimen the
survival rate of colibacillus was greater than 70%, but the survival rate was less than
10% in the #2 specimen.
Next, the #2 and #1 specimens immediately after preparation, and the uncoated
soda-lime glass plate, were tested for deodorizing performance. Each specimen was
placed in a desiccator of 11 liters in volume made of UV permeable quartz glass and
nitrogen gas containing methyl mercaptan was introduced therein in such a manner
that the methyl mercaptan concentration equaled 3 ppm. In each case, a 4 W BLB
fluorescent lamp was placed within the desiccator at a distance of 8 cm from the
specimen to irradiate the specimen, at a UV intensity of 0.3 mW/cm.sup.2. By
sampling gas in the desiccator 30 minutes later, the methyl mercaptan concentration
was measured by gas chromatography and the removal rate of methyl mercaptan was
calculated. With the #1 specimen and the soda-lime glass plate, the removal rate of
methyl mercaptan was less than 10%. In contrast, the removal rate of the #2 specimen
was more than 90%, so that a good deodorizing performance was achieved.
Example 21
Antibacterial Enhancer--Cu-Added Photocatalyst
The first and second components "A" (silica sol) and "B" (trimethoxymethylsilane) of
"Glaska" of Japan Synthetic Rubber Co. were admixed such that the ratio by weight
of silica to trimethoxymethylsilane was equal to 3, and the mixture was applied on the
surface of a 10 cm-square acrylic resin plate, followed by curing at a temperature of
100.degree. C. to obtain an acrylic resin plate coated with a base coating of silicone of
3 .mu.m in thickness.
Then, a sol of the anatase form of titania (TA-15) and an aqueous solution containing
3 weight percent of copper acetate were mixed and, after adding further the first
component "A" (silica sol) of "Glaska" thereto, the mixture was diluted by propanol.
Then the second component "B" of "Glaska" was further added to prepare a
titania-containing coating composition. The coating composition was comprised of 3
parts by weight of silica, 1 part by weight of trimethoxymethylsilane, 4 parts by
weight of titania, and 0.08 parts by weight of copper acetate in terms of metallic
copper.
The coating composition was applied onto the surface of the acrylic resin plate and
was cured at a temperature of 100.degree. C. to form a top coating. Then the specimen
was subjected to irradiation with UV light for 5 days, at a UV intensity of 0.5
mW/cm.sup.2 by using a BLB fluorescent lamp to obtain #1 specimen.
The #1 specimen and the acrylic resin plate were investigated for antifogging
capability, contact angle with water, antibacterial performance and deodorizing
function, in a manner similar to Example 20. In the acrylic resin plate, the contact
angle with water was 70.degree. and a fog was formed as a blow of breath was blown
upon. In the #1 specimen, however, the contact angle with water was 3-9.degree. and
formation of fog did not occur. With regard to antibacterial property, in the acrylic
resin plate the survival rate of colibacillus was greater than 70%, whereas the survival
rate was less than 10% in the #1 specimen. Regarding the deodorizing property, while
the removal rate of methyl mercaptan by the acrylic resin plate was less than 10%, the
removal rate by the #1 specimen was more than 90%.
Example 22
Photo-Redox Activity Enhancer--Pt-Added Photocatalyst
In a manner similar to Example 1, a thin film of amorphous silica and then a thin film
of amorphous titania were formed on the surface of a 10 cm-square soda-lime glass
plate and the glass plate was then calcined at a temperature of 500.degree. C. to
transform amorphous titania into the anatase form titania.
Then, 1 ml of aqueous solution of chloroplatinic acid 6-hydrate H.sub.2
PtCl.sub.6.6H.sub.2 O containing 0.1 weight percent of platinum was applied onto the
specimen which was then subjected to irradiation with UV light for one minute, at a
UV intensity of 0.5 mW/cm.sup.2 by a BLB fluorescent lamp to thereby form deposit
of platinum by photoreduction of chloroplatinic acid hexahydrate to obtain a
specimen wherein crystals of titania were doped with platinum.
The specimen thus obtained was left as such for a day and was thereafter subjected to
irradiation with UV light for a day, at a UV intensity of 0.5 mW/cm.sup.2 by using a
BLB fluorescent lamp. The contact angle measured after UV irradiation was 0.degree..
Furthermore, the removal rate of methyl mercaptan as measured and calculated in a
manner similar to Example 20 was 98%.
Example 23
Self-Cleaning and Antifogging Capability
The #2 specimen of Example 13 was subjected to irradiation with UV light for 10
hours, at a UV intensity of 0.5 mW/cm.sup.2 by using a BLB fluorescent lamp to
obtain #3 specimen. When the contact angle with water of the surface of this
specimen was measured by the contact angle meter (made by ERMA), the reading of
the contact angle meter was less than 3.degree..
An outdoor accelerated fouling test apparatus as shown in FIGS. 11A and 11B was
installed atop of a building located in chigasaki City. Referring to FIGS. 11A and 11B,
this apparatus includes an inclined specimen mounting surface 22 supported by a
frame 20 and adapted to affix specimens 24 thereto. A forwardly slanted roof 26 is
fixed at the top of the frame. The roof is made of corrugated plastic sheet and is
designed to permit collected rain water to flow down in a striped pattern along the
surface of the specimens 24 affixed on the specimen mounting surface 22.
The #3 specimens, the #1 specimens of Example 13, and the #2 specimens of
Example 13 were mounted to the specimen mounting surface 22 of the apparatus and
were exposed to the weather conditions for 9 days starting from Jun. 12, 1995. The
weather and the amount of rain fall during this period were as shown in Table 6.
TABLE 6
Date
June 12
June 13
June
June
June
June
June
June
June
14
15
16
17
18
19
20
Weather
cloudy
heavy rain
Rainfall (mm)
0.0
53.0
cloudy/rain
cloudy/fair
cloudy
fair/cloudy
fair to cloudy
rain to cloudy
cly/heavy rain
20.5
0.0
0.0
0.0
0.0
1.0
56.0
Shining Hours
0
0
0
3.9
0.2
9.6
7.0
0.2
2.4
When inspected on June 14, dirt or smudge of a striped pattern was observed on the
surface of the #1 specimen. Presumably, this is because during heavy rainfall on the
preceding day the airborne hydrophobic contaminants such as combustion products
like carbon black and city grime were carried by rain and were allowed to deposit on
the specimen surface as rain water flowed down along the surface. In contrast, no dirt
or smudge was observed in the #3 specimen. Believably, this is because, since the
specimen surface was rendered highly hydrophilic, the hydrophobic contaminants
were unable to adhere onto the surface as rain water containing contaminants flowed
down and further because the contaminants were washed away by rainfall.
In the #2 specimen, dirt or smudge of a mottled pattern was observed. This is
probably because, after the #2 specimen which had not been subjected to UV
irradiation was mounted to the testing apparatus, the photocatalytic coating thereof
was not yet exposed to UV light in the sunlight to a satisfactory degree so that the
surface was unevenly hydrophilified.
When inspected on June 20, a smudge of a vertically striped pattern was remarkably
noticed on the surface of the #1 specimen which was not provided with the
photocatalytic coating. Conversely, no smudge was observed on the #3 and #2
specimens provided with the photocatalytic coating.
The contact angle with water as measured was 70.degree. for the #1 specimen and
was less than 3.degree. for the #2 and #3 specimens. The fact that the contact angle of
the #2 specimen became less than 3.degree. demonstrates that, upon irradiation by TV
light contained in the sunlight, the organic groups bonded to the silicon atoms of the
silicone molecules of the top coating were substituted with hydroxyl groups under the
photocatalytic action so that the top coating was rendered highly hydrophilic. It was
also noted that in the #3 specimen a high degree of hydrophilicity was sustained by
irradiation of the sunlight.
Example 24
Color Difference Test
Prior to and 1 month after mounting to the outdoor accelerated fouling test apparatus,
the #1 and #2 specimens of Example 23 were tested by a color difference meter
(Tokyo Denshoku) to measure a color difference. In compliance with the Japanese
Industrial Standard (JIS) H0201, the color difference was indicated by the .DELTA.E*
index. The variation in the color difference after mounting to the accelerated fouling
test apparatus is shown in Table 7.
#1 Specimen
#2 Specimen
TABLE 7
Striped Area
4.1
0.8
Background
1.1
0.5
As will be noted from Table 7, in the #1 specimen void of the photocatalytic coating,
a large amount of smudge was caused to adhere to the vertical striped area
corresponding to the flow path of rainwater, as compared with the #2 specimen
provided with the photocatalytic coating. It will also be recognized that, between the
#2 and #1 specimens, there was a substantial difference in the degree of fouling of the
background area.
Example 25
Cleansing Capability for Oil Stains
A quantity of oleic acid was applied on the surface of the #1 and #3 specimens of
Example 23, respectively, and the specimens were then immersed in water in a cistern
with the specimen surface held in a horizontal position. In the #1 specimen, oleic acid
remained adhered to the specimen surface. In contrast, in the #3 specimen, oleic acid
became rounded to form oil droplets which were then released from the surface of the
specimen to rise to the top of the water.
In this manner, it was confirmed that, in the case that the surface of a substrate was
coated with a photocatalytic top coating, the surface was maintained hydrophilic so
that, when soaked in water, oily stains were readily released away from the surface
whereby the surface was cleansed.
This Example illustrates that a tableware, for instance, fouled by oil or fat can be
readily cleansed only by soaking it in water without recourse to a detergent, provided
that the surface thereof is provided with a photocatalytic coating and if the
photocatalyst is photoexcited by UV irradiation.
Example 26
Drying of Water Wet Surface
The surface of the #1 and #3 specimens of Example 23 were wetted with water and
the specimens were left outdoors on a fair day to subject them to natural drying. The
ambient temperature was about 25.degree. C. As the #1 specimen was inspected 30
minutes later, water droplets still remained on the surface. In contrast, it was found
that the surface of the #3 specimen was completely dried.
It is considered that in the #3 specimen provided with the photocatalytic coating, the
adherent water droplets were caused to spread into a uniform film of water and for
this reason drying was accelerated.
This Example illustrates the possibility that an eyeglass lens or automotive windshield
wetted with water may be promptly dried.
Example 27
Tile with Highly Hydrophilic Surface--Coating of Sintered Titania and Silica
A sol of the anatase form of titania (Ishihara Industries of Osaka, STS-11) and a sol of
colloidal silica (Nissan Chemical Ind., "Snowtex O") were admixed at a ratio by mol
of 88:12 in terms of solid matter and the mixture was applied by spray coating on the
surface of a glazed tile (Toto Ltd., AB02E01) of 15 cm square in size, followed by
sintering for 1 hour at a temperature of 800.degree. C. to obtain a specimen covered
by a coating comprised of titania and silica. The thickness of the coating was
0.3 .mu.m. The contact angle with water immediately after sintering was 5.degree..
The specimen was kept in the dark for a week but the contact angle measured
thereafter was still 5.degree..
As the specimen surface was subjected to irradiation with UV light for 1 day, at a UV
intensity of 0.03 mW/cm.sup.2 by using a BLB fluorescent lamp, the contact angle
with water became 0.degree..
Example 28
Coating of Sintered Titania and Silica--Hydrophilification under Room Light
A sol of the anatase form of titania (STS-11) and a sol of colloidal silica (Nissan
Chemical Ind., "Snowtex 20") were admixed at a ratio by mol of 80:20 in terms of
solid matter and the mixture was applied by spray coating on the surface of a 15
cm-square glazed tile (AB02E01), followed by sintering for 1 hour at a temperature of
800.degree. C. to obtain a specimen covered by a coating comprised of titania and
silica. The thickness of the coating was 0.3 .mu.m. The contact angle with water
immediately after sintering was 5.degree..
The contact angle with water as measured after keeping the specimen in the dark for 2
weeks was 14.degree..
As the specimen surface was subjected to irradiation with UV light for 1 day, at a UV
intensity of 0.004 mW/cm.sup.2 by a white fluorescent lamp, the contact angle with
water became 4.degree..
Accordingly, it was found that the photocatalytic coating was rendered hydrophilic to
a satisfactory degree even under indoor illumination.
Example 29
Coating of Sintered Titania and Silica--Silica Content
A sol of the anatase form of titania (STS-11) and a sol of colloidal silica (Nissan
Chemical Ind., "Snowtex 20") were admixed at a varying ratio to obtain a plurality of
suspensions having a ratio by mol of silica to the solid matter of the suspension of 0%,
5%, 10%, 15%, 20%, 25% and 30%, respectively. 0.08g of each suspension was
uniformly applied by spray coating on the surface of a 15 cm-square glazed tile
(AB02E01) and each tile was fired for 1 hour at a temperature of 800.degree. C. to
obtain a plurality of specimens each covered by a coating comprised of titania and
silica.
The contact angle with water immediately after sintering of the respective specimens
was as shown in the graph of FIG. 12. As will be apparent from the graph of FIG. 12,
the initial contact angle was lowered by addition of silica.
The contact angle with water as measured after keeping the specimen in the dark for 8
days was plotted in the graph of FIG. 13. As will be noted by comparing the graph of
FIG. 12 with the graph of FIG. 13, the loss of hydrophilicity resulting from keeping
the specimens in the dark is small in the specimens containing more than 10%, in the
ratio by mol, of silica.
Thereafter, the specimens were subjected to irradiation with UV light for 2 days, at a
UV intensity of 0.03 mW/cm.sup.2 by using a BLB fluorescent lamp. The contact
angle with water after irradiation is shown in the graph of FIG. 14. It will be noted
from the graph that upon UV irradiation hydrophilicity is readily recovered in the case
where silica is added to titania.
Then the specimens were kept in the dark for further a days and the contact angle with
water was measured. The results are shown in FIG. 15. It will be noted from the graph
that the loss of hydrophilicity resulting from keeping the specimens in the dark after
UV irradiation is small in the case where silica is added to titania.
A pencil scratch test was carried out to examine the abrasion resistance of the sintered
film comprised of titania and silica. The results are shown in the graph of FIG. 16. It
will be understood that the abrasion resistivity is increased with increasing silica
content.
Example 30
Sludge Test
A mixture of a sol of the anatase form of titania (STS-11) and a sol of colloidal silica
(Snowtex 20) and having a silica content of 10% by weight in terms of solid matter
was applied to a 15 cm-square glazed tile (AB02E01) in an amount of 4.5 mg in terms
of solid matter and the tile was then calcined for 10 minutes at a temperature of
880.degree. C. The specimen was then subjected to irradiation with UV light for 3
hours, at a UV intensity of 0.5 mW/cm.sup.2 by using a BLB fluorescent lamp to
obtain #1 specimen. The contact angle with water of the #1 specimen and the glazed
tile (AB02E01) as such was 0.degree. and 30.degree., respectively.
A mixture of powders of 64.3% by weight of yellow ochre, 21.4% by weight of
calcined Kanto loam clay, 4.8% by weight of hydrophobic carbon black, 4.8% by
weight of silica powder, and 4.7% by weight of hydrophilic carbon black was
suspended in water at a concentration of 1.05 g/l to prepare a slurry.
150 ml of the thus prepared slurry was caused to flow down along the surface of the
#1 specimen and the glazed tile (AB02E01) held inclined at 45.degree., followed by
drying for 15 minutes, and 150 ml of distilled water was thereafter caused to flow
down, followed by drying for 15 minutes, the cycle of the above-mentioned sequences
being repeated for 25 times. A change in color difference and in glossiness after the
sludge test was measured. The measurement of the glossiness was carried out
according to the method laid down by the Japanese Industrial Standard (JIS) Z8741
and the variation in the glossiness was obtained by dividing the glossiness after
testing by the glossiness before testing. The results are given in Table 8.
TABLE 8
#1 Specimen
Tile (AB02E01)
Contact Angle (.degree.)
0
Color Diff. Change
0.7
Glossiness Change
93.4%
30
5.6
74.1%
Example 31
Relationship between Contact Angle with Water and Self-Cleaning and Antifouling
Capability
Various specimens were subjected to a sludge test in a manner similar to Example 30.
The tested specimens included the #1 specimen of Example 30, #2 specimen having a
copper-doped titania coating, the glazed tile (AB02E01), an acrylic resin plate, an
artificial marble plate (Toto Ltd., ML03) made of polyester resin matrix, and a
polytetrafluoroethylene (PTFE) plate. The #2 specimen was prepared by spray coating
0.3g of an aqueous solution of copper acetate monohydrate having a copper
concentration of 50 .mu.mol/g on the #1 specimen of Example 30 and, after drying,
subjecting the specimen to irradiation with UV light for 10 minutes, at a UV intensity
of 0.4 mW/cm.sup.2 by a BLB fluorescent lamp to thereby subject copper acetate
monohydrate to photoreduction deposition. The results of the sludge test are shown in
Table 9.
TABLE 9
Contact Angle
Color Difference
Specimen
with Water (.degree.)
Change
#1 Specimen
0.0
0.7
#2 Specimen
4.0
2.0
Glazed Tile
19.4
4.6
Acrylic Plate
50.9
4.5
Artif. Marble
54.8
3.2
PTFE Plate
105.1
0.9
Glossiness
Change (%)
93.8
81.5
68.3
69.3
85.2
98.2
Furthermore, various specimens were subjected for a period of a month to an
accelerated fouling test similar to Example 23. The specimens used included the #1
specimen of Example 30, the glazed tile (AB02E01), an acrylic resin plate, an
aluminum plate covered by a base coating of silicone in a manner similar to Example
13, and a PTFE plate. The results of the accelerated tests are shown in Table 10
wherein, similar to Example 24, the change in the color difference represents that of
the vertical striped area of the specimens.
TABLE 10
Specimen
#1 Specimen
Glazed Tile
Acrylic Plate
Silicone Coated
PTFE Plate
Contact Angle with
Water (.degree.)
0.0
19.4
50.9
90.0
105.1
Color Difference
Change
0.9
1.5
2.3
4.2
7.8
To facilitate understanding, the contact angle with water as well as the variation in the
color difference are plotted in the graph of FIG. 17. In the graph of FIG. 17, the curve
A indicates the relationship between the contact angle with water and the color
difference change caused by the contaminants such as airborne combustion products
like carbon black and city grime as a result of the accelerated fouling test, with the
curve B representing the relationship between the contact angle with water and the
color difference change caused by sludge as a result of the sludge test.
Referring to the graph of FIG. 17, as the contact angle with water of the substrate
increases, the dirt or stain due to combustion products and city grime becomes more
conspicuous, as will be readily understood from the curve A. This is because the
contaminants such as combustion products and city grime are generally hydrophobic
and, hence, are apt to adhere to a hydrophobic surface.
In contrast, the curve B illustrates that the dirt or stain due to sludge peaks when the
contact angle with water is in the range of 20-50.degree.. This is because the inorganic
substances such as loam and soil inherently have a hyrdophilicity on the order of
20-50.degree. in terms of the contact angle with water so that they are apt to adhere to
a surface having a similar hyrdophilicity. It will therefore be understood that, by
rendering the surface hyrdophilic to the degree that the contact angle with water is
less than 20.degree. or, alternatively, by rendering the surface hyrdophobic to the
degree that the contact angle with water is greater than 60.degree., the adherence of
the inorganic substances to a surface can be prevented.
The reason why fouling by sludge is reduced as the contact angle with water is less
than 20.degree. is that, when the surface is rendered highly hydrophilic to the degree
that the contact angle with water becomes less than 20.degree., the affinity of the
surface for water exceeds the affinity for inorganic substances so that adherence of
inorganic substances is blocked by water which preferentially adheres to the surface
and any inorganic substances that have adhered to or are tending to adhere to the
surface are readily washed away by water.
It will be noted from the foregoing that, in order to prevent both the hydrophobic and
hydrophilic substances from adhering to the surface of a building and the like, or in
order to ensure that dirt or smudge deposited on the surface is washed away by rain
water so as to permit the surface to be self-cleaned, it is desirable to modify the
surface to present a contact angle with water of less than 20.degree., preferably less
than 10.degree., more preferably less than 5.degree..
Example 32
Coating of Sintered Titania and Tin Oxide--Glazed Tile
A sol of the anatase form of titania (STS-11) and a sol of tin oxide (Taki Chemical
K.K. of Kakogawa City, Hyogo-Prefecture; mean crystallite size of 3.5 nm) were
admixed at various blending ratio (percent by weight of tin oxide to the sum of titania
plus tin oxide) shown in Table 11 and the mixtures were applied by spray coating on
the surface of 15 cm-square glazed tiles (ABO2E01), followed by sintering for 10
minutes at a temperature either of 750.degree. C. or 800.degree. C. to obtain #1-#6
specimens. After sintering, the #2, #4, #5 and #6 specimens were further doped with
silver by applying thereon an aqueous solution containing 1 weight percent of silver
nitrate and by subjecting silver nitrate to photoreduction deposition. In addition, #7-#9
specimens were further prepared by applying onto the glazed tiles only a sol of tin
oxide or a sol of titania and by sintering. After sintering, the #7 and #9 specimens
were further doped with silver.
Each specimen was kept in the dark for a week and was thereafter subjected to
irradiation with UV light for 3 days, at a UV intensity of 0.3 mW/cm.sup.2 by using a
BLB fluorescent lamp whereupon the contact angle with water was measured. The
results are shown in Table 11.
TABLE 11
Specimen
(.degree.)
SnO.sub.2 Ratio
Sintering
(wt %)
Temp. (.degree. C.)
Ag
Contact
Angle
#1
1
800
None
0
#2
#3
#4
#5
#6
#7
#8
#9
5
15
15
50
95
100
0
0
800
800
750
750
800
750
800
800
Added
None
Added
Added
Added
Added
None
Added
0
0
0
0
5
8
11
14
As will be apparent from Table 11, in the #8 and #9 specimens which were coated
only with titania, the contact angle with water exceeded 10.degree.. This is because
the alkaline network-modifier ions such as sodium ions diffused from the glaze into
the titania coating during sintering whereby the photocatalytic activity of anatase was
hindered. In contrast, it will be noted that, in the #1-#6 specimens wherein SnO.sub.2
were blended, the surface was hydrophilified to a high degree. As shown by the #7
specimen, tin oxide which is a semiconductor photocatalyst is effective in rendering
the surface hydrophilic in a manner similar to titania. Although the reason therefor is
not clear, this Example illustrates that the effect of diffusion of the alkaline
network-modifier ions can be overcome by adding tin oxide to titania.
Example 33
Sintered Titania Coating and Diffusion Prevention Layer--Glazed Tile
Tetraethoxysilane (marketed by Colcoat, "Ethyl 28") was applied by spray coating on
the surface of a 15 cm-square glazed tile (AB02E01) which was then held at a
temperature of about 150.degree. C. for about 20 minutes to subject tetraethoxysilane
to hydrolysis and dehydration polymerization whereby a coating of amorphous silica
was formed on the surface of the glazed tile.
Then, a sol of the anatase form of titania (STS-11) was applied by spray coating on
the surface of the tile which was then fired for an hour at a temperature of 800.degree.
C.
The thus obtained specimen, as well as the #8 specimen of Example 32 tested for the
purposes of comparison, were kept in the dark for a week and were then subjected to
irradiation with UV light for 1 day, at a UV intensity of 0.3 mW/cm.sup.2 by using a
BLB fluorescent lamp whereupon the contact angle with water was measured.
In contrast to the contact angle with water being 12.degree. in the #8 specimen of
Example 32, the specimen provided with the intervening layer of amorphous silica
was hydrophilified to the degree that the contact angle with water became less than
3.degree.. It is therefore considered that the layer of amorphous silica is effective in
preventing diffusion of the alkaline network-modifier ions being present in the glaze
layer.
Example 34
Amorphous Titania Calcination Coating and Diffusion Prevention Layer--Glazed Tile
In a manner similar to Example 1, a thin film of amorphous silica and then a thin film
of amorphous titania were formed in sequence on the surface of a 15 cm-square
glazed tile (AB02E01). The tile was then calcined at a temperature of 500.degree. C.
to transform amorphous titania into the anatase form titania.
The specimen thus obtained was kept in the dark for several days and was then
subjected to irradiation with UV light for 1 day, at a UV intensity of 0.5 mW/cm.sup.2
by using a BLB fluorescent lamp. The contact angle with water of the resultant
specimen as measured was 0.degree.. Similar to Example 33, it is considered that the
layer of amorphous silica is effective in rendering the surface of a tile highly
hydrophilic.
Example 35
Glazed Tile--Cleansing Capability for Oil Stains
A quantity of oleic acid was applied on the surface of the #1 specimen of Example 30.
When the specimen was then immersed in water in a cistern with the specimen
surface held in a horizontal position, oleic acid became rounded to form oil droplets
which were then released from the surface of the tile to ascend to the top of the water.
This Example also illustrates that a surface of pottery, such as tile and tableware,
fouled by oil or fat can be readily cleansed merely by soaking the object in water or
by wetting it with water, provided that the surface thereof is provided with a
photocatalytic coating and provided that the photocatalyst is photoexcited by UV
irradiation.
Example 36
Glass--Cleansing Capability for Oil Stains
In a manner similar to Example 1, a thin film of amorphous silica and then a thin film
of amorphous titania were formed in sequence on the surface of a 10 cm-square
soda-lime glass plate. The glass plate was then fired at a temperature of 500.degree. C.
to transform amorphous titania into the anatase form titania.
A quantity of oleic acid was applied on the surface of the glass plate. As the glass
plate was then immersed in water in a cistern with the surface held in a horizontal
position, oleic acid became rounded to form oil droplets which were then released
from the surface of the glass plate and floated.
Example 37
Glass--Self-Cleaning and Antifouling Capability
The specimen of Example 36 was subjected for a month to an accelerated fouling test
similar to Example 23. When inspected by the eye a month later, no smudge of a
vertically striped pattern was observed.
Example 38
Glazed Tile--Antibacterial Enhancer (Ag Doping)
A coating comprised of titania and silica was formed on the surface of a 15 cm-square
glazed tile (AB02E01) in a manner similar to Example 27.
Then an aqueous solution containing 1 weight percent of silver lactate was applied
onto the surface of the tile which was then subjected to irradiation with UV light of a
BLB fluorescent lamp to thereby subject silver lactate to photoreduction to form a
silver deposit whereby a specimen coated with silver doped titania was obtained. The
contact angle with water as measured was 0.degree..
When the tile was then tested for the antibacterial function in a manner similar to
Example 19, the survival rate of colibacillus was less than 10%.
Example 39
Glazed Tile--Antibacterial Enhancer (Cu Doping)
A coating comprised of titania and silica was formed on the surface of a 15 cm-square
glazed tile (AB02E01) in a manner similar to Example 27.
Then an aqueous solution containing 1 weight percent of copper acetate monohydrate
was applied onto the surface of the tile which was then subjected to irradiation with
UV light of a BLB fluorescent lamp to thereby subject copper acetate monohydrate to
photoreduction to form a copper deposit whereby a specimen coated with
copper-doped titania was obtained. The contact angle with water as measured was less
than 3.degree..
As the tile was then tested for the antibacterial function in a manner similar to
Example 19, the survival rate of colibacillus was less than 10%.
Example 40
Glazed Tile--Photo-Redox Activity Enhancer
A coating comprised of titania and silica was formed on the surface of a 15 cm-square
glazed tile (AB02E01) in a manner similar to Example 27.
Then, the surface of the specimen was doped with platinum in a manner similar to
Example 22. The contact angle with water as measured was 0.degree..
The removal rate of methyl mercaptan as measured in a manner similar to Example 20
was 98%.
Example 41
Effect of Photoexciting Wavelength
After being kept in the dark for 10 days, the #8 specimen of Example 32 and, for the
purposes of comparison, the glazed tile (AB02E01) without titania coating were
subjected to irradiation with UV light by using a Hg-Xe lamp under the conditions
shown in Table 12 and on doing so the variation in response to time of the contact
angle with water was measured.
TABLE 12
UV Wavelength
(nm)
313
365
405
UV Intensity
Photon Density
(mW/cm.sup.2) (photon/sec/cm.sup.2)
10.6
1.66 .times. 10.sup.16
18
3.31 .times. 10.sup.16
6
1.22 .times. 10.sup.16
The results of measurement were shown in FIGS. 18A-18C wherein the value plotted
by white dots represents the contact angle with water of the #8 specimen of Example
32 and the value plotted by black dots indicates the contact angle with water of the
glazed tile which was not provided with the titania coating.
As will be understood from FIG. 18C, hydrophilification did not occur in the case that
a UV light having an energy lower than that of a wavelength of 387 nm corresponding
to the bandgap energy of the anatase form of titania (i.e., a UV light having a
wavelength longer than 387 nm) was irradiated.
In contrast, as will be apparent from FIGS. 18A and 18B, the surface was rendered
hydrophilic upon irradiation with UV light having an energy higher than the bandgap
energy of anatase.
From the foregoing, it was confirmed that hydrophilification of a surface would not
occur unless the photocatalyst is photoexcited and that hydrophilification of a surface
results from the photocatalytic action of the photocatalyst.
Example 42
Physisorption of Water under Photocatalytic Action
Powders of the anatase form of titania (made by Nihon Aerosol, P-25) were pressed to
form three specimens in the form of a disc of compacted powders. The specimens
were subjected respectively to Experiments 1-3, described below, wherein the surface
of the specimens was tested and inspected by the Fourier transform infrared
spectroscopic analysis (FT-IR) using a Fourier transform infrared spectrometer
(FTS-40A). Throughout these experiments, an ultraviolet lamp (UVL-21) having a
wavelength of 366 nm was used for UV irradiation.
For the purpose of analyzing the infrared absorption spectrum, the following
absorption bands are assigned, respectively, to the following information.
Sharp absorption band at wavenumber 3690 cm.sup.-1 :
stretching of OH bond of chemisorbed water.
Broad absorption band at wavenumber 3300 cm.sup.-1 :
stretching of OH bond of physisorbed water.
Sharp absorption band at wavenumber 1640 cm.sup.-1 :
bending of HOH bond of physisorbed water.
Absorption bands at wavenumbers 1700 cm.sup.-1, 1547 cm.sup.-1, 1475 cm.sup.-1,
1440 cm.sup.-1, and 1365 cm.sup.-1 :
carbonyl groups of contaminants adsorbed onto the specimen surface.
Experiment 1
First, the titania disc immediately after press forming was subjected to the infrared
spectroscopic analysis. The absorption spectrum of the disc immediately after press
forming is shown by the curve #1 in the graphs of FIGS. 19A and 19B.
After keeping the titania disc for 17 hours in a dry box containing silica gel as a
desiccant, the absorption spectrum was detected which is indicated by the curve #2 in
the graphs of FIGS. 19A and 19B. As will be understood upon comparison of the #1
spectrum with the #2 spectrum, infrared absorption at the wavenumber 3690
cm.sup.-1 was drastically decreased in the #2 spectrum, indicating that chemisorbed
water has decreased. Similarly, absorption at the wavenumbers 3300 and 1640
cm.sup.-1 was drastically decreased in the #2 spectrum, indicating that physisorbed
(physically adsorbed) water has also decreased. It is therefore observed that both
chemisorbed water and physisorbed water have decreased by keeping the specimen in
dry air for 17 hours.
In contrast, infrared absorption at wavenumber 1300-1700 cm.sup.-1 due to presence
of the carbonyl groups was increased, suggesting that, during storage of the specimen,
compounds containing carbonyl groups were adsorbed onto the specimen surface
thereby contaminating the surface. It was impossible to measure the variation in the
contact angle with water at the surface of the specimen because of the porous nature
of surface of the disc-shaped specimen which was made by press-forming of titania
powders. However, it is presumed that the contact angle with water at the surface of a
specimen would be increased during storage in dry air if the specimen were made in
the form of a thin film of the anatase form of titania.
Then, the titania disc in the dry box was subjected to irradiation with UV light for an
hour, at a UV intensity of 0.5 mW/cm.sup.2 and the absorption spectrum was detected
which is shown in the graphs of FIGS. 19A and 19B by the curve #3.
As will be apparent from the #3 spectrum, absorption at wavenumber 3690 cm.sup.-1
was almost revived. Similarly, absorption at wavenumbers 3300 and 1640 cm.sup.-1
substantially restored the initial level. It is therefore observed that, upon UV
irradiation, both the amount of chemisorbed water and the amount of physisorbed
water are resumed the initial level. It is presumed that, if the specimen were made in
the form of a titania thin film, the surface of the thin film would be rendered
hydrophilic upon UV irradiation so that the contact angle with water would be
decreased.
Thereafter, the specimen was placed for 24 hours in a dark room communicated with
the ambient air and the absorption spectrum was detected. To avoid various curves
being overly complicated, the detected absorption spectrum is shown in the different
graphs of FIGS. 20A and 20B by the curve #4. Further, to provide a basis for
comparison, the #2 spectrum is reproduced in the graphs of FIGS. 20A and 20B.
As shown by the #4 curve, a slight decrease is observed in the absorption at
wavenumbers 3690 and 1640 cm.sup.-1. Accordingly, it is concluded that the amount
of chemisorbed and physisorbed water slightly decreases as the specimen after UV
irradiation is placed in the dark in the presence of moisture in the ambient air.
However, absorption at wavenumber 1300-1700 cm.sup.-1 is increased, showing that
carbonyl compounds were further adsorbed. It is presumed that, if the specimen were
made in the form of a titania thin film, the contact angle with water would be
increased in response to contamination.
Finally, the titania disc was again subjected to irradiation with UV light in a dark
room communicated with the ambient air for an hour, at a UV intensity of 0.5
mW/cm.sup.2 and the absorption spectrum was detected which is shown in the graphs
of FIGS. 20A and 20B by the curve #5. As shown in the graphs, no change was
observed in the absorption at wavenumber 3690 cm.sup.-1, whereas the absorption at
wavenumber 3300 cm.sup.-1 is remarkably increased, with the absorption at
wavenumber 1640 cm.sup.-1 being increased. It will therefore be noted that as a result
of re-irradiation with UV light, the amount of chemisorbed water remained unchanged
but the amount of water was increased. It is presumed that, if the specimen were made
in the form of a titania thin film, the contact angle with water would be decreased
upon UV irradiation.
Experiment 2
First, the titania disc immediately after press forming was subjected to the infrared
spectroscopic analysis. The absorption spectrum detected is shown in the graphs of
FIGS. 21A and 21B by the curve #1.
Then, the titania disc was subjected to irradiation with UV light for one hour, at a UV
intensity of 0.5 mW/cm.sup.2 and the absorption spectrum was detected which is
shown in the graphs of FIGS. 21A and 21B by the curve #2.
The disc was further subjected to irradiation with UV light at the same UV intensity
for additional one hour (total 2 hours), further additional one hour (total 3 hours), and
further additional 2 hours (total 5 hours) and the absorption spectra detected at the end
of irradiation are shown in FIGS. 22A and 22B by the curve #3, #4 and #5,
respectively.
As will be understood upon comparison of the #1 spectrum with the #2 spectrum,
both the amount of chemisorbed water and the amount of physisorbed water were
increased as the disc was subjected for the first time to UV irradiation. During the first
irradiation, the amount of adherent carbonyl compounds was slightly increased.
Presumably, the contact angle with water would be decreased in response to UV
irradiation if the specimen were made in the form of a titania thin film.
After the disc was subjected to UV irradiation for further one hour (total 2 hours), the
amount of chemisorbed water was slightly decreased but the amount of physisorbed
water remained unchanged, as shown by the #2 and #3 spectra. The amount of
adherent carbonyl compounds was slightly increased. It is considered that the absence
of any change in the amount of physisorbed water is due to saturation of the
physisorbed water. It is presumed that the contact angle with water would remain
unchanged if the specimen were made in the form of a titania thin film.
As will be noted from the #4 and #5 spectra, UV irradiation for further one hour (total
3 hours) and for further 2 hours (total 5 hours) resulted in a further slight decrease in
the amount of chemisorbed water, with the amount of physisorbed water remained
unchanged. The amount of adhered carbonyl compounds was increased. It is
considered that the contact angle with water would remain unchanged if the UV
irradiation were carried out on a specimen made in the form of a titania thin film.
Experiment 3
This experiment is similar to Experiment 1 in many respects and the major difference
resides in that the UV intensity was decreased.
First, the titania disc immediately after press forming was subjected to the infrared
spectroscopic analysis. The detected absorption spectrum is shown by the curve #1 in
the graphs of FIGS. 23A and 23B. Then, the disc was placed for 34 hours in a dark
room communicated with the ambient air and thereafter the absorption spectrum was
detected which is shown by the curve #2 in the graphs of FIGS. 23A and 23B. Then,
the titania disc placed in the same dark room was subjected to irradiation with UV
light for 2 hours, at a UV intensity of 0.024 mW/cm.sup.2 and the absorption
spectrum was detected, the detected spectrum being indicated by the curve #3 in the
graphs of FIGS. 23A and 23B.
As will be understood from the graphs, both the amount of chemisorbed water and the
amount of physisorbed water were decreased as the disc was placed in a dark room in
the presence of ambient moisture. As the amount of carbonyl compounds adhered to
the specimen was increased, it is presumed that the contact angle with water would be
increased if a specimen made in the form of a titania thin film were used.
It will be noted that in response to UV irradiation the amount of chemisorbed water
was slightly increased and the amount of physisorbed water was increased to again
attain to the initial level. During UV irradiation, the amount of adherent carbonyl
compounds was slightly increased. It is presumed that the contact angle with water
would be increased during UV irradiation if a specimen made in the form of a titania
thin film were used.
Evaluation of the Test Results
To facilitate comparison, the results of Experiments 1-3 are summarized in Table 13
below.
Contact
Chemisorbed Physisorbed Carbonyl
Experiment
Angle w/w
Water
Water
Compound
Experiment 1
(0.5 mW/cm.sup.2)
dark room
increased
dry air
UV irradiated decreased
dry air
dark room
increased
ambient air
UV irradiated decreased
ambient air
Experiment 2
(0.5 mW/cm.sup.2)
UV irradiated decreased
(1 h)
UV irradiated unchanged
(2 h)
UV irradiated unchanged
(3 h)
UV irradiated unchanged
(5 h)
Experiment 3
(0.024 mW/
cm.sup.2)
dark room
increased
ambient air
UV irradiated decreased
ambient air
decreased
decreased
increased
almost
restored
slightly
decreased
unchanged
restored
decreased
slightly
decreased
increased
increased
slightly
increased
slightly
decreased
slightly
decreased
slightly
increased
unchanged
slightly
increased
slightly
increased
increased
unchanged
increased
decreased
decreased
increased
slightly
increased
increased
increased
unchanged
unchanged
decreased
As will be best understood from Table 13, the amount of physisorbed water increases
in good response to UV irradiation.
In this regard, it is considered that, as illustrated in the upper part of FIG. 24, in the
crystal face of a crystal of titania forming a titania coating 30, a terminal OH group 32
is bonded to each titanium atom, with a bridging OH group 34 being bonded to a pair
of adjacent titanium atoms, these OH groups 32 and 34 forming a layer of
chemisorbed water. It is considered that, upon irradiation with UV light in the
presence of ambient moisture, molecules of water in the ambient air are physically
adsorbed by way of hydrogen bond 36 onto the hydrogen atoms of the terminal and
bridging OH groups to thereby form a layer of physisorbed water 38, as illustrated in
the lower part of FIG. 24.
As the amount of physisorbed water increases in good response to UV irradiation as
described before, Example 42 demonstrates that formation of a layer of physisorbed
water 38 is induced by the photocatalytic action of titania. It is believed that because
of the presence of the layer of physisorbed water 38 the surface of titania surface is
rendered hydrophilic.
In contrast, the amount of carbonyl compounds adhered to the surface appears to
increase with increasing duration of contact with ambient air. It is considered that
upon photoexcitation of the photocatalyst the water-wettability of the surface is
increased regardless of increasing amount of adherent carbonyl compounds.
Example 43
Plastic Plate Coated by Photocatalyst-Containing Silicone
A titania-containing coating composition similar to that of Example 18 was applied on
a polyethyleneterephthalate (PET) film (Fuji Xerox, monochromatic PPC film for
OHP, JF-001) and was cured at a temperature of 110.degree. C. to obtain #1 specimen
coated with titania-containing silicone.
Further, an aqueous polyester paint (made by Takamatsu Resin, A-124S) was applied
on another PET film (JF-001) and was cured at 110.degree. C. to form a primer
coating. A titania-containing coating composition similar to that of Example 18 was
then applied on the primer coating and was cured at a temperature of 110.degree. C. to
obtain #2 specimen.
Also, a titania-containing coating composition similar to that of Example 18 was
applied on a polycarbonate (PC) plate and was cured at a temperature of 110.degree.
C. to obtain #3 specimen.
Furthermore, an aqueous polyester paint (A-124S) was applied on another
polycarbonate plate, followed by curing at a temperature of 110.degree. C. to form a
primer coating, and a titania-containing coating composition similar to that of
Example 18 was thereafter applied thereon followed by curing at a temperature of
110.degree. C. to obtain #4 specimen.
The #1-#4 specimens as well as the PET film (JF-001) and polycarbonate plate as
such were subjected to irradiation with UV light, at a UV intensity of 0.6
mW/cm.sup.2 by using a BLB fluorescent lamp and on doing so the variation in
response to time of the contact angle with water of the specimen surface was
measured. The results are shown in Table 14.
TABLE 14
Before
Specimen
#1
2.degree.
#2
2.degree.
#3
3.degree.
#4
2.degree.
PET
1 day
2 days
3 days
10 days
Irradiat. later
later
later
later
71.degree. 44.degree. 32.degree.
7.degree.
73.degree. 35.degree. 16.degree.
3.degree.
66.degree. 55.degree. 27.degree.
9.degree.
65.degree. 53.degree. 36.degree.
18.degree.
70.degree. 72.degree. 74.degree.
73.degree.
90.degree. 86.degree. 88.degree.
87.degree.
60.degree.
PC
89.degree.
As will be apparent from Table 14, the surface of the specimens under question was
hydrophilified as UV irradiation was continued and about 3 days later the surface is
rendered superhydrophilic. As described hereinbefore with reference to Example 14, it
is considered that this is due to the fact that the organic groups bonded to the silicon
atoms of the silicone molecules of the titania-containing silicone layer were
substituted with the hydroxyl groups under the photocatalytic action caused by
photoexcitation.
As is well-known, a UV intensity of 0.6 mW/cm.sup.2 is roughly equal to the
intensity of the UV light contained in the sunlight impinging upon the earth's surface.
It will be noted, accordingly, that superhydrophilification can be achieved simply by
exposing the titania-containing silicone coating to the sunlight.
Example 44
Weathering Test of Photocatalyst-Containing Silicone
The #1 specimen (aluminum substrate coated with silicone) and the #2 specimen
(aluminum substrate coated with titania-containing silicone) of Example 13 were
subjected to a weathering test by using a weathering testing machine (made by Suga
Testing Instruments, Model "WEL-SUN-HC") while irradiating a light from a carbon
arc lamp and spraying rain for 12 minutes per hour and at a temperature of
40.degree.C. The weather resistivity was assessed by the glossiness retention rate
(percentage of the glossiness after testing to the initial glossiness). The results are
shown in Table 15.
TABLE 15
Specimen
#1
#2
500 hrs
91
99
1000 hrs
95
100
3000 hrs
90
98
As will be apparent from Table 15, the glossiness retention rate remained roughly the
same regardless of the presence or absence of titania. This indicates that the siloxane
bonds forming the main chain of the silicone molecule were not broken by the
photocatalytic action of titania. It is therefore considered that the weather resistivity of
silicone is not affected even after the organic groups bonded to the silicon atoms of
the silicone molecules are substituted with the hydroxyl groups.
While the present invention has been described herein with reference to the specific
embodiments thereof, it is contemplated that the invention is not limited thereby and
various modifications and alterations may be made therein without departing from the
scope of the invention. Furthermore, the present invention may be applied for various
purposes and fields other than the aforesaid. For example, a superhydrophilified
surface may be utilized to prevent air bubbles from adhering to an underwater surface.
Also, the superhydrophilified surface may be used to form and maintain a uniform
film of water. Moreover, in view of an excellent affinity for vital tissues and organs,
the superhydrophilic photocatalytic coating may be utilized in the medical fields such
as contact lens, artificial organs, catheters, and anti-thrombotic materials.
(4
United States Patent
Boire ,
of
4)
6,680,135
et al.
January 20, 2004
Substrate with a photocatalytic coating
Abstract
The subject of the invention is a glass-, ceramic- or vitroceramic-based substrate (1)
provided on at least part of at least one of its faces with a coating (3) with a photocatalytic
property containing at least partially crystalline titanium oxide. It also relates to the
applications of such a substrate and to its method of preparation.
Inventors: Boire; Philippe (Paris, FR); Talpaert; Xavier (Paris, FR)
Assignee: Saint-Gobain Glass France (Paris, FR)
Appl. No.: 079484
Filed:
February 22, 2002
Foreign Application Priority Data
Sep 15, 1996[FR]
95 10839
Current
U.S.
Class:
428/702; 428/336; 428/428; 428/432; 428/450; 428/469; 428/496; 428/523;
428/632; 428/687
Intern'l
Class:
B32B 015/04; B32B 017/06; G03C 001/725; G03C 001/76
Field of 428/432,433,434,632,633,660,687,472,472.1,701,702,937,428,450,469,699,332,336
430/270.1,496,271.1,523,272.1,273.1
Search:
References Cited [Referenced By]
U.S. Patent Documents
3630796
Dec., 1971
Yokozawa et al.
156/17.
4017661
Apr., 1977
Gillery
428/412.
4112142
Sep., 1978
Schroder et al.
427/166.
4238276
Dec., 1980
Kinugawa et al.
156/634.
4485146
Nov., 1984
Mizuhashi et al.
4544470
Oct., 1985
Hetrick
4888038
Dec., 1989
Herrington et al.
65/114.
4892712
Jan., 1990
Robertson et al.
422/186.
4898789
Feb., 1990
Finley.
4997576
Mar., 1991
Heller et al.
5028568
Jul., 1991
Anderson et al.
501/12.
5032241
Jul., 1991
Robertson et al.
204/157.
5035784
Jul., 1991
Anderson et al.
204/158.
5165972
Nov., 1992
Porter.
5304394
Apr., 1994
Sauvinet et al.
5308805
May., 1994
Baker et al.
5342676
Aug., 1994
Zagdoun.
5348805
Sep., 1994
Zagdoun et al.
5368892
Nov., 1994
Berquier
427/299.
5389427
Feb., 1995
Berquier
428/210.
5478783
Dec., 1995
Higby et al.
5505989
Apr., 1996
Jenkinson
427/166.
5514454
May., 1996
Boire et al.
428/216.
5525406
Jun., 1996
Goodman et al.
428/216.
5547823
Aug., 1996
Murasawa et al.
430/531.
5580364
Dec., 1996
Goodman et al.
65/60.
5584169
Dec., 1996
Ikehara
204/248.
427/166.
501/71.
501/27.
502/242.
5616532
Apr., 1997
Heller et al.
502/242.
5618579
Apr., 1997
Boire et al.
427/166.
5698262
Dec., 1997
Soubeyrand et al.
427/255.
5735922
Apr., 1998
Woodward et al.
65/104.
5745291
Apr., 1998
Jenkinson
5749931
May., 1998
Goodman et al.
65/60.
5751484
May., 1998
Goodman et al.
359/512.
5755845
May., 1998
Woodward et al.
65/102.
5764415
Jun., 1998
Nelson et al.
359/584.
5773086
Jun., 1998
McCurdy et al.
472/255.
5811192
Sep., 1998
Takahama et al.
428/432.
5853866
Dec., 1998
Watanabe et al.
428/312.
5869187
Feb., 1999
Nakamura et al.
428/428.
5939201
Aug., 1999
Boire et al.
428/432.
5961843
Oct., 1999
Hayakawa et al.
210/748.
6001462
Dec., 1999
Purvis et al.
428/215.
6013372
Jan., 2000
Hayakawa et al.
428/411.
6027766
Feb., 2000
Greenberg et al.
427/226.
6027797
Feb., 2000
Watanabe et al.
428/312.
6037289
Mar., 2000
Chopin et al.
6045896
Apr., 2000
Boire et al.
428/216.
6054227
Apr., 2000
Greenberg et al.
428/701.
6068914
May., 2000
Boire et al.
428/216.
6090489
Jul., 2000
Hayakawa et al.
428/409.
6103360
Aug., 2000
Caldwell et al.
428/323.
6103363
Aug., 2000
Boire et al.
428/325.
6106955
Aug., 2000
Ogawa et al.
428/469.
6210779
Apr., 2001
Watanabe et al.
6228480
May., 2001
Kimura et al.
428/328.
6238738
May., 2001
McCurdy
427/255.
6294246
Sep., 2001
Watanabe et al.
6294247
Sep., 2001
Watanabe et al.
6322881
Nov., 2001
Boire et al.
359/586.
502/2.
432/216.
6326079
Dec., 2001
Philippe et al.
428/325.
6387844
May., 2002
Fujishima et al.
502/350.
Foreign Patent Documents
0 071 865
Feb., 1983
EP.
0 348 185
Dec., 1989
EP.
489 621
Jun., 1992
EP.
0 544 577
Jun., 1993
EP.
0 581 216
Feb., 1994
EP.
A 581 216
Feb., 1994
EP.
590 477
Apr., 1994
EP.
633 064
Jan., 1995
EP.
636 702
Feb., 1995
EP.
650 938
May., 1995
EP.
675 086
Oct., 1995
EP.
737 513
Oct., 1996
EP.
816 466
Jan., 1998
EP.
2031756
Apr., 1980
GB.
2 320 499
Jun., 1998
GB.
2 320503
Jun., 1998
GB.
2 324098
Oct., 1998
GB.
2 355 273
Apr., 2001
GB.
5-3149281
Dec., 1978
JP.
91042/1986
May., 1986
JP.
63-100042
May., 1988
JP.
5-302173
Nov., 1993
JP.
7-99425
Mar., 1995
JP.
7-117600
Apr., 1995
JP.
7-182019
Jun., 1995
JP.
7-182020
Jun., 1995
JP.
7-205019
Jul., 1995
JP.
8-119673
May., 1996
JP.
8-164334
Jun., 1996
JP.
8-313705
Nov., 1996
JP.
9-173783
Jul., 1997
JP.
9-227157
Sep., 1997
JP.
9-227158
Sep., 1997
JP.
9-235140
Sep., 1997
JP.
9-241037
Feb., 1999
JP.
WO 95/15816
Jun., 1995
WO.
WO 96/13327
May., 1996
WO.
WO 96/29375
Sep., 1996
WO.
WO 97/07069
Feb., 1997
WO.
WO 97/10186
Mar., 1997
WO.
WO 98/06510
Feb., 1998
WO.
WO 98/06675
Feb., 1998
WO.
WO 00/75087
Dec., 2000
WO.
WO 01/10790
Feb., 2001
WO.
WO 01/72652
Oct., 2001
WO.
Other References
Opposition filed by Glaverbel (no date).
Opposition filed by Pilkington PLC (no date).
Opposition filed by Toto LTD. (no date).
Opposition filed by Sternagel, Fleischer, Godemeyer, Aug. 2002.
Pt-TiO.sub.2 Thin Films on Glass Substrates as Efficient Photocatalysts,
Journal of Materials Science, 24 (1989), pp. 243-246. (no month).
Preparation of TiO.sub.2 Fine Particles Supported on Silica Gel as
Photocatalyst, Yasumori et al., Journal of the Ceramic Society of Japan, 102
(1994). (Aug.).
Photocatalytic Properties of TiO.sub.2, Wold, Chem. Mater., 1993, 5, pp.
280-283. (no month).
Kristallstruktur und Optische Eigenshaften von Dunnen Organogenen
Titanoxyd-Schichten Auf Glasunterlagen [Crystal Structure and Optical
Properties of Thin Organogenic Titanium Oxide Layers on Glass Substrates],
Bach et al., Thin Solid Films I (1967/68), pp. 255-276, and English
translation (no month).
The Effect of Substrate Temperature on the Properties of Sputtered Titanium
Oxide Films, Meng et al., Applied Surface Science 65/66 (1993) pp. 235-239.
(no month).
Sol-Gel-Derived TiO.sub.2 Film Semiconductor Electrode for Photocleavage
of Water, Yoko et al., J. Electrochem. Soc., vol. 138(8), Aug. 1991, pp.
2279-2284.
Dip-Coating of TiO.sub.2 Films Using a Sol Derived from Ti(O-iPr).sub.4
-diethamolamine-H.sub.2 O-i-PrOH System, Takahashi et al., Journal of
Materials Science 23 (1988, pp. 2259-2266. (no month).
A Structural Investigation of Titanium Dioxide Photocatalysts, Bickley, et al.,
Journal of Solid State Chemistry 92, 1991, pp. 178-190. (no month).
Highly Transparent and Photoactive TiO2 Thin Film Coated on Glass
Substrate, Fukayama et al., Abstract 735, 187.sup.th Electrochemical Society
Meeting, Mar. 29, 1995.
EP 684,075, Wantanabe et al., Jun. 15, 1995 and the front page of WO
95/15816, Watanabe et al., Jun. 15, 1995, which is an equivalent of EP
684,075 and contains an English abstract.
Oxide Layers Deposited from Organic Solutions, H. Schroeder in Physics of
Thin Films: Advances in Research and Development pp. 105-112, vol. 5,
1969 Academic Press. (no month).
JP 267476/94, Fujishima et al., (no date) publication date not listed, and
Derwent WPIndex abstract; corresponds to EP 737 513A, (submitted
herewith under Tab 17); WO 96/13327 (of record; published on May 9,
1996); and U.S. 6,387,844 (of record).
JPA 63-5301 Matsushita Electric Works (assignee), Jan. 11, 1988, and
Derwent WPIndex abstract.
JPA 63-5304, Matsushita Electric Works (assignee), Jan. 11, 1988, and
Derwent WPIndex abstract.
JPA 7-222928, Chikuni et al., Aug. 22, 1995, and Derwent WPIndex abstract;
equivalent of WO 95/15816 (submitted herewith)) and U.S. 5,853,866 (of
record) 6,210,779 (submitted hereiwth), 6,294,246 (submitted herewith), and
6,294,247 (submitted herewith).
JPA 1-218635, Hitachi LTD (assignee), Feb. 29, 1988, and Derwent
WPIindex abstract.
JPA 7-111104, Fujishima et al., Apr. 25, 1995, and Derwent WPIndex
abstract.
Preparation of Transparent TiO.sub.2 Thin Film Photocatalyst and Its
Photocatalytic Activity, Negishi et al., Chemistry Letters 1995, No. 9, pp.
841-842. (Sep.).
JP-A-5 253 544, Toto LTD (assignee), Oct. 5, 1995, and Derwent WPIndex
abstract.
JP-A-6-65012, Agency of Ind. Sci. & Technology (assignee), Mar. 8, 1994,
and Derwent WPIndex abstract.
Electrical and Electrochemical Properties of TiO.sub.2 films Grown by
Organometallic Chemical Vapour Deposition, Takahashi et al., J. Chem. Soc.,
Faraday Trans 1, 1982, 78, pp. 2563-2571. (no month).
Apr. 3, 2000 Letter from Mrs.Colette Ward, Patent Litigation Enquiries,
British Library.
Table showing values of roughness (Root Mean Square) of various coated
glass samples available tot the public at the priority date of EP 850 204. (no
date).
Masanari Takahashi et al., "Pt-TiO.sub.2 Thin Films on Glass Substrates as
Efficient Photocatalysts," Journal of Materials Science, 24 (1989) pp.
243-246, (Jan.).
S. Fukuyama et al., Highly Transparent and Photoactive TiO.sub.2 Thin Film
Coated on Glass Substrate, Abstract No. 735, pp. 1102-1103, 187.sup.th
Electrochemical Society Meeting, Reno, NV, May 21-26, 1995, and attached
facsimile transmission from The British Library indicating that the date of
availability for public use was Mar. 29, 1995.
D.R. Uhlmann, "Glass: Science and Technology," vol. 2, Processing I, pp.
253-283, 1984, (no month).
GlassFAQs, GlassFACTS.com, p. 1-5. (no date).
JP 63-100042; May 1988. Abstract Only, Derwent AN 88-158990, Glass
Article Difficult Soil Coating Thin Titanium DI Oxide Coating Contain
Platinum@ Rhodium Palladium@.
Chemical Abstracts,, 116: 89812a, Sokolov, et al., "Selective Activation of
Smooth Surfaces of Glass and Ceramic Articles Before Chemical
Metalization," Abstract Only. SU 166304; Jul. 1991.
International Search Report for PCT/FR96/01421, Jan. 1997.
International Preliminary Examination Report for PCT/FR96/01421, May
1997.
Robert J. Good et al., The Modern Theory of Contact Angles and the
Hydrogen Bond Components of Surface Energies, in Modern Approaches to
Wettability, Theory and Applications, pp 1-3, Schrader et al., Eds. (no date).
H.H. Dunken, Glass Surfaces, Treatise on Materials Science and Technology,
vol. 22, pp. 1-75, 1982. (no month).
Toshiya Watanabe et al., Photocatalytic Activity of TiO2 Thin Film under
Room Light, in Photocatalytic Purification and Treatment of Water and Air,
pp. 747-751, 1993, Ollis et al., Eds. (no month).
The Japan Times, May 21, 2002, Tuesday, Race for Technology, pp. 2-5,
from LexisNexis.
P. Chartier, Verre, Glass Institute, vol. 3, No. 3--Jun. 1997, pp. 5-12, French
document with English Translation.
U.S. patent application Ser. No. 09/486,719, filed Aug. 2, 2000, pending.
U.S. patent application Ser. No. 09/923,353, filed Aug. 8, 2001, pending.
U.S. patent application Ser. No. 09/940,499, filed Aug. 29. 2001, pending.
U.S. patent application Ser. No. 10/000,503, filed Dec. 4, 2001, pending.
U.S. patent application Ser. No. 10/079,484, filed Feb. 22, 2002, pending.
U.S. patent application Ser. No. 10/079,483, filed Feb. 22, 2002, pending.
U.S. patent application Ser. No. 10/079,533, filed Feb. 22, 2002, pending.
U.S. patent application Ser. No. 09/719,153, filed Mar. 16, 2001, pending.
U.S. patent application Ser. No. 10/116,164, filed Apr. 5, 2002, pending.
U.S. patent application Ser. No. 10/220,268, filed Sep. 6, 2002, pending.
Primary Examiner: LaVilla; Michael
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt, P.C.
Parent Case Text
This application is a Continuation of application Ser. No. 10/000,503, filed on Dec. 4,
2001, now abandoned, which is a continuation of application Ser. No. 09/615,910,
filed Jul. 13, 2000, now U.S. Pat. No. 6,326,079, which is a continuation of
application Ser. No. 09/029,855, filed on May 28, 1998, now U.S. Pat. No. 6,103,363,
which was originally filed as PCT/FR96/01421 on Sep. 13, 1996.
Claims
What is claimed is:
1. A self-cleaning article of manufacture, comprising:
a glass-, ceramic-, or vitroceramic-based substrate having at least one surface over
which organic contaminants are expected to accumulate,
a photocatalytically-activated self-cleaning coating of a photocatalytically-activated
self-cleaning and at least partially crystalline titanium oxide deposited on said at least
one surface by sol-gel or liquid spray pyrolysis, and
a barrier layer with respect to alkali metals between said at least one surface and the
coating which comprises a member selected from the group consisting of silicon
nitride, silicon oxynitride, silicon oxycarbide, Al.sub.2 O.sub.3 :F, and aluminum
nitride.
2. The self-cleaning article of manufacture of claim 1, wherein the crystalline form of
the titanium dioxide is selected from the group consisting of anatase, rutile, and
combinations of anatase and rutile.
3. The self-cleaning article of manufacture of claim 1, wherein the self-cleaning
coating has a thickness between 5 nm and 1 micron.
4. The self-cleaning article of manufacture of claim 1, wherein the
photocatalytically-activated self-cleaning coating is photocatalytically-activated to be
self-cleaning upon irradiation with ultraviolet radiation.
5. The self-cleaning article of manufacture of claim 1, which further comprises one or
more ultraviolet lamps.
6. The self-cleaning article of manufacture of claim 1, wherein the barrier layer
comprises silicon nitride.
7. The self-cleaning article of manufacture of claim 1, wherein the barrier layer
comprises silicon oxynitride.
8. The self-cleaning article of manufacture of claim 1, wherein the barrier layer
comprises silicon oxycarbide.
9. The self-cleaning article of manufacture of claim 1, wherein the barrier layer
comprises Al.sub.2 O.sub.3 :F.
10. The self-cleaning article of manufacture of claim 1, wherein the barrier layer
comprises aluminum nitride.
Description
The invention relates to glass-, ceramic- or vitroceramic-based substrates, more
particularly made of glass, in particular transparent substrates, which are furnished
with coatings with photocatalytic properties, for the purpose of manufacturing glazing
for various applications, such as utilitarian glazing or glazing for vehicles or for
buildings.
There is an increasing search to functionalize glazing by depositing at the surface
thereof thin layers intended to confer thereon a specific property according to the
targeted application. Thus, there exist layers with an optical function, such as
so-called anti-glare layers composed of a stack of layers alternatively with high or low
refractive indices. For an anti-static function or a heating function of the anti-icer type,
it is also possible to provide electrically conducting thin layers, for example based on
metal or doped metal oxide. For an anti-solar or low-emissivity thermal function for
example, thin layers made of metal of the silver type or based on metal oxide or
nitride may be used. To obtain a "rain-repellent" effect, it is possible to provide layers
with a hydrophobic nature, for example based on fluorinated organosilane and the like.
However, there still exists a need for a substrate, particularly a glazing, which could
be described as "dirt-repellent", that is to say targeted at the permanence over time of
the appearance and surface properties, and which makes it possible in particular to
render cleaning less frequent and/or to improve the visibility, by succeeding in
removing, as they are formed, the dirty marks which are gradually deposited at the
surface of a substrate, in particular dirty marks of organic origin, such as finger marks
or volatile organic products present in the atmosphere, or even dirty marks of
condensation type.
In point of fact, it is known that there exist certain semiconductive materials based on
metal oxides which are capable, under the effect of radiation of appropriate
wavelength, of initiating radical reactions which cause the oxidation of organic
products; they are generally referred to as "photocatalytic" or alternatively
"photoreactive" materials.
The aim of the invention is then to develop photocatalytic coatings on a substrate
which exhibit a marked "dirt-repellent" effect with respect to the substrate and which
can be manufactured industrially.
The object of the invention is a glass-, ceramic- or vitroceramic-based substrate, in
particular made of glass and transparent, provided on at least part of at least one of its
faces with a coating with a photocatalytic property containing at least partially
crystalline titanium oxide. The titanium oxide is preferably crystallized "in situ"
during the formation of the coating on the substrate.
Titanium oxide is in fact one of the semiconductors which, under the effect of light in
the visible or ultraviolet range, degrade organic products which are deposited at their
surface. The choice of titanium oxide to manufacture a glazing with a "dirt-repellent"
effect is thus particularly indicated, all the more so since this oxide exhibits good
mechanical strength and good chemical resistance: for long-term effectiveness, it is
obviously important for the coating to retain its integrity, even if it is directly exposed
to numerous attacks, in particular during the fitting of the glazing on a building site
(building) or on a production line (vehicle) which involves repeated handlings by
mechanical or pneumatic prehension means, and also once the glazing is in place,
with risks of abrasion (windscreen wipers, abrasive rag) and of contact with
aggressive chemicals (atmospheric pollutants of SO.sub.2 type, cleaning product, and
the like).
The choice has fallen, in addition, on a titanium oxide which is at least partially
crystalline because it has been shown that it had a much better performance in terms
of photocatalytic property than amorphous titanium oxide. It is preferably crystallized
in the anatase form, in the rutile form or in the form of a mixture of anatase and rutile,
with a degree of crystallization of at least 25%, in particular of approximately 30 to
80%, in particular close to the surface (the property being rather a surface property).
(Degree of crystallization is understood to mean the amount by weight of crystalline
TiO.sub.2 with respect to the total amount by weight of TiO.sub.2 in the coating).
It has also been possible to observe, in particular in the case of crystallization in
anatase form, that the orientation of the TiO.sub.2 crystals growing on the substrate
had an effect on the photocatalytic behaviour of the oxide: there exists a favoured
orientation (1, 1, 0) which markedly promotes photocatalysis.
The coating is advantageously manufactured so that the crystalline titanium oxide
which it contains is in the form of "crystallites", at least close to the surface, that is to
say of monocrystals, having an average size of between 0.5 and 100 nm, preferably 1
to 50 nm, in particular 10 to 40 nm, more particularly between 20 and 30 nm. It is in
fact in this size range that titanium oxide appears to have an optimum photocatalytic
effect, probably because the crystallites of this size develop a high active surface area.
As will be seen in more detail subsequently, it is possible to obtain the coating based
on titanium oxide in many of ways:
by decomposition of titanium precursors (pyrolysis techniques: liquid pyrolysis,
powder pyrolysis, pyrolysis in the vapour phase, known as CVD (Chemical Vapour
Deposition), or techniques associated with the sol-gel: dipping, cell coating, and the
like),
by a vacuum technique (reactive or non-reactive cathodic sputtering).
The coating can also contain, in addition to the crystalline titanium oxide, at least one
other type of inorganic material, in particular in the form of an amorphous or partially
crystalline oxide, for example a silicon oxide (or mixture of oxides), titanium oxide,
tin oxide, zirconium oxide or aluminium oxide. This inorganic material can also
participate in the photocatalytic effect of the crystalline titanium oxide, by itself
exhibiting to a certain extent a photocatalytic effect, even a weak effect compared
with that of crystalline TiO.sub.2, which is the case with tin oxide or amorphous
titanium oxide.
A layer of "mixed" oxide thus combining at least partially crystalline titanium oxide
with at least one other oxide can be advantageous from an optical viewpoint, very
particularly if the other oxide or oxides are chosen with a lower index than that of
TiO.sub.2 : by lowering the "overall" refractive index of the coating, it is possible to
vary the light reflection of the substrate provided with the coating, in particular to
lower this reflection. This is the case if, for example, a layer made of TiO.sub.2
/Al.sub.2 O.sub.3, a method for the preparation of which is described in Patent
EP-0,465,309, or made of TiO.sub.2 /SiO.sub.2 is chosen. It is necessary, of course,
for the coating to contain however a TiO.sub.2 content which is sufficient to maintain
a significant photocatalytic activity. It is thus considered that it is preferable for the
coating to contain at least 40% by weight, in particular at least 50% by weight, of
TiO.sub.2 with respect to the total weight of oxide(s) in the coating.
It is also possible to choose to superimpose, with the coating according to the
invention, a grafted oleophobic and/or hydrophobic layer which is stable or resistant
to photocatalysis, for example based on the fluorinated organosilane described in
Patents U.S. Pat. No. 5,368,892 and U.S. Pat. No. 5,389,427 and on the
perfluoroalkylsilane described in Patent Application FR-94/08734 of Jul. 13, 1994,
published under the number FR-2,722,493 and corresponding to European Patent
EP-0,692,463, in particular of formula:
CF.sub.3 -(CF.sub.2).sub.n -(CH2).sub.m -SiX3
in which n is from 0 to 12, m is from 2 to 5 and X is a hydrolysable group.
To amplify the photocatalytic effect of the titanium oxide of the coating according to
the invention, it is possible first of all to increase the absorption band of the coating,
by incorporating other particles in the coating, in particular metal particles or particles
based on cadmium, tin, tungsten, zinc, cerium or zirconium.
It is also possible to increase the number of charge carriers by doping the crystal
lattice of the titanium oxide by inserting therein at least one of the following metal
elements: niobium, tantalum, iron, bismuth, cobalt, nickel, copper, ruthenium, cerium
or molybdenum.
This doping can also be carried out by surface doping only of the titanium oxide or of
the combined coating, surface doping carried out by covering at least part of the
coating with a layer of metal oxides or salts, the metal being chosen from iron, copper,
ruthenium, cerium, molybdenum, vanadium and bismuth.
Finally, the photocatalytic phenomenon can be accentuated by increasing the yield
and/or the kinetics of the photocatalytic reactions, by covering the titanium oxide, or
at least part of the coating which incorporates it, with a noble metal in the form of a
thin layer of the platinum, rhodium, silver or palladium type.
Such a catalyst, for example deposited by a vacuum technique, in fact makes it
possible to increase the number and/or the lifetime of the radical entities created by
the titanium oxide and thus to promote the chain reactions leading to the degradation
of organic products.
In an entirely surprising way, the coating exhibits in fact not one property but two, as
soon as it is exposed to appropriate radiation, as in the visible and/or ultraviolet field,
such as sunlight: by the presence of photocatalytic titanium oxide, as already seen, it
promotes the gradual disappearance, as they are accumulated, of dirty marks of
organic origin, their degradation being caused by a radical oxidation process.
Inorganic dirty marks are not, themselves, degraded by this process: they therefore
remain on the surface and, except for a degree of crystallization, they are in part easily
removed since they no longer have any reason to adhere to the surface, the binding
organic agents being degraded by photocatalysis.
However, the coating of the invention, which is permanently self-cleaning, also
preferably exhibits an external surface with a pronounced hydrophilic and/or
oleophilic nature which results in three very advantageous effects:
a hydrophilic nature makes possible complete wetting of the water which can be
deposited on the coating. When a water condensation phenomenon takes place,
instead of a deposit of water droplets in the form of condensation which hampers
visibility, there is in fact a continuous thin film of water which is formed on the
surface of the coating and which is entirely transparent. This "anti-condensation"
effect is in particular demonstrated by the measurement of a contact angle with water
of less than 5.degree. after exposure to light, and
after running of water, in particular of rain, over a surface which has not been treated
with a photocatalytic layer, many drops of rainwater remain stuck to the surface and
leave, once evaporated, unattractive and troublesome marks, mainly of inorganic
origin. Indeed, a surface exposed to the surrounding air is rapidly covered by a layer
of dirty marks which limits the wetting thereof by water. These dirty marks are in
addition to the other dirty marks, in particular inorganic marks (crystallizations and
the like), contributed by the atmosphere in which the glazing bathes. In the case of a
photoreactive surface, these inorganic dirty marks are not directly degraded by
photocatalysis. In fact, they are in very large part removed by virtue of the hydrophilic
nature induced by the photocatalytic activity. This hydrophilic nature indeed causes
complete spreading of the drops of rain. Evaporation marks are therefore no longer
present. Moreover, the other inorganic dirty marks present on the surface are washed,
or redissolved in the case of crystallization, by the water film and are thus in large
part removed. An "inorganic dirt-repellent" effect is obtained, induced in particular by
rain,
in conjunction with a hydrophilic nature, the coating can also exhibit an oleophilic
nature which makes possible the "wetting" of the organic dirty marks which, as with
water, then tend to be deposited on the coating in the form of a continuous film which
is less visible than highly localized "stains". An "organic dirt-repellent" effect is thus
obtained which operates in two ways: as soon as it is deposited on the coating, the
dirty mark is already not very visible. Subsequently, it gradually disappears by radical
degradation initiated by photocatalysis.
The coating can be chosen with a more or less smooth surface. A degree of roughness
can indeed be advantageous:
it makes it possible to develop a greater active photocatalytic surface area and thus
induces a greater photocatalytic activity,
it has a direct effect on the wetting. The roughness in fact enhances the wetting
properties. A smooth hydophilic surface will be even more hydrophilic once rendered
rough. "Roughness" is understood to mean, in this instance, both the surface
roughness and the roughness induced by a porosity of the layer in at least a portion of
its thickness.
The above effects will be all the more marked when the coating is porous and rough,
resulting in a superhydrophilic effect for rough photoreactive surfaces. However,
when exaggerated, the roughness can be penalizing by promoting incrustation or
accumulation of dirty marks and/or by bringing about the appearance of an optically
unacceptable level of fuzziness.
It has thus proved to be advantageous to adapt the method for deposition of TiO.sub.2
-based coatings so that they exhibit a roughness of approximately 2 to 20 nm,
preferably of 5 to 15 nm, this roughness being evaluated by atomic force microscopy,
by measurement of the value of the root mean square or RMS over a surface area of 1
square micrometre. With such roughnesses, the coatings exhibit a hydrophilic nature
which is reflected by a contact angle with water which can be less than 1.degree.. It
has also been found that it is advantageous to promote a degree of porosity in the
thickness of the coating. Thus, if the coating consists only of TiO.sub.2, it preferably
exhibits a porosity of the order of 65 to 99%, in particular of 70 to 90%, the porosity
being defined in this instance indirectly by the percentage of the theoretical relative
density of TiO.sub.2, which is approximately 3.8. One means for promoting such a
porosity comprises, for example, the deposition of the coating by a technique of the
sol-gel type involving the decomposition of materials of organometallic type: an
organic polymer of polyethylene glycol PEG type can then be introduced into the
solution, in addition to the organometallic precursor(s): on curing the layer by heating,
the PEG is burnt off, which brings about or accentuates a degree of porosity in the
thickness of the layer.
The thickness of the coating according to the invention is variable; it is preferably
between 5 nm and 1 micron, in particular between 5 and 100 nm, in particular
between 10 and 80 nm, or between 20 and 50 nm. In fact, the choice of the thickness
can depend on various parameters, in particular on the targeted application of the
substrate of the glazing type or alternatively on the size of the TiO.sub.2 crystallites in
the coating or on the presence of a high proportion of alkali metals in the substrate.
It is possible to arrange, between the substrate and the coating according to the
invention, one or a number of other thin layers with a different or complementary
function to that of the coating. It can concern, in particular, layers with an anti-static,
thermal or optical function or promoting the crystalline growth of TiO.sub.2 in the
anatase or rutile form or of layers forming a barrier to the migration of certain
elements originating from the substrate, in particular forming a barrier to alkali metals
and very particularly to sodium ions when the substrate is made of glass.
It is also possible to envisage a stack of alternating "anti-glare" layers of thin layers
with high and low indices, the coating according to the invention constituting the final
layer of the stack. In this case, it is preferable for the coating to have a relatively low
refractive index, which is the case when it is composed of a mixed oxide of titanium
and of silicon.
The layer with an anti-static and/or thermal function (heating by providing it with
power leads, low-emissive, anti-solar, and the like) can in particular be chosen based
on a conductive material of the metal type, such as silver, or of the doped metal oxide
type, such as indium oxide doped with tin ITO, tin oxide doped with a halogen of the
fluorine type SnO.sub.2: F or with antimony SnO.sub.2 :Sb or zinc oxide doped with
indium ZnO:In, with fluorine ZnO:F, with aluminium ZnO:Al or with tin ZnO:Sn. It
can also concern metal oxides which are stoichiometrically deficient in oxygen, such
as SnO.sub.2-x or ZnO.sub.2-x with .times.<2.
The layer with an anti-static function preferably has a surface resistance value of 20 to
1000 ohms.square. Provision can be made for furnishing it with power leads in order
to polarize it (feeding voltages for example of between 5 and 100 V). This controlled
polarization makes it possible in particular to control the deposition of dust with a size
of the order of a millimetre capable of being deposited on the coating, in particular
dry dust which adheres only by an electrostatic effect: by suddenly reversing the
polarization of the layer, this dust is "ejected".
The thin layer with an optical function can be chosen in order to decrease the light
reflection and/or to render more neutral the colour in reflection of the substrate. In this
case, it preferably exhibits a refractive index intermediate between that of the coating
and that of the substrate and an appropriate optical thickness and can be composed of
an oxide or of a mixture of oxides of the aluminium oxide Al.sub.2 O.sub.3, tin oxide
SnO.sub.2, indium oxide In.sub.2 O.sub.3 or silicon oxycarbide or oxynitride type. In
order to obtain maximum attenuation of the colour in reflection, it is preferable for
this thin layer to exhibit a refractive index close to the square root of the product of
the squares of the refractive indices of the two materials which frame it, that is to say
the substrate and the coating according to the invention. In the same way, it is
advantageous to choose its optical thickness (that is to say the product of its geometric
thickness and of its refractive index) similar to lambda/4, lambda being approximately
the average wavelength in the visible, in particular from approximately 500 to 550 nm.
The thin layer with a barrier function with respect to alkali metals can be in particular
chosen based on silicon oxide, nitride, oxynitride or oxycarbide, made of aluminium
oxide containing fluorine Al.sub.2 O.sub.3 :F or alternatively made of aluminium
nitride. In fact, it has proved to be useful when the substrate is made of glass, because
the migration of sodium ions into the coating according to the invention can, under
certain conditions, detrimentally affect the photocatalytic properties thereof.
The nature of the substrate or of the sublayer furthermore has an additional advantage:
it can promote the crystallization of the photocatalytic layer which is deposited, in
particular in the case of CVD deposition.
Thus, during deposition of TiO.sub.2 by CVD, a crystalline SnO.sub.2 :F sublayer
promotes the growth of TiO.sub.2 mostly in the rutile form, in particular for
deposition temperatures of the order of 400.degree. to 500.degree. C., whereas the
surface of a soda-lime glass or of a silicon oxycarbide sublayer rather induces an
anatase growth, in particular for deposition temperatures of the order of 400.degree. to
600.degree. C.
All these optional thin layers can, in a known way, be deposited by vacuum
techniques of the cathodic sputtering type or by other techniques of the thermal
decomposition type, such as solid, liquid or gas phase pyrolyses. Each of the
abovementioned layers can combine a number of functions but it is also possible to
superimpose them.
Another subject of the invention is "dirt-repellent" (organic and/or inorganic dirty
marks) and/or "anti-condensation" glazing, whether it is monolithic or insulating
multiple units of the double glazing or laminated type, which incorporates the coated
substrates described above.
The invention is thus targeted at the manufacture of glass, ceramic or vitroceramic
products and very particularly at the manufacture of "self-cleaning" glazing. The latter
can advantageously be building glazing, such as double glazing (it is then possible to
arrange the coating "external side" and/or "internal side", that is to say on face 1
and/or on face 4). This proves to be very particularly advantageous for glazing which
is not very accessible to cleaning and/or which needs to be cleaned very frequently,
such as roofing glazing, airport glazing, and the like. It can also relate to vehicle
windows where maintenance of visibility is an essential safety criterion. This coating
can thus be deposited on car windscreens, side windows or rear windows, in particular
on the face of the windows turned towards the inside of the passenger compartment.
This coating can then prevent the formation of condensation and/or remove traces of
dirty finger mark, nicotine or organic material type, the organic material being of the
volatile plasticizing type released by the plastic lining the interior of the passenger
compartment, in particular that of the dashboard (release sometimes known under the
term "fogging"). Other vehicles such as planes or trains can also find it advantageous
to use windows furnished with the coating of the invention.
A number of other applications are possible, in particular for aquarium glass, shop
windows, greenhouses, verandas, or glass used in interior furniture or street furniture
but also mirrors, television screens, the spectacle field or any architectural material of
the facing material, cladding material or roofing material type, such as tiles, and the
like.
The invention thus makes it possible to functionalize these known products by
conferring on them anti-ultraviolet, dirt-repellent, bactericidal, anti-glare, anti-static or
antimicrobial properties and the like.
Another advantageous application of the coating according to the invention consists in
combining it with an electrically controlled variable absorption glazing of the
following types: electrochromic glazing, liquid crystal glazing, optionally with
dichroic dye, glazing containing a system of suspended particles, viologen glazing
and the like. As all these glazing types are generally composed of a plurality of
transparent substrates, between which are arranged the "active" elements, it is then
possible advantageously to arrange the coating on the external face of at least one of
these substrates.
In particular in the case of an electrochromic glazing, when the latter is in the
coloured state, its absorption results in a degree of surface heating which, in fact, is
capable of accelerating the photocatalytic decomposition of the carbonaceous
substances which are deposited on the coating according to the invention. For further
details on the structure of an electrochromic glazing, reference will advantageously be
made to Patent Application EP-A-0,575,207, which describes an electrochromic
laminated double glazing, it being possible for the coating according to the invention
preferably to be positioned on face 1.
Another subject of the invention is the various processes for obtaining the coating
according to the invention. It is possible to use a deposition technique of the pyrolysis
type which is advantageous because it in particular makes possible the continuous
deposition of the coating directly on the float-glass strip when a glass substrate is used.
The pyrolysis can be carried out in the solid phase, from powder(s) of precursor(s) of
the organo-metallic type.
The pyrolysis can be carried out in the liquid phase, from a solution comprising an
organometallic titanium precursor of the titanium chelate and/or titanium alcoholate
type. Such precursors are mixed with at least one other organometallic precursor. For
further details on the nature of the titanium precursor or on the deposition conditions,
reference will be made, for example, to Patents FR-2,310,977 and EP-0,465,309.
The pyrolysis can also be carried out in the vapour phase, which technique is also
denoted under the term of CVD (Chemical Vapour Deposition), from at least one
titanium precursor of the halide type, such as TiCl.sub.4, or titanium alcoholate of the
Ti tetraisopropylate type, Ti(OiPr).sub.4. The crystallization of the layer can
additionally be controlled by the type of sublayer, as mentioned above.
It is also possible to deposit the coating by other techniques, in particular by
techniques in combination with the "sol-gel". Various deposition methods are possible,
such as "dipping", also known as "dip coating", or a deposition using a cell known as
"cell coating". It can also concern a method of deposition by "spray coating" or by
laminar coating, the latter technique being described in detail in Patent Application
WO-94/01598. All these deposition methods in general use a solution comprising at
least one organometallic precursor, in particular titanium of the alcoholate type, which
is thermally decomposed after coating the substrate with the solution on one of its
faces or on both its faces.
It can be advantageous, moreover, to deposit the coating, whatever the deposition
technique envisaged, not in a single step but via at least two successive stages, which
appears to promote the crystallization of titanium oxide throughout the thickness of
the coating when a relatively thick coating is chosen.
Likewise, it is advantageous to subject the coating with a photocatalytic property,
after deposition, to a heat treatment of the annealing type. A heat treatment is essential
for a technique of the sol-gel or laminar coating type in order to decompose the
organometallic precursor(s) to oxide, once the substrate has been coated, and to
improve the resistance to abrasion, which is not the case when a pyrolysis technique is
used, where the precursor decomposes as soon as it comes into contact with the
substrate. In the first case, as in the second, however, a post-deposition heat treatment,
once the TiO.sub.2 has been formed, improves its degree of crystallization. The
chosen treatment temperature can in addition make possible better control of the
degree of crystallization and of the crystalline nature, anatase and/or rutile, of the
oxide.
However, in the case of a substrate made of soda-lime glass, multiple and prolonged
annealings can promote attenuation of the photocatalytic activity because of an
excessive migration of the alkali metals from the substrate towards the photoreactive
layer. The use of a barrier layer between the substrate, if it is made of standard glass,
and the coating, or the choice of a substrate made of glass with an appropriate
composition, or alternatively the choice of a soda-lime glass with a surface from
which alkali metals have been eliminated make it possible to remove this risk.
Other advantageous details and characteristics of the invention emerge from the
description below of non-limiting implementational examples, with the help of the
following figures:
FIG. 1: a cross-section of a glass substrate provided with the coating according to the
invention,
FIG. 2: a diagram of a sol-gel deposition technique, by so-called "dip coating" the
coating,
FIG. 3: a diagram of a so-called "cell coating" deposition technique,
FIG. 4: a diagram of a so-called "spray coating" deposition technique,
FIG. 5: a diagram of a deposition technique by laminar coating.
As represented very diagrammatically in FIG. 1, all the following examples relate to
the deposition of a so-called "dirt-repellent" coating 3, essentially based on titanium
oxide, on a transparent substrate 1.
The substrate 1 is made of clear soda-lime-silica glass with a thickness of 4 mm and a
length and width of 50 cm. It is obvious that the invention is not limited to this
specific type of glass. The glass can in addition not be flat but bent.
Between the coating 3 and the substrate 1 is found a thin optional layer 2, either based
on silicon oxycarbide, written as SiOC, for the purpose of constituting a barrier to the
diffusion of the alkali metals and/or a layer which attenuates light reflection, or based
on tin oxide doped with fluorine SnO.sub.2 :F, for the purpose of constituting an
anti-static and/or low-emissive layer, even with a not very pronounced low-emissive
effect, and/or a layer which attenuates the colour, in particular in reflection.
EXAMPLES 1 TO 3
Examples 1 to 3 relate to a coating 3 deposited using a liquid phase pyrolysis
technique. The operation can be carried out continuously, by using a suitable
distribution nozzle arranged transversely and above the float-glass strip at the outlet of
the float-bath chamber proper. In this instance, the operation is carried out
non-continuously, by using a moveable nozzle arranged opposite the substrate 1
already cut to the dimensions shown, which substrate is first heated in an oven to a
temperature of 400 to 650.degree. C. before progressing a constant speed past the
nozzle spraying at an appropriate solution.
Example 1
In this example, there is no optional layer 2. The coating 3 is deposited using a
solution comprising two organometallic titanium precursors, titanium diisopropoxide
diacetylacetonate and titanium tetraoctyleneglycolate, dissolved in a mixture of two
solvents, the latter being ethyl acetate and isopropanol.
It should be noted that it is also entirely possible to use other precursors of the same
type, in particular other titanium chelates of the titanium acetylacetonate, titanium
(methyl acetoacetato), titanium (ethyl acetoacetato) or alternatively titanium
triethanolaminato or titanium diethanolaminato type.
As soon as the substrate 1 has reached the desired temperature in the oven, i.e. in
particular approximately 500.degree. C., the substrate progresses past the nozzle
which sprays at room temperature, using compressed air, the mixture shown.
A TiO.sub.2 layer with a thickness of approximately 90 nm is then obtained, it being
possible for the thickness to be controlled by the rate of progression of the substrate 1
past the nozzle and/or the temperature of the said substrate. The layer is partially
crystalline in the anatase form.
This layer exhibits excellent mechanical behaviour. Its resistance to abrasion tests is
comparable with that obtained for the surface of the bare glass.
It can be bent and dip coated. It does not exhibit bloom: the scattered light
transmission of the coated substrate is less than 0.6% (measured according to the
D.sub.65 illuminant at 560 nm)
Example 2
Example 1 is repeated but inserting, between the substrate 1 and coating 3, an
SnO.sub.2 :F layer 2 with a thickness of 73 nm. This layer is obtained by powder
pyrolysis from dibutyltin difluoride DBTF. It can also be obtained, in a known way,
by pyrolysis in the liquid or vapour phase, as is for example described in Patent
Application EP-A-0,648,196. In the vapour phase, it is possible in particular to use a
mixture of monobutyltin trichloride and of a fluorinated precursor optionally in
combination with a "mild" oxidant of the H.sub.2 O type.
The index of the layer obtained is approximately 1.9. Its surface resistance is
approximately 50 ohms.
In the preceding Example 1, the coated substrate 1, mounted as a double glazing so
that the coating is on face 1 (with another substrate 1' which is non-coated but of the
same nature and dimensions as the substrate 1 via a 12 mm layer of air), exerts a
colour saturation value in reflection of 26% and a colour saturation value in
transmission of 6.8%.
In this Example 2, the colour saturation in reflection (in the goldens) is only 3.6% and
it is 1.1% in transmission.
Thus, the SnO.sub.2 :F sublayer makes it possible to confer, on the substrate,
anti-static properties due to its electrical conductivity and it also has a favourable
effect on the colorimetry of the substrate, by making its coloration markedly more
"neutral", both in transmission and in reflection, which coloration is caused by the
presence of the titanium oxide coating 3 exhibiting a relatively high refractive index.
It is possible to polarize it by providing it with a suitable electrical supply, in order to
limit the deposition of dust with a relatively large size, of the order of a millimetre.
In addition, this sublayer decreases the diffusion of alkali metals into the
photocatalytic TiO.sub.2 layer. The photocatalytic activity is thus improved.
Example 3
Example 2 is repeated but this time inserting, between substrate 1 and coating 3, a
layer 2 based on silicon oxycarbide with an index of approximately 1.75 and a
thickness of approximately 50 nm, which layer can be obtained by CVD from a
mixture of SiH.sub.4 and ethylene diluted in nitrogen, as described in Patent
Application EP-A-0,518,755. This layer is particularly effective in preventing the
tendency of alkali metals (Na.sup.+, K.sup.+) and of alkaline-earth metals (Ca.sup.++)
originating from the substrate 1 to diffuse towards the coating 3 and thus the
photocatalytic activity is markedly improved. As it has, like SnO.sub.2 :F, a refractive
index intermediate between that of the substrate (1.52) and of the coating 3
(approximately 2.30 to 2.35), it also makes it possible to reduce the intensity of the
coloration of the substrate, both in reflection and in transmission, and overall to
decrease the light reflection value R.sup.L of the said substrate.
The following Examples 4 to 7 relate to depositions by CVD.
EXAMPLES 4 TO 7
Example 4
This example relates to the deposition by CVD of the coating 3 directly on the
substrate 1 using a standard nozzle, such as that represented in the above-mentioned
Patent Application EP-A-0,518,755. Use is made, as precursors, either of an
organometallic compound or of a metal halide. In this instance, titanium
tetraisopropylate is chosen as organometallic compound, this compound being
advantageous because of its high volatility and its large working temperature range,
from 300 to 650.degree. C. In this example, deposition is carried out at approximately
425.degree. C. and the TiO.sub.2 thickness is 15 nm.
Tetraethoxytitanium Ti(O--Et).sub.4 may also be suitable and, as halide, mention may
be made of TiCl.sub.4.
Example 5
It is carried out similarly to Example 4, except that, in this instance, the 15 nm
TiO.sub.2 layer is not deposited directly on the glass but on a 50 nm SiOC sublayer
deposited as in Example 3.
Example 6
It s carried out as in Example 4, except that, in this instance, the thickness of the
TiO.sub.2 layer is 65 nm.
Example 7
It is carried out as in Example 5, except that, in this instance, the thickness of the
TiO.sub.2 layer is 60 nm.
From these Examples 4 to 7, it is found that the substrates thus coated exhibit good
mechanical behaviour with respect to the abrasion tests. In particular, no delamination
of the TiO.sub.2 layer is observed.
Example 8
This example uses a technique in combination with the sol-gel using a deposition
method by "dipping", also known as "dip coating", the principle of which emerges
from FIG. 2: it consists in immersing the substrate 1 in the liquid solution 4 containing
the appropriate precursor(s) of the coating 3 and in then withdrawing the substrate 1
therefrom at a controlled rate using a motor means 5, the choice of the rate of
withdrawal making it possible to adjust the thickness of solution remaining at the
surface of the two faces of the substrate and, in fact, the thickness of the coatings
deposited, after heat treatment of the latter in order both to evaporate the solvent and
to decompose the precursor or precursors to oxide.
Use is made, for depositing the coating 3, of a solution 4 comprising either titanium
tetrabutoxide Ti(O--Bu).sub.4, stabilized with diethanolamine DEA in the molar
proportion 1:1, in an ethanol-type solvent containing 0.2 mol of tetrabutoxide per litre
of ethanol, or the mixture of precursors and of solvents described in Example 1.
(Another precursor, such as titanium (diethanolaminato)dibutoxide, can also be used).
The substrates 1 can contain SiOC sublayers.
After withdrawal from each of the solutions 4, the substrates 1 are heated for 1 hour at
100.degree. C. and then for approximately 3 hours at 550.degree. C. with the
temperature raised gradually.
A coating 3 is obtained on each of the faces, which coating is in both cases made of
highly crystalline TiO.sub.2 in the anatase form.
Example 9
This example uses the technique known as "cell coating", the principle of which is
recalled in FIG. 3. It relates to forming a narrow cavity, delimited by two substantially
parallel faces 6, 7 and two seals 8, 9, at least one of these faces 6, 7 consisting of the
face of the substrate 1 to be treated. The cavity is then filled with the solution 4 of
precursor(s) of the coating and the solution 4 is withdrawn in a controlled way, so as
to form a wetting meniscus, for example using a peristaltic pump 10, leaving a film of
the solution 4 on the face of the substrate 1 as this solution is withdrawn.
The cavity 5 is then maintained for at least the time necessary for drying. The film is
cured by heat treatment. The advantage of this technique, in comparison with "dip
coating", is in particular that it is possible to treat only a single one of the two faces of
the substrate 1 and not both systematically, unless a masking system is resorted to.
The substrates 1 comprise thin layers 2 based on silicon oxycarbide SiOC.
Example 6 uses respectively the solutions 4 described in Example 8. The same heat
treatments are then carried out in order to obtain the TiO.sub.2 coating 3.
The coating 3 exhibits good mechanical durability.
Under an SEM (scanning electron microscope), a field effect appears in the form of
"grains" of monocrystals with a diameter of approximately 30 nm. The roughness of
this coating induces wetting properties which are enhanced with respect to a
non-rough coating.
These same solutions 4 can also be used to deposit coatings by "spray coating", as
represented in FIG. 4, where the solution 4 is sprayed in the form of a cloud against
the substrate 1 statically, or by laminar coating, as represented in FIG. 5. In the latter
case, the substrate 1, held by vacuum suction against a support 11 made of stainless
steel and Teflon, is passed over a tank 12 containing the solution, in which solution is
partially immersed a slotted cylinder 14, and the combined tank 12 and cylinder 14
are then moved over the whole length of the substrate 1, the mask 13 preventing
excessive evaporation of the solvent from the solution 4. For further details regarding
this latter technique, reference will advantageously be made to the abovementioned
Patent Application WO-94/01598.
Tests were carried out on the substrates obtained according to the above examples in
order to characterize the coatings deposited and to evaluate their "anti-condensation"
and "dirt-repellent" behaviour.
Test 1: This is the test of the condensation aspects. It consists in observing the
consequences of the photocatalysis and of the structure of the coating (level of
hydroxyl groups, porosity, roughness) on the wetting. If the surface is photoreactive,
the carbonaceous microcontaminants which are deposited on the coating are
continually destroyed and the surface is hydrophilic and thus anti-condensation. It is
also possible to carry out a quantitative evaluation by suddenly reheating the initially
coated substrate, stored in the cold or simply by blowing over the substrate, by
measuring if condensation appears and, in the affirmative, at what time, and by then
measuring the time necessary for the disappearance of the said condensation.
Test 2: It relates to the evaluation of the hydrophilicity and the oleophilicity at the
surface of the coating 3, in comparison with those of the surface of a bare glass, by
measurement of contact angles of a drop of water and of a drop of DOP (dioctyl
phthalate) at their surfaces, after having left the substrates for one week in the
surrounding atmosphere under natural light, in the dark and then having subjected
them to UVA radiation for 20 minutes.
Test 3: It consists in depositing, on the substrate to be evaluated, a layer of an
organosilane and in irradiating it with UVA radiation so as to degrade it by
photocatalysis. As the organosilane modifies the wetting properties, measurements of
contact angle of the substrate with water during the irradiation indicate the state of
degradation of the grafted layer. The rate of disappearance of this layer is related to
the photocatalytic activity of the substrate.
The grafted organosilane is a trichlorosilane: octadecyltrichlorosilane (OTS). The
grafting is carried out by dipping.
The test device is composed of a turntable rotating around from 1 to 6 low pressure
UVA lamps. The test specimens to be evaluated are placed in the turntable, the face to
be evaluated on the side of the UVA radiation. Depending on their position and the
number of lamps switched on, each test specimen receives a UVA irradiation varying
from 0.5 W/m.sup.2 to 50 W/m.sup.2. For Examples 1, 2, 3, 8 and 9, the irradiation
power is chosen as 1.8 W/m.sup.2 and, for Examples 4 to 7, as 0.6 W/m.sup.2.
The time between each measurement of the contact angle varies between 20 min and
3 h, depending on the photocatalytic activity of the test specimen under consideration.
The measurements are carried out using a goniometer.
Before irradiation, the glasses exhibit an angle of approximately 100.degree.. It is
considered that the layer is destroyed after irradiation when the angle is less than
20.degree..
Each test specimen tested is characterized by the mean rate of disappearance of the
layer, given in nanometres per hour, that is to say the thickness of the organosilane
layer deposited divided by the irradiation time which makes it possible to reach a final
stationary value of less than 20.degree. (time for disappearance of the organosilane
layer)
All the preceding examples pass Test 1, that is to say that, when the substrates coated
with the coating are blown on, they remain perfectly transparent, whereas a highly
visible layer of condensation is deposited on non-coated substrates.
The examples were subjected to Test 2: the coated substrates, after exposure to UVA
radiation, exhibit a contact angle with water and with DOP of not more than 50. In
contrast, a bare glass under the same conditions exhibits a contact angle with water of
40.degree. and a contact angle with DOP of 20.degree..
The results of the substrates coated according to the above examples in Test 3 are
combined in the table below.
Test 3, of wetting,
at 1.8 W/m.sup.2 UVA
Substrate
(in nm/h)
Example 1 (TiO.sub.2 on bare glass)
0.03
Example 2 (TiO.sub.2 on SnO.sub.2 :F)
0.1
Example 3 (TiO.sub.2 on SiOC)
0.2
Example 8 (TiO.sub.2 on 50 nm SiOC)
5
Example 9 (TiO.sub.2 on 50 nm SiOC)
5
Bare glass
0
Test 3, of wetting,
at 0.6 W/m.sup.2 UVA
Substrate (CVD)
(in nm/h)
Example 4 (TiO.sub.2 on bare glass)
<0.05 nm/h
Example 5 (TiO.sub.2 on SiOC)
4
Example 6 (TiO.sub.2 on bare glass)
Example 7 (TiO.sub.2 on SiOC)
9
19.5
From the table, it can be seen that the presence of sublayers, in particular of SiOC,
promotes the photocatalytic activity of the coating containing the TiO.sub.2, by its
barrier effect to alkali metals and alkaline-earth metals which can migrate from the
glass (comparison of Examples 4 and 5 or 6 and 7).
It is also observed that the thickness of the coating containing the TiO.sub.2 also plays
a role (comparison of Examples 1 and 3) for a TiO.sub.2 coating with a thickness
greater than the mean size of the monocrystals or "crystallites", a better photocatalytic
effect is obtained.
Indeed, it could be observed that the TiO.sub.2 coatings obtained by CVD exhibit the
most advanced crystallization, with crystallite sizes of the order of 20 to 30 nm. It can
be seen that the photocatalytic activity of Example 6 (65 nm of TiO.sub.2) is
markedly greater than that of Example 4 (15 nm of TiO.sub.2 only). It is therefore
advantageous to provide a TiO.sub.2 coating thickness at least two times greater than
the mean diameter of the crystallites which it contains. Alternatively, as in the case of
Example 5, it is possible to retain a TiO.sub.2 coating with a thin thickness but then to
choose to use a sublayer of an appropriate nature and with an appropriate thickness
for promoting as far as possible the crystalline growth of TiO.sub.2 from the "first"
layer of crystallites.
It could be observed that the crystallization of the TiO.sub.2 was somewhat less
advanced for the coatings deposited by a technique other than CVD. Here again,
however, everything is still a matter of compromise: a less advanced crystallization
and an a priori lower photocatalytic activity can be "compensated for" by the use of a
deposition process which is less expensive or less complex, for example. Moreover,
the use of an appropriate sublayer or the doping of the TiO.sub.2 can make it possible
to improve the photocatalytic behaviour, if necessary.
It is also confirmed, from the comparison of Examples 2 and 3, that the nature of the
sublayer influences the crystallization form and, in fact, the photocatalytic activity of
the coating.