ESSENTIAL ELEMENTS FOR INKJET
PRINTING
R.B.CHAVAN
Dept. of Textile Technology
Indian Institute of Technology
Hauz-Khas, New Delhi 110016
COMPUTER
• Computer system essential for data
processing
• CPU Pentium IV 600Hz x2 or above
• OS Windows NT4SP4
• Memory 256 MB or above
• Hard disk 9.1 GB or above
• CD-ROM 40 x or above
• Color display (Monitor) 17 inch
SOFTWARE
• Raster Image Processing (RIP)
• Colour Management System
• Convert scanned design into electronic
signals.
• Allows editing of design
• Give command to the inkjet printer for
faithful printing of scanned/edited design.
DIGITAL PRINTER
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Mainly DOD printers used for textile printing
Choice
Thermal or bubble jet printer
Piezo printer
Piezo preferred
wide choice inks
Reliability
Durable print heads
TEXTILE SUBSTRATE
• In digital world known as “ media “
• Fabric to be printed
FABRIC PRE-TREATMENT
• Conventional printing
• Bleached fabric without any pre-treatment is used
for conventional printing
• Chemicals and auxiliaries necessary for print
fixation like thickener, urea, alkali, acid, defoaming
agents etc. are incorporated in the print paste
• Viscous print paste. No danger of print spreading
• Digital printing
• Printing chemicals/auxiliaries can not in
incorporated in printing ink.
• They are incorporated in fabric in the form of fabric
pre-treatment.
FABRIC PRE-TREATMENT
• Such pre-treatments help to maximize the
absorbency and reactivity of the textile substrate
towards the inks.
• Minimize ink spreading to prevent loss of definition
and colour intensity.
• Many patented and proprietary formulations exist,
• ranging from simple formulations of soda ash,
alginate and urea
• to more sophisticated combinations of cationic
agents, softeners, polymers and inorganic
particulates such as fumed silica.
• Many of these have been aimed at fashion fabrics
such as cotton, silk, nylon and wool.
• 3P InkJet Textiles (Germany) is marketing pretreated
fabrics ready for inkjet printing.
Fabric pre-coat machine
Fabric Feeding System
Fabric feeding
Fabric Exit
ensures perfect registration and alignment throughout, even for
delicate and unstable fabrics such as knits or fine silks. If required,
this machine may also pre-heat, dry or set the printed fabric, before
finally rolling-up the output smoothly and with even tension.
Ichinose-unit: conveyor belt and dryer
Ichinose uses a conveyor belt to transport and align the textile substrate.
The conveyor belt carrying the fabric gently moves ahead for inkjet printing
operation. The print head nozzles are set up right above the carrier belt, and
the cloth printed with the inks sprayed from the head nozzles. This can
prevent the inks from bleeding onto the cloth. After printing operation the
cloth at the exit end is released from the conveyor belt. The conveyor belt
can be cleaned whenever necessary
Requirement of ink for paper printing
• All papers are cellulose in nature
• Ink held on paper mainly by adhesive
forces
• Most suitable inks are pigments or any
water soluble dye
• Adhesion of ink to paper is through simple
adhesives like PVA or poly vinyl acetate.
• paper is not subjected to washing, rubbing
and various other agencies to which fabric
is subjected.
• Only requirement is good light fastness
Ink requirement for textiles
• Fibres of different nature are available
correspondingly different classes of suitable
dyes for each fibre
• During use textile material is subjected to
various agencies like washing, rubbing, chlorine
water (Swimming), light, perspiration etc
• Fastness requirement in case of textiles is more
stringent compared to paper
• Adhesive forces are not adequate to give the
desired fastness properties to printed textiles
• ink (dye, Pigment) must be held by means of
interactive forces between dye and fibre.
Ink requirement for textiles
• The interactive forces will vary depending on the
nature of fibre and dye class e.g.
• Reactive dye:Cellulose Covalent bond
• Acid dye:Silk Electrostatic force
• Disperse dye :Polyester H bonding, entrapment
in compact fibre structure
• Textiles are stretchable, flexible, often have
highly porous and textured surface
• Textiles, being porous, and absorbent, require
greater volume of ink to produce same shade
compared to paper.
• Fabrics with neps and pile leave lint on print
head causing nozzle clogging
INKJET INKS
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High purity
Dyes
Pigments
Milled to very fine particle size and particle size
distribution
Ink formulation
Precise viscosity and surface tension
Good shelf life, no settling
High colour strength
Good colour build up on fabric.
Good fastness properties
Typical operating parameters for ink-jet engines
Print Head
Viscosity cps
Drop volume Pico
litre pl
Continuous
1-10
400
Thermal
1-3
200
Piezo
5-30
100
The average particle size of disperse ink must be approx.
0,5 micro meter or lower in order to avoid clogging of the
nozzles. Electrostatic deflection systems also require
that the ink is electrically conducting which is difficult to
achieve in organic solvent based systems.
REACTIVE AND ACID DYES
• Reactive dyes are suited to cotton, viscose and
other cellulosic materials
• acid dyes are used for wool, silk and nylon.
• Both are fully water soluble and relatively easy to
formulate for a wide range of inkjet heads.
• especially the widely installed thermal drop on
demand jet types.
PIGMENT COLOURS AND DISPERSE DYES
• Both exist in water as dispersion of small particles.
• These inks must be prepared with high degree of
expertise so that the particles will not settle or
agglomerate (flocculate).
• The particle size must have an average of 0.5
micrometer and the particle size distribution must be
very narrow with more than 99% of the particles
smaller than 1 micrometer in order to avoid clogging
of the nozzles.
PIGMENT COLOURS
• pigment printing accounts for over 50% of
all conventional textile printing.
• they offer excellent wash and light
fastness and have the great advantage of
universal application to almost all fibres.
• after treatments are limited to a dry fixation
process.
• Research is going on to develop UVcurable pigment inks in- stead of thermal
curable inks.
BINDER APPLICATION
• major problem with use of pigments in inkjet
system is how best to formulate and apply the
resins binder which is required to bond the
pigment particles to the fabric surface.
• Several different approaches, from spraying
binder through a separate jet head to screen
printing binder over an inkjet printed colour have
been suggested.
• In the long run, improved binder technology
seems likely to prevail, allowing trouble- free
formulation and printing from a single inkjet head
for each colour.
Commercial water-based inks
Supplier
Trade name
Type
Dyestar
Helizarine
Bafixan
Reactive
Terasil (D)
Terasil (T)
Irgaphor TBI
Cibacron
Lanaset
Dorasyn
Pigment
Disperse (Transfer)
Reactive (MCT)
Disperse
Disperse 9Transfer)
HC Pigment + binder
Reactive MCT
Acid
Acid
Artistry 1000
Artistry 500
Colorspan
Pigment (CMYK)
Pigment + Binder
Reactive
Ciba
Dohmenn
Dupont
Colorspan
Digital printing inks for different substrates
Fibre
Colorant
Aftertreatment
(Fixation)
After
wash
Cotton,
Viscose
Reactive
Steam
Yes
Silk,
wool,
Polyamide
Polyester
All fibres
Reactive/
Acid
Disperse
Pigment
Steam
Yes
HT steam
Yes
Polymerization No
Thermal,
UV
curing
Ink formulation
Component
Content %
Water
< 80
Solvent (Ethylene
Glycol*
30 Max
Additives (Wetting and
Antifoaming agents
Dye
10
*Avoids drying out of the nozzles
Upto 10
SPOT COLOURS
• Inks used in conventional (Analog) printing
are known as spot colours.
• required shade is prepared by mixing
appropriate colours before printing.
• It is a skilled job,
• It allows matching the desired shade as
closely as possible.
• This gives an extremely large colour
gamut, less variation in colour in solid areas,
and a cleaner brighter shades.
Process Colours
• The inks used in inkjet printing are known
as process colours.
• The desired shade is produced on fabric
itself during printing operation by blending
the primaries -cyan, magenta, yellow and
black (CMYK) drop by drop sequentially
over a small area rather than being
premixed in an ink kitchen prior to printing
• Each primary must be transparent to
produce compound shades using CMYK.
Process Colours
• With screen-printing the inks may be dried
between colours,
• with ink-jet all colours are printed
simultaneously, wet on wet.
• The colour gamut obtainable with spot
colours is larger than with process colours.
• limitations
• inability of any given set of CMYK process
colours to generate a full colour gamut
suitable for textile industry.
Process Colours
• Theoretically one may be able to produce 16.7
million colours;
• however, only 1.5 million might be useful for
most textile printing
• out of this 1 million colours may be outside the
colour space possible from this system.
• In order to improve the colour gamut and to
obtain extremely fine images special colour
systems are developed. Hexachrome® (Pantone
Inc.) is a 6-color process consisting of the four
basic colours plus orange and green inks. This
approach results in more brilliant continuoustone images and in almost twice the number of
colours that can be obtained using CMYK
Extended Process colours
• In order to improve the colour gamut
special colour systems are developed.
• Hexachrome® (Pantone Inc.) is a 6
Process colour system consisting of the
four basic colours (CMYK) plus orange
and green inks.
• This approach results in more brilliant
continuous-tone images
• Almost twice the number of colours that
can be obtained using CMYK
CMYK
Colour gamut with 4 and 6 inks
outside: Hexachrome gamut
Inside: CMYK gamut
Extended Process colours
• Introduction of 6, 7, 8, and even 12-color digital
printers into the market,
• these systems come closer to achieving the
results obtained using analog printing. .
• However, this increasing number of colours in
the design of systems for ink-jet printing of
textiles is problematical.
• Each additional colour head increases the
problems of data handling rate and nozzle
failure.
• It also significantly reduces the fraction of the
printer that is not actively printing at any given
moment,
• thus significantly reducing machine efficiency.
Fabric post Treatments
• Post treatments similar to analog printing
• Steaming, curing for dye/pigment fixation
• Washing to remove unfixed colour and
chemicals, thickener.
• Finishing: Water repellant, fire retardant,
soil release etc.
Slow adoption of inkjet printing
• The existing speeds adequate for sample printing
but not for bulk production
• Availability of printing inks at reasonable cost
• Colour matching problems in flat colours
• Reproducibility of results from one printer to
another printer.
• Migration of manufacturing capacity to Asia where
labour intensive processes
prevail.
• Main stream textile printers are geared to low cost
mass production business model and long response
time
• Niche market has to be build up from scratch
• Educating the consumers about the potentialities of
digital printing.
Future Vision
• Sampling: This is the traditional application area and
this may be expected to continue with modest
growth.
• Bulk production for batches less than 1000 metres.
• This is the vision of many
• Mass-customization: The creation of new niche
markets for small-medium batches of printed textiles
for specific customers.
• It may be possible that garment makers decide to
buy a digital printer and attach it to a laser cutting
table.
• After printing, the fabric could be cut single ply
using a computerized system and then converted to
made-ups.
Future Vision
• Major inkjet manufacturers are working to
resolve the issue of production speed and it is
hoped that inkjet printers will be available with a
speed to compete with rotary screen printing.
• The ITMA 2003 exhibition in Birmingham, UK,
was a significant milestone for digital printing,
• 27 companies offering textile digital printing
equipment.
• Many of the machines shown were said to print
at over 50 m2 per hour,
• Reggiani printer was said to print at
150m2/hour.
• However this far less than rotary screen printing
(3600 meters/hour)
Future Vision
• The other possibility is that inkjet printing
technology may be used as weaving
technology
• where printers may have large number of
inkjet printers like looms to carry out the
printing production.
• In Bangkok a printing unit has 25 Stork
Sapphire machines run much like a
traditional weaving department.
Conclusion
• Digital printing provides an opportunity to meet the
present day market trends of mass customization.
• It has established as an acceptable technology for
sample production.
• Among other technology problems speed of printing
is the main hurdle in commercialization of
technology.
• Attempts are being made to achieve commercially
acceptable printing speeds.
• Till then the practice of combination of digital
printing for sampling and rotary screen printing for
production will continue.
• What now seems certain is that there is sufficient
industrial investment and commitment by
manufacturers to ensure that commercial ink jet
textile printing will become a reality.