Fast Response Time of the In Plane Switching Liquid Crystal Mode on the
Photo-Sensitive Alignment Layer
Byung-June Mun,1 Ki-Woong Park,1 Joun Ho Lee,2 Byeong Koo Kim,2 Hyun Chul Choi,2 and
Gi-Dong Lee1,*
1 Department of Electronics Engineering, Dong-A University, Busan 604-714, South Korea
2 LG Display Co., Ltd., Gumi, Gyungbuk 730-731, South Korea
[Contact E-mail: gdlee@dau.ac.kr]
Performances for the displaying image quality of liquid crystal displays (LCDs) have been developed
by studying a variety of LC modes including twisted nematic (TN) [1], in-plane switching (IPS) [2, 7],
fringe-field switching (FFS) [3], vertical alignment (VA) [4] mode. Of all LC modes, IPS LC mode,
which is representative horizontal switching LC mode, exhibits fast response time and wide viewing
angle properties due to the optical mechanism of LCs. However, it is required to perform the surface
alignment technology for achieving the uniform orientation of the LC molecules in the cavity.
Conventional method for surface alignment of LCs was commonly used as rubbing of polymers in the
most of LCD applications because of its simplicity, thermal stability and especially strong anchoring
energy of the polymer film [5]. Nevertheless, mechanical rubbing method leads to deteriorate the
electro-optical properties owing to the generation of dust particles, electrostatic charges, physical
damages and low order parameter of LCs caused by contact type method. For these reasons, LC
alignment technology is recently changed to the photo-alignment method, which can make an
orientation of LCs by the exposure of the linearly polarized UV light by using the photo-sensitive
polymer materials, instead of the rubbing of polymers [6]. The technology for a photo-aligning shows
the many advantages over conventional rubbing of polymers, such as cleanliness and controllability of
alignment direction. Additionally, the alignment processing with good uniformity for large sized
display panels is also readily achievable. However, this method leads the poor chemical stability,
reliability and especially weak anchoring energy which can cause the slow response time compared to
that of the conventional rubbing of polymer films.
In this paper, we reported the enhanced photo-alignment method with strong anchoring energy by
coating the reactive mesogens (RMs) on the photo-sensitive alignment layer, and also proposed high
speed IPS LC mode on the photo-sensitive alignment layers. To more improve the speed of response
time, the retardation free mechanism which was reported in our previous study [7] is additionally
applied in the photo-aligned IPS LC mode. In experiments, we checked the azimuthal anchoring
energy and optical response time of the photo-aligned IPS LC cell, and also demonstrated the
electro-optical properties in this paper. As results, we observed that the surface anchoring energy of the
proposed IPS LC mode was enhanced to 2 times stronger than the conventional IPS LC mode without
RMs and thus, the response time improved over 70% because of the electro-optical effect of
retardation free mechanism.
Acknowledgement
This work was supported by LG Display Co., Ltd.
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