Vertically aligned LCD

A. Takeda, S. Kataoka, T. Sasaki, et al., A super-high-image-quality multi-domain vertical alignment LCD by new tubbing-less technology, SID Tech Digest 29, 1077 (1997). 

The present invention is provided a two-domain vertical aligned LCD with negative compensator. The liquid crystal molecules in each of the liquid crystal domains are orientated nearly perpendicular to surfaces of the transparent substrates with a little pre-tilted angle to the normal of said substrates when an electric field is not applied, the tilt angle projected on the azimuthal of substrate between the orientation of liquid crystal molecules in two domains are not equal to 180 degrees, and the orientation of said liquid crystal molecules in two domains are oriented opposed direction. The structure that described above is obtained by UV exposure process. 

In LCDs various LC modes of operation are applied like twisted nematic (TN) [5], super twisted nematic (STN)[6], vertically aligned nematic (VAN) [7,8], optically compensated birefringence (OCB) [9] and in plane switching (IPS) [10-12]. The LC mode used depends on the demands of a specific application, like the viewing angle, power consumption and manufacturing cost. 

K. Ohmuro, S. Kataoka, T. Sasaki, and Y. Koike, Development of super-high-irrrage-quality vertical alignment-mode LCD, SID Tech. Digest 28, 845 (1997). 

The generation of high pretilt angle by such an approach led immediately to the development of vertically aligned nematic (VA)-LCDs using PI films with a very high pretilt angle of 89° on the basis of the research of Pl-coated STN-LCDs. 

Figure 4.1 The multidomain VAN-LCD based on two arrays of photopolymer gratings arranged orthogonal to each other [9]. Reproduced from J.-H. Park, Y. Choi, T.-Y. Yoon, C.-J. Yu, and S.-D. Lee, A self-aligned mnlti-domain Uquid-crystal display on polymer gratings in a vertically aligned configuration. Journal of the SID 11/2, 283 (2003), The Society for Information Display...

Figure 4.2 Preparation of pretilted vertical alignment for VAN-LCD by a photoalignment method [11]. Reproduced from V. A. Konovalov, V. G. Chigrinov, H.-S. Kwok, H. Takada, and H. Takatsu, Photoaligned vertical aligned nematic mode in liquid crystals. Japanese Journal of Applied Physics 43, 261 (2004), Institute of Pure and Applied Physics...

When a discotic liquid crystal is sandwiched between two substrates (or exposed to air), the direction of the uniaxial axis can be controlled by alignment layers, external electric fields, and chiral dopants [46,47]. It is therefore possible to develop discotic compensation films with spatially varied uniaxial axis orientations. For example, Fuji Photo Film Co. developed discotic compensation films for TN LCDs. In both the TN display and discotic compensation film, the liquid crystal directors vary in the vertical direction. Each layer of nematic liquid crystal with a certain director orientation is compensated by a layer of discotic liquid crystal with the same director orientation. 

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