Pretilt angle generation

Fig. 2.26 Illustrations of two types of mechanism for pretilt angle generation (a) Asymmetric distribution of the main chains, (b) Side chains push up the main chain.

Figure 3.9 Schematic diagram of in situ imidization and two-step DUV exposure setup [25]. Reproduced from J. Y. L. Ho, V. G. Chigrinov, and H.-S. Kwok, Variable liquid crystal pretilt angles generated by photoaligmnent of a mixed polyimide atigimient layer. Applied Physics Letters 90, 243506 (2007), American Institute of Physics...

D.-S. Seo and C.-H. Lee, Investigation of liquid crystal ahgmnent and pretilt angle generation in the cell with linearly polarized UV light irradiation on polymer surface. Molecular Crystals and Liquid Crystals 329, 255 (1999). 

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. 

It was also reported around that time that such a pretilt angle could happen if one lowers the interfacial energy, and the effect of the alkylated PI can be explained by the reduction of the interfacial energy [52]. Thereafter, a series of Pis that allow the generation of a stable pretilt, optical high transparent Pis, and cyclobutane polyamic acid (CBPA patent opening 1992/6/1) were developed and manufactured by Nissan Chemical Industries, Ltd. 

Figure 20. Generation of pretilt angle by rubbing the surface of alignment surface.

Figure 23. Schematic representation of the conformation of Pis derived from diamine having odd and even numbered carbons and the generation of pretilt angle.

Figure 3.3 Generation of the pretilt angle by a one-step exposure [4]. Reproduced from M. Nishikawa and J. West, Mechanism of generation of pretilt angles on polyimides with a single exposure of polarized ultraviolet light. Japanese Journal of Applied Physics 38, 5183 (1999), Institute of Physics...

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