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Polyimide photo-alignment layers for inclined homeotropic alignment of liquid crystal molecules |
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| Authors: | Kiyoaki Usami Kenji Sakamoto Yoichi Uehara |
| Affiliation: | a Organic Nanomaterials Center, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan b Department of Information Systems Engineering, Osaka Sangyo University, 3-1-1 Nakagaito, Daito-Shi, Osaka 574-8530, Japan c Chisso Petrochemical Co., Ltd., 5-1 Goikaigan, Ichihara, Chiba 290-8551, Japan d Research Institute of Electrical Communication, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan e Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292, Japan |
| Abstract: | We have succeeded in realizing an inclined homeotropic alignment of liquid crystal (LC) molecules by using photo-aligned films of a polyimide containing azobenzene in the backbone structure. To induce such an LC alignment, a side chain structure was introduced into the backbone structure. The LC pretilt angle, measured from the surface normal, could be controlled up to 1.75° by varying the light exposure in oblique angle irradiation with unpolarized light. Its thermal stability was examined by annealing the LC cell at 100 °C. No change was observed in the pretilt angle even after annealing for 36 h, indicative of its excellent thermal stability. Since photo-alignment has patterning capability, the photo-aligned polyimide film is expected as a promising alignment film for multi-domain vertical alignment mode LC displays. |
| Keywords: | Photo-induced alignment method Polyimide containing azobenzene in the backbone structure Pretilt angle Inclined homeotropic alignment of liquid crystal molecules |
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