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26 March 1999 Generation of high pretilt in photo-aligned polyimides
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Liquid crystals have been shown to align on polarized UV (PUV) exposed polyimide films with the liquid crystal director oriented perpendicular to the polarization direction. Uniform pretilt is produced by a second oblique PUV exposure. We report here the factors controlling liquid crystal alignment and pretilt on photo-exposed polyimide films. We show that the chemistry of the polyimide controls the liquid crystal aligns either parallel or perpendicular to the PUV. Also, the tilt angle of the liquid crystal can be varied continuously between 0 degrees and 90 degrees by adjusting the polyimide chemistry. Our results indicate that the liquid crystal has uniform pretilt with no preferred alignment direction on unexposed polyimide. Normal exposure aligns the director but the pretilt is degenerate, pointing in either the plus or minus direction. Oblique exposure breaks this degeneracy, producing a unique pretilt direction. We show that uniform alignment and pretilt can be produced with a single oblique exposure if the liquid crystal aligns parallel to the polarization direction.
© (1999) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
John L. West, Michinori Nishikawa, and Yuri A. Reznikov "Generation of high pretilt in photo-aligned polyimides", Proc. SPIE 3635, Liquid Crystal Materials, Devices, and Applications VII, (26 March 1999);

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