Control of High Pretilt Angle for Nematic Liquid Crystal on Homeotropic Alignment Layer by In-situ Photoalignment Method

Pretilt angle generation and liquid crystal (LC) aligning capabilities for a nematic (N) LC with obliquely polarized UV exposure on a homeotropic polyimide (PI) surface by an in-situ photoalignment method were studied. The high pretilt angle of 30θ for NLC with obliquely polarized UV exposure on the PI surface for 20 min can be achieved. The pretilt angle generated in NLC by the in-situ photoalignment method was higher than that generated by a conventional photoalignment method on a homeotropic alignment layer. Also, we suggest that the generation of pretilt angle in NLC with obliquely polarized UV exposure during imidization of the polymer for homeotropic alignment is a promising method to generate a high pretilt angle. Lastly, the good electro-optical (EO) characteristics of the photoaligned vertical alignment (VA)-liquid crystal display (LCD) by UV exposure on the PI surface for 10 min were observed.