Control of high pretilt angle for nematic liquid crystal using in situ photoalignment method on homeotropic alignment layer

Pretilt angle generation and liquid crystal (LC) aligning capabilities for nematic (N) LC using an in situ photoalignment method with obliquely polari zed UV exposure of the polyimide (PI) surface for homeotropic alignment wer e studied. The high pretilt angle of 30 degrees for NLC with obliquely pola rized UV exposure for 10-20 min on the PI surface can be achieved. The expo sure energy of UV used was 15.5 mW/cm(2) at 365 nm. The pretilt angle gener ated in NLC using the in situ photoalignment method was higher than that ge nerated using a conventional photoalignment method on a homeotropic alignme nt laver. Lastly, we suggest that the generation of pretilt angle in NLC wi th obliquely polarized UV exposure during imidization of the polymer for ho meotropic alignment is a promising method to generate a high pretilt angle.