Liquid crystal alignment with a photo-crosslinkable and solvent-soluble polyimide film

A new photo-crosslinkable and solvent-soluble polyimide containing cinnamat e side chains (PICA) was developed for aligning nematic liquid crystals (LC s). Good LC alignment was achieved by exposing a long-wave linearly polariz ed ultraviolet (LPUV) light to the PICA film. The LC alignment direction is found perpendicular to the polarization axis of the incident LPUV light. T he uniform alignment of LC molecules induced by PICA Films remains intact a fter being heated at 85 degreesC for 450 hours. A small pretilt angle on th e PICA film was generated by the double exposure method.