Two Interfaces of Polyimide Alignment Layer and Bulk Pretilt Angle

Abstract

Side chain orientation of polyimide (PI) films for liquid crystal alignment has been studied by surface second-harmonic generation (SHG). SHG from two interfaces of the film was separately observed using thick films, in which SH light from the rear interface was almost absorbed in the film. Rubbing action caused in-plane anisotropy only for the air-PI interface. For as-coated films, the average tilt angle of the side chain at the air-PI interface is smaller than that of the other interface. The dstribution functions of the side chain of the rubbed PI film and bulk pretilt angle were also discussed.