Infrared spectroscopic studies of the thermal stability of alignment layers of polarized UV-exposed polyimide films for liquid crystal alignment

Polarized Fourier transform infrared (FTIR) and optical microscopy with cro ssed polarizer were used to investigate the thermal stability of the alignm ent layers formed by rubbing and polarized UV (PUV) irradiation on the poly imide (PI) films. The thermal stability of the PUV irradiated PI alignment layer is lower than that of the rubbed PI layer due to the fragmentation re action of me PI by PUV. We also investigated the alignment of the liquid cr ystal by rubbing or PUV irradiation. Liquid crystal (LC) molecules align pa rallel to the predominant orientation of the PI and perpendicular to the PU V irradiation direction.