Photostability of liquid crystals and alignment layers

Abstract

Abstract — Photostability of liquid-crystal (LC) materials and surface alignment layers was evaluated using a UV lamp and a blue laser beam. Both organic polyimide (PI) and inorganic silicon-dioxide (SiO2) alignment layers were studied under nitrogen environment. Two commercial TFT-grade LC mix-tures (low-birefringence MLC-9200-000 and high-birefringence TL-216) were used for comparisons. Results indicate that SiO2 alignment layers are much more robust than PI layers, and low birefringence LCs are more stable than the high-birefringence ones. At the He–Cd laser wavelength (λ = 442 nm), both LC mixtures and SiO2 alignment layers are hardly damaged. To lengthen the lifetime of an LCD projector, inorganic SiO2 alignment layers, high-optical-density UV filter, long cutoff-wavelength blue filter, and short-conjugation (low birefringence) LC materials should be considered