In situ control of the photoinduced birefringence of photoalignable liquid crystalline polymeric films

Photoalignment is one the important techniques to fabricate flat panel displays, birefringent functional films, and polarized optical diffraction devises. Thinner optical devises are attained when the optical film exhibits high birefringence. We investigated systematic studies on photoalignable liquid crystalline polymers (PLCPs), which achieve molecularly oriented structure for themselves, showing the bulk-photoalignment. This paper describes new PLCPs which reveal high photosensitivity, high photoalignability, and controllability of generated birefringence by means of in situ modification of the oriented mesogenic side groups. The initial generated birefringence of the PLCP films is 0.15, whereas the improved birefringence exceeds 0.4 is achieved via in situ modification of the oriented mesogenic side groups. Using PLCP films, polarization gratings are fabricated.