Generation of Maxwell Displacement Current across Liquid Crystal Monolayers and Control of Liquid Crystal Alignment

Abstract

The orientational transition process of p-pentyl-p'-cyano-biphenyl (5CB) liquid crystal monolayers at the air-water surface during monolayer compression and the cis-trans photoisomerization process of surface azobenzene monolayer were examined using the Maxwell displacement current measurement. Using this measurement, the orientational transition process of 5CB molecules in monolayers mixed with azobenzene molecules was examined by alternating irradiation with ultra-violet and visible light. Subsequently, we examined the orientational transition process of 5CB molecules in Liquid crystal (LC) cells triggered by the conformational change of the surface azobezene monolayer on polyimide (PI) Langmuir-Blodgett (LB) films. It was shown that the optical transmittance and the capacitance of the LC cells with 1-layer PI LB films changed reversibly by the alternating irradiation of ultra-violet (UV) and visible light, whereas those of LC cells with more than 3-layer PI LB layers did not change reversibly. These results were discussed taking into account the physico-chemical property of PI LB films.