Effect of Electrical Properties of Orientation Films on Switching Current and EO Performance of FE-LCD

Simultaneous observation of the temporal behaviors of the switching currents, and the electrooptic (EO) response, in ferroelectric liquid crystal (FLC) cells prepared by using molecular orientation films of rubbed polyimide (PI) and PI Langmuir-Blodgett films has been carried out. The effect on these phenomena of doping of a charge-transfer complex into the FLC medium also has been investigated. The behavior has been interpreted by investigating the effect of the internal depolarization fields originating from accumulated charges on the nonconductive orientation films such as ordinary rubbed PI. In the case where PI-LB films were used, the switching current and the EO response were shown to start exactly at the instant when the applied triangular voltage waveform reversed polarity, whereas in the case of insulating orientation layers there occurred a phase advance both in the switching current and EO response. Through this study, the magnitude of the depolarization field was estimated.