ELECTROOPTIC RESPONSE OF POLYMER DISPERSED LIQUID-CRYSTAL FILMS

The electro-optic response of polymer dispersed liquid-crystal (PDLC) films is reported as a function of frequency and amplitude of the applied voltage and size of the LC droplets. We found that the threshold voltage is minimum and sharpest at frequencies near a few kHz. Visual and optical response studies show that there are two types of PDLC films; type I, which exhibit large partial optical memory, and type II, which quickly regain their original levels of transmittance after switching off relatively small driving voltage. It was observed that both types of PDLC films, in general, exhibit a two-step decay involving fast and slow components. However, the order in which the two components appear as the voltage is increased is different for the two types of PDLC films. Observations under the polarizing microscope show that the LC droplets in the two types of PDLC films undergo different transformations as the applied voltage is changed.