Droplet Size Control In Polymer Dispersed Liquid Crystal Films

Abstract

We have established correlations between the liquid crystal (LC) droplet size and selected characteristics of polymer dispersed liquid crystal (PDLC) films, formed by photopolymerization of LC dissolved in a monomer. The LC droplet size was controlled by means of the ultraviolet (UV) exposure intenstiy, LC concentration, and concentration of polymerization initiator. Correlations were noted between the LC droplet size and the resulting PDLC threshold and operating voltages for optical transmission, contrast ratio, and electro-optical response times. Good contrast PDLC films were obtained which were operable with less than 20 V, rms of applied signal. Special types of films, including in situ gratings were obtained by varying the conditions of polymerization across the film to produce a periodic spatial variation in the LC droplet size.