Relationship between Film Thickness and Electro-Optical Properties in Polymer Dispersed Liquid Crystal Films

Abstract

Dependences of turbidity and dielectric constant on film thickness in polymer dispersed liquid crystal (PDLC) films are measured for a polymer ball type and a droplet type morphology. Liquid crystal molecules tend to align parallel to a substrate at the interface between the film and the substrate for the polymer ball type PDLC film, where contrast ratio in the thinner film becomes larger than that of the droplet type films. Electro-optical properties are represented using turbidity and electric field instead of transmittance and applied voltage. The electro-optical properties for the droplet type PDLC film are independent of film thickness, and a relationship between the driving voltage and the contrast ratio can be estimated for an arbitrary film thickness.