Characterization of reflective cholesteric liquid-crystal displays

Abstract

We report on the optical reflective properties of the planar texture of cholesteric liquid crystal reflective displays. The reflecting liquid-crystal medium is partitioned into many distinguishable domains, each of which is characterized by its local dielectric anisotropy. Such a multidomain cholesteric liquid crystal is made bistable by either dispersing a low concentration of polymer or by treating the cell substrate surfaces, both of which affect the domain alignment. Both types of cells result in a bistable colorful reflective display. We determine the role that the polymer network and surface alignment has on the reflective properties in regard to their photometric and colorimetric properties as a function of viewing angle using both collimated and diffuse illumination. Both the polymer network and surface anchoring have the effect of distributing the orientation of the cholesteric helix axes about the cell normal. Theoretically we characterize these cells by this distribution. Our goal is to properly model both types of display cells so as to quantitatively elucidate their distinguishing features.