ELECTROOPTIC EFFECT IN POLYMER-DISPERSED CHOLESTERIC LIQUID-CRYSTALS WITH MEDIUM CHIRALITY

We have investigated the electro-optic behaviour of polymer sheets containing small chiral nematic liquid crystal droplets. In previous investigations of polymer-dispersed liquid crystals (PDLC), either non-chiral nematic liquid crystals or cholesteric liquid crystals with very small pitch (p < lambda) have been used. Here we adjusted the pitch p to be below the Mauguin limit, but well above the wavelength, lambda, of the visible range of light; typically we chose p approximate to 2 lambda/Delta n. Between crossed polarizers, the sample can be switched from a transparent off state to a dark on state. With respect to non-chiral nematic PDLC films, the transmittance is lower, but the angular dependence is improved.