Polymer dispersed liquid crystal composite films-droplet orientation and optical responses

Abstract

Polymer dispersed liquid crystals (PDLCs) constitute an important class of novel materials in which liquid crystal droplets are dispersed in an appropriate polymer matrix. The opto-electric switching in these materials is achieved by matching the refractive index of the liquid crystal with that as the polymer matrix. In this paper, preparation and characterization of PDLC films of nematic and Ferroelectric liquid crystals in various polymers are described. PDLC films with a dichroic dye dissolved in the liquid crystal possess a controllable absorbance and a controllable scattering as well. This combination can be used to produce high contrast displays. This attractive feature is attributed to the molecular orientation in dispersed liquid crystal droplets and the optical transmission of dichroic PDLC cells exhibiting a remarkable dependence on the droplet morphology. It is found that the viscosity and concentration of the dichroic dye influence the LC droplet size and low dye concentration, samples show improved contrast ratio with reduced threshold voltage.