Effects of Dichroic Dye in UV-Cured Polymer Dispersed Liquid Crystal Films

Abstract

We study the effects of dichroic dye in “ultraviolet” polymer dispersed liquid crystal (PDLC) films. Experimental data show that for a dye-doped PDLC film the absorption coefficient for He-Ne laser light is different from that for UV light. Transmittance of a PDLC film changes when the UV curing intensity or dye concentration is varied. It is found that under UV the illumination with a constant intensity the dye concentration can be optimized to obtain minimum transmittance and to improve the contrast ratio. Correspondingly, for a fixed dye concentration the UV curing intensity can be optimized to obtain a minimum transmittance. The experimental results can be described by a theory based on Beer's law. Besides, the experimental results show that the curing temperature is an important factor that affects the nematic liquid crystal droplet size in the UV curing process.