Abstract
In general commercial STN mixtures are based on materials, which absorb UV light and are degraded by it. In order to generate long lifetimes for Photoluminescent Liquid Crystal Displays (PL-LCDs) it is necessary to develop STN mixtures that are transparent and, therefore, stable when operating with UV light. We have formulated STN nematic mixtures by adding UV-transparent chiral dopants into an UV-stable nematic mixture. Comparisons of the results of life tests and absorption spectra of these mixtures with analogous mixtures with conventional UV-unstable LCs, which contain conjugated phenyl rings and/or cyano-groups, show that such groups absorb in the UV and consequently lower the UV stability of the mixtures. The physical properties of the mixtures have been evaluated to assess the likely device performance of the resulting PL-LCD. In order to assess its multiplexability the sharpness of its electro-optic response was determined using single pixels with twists of 180°, 240° and 270°. We found that 240° twist gives the best multiplexing as 270° showed hysteresis.