Retardation-film-compensated reflective bistable twisted nematic liquid-crystal displays

The reflective bistable twisted nematic liquid-crystal-displays (RBTN-LCDs) with a single front polarizer have been compensated by front half-wave or integer-wave plates or both. The compensation has been optimized through maximizing the contrast ratio. The optimized RBTN-LCDs with one or two retardation plates showed great improvement in contrast ratio. The wavelength-dependent reflectance, viewing-angle properties, and effect of the retardation variation of these optimized RBTNs with retardation compensation were also investigated. The simulation was carried out by using realistic parameters on RBTN modes that have retardation values from 0.30 to 0.85 microm and a low contrast ratio. The viewing-angle properties did not change much before and after the retardation compensation. The reflectance varied little, but the contrast ratio varied significantly with the variation of the retardations of the bistable twisted nematic cells, for both compensated and uncompensated cases. It is shown that a high contrast ratio (100:1), high reflectance (30%), and low dispersion are possible for such RBTN-LCDs with proper retardation compensations. Black-white operations can be realized by compensating RBTN-LCDs.