An optical design for reflective color STN-LCDs

This paper describes the optical design method for reflective color STN-LCDs with single polarizers. The design method ensures the devices have high reflectance, high contrast ratio, and good color purity. The design of an STN liquid crystal layer, a polarizer, two birefringent films, color filters and a diffusion film are presented and a novel evaluation method for reflective LCDs is proposed. In the design of the STN LC cell, the polarizer, and the birefringent films, i.e. the design of the Single Polarizer STN LCD mode, we focus on achieving achromatic dark representation, since we found earlier that the chromaticity in the dark representation significantly affects the color balance. The polarizer and birefringent films are optimized to achieve achromatic dark representation for a given STN LC layer. The retardation of the STN LC layer is optimized to achieve achromatic dark representation and high reflectance. The color filters are optimized to achieve a large color gamut and high transmittance with good white balance. The diffusion film is designed to increase the reflection in an office.