Liquid crystal display device

摘要

In a matrix display device having a cholesteric liquid crystal the bistability effect is used which some cholesteric liquid crystals show. The liquid crystal shows a frequency-dependent relaxation of a positive to a negative dielectric anisotropy. After writing the information the light-scattering picture elements have a focal-conical texture and the transparent elements have a homeotropic-nematic texture. The information can be stored for a longer period of time by causing the homeotropic-nematic texture of the transparent elements to change into the substantially transparent planar-conical texture. This is produced rapidly by applying across all picture elements a voltage of a frequency at which the liquid crystal has a negative dielectric anisotropy. The focal-conical texture of the light-scattering elements is substantially not disturbed by this voltage. During the presence of this voltage the written information is continuously visible.