DRIVE SCHEMES FOR DRIVING CHOLESTERIC LIQUID CRYSTAL MATERIAL INTO THE FOCAL CONIC STATE

摘要

In a cholesteric liquid crystal display device (24), to drive a surface-stabilized layer of cholesteric liquid crystal material into the focal conic state, there is applied drive signal comprising a series of pulses (30, 34, 35, 36, 37, 38, 41). At least one initial pulse has sufficient energy to drive the layer of cholesteric liquid crystal material into the homeotropic state and the subsequent pulses have time-averaged energies which reduce to a minimum level at which the layer of cholesteric liquid crystal material is driven into the focal conic state. This produces a focal conic state of particularly low reflectance, which allows a high contrast ratio to be achieved.