Patent ID: 8013819
Filing Date: 2011-09-06
Classification: G09G

Abstract:
1. A method of driving a cholesteric liquid crystal display device which comprises at least one cell comprising a layer of cholesteric liquid crystal material and an electrode arrangement capable of providing driving of a plurality of pixels across the layer of cholesteric liquid crystal material by respective drive signals, the method comprising applying respective drive signals to each pixel to drive the pixels into states which are varied to provide a reflectance varying within a predetermined range of reflectances, the drive signals comprising: (a) when providing a reflectance in a first portion of the predetermined range of reflectances, a first waveform shaped to drive the pixel into a stable state, the waveform having a shape which is variable to provide a stable state having a varying reflectance; and (b) when providing a reflectance in a second portion of the predetermined range of reflectances which is lower than the first portion, a second waveform shaped to drive the pixel into the homeotropic state and the planar state alternately, the periods of time during which the pixel is driven into the homeotropic and planar states being variable to provide a varying average reflectance as perceived by a viewer.