Abstract: A cholesteric liquid crystal display device comprises three cells each comprising a layer of cholesteric liquid crystal material and an electrode arrangement capable of providing independent driving of a plurality of pixels across the layer of cholesteric liquid crystal material by respective drive signals. A drive circuit applies a respective drive signal to each pixel to drive the pixel into states which are variable to provide a reflectance varying within a predetermined range of reflectances. The drive signals involve a combination of two drive schemes to provide reflectances in different portions of the range.

Abstract: A cholesteric liquid crystal display device (24) comprises three stacked cells (10R, 10G, 10B), each comprising a layer of cholesteric liquid crystal material (19) and an electrode arrangement (13, 14) capable of providing independent driving of a plurality of pixels across the layer of cholesteric liquid crystal material by respective drive signals. The display device has a drive circuit (22) arranged to apply respective drive signals to each pixel in successive cycles of predetermined duration. When providing a high reflectance, the drive signal comprises makes use of drive pulses (50) shaped to drive the pixel into the homeotropic state. When providing a low reflectance, the drive signal includes a number of perturbation pulses (61) which are sufficiently short and sufficiently spaced from each other that the pixel is driven into a transient state having a lower reflectance than the planar state.

Abstract: A cholesteric liquid crystal display device comprises three cells each comprising a layer of cholesteric liquid crystal material and an electrode arrangement capable of providing independent driving of a plurality of pixels across the layer of cholesteric liquid crystal material by respective drive signals. A drive circuit applies a respective drive signal to each pixel to drive the pixel into states which are variable to provide a reflectance varying within a predetermined range of reflectances. The drive signals involve a combination of two drive schemes to provide reflectances in different portions of the range.