Liquid crystal devices with particular cholesteric pitch-cell thickness ratio

Claim 1

A liquid crystal display device comprising: a layer of positive dielectric anisotropy cholesteric liquid crystal material of natural pitch p and thickness d less than 20 μm contained between two parallel spaced cell walls, electrode structures on both cell walls arranged to form a plurality of addressable elements, a surface treatment on both cells wall in contact with the liquid crystal material to align liquid crystal molecules in a tilted homogeneous structure, said surface alignment being matched to said cholesteric material to provide a progressive molecular twist of greater than π and less than 2π radians across said layer with a uniform tilt direction, the ratio of layer thickness d divided by pitch p laying between 0.5 and 1.0, said device further comprising means for selectively absorbing transmitted light depending on the molecular orientation of the liquid crystal material, two sets of driver circuits and a controlling logic circuit for repetitively applying voltage from a voltage source to the electrode structures in a multiplexed sequence, wherein each of said addressable elements may be switched directly between a light transmissive state and a nontransmissive state with a sharp transmission/voltage characteristic without substantial hysteresis.