Liquid crystal display device

Claim 1

A display device comprising two supporting plates, crossing patterns of parallel strip-shaped electrodes on the facing surfaces of the supporting plates, a layer of cholesteric liquid crystal with positive dielectric anisotropy between the supporting plates, said liquid crystal, upon applying an electric field across the layer, having a focal-conic texture below a certain field strength E 1 , having a homeotropic-nematic texture above a certain field strength E 2 , and having one of the said textures for a field strength between E 1 and E 2 , the device furthermore comprising means to maintain the liquid crystal in the homeotropic-nematic texture at the edges of the electrodes above a field strength E 2 if the liquid crystal in the central part of the electrodes is in the homeotropic-nematic texture at a field strength between E 1 and E 2 characterized in that the said means are formed by grooves which are provided in the supporting plates and are separated by ridges and have a depth substantially equal to half the desired thickness of the liquid crystal layer, by electrodes provided in the grooves and extending up to the ridges and being separated from each other by a narrow strip on the ridges, and by a layer of dielectric material covering the electrode surface and the surface of the supporting plates situated between the electrodes.