GB1383047A - Liquid crystal display devices - Google Patents

Abstract

1383047 Modulating light MARCONI CO Ltd 16 July 1973 [4 Aug 1972] 36487/72 Heading H4F An electro-optic cell comprises a layer of liquid crystal material contained between two electrode structures, the facing surfaces of the electrode structures each having been rubbed in a single direction with an ionic, polar or polymeric chemical compound such as to encourage orientation of the adjacent liquid crystal molecules parallel to the surface and to the direction of rubbing, the respective rubbing directions being parallel in the assembled cell. As particularly described, a nematic material having a negative dielectric anisotropy is used, being a single compound or a mixture, and the cell is disposed between polarizers respectively parallel and at 90 degrees to the common rubbing direction, whereby in the absence of an electric field across the layer, no light is transmitted through the second polarizer. When a potential difference (A.C. or D.C.) is applied between the electrode structures, the nematic layer scatters and depolarizes the light, some of which is then transmitted by the second polarizer. The electrode structures comprise conductive films, e.g. in a seven segment pattern, lying on a substrate and overlaid with a semi-insulating layer of silicon monoxide which provides the surface to be rubbed. The polarizers may be films cemented to the outer surfaces of the electrode structures and the light source may include a diffusing screen or an electroluminescent panel. The chemical compound with which the electrode structures are rubbed may be an ionic polar or polymeric material, including polyvinyl pyrrolidone; polyacrylamide; tetrabutyl-ammonium salts; indophenol blue; dioxan; 1,4- butanediol-diglycidyl ether; 4-nitrobenzylidene phenylhydrazone and 4-dimethylammocinnamylidene 2<SP>1</SP>, 4<SP>1</SP> dinitrophenylhydrazone.