Liquid crystal materials and devices

Abstract

ABSTRACT OF THE DISCLOSURE A liquid crystal material which at least contains a compound having a molecular structure such that the material exhibits a liquid crystal phase, the molecular structure of the compound being selected from one of the following structures: the structure ; a simple ortho-substituted derivative of the structure ; and a derivative of the structure in which a simple bridging group is contained between two of the ortho-positions of the said structure wherein X and Y are different para-substituents of the kind which promote liquid crystal behaviour, the para-substituent X being a group selected from the following list: an alkoxy group having more than one carbon atom; an alkyl group; an acyloxy group; and an alkenyl group; and the para-substituent Y being selected from the following list: a cyano group; a benzene ring substituted in the para-position by a cyano group; and a plurality of directly para-linked benzene rings in which the end ring remote from the substituent X is substituted in the para-position by a cyano group. The material may be the said compound or it may be a multi-component solution or mixture containing it. The liquid crystal material may be nematic, smectic or cholesteric depending on the selection of the substituents X and Y. A device such as a twisted nematic effect device, incorporating the material may be operated at low temperatures. The material does not suffer from significant chemical and/or photochemical decomposition when used in a liquid crystal device.