Patent ID: 7097887

Claim:
A method for increasing the u.v. stability of a liquid crystal mixture comprising adding to or including in a liquid crystal mixture a compound of formula (I) wherein R 1 is an alkyl or alkenyl group, either of which may be optionally interposed with one or more oxygen or sulphur atoms, R 2 is an alkyl or alkenyl group, Y′ and Y″ are independently selected from oxygen or sulphur, n is an integer from 1 to 5, X is a direct bond or a C 1-4 alkylene or C 2-4 alkenylene chain, and A is group comprising one or two rings which are independently selected from aryl or heterocyclic rings, and when there are two rings, they are bonded together directly or by way of a C 1-4 alkylene or C 2-4 alkenylene group.