Abstract: A compound of formula (I): where R1 is alkyl or alkenyl, Y1 and Y2 are independently selected from oxygen or sulphur, n is an integer of from 1 to 5, A is an optionally substituted phenyl or an optionally substituted cycloalkyl ring, X is a direct bond, a C1-4alkylene, a C2-4alkenylene, an acetylene, —CO(O)— or a group of sub-formula (i): where X1 and X2 are independently selected from a direct bond, a C1-4alkylene, a C2-4alkenylene, an acetylene, —CO(O)— and R2, R3 and R4 are independently selected from hydrogen, halo or cyano, provided that no more than one of R2, R3 and R4 is hydrogen. These compounds have a high dipole moment and may be used as dopants in liquid crystal mixtures.

Abstract: The use of a compound of formula (I) wherein R1 is an alkyl or alkenyl group, either of which may be optionally interposed with one or more oxygen or sulphur atoms, R2 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 C1-4alkylene or C2-4alkenylene chain, and A is group comprising one or two rings which are independently selected from aryl, heterocylic or cycloalkyl rings, and when there are two rings, they are bonded together directly or by way of a C1-4alkylene or C2-4alkenylene group, for increasing the u.v. stability of a liquid crystal mixture. The compounds of formula (I) are u.v. stable and are useful in liquid crystal devices which are exposed to high levels of u.v. light such as phosphor display cells. Certain compounds are novel and these form a further aspect of the invention.

Abstract: The use of a compound of formula (I) 1

Abstract: Liquid crystal mixtures comprising at least one of the compounds of formula (I) containing a heterocyclic five-membered ring and with a carbon-carbon double bond in the termninal group are new. RJ=CnH2n+1CH=CHCmH2mZ1; n=1-5; m=0-5; and q=0, 1 or 2; A1 and A2=2,5-disubstituted furan, 2,5-disubstituted thiophene, 2,5-disubstituted oxazole, 2,5-disubstituted thiazole, 2,5-disubstituted 1,3,4-oxadiazole, 2,5-disubstituted 1,3,4-thiadiazole, 1,4-disubstituted benzene, 2,5-disubstituted pyrimidine, 2,5-disubstituted pyridine, 2,6-disubstituted naphthalene; laterally substituted 1,4-disubstituted benzene, laterally substituted 2,5-disubstituted pyrimidine, laterally substituted 2,5-disubstituted pyridine or laterally substituted 2,6-disubstituted naphthalene (lateral substituents=F, Cl, Br or CN); A3=any A1 or 1,4-disubstituted bicyclo(2.2.