LIQUID CRYSTAL COMPOSITIONS

摘要

A liquid crystal composition comprising from 90 % to 99.9 % by weight of one or more achiral host compounds of formula (1) wherein X is A1 or OA1; Y is A1, OA1; OCOA1 or CO2A1; A1 is a straight or branched chain alkyl group containing from 1 to 18 carbon atoms, optionally substituted with one or more F or CN; Z1, Z2, Z3, and Z4 may each be H or F, but either one or two of Z1, Z2, Z3, and Z4 must be F; D is (a), (b), (c) or (d) and from 0.1 % to 10 % by weight of a chiral dopant compound of formula (2) wherein D1 is D (as in formula (1)) or a single bond; Y1 is OA¿3?, OCOA3 or CO2A4; A3 is an alkyl group containing from 1 to 18 carbon atoms, optionally substituted with one or more F or CN and containing at least one centre of asymmetry; A4 can either be the same as A3 or a group of the formula: CH(R1)COA5 wherein R1 is an alkyl group containing from 1 to 5 carbon atoms and A5 is OR1 or -N(R2)R3 where R2 and R3 are hydrogen, R1, phenyl optionally substituted by R1, or together form a homocyclic or heterocyclic ring optionally substituted by R1, provided that R2 and R3 are not the same; and D, X, Z1, Z2, Z3 and Z4 have the above significance, except that all of Z1, Z2, Z3 and Z4 can be hydrogen. These compositions are useable in liquid crystal devices and, over a temperature range of 5 °C to 40 °C, have a relaxed cone angle of greater than 28° and a contrast ratio of at least 50:1.