Patent ID: 7033654

Claim:
Liquid-crystalline medium comprising a mixture of polar compounds of positive dielectric anisotropy, wherein: the medium comprises one or more compounds of formula Ia in which R is H, an alkyl or alkenyl radical having 1 to 15 carbon atoms which is unsubstituted, monosubstituted by CN or CF 3 or at least monosubstituted by halogen, where one or more CH 2 groups in these radicals are optionally, in each case independently of one another, replaced by —O—, —S—, —CO—, —CO—O—, —O—CO— or —O—CO—O in such a way that O atoms are not linked directly to one another, and the medium further comprises at least one compound of the formula Xc or Xd: wherein Alkyl is a straight-chain or branched alkyl group of 1–7 carbon atoms, and Alkenyl and Alkenyl* are, independently, a straight-chain or branched alkenyl group of 2–7 carbon atoms. wherein the medium exhibits a birefringence value of ≦0.065.