Patent ID: 7452575

Claim:
A liquid-crystalline medium having a helically twisted structure comprising a nematic component and an optically active component, wherein the optically active component comprises one or more chiral compounds whose helical twisting power and concentration are selected in such a way that the helical pitch of the medium is ≦1 μm, and the nematic component comprises at least 75% by weight of one or more compounds containing a 3,4,5-trifluorophenyl group selected from the following formulae in which Z 3 in each case, independently of one another, denotes COO, C 2 H 4 , CF 2 O or C 2 F 4 , and Z 4 in each case, independently of one another, denotes COO, CF 2 O, C 2 F 4 or a single bond, R 0 denotes H or an alkyl or alkenyl radical having 1 to 20 C atoms which is unsubstituted, monosubstituted by CN or CF 3 or at least monosubstituted by halogen, where, in addition, one or more CH 2 groups in these radicals may each, independently of one another, be replaced by —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —CH═CH— or —C≡C— in such a way that O atoms are not linked directly to one another, Y 3 to Y 4 each, independently of one another, denote H or F, Y 1 , Y 2 denote F, X 0 denotes F, and a denotes 0 or 1.