Patent ID: 7175891

Claim:
Liquid-crystalline medium based on a mixture of polar compounds of positive dielectric anisotropy, which comprises one or more compounds of the formula I: and one or more compounds of the formula IA in which the individual radicals have the following meanings: R 1 and R 2 are each, independently of one another, H, a halogenated or unsubstituted alkyl radical having from 1 to 15 carbon atoms, where one or more CH 2 groups in these radicals are optionally replaced, in each case independently of one another, by in such a way that O atoms are not linked directly to one another, X 1 is in each case, independently of one another, CN, SF 5, SCN, NCS, OCN, a halogenated alkyl radical, a halogenated alkenyl radical, a halogenated alkoxy radical or a halogenated alkenyloxy radical, each having up to 6 carbon atoms, X 2 is in each case, independently of one another, F, Cl, CN, SF 5, SCN, OCN, NCS, a halogenated alkyl radical, a halogenated alkenyl radical, a halogenated alkoxy radical or a halogenated alkenyloxy radical, each having up to 6 carbon atoms, Z 1 and Z 2 are each, independently of one another, —CF 2 O—, —OCF 2 — or a single bond, where Z 1 ≠Z 2 , are each, independently of one another, L 1-4 are each, independently of one another, H or F; with the proviso that, when Z 1 is —CF 2 O—, and Z 2 is not a single bond or with the proviso that, when Z 2 is —CF 2 O—, and Z 1 is not a single bond or