Liquid-crystalline medium

Liquid-crystalline medium, characterised in that it comprises one or more compounds of the formula I,

• in which
• R1 and R2 each, independently of one another, denote an alkyl or alkoxy radical having 1 to 15 C atoms, where, in addition, one or more CH2 groups in these radicals may each be replaced independently of one another, by —C≡C—, —CF2O—, —CH═CH—,
• —O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another, and in which, in addition, one or more H atoms may be replaced by halogen, alternatively, R2 can also be H.