The liquid-crystalline phases according to the invention contain about 0.1 to 99, preferably 10 to 95%, of one or more compounds of the formula I. Further preferred liquid-crystalline phases are those which contain 0.1-50, in particular 0.5-30,% of one or more compounds of the formula I. It is also possible to use isotropic compounds of the formula I in the phases according to the invention.