Ferroelectric liquid-crystalline medium

The invention relates to a ferroelectric liquid-crystalline medium having at least two liquid-crystalline components, characterised in that this contains at least one compound of formula I in which R and R are each, independently of one another, an alkyl group or a polyfluoroalkyl group, in each case having 1 to 15 carbon atoms, and in which, in addition, one or more CH2 groups or CF2 groups may be replaced by a group selected from the series consisting of -O-, -S-, -CO-, -CH-halogen, -CHCN-, -O-CO-, -O-COO-, -CO-O- and -CH=CH- or by a combination of two suitable groups, where two heteroatoms are not linked directly to one another, and R is alternatively halogen, A and A are each, independently of one another, 1,4-cyclohexylene which is unsubstituted or monosubstituted or polysubstituted by halogen atoms, CH3 groups and/or nitrile groups, and in which one or two non-adjacent CH2 groups may be replaced by -O- and/or -S- and/or -CH-CH2-group may be replaced by -C=N- (Cy), or are 1,4-phenylene which is unsubstituted or monosubstituted or polysubstituted by halogen atoms, CH3 groups and/or nitrile groups and in which, in addition, one or more CH groups may be replaced by N, and Z and Z are each, independently of one another, -CO-O, -O-CO-, -CH2O-, -OCH2- or -CH2CH2-.