DERIVATE DES 2,3-DIFLUORHYDROCHINONS

Derivatives of 2,3-difluorohydroquinone of formula (I) wherein R and R , independently, denote an unsubstituted C1-C15 or C3-C15 alkyl or C3-C15 alkenyl or a C1-15 alkyl or C3-C15 alkenyl monosubstituted by cyanogen or at least monosubstituted by fluorine or chlorine, whereby a CH2 group in these residues can also be substituted by -O-, -CO-, -CO-O-, -O-CO- or -O-CO-O-, A , A and A , independently, denote (a) trans-1,4-cyclohexylene, wherein one or two non-neighbouring CH2 groups can also be replaced by -O- and/or -S-; (b) 1,4-phenyle, wherein one or two CH groups can also be replaced by N; (c) a residue of the group consisting of piperidin-1,4-diyl, 1,4-bicyclo(2,2,2)octylen-1,3,4-thiadiazol-2,5-diyl, naphthalen-2,6-diyl, decahydronaphthalen-2,6-diyl and 1,2,3,4-tetrahydronaphthalen-2,6-diyl, where the residues (a) and (b) can be substituted one or more times by F, Cl, CH3 or CN; Z denotes -CO-O, -O-CO, -CH2-CH2-, -OCH2-, -CH2O-, -C=C- or a single bond; Q and Q , independently, denote -CO- or -CH2; m and n are each equal to 0, 1 or 2; and (m + n) is equal to 0, 1 or 2. These derivatives are useful as components of liquid crystal phases.