A liquid-crystal medium comprising one or more compounds of formula I P-Sp-(A 2 -Z 2 -A 1) m1 -Z 1 -T I wherein the individual radicals, independently of each other, and on each occurrence identically or differently, have the following meanings T a group selected from the following formulae R a-f straight chain or branched alkyl with 1 to 10 C atoms, R g H or straight chain or branched alkyl with 1 to 10 C atoms, or benzyl, P vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane or epoxy, Sp a spacer group or a single bond, A 1, A 2 an alicyclic, heterocyclic, aromatic or heteroaromatic group with 4 to 30 ring atoms, which may also contain fused rings, and is optionally substituted by one or more groups L or R-(A 3 -Z 3) m2 -, and one of A 1 and A 2 may also denote a single bond, A 3 an alicyclic, heterocyclic, aromatic or heteroaromatic group with 4 to 30 ring atoms, which may also contain fused rings, and is optionally substituted by one or more groups L, Z 1 -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -OCH 2 -, -CH 2 O-, -SCH 2 -, -CH 2 S-, -CF 2 O-, -OCF 2 -, -CF 2 S-, -SCF 2 -, -(CH 2) n -, -CF 2 CH 2 -, -CH 2 CF 2 -, -(CF 2) n -, -CH=CH-, -CF=CF-, -CH=CF-, -CF=CH-, -C≡C-, -CH=CH-CO-O-, -O-CO-CH=CH-, -CH 2 -CH 2 -CO-O-, -O-CO-CH 2 -CH 2 -, -CR 00 R 000 -, or a single bond, with the proviso that, if m1 is 0 and Sp is a single bond, Z 1 is a single bond, Z 2, Z 3 -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -OCH 2 -, -CH 2 O-, -SCH 2 -, -CH 2 S-, -CF 2 O-, -OCF 2 -, -CF 2 S-, -SCF 2 -, -(CH 2) n -, -CF 2 CH 2 -, -CH 2 CF 2 -, -(CF 2) n -, -CH=CH-, -CF=CF-, -CH=CF-, -CF=CH-, -C≡C-, -CH=CH-CO-O-, -O-CO-CH=CH-, -CH 2 -CH 2 -CO-O-, -O-CO-CH 2 -CH 2 -, -CR 00 R 000 -, or a single bond, R 00, R 000 H or alkyl having 1 to 12 C atoms, R P-Sp-, H, F, Cl, CN, or straight chain, branched or cyclic alkyl having 1 to 25 C atoms, wherein one or more non-adjacent CH 2 -groups are optionally replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a manner that O- and/or S-atoms are not directly connected with each other, and wherein one or more H atoms are each optionally replaced by F, Cl or P-Sp-, or R is a group selected from formula 1, 2, 3 and 4, L P-Sp-, F, Cl, CN, or straight chain, branched or cyclic alkyl having 1 to 25 C atoms, wherein one or more non-adjacent CH 2 -groups are optionally replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a manner that O- and/or S-atoms are not directly connected with each other, and wherein one or more H atoms are each optionally replaced by F, Cl or P-Sp-, or L is a group selected from formula 1, 2, 3 and 4, m1 1, 2, 3 or 4, m2 0, 1, 2, 3 or 4, n 1, 2, 3 or 4, characterized in that -(A 2 -Z 2 -A 1) m1 - denotes benzene, biphenylene, p-terphenylene (1,4-diphenylbenzene), m-terphenylene (1,3-diphenylbenzene), naphthylene, 2-phenyl-naphthylene, phenanthrene or anthracene, all of which are optionally substituted by one or more groups L. T a group selected from the following formulae R a-f straight chain or branched alkyl with 1 to 10 C atoms, R g H or straight chain or branched alkyl with 1 to 10 C atoms, or benzyl, P vinyloxy, acrylate, methacrylate, fluoroacrylate, chloroacrylate, oxetane or epoxy, Sp a spacer group or a single bond, A 1, A 2 an alicyclic, heterocyclic, aromatic or heteroaromatic group with 4 to 30 ring atoms, which may also contain fused rings, and is optionally substituted by one or more groups L or R-(A 3 -Z 3) m2 -, and one of A 1 and A 2 may also denote a single bond, A 3 an alicyclic, heterocyclic, aromatic or heteroaromatic group with 4 to 30 ring atoms, which may also contain fused rings, and is optionally substituted by one or more groups L, Z 1 -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -OCH 2 -, -CH 2 O-, -SCH 2 -, -CH 2 S-, -CF 2 O-, -OCF 2 -, -CF 2 S-, -SCF 2 -, -(CH 2) n -, -CF 2 CH 2 -, -CH 2 CF 2 -, -(CF 2) n -, -CH=CH-, -CF=CF-, -CH=CF-, -CF=CH-, -C≡C-, -CH=CH-CO-O-, -O-CO-CH=CH-, -CH 2 -CH 2 -CO-O-, -O-CO-CH 2 -CH 2 -, -CR 00 R 000 -, or a single bond, with the proviso that, if m1 is 0 and Sp is a single bond, Z 1 is a single bond, Z 2, Z 3 -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O-, -OCH 2 -, -CH 2 O-, -SCH 2 -, -CH 2 S-, -CF 2 O-, -OCF 2 -, -CF 2 S-, -SCF 2 -, -(CH 2) n -, -CF 2 CH 2 -, -CH 2 CF 2 -, -(CF 2) n -, -CH=CH-, -CF=CF-, -CH=CF-, -CF=CH-, -C≡C-, -CH=CH-CO-O-, -O-CO-CH=CH-, -CH 2 -CH 2 -CO-O-, -O-CO-CH 2 -CH 2 -, -CR 00 R 000 -, or a single bond, R 00, R 000 H or alkyl having 1 to 12 C atoms, R P-Sp-, H, F, Cl, CN, or straight chain, branched or cyclic alkyl having 1 to 25 C atoms, wherein one or more non-adjacent CH 2 -groups are optionally replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a manner that O- and/or S-atoms are not directly connected with each other, and wherein one or more H atoms are each optionally replaced by F, Cl or P-Sp-, or R is a group selected from formula 1, 2, 3 and 4, L P-Sp-, F, Cl, CN, or straight chain, branched or cyclic alkyl having 1 to 25 C atoms, wherein one or more non-adjacent CH 2 -groups are optionally replaced by -O-, -S-, -CO-, -CO-O-, -O-CO-, -O-CO-O- in such a manner that O- and/or S-atoms are not directly connected with each other, and wherein one or more H atoms are each optionally replaced by F, Cl or P-Sp-, or L is a group selected from formula 1, 2, 3 and 4, m1 1, 2, 3 or 4, m2 0, 1, 2, 3 or 4, n 1, 2, 3 or 4,