Aromatic isothiocyanates

A compound of formula U

• in which
• RU denotes H, alkyl or alkoxy having 1 to 12 C atoms, or alkenyl, alkenyloxy or alkoxyalkyl having 2 to 12 C atoms, in which one or more CH2 groups may be replaced by
• or a group RP,
• RP denotes halogen, CN, NCS, RF, RF—O— or RF—S—, wherein RF denotes fluorinated alkyl having 1 to 9 C atoms or fluorinated alkenyl having 2 to 9 C atoms,
• ZU1, ZU2 identically or differently, denote —CH═CH—, —CH═CF—, —CH═CF—, —CF═CH—, —C≡C— or a single bond,
• X1, X2,
• X3 and X4 identically or differently, denote Cl or F,
• t is 0 or 1, and
• identically or differently, denote a radical selected from:
• the group consisting of 1,4-phenylene, 1,4-naphthylene, and 2,6-naphthylene, in which one or two CH groups may be replaced by N and in which one or more H atoms may be replaced by L, wherein tetrafluoro-1,4-phenylene is excluded,
• b) the group consisting of trans-1,4-cyclohexylene, 1,4-cyclo-hexenylene, bicyclo[1.1.1]pentane-1,3-diyl, 4,4′-bicyclohexylene, bicyclo[2.2.2]octane-1,4-diyl, and spiro[3.3]heptane-2,6-diyl, in which one or more non-adjacent CH2 groups may be replaced by —O— and/or —S— and in which one or more H atoms may be replaced by F,
• c) the group consisting of thiophene-2,5-diyl, thieno[3,2-b]thiophene-2,5-diyl, and selenophene-2,5-diyl, each of which may also be mono- or polysubstituted by L,
• L on each occurrence, identically or differently, denotes F, Cl, CN, SCN, SF5 or straight-chain, in each case optionally fluorinated, alkyl, alkoxy, alkylcarbonyl, alkoxy-carbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 1 to 12 C atoms or branched, in each case optionally fluorinated, alkyl, alkoxy, alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxy having 3 to 12 C atoms.