Fluorinated aromatic compounds

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, ZU3 identically or differently, denote —CH═CH—, —CF═CF—, —CH═CF—, —CF═CH—, —C≡C— or a single bond,
• X1, X2 identically or differently, denote H, Cl, F, CH3 or C2H5,
• Y1, Y2, Y3, Y4 identically or differently, denote H, F, Cl, or straight chain alkyl, or alkoxy, each having 1 to 12 C atoms or straight chain alkenyl or alkenyloxy, each having 2 to 12 C atoms or branched or cyclic alkyl, alkenyl, alkoxy or alkenyloxy, each having 3 to 12 C atoms, where at least one of Y1, Y2, Y3 and Y4 is different from F,
• s is 0, 1 or 2,
• t is 0, 1 or 2, and
• s+t is 0, 1 or 2,
• identically or differently, denote a radical selected from the following groups:
• a) 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,
• b) the group consisting of trans-1,4-cyclohexylene, 1,4-cyclohexenylene, bicyclo[1.1.1]pentane-1,3-diyl, 4,4″-bicyclohexylene, bicyclo[2.2.2]octane-1,4-diyl, 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, and
• c) the group consisting of thiophene-2,5-diyl, thieno[3,2-b]thiophene-2,5-diyl, 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, alkoxycarbonyl, 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.