Liquid-crystalline compounds

A liquid-crystalline medium comprising at least two mesogenic compounds:

• wherein the medium contains substantially no compounds having a cyano group;
• wherein at least one mesogenic compound is a compound of the formula I
• in which
• R is vinyl, CH3CH═CH—, CH2═CHCH2CH2— or CH3CH═CHCH2CH2—,
• A1 and A2 are each, independently of one another,
• a) a 1,4-cyclohexenylene or 1,4-cyclohexylene radical, in which one or two non-adjacent CH2 groups are optionally replaced by —O— or —S—,
• b) a 1,4-phenylene radical, in which one or two CH groups are optionally replaced by N,
• c) a radical selected from the group consisting of piperidine-1,4-diyl, 1,4-bicyclo[2.2.2]octylene, phenanthrene-2,7-diyl, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl, phenanthrene-2,7-diyl and fluorene-2,7-diyl,
• where the radicals a), b) and c) are optionally mono- to perhalo-substituted by halogen atoms,
• X is F, Cl, NCS, SF5, or a halogenated or unsubstituted alkyl, alkoxy, alkenyloxy or alkenyl radical having 1 to 5 carbon atoms,
• Z1 and Z2 are each, independently of one another, —CO—O—, —O—CO—, —CF2O—, —OCF2—, —CH2O—, —OCH2—, —CH2CH2—, —(CH2)4—, —C2F4—, —CH2CF2—, —CF2CH2—, —CF═CF—, —CH═CH—, —C≡C— or a single bond,
• a is 0, 1 or 2,
• b is 0, 1 or 2,
• provided that a and b are not both 0 and that the compound contains at least one bridge Z1 or Z2 which is —CF2O— or —OCF2—, and
• L1, L2 and L3 are each, independently of one another, H, F or Cl;
• and
• wherein at least one other mesogenic compound is a compound of one of formulae IV or V:
• in which:
• R0 is n-alkyl, oxaalkyl, fluoroalkyl, alkenyloxy or alkenyl, each having 1 to 9 carbon atoms,
• X0 is halogenated alkoxy having 1 to 7 carbon atoms,
• Z0 is a single bond,
• Y1, Y2,
• Y3 and Y4 are each, independently of one another, H or F, and
• r is 0 or 1,
• provided that the variables are selected such that the compounds of formulae IV and V do not include compounds within the scope of formula I;
• and
• provided that the medium does not contain:
• a compound of the formula IV
• where R0 is alkenyl, Z0 is a single bond and r is 1, or
• a compound of formula RI where R0 alkenyl, formula RII, formula RIII, formula RIV where R0 is alkenyl, formula RV where R0 alkenyl, formula RIX where R0 alkenyl or formula RX where R0 alkenyl:
• wherein the above formulae, alkyl* is a straight-chain or branched alkyl radical having 1-9 carbon atoms, and alkenyl and alkenyl* are each, independently of one another, a straight-chain or branched alkenyl radical having up to 9 carbon atoms.