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 II to IX:
• 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 —CH═CH—, —C2H4—, —(CH2)4—, —C2F4—, —CF═CF—, —CF2O—, —OCF2— or —COO—,
• 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, V and VII do not include compounds within the scope of formula I;
• and
• provided that the medium does not contain:
• a compound of the formula II
• wherein R0 is alkenyl and r is 1,
• a compound of the formula IV
• where R0 is alkenyl, Z0 is a single bond and r is 1, or
• a compound of any of formulae RI—RV or RIX—RX:
• where R0 is alkenyl alkyl* are each, independently of one another, a straight-chain or branched alkyl radical having 1-9 carbon atoms,
• alkenyl and alkenyl* are each, independently of one another, a straight-chain or branched alkenyl radical having up to 9 carbon atoms and d is 0, 1 or 2.