Liquid-crystalline compounds

A liquid-crystalline compound of the formula I

• 312
• in which
• R1 is an alkyl radical having from 1 to 15 carbon atoms which is unsubstituted, monosubstituted by CN or CF3 or mono-to per halo-substituted by halogen, where one or more CH2 groups in these radicals are optionally replaced by —O—, —S—, —CH═CH—, —C≡C—, —OC—O— or —O—CO— in such a way that 0 atoms are not linked directly to one another,
• 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 and 1,2,3,4-tetra-hydronaphthalene-2,6-diyl,
• where the radicals a), b) and c) are optionally monosubstituted or polysubstituted by halogen 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, with the proviso that at least one of Z1 and Z2 is —CF2O— or —OCF2—,
• a is 0, 1 or 2,
• b is 1 or 2, and
• L1, L2 and L3 are each, independently of one another, H, F or Cl.