Liquid crystalline medium

A liquid-crystalline medium containing a mixture of polar compounds having positive dielectric anisotropy, said medium comprising one or more alkenyl compounds of formula I

• and one or more compounds of formula IA
• wherein:
• R is a halogenated or unsubstituted alkyl or alkoxy radical having 1 to 15 carbon atoms, where one or more CH2 groups in these radicals are optionally, in each case independently of one another, replaced by —C≡C—, —CH═CH—, —O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another,
• R1 is an alkenyl radical having 2 to 7 carbon atoms,
• R2 is a halogenated or unsubstituted alkyl or alkoxy radical having 1 to 15 carbon atoms, where one or more CH2 groups in these radicals are optionally, in each case independently of one another, replaced by —C≡C—, —CH═CH—, —O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another or, if y is 1 or 2, R2 can also Q—Y,
• Q is CF2, OCF2, CFH, OCFH, OCHFCF2, OCF2CHFCF2 or a single bond,
• Y is F or Cl,
• X is F, Cl, CN, or a halogenated alkyl radical, a halogenated alkenyl radical, a halogenated alkoxy radical or a halogenated alkenyloxy radical, in each case having up to 6 carbon atoms,
• Z1 and Z2 are each, independently of one another, —CF2O—, —OCF2— or a single bond, where, if z=1, Z1≠Z2, and if z=0, Z1 is —CF2O— or —OCF2—,
• are each, independantly of one another,
• y is 0, 1 or 2,
• z is 0 or 1, and
• L1, L2, L3 and L4 are each, independently of one another, H or F, and wherein said medium does not contain cyanophenylcyclohexanes.