Liquid-crystal medium

Liquid-crystalline medium having negative dielectric anisotropy based on a mixture of polar compounds, which comprises:

• at least one compound of the formula I
• in which
• R1, R1* each, independently of one another, denote an alkyl radical having 1-6 C atoms, and
• a denotes 1;
• and
• at least one compound selected from the group of the compounds of the formulae IIB and IIC:
• in which
• R2B and R2C each, independently of one another, denote H, an alkyl radical having up to 15 C atoms which is unsubstituted, monosubstituted by CN or CF3 or at least monosubstituted by halogen, where, in addition, one or more CH2 groups in these radicals may be replaced by —O—,—S—,
• —C≡C—, —CF2O—, —OCF2—, —OC—O— or —O—CO— in such a way that O atoms are not linked directly to one another,
• L3 and L4 each, independently of one another, denote F or Cl,
• Z2 and Z2′ each, independently of one another, denote a single bond, —CH2CH2—, —CH═CH—, —CF2O—, —OCF2——CH2O—, —OCH2—, —COO—, —OCO—, —C2F4—, —CF═CF—, or —CH═CHCH2O—,
• q denotes 0, and
• v denotes 1 to 6.