Liquid-crystalline medium

A liquid-crystalline medium, comprising:

• at least one compound of the formula I,
• in which
• R denotes an alkyl or alkoxy radical having 1 to 15 C atoms, where one or more CH2 groups in these radicals may each be replaced, independently of one another, by —CF2O—,
• —O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another, and in which one or more H atoms may be replaced by halogen,
• R2 denotes H, an alkyl, or alkoxy radical having 1 to 15 C atoms, where one or more CH2 groups in these radicals may each be replaced, independently of one another, by —CF2O—, —CH═CH—,
• —O—, —CO—O— or —O—CO— in such a way that 0 atoms are not linked directly to one another, and in which one or more H atoms may be replaced by halogen;
• and
• at least two compounds of the formula
• wherein
• R0 denotes an alkyl or alkoxy radical having 1 to 15 C atoms, where one or more CH2 groups in these radicals may each be replaced, independently of one another, by —C≡C—, —CF2O—, —CH═CH—,
• —O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another, and in which one or more H atoms may be replaced by halogen,
• X0 denotes F, Cl, a mono- or polyhalogenated alkyl or alkoxy radical having 1 to 6 C atoms, a mono- or polyhalogenated alkenyl or alkenyloxy radical having 2 to 6 C atoms,
• Y1-6 each, independently of one another, denote H or F,
• Z0 denotes —C2H4—, —(CH2)4—, —CH═CH—, —CF═CF—, —C2F4—, —CH2CF2—, —CF2CH2—, —CH2O—, —OCH2—, —COO—, —CF2O—, —OCF2—, or a single bond, and
• r denotes 0 or 1, and
• denotes
• or at least one compound of formula I and at least one compound selected from the group consisting of compounds of formulas XIIa, XIIb, XIIc, IIIa, and IIIb,
• or at least one compound of formula I and at least one compound of the formula XI and at least one compound selected from the group consisting of compounds of formulas XIIa, XIIb, XIIc, IIIa, and IIIb,
• wherein R1 and R2 each, independently of one another, denote alkyl, alkenyl, alkoxy, oxaalkyl, fluoroalkyl or alkenyloxy, each having up to 9 C atoms, and preferably each, independently of one another, denote alkyl having 1 to 8 C atoms, and
• wherein R3a and R4a each, independently of one another, denote H, CH3, C2H5 or C3H7, and “alkyl” denotes a straight-chain alkyl group having 1 to 8 C atoms.