Liquid-crystal medium, and electro-optical display containing the medium

A nematic liquid-crystal medium comprising:

• a) one or more dielectrically negative compound(s) of formula I
• in which
• R11 is alkoxy having 1 to 7 carbon atoms or alkenyloxy having 2 to 7 carbon atoms,
• and, in the case where
• R11 can also be alkyl having 1 to 7 carbon atoms;
• and
• R12 is alkyl having 1 to 7 carbon atoms, alkoxy having 1 to 7 carbon atoms, alkenyloxy having 2 to 7 carbon atoms,
• b) one or more dielectrically negative compound(s) of formula II
• in which
• R21 is alkyl having 1 to 7 carbon atoms, alkoxy having 1 to 7 carbon atoms, or alkenyloxy having 2 to 7 carbon atoms,
• R22 is alkyl having 1 to 7 carbon atoms, alkoxy having 1 to 7 carbon atoms, or alkenyloxy having 2 to 7 carbon atoms,
• Z21 and Z22 are, in each case, independently, —CH2—CH2—, —CH═CH—, —C≡C—, —COO— or a single bond,
• are, in each case independently,
• L21 and L22 are both C—F or one of the two is N and the other is C—F,
• I is 0 or 1,
• the compounds of the formulae I and III being excluded from the one or more dielectrically negative compound(s) of formula II,
• c) optionally one or more dielectrically negative compound(s) of the formula III
• in which
• R31 and R32 are each independently, alkyl having 1 to 7 carbon atoms, alkoxy having 1 to 7 carbon atoms or alkenyloxy having 2 to 7 carbon atoms,
• Z31 is —CH2—CH2—, —CH═CH—, —C≡C—, —COO— or a single bond,
• L31 and L32 are both C—F or one of the two is N and the other is C—F, and
• L33 and L34 are both C—F or one of the two is N and the other is C—F.