Liquid-crystalline medium and liquid-crystal display

1. A liquid-crystal medium, comprising:

a first dielectrically positive component, component A, comprising one or more dielectrically positive compounds of the formula I

in which

R 1 denotes alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl, alkenyloxy or alkoxyalkyl having 2 to 7 C atoms,

X 1 denotes —CN, halogen, halogenated alkyl or halogenated alkoxy having 1 to 3 C atoms or halogenated alkenyl or halogenated alkenyloxy having 2 or 3 C atoms,

Y 11 and Y 12 , independently of one another, denote H or F, and

L 11 to L 16 , independently of one another, denote H or F, and

optionally a further dielectrically positive component, component B, comprising one or more dielectrically positive compounds of the formulae II and III:

in which

R 2 and R 3 , independently of one another, denote alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms, alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms,

independently of one another, denote

L 21 , L 22 , L 31 and L 32 , independently of one another, denote H or F,

X 2 and X 3 , independently of one another, denote halogen, halogenated alkyl or alkoxy having 1 to 3 C atoms or halogenated alkenyl or alkenyloxy having 2 or 3 C atoms,

Z 3 denotes —CH 2 CH 2 —, —CF 2 CF 2 —,—COO—, trans-CH═CH—, trans-CF═CF—, —CH 2 O— or a single bond, and

l, m, n and o, independently of one another, denote 0 or 1, and

optionally a dielectrically neutral component, component C, comprising one or more dielectrically neutral compounds of the formula IV

in which

R 41 and R 42 , independently of one another, have the meaning indicated above for R 2 under formula II,

independently of one another and, if

occurs twice, also these independently of one another, denote

Z 41 and Z 42 , independently of one another and, if Z 41 occurs twice, also these independently of one another, denote —CH 2 CH 2 —, —COO—, trans-CH═CH—, trans-CF═CF—, —CH 2 O—, —CF 2 O—, —C≡C— or a single bond, and

p denotes 0, 1 or 2.

2. The liquid-crystal medium according to claim 1 , wherein the concentration of component A in the medium is in the range from 1% to 30%.

3. The liquid-crystal medium according to claim 1 , wherein component A comprises one or more compounds of the formula I in which X 1 denotes F.

4. The liquid-crystal medium according to claim 1 , comprising one or more compounds of the formula II.

5. The liquid-crystal medium according to claim 1 , comprising one or more compounds of the formula III.

6. The liquid-crystal medium according to claim 1 , comprising one or more dielectrically neutral compounds of the formula IV.

7. The liquid-crystal medium according to claim 1 , comprising a dielectrically neutral component, component D, comprising one or more dielectrically neutral compounds of the formula VI

in which

R 61 and R 62 , independently of one another, have the meaning indicated for R 2 ,

and, if it occurs twice, independently of one another on each occurrence, denotes

Z 61 and Z 62 , independently of one another and, if Z 61 occurs twice, also these independently of one another, denote —CH 2 CH 2 —, —COO—, trans-CH═CH—, trans-CF═CF—, —CH 2 O—, —CF 2 O—or a single bond, and

r denotes 0, 1 or 2.

8. The liquid-crystal display, comprising a liquid-crystal medium according to claim 1 .

9. The liquid-crystal display according to claim 8 , addressed by an active matrix.

10. The liquid-crystalline medium according to claim 1 , comprising a compound of formula IA-3.

11. The liquid-crystalline medium according to claim 1 , wherein X 1 is CF 3 or OCF 3 .

12. The liquid-crystalline medium according to claim 1 , wherein X 1 is CF 3 .