Liquid-crystal medium

1. A liquid crystal medium comprising

a) one or more compounds of formula I

in which

R 1 and R 2 , identically or differently, denote H, halogen, straight chain alkyl or alkoxy having 1 to 15 C atoms, straight chain alkenyl or alkenyloxy having 2 to 15 C atoms or branched alkyl or alkoxy or alkenyl or alkenyloxy having 3 to 15 C atoms, where one or more CH 2 groups in these radicals may each be replaced, independently of one another, by

 —C≡C—, —CF 2 O—, —OCF 2 —, —CH═CH—, —O—, —CO—O— or —O—CO— in such a way that O atoms are not linked directly to one another,

A 0 , A 1 , and A 2 , each, independently of one another, denote phenylene-1,4-diyl, in which one or two CH groups may be replaced by N and one or more H atoms may be replaced by halogen, CN, CH 3 , CHF 2 , CH 2 F, CF 3 , OCH 3 , OCHF 2 or OCF 3 , or denote cyclohexane-1,4-diyl, in which one or two non-adjacent CH 2 groups may be replaced, independently of one another, by O and/or S and one or more H atoms may be replaced by F, or denote cyclohexene-1,4-diyl, bicyclo[1.1.1]-pentane-1,3-diyl, bicyclo[2.2.2]octane-1,4-diyl, spiro[3.3]heptane-2,6-diyl, tetrahydropyran-2,5-diyl or 1,3-dioxane-2,5-diyl,

Z 1 and Z 2 , each, independently of one another, denote —CF 2 O—, —OCF 2 —, —CH 2 O—, —OCH 2 —, —CO—O—, —O—CO—, —C 2 H 4 —, —C 2 F 4 , —CF 2 CH 2 —, —CH 2 CF 2 —, —CFHCFH—, —CFHCH 2 —, —CH 2 CFH—, —CF 2 CFH—, —CFHCF 2 —, —CH═CH—, —CF═CH—, —CH═CF—, —CF═CF—, —C≡C— or a single bond,

m denotes 0, 1, 2 or 3, and

n denotes 0, 1, 2 or 3;

and

b) one or more compounds selected from the group of compounds of formulae IIA, IIB, IIC and IID

in which

R 2A , R 2B , R 2C and R 2D identically or differently, denote H, straight chain alkyl or alkoxy having 1 to 15 C atoms, straight chain alkenyl or alkenyloxy having 2 to 15 C atoms or branched alkyl or alkoxy or alkenyl or alkenyloxy having 3 to 15 C atoms, where one or more CH 2 groups in these radicals may each be replaced, independently of one another, by

 —C≡C—, —CF 2 O—, —OCF 2 —, —CH═CH—, by —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,

L 1 and L 2 , each, independently of one another, denote F, Cl, CF 3 or CHF 2 ,

Y denotes H, F, Cl, CF 3 , CHF 2 or CH 3 ,

Z 2 , Z 2 B and Z 2 D each, independently of one another, denote a single bond, —CH 2 CH 2 —, —CH═CH—, —CF 2 O—, —OCF 2 —, —CH 2 O—, —OCH 2 —, —COO—, —OCO—, —C 2 F 4 —, —CF═CF— or —CH═CHCH 2 O—,

(O) denotes O or a single bond,

p denotes 0, 1 or 2,

q denotes 0 or 1, and

v denotes an integer from 1 to 6;

wherein the medium has negative dielectric anisotropy.

2. The liquid crystal medium according to claim 1 , wherein the total amount of the one or more compounds selected from the group of compounds of formulae IIA, IIB, IIC and IID is in the range of 9% to 70%.

3. The liquid crystal medium according to claim 1 , wherein the one or more compounds of formula I are selected from the group of compounds of formulae I-1 to I-6

in which R 1 and R 2 have the meanings given for formula I, L is halogen, CN, CH 3 , CHF 2 , CH 2 F, CF 3 , OCH 3 , OCHF 2 or OCF 3 , and r, s and t independently are 0, 1, 2, 3, or 4.

4. The liquid crystal medium according to claim 3 , wherein the group

in the formulae I-1 to I-6 denotes

5. The liquid crystal medium according to claim 1 , wherein the medium further comprises one or more compounds of formula III

in which

R 31 and R 32 each, independently of one another, denote H, an alkyl or alkoxy radical having 1 to 15 C atoms, where one or more CH 2 groups in these radicals may each be replaced, independently of one another, by

 —C≡C—, —CF 2 O—, —OCF 2 —, —CH═CH—, by —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,

A 31 on each occurrence, independently of one another, denotes

a) 1,4-cyclohexenylene or 1,4-cyclohexylene radical, in which one or two non-adjacent CH 2 groups may be replaced by —O— or —S—,

b) a 1,4-phenylene radical, in which one or two CH groups may be replaced by N, or

c) a radical selected from the group consisting of spiro[3.3]heptane-2,6-diyl, 1,4-bicyclo[2.2.2]octylene, naphthalene-2,6-diyl, decahydronaphthalene-2,6-diyl, 1,2,3,4-tetrahydronaphthalene-2,6-diyl, phenanthrene-2,7-diyl and fluorene-2,7-diyl,

where the radicals a), b) and c) may be mono- or polysubstituted by halogen atoms,

n denotes 0, 1 or 2,

Z 31 on each occurrence independently of one another denotes —CO—O—, —O—CO—, —CF 2 O—, —OCF 2 —, —CH 2 O—, —OCH 2 —, —CH 2 —, —CH 2 CH 2 —, —(CH 2 ) 4 —, —CH═CH—CH 2 O—, —C 2 F 4 —, —CH 2 CF 2 —, —CF 2 CH 2 —, —CF═CF—, —CH═CF—, —CF═CH—, —CH═CH—, —C≡C— or a single bond,

L 31 and L 32 each, independently of one another, denote F, Cl, CF 3 or CHF 2 , and

W denotes O or S.

6. The liquid crystal medium according to claim 5 , wherein W in formula III denotes S.

7. The liquid crystal medium according to claim 1 , wherein the medium further comprises one or more compounds of formula IV

in which

R 41 denotes an unsubstituted alkyl radical having 1 to 7 C atoms or an unsubstituted alkenyl radical having 2 to 7 C atoms, and

R 42 denotes an unsubstituted alkyl radical having 1 to 7 C atoms or an unsubstituted alkoxy radical having 1 to 6 C atoms, or an unsubstituted alkenyl radical having 2 to 7 C atoms.

8. The liquid crystal medium according to claim 1 , wherein the medium further comprises one or more compounds selected from the group consisting of compounds of formulae IV-3-1 and IV-3-2:

in which alkyl denotes n-alkyl having 1 to 7 C-atoms.

9. The liquid crystal medium according to claim 1 , wherein the medium further comprises one or more compounds of the formula V

in which

R 51 and R 52 denote, each independently, alkyl having 1 to 7 C atoms, alkoxy having 1 to 7 C atoms, or alkoxyalkyl, alkenyl or alkenyloxy having 2 to 7 C atoms,

 identically or differently, denote

Z 51 and Z 52 , identically or differently, denote —CH 2 —CH 2 —, —CH 2 —O—, —CH═CH—, —C≡C—, —COO— or a single bond, and

n is 1 or 2.

10. The liquid crystal medium according to claim 1 , wherein the medium has a birefringence of 0.105 or more.

11. The liquid crystal medium according to claim 1 , wherein the medium comprises a polymerisable compound.

12. A liquid crystal display comprising the liquid crystal medium according to claim 1 .

13. The liquid crystal display of claim 12 , wherein the display is a VA, IPS, FFS, PS-VA, PS-IPS or PS-FFS type display.

14. An energy saving display for gaming comprising the liquid crystal medium according to claim 1 .

15. A process of preparing a liquid crystal medium according to claim 1 , comprising mixing one or more compounds of formula I with one or more compounds selected from the group consisting of compounds of formulae IIA, IIB, IIC and IID, and optionally with a polymerisable compound or further liquid crystal compounds or additives.

16. The liquid crystal medium according to claim 1 , wherein the medium has a dielectric anisotropy Δε of −1.8 to −5.0.

17. The liquid crystal medium according to claim 1 , wherein the medium has a dielectric anisotropy Δε of −2.0 to −3.9.

18. The liquid crystal medium according to claim 1 , wherein the medium has a dielectric anisotropy Δε of −2.3 to −3.4.

19. The liquid crystal medium according to claim 1 , wherein the medium has a dielectric anisotropy Δε of −2.8 to −3.2.

20. The liquid crystal medium according to claim 1 , wherein the medium has a ratio of γ 1 /K 11 [mPas/pN] of 5.4 to 5.5.