Liquid crystal medium

1. A liquid crystal medium comprising one or more compounds selected from formulae I-1 and I-2

in which

R L1 denotes H, or a straight chain alkyl or alkoxy radical having 1 to 15 C atoms or branched alkyl or alkoxy radical 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, and in which, in addition, one or more H atoms may each be replaced by halogen,

and

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

in which

R 2A , R 2B , R 2C

and R 2D each, independently of one another, denote H, or an alkyl radical having 1 to 15 C atoms or an alkenyl radical having 2 to 15 C atoms which, in each case, is unsubstituted, monosubstituted by CN or CF 3 or at least monosubstituted by halogen, where, in addition, one or more CH 2 groups in these radicals may each be replaced by —O—, —S—,

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

L 1 to L 4 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 2B and Z 2D 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—,

p denotes 0, 1 or 2,

q denotes 0 or 1, and

v denotes 1, 2, 3, 4, 5, or 6,

wherein said medium has a negative dielectric anisotropy,

wherein the total concentration of compounds of formula I-1 and I-2 in said medium is 0.5% to 2%,

wherein the medium further comprises one or more compounds of formula III

in which

R 11 and R 12 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, in addition, one or more H atoms may each be replaced by halogen,

A 1 on each occurrence independently denotes

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

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

c) a radical from the group 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 is 0, 1 or 2,

Z 1 on each occurrence independently 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, and

L 11 and L 12 each, independently of one another, denote H, F, Cl, CF 3 or CHF 2 , and

W denotes S, and

wherein the mixtures X-1 and X-2 having the following compositions

Mixture X-1:

    8%

   20%

 10.5%

  2.0%

  0.5%

 11.0%

  7.5%

  1.0%

 10.5%

 15.5%

  3.5%

 10.0%

Σ

100.0%

Mixture X-2

  2.0%

  4.0%

 37.0%

  3.0%

 14.5%

 11.5%

  3.0%

 10.0%

 14.0%

  1.0%

Σ

100.0%

are excluded.

2. The medium according to claim 1 , wherein the medium comprises one or more compounds of formula IV

in which

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

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

3. The medium according to claim 1 , wherein the medium comprises one or more compounds selected from the group of compounds of the following formulae:

4. The medium according to claim 1 , wherein the medium comprises one or more compounds of formula IVb-1 to IVb-3

in which

alkyl and alkyl* each, independently of one another, denote alkyl having 1 to 6 C atoms, and

alkenyl and alkenyl* each, independently of one another, denote alkenyl having 2 to 6 C atoms.

5. The medium according to claim 1 , wherein the medium comprises one or more compounds of formula V

in which

R 51 , R 52 denote 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 , Z 52 each, independently of one another, denote —CH 2 —CH 2 —, —CH 2 —O—, —CH═CH—, —C≡C—, —COO— or a single bond, and

n is 1 or 2.

6. The medium according to claim 1 , wherein the medium comprises a chiral dopant.

7. The medium according to claim 1 , wherein the medium comprises one or more polymerizable compounds of formula P

P-Sp-A 1 -(Z 1 -A 2 ) z -R  P

in which

P denotes a polymerizable group,

Sp denotes a spacer group or a single bond,

A 1 , A 2 identically or differently, denote an aromatic, heteroaromatic, alicyclic or heterocyclic group, which may also contain fused rings, and which is unsubstituted, or mono- or polysubstituted by L,

L denotes F, Cl, —CN, P—Sp-,_ or straight chain alkyl having 1 to 25 C atoms or branched or cyclic alkyl having 3 to 25 C atoms, wherein one or more non-adjacent CH 2 — groups are each optionally replaced by —O—, —S—, —CO—, —CO—O—, —O—CO—, or —O—CO—O— in such a manner that O- and/or S-atoms are not directly connected with each other, and wherein one or more H atoms are each optionally replaced by P-Sp-, F or Cl,

Z 1 denotes —O—, —S—, —CO—, —CO—O—, —O—CO—, —O—CO—O—, —OCH 2 —, —CH 2 O—, —SCH 2 —, —CH 2 S—, —CF 2 O—, —OCF 2 —, —CF 2 S—, —SCF 2 —, —(CH 2 ) n1 —, —CF 2 CH 2 —, —CH 2 CF 2 —, —(CF 2 ) n1 —, —CH═CH—, —CF═CF—, —CH═CF—, —CF═CH—, —C≡C—, —CH═CH—CO—O—, —O—CO—CH═CH—, —CH 2 —CH 2 —CO—O—, —O—CO—CH 2 —CH 2 —, —CR 0 R 00 —, or a single bond,

R 0 , R 00 identically or differently, denote H or alkyl having 1 to 12 C atoms,

R denotes H, L, or P-Sp-,

z is 0, 1, 2 or 3,

n1 is 1, 2, 3 or 4.

8. The medium according to claim 7 , wherein the polymerizable compounds of formula P are polymerized.

9. A process of preparing a liquid crystal medium according to claim 1 , comprising:

mixing together one or more compounds selected from formulae I-1 and I-2 of claim 1 , one or more compounds selected from formulae IIA, IIB, IIC, and IID of claim 1 , one or more compounds of formula III, one or more mesogenic or liquid-crystalline compounds other than compounds of formulae I-1, I-2, IIA, IIB, IIC, and IID, optionally a polymerizable compound, and optionally one or more additives.

10. A liquid crystal display comprising a medium according to claim 1 .

11. The liquid crystal display according to claim 10 , wherein the display is a PSA display.

12. The liquid crystal display according to claim 11 , wherein the display is a PS-VA, PS-IPS, PS-FFS, PS-UB-FFS, polymer stabilized SA-VA or polymer stabilized SA-FFS display.

13. The liquid crystal display according to claim 10 , wherein the display is a VA, IPS, U-IPS, FFS, UB-FFS, SA-FFS or SA-VA display.

14. A method of generating an electro-optical effect comprising applying a voltage to a display according to claim 10 .

15. The medium according to claim 1 , wherein the medium has a dielectric anisotropy Δε of −1.5 to −8.0.

16. The medium according to claim 1 , wherein the medium has a dielectric anisotropy Δε of −2.0 to −4.0.

17. The medium according to claim 1 , wherein the medium has a dielectric anisotropy Δε of −2.5 to −3.5.

18. The medium according to claim 1 , wherein the amount of compounds having a dielectric anisotropy of Δε≥1.5 in said medium is ≤20% by weight.

19. The medium according to claim 1 , wherein the total concentration of compounds of formula I-1 and I-2 in said medium is 0.5% to 1%.