Liquid crystal medium and liquid crystal display

1. A liquid-crystal medium having positive dielectric anisotropy (Δε) in the range from 12 to 17 at 20° C. and 1 kHz,

comprising

a) a compound of the formula below,

and

b) a liquid crystal mixture comprising one or more compounds of formula II in a concentration of 33% to 60% by weight based on the weight of the liquid crystal mixture as a whole and one or more compounds of formula II-2;

in which

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

on each appearance, independently of one another, denote

L 21 L 22 , L 23 and L24 independently of one another, denote H or F,

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

and

m denotes 0, 1, 2 or 3

wherein the total concentration of the compound of the following formula

in the medium is in the range from 1 ppm to 2000 ppm.

2. The liquid-crystal medium according to claim 1 , which additionally comprises one or more compounds of formula III

in which

R 3 denotes alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms,

on each appearance, independently of one another, denote

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

X 3 denotes 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

N denotes 0, 1, 2 or 3.

3. The liquid-crystal medium according to claim 1 , which additionally comprises one or more compounds of formula IV

in which

R 41 and R 42 independently of one another, denote alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms,

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.

4. The liquid-crystal medium according to claim 2 , which additionally comprises one or more compounds of formula IV

in which

R 41 and R 42 independently of one another, denote alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms,

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.

5. The liquid-crystal medium according to claim 1 , further comprising a stabilizer compound that is a di-ortho-(tert-butyl)phenol compound, which contains a structural element of the following formula

6. The liquid-crystal medium according to claim 1 , further comprising a stabilizer compound of the following formula

wherein n is 1-7.

7. The liquid-crystal medium according to claim 1 , which additionally comprises one or more compounds of formula I,

in which

n denotes an integer from 1 to 4,

m denotes (4−n),

denotes an organic radical having 4 bonding sites, in which, in addition to the m groups R 12 present in the molecule, but independently thereof, a further H atom may be replaced by R 12 or a plurality of further H atoms may be replaced by R 12 , in which one —CH 2 — group or a plurality of —CH 2 — groups may be replaced by —O— or —(C═O)— in such a way that two O atoms are not bonded directly to one another, or denotes a substituted or unsubstituted aromatic or heteroaromatic hydrocarbon radical having 1 to 4 valences, in which, in addition to the m groups R 12 present in the molecule, but independently thereof, a further H atom may be replaced by R 12 or a plurality of further H atoms may be replaced by R 12 ,

Z 11 and Z 12 independently of one another, denote —O—, —(C═O)—, —(N—R 14 )— or a single bond, but do not both simultaneously denote —O—,

r and s independently of one another, denote 0 or 1,

Y 11 to Y 14 each, independently of one another, denote alkyl having 1 to 4 C atoms and alternatively, independently of one another, one or both of the pairs Y 11 and Y 12 and/or Y 13 and Y 14 together also denote a divalent group having 3 to 6 C atoms,

R 11 denotes O.,

R 12 on each occurrence, independently of one another, denotes H, F, OR 14 , NR 14 R 15 , a straight-chain alkyl having 1-20 C atoms or branched alkyl chain having 3-20 C atoms, in which one —CH 2 — group or a plurality of —CH 2 — groups may be replaced by —O— or —C(═O)—, but two adjacent —CH 2 — groups cannot be replaced by —O—, or denotes a hydrocarbon radical which contains a cycloalkyl having 3 to 10 C atoms or alkylcycloalkyl unit having 4 to 10 C atoms, and in which one —CH 2 — group or a plurality of —CH 2 — groups may be replaced by —O— or —C(═O)—, but two adjacent —CH 2 — groups cannot be replaced by —O—, and in which one H atom or a plurality of H atoms may be replaced by OR 14 , N(R 14 )(R 15 ) or R 16 , or denotes an aromatic or heteroaromatic hydrocarbon radical, in which one H atom or a plurality of H atoms may be replaced by OR 14 , N(R 14 )(R 15 ) or R 16 ,

R 13 on each occurrence, independently of one another, denotes a straight-chain alkyl having 1-20 C atoms or branched alkyl chain having 3-20 C atoms, in which one —CH 2 — group or a plurality of —CH 2 — groups may be replaced by —O— or —C(═O)—, but two adjacent —CH 2 — groups cannot be replaced by —O—, or denotes a hydrocarbon radical which contains a cycloalkyl having 3 to 10 C atoms or alkylcycloalkyl unit having 4 to 10 C atoms, and in which one —CH 2 — group or a plurality of —CH 2 — groups may be replaced by —O— or —C(═O)—, but two adjacent —CH 2 — groups cannot be replaced by —O—, and in which one H atom or a plurality of H atoms may be replaced by OR 14 , N(R 14 )(R 15 ) or R 16 , or denotes an aromatic or heteroaromatic hydrocarbon radical, in which one H atom or a plurality of H atoms may be replaced by OR 14 , N(R 14 )(R 15 ) or R 16 , or can be 1,4-cyclohexylene of the following formula

in which one or more —CH 2 — groups may be replaced by —O—, —CO— or —NR 14 —, or an acetophenyl, isopropyl or 3-heptyl radical,

R 14 on each occurrence, independently of one another, denotes a straight-chain alkyl having 1 to 10 C atoms or branched-chain alkyl having 3 to 10 C atoms or acyl group having 1 to 10 C atoms or an aromatic hydrocarbon or carboxyl radical having 6-12 C atoms,

R 15 on each occurrence, independently of one another, denotes a straight-chain alkyl having 1 to 10 C atoms or branched-chain alkyl having 3 to 10 C atoms or acyl group having 1 to 10 C atoms or an aromatic hydrocarbon or carboxyl radical having 6-12 C atoms,

R 16 on each occurrence, independently of one another, denotes a straight-chain alkyl having 1 to 10 C atoms or branched-chain alkyl group having 3 to 10 C atoms, in which one —CH 2 — group or a plurality of —CH 2 — groups may be replaced by —O— or —C(═O)—, but two adjacent —CH 2 — groups cannot be replaced by —O—,

with the provisos that,

in the case where n=1, and

—[Z 11 —] r —[Z 12 —] s —═—O—, —(CO)—O—, —O—(CO)—, —O—(CO)—O—, —NR 14 or

—NR 14 —(CO)—,

does not denote

straight-chain alkyl having 1 to 10 C atoms or branched-chain alkyl having 3 to 10 C atoms, also cycloalkyl having 3 to 10 C atoms, cycloalkylalkyl having 4 to 10 C atoms or alkylcycloalkyl having 1 to 10 C atoms, where in all these groups one or more —CH 2 — groups may be replaced by —O— in such a way that no two O atoms in the molecule are bonded directly to one another,

in the case where n=2,

does not denote

8. The medium according to claim 7 , comprising

one or more compounds of formula III

in which

R 3 denotes alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms,

on each appearance, independently of one another, denote

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

X 3 denotes 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

n denotes 0, 1, 2 or 3.

9. The medium according to claim 8 , which comprises more than one compound of the formula II and one or more compounds of formula II-2.

10. The medium according to claim 8 , which comprises more than one compound of the formula III.

11. The liquid-crystal medium according to claim 8 , which additionally comprises one or more compounds of formula IV

in which

R 41 and R 42 independently of one another, denote alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 C atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms,

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.

12. The liquid-crystal medium according to claim 8 , wherein joint concentration of the compounds of formulae II and III within the liquid crystal medium ranges from 49% to 60% by weight based on the weight of the whole liquid crystal medium.

13. The medium according to claim 7 , comprising

one or more compounds of formula IV

in which

R 41 and R 42 independently of one another, denote alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 carbon atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 carbon atoms,

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.

14. The medium according to claim 7 , wherein the total concentration of the compounds of formula I and the compound of the following formula

in the medium combined is in the range from 1 ppm to 2000 ppm.

15. The medium according to claim 7 , wherein the compounds of the formula I are compounds selected from the group of the compounds of the formulae I-1 to I-9

t denotes an integer from 1 to 12,

R 17 denotes a straight-chain alkyl having 1 to 12 C atoms or branched alkyl chain having 3-12 C atoms, in which one —CH 2 — group or a plurality of —CH 2 — groups may be replaced by —O— or —C(═O)—, but two adjacent —CH 2 — groups cannot be replaced by —O—, or denotes an aromatic or heteroaromatic hydrocarbon radical, in which one H atom or a plurality of H atoms may be replaced by OR 14 , N(R 14 )(R 15 ) or R 16 .

16. The medium according to claim 7 , comprising one or more dielectrically neutral compounds of formula V

in which

R 51 and R 52 independently of one another, denote alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 carbon atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 carbon atoms,

on each occurrence, independently of one another, denotes

Z 51 and Z 52 independently of one another and, if Z 51 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.

17. A liquid-crystal display, containing the medium according to claim 7 .

18. The display according to claim 17 , which is addressed by an active matrix.

19. A method of using a medium according to claim 7 , comprising operating said medium in a liquid-crystal display to generate an image in said display.

20. A process for the preparation of the medium according to claim 7 , wherein the compound of the following formula

is mixed with one or more compounds of formula I, one or more compounds of formula II, one or more compounds of formula II-2 and with

i) one or more compounds of formula III,

ii) one or more compounds of formula IV,

iii) one or more further mesogenic compounds, or

iv) one or more additives

or a combination thereof,

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, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 C atoms,

on each appearance, 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

m and n independently of one another, denote 0, 1, 2 or 3,

in which

R 41 and R 42 independently of one another, denote alkyl, alkoxy, fluorinated alkyl or fluorinated alkoxy having 1 to 7 carbon atoms, or alkenyl, alkenyloxy, alkoxyalkyl or fluorinated alkenyl having 2 to 7 carbon atoms,

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.