Modified nematic mixtures with positive dielectric anisotropy

Claim 2

A modified liquid crystal nematic mixture having positive dielectric anisotropy and an enantiotropic nematic mesophase of about 20° to 80° C. extending over temperatures from 0° to 30° C., comprising an admixture of: a. at least one nematic compound of the formula ##STR6## wherein A is azoxy or carbonyloxy and R 1 and R 2 are each straight-chain alkyl or alkoxy of 1-8 carbon atoms; and b. at least one compound of the formula X - R - Y wherein X is dialkylamino of 2-4 carbon atoms; Y is cyano, nitro or trifluoromethyl; and R is selected from the group consisting of divalent radicals of the formulae ##STR7## characterized in that component (b) is present in an amount sufficient to increase the dielectric anisotropy of the admixture to a value of at least +2.

Claim 3

A modified nematic mixture according to claim 1, comprising 65-99% by weight of (a) and correspondingly 35-1% by weight of (b).

Claim 4

A modified nematic mixture according to claim 2, comprising 70-95% by weight of (a) and correspondingly 30-5% by weight of (b).

Claim 5

A modified nematic mixture according to claim 1, wherein R has the structure 2c or 2d and Y is cyano.

Claim 6

A modified nematic mixture according to claim 1, wherein R has the structure 2a or 2b and Y is cyano.

Claim 7

A modified nematic mixture according to claim 5, wherein X is dimethylamino.

Claim 8

A modified nematic mixture according to claim 1, wherein component (b) is 4-dimethylaminobenzonitrile.

Claim 9

A modified nematic mixture according to claim 1, wherein component (a) is one in which at least one of R 1 and R 2 is straight-chain alkyl.

Claim 10

A modified nematic mixture according to claim 8, wherein component (a) is selected from the group consisting of 4-n-buty-4'-methoxy-azoxybenzene, 4-ethyl-4'-methoxyazoxybenzene and mixtures thereof.

Claim 11

A modified nematic mixture according to claim 8, wherein component (a) is selected from the group consisting of the 4-n-pentylphenyl ester of anisic acid, the 4'-pentylphenyl ester of 4-n-hexoxybenzoic acid and mixtures thereof.

Claim 12

A modified liquid crystal nematic mixture having positive dielectric anisotropy and an enantiotropic nematic mesophase of about 20° to 80° C. extending over temperatures from 0° to 30° C., comprising an admixture of: a. 20-95% by weight of at least one nematic compound of the formula ##STR8## wherein A is azoxy or carbonyloxy and R 1 and R 2 are each straight-chain alkyl or alkoxy of 1-8 carbon atoms; b. 3-65% by weight of at least one compound of the formula X -- R -- Y wherein X is straight-chain alkyl of 4-9 carbon atoms or dialkylamino of 2-4 carbon atoms; Y is cyano, nitro or trifluoromethyl when X is dialkylamino, and Y is nitro or trifluoromethyl when X is straight-chain alkyl; and R is selected from the group consisting of divalent radicals of the formulae ##STR9## characterized in that component (b) is present in an amount sufficient to increase the dielectric anisotropy of the admixture to a value of at least +2; and c. 2-27% by weight based on the total composition of at least one compound of the formula ##STR10## wherein R 1 and R 2 are each alkyl or alkoxy of 1-8 carbon atoms, said component (c) being present in an amount sufficient to compensate the clearing-point-lowering effect of the addition of component (b) to the nematic component (a).

Claim 13

A modified liquid crystal nematic mixture having positive dielectric anisotropy and an enantiotropic nematic mesophase of about 20° to 80° C. extending over temperatures from 0° to 30° C., comprising an admixture of: a. 20-95% by weight of at least one nematic compound of the formula ##STR8## wherein A is azoxy or carbonyloxy and R 1 and R 2 are each straight-chain alkyl or alkoxy of 1-8 carbon atoms; b. 3-65% by weight of at least one compound of the formula X -- R -- Y wherein X is straight-chain alkyl of 4-9 carbon atoms or dialkylamino of 2-4 carbon atoms; Y is cyano, nitro or trifluoromethyl when X is dialkylamino, and Y is nitro or trifluoromethyl when X is straight-chain alkyl; and R is selected from the group consisting of divalent radicals of the formulae ##STR9## characterized in that component (b) is present in an amount sufficient to increase the dielectric anisotropy of the admixture to a value of at least +2; and c. 2-27% by weight based on the total composition of at least one compound of the formula ##STR10## wherein R 1 and R 2 are each alkyl or alkoxy of 1-8 carbon atoms, said component (c) being present in an amount sufficient to compensate the clearing-point-lowering effect of the addition of component (b) to the nematic component (a).

Claim 14

A modified nematic mixture according to claim 11 comprising 45-80% by weight of (a); 10-45% by weight of (b); and 10-25% by weight of (c).

Claim 15

A modified nematic mixture according to claim 11, wherein at least one of R 1 and R 2 of component (c) is straight-chain alkyl of 4-8 carbon atoms.

Claim 16

A modified nematic mixture according to claim 13, wherein component (c) is selected from the group consisting of the 4'-n-butylphenyl ester of 4-anisoyloxybenzoic acid, the 4'-n-butylphenyl ester of 4-(4-n-hexoxybenzoyloxy)-benzoic acid, the 4'-n-butylphenyl ester of 4-(4-n-butylbenzoyloxy)benzoic acid and mixtures thereof.

Claim 17

In a liquid crystal electrooptical cell comprising transparent or translucent electrodes surrounding a dielectric nematic composition having a homogeneous orientation, the improvement wherein said nematic composition is the modified nematic mixture of claim 1.

Claim 18

In a liquid crystal electrooptical cell comprising transparent or translucent electrodes surrounding a dielectric nematic composition having a homogenous orientation, the improvement wherein said nematic composition is the modified nematic mixture of claim 11.

Claim 19

A process for increasing the dielectric anistropy of a nematic substance consisting of at least one compound of the formula ##STR11## wherein A is azoxy or carbonyloxy and R 1 and R 2 are each straight-chain alkyl or alkoxy of 1-8 carbon atoms, which comprises admixing therewith at least one compound of the formula X -- R -- Y wherein X is dialkylamino of 2-4 carbon atoms; Y is cyano, nitro or trifluoromethyl; and R is selected from the group consisting of divalent radicals of the formulae ##STR12## in an amount sufficient to increase the dielectric anisotropy to a value of at least +2.

Claim 20

A process for increasing the dielectric anistropy of a nematic substance consisting of at least one compound of the formula ##STR11## wherein A is azoxy or carbonyloxy and R 1 and R 2 are each straight-chain alkyl or alkoxy of 1-8 carbon atoms, which comprises admixing therewith at least one compound of the formula X -- R -- Y wherein X is dialkylamino of 2-4 carbon atoms; Y is cyano, nitro or trifluoromethyl; and R is selected from the group consisting of divalent radicals of the formulae ##STR12## in an amount sufficient to increase the dielectric anisotropy to a value of at least +2.

Claim 21

A process according to claim 17, further comprising admixing at least one compound of the formula ##STR13## wherein R 1 and R 2 are each alkyl or alkoxy of 1-8 carbon atoms, in an amount sufficient to compensate the clearing-point-lowering effect of the admixture of the compound of the formula X -- R -- Y.

Claim 22

a modified nematic mixture according to claim 5, comprising 20-95% by weight of (a); 3-65% by weight of (b); and (c) 2-27% by weight based on the total composition of at least one compound of the formula ##STR14## wherein R 1 and R 2 are each alkyl or alkoxy of 1-8 carbon atoms, said component (c) being present in an amount sufficient to compensate the clearing-point-lowering effect of the addition of component (b) to the nematic component (a).

Claim 23

A modified nematic mixture according to claim 19, comprising 45-80% by weight of (a); 10-45% by weight of (b); and 10-25% by weight of (c).

Claim 24

A modified nematic mixture according to claim 19, wherein at least one of R 1 and R 2 of component (c) is straight-chain alkyl of 4-8 carbon atoms.

Claim 25

A modified nematic mixture according to claim 19, wherein component (c) is selected from the group consisting of the 4'-n-butylphenyl ester of 4-anisoyloxybenzoic acid, the 4'-n-butylphenyl ester of 4-(4-n-hexoxybenzoyloxy)-benzoic acid, the 4'-n-butylphenyl ester of 4-(4-n-butylbenzoyloxy)-benzoic acid and mixtures thereof.

Claim 26

A modified nematic mixture according to claim 19, wherein X in component (b) is dimethylamino.

Claim 27

A modified nematic mixture according to claim 19, wherein component (a) is selected from the group consisting of 4-n-butyl-4'-methoxy-azoxybenzene, 4-ethyl-4'-methoxy-azoxybenzene and mixtures thereof.

Claim 28

A modified nematic mixture according to claim 24, wherein X in component (b) is dimethylamino.

Claim 29

A modified nematic mixture according to claim 25, wherein component (b) is 4-dimethylaminobenzonitrile.

Claim 30

A modified nematic mixture according to claim 25, wherein component (c) is selected from the group consisting of the 4'-n-butylphenyl ester of 4-anisoyloxybenzoic acid, the 4'-n-butylphenyl ester of 4-(4-n-hexoxybenzoyloxy)benzoic acid, the 4'-n-butylphenyl ester of 4-(4-n-butylbenzoyloxy)benzoic acid and mixtures thereof.

Claim 31

A modified nematic mixture according to claim 24, wherein component (a) is a mixture of said compounds containing a major portion of said 4-n-butyl-4'-methoxyazoxybenzene.

Claim 32

A modified nematic mixture according to claim 28, wherein X in component (b) is dimethylamino.

Claim 33

A modified nematic mixture according to claim 29, wherein component (b) is 4-dimethylaminobenzonitrile.

Claim 34

A modified nematic mixture according to claim 29, wherein component (c) is selected from the group consisting of the 4'-n-butylphenyl ester of 4-anisoyloxybenzoic acid, the 4'-n-butylphenyl ester of 4-(4-n-hexoxybenzoyloxy)benzoic acid, the 4'-n-butylphenyl ester of 4-(4-n-butylbenzoyloxy)benzoic acid and mixtures thereof.

Claim 35

A modified nematic mixture according to claim 30, wherein component (c) is the 4'-n-butylphenyl ester of 4-(4-n-butylbenzoyloxy)-benzoic acid.

Claim 36

A modified nematic mixture according to claim 30, wherein component (c) is a mixture of the 4'-n-butylphenyl ester of 4-(4-n-butylbenzoyloxy)-benzoic acid and the 4'-n-butylphenyl ester of 4-(4-n-hexoxybenzoyloxy)-benzoic acid.