Mixtures comprising a nematic liquid crystal and a non-mesomorphic compound

Claim 2

A mixture having the properties of a nematic liquid crystal comprising at least one nematic liquid crystal with negative dielectric anisotropy and at least one non-mesomorphic compound able to improve the elastic behaviour of the nematic liquid crystal by increasing the value of the ratio K 33 /K 11 , in which K 33 represents the elastic bending constant and K 11 the elastic fanning constant of the liquid crystal, said non-mesomorphic compound being of formula: ##STR35## in which R 1 and R 2 , which can be the same or different, represent a hydrogen atom or an alkyl radical having 1 to 12 carbon atoms and n is an integer between 2 and 16, said non-mesomorphic compound comprising 0.5 to 10% by weight of the mixture.

Claim 3

A mixture according to claim 1, wherein the non-mesomorphous compound is in accordance with formula: ##STR36##

Claim 4

A mixture according to claim 1, wherein said at least one nematic liquid crystal is a 1-(alkylcyclohexyl)-2-(alkylfluorobiphenylyl)-ethane of formula: ##STR37## in which R 3 and R 4 , which can be the same or different and are alkyl radicals with 1 to 7 carbon atoms.

Claim 5

A mixture according to claim 2, wherein the nematic liquid crystal is 1-(trans-4-n-ethylcyclohexyl)-2-2'-fluoro-4'-(2-ethyl)-4-biphenylyl-ethane of formula: ##STR38##

Claim 6

A mixture according to claim 1, including a mixture of said liquid crystals comprising at least one 1-(alkylcyclohexyl)-2-(alkylfluorobiphenylyl)-ethane of formula: ##STR39## in which R 3 and R 4 , which can be the same or different, are alkyl radicals with 1 to 7 carbon atoms, and at least one compound selected from the group consisting of: (a) the alkyl fluorophenyl alkyl bicyclooctane carboxylates of formula: ##STR40## in which R 5 and R 6 , which can be the same or different, are alkyl radicals with 1 to 7 carbon atoms, (b) biphenylbicyclohexyl dialkyl of formula: ##STR41## in which R 7 and R 8 are alkyl radicals with 1 to 7 carbon atoms, (c) the dicyanoalkoxyphenyl alkylcyclohexyl carboxylates of formula: ##STR42## in which R 9 and R 10 , which can be the same or different, are alkyl radicals with 1 to 7 carbon atoms, and (d) alkyl alkylene or dialkyl bicyclohexylcarbonitrile of formula: ##STR43## in which R 11 and R 12 , which can be the same or different, are alkyl or alkylene radicals with 1 to 7 carbon atoms; said mixture comprising: 60to 90% by weight in all of 1-(alkylcyclohexyl)-2-(alkylfluorobiphenylyl)-ethane, 0 to 15% in all of the alkylfluorophenyl alkyl bicyclooctane carboxylates, 0 to 12% in all of biphenylbicyclohexyl dialkyl, 0 to 12% in all of dicyanoalkoxyphenyl alkyl cyclohexyl carboxylates, and 0 to 40% in all of alkyl alkylene or dialkyl bicyclohexylcarbonitrile.

Claim 7

A liquid crystal display device using the electrically controlled birefringence effect, wherein the screen of said device comprises a mixture according to claim 1.