Twisted nematic liquid crystal display device having a particular pitch-to-thickness ratio

Claim 2

A twisted nematic liquid crystal display device which comprises a liquid crystal cell having a twisted spiral structure by disposing a pair of substrates opposedly to each other with the rubbed orientation films formed on the electrodes, placing a nematic liquid crystal having a positive dielectric anisotrophy containing an optically active substance between this pair of substrates, and shifting the orientation direction of liquid crystal molecules by a specified angle of φ on both substrates, wherein said angle φ is set in a range of 210°≦φ≦300°, the ratio of d/p of the spiral pitch p of said liquid crystal molecules to layer thickness d of said liquid crystal cell is set in a range of (φ/360-1/4)<d/p<φ/360, and the nematic liquid crystal comprises at least one compound of group (I) ##STR63## wherein R 1 to R 7 are straight-chain alkyl groups having 1 to 7 carbon atoms, and R 2 O is a straight-chain alkoxy group having 1 to 7 carbon atoms, with the proviso that the liquid crystal does not include cyanocyclohexane type liquid crystals or cyanocyclohexyl cyclohexane type liquid crystals.

Claim 3

The twisted nematic liquid crystal display device according to claim 1, wherein the compounds of group (I) are selected from the group consisting of ##STR64##

Claim 4

The twisted nematic liquid crystal display device according to claim 1, wherein said device contains a polyimide type high molecular film which is obtained by dehydrating and closing rings of ##STR65## wherein R 1 is ##STR66## R 2 is ##STR67## R 3 is ##STR68## X 1 to X 5 is (CH 2 ) n --, --O--(CH 2 CH 2 O) n --, --O--, --S--, or --SO 2 --; R 4 , R 5 , R 6 , and R 7 represents hydrogen atoms and lower alkyl groups; R 8 and R 9 represents hydrogen atoms, methyl groups, ethyl groups, or trifluoromethyl groups; R 10 is a bivalent hydrocarbon group; and R 11 is a monovalent hydrocarbon group.

Claim 5

The twisted nematic liquid crystal device according to claim 1, wherein the optically active substance is a chiral nematic liquid crystal selected from the group consisting of ##STR69## wherein 2MB* is ##STR70## C* is a symmetric carbon, or a cholesteric liquid crystal having a cholesterol ring as expressed in ##STR71## wherein X is ##STR72##

Claim 6

A twisted nematic liquid crystal display device which comprises a liquid crystal cell having a twisted spiral structure by disposing a pair of substrates opposedly to each other with the rubbed orientation films formed on the electrodes, placing a nematic liquid crystal having a positive dielectric anisotrophy containing an optically active substance between this pair of substrates, and shifting the orientation direction of liquid crystal molecules by a specified angle of φ on both substrates, wherein said angle φ is set in a range of 210°≦φ≦300°, the range of d/p of the spiral pitch p of said liquid crystal molecules to layer thickness d of said liquid crystal cell is set in a range of (φ/360-1/4)<d/p<φ/360, and the nematic liquid crystal comprises a mixture of at least one compound of group (I) and at least one compound of group (II) or group (III), Group (I): ##STR73## wherein R 1 to R 7 are straight-chain alkyl groups having 1 to 7 carbon atoms, and R 2 O is a straight-chain alkoxy group having 1 to 7 carbon atoms, Group (II): ##STR74## wherein R 8 to R 14 are straight-chain alkyl groups having 1 to 7 carbon atoms; R 9 O and R 12 O are straight-chain alkoxy groups having 1 to 7 carbon atoms, and Group (III): ##STR75## wherein R 15 to R 18 are straight-chain alkyl groups having 1 to 7 carbon atoms, and the content of the compound(s) included in group (I) may be 15 wt.% or more of the total.

Claim 7

A twisted nematic liquid crystal display device which comprises a liquid crystal cell having a twisted spiral structure by disposing a pair of substrates opposedly to each other with the rubbed orientation films formed on the electrodes, placing a nematic liquid crystal having a positive dielectric anisotrophy containing an optically active substance between this pair of substrates, and shifting the orientation direction of liquid crystal molecules by a specified angle of φ on both substrates, wherein said angle φ is set in a range of 210°≦φ≦300°, the range of d/p of the spiral pitch p of said liquid crystal molecules to layer thickness d of said liquid crystal cell is set in a range of (φ/360-1/4)<d/p<φ/360, and the nematic liquid crystal comprises a mixture of at least one compound of group (I) and at least one compound of group (II) or group (III), Group (I): ##STR73## wherein R 1 to R 7 are straight-chain alkyl groups having 1 to 7 carbon atoms, and R 2 O is a straight-chain alkoxy group having 1 to 7 carbon atoms, Group (II): ##STR74## wherein R 8 to R 14 are straight-chain alkyl groups having 1 to 7 carbon atoms; R 9 O and R 12 O are straight-chain alkoxy groups having 1 to 7 carbon atoms, and Group (III): ##STR75## wherein R 15 to R 18 are straight-chain alkyl groups having 1 to 7 carbon atoms, and the content of the compound(s) included in group (I) may be 15 wt.% or more of the total.

Claim 8

A twisted nematic liquid crystal display device which comprises a liquid crystal cell having a twisted spiral structure by disposing a pair of substrates opposedly to each other with the rubbed orientation films formed on the electrodes, placing a nemetic liquid crystal having a positive dielectric anisotrophy containing an optically active substance between this pair of substrates, and shifting the orientation direction of liquid crystal molecules by a specified angle of φ on both substrates, wherein said angle φ is set in a range of 210°≦φ≦300°, the ratio of d/p of the spiral pitch p of said liquid crystal molecules to layer thickness d of said liquid crystal cell is set in a range of (φ/360-1/4)<d/p<φ/360, and the orientation films are polyimidesilane type high molecular films obtained from a mixture of 1,3-bis(aminopropyl)tetramethyl disiloxane, 4,4'-diaminodiphenylether and 3,3', 4,4'φbenzophenontetra- carboxylic anhydride.

Claim 9

A twisted nematic liquid crystal display device which comprises a liquid crystal cell having a twisted spiral structure by disposing a pair of substrates opposedly to each other with the rubbed orientation films formed on the electrodes, placing a nemetic liquid crystal having a positive dielectric anisotrophy containing an optically active substance between this pair of substrates, and shifting the orientation direction of liquid crystal molecules by a specified angle of φ on both substrates, wherein said angle φ is set in a range of 210°≦φ≦300°, the ratio of d/p of the spiral pitch p of said liquid crystal molecules to layer thickness d of said liquid crystal cell is set in a range of (φ/360-1/4)<d/p<φ/360, and the orientation films are polyimidesilane type high molecular films obtained from a mixture of 1,3-bis(aminopropyl)tetramethyl disiloxane, 4,4'-diaminodiphenylether and 3,3', 4,4'φbenzophenontetra- carboxylic anhydride.

Claim 10

A twisted nematic liquid crystal display device, which comprises: (i) a first polarizing plate, (ii) a first glass substrate disposed on the first polarizing plate, (iii) a first transparent electrode disposed on the first glass substrate, (iv) a first orientation film disposed on the first transparent electrode, (v) a nematic liquid crystal layer disposed on the first orientation film, (vi) a second orientation film disposed on the liquid crystal layer, (vii) a second transparent electrode disposed on the second orientation film, (viii) a second glass substrate disposed on the second transparent electrode, and (ix) a second polarizing plate disposed on the second glass substrate, wherein said liquid crystal cell has a twisted spiral structure, said nematic liquid crystal has a positive dielectric anisotrophy and contains an optically active substance between said substrates, the orientation direction of liquid crystal molecules being shifted by a specified angle of φ on said substrates, wherein said angle φ is set in a range of 210°≦φ≦300°, the ratio of d/p of the spiral pitch p of said liquid crystal molecules to layer thickness d of said liquid crystal cell is set in a range of (φ/360-1/4)<d/p <φ/360, and the nematic liquid crystal comprises at least one compound of group (I) ##STR76## wherein R 1 to R 7 are straight-chain alkyl groups having 1 to 7 carbon atoms, and R 2 O is a straight-chain alkoxy group having 1 to 7 carbon atoms, with the proviso that the liquid crystal does not include cyanocyclohexane type liquid crystals or cyanocyclohexyl cyclohexane type liquid crystals.

Claim 11

A twisted nematic liquid crystal display device, which comprises: (i) a first polarizing plate, (ii) a first glass substrate disposed on the first polarizing plate, (iii) a first transparent electrode disposed on the first glass substrate, (iv) a first orientation film disposed on the first transparent electrode, (v) a nematic liquid crystal layer disposed on the first orientation film, (vi) a second orientation film disposed on the liquid crystal layer, (vii) a second transparent electrode disposed on the second orientation film, (viii) a second glass substrate disposed on the second transparent electrode, and (ix) a second polarizing plate disposed on the second glass substrate, wherein said liquid crystal cell has a twisted spiral structure, said nematic liquid crystal has a positive dielectric anisotrophy and contains an optically active substance between said substrates, the orientation direction of liquid crystal molecules being shifted by a specified angle of φ on said substrates, wherein said angle φ is set in a range of 210°≦φ≦300°, the ratio of d/p of the spiral pitch p of said liquid crystal molecules to layer thickness d of said liquid crystal cell is set in a range of (φ/360-1/4)<d/p <φ/360, and the nematic liquid crystal comprises at least one compound of group (I) ##STR76## wherein R 1 to R 7 are straight-chain alkyl groups having 1 to 7 carbon atoms, and R 2 O is a straight-chain alkoxy group having 1 to 7 carbon atoms, with the proviso that the liquid crystal does not include cyanocyclohexane type liquid crystals or cyanocyclohexyl cyclohexane type liquid crystals.