| CORP. SALE |
NC-C6H10-CH2CH2-[Spiro(3,3)heptane]-CH=CH-CH2-CH= CH2 |
| PATENT ASSIGNEE'S COUNTRY | Japan |
| UPDATE | 12.99 |
| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | 14.12.99 |
| PATENT TITLE |
Liquid-crystalline compound having dienyl moiety and liquid-crystal composition |
| PATENT ABSTRACT |
The present invention is concerned with a liquid crystalline compound expressed by general formula (1) ##STR1## wherein R.sub.1 represents cyano group, halogen atom, or a straight or branched alkyl group or halogenated alkyl group having 1 to 20 carbon atoms, one or not-adjacent two CH.sub.2 groups in the alkyl group or halogenated alkyl group may be replaced by oxygen atom or --CH.dbd.CH-- group; R.sub.2 and R.sub.2 ' represent hydrogen atom, halogen atom, or an alkyl group having 1 to 9 carbon atoms; X.sub.1, X.sub.2, and X.sub.3 independently represent --CH.sub.2 CH.sub.2 --, --CO--O--, --O--CO--, --CH.dbd.CH--, --C.tbd.C--, --(CH.sub.2).sub.4 --, --CF.sub.2 O--, --OCF.sub.2 --, --CH.sub.2 O--, --OCH.sub.2 --, or a covalent bond; rings A, B, C, and D independently represent 1,4-phenylene ring, trans-1,4-cyclohexylene ring, bicyclo[1,1,0]butane ring, bicyclo[1,1,1]pentane ring, bicyclo[3,2,2]octane ring, cyclobutane ring, or spiro[3,3]heptane ring, respectively, hydrogen atom in these rings may be replaced by halogen atom and carbon atom in these rings may be replaced by nitrogen atom or oxygen atom; l, m, and o are independently 0 or 1, n is an integer of 0 to 3, and p is an integer of 1 to 5. |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | 09.07.97 |
| PATENT CT FILE DATE | 19.01.96 |
| PATENT CT NUMBER | This data is not available for free |
| PATENT CT PUB NUMBER | This data is not available for free |
| PATENT CT PUB DATE | 25.07.96 |
| PATENT FOREIGN APPLICATION PRIORITY DATA | This data is not available for free |
| PATENT REFERENCES CITED | This data is not available for free |
| PATENT PARENT CASE TEXT | This data is not available for free |
| PATENT CLAIMS |
We claim: 1. A liquid crystalline compound expressed by the following general formula (1) ##STR1271## wherein R.sub.1 represents cyano group, a halogen atom, or a straight or branched alkyl group or halogenated alkyl group having 1 to 20 carbon atoms, one or not-adjacent two CH.sub.2 groups in the alkyl or halogenated alkyl group may be replaced by oxygen atom or --CH.dbd.CH-- group; R.sub.2 and R.sub.2 ' represent hydrogen atom, a halogen atom, or an alkyl group having 1 to 9 carbon atoms; X.sub.1, X.sub.2 and X.sub.3 independently represent --CH.sub.2 CH.sub.2 --, --CO.tbd.O--, --O--CO--, --CH.dbd.CH--, --(CH.sub.2).sub.4 --, --CF.sub.2 O--, --OCF.sub.2 --, --CH.sub.2 O--, --OCH.sub.2 --, or a covalent bond; rings A, B, C, and D independently represent 1,4-phenylene ring, trans-1,4-cyclohexylene ring, cyclobutane ring, or spiro[3,3]heptane ring, respectively, hydrogen atom in these rings may be replaced by a halogen atom and carbon atom in these rings may be replaced by nitrogen atom or oxygen atom provided that two rings in which carbon atom is replaced by nitrogen atom or oxygen atom are not bonded with a covalent bond, and provided that ring D does not represent trans-1,4-cyclohexylene or trans-1,3-dioxane-2,5-diyl; l and m are independently an integer of 0 or 1, o is 1, n is an integer of 0 to 3; and p is an integer of 1 to 5. 2. The liquid crystalline compound according to claim 1 wherein n is 0, o is 1, p is 2, and R.sub.2 and R.sub.2 ' represent hydrogen atom, respectively. 3. The liquid crystalline compound according to claim 2 wherein at least one of X.sub.1, X.sub.2, and X.sub.3 is a covalent bond. 4. The liquid crystalline compound according to claim 3 wherein X.sub.1, X.sub.2, and X.sub.3 are --CH.sub.2 CH.sub.2 --, --CH.dbd.CH--, --(CH.sub.2).sub.4 --, or a covalent bond. 5. A liquid crystal composition comprising at least two components and containing at least one compound defined in any one of claims 2 to 5 or 1 in at least one of the components. 6. A liquid crystal display device comprising a liquid crystal composition defined in claim 5. 7. A liquid crystal composition comprising, as a first component, at least one liquid crystalline compound expressed by following general formula (1) ##STR1272## wherein R.sub.1 represents cyano group, a halogen atom, or a straight or branched alkyl group or halogenated alkyl group having 1 to 20 carbon atoms, one or not-adjacent two CH.sub.2 groups in the alkyl or halogenated alkyl group may be replaced by oxygen atom or --CH.dbd.CH-- group; R.sub.2 and R.sub.2 ' represent hydrogen atom, a halogen atom, or an alkyl group having 1 to 9 carbon atoms; X.sub.1, X.sub.2 and X.sub.3 independently represent --CH.sub.2 CH.sub.2 --, --CO--O--, --O--CO--, --CH.dbd.CH--, --C.tbd.C--, --(CH.sub.2).sub.4 --, --CF.sub.2 O--, --OCF.sub.2 --, --CH.sub.2 O--, --OCH.sub.2 --, or a covalent bond; rings A, B, C, and D independently represent 1,4-phenylene ring, trans-1,4-cyclohexylene ring, cyclobutane ring, or spiro[3,3]heptane ring, respectively, hydrogen atom in these rings may be replaced by a halogen atom and carbon atom in these rings may be replaced by nitrogen atom or oxygen atom provided that two rings in which carbon atom is replaced by nitrogen atom or oxygen atom are not bonded with a covalent bond, and provided that ring D does not represent trans-1,4-cyclohexylene or trans-1,3-dioxane-2,5-diyl; l and m are independently an integer of 0 or 1, o is 1, n is an integer of 0 to 3; and p is an integer of 1 to 5, and as a second component, one or more compounds selected from the group consisting of the compounds expressed by the general formula (2), (3), or (4) ##STR1273## in which R.sub.3 represents an alkyl group having 1 to 10 carbon atoms, Y represents F or Cl, Q.sub.1 and Q.sub.2 independently represent H or F, r is 1 or 2, and Z.sub.1 and Z.sub.2 independently represent --CH.sub.2 CH.sub.2 -- or a covalent bond. 8. A liquid crystal composition comprising, as a first component, at least one liquid crystalline compound expressed by following general formula (1) ##STR1274## wherein R.sub.1 represents cyano group, a halogen atom, or a straight or branched alkyl group or halogenated alkyl group having 1 to 20 carbon atoms, one or not-adjacent two CH.sub.2 groups in the alkyl or halogenated alkyl group may be replaced by oxygen atom or --CH.dbd.CH-- group; R.sub.2 and R.sub.2 ' represent hydrogen atom, a halogen atom, or an alkyl group having 1 to 9 carbon atoms; X.sub.1, X.sub.2 and X.sub.3 independently represent --CH.sub.2 CH.sub.2 --, --CO--O--, --O--CO--, --CH.dbd.CH--, --C.tbd.C--, --(CH.sub.2).sub.4 --, --CF.sub.2 O--, --OCF.sub.2 --, --CH.sub.2 O--, --OCH.sub.2 --, or a covalent bond; rings A, B, C, and D independently represent 1,4-phenylene ring, trans-1,4-cyclohexylene ring, cyclobutane ring, or spiro[3,3]heptane ring, respectively, hydrogen atom in these rings may be replaced by a halogen atom and carbon atom in these rings may be replaced by nitrogen atom or oxygen atom provided that two rings in which carbon atom is replaced by nitrogen atom or oxygen atom are not bonded with a covalent bond, and provided that ring D does not represent trans-1,4-cyclohexylene or trans-1,3-dioxane-2,5-diyl; l and m are independently an integer of 0 or 1, o is 1, n is an integer of 0 to 3; and p is an integer of 1 to 5, and as a second component, one or more compounds selected from the group consisting of the compounds expressed by the general formula (5), (6), (7), (8), or (9) ##STR1275## in which R.sub.4 represents an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms, in either case any methylene group (--CH.sub.2 --) in the alkyl or alkenyl group may be replaced by oxygen atom (--O--) provided that in no case two or more methylene groups are continuously replaced by oxygen atom; Z.sub.3 represents --CH.sub.2 CH.sub.2 --, --COO--, or a covalent bond; Q.sub.3 and Q.sub.4 represent H or F, E represents cyclohexylene ring, benzene ring, or 1,3-dioxane ring, and s is an integer of 0 or 1, ##STR1276## in which R.sub.5 represents an alkyl group having 1 to 10 carbon atoms, Q.sub.5 represents H or F, and k is an integer of 0 or 1, ##STR1277## in which R.sub.6 represents an alkyl group having 1 to 10 carbon atoms, G represents cyclohexane ring or benzene ring, Q.sub.6 and Q.sub.7 independently represent H or F, Z.sub.4 represents --COO-- or a covalent bond, and h is an integer of 0 or 1, R.sub.7 --(H)--Z.sub.5 --(J)--R.sub.8 ( 8) in which R.sub.7 and R.sub.8 independently represent an alkyl group, alkyloxy group, or alkyloxymethyl group having 1 to 10 carbon atoms, H represents cyclohexane ring, pyrimidine ring, or benzene ring; J represents cyclohexane ring or benzene ring, Z.sub.5 represents --C.tbd.C--, --COO--, --CH.sub.2 CH.sub.2 --, or a covalent bond, ##STR1278## in which R.sub.9 represents an alkyl group or alkoxy group having 1 to 10 carbon atoms, R.sub.10 represents an alkyl group, alkyloxy group, or alkoxymethyl group having 1 to 10 carbon atoms, K represents cyclohexane ring or pyrimidine ring, each of L and M independently represent cyclohexane ring or benzene ring, Z.sub.6 represents --COO--, --CH.sub.2 CH.sub.2 --, or a covalent bond, Z.sub.7 represents --C.tbd.C--,--COO--, or a covalent bond, and Q.sub.8 represents H or F. 9. A liquid crystal display device comprising a liquid crystal composition defined in claim 7. 10. A liquid crystal display device comprising a liquid crystal composition defined in claim 8. 11. The liquid crystalline compound according to claim 1 wherein p is 2 to 5. 12. The liquid crystal composition according to claim 7 wherein p is 2 to 5. 13. The liquid crystal composition according to claim 8 wherein p is 2 to 5 . -------------------------------------------------------------------------------- |
| PATENT DESCRIPTION |
TECHNICAL FIELD The present invention relates to a novel liquid crystalline compound which develops preferable physical properties and to a liquid crystal composition comprising the novel liquid crystalline compound mentioned above and having preferable physical properties. BACKGROUND ART Liquid crystal display devices employ the optical anisotropy and dielectric anisotropy of liquid crystal compounds. As their display mode, twisted nematic mode (TN mode), super twisted nematic mode (STN mode), dynamic scattering mode (DS mode), guest-host mode (GH mode), and DAP mode are known. As their driving mode, static driving mode, time sharing addressing mode, active matrix driving mode, and dual frequency driving mode are known. Whereas the properties of liquid crystalline compounds used for these liquid crystal display devices are different depending on their uses, it is required of any of the liquid crystalline compounds that they are stable against external environmental factors such as moisture, air, heat, and light, and that they exhibit a liquid crystal phase at a range of temperatures as wide as possible with room temperature preferably being at its center. Liquid crystal compositions are composed of several or twenty-odd liquid crystalline compounds to develop most suitable characteristics required of a particular display device. Therefore, liquid crystalline compounds are required to be excellent in miscibility with other liquid crystalline compounds, even in the miscibility at low temperatures particularly from the latest demand for their use in various environment. Especially, steep threshold characteristics are required of liquid crystal compositions used in STN driving to actualize high picture quality. The steepness is a function of the ratio of elastic constants K.sub.33 /K.sub.11, and it is known that the larger the ratio of the elastic constants of liquid crystalline compounds are used in a liquid crystal composition, the steeper threshold characteristics the composition exhibits (F. Leenhouts et al., Proceedings of the Japan Display, 388 (1986) ). Also, it is necessary to use a liquid crystal composition having a high response speed for realizing a large screen of display device. It is known that the response speed is a function of viscosity (E. Jakeman et al., Phys. Lett., 39A, 69 (1972) ). That is, it is important to use liquid crystalline compounds having a low viscosity necessary for actualizing a composition having a low viscosity. As the compound having a large elastic constant ratio K.sub.33 /K.sub.11, compounds which have an alkenyl moiety are known. That is, they are the compounds described in M. Schadt et al., Mol. Cryst. Liq. Cryst., 122 (1985) and Laid-open Japanese Patent Publication No. Sho 61-83136; and the compounds having introduced fluorine atom and described in Japanese Patent Application No. Hei 6-92740, each of which are shown below. ______________________________________ ##STR2## K33/K11 2.28 ##STR3## K33/K11 1.78 ##STR4## K33/K11 2.28 ##STR5## K33/K11 1.90 ______________________________________ Any of these alkenyl compounds has a large ratio of elastic constants K.sub.33 /K.sub.11 (about 1.78 to 2.28) and liquid crystal compositions comprising these compounds exhibit a preferable steepness. (Elastic constant ratio K.sub.33 /K.sub.11 of the four compounds mentioned above are the values determined under the same conditions as in Example 7 (Use Example 1) mentioned below.) However, as the demand on the displaying ability of liquid crystal display devices has increased, liquid crystal compositions having a higher response speed, in other words, liquid crystal compositions having a lower viscosity have been demanded. As the compounds having a large elastic constant ratio K.sub.33 /K.sub.11, compounds having 1,3-butadienyl group are described in Laid Open Japanese Patent Publication No. Hei 6-151445. ##STR6## However, since the substituent, 1,3-butadienyl group has a conjugated diene moiety, the compound is chemically very unstable, and thus it was impossible to use the compound in liquid crystal compositions to be practically used. In short, liquid crystalline compounds are long-awaited which have a large elastic constant ratio K.sub.33 /K.sub.11, still lower viscosity compared with that of known liquid crystalline compounds, high chemical stability, and excellent miscibility with other liquid crystalline compounds. DISCLOSURE OF THE INVENTION An object of the present invention is to provide a novel liquid crystalline compound which has a large ratio of elastic constants, has a low viscosity compared with that of known liquid crystalline compounds, is excellent in miscibility with other liquid crystalline compounds, particularly in the miscibility at low temperatures, and is chemically stable, and to provide a liquid crystal composition containing the compound. As a result of the diligent investigation by the present inventors to solve the problems mentioned above, compounds have been found which have a novel structure and have improved characteristics compared with those of known liquid crystalline compounds, leading to the achievement of the present invention. First aspect of the present invention is concerned with a liquid crystalline compound having an unconjugated alkadienyl group at a side chain. Second aspect of the present invention is concerned with a liquid crystalline compound expressed by general formula (1) ##STR7## wherein R.sub.1 represents cyano group, halogen atom, or a straight or branched alkyl group or halogenated alkyl group having 1 to 20 carbon atoms, one or not-adjacent two CH.sub.2 groups in the alkyl group or halogenated alkyl group may be replaced by oxygen atom or --CH.dbd.CH-- group; R.sub.2 and R.sub.2 ' represent hydrogen atom, halogen atom, or an alkyl group having 1 to 9 carbon atoms; X.sub.1, X.sub.2, and X.sub.3 independently represent --CH.sub.2 CH.sub.2 --, --CO--O--, --O--CO--, --CH.dbd.CH--, --C.tbd.C--, --(CH.sub.2).sub.4 --, --CF.sub.2 O--, --OCF.sub.2 --, --CH.sub.2 O--, --OCH.sub.2 --, or a covalent bond; rings A, B, C, and D are independently represent 1,4-phenylene ring, trans-1,4-cyclohexylene ring, bicyclo[1,1,0] butane ring, bicyclo[1,1,1]pentane ring, bicyclo[3,2,2]octane ring, cyclobutane ring, or spiro[3,3]heptane ring, respectively, hydrogen atom in these rings may be replaced by halogen atom, carbon atom in these rings may be replaced by nitrogen atom or oxygen atom; l, m, and o are independently 0 or 1, n is an integer of 0 to 3, p is an integer of 1 to 5. Third aspect of the present invention is concerned with a second compound of the present invention expressed by general formula (1) wherein n is 0, o is 1, p is 2, and R.sub.2 and R.sub.2 ' are hydrogen atom, respectively. Fourth aspect of the present invention is concerned with a third compound of the present invention expressed by general formula (1) wherein at least one of X.sub.1, X.sub.2, and X.sub.3 is a covalent bond. Fifth aspect of the present invention is concerned with a fourth compound of the present invention expressed by general formula (1) wherein X.sub.1, X.sub.2, and X.sub.3 are --CH.sub.2 CH.sub.2 --, --CH.dbd.CH--, --(CH.sub.2).sub.4 --, or a covalent bond. Sixth aspect of the present invention is concerned with a liquid crystal composition comprising at least two components and containing a compound recited in any one of the aspects 1 to 5 in at least one of the components. Seventh aspect of the present invention is concerned with a liquid crystal composition containing, as a first component, at least one compound recited in any one of the aspects 1 to 5, and containing, as a second component, one or more compounds selected from the group consisting of the compounds expressed by general formula (2), (3), or (4) ##STR8## in which R.sub.3 represents an alkyl group having 1 to 10 carbon atoms, Y represents F or Cl, Q.sub.1 and Q.sub.2 independently represent H or F, r is 1 or 2, and Z.sub.1 and Z.sub.2 independently represent --CH.sub.2 CH.sub.2 -- or a covalent bond. Eighth aspect of the present invention is concerned with a liquid crystal composition containing, as a first component, at least one compound recited in any one of the aspects 1 to 5, and containing, as a second component, one or more compounds selected from the group consisting of the compounds expressed by general formula (5), (6), (7), (8), or (9) ##STR9## in which R.sub.4 represents an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms, in either case any methylene group (--CH.sub.2 --) in the alkyl or alkenyl group may be replaced by oxygen atom (--O--) provided that in no case two or more methylene groups are continuously replaced by oxygen atom; Z.sub.3 represents --CH.sub.2 CH.sub.2 --, --COO--, or a covalent bond, Q.sub.3 and Q.sub.4 represent H or F, E represents cyclohexane ring, benzene ring, or 1,3-dioxane ring, and s is an integer of 0 or 1, ##STR10## in which R.sub.5 represents an alkyl group having 1 to 10 carbon atoms, Q.sub.5 represents H or F, and k is an integer of 0 or 1, ##STR11## in which R.sub.6 represents an alkyl group having 1 to 10 carbon atoms, G represents cyclohexane ring or benzene ring, Q.sub.6 and Q.sub.7 independently represent H or F, respectively, Z.sub.4 represents --COO-- or a covalent bond, and h is an integer of 0 or 1, R.sub.7 --(H)--Z.sub.5 --(J)--R.sub.8 (8) in which R.sub.7 and R.sub.8 independently represent an alkyl group, alkyloxyl group, or alkyloxymethyl group having 1 to 10 carbon atoms, H represents cyclohexane ring, pyrimidine ring, or benzene ring, J represents cyclohexane ring or benzene ring, Z.sub.5 represents --C.tbd.C--, --COO--, --CH.sub.2 CH.sub.2 --, or a covalent bond, ##STR12## in which R.sub.9 represents an alkyl group or alkoxyl group having 1 to 10 carbon atoms, R.sub.10 represents an alkyl group, alkyloxyl group, or alkoxymethyl group having 1 to 10 carbon atoms, K represents cyclohexane ring or pyrimidine ring, each of L and M independently represent cyclohexane ring or benzene ring, Z.sub.6 represents --COO--, --CH.sub.2 CH.sub.2 --, or a covalent bond, Z.sub.7 represents --C.tbd.C--, --COO--, or a covalent bond, and Q.sub.8 represents H or F. Ninth aspect of the present invention is concerned with a liquid crystal display device comprising a liquid crystal composition recited in any one of the aspects 6 to 8. Tenth aspect of the present invention is concerned with a liquid crystal display device comprising a liquid crystal composition recited in any one of the aspects 6 to 9. Preferable compounds of the present invention recited in the aspects 1 to 5 are those expressed by the group of the following general formulas (1-a) to (1-c). However, W in the following formulas represents --(CH.sub.2).sub.n --(CH).sub.o .dbd.CH--(CH.sub.2)p--CH.dbd.CH--R.sub.2 R.sub.2 ' in general formula (1), and R.sub.1, R.sub.2, R.sub.2 ', X.sub.1, X.sub.2, X.sub.3, rings A, B, C, and D, and l, m, n, o, and p have the same meaning as mentioned above. ##STR13## Further, among the compounds expressed by the group of general formulas (1-a) to (1-c), particularly preferable compounds are shown below: ##STR14## whereas R.sub.1 and W in the formulas shown above have the same meaning as that mentioned above, hydrogen atom in 1,4-phenylene ring, trans-1,4-cyclohexylene ring, bicyclo[1,1,0]butane ring, bicyclo[1,1,1] pentane ring, bicyclo[3,2,2]octane ring, cyclobutane ring, and spiro[3,3]heptane ring may be replaced by halogen atom, and the carbon atom in the rings may be replaced by nitrogen atom or oxygen atom. While any of dienyl group W exhibits preferable characteristics when it satisfies the conditions shown by general formula (1), particularly preferable ones are W.sub.1 to W.sub.15, W.sub.17, and W.sub.19, and more desirable ones are W.sub.1 to W.sub.8, and W.sub.17 shown below: ##STR15## While R.sub.1 in the formulas shown above represents cyano group, halogen atom, or a straight or branched alkyl group or halogenated alkyl group having 1 to 20 carbon atoms, methylene group in the alkyl or halogenated alkyl group may be replaced by oxygen atom or --CH.dbd.CH--. As the halogen atom, fluorine atom and chlorine atom, and as the alkyl group, one having 1 to 10 carbon atoms, particularly 1 to 6 carbon atoms is preferable. Further, as the halogenated alkyl group, trifluoromethyl, trifluoromethoxy, difluoromethoxy, 2-fluoroethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, 3-fluoropropyl, 2-fluoro-propyl, 2,2-difluoropropyl, 4-fluorobutyl, 3-fluorobutyl, 2-fluorobutyl, 3,3-difluorobutyl, 2,2-difluorobutyl, 5-fluoropentyl, 4-fluoropentyl, 3-fluoropentyl, 3,3-difluoropentyl, and 10-fluorodecyl are preferable. As the one in which methylene group is replaced by oxygen atom, methoxymethyl, ethoxymethyl, propoxymethyl, butoxymethyl, pentoxymethyl, methoxyethoxy, methoxypropyl, ethoxyethoxy, and ethoxypropoxyl group are preferable. As the one in which methylene group is replaced by --CH.dbd.CH--, vinyl, 1-propenyl, 2-propenyl, 1-butenyl, 3-butenyl, 1-pentenyl, 2-pentenyl, and 3-pentenyl group are preferable. Any of the compounds of the present invention expressed by general formula (1) has a large elastic constant ratio K.sub.33 /K.sub.11 and a low viscosity. Further, any of them is an unconjugated diene and chemically very stable. Any of the compounds of the present invention exhibits preferable physical properties, and liquid crystal compositions which have characteristics satisfying the purpose can be produced by using compounds expressed by general formula (1) and in which R.sub.1, R.sub.2, R.sub.2 ', X.sub.1, X.sub.2, X.sub.3, A, B, C, D, l, m, n, o, and p are suitably selected. For instance, when a compound is used for a liquid crystal composition mesomorphic range of which must be particularly in a high temperature side, a tricyclic or tetracyclic compound can be used, and in other cases, bicyclic or tricyclic compound can be used. When especially a large dielectric anisotropy is required, a compound having a positive dielectric anisotropy (P type compound) is used as in the case for compositions commonly used, and a P type compound can be provided by selecting halogen atom or cyano group as R.sub.1 in general formula (1). Besides, when a still larger dielectric anisotropy is required, the purpose is achieved by introducing halogen atom on a ring to which R.sub.1 is linked. In order to obtain a compound having a negative dielectric anisotropy (N type compound), it will be sufficient to introduce a substituent having a not-large dipole moment, for example, an alkyl group as R.sub.1. Optical anisotropy can also be controlled by optionally selecting R.sub.1, R.sub.2, R.sub.2 ', X.sub.1, X.sub.2, X.sub.3, A, B, C, D, l, m, n, o, and p in general formula (1). That is, when a large optical anisotropy is required, it is sufficient to use a compound having more 1,4-phenylene rings; and a compound having a more trans-1,4-cyclohexylene rings when a small optical anisotropy is required. Compounds of the present invention expressed by general formula (1) can readily be produced by freely using the ordinary technique in organic synthetic chemistry as indicated by the reaction formulas shown below: ##STR16## in the formula shown above, ring D represents a substituted or unsubstituted 1,4-phenylene ring or trans-1,4-cyclohexylene ring, hydrogen atom in the ring may be replaced by halogen atom, and the carbon atom in the ring may be replaced by nitrogen atom or oxygen atom, and X represents halogen atom. That is, when o and n are 0, the compound expressed by general formula (1) can be produced by reacting a phosphonium salt such as (11) with a cyclohexanone (10) in the presence of a base. The phosphonium salt can readily be produced from a corresponding halide and triphenylphosphine according to the method of G. Wittig et al. described in Org. Synth. Col. V. 751 (1973). As the base, for example, alkyl lithium, sodium hydride, and potassium-t-butoxide can preferably be used. When o is 1, (1) can be obtained by reacting (11) with an aldehyde expressed by (12) according to the method of G. Wittig et al. described in Org. Synth. Col. V. 751 (1973). Whereas the reaction of (11) with (12) usually gives a cis form olefin as main product, it can be derived to (1) which is in trans form by converting the olefin into a bromide (13), removing unnecessary isomers by recrystallization, and then reducing the bromide according to the method of J. Schaeffer et al. described in Org. Synth. Col. V. 249 (1973). While the method in which the olefin is once oxidized to form an epoxide and then reacted with triphenylphosphine dibromide is preferable for the bromination, there is no problem in directly reacting bromine of simple substance with an olefin. While the reduction of (13) can readily be performed by either method, the use of metal zinc according to the method of S. J. Cristol et al. described in J. Am. Chem. Soc., 89, 401 (1967) is preferable. Cyclohexanone (10) can readily be produced from, for example, a halide (14). That is, (10) can be preferably produced by converting (14) into Grignard reagent or lithium reagent, reacting it with an available cyclohexanone derivative (15), and then subjecting to a dehydration, reduction, and deprotection. Also, aldehyde (12) can be produced from a carboxylic acid (16), which can be obtained by a method described in literatures, for example, the method of M. E. Neubert et al. described in Mol. Cryst. Liq. Cryst., 76, 48 (1981), by utilizing a two carbons homologation reaction ordinarily used. When X.sub.1, X.sub.2, and X.sub.3 in general formula (1) are --CH.sub.2 CH.sub.2 --, main skeleton can be constructed according to the method of Laid-open Japanese Patent Publication No. Hei 5-140015 and when they are --(CH.sub.2).sub.4 --, can be constructed according to the method of Laid-open Japanese Patent Publication No. Hei 5-310605. When they are --CH.dbd.CH-- or --C.tbd.C--, it can be produced by the method of Laid-open Japanese Patent Publication No. Hei 6-92924 and C. E. Castro et al. described in Org. Chem., 28, 2163, 3313 (1963), respectively. When they are --CF.sub.2 O-- or --OCF.sub.2 --, it can be produced according to the method of Laid-open Japanese Patent Publication No. Hei 5-112778, and when they are --CH.sub.2 O-- or --OCH.sub.2 --, it can be produced according to the method of Japanese Patent Publication No. Hei 2-6743. Also, when they are --COO-- or --OCO--, it can preferably be produced according to the method of B. K. Sadashiva, Mol. Cryst. Liq. Cryst., 55, 135 (1979). Liquid crystal composition of the present invention preferably contains at least one compound expressed by general formula (1) in a ratio of 0.1 to 99% by weight to develop excellent characteristics. Specifically, liquid crystal compositions of the present invention can be produced by blending a compound optionally selected, depending on the purpose, from the group of compounds expressed by any one of general formulas (2) to (9) to the first component containing at least one compound expressed by general. formula (1). As the compounds used in liquid crystal compositions of the present invention and expressed by any one of general formulas (2) to (4), the following compounds can preferably be mentioned: (In the followings, Ra represents an alkyl group or alkoxy group.) ##STR17## Compounds expressed by any one of general formulas (2) to (4) are ones which have a positive dielectric anisotropy, are remarkably excellent in heat resistance and chemical resistance, and are indispensable compounds when liquid crystal compositions for TFT (AM-LCD) are produced of which TFT high reliability demonstrated, for instance, by an especially high voltage holding ratio and a large specific resistance is required. While the compounds expressed by any one of general formulas (2) to (4) can optionally be used in the range of 1 to 99% by weight based on the total amount of liquid crystal composition when liquid crystal compositions for TFT are produced, the use in an amount of 10 to 97% by weight is preferable and 40 to 95% by weight is more desirable. Also at that time, a compound expressed by any one of general formulas (5) to (9) may be contained as a part of the composition. Even when liquid crystal compositions for STN display mode or ordinary TN display mode are produced, a compound expressed by any one of general formulas (2) to (4) can be used. As the compounds expressed by any one of general formulas (5) to (7), the following compounds can preferably mentioned: (In the followings, Rb, Rc, and Rd represent an alkyl group or alkenyl group, and R' represents an alkylene.) ##STR18## Compounds expressed by any one of general formulas (5) to (7) have a large positive dielectric anisotropy and are used particularly for the purpose of lowering threshold voltage. They are also used for the purpose of adjusting viscosity and optical anisotropy, and of widening nematic range by, for instance, raising clearing point. Further, they are used for the purpose of improving the steepness. As the compounds of the present invention expressed by general formula (8) or (9), the following compounds can preferably be mentioned: (In the followings, Re, Rf, Rg, and Rh represent an alkyl group or alkenyl group.) ##STR19## Compounds expressed by general formula (8) or (9) are ones having a negative or small positive dielectric anisotropy. Compounds expressed by general formula (8) are used for the purpose of principally reducing viscosity and/or adjusting optical anisotropy. Compounds expressed by general formula (9) are used for the purpose of widening nematic range by, for instance, raising clearing point and/or adjusting optical anisotropy. Compounds expressed by any one of general formulas (5) to (9) are indispensable particularly when liquid crystal compositions for STN display mode or ordinary TN display mode are produced. While the compounds of general formulas (5) to (9) can optionally be used in the range of 1 to 99% by weight when liquid crystal compositions for ordinary TIN display mode or STN display mode are produced, the use in an amount of 10 to 97% by weight is preferable, and 40 to 95% by weight is more desirable. Also at that time, a compound expressed by any one of general formulas (2) to (4) may be used as a part of the composition. By using the liquid crystal compositions of the present invention for TFT liquid crystal display devices, steepness and viewing angle can be improved. Also, since the compounds expressed by general formula (1) have a low viscosity, the response speed of the liquid crystal display devices comprising the compounds can be improved. Liquid crystal compositions used according to the present invention are produced by the methods which are conventional in the art. Generally, methods are adopted in which various components are dissolved with each other at a high temperature. Also, liquid crystal materials of the present invention are improved, depending on the intended uses, by using a suitable additive to optimize. Such additives are well known in the art and described in literatures in detail. Usually, a chiral dopant or likes are added to cause a helical structure of liquid crystal to adjust a required twisting angle, and to avoid reverse-twist. Further, the liquid crystal compositions of the present invention can be used as liquid crystal compositions for guest-host (GH) mode by adding a dichroic dye such as merocyanine type, styryl type, azo type, azomethine type, azoxy type, quinophthalone type, anthraquinone type, and tetrazine type dye. Alternatively, they can also be used as liquid crystal compositions for polymer dispersion type liquid crystal display devices (PDLCD) typified by NCAP which is prepared by forming a nematic liquid crystal into a microcapsule or typified by a polymer net work liquid crystal display devices (PNLCD) which is prepared by forming a polymer of three-dimensional network structure in a liquid crystal. Also, the liquid crystal compositions of the present invention can be used as ones for electrically controlled birefringence (ECB) mode or dynamic scattering (DS) mode. As the nematic liquid crystal compositions containing the compounds of the present invention and produced by the methods mentioned above, composition examples can be shown as follows: |
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