| CORP. SALE | Et-C(=CH2)-(CH2)n-C6H4-C6H4-Me; n = 0-10 |
| PATENT ASSIGNEE'S COUNTRY | Japan |
| UPDATE | 11.00 |
| PATENT NUMBER | This data is not available for free |
| PATENT GRANT DATE | 07.11.00 |
| PATENT TITLE |
Liquid crystalline compounds having exo-methylene site and liquid crystal compositions comprising the same |
| PATENT ABSTRACT |
A liquid crystalline compound represented by the general formula (1) ##STR1## wherein R.sub.1 represents an alkyl or alkoxy group having 1 to 10 carbon atoms, a cyano group, a halogen atom, or an alkyl or alkoxy halide group having 1 to 4 carbon atoms; R.sub.2 represents an alkyl group having 1 to 10 carbon atoms; rings A.sub.1, A.sub.2, A.sub.3, and A.sub.4 each independently represent a 1,4-phenylene or 1,4-cyclohexylene group; Z.sub.1, Z.sub.2, and Z.sub.3 each independently represent a covalint bond, --CH.sub.2 CH.sub.2 --, --CH.dbd.CH--, --C.tbd.C-- or --COO--; 1 and m are 0 pr 1; and n is 0 to 10. |
| PATENT INVENTORS | This data is not available for free |
| PATENT ASSIGNEE | This data is not available for free |
| PATENT FILE DATE | 25.11.97 |
| PATENT CT FILE DATE | 24.05.96 |
| 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 | 28.11.96 |
| PATENT FOREIGN APPLICATION PRIORITY DATA | This data is not available for free |
| PATENT REFERENCES CITED | Schadt et al., "Polar Alkenyls: Physical Properties and Correlations with Molecular Structure of New Nematic Liquid Crystals", Mol. Cryst. Liq. Cryst., 1985, vol. 122, pp. 241-260. |
| PATENT PARENT CASE TEXT | This data is not available for free |
| PATENT CLAIMS |
What is claimed is: 1. A liquid crystalline compound represented by the general formula ( 1): ##STR45## wherein R.sub.1 represents an alkyl or alkoxy group having 1 to 10 carbon atoms, a cyano group, a halogen atom, or an alkyl or alkoxy halide group having 1 to 4 carbon atoms; R.sub.2 represents an alkyl group having 2 to 10 carbon atoms; rings A.sub.1, A.sub.2, A.sub.3, and A.sub.4 each independently represent a 1,4-phenylene, 1,4-cyclohexylene, 1,4-cyclohexenylene, 1,3-dioxane-2,5-diyl, Dyrimidine-2,5-diyl, pyridine-2,5-diyl, or bicyclo[1,1,1]pentanediyl group, provided that the rings may be substituted with one or more halogen atoms; Z.sub.1, Z.sub.2, and Z.sub.3 each independently represent a covalent bond, --CH.sub.2 CH.sub.2 --, --CH.dbd.CH--, --C.tbd.C--, --COO--, --OCO--, --CH.sub.2 O--, --OCH.sub.2 -- or --(CH.sub.2).sub.4 --; l and m are 0 or 1; and n is 0 to 10; provided that R.sub.2 is an alkyl group having 2 to 10 carbon atoms when R.sub.1 is a halogen atom, a halogenated alkyl group or a halogenated alkoxy group, the ring to which R.sub.1 is directly connected is a 1,4-phenylene group which may be substituted by a halogen atom, and ring A.sub.4 is a 1,4-cyclohexylene group. 2. A liquid crystal display device comprising a liquid crystal composition, the liquid crystal composition comprising at least one liquid crystalline compound according to claim 1. 3. A liquid crystal composition comprising more than one compound, at least one of which is a liquid crystalline compound according to claim 1. 4. A liquid crystal display device comprising a liquid crystal composition according to claim 3. 5. A liquid crystalline compound represented by the general formula (1-1): ##STR46## wherein R.sub.1 represents an alkyl or alkoxy group having 1 to 10 carbon atoms, a cyano group, a halogen atom, or an alkyl or alkoxy halide group having 1 to 4 carbon atoms; R.sub.2 represents an alkyl group having 2 to 10 carbon atoms; rings A.sub.3 and A.sub.4 each independently represent a 1,4-phenylene or 1,4-cyclohexylene, provided that the rings may be substituted with one or more halogen atoms; Z.sub.3 represents a covalent bond, --CH.sub.2 CH.sub.2 --, --CH.dbd.CH--, --C.tbd.C--, --COO--, --OCO--, --CH.sub.2 O--, --OCH.sub.2 -- or --(CH.sub.2).sub.4 --; and n is 0 to 10; provided that R.sub.2 is an alkyl group having 2 to 10 carbon atoms when R.sub.1 is a halogen atom, a halogenated alkyl group or a halogenated alkoxy group, ring A.sub.3 is a 1,4-phenylene group which may be substituted by a halogen atom, and ring A.sub.4 is a 1,4-cyclohexylene group. 6. The liquid crystalline compound according to claim 5, wherein Z.sub.3 represents a covalent bond, --CH.sub.2 CH.sub.2 --, --CH.dbd.CH-- or --C.tbd.C--. 7. The liquid crystalline compound according to claim 5, wherein R.sub.1 represents an alkyl group having 1 to 10 carbon atoms, rings A.sub.3 and A.sub.4 represent a 1,4-cyclohexylene group, Z.sub.3 represents a covalent bond, --CH.sub.2 CH.sub.2 -- or --CH.dbd.CH-- and n is 0 to 10. 8. A liquid crystalline compound represented by the general formula (1-2): ##STR47## wherein R.sub.1 represents an alkyl or alkoxy group having 1 to 10 carbon atoms, a cyano group, a halogen atom, or an alkyl or alkoxy halide group having 1 to 4 carbon atoms; R.sub.2 represents an alkyl group having 1 to 10 carbon atoms; rings A.sub.2, A.sub.3 and A.sub.4 each independently represent a 1,4-phenylene or 1,4-cyclohexylene, provided that the rings may be substituted with one or more halogen atoms; Z.sub.2 and Z.sub.3 each independently represent a covalent bond, --CH.sub.2 CH--, --CH.dbd.CH--, --C.tbd.C--, --COO--, --OCO--, --CH.sub.2 O--, --OCH.sub.2 -- or --(CH.sub.2).sub.4 --; and n is 0 to 10; provided that R.sub.2 is an alkyl group having 2 to 10 carbon atoms when R.sub.1 is a halogen atom, a halogenated alkyl group or a halogenated alkoxy group, ring A.sub.2 is a 1,4-phenylene group which may be substituted by a halogen atom, and ring A.sub.4 is a 1,4-cyclohexylene group. 9. The liquid crystalline compound according to claim 8, wherein Z.sub.2 and Z.sub.3 each independently represent a covalent bond, --CH.sub.2 CH.sub.2 --, --CH.dbd.CH--, --C.tbd.C-- or --(CH.sub.2).sub.4 --. 10. The liquid crystalline compound according to claim 9, wherein R.sub.1 represents a cyano group, a halogen atom, or an alkyl halide or alkoxy halide group having 1 to 4 carbon atoms and ring A.sub.2 represents a 1,4-phenylene group, provided that the ring may be substituted with one or more halogen atoms. 11. The liquid crystalline compound according to claim 9, wherein R.sub.1 represents an alkyl group having 1 to 10 carbon atoms, and ring A.sub.2 represents a 1,4-cyclohexylene group, provided that the ring may be substituted with one or more halogen atoms. 12. The liquid crystalline compound according to claim 8, which is represented by the general formula (1-3): ##STR48## wherein R.sub.1 represents a cyano group, a halogen atom, or an alkyl or alkoxy group having 1 to 4 carbon atoms; W.sub.1 and W.sub.2 represent a fluorine or chlorine atom; Z.sub.2 and Z.sub.3 each independently represent --CH.sub.2 CH.sub.2 -- or --(CH.sub.2).sub.4 --; and n is 0 to 10; provided that R.sub.2 is an alkyl group having 2 to 10 carbon atoms when R.sub.1 is a halogen atom, a halogenated alkyl group or a halogenated alkoxy group, and ring A.sub.4 is a 1,4-cyclohexylene group. 13. The liquid crystalline compound according to claim 12, wherein R.sub.1 represents a cyano group, a fluorine or chlorine atom, a trifluoromethyl, trifluoromethoxy, difluoromethoxy, 1,1,2,2-tetrafluoroethoxy, 1,1,2,3,3,3-hexafluoropropoxy, 2,2-difluoroethoxy, or 2,2,2-trifluoroethoxy group and Z.sub.2 and Z.sub.3 each independently represent a covalent bond, --CH.sub.2 CH.sub.2 -- or --(CH.sub.2).sub.4 --. 14. A liquid crystal composition comprising: a first component of at least one compound according to any one of claims 1, 5-12 and 13; and a second component of at least one member selected from the group consisting of compounds represented by the general formulae (2), (3), and (4): ##STR49## wherein R.sub.3 represents an alkyl group having 1 to 10 carbon atoms, Y represents a fluorine or chlorine atom, Q.sub.1 and Q.sub.2 each independently represent a hydrogen or fluorine atom, r is 1 or 2, and Z.sub.4 and Z.sub.5 each independently represent --CH.sub.2 CH.sub.2 -- or a covalent bond. 15. A liquid crystal composition comprising: a first component of at least one compound according to any one of claims 1, 5-12 and 13; and a second component of at least one member selected from the group consisting of compounds represented by the general formulae (5), (6), (7), (8), and (9): ##STR50## wherein R.sub.4 represents an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms, provided that although any methylene group (--CH.sub.2 --) may be replaced by an oxygen atom (--O--), two or more consecutive methylene groups are not simultaneously replaced by an oxygen atom, Z.sub.6 represents --CH.sub.2 CH.sub.2 --, --COO-- or a covalent bond, Q.sub.3 and Q.sub.4 represent a hydrogen or fluorine atom, E represents a cyclohexane, benzene, or 1,3-dioxane ring, and s is 0 or 1; ##STR51## wherein R.sub.5 represents an alkyl group having 1 to 10 carbon atoms, Q.sub.5 represents a hydrogen or fluorine atom, and k is 0 or 1; ##STR52## wherein R.sub.6 represents an alkyl group having 1 to 10 carbon atoms, G represents a cyclohexane or benzene ring, Q.sub.6 and Q.sub.7 each independently represent a hydrogen or fluorine atom, Z.sub.7 represents --COO-- or a covalent bond, and h is 0 or 1; ##STR53## wherein R.sub.7 and R.sub.8 each independently represent an alkyl, alkyloxy or alkyloxymethyl group having 1 to 10 carbon atoms, H represents a cyclohexane, pyrimidine or benzene ring, J represents a cyclohexane or benzene ring, and Z.sub.8 represents --C.tbd.C--, --COO--, --CH.sub.2 CH.sub.2 -- or a covalent bond; and ##STR54## wherein R.sub.9 represents an alkyl or alkoxyl group having 1 to 10 carbon atoms, R.sub.10 represents an alkyl, alkyloxy or alkoxymethyl group having 1 to 10 carbon atoms, K represents a cyclohexane or pyrimidine ring, L and M each independently represent a cyclohexane or benzene ring, Z.sub.9 represents --COO--, --CH.sub.2 CH.sub.2 -- or a covalent bond, Z.sub.10 represents --C.tbd.C--, --COO--, or a covalent bond, and Q.sub.8 represents hydrogen or florine atom. 16. A liquid crystal display device comprising a liquid crystal composition according to claim 14. 17. A liquid crystal display device comprising a liquid crystal composition according to claim 15. |
| PATENT DESCRIPTION |
TECHNICAL FIELD The present invention relates to novel liquid crystalline compounds, which can develop various properties suitable for use as electro-optical display materials, and liquid crystal compositions, having various favorable properties, using the novel liquid crystalline compounds. BACKGROUND ART Liquid crystal display devices are used in watches and clocks, electric calculators, various types of measuring equipment, panels for automobiles, word processors, electronic message pads, printers, computers, televisions, etc. The liquid crystal displays take advantage of optical anisotropy and anisotropy of dielectric constant which liquid crystalline compounds possess. Known display systems for this purpose include twisted nematic (TN), super-twisted nematic (STN), dynamic scattering (DS), guest-host (G-H), DAP, ferroelectric liquid crystal (FLC) display systems. Drive systems, for these display systems, known in the art include static drive, time-sharing drive, active-matrix drive, and double-channel drive systems. Various properties are required of the liquid crystal materials depending upon display systems and drive systems. However, 1) a wide temperature range of liquid crystal phase and 2) low viscosity are important properties required in common to all the systems. Properties necessary for meeting the requirement 1) include a high upper limit temperature of the nematic phase and a melting point low enough to prevent phase separation such as crystallization in a low temperature region. The properties of liquid crystalline compounds used in these various liquid crystal display devices vary depending upon applications of the liquid crystal display devices. However, good stability against external environment factors, such as moisture, air, heat, and light, are required of the all the liquid crystalline compounds used for these purposes. Further, these liquid crystalline compounds are required to exhibit a liquid crystal phase in an as wide as possible temperature range around room temperature. A liquid crystal composition for use in liquid crystal display devices comprises several to twenty-odd liquid crystalline compounds in order to develop optimal properties required of individual display devices. For this purpose, good compatibility with other liquid crystalline compounds, particularly good compatibility with other liquid crystalline compounds at a low temperature due to an ever-increasing demand for use of the display device under various environments, is required of the liquid crystalline compounds. Liquid crystal compositions for use in the STN drive system are required to have steep threshold properties from the viewpoint of realizing a high image quality. The steepness is a function of the elastic constant ratio K33/K11, and it is known that the steepness of the threshold properties increases with increasing the elastic constant ratio of liquid crystalline compounds used in the liquid crystal composition (F. Leenhouts et al., Proceedings of the Japan Display, 388 (1986)). The following compounds having an alkenyl site are known to have a large elastic constant ratio K33/K11: the following compounds (a) described in M. Schadt et al., Mol. Cryst. Liq. Cryst., 122 (1985) and Japanese Patent Laid-Open No. 83136/1986: ##STR2## and the following compounds (b), containing a fluorine atoms, described in Japanese Patent Application No. 92740/1994: ##STR3## When the above alkenyl compounds were mixed in an amount of 15% by weight with a liquid crystal composition comprising 24% of 4-(4-propylcyclohexyl)benzonitrile, 36% of 4-(4-pentylcyclohexyl)benzonitrile, 25% of 4-(4-heptylcyclohexyl)benzonitrile, and 15% of 4-(4-pentylphenyl)benzonitrile, and properties were measured, it was found that all the above compounds had a relatively large elastic constant ratio K33/K11 and all the liquid crystal compositions using these compounds had favorable steepness. The upper limit of the elastic constant ratio K33/K11 of a liquid crystalline compound having an alkenyl site on its side chain is that noted above. However, an ever-increasing demand for an improvement in display ability of liquid crystal display devices has led to a demand for compounds having more steep threshold properties. In other words, liquid crystalline compounds having a larger elastic constant ratio K33/K11 have been desired in the art. That is, the provision of a novel skeleton other than alkenyl compounds has been desired in the art. Compounds (c) having a 1,3-butadienyl group, represented by the following structural formula, described in Japanese Patent Laid-Open No. 286873/1993 are also known to have a high elastic constant ratio K33/K11: ##STR4## These compounds, however, do not have a satisfactorily high elastic constant ratio K33/K11 and, since the 1,3-butadienyl group has a conjugated diene site, chemically very unstable, making it impossible to use them in liquid crystal compositions for practical purpose. That is, the development of liquid crystalline compounds, for STN, possessing a very large elastic constant ratio K33/K11, high chemical stability, and good compatibility with other liquid crystalline compounds has been desired in the art. Liquid crystal compositions designed for active-matrix liquid crystal displays with an integrated non-linear element incorporated thereinto for switching individual pixels, particularly, for TFT, should have large positive anisotropy of dielectric constant and, in addition, very high specific resistance (high voltage retention), good UV stability, and high compatibility with other liquid crystalline compounds at a low temperature. The active-matrix liquid crystal displays are suitable particularly for displays for televisions, advanced information displays for computers, and advanced information displays in automobiles and airplanes. However, when liquid crystalline compounds or liquid crystalline compositions not having very high specific resistance (high voltage retention) or good UV stability are used, the contrast decreases with a lowering in electrical resistance in the liquid crystal panel, posing a problem of "afterimage quenching." High electrical resistance of the liquid crystal composition is a very important factor which determines the service life, particularly in the case of low-voltage drive. For this reason, very high specific resistance (high voltage retention) and good UV stability are very important properties required of liquid crystalline compounds used. Further, in order to enable use of the liquid crystal composition in a wide temperature range, the liquid crystal composition should have a nematic phase particularly at a low temperature. Therefore, liquid crystal compositions free from the precipitation of a crystal or the development of a smectic phase and having a minimized temperature dependence of viscosity at a low temperature have been desired in the art. For this, that the liquid crystalline compound used has high compatibility with other liquid crystalline compounds at a low temperature is very important. However, no conventional liquid crystalline compounds, for TFT, which have a combination of large positive anisotropy of dielectric constant, very high specific resistance (high voltage retention), good UV stability, high compatibility with other liquid crystalline compounds at a low temperature, are known in the art. An object of the present invention is to provide a novel liquid crystalline compound having a large elastic constant ratio, excellent compatibility with other liquid crystalline compound(s) particularly at a low temperature, and chemical stability, or a liquid crystalline compound having a combination of a large positive anisotropy of dielectric constant, a very high specific resistance (a high voltage retention), good UV stability, and high compatibility with other liquid crystalline compound(s) at a low temperature, and a liquid crystal composition comprising the same. DISCLOSURE OF INVENTION The present inventors have extensive and intensive studies with a view to solving the above problems and, as a result, have found compounds having a novel structure and possessing better properties than the conventional liquid crystalline compounds. Specifically, the present inventors have found compounds, with an exo-methylene site on their side chain, possessing better properties than the conventional liquid crystalline compounds, which has led to the completion of the present invention. Thus, the first invention relates to a liquid crystalline compound represented by the general formula (1): ##STR5## wherein R.sub.1 represents an alkyl or alkoxy group having 1 to 10 carbon atoms, a cyano group, a halogen atom, or an alkyl or alkoxy halide group having 1 to 4 carbon atoms; R.sub.2 represents an alkyl group having 1 to 10 carbon atoms; rings A.sub.1, A.sub.2, A.sub.3, and A.sub.4 each independently represent a 1,4-phenylene, 1,4-cyclohexylene, 1,4-cyclohexenylene, 1,3-dioxane-2,5-diyl, pyrimidine-2,5-diyl, pyridine-2,5-diyl, or bicyclo[1,1,1]pentanediyl group, provided that the rings may be substituted with one or more halogen atoms; Z.sub.1, Z.sub.2, and Z.sub.3 each independently represent a covalent bond, --CH.sub.2 CH.sub.2 --, --CH.dbd.CH--, --C.tbd.C--, --COO--, --OCO--, --CH.sub.2 O--, --OCH.sub.2 -- or --(CH.sub.2).sub.4 --; 1 and m are 0 or 1; and n is 0 to 10. The second invention relates to a liquid crystalline compound represented by the general formula (1--1): ##STR6## wherein R.sub.1 represents an alkyl or alkoxy group having 1 to 10 carbon atoms, a cyano group, a halogen atom, or an alkyl or alkoxy halide group having 1 to 4 carbon atoms; R.sub.2 represents an alkyl group having 1 to 10 carbon atoms; rings A.sub.3 and A.sub.4 each independently represent a 1,4-phenylene or 1,4-cyclohexylene, provided that the rings may be substituted with one or more halogen atoms; Z.sub.3 represents a covalent bond, --CH.sub.2 CH.sub.2 --, --CH.dbd.CH--, --C.tbd.C--, --COO--, --OCO--, --CH.sub.2 O--, --OCH.sub.2 --, or --(CH.sub.2).sub.4 --; and n is 0 to 10. The third invention relates to a liquid crystalline compound according to the second invention, wherein Z.sub.3 represents a covalent bond, --CH.sub.2 CH.sub.2 --, --CH.dbd.CH-- or --C.tbd.C--. The fourth invention relates to a liquid crystalline compound according to the second invention, wherein R.sub.1 represents an alkyl group having 1 to 10 carbon atoms, rings A.sub.3 and A.sub.4 represent a 1,4-cyclohexylene group, Z.sub.3 represents a covalent bond, --CH.sub.2 CH.sub.2 -- or --CH.dbd.CH--and n is 0 to 10. The fifth invention relates to a liquid crystalline compound represented by the general formula (1-2): ##STR7## wherein R.sub.1 represents an alkyl or alkoxy group having 1 to 10 carbon atoms, a cyano group, a halogen atom, or an alkyl or alkoxy halide group having 1 to 4 carbon atoms; R.sub.2 represents an alkyl group having 1 to 10 carbon atoms; rings A.sub.2, A.sub.3 and A.sub.4 each independently represent a 1,4-phenylene or 1,4-cyclohexylene group, provided that the rings may be substituted with one or more halogen atoms; Z.sub.2 and Z.sub.3 each independently represent a covalent bond, --CH.sub.2 CH.sub.2 --, --CH.dbd.CH--, --C.tbd.C--, --COO--, --OCO--, --CH.sub.2 O--, --OCH.sub.2 -- or --(CH.sub.2).sub.4 --; and n is 0 to 10. The sixth invention relates to a liquid crystalline compound according to the fifth invention, wherein Z.sub.2 and Z.sub.3 each independently represent a covalent bond, --CH.sub.2 CH.sub.2 --, --CH.dbd.CH--, --C.tbd.C-- or --(CH.sub.2).sub.4 --. The seventh invention relates to a liquid crystalline compound according to the sixth invention, wherein R.sub.1 represents a cyano group, a halogen atom, or an alkyl halide or alkoxy halide group having 1 to 4 carbon atoms and-ring A.sub.2 represents a 1,4-phenylene group, provided that the ring may be substituted with one or more halogen atoms. The eighth invention relates to a liquid crystalline compound according to the sixth invention, wherein R.sub.1 represents an alkyl group having 1 to 10 carbon atoms, ring A.sub.2 represents a 1,4-cyclohexylene group, provided that the ring may be substituted with one or more halogen atoms. The ninth invention relates to a liquid crystalline compound according to the fifth invention, which is represented by the general formula (1-3): ##STR8## wherein R.sub.1 represents a cyano group, a halogen atom, or an alkyl or alkoxy group having 1 to 4 carbon atoms; W.sub.1 and W.sub.2 represent a fluorine or chlorine atom; Z.sub.2 and Z.sub.3 each independently represent a covalent bond, --CH.sub.2 CH.sub.2 -- or --(CH.sub.2).sub.4 --; and n is 0 to 10. The tenth invention relates to a liquid crystalline compound according to the ninth invention, wherein R.sub.1 represents a cyano group, a fluorine or chlorine atom, a trifluoromethyl, trifluoromethoxy, difluoromethoxy, 1,1,2,2-tetrafluoroethoxy, 1,1,2,3,3,3-hexafluoropropoxy, 2,2-difluoroethoxy, or 2,2,2-trifluoroethoxy group and Z.sub.2 and Z.sub.3 each independently represent a covalent bond, --CH.sub.2 CH.sub.2 -- or --(CH.sub.2).sub.4 --. The eleventh invention relates to a liquid crystal composition comprising at least one of which is a liquid crystalline compound represented by the general formula (1). The twelfth invention relates to a liquid crystal composition comprising: a first component of at least one compound according to any one of the first to tenth inventions; and a second component of at least one member selected from the group consisting of compounds represented by the general formulae (2), (3), and (4): ##STR9## wherein R.sub.3 represents an alkyl group having 1 to 10 carbon atoms, Y represents a fluorine or chlorine atom, Q.sub.1 and Q.sub.2 each independently represent a hydrogen or fluorine atom, r is 1 or 2, Z.sub.4 and Z.sub.5 each independently represent --CH.sub.2 CH.sub.2 -- or a covalent bond. The thirteenth invention relates to a liquid crystal composition comprising: a first component of at least one compound according to any one of the first to tenth inventions; and a second component of at least one member selected from the group consisting of compounds represented by the general formulae (5), (6), (7), (8), and (9): ##STR10## wherein R.sub.4 represents an alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms, provided that although any methylene group (--CH.sub.2 --) may be replaced by an oxygen atom (--O--), two or more consecutive methylene groups are not simultaneously replaced by an oxygen atom, Z.sub.6 represents --CH.sub.2 CH.sub.2 --, --COO-- or a covalent bond, Q.sub.3 and Q.sub.4 represent a hydrogen or fluorine atom H or F, E represents a cyclohexane, benzene, or 1,3-dioxane ring, and s is 0 or 1; ##STR11## wherein R.sub.5 represents an alkyl group having 1 to 10 carbon atoms, Q.sub.5 represents a hydrogen or fluorine atom, and k is 0 or 1; ##STR12## wherein R.sub.6 represents an alkyl group having 1 to 10 carbon atoms, G represents a cyclohexane or benzene ring, Q.sub.6 and Q.sub.7 each independently represent a hydrogen or fluorine atom, Z.sub.7 represents --COO-- or a covalent bond, and h is 0 or 1; ##STR13## wherein R.sub.7 and R.sub.8 each independently represent an alkyl, alkyloxy, or alkyloxymethyl group having 1 to 10 carbon atoms, H represents a cyclohexane, pyrimidine or benzene ring, J represents a cyclohexane or benzene ring, and Z.sub.8 represents --C.tbd.C--, --COO--, --CH.sub.2 CH.sub.2 -- or a covalent bond; and ##STR14## wherein R.sub.9 represents an alkyl or alkoxyl group having 1 to 10 carbon atoms, R.sub.10 represents an alkyl, alkyloxy, or alkoxymethyl group having 1 to 10 carbon atoms, K represents a cyclohexane or pyrimidine ring, L and M each independently represent a cyclohexane or benzene ring, Z.sub.9 represents --COO--, --CH.sub.2 CH.sub.2 -- or a covalent bond, Z.sub.10 represents --C.tbd.C--, --COO-- or a covalent bond, and Q.sub.8 represents a hydrogen or fluorine atom. The fourteenth invention relates to a liquid crystal display device comprising a liquid crystal composition, the liquid crystal composition comprising at least one of which is a liquid crystalline compound represented by the general formula (1). The fifteenth invention relates to a liquid crystal display device comprising a liquid crystal composition according to any one of the eleventh to fourteenth inventions. The compounds, of the present invention, represented by the formula (1) features a large elastic constant ratio K33/K11, high specific resistance, high voltage retention, chemical stability, good UV stability, low viscosity, and good compatibility with other liquid crystalline compounds at a low temperature. Further, liquid crystal compositions using the compounds represented by the formula (1) have good steepness of threshold voltage and, hence, can be used to realize display devices which have high definition display quality and long service life and can be driven at a low temperature. The compounds of the formula (1) according to the present invention have a particularly large elastic constant ratio K33/K11. In the prior art, compounds having a large elastic constant ratio have been limited to compounds having an alkenyl site on their side chain. No compounds having a skeleton other than that of the conventional compounds and, at the same time, possessing the above properties are utterly known in the art. Like the compounds of the formula (1) according to the present invention, compounds with an exo-methylene site incorporated on their side chain can develop a much larger elastic constant ratio than the conventional alkenyl derivatives. Best Mode for Carrying Out the Invention All the compounds of the present invention have favorable properties. The use of compounds represented by the formula (1) wherein R.sub.1, R.sub.2, rings A.sub.1, A.sub.2, A.sub.3, A.sub.4, Z.sub.1, Z.sub.2, and Z.sub.3, l, m, and n have been properly selected enables the preparation of liquid crystal compositions having properties suitable for respective applications. Specifically, in particular, a compound of three-ring system or a four-ring system may be used for the preparation of a composition which should have a liquid crystal temperature range on a high temperature side, while a compound of two-ring system or a three-ring system may be used for the preparation of a composition which is not required to have such a property. When particularly large anisotropy of dielectric constant is necessary, a compound having positive anisotropy of dielectric constant (P type compound) is used as in the case of a conventional composition. In this case, a P type compound can be provided by selecting a halogen atom, a cyano group, or an alkyl halide group as R.sub.1 in the formula (1). When larger anisotropy of dielectric constant is necessary, this can be achieved by introducing a halogen atom on a ring so as for dipoles to orient toward an identical direction. When a compound having negative anisotropy of dielectric constant (N type compound) is desired, a group, of which the dipole moment is not large, for example, an alkyl or alkoxy group, may be introduced into R.sub.1. The anisotropy of refractive index also can be regulated, as desired, by selecting R.sub.1, R.sub.2, rings A.sub.1, A.sub.2, A.sub.3, A.sub.4, Z.sub.1, Z.sub.2, and Z.sub.3, l, m, and n in the formula (1). Specifically, when large anisotropy of refractive index is necessary, a compound having a high 1,4-phenylene ring content may be used, while when small anisotropy of refractive index is necessary, a compound having a high trans-1,4-cyclohexylene content may be used. The term "alkyl group" used includes straight-chain or branched alkyl groups having 1 to 10 carbon atoms. Among them, an alkyl group having 3 to 5 carbon atoms is particularly preferred from the viewpoint of low viscosity. Examples of preferred alkyl groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, isopropyl, isobutyl, isoamyl, isohexyl, 2-methylbutyl, 2-methylpentyl, and 3-methylpentyl groups, and the term "alkyl group" embraces racemic, S, and R forms. The term "alkoxy group" used herein include straight-chain or branched alkoxy groups having 1 to 10 carbon atoms. Among them, an alkoxy group having 3 to 5 carbon atoms is preferred. Examples of preferred alkyl groups include methoxy, ethoxy, propoxy, butoxy, pentoxy, hexyloxy, heptyloxy, octyloxy, isopropoxy, isobutoxy, isoamyloxy, isohexyloxy, 2-methylbutoxy, 2-methylpentoxy, and 3-methylpentoxy groups, and the term "alkoxy group" embraces racemic, S, and R forms. The term "alkyl halide group" used herein refers to an alkyl group, having 1 to 4 carbon atoms, with at least one fluorine atom and/or at least one chlorine atom bonded to a carbon atom(s). Among them, an alkyl groups subsutituted with fluorine atom(5) is preferred. Examples of preferred alkyl fluolide groups include monofluoromethyl, difluoromethyl, trifluoromethyl, 2-fluoroethyl, 2,2-difluoroethyl, 2,2,2-trifluoroethyl, 1,1,2,2-tetrafluoroethyl, perfluoroethyl, 3-fluoropropyl, 3,3-difluoropropyl, 3,3,3-trifluoropropyl, 2,2,3,3,3-pentafluoropropyl, 1,1,2,3,3,3-hexafluoropropyl, perfluoropropyl, 4-fluorobutyl, perfluorobutyl, and 5-fluoropentyl groups. The term "alkoxy halide group" used herein refers to an alkoxy group, having 1 to 4 carbon atoms, with at least one fluorine atom and/or at least one chlorine atom bonded to a carbon atom(s). Examples of preferred alkoxy halide groups include monofluoromethoxy, difluoromethoxy, trifluoromethoxy, 2,2-difluoroethoxy, 2,2,2-trifluoroethoxy, 1,1,2,2-tetrafluoroethoxy, perfluoroethoxy, 3,3-difluoropropoxy, 3,3,3-trifluoropropoxy, 2,2,3,3,3-pentafluoropropoxy, 1,1,2,3,3,3-hexafluoropropoxy, perfluoropropoxy, and perfluorobutoxy groups. Among the compounds of the formula (1) according to the present invention, a group of compounds represented by a group of general formulae (1-4) to (1-40) are preferred. R.sub.1, R.sub.2, rings A.sub.1, A.sub.2, A.sub.3, and A.sub.4, and n are as defined above. ##STR15## Among the compounds of the formula (1) according to the present invention, a group of compounds represented by a group of general formulae (1-41) to (1-136) are more preferred. R.sub.1, R.sub.2, and n are as defined above. W.sub.3, W.sub.4, W.sub.5, W.sub.6, W.sub.7, W.sub.8, W.sub.9, and W.sub.10 represent a fluorine or a chlorine atom. ##STR16## All the compounds having a side chain including an exo-methylene site "--(CH.sub.2).sub.n --C(.dbd.CH.sub.2)--R.sub.2 " have good properties so far as requirements specified in the general formula (1) are met. R.sub.2 represents an alkyl group having 1 to 10 carbon atoms or a straight-chain or branched hydrocarbon residue. Preferred examples of the side chain "--(CH.sub.2).sub.n --C(.dbd.CH.sub.2)--R.sub.2 " include: 1-methyl-1-ethenyl(isopropenyl), 1-ethyl-1-ethenyl, 1-propyl-1-ethenyl, 1-isopropyl-1-ethenyl, 1-butyl-1-ethenyl, 1-isobutyl-1-ethenyl, 1-pentyl-1-ethenyl, 1-isopentyl-1-ethenyl, 1-(2-methylbutyl)-1-ethenyl, 1-hexyl-1-ethenyl, 1-isohexyl-1-ethenyl, 1-(2-methylpentyl)-1-ethenyl, 1-(3-methylpentyl)-1-ethenyl, 1-heptyl-1-ethenyl, 1-octyl-1-ethenyl, 1-nonyl-1-ethenyl, 1-decyl-1-ethenyl, 2-methyl-2-propenyl, 2-ethyl-2-propenyl, 2-propyl-2-propenyl, 2-isopropyl-2-propenyl, 2-butyl-2-propenyl, 2-isobutyl-2-propenyl, 2-pentyl-2-propenyl, 2-isopentyl-2-propenyl, 2-(2-methylbutyl)-2-propenyl, 2-hexyl-2-propenyl, 2-isohexyl-2-propenyl, 2-(2-methylpentyl)-2-propenyl-2-(3-methylpentyl)-2-propenyl, 2-heptyl-2-propenyl, 2-octyl-2-propenyl, 2-nonyl-2-propenyl, 2-decyl-2-propenyl, 3-methyl-3-butenyl, 3-ethyl-3-butenyl, 3-propyl-3-butenyl, 3-isopropyl-3-butenyl, 3-butyl-3-butenyl, 3-isobutyl-3-butenyl, 3-pentyl-3-butenyl, 3-isopentyl-3-butenyl, 3-(2-methylbutyl)-3-butenyl, 3-hexyl-3-butenyl, 3-isohexyl-3-butenyl, 3-(2-methylpentyl)-3-butenyl, 3-(3-methylpentyl)-3-butenyl, 3-heptyl-3-butenyl, 3-octyl-3-butenyl, 3-nonyl-3-butenyl, 3-decyl-3-butenyl, 4-methyl-4-pentenyl, 4-ethyl-4-pentenyl, 4-propyl-4-pentenyl, 4-isopropyl-4-pentenyl, 4-butyl-4-pentenyl, 4-isobutyl-4-pentenyl, 4-pentyl-4-pentenyl, 4-isopentyl-4-pentenyl, 4-(2-methylbutyl)-4-pentenyl, 4-hexyl-4-pentenyl, 4-isohexyl-4-pentenyl, 4-(2-methylpentyl)-4-pentenyl, 4-(3-methylpentyl)-4-pentenyl, 4-heptyl-4-pentenyl, 4-octyl-4-pentenyl, 4-nonyl-4-pentenyl, 1-decyl-4-pentenyl, 5-methyl-5-hexenyl, 5-ethyl-5-hexenyl, 5-propyl-5-hexenyl, 5-isopropyl-5-hexenyl, 5-butyl-5-hexenyl, 5-isobutyl-5-hexenyl, 5-pentyl-5-hexenyl, 5-isopentyl-5-hexenyl, 5-(2-methylbutyl)-5-hexenyl, 5-hexyl-5-hexenyl, 5-isohexyl-5-hexenyl, 5-(2-methylpentyl)-5-hexenyl, 5-(3-methylpentyl)-5-hexenyl, 5-heptyl-5-hexenyl, 5-octyl-5-hexenyl, 5-nonyl-5-hexenyl, 5-decyl-5-hexenyl, 6-methyl-6-heptenyl, 6-ethyl-6-heptenyl, 6-propyl-6-heptenyl, 6-isopropyl-6-heptenyl, 6-butyl-6-heptenyl, 6-isobutyl-6-heptenyl, 6-pentyl-6-heptenyl, 6-isopentyl-6-heptenyl, 6-(2-methylbutyl)-6-heptenyl, 6-hexyl-6-heptenyl, 6-isohexyl-6-heptenyl, 6-(2-methylpentyl)-6-heptenyl, 6-(3-methylpentyl)-6-heptenyl, 6-heptyl-6-heptenyl, 6-octyl-6-heptenyl, 6-nonyl-6-heptenyl, 6-decyl-6-heptenyl, 7-methyl-7-octenyl, 7-ethyl-7-octenyl, 7-propyl-7-octenyl, 7-isopropyl-7-octenyl, 7-butyl-7-octenyl, 7-isobutyl-7-octenyl, 7-pentyl-7-octenyl, 7-isopentyl-7-octenyl, 7-(2-methylbutyl)-7-octenyl, 7-hexyl-7-octenyl, 7-isohexyl-7-octenyl, 7-(2-methylpentyl)-7-octenyl, 7-(3-methylpentyl)-7-octenyl, 7-heptyl-7-octenyl, 7-octyl-7-octenyl, 7-nonyl-7-octenyl, 7-decyl-7-octenyl, 8-methyl-8-nonenyl, 8-ethyl-8-nonenyl, 8-propyl-8-nonenyl, 8-isopropyl-8-nonenyl, 8-butyl-8-nonenyl, 8-isobutyl-8-nonenyl, 8-pentyl-8-nonenyl, 8-isopentyl-8-nonenyl, 8-(2-methylbutyl)-8-nonenyl, 8-hexyl-8-nonenyl, 8-isohexyl-8-nonenyl, 8-(2-methylpentyl)-8-nonenyl, 8-(3-methylpentyl)-8-nonenyl, 8-heptyl-8-nonenyl, 8-octyl-8-nonenyl, 8-nonyl-8-nonenyl, and 8-decyl-8-nonenyl groups. Among them, the following groups are more preferred: 3-methyl-3-butenyl, 3-ethyl-3-butenyl, 3-propyl-3-butenyl, 3-butyl-3-butenyl, 3-pentyl-3-butenyl, 3-hexyl-3-butenyl, 3-heptyl-3-butenyl, 3-octyl-3-butenyl, 3-nonyl-3-butenyl, 3-decyl-3-butenyl, 4-methyl-4-pentenyl, 4-ethyl-4-pentenyl, 4-propyl-4-pentenyl, 4-butyl-4-pentenyl, 4-pentyl-4-pentenyl, 4-hexyl-4-pentenyl, 4-heptyl-4-pentenyl, 4-octyl-4-pentenyl, 4-nonyl-4-pentenyl, 4-decyl-4-pentenyl, 5-methyl-5-hexenyl, 5-ethyl-5-hexenyl, 5-butyl-5-hexenyl, 5-pentyl-5-hexenyl, 5-hexyl-5-hexenyl, 5-heptyl-5-hexenyl, 5-octyl-5-hexenyl, 5-nonyl-5-hexenyl, and 5-decyl-5-hexenyl groups. Among the above groups, the following groups are more preferred from the viewpoints of low viscosity and high clearing point: 3-methyl-3-butenyl, 3-ethyl-3-butenyl, 3-propyl-3-butenyl, 3-butyl-3-butenyl, 3-pentyl-3-butenyl, 4-methyl-4-pentenyl, 4-ethyl-4-pentenyl, 4-propyl-4-pentenyl, 4-butyl-4-pentenyl, 5-methyl-5-hexenyl, 5-ethyl-5-hexenyl, and 5-butyl-5-hexenyl groups. Preferably, the liquid crystal composition of the present invention comprises 0.1 to 99.9% by weight in total of at least one member selected from the compounds represented by the formula (1) from the viewpoint of developing good properties. More preferably, the liquid crystal composition according to the present invention comprises a first component containing at least one member selected from the compounds of the formula (1) and, in addition, at least one member properly selected from a group of compounds represented by the general formulae (2) to (9) according the applications of the liquid crystal composition. Preferred examples of compounds, used in the present invention, represented by the general formulae (2) to (4) include the following compounds. (In the following formulae, R.sub.a represents an alkyl or alkoxy group.) ##STR17## The compounds represented by the general formulae (2) to (4) have positive anisotropy of dielectric constant and possess excellent thermal stability and chemical stability and, hence, are indispensable to the preparation of liquid crystal compositions particularly for TFT (AM-LCD) where high voltage retention or high specific resistance are required. The amount of the compounds represented by the general formulae (2) to (4), when used in the preparation of a liquid crystal composition for TFT, may be in the range of from 1 to 99% by weight based on the total weight of the liquid crystal composition. It is preferably in the range of from 10 to 97% by weight, more preferably in the range of from 40 to 95% by weight. In this case, the compounds represented by the general formulae (5) to (9) may constitute a part of the liquid crystal composition. The compounds represented by the general formulae (2) to (4) may be used also in the preparation of liquid crystal compositions for STN display system or conventional TN display systems. Examples of preferred compounds represented by the general formulae (5) to (7) according to the present invention include the following compounds. (In the following formulae, R.sub.b, R.sub.c, and R.sub.d represent an alkyl or alkenyl group and R' represents .alpha.,.omega.-alkylene.) ##STR18## The compounds represented by the general formulae (5) to (7) have large positive anisotropy of dielectric constant and are used particularly for decreasing the threshold voltage. Further, they are used also for widening the nematic range, for example, for the purposes of modifying the viscosity, regulating the anisotropy of refractive index, and increasing the clearing point. It is also possible to use them for improving the steepness of the threshold voltage. Examples of preferred compounds represented by the general formulae (8) to (9) according to the present invention include the following compounds. (In the following formulae, R.sub.e, R.sub.f, R.sub.g, and R.sub.h represent an alkyl or alkenyl group.) ##STR19## The compounds represented by the following formulae (8) and (9) have negative or somewhat positive anisotropy of dielectric constant. The compounds represented by the general formula (8) are mainly used for lowering the viscosity and/or regulating the anisotropy of refractive index. On the other hand, the compounds represented by the general formula (9) are used for widening the nematic range, for example, for the purposes of increasing the clearing point, and/or for regulating the anisotropy of refractive index. The compounds represented by the general formulae (5) to (9) are indispensable particularly to the preparation of liquid crystal compositions for STN display system and conventional TN display-system. The amount of the compounds represented by the general formulae (5) to (9), when used in the preparation of a liquid crystal composition for conventional TN and STN display systems, may be in the range of from 1 to 99% by weight. It is preferably in the range of from 10 to 97% by weight, more preferably in the range of from 40 to 95% by weight. In this case, the compounds represented by the general formulae (2) to (4) may constitute a part of the liquid crystal composition. The use of the liquid crystal composition according to the present invention for TFT liquid crystal display devices enables an improvement in steepness and angle of visibility. Further, the compounds represented by the formula (1) have a low viscosity and, hence, when used in liquid crystal display devices, can markedly improve the response speed. The liquid crystal composition used according to the present invention may be prepared by a production process which is per se commonly used in the art. In general, different components are dissolved in each other at a high temperature. Alternatively, it is also possible to use a method wherein the components are dissolved in an organic solvent capable of dissolving liquid crystals used and the solvent is then distilled off. Further, the liquid crystal material of the present invention may be modified by using suitable additives according to the contemplated applications. Such additives are well known in the art and described in detail in literature or the like. In general, additives such as, chiral dopants, are added in order to induce the helical structure of the liquid crystal to adjust the twist angle as desired, thereby preventing reverse twisting. Furthermore, when the liquid crystal composition used according to the present invention is contemplated to be used as a liquid crystal composition for guest-host (GH) mode, dichroic dyes, such as merocyanine, styryl, azo, azomethine, azoxy, quinophthalone, anthraquinone, and tetrazine dyes, may be added to the liquid crystal composition. Furthermore, the liquid crystal composition according to the present invention can also be used as a liquid crystal composition for NCAP, which has been prepared by enmicrocapsulating a nematic liquid crystal, or a polymer dispersion type liquid crystal display device (PDLCD) represented by a polymer network liquid crystal display device (PNLCD) with a three-dimensional network polymer prepared in a liquid crystal. Furthermore, it may be used also as a liquid crystal composition for the birefringence control (ECB) mode or dynamic scattering (DS) mode. Composition examples of nematic liquid crystal compositions, containing the compound of the present invention, thus prepared will be given below. Compound No. given in parentheses corresponds to that described in "Examples" which will be given below. |
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