Compositions – Liquid crystal compositions – Containing nonsteryl liquid crystalline compound of...
Patent
1997-11-25
2000-11-07
Kelly, C. H.
Compositions
Liquid crystal compositions
Containing nonsteryl liquid crystalline compound of...
25229962, 25229963, 25229966, 25229967, 544298, 546339, 549369, 570 12, 570144, 568626, C09K 1934, C09K 1932, C09K 1930, C09K 1912
Patent
active
061431982
DESCRIPTION:
BRIEF SUMMARY
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 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 ela
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Matsui Shuichi
Miyazawa Kazutoshi
Nakagawa Etsuo
Sekiguchi Yasuko
Chisso Corporation
Kelly C. H.
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