Dicyclohexylethylene derivative

Details Dicyclohexylethylene derivative Dicyclohexylethylene derivative

1995-10-26

1997-06-24

Kelly, C. H.

Compositions

Liquid crystal compositions

Containing nonsteryl liquid crystalline compound of...

570128, C09K 1930, C07C 1908

Patent

active

056414323

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to a dicyclohexylethylene derivative. More particularly, it relates to a dicyclohexylethylene derivative which is a compound preferred as a component of display materials, and to a liquid crystal composition containing the derivative.


BACKGROUND ART

In recent years, liquid crystal display elements have been introduced into personal computers and OA apparatus, as display devices, and the importance thereof has been rapidly increasing. For the computers and apparatus, display devices of such a mode as supertwisted nematic (STN) or supertwisted birefringence effect (SBE), and active matrix using a thin film transistor (TFT), among various modes of liquid crystal display have been employed.
The reason is that the quantities of information have been increased by employing these modes, and as a result, color display and magnification of picture of display have become possible. For the liquid crystal materials used for these display modes, various characteristics are required, such that the materials have liquid crystal phases within a temperature region where display elements are used; are stable to environmental factors (moisture, heat, air, light, electricity, etc.); are colorless; are large (or small) in the quantity of the anisotropy of refractive index (herein abbreviated to .DELTA.n); are large in the quantity of the dielectric anisotropy (hereinafter abbreviated to .DELTA..epsilon.); are low in the viscosity; are high in the specific resistivity and yet small in its change with lapse of time; and are broad in d/p margin (d: cell thickness and p: pitch length). However, at present, a single compound which satisfies these requirements and thus is usable for display elements is not available. Thus, practically used liquid crystal materials are ones obtained by mixing several kinds of liquid crystalline compounds or by mixing these compounds with other compounds having specific objects. Accordingly, the liquid crystalline compounds should have a good compatibility with other liquid crystals. Liquid crystalline compounds referred to in this specification mean compounds which, even if they do not apparently exhibit mesophases by themselves, contribute to various characteristics as liquid crystals in a certain aspect when they are mixed with liquid crystal substances.
As a compound similar to that of the present invention, a compound expressed by the following formula (II) has been known: ##STR2## wherein n represents an integer of 3, 4, 5, 6 or 7 (Japanese patent application laid-open No. Sho 61-215336). However, this compound has a high viscosity and an inferior compatibility with a number of already known liquid crystal compounds at low temperatures. Further, this compound has a drawback of being difficultly used from the aspects of specific resistivity required for display materials of TFT mode and its change with lapse of time.
Further, a compound similar to that of the present invention and expressed by the following formula (III) has been disclosed in U.S. Pat. No. 5,055,220: ##STR3## wherein R represents a linear alkyl group of 1 to 8 carbon atoms.
This compound has a broad liquid crystal temperature range and a low viscosity, but it has a weak point of a small dielectric anisotropy.
Still further, fluorine atoms-containing compounds similar to the compound of the present invention, and expressed by the following formulas (IV) and (V) have been disclosed in U.S. Pat. No. 5,032,313 and DE 4,027,840 Al.
Compounds expressed by the formulas (III) and (IV) have a large dielectric anisotropy .DELTA..epsilon. similarly to the compound of the present invention, but they have a drawback of an inferior solubility in other liquid crystal compounds at low temperatures; hence they are somewhat difficultly used. ##STR4##
In these formulas, R represents an alkyl group of 1 to 10 carbon atoms.
The compound expressed by the formula (V) is structurally very similar to the compound of the present invention, and the difference between the compounds exists only in that the compound

REFERENCES:
patent: 4853152 (1989-08-01), Goto et al.
patent: 5032313 (1991-07-01), Goto et al.
patent: 5055220 (1991-10-01), Uchida et al.
patent: 5308541 (1994-05-01), Hittich et al.
patent: 5358662 (1994-10-01), Hirose et al.

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