Compositions – Liquid crystal compositions – Containing nonsteryl liquid crystalline compound of...
Patent
1995-10-18
1999-03-02
Wu, Shean C.
Compositions
Liquid crystal compositions
Containing nonsteryl liquid crystalline compound of...
25229901, 25229961, 25229966, 25229967, 544298, 544334, 546290, 546339, 546345, 548136, 548146, 549 29, 549369, C09K 1930, C09K 1934, C07D23902, C07D21172
Patent
active
058766286
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a novel compound for use in liquid-crystal compositions.
DESCRIPTION OF THE RELATED ART
In particular in the last decade, liquid crystals have been introduced into various technical areas where electro-optical and display device properties are required (for example, in watch, calculator and typewriter displays). These display devices are based on the dielectric alignment effects in the nematic, cholesteric and/or smectic phases of the liquid-crystalline compounds, where, caused by the dielectric anisotropy, the molecular long axes of the compounds adopt a preferred alignment in an applied electric field. The conventional response times in these display devices are too long for many other potential areas of application of liquid crystals. This disadvantage is particularly noticeable if a large number of pixels have to be addressed. The production costs of equipment containing relatively large screen areas are then generally too high.
In addition to nematic and cholesteric liquid crystals, optically active smectic liquid-crystal phases have also been increasing in importance for a few years.
Clark and Lagerwall have been able to show that the use of ferroelectric liquid-crystal systems in very thin cells give electro-optical switch or display elements which have response times faster by a factor of up to 1000 compared with conventional TN ("twisted nematic") cells (cf., for example, Lagerwall et al., "Ferroelectric Liquid Crystals for Displays", SID Symposium, October Meeting 1985, San Diego, Calif., USA). Due to these and other favorable properties, for example, the possibility for bistable switching and the contrast which is virtually independent of the viewing angle, FLCs are fundamentally very suitable for the above-mentioned areas of application, for example, via matrix addressing. Due to their high contrast and speed, ferroelectric liquid crystals are also particularly suitable in the area of spatial light modulators (cf, for example, U. Efron in "Spatial Light Modulators and Applications", SPIE, Vol. 1150, p. 46 ff).
Ferroelectric properties are expressed in liquid crystals having a phase called a smectic phase represented by a smectic C phase. Compounds having a smectic phase are described in, for example, G. W. Gray et al., Mol. Cryst. Liq. Cryst., Vol. 37, 157-188 (1976). The working temperature and the storage temperature of such liquid-crystal display devices are restricted by the temperatures range of a smectic C phase. Hence ferroelectric liquid crystals having a smectic C phase in a temperature range of -20.degree. C. to +70.degree. C. are desired.
The above requirements can only be satisfied by mixing a plurality of components. In addition, a material which can reduce the melting point and raise the upper limit of the phase transition temperature of a smectic C phase is always required. Compounds bearing a very short alkyl or alkyloxy radical on only one side of the molecule tend to have a nematic phase. It has been an established technique in the art to use such compounds as a component of nematic liquid crystal compositions (Japanese Patent Public Disclosure No. 148282/1986 and No. 003451/1980). However, they have not been considered to be useful for ferroelectric liquid-crystal compositions.
SUMMARY OF THE INVENTION
Accordingly, the object of the present invention is to provide a compound capable of broadening the temperature range of a smectic C phase and to provide a liquid-crystal composition containing the compounds.
Surprisingly, it has now been found that compounds which include as a terminal group a cyclohexyl group having no side chains have a smectic C phase and are useful for broadening the temperature range of the smectic C phase and reducing the melting point of smectic liquid-crystal compositions and ferroelectric liquid crystals.
The present invention relates to compounds of the formula (I): ##STR2## in which the symbols and indices have the following meanings: R.sup.1 is a straight-chain or branched alkyl ra
REFERENCES:
patent: 5384071 (1995-01-01), Gray et al.
patent: 5445763 (1995-08-01), Schlosser et al.
patent: 5460749 (1995-10-01), Terada et al.
patent: 5468421 (1995-11-01), Matsui et al.
patent: 5679792 (1997-10-01), Escher et al.
Fujiwara Hidenori
Illian Gerhard
Muller Ingrid
Nagao Kazuya
Nonaka Thoshiaki
Hoechst Aktiengesellschaft
Wu Shean C.
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