Compositions – Liquid crystal compositions
Patent
1992-10-08
1994-07-05
Wu, Shean
Compositions
Liquid crystal compositions
25229961, 25229963, 25229966, 25229967, 560 8, 560 55, C09K 1952, C09K 1934, C09K 1930, C09K 1912
Patent
active
053264959
DESCRIPTION:
BRIEF SUMMARY
The invention relates to novel tetrasubstituted methanes of the general formula is an alkylene or alkenylene radical having 1 to 12 carbon atoms which is unsubstituted or monosubstituted by halogen, --CN or --CF.sub.3 and in which, in addition, one or two non-adjacent CH.sub.2 groups may be replaced by --O--, --CO--, --COO--, --OOC--, --CONH-- or --OCOO--, or is a single bond, M is a mesogenic group and R is hydrogen, halogen, --CN, --CF.sub.3, --OCF.sub.3, --NO.sub.2, --N(CH.sub.3).sub.2, a straight-chain or branched alkyl or alkenyl radical having 1 to 12 carbon atoms which is unsubstituted or monosubstituted or polysubstituted by --CN, --NH.sub.2, --CF.sub.3 or halogen and in which one or more non-adjacent CH.sub.2 groups may be replaced by the radicals --O--, --CO--, --OOC--, --COO-- or --OCOO--.
BACKGROUND OF THE INVENTION
The novel methane derivatives of the general formulae I and II (see below) according to the invention are thermotropic liquid-crystalline compounds; due to their molecular structure principle, which is novel for such compounds, they generally broaden the known range of liquid-crystalline substances by means of which mixtures having favorable applicational properties can be prepared.
By contrast, the molecules of mesogenic compounds which have hitherto achieved technical importance in display technology and as temperature displays have an elongate form (cf. K. J. Toyne in Thermotropic Liquid Crystals, John Wiley & Sons, Ed., G. W. Gray, 1987, pp. 28ff); these form nematic, cholesteric and smectic phases. In addition, thermotropic liquid-crystalline phases are formed by diskoid molecules (cf. C. Destrade et al., Mol. Cryst. Liq. Cryst. Vol. 106, p.121 (1984)).
SUMMARY OF THE INVENTION
Surprisingly, it has now been found that, in particular, the tetrasubstituted methanes of the general formula --R].sub.4,(II) M, Z.sub.1 and Z.sub.2 are each, independently of one another, --CH.sub.2 CH.sub.2 --, --COO--, --OOC--, --OCH.sub.2 --, CH.sub.2 O --, --C.tbd.C--, --N.dbd.N-- or a single bond; 1,4-phenylene radical which is unsubstituted or monosubstituted to tetrasubstituted by fluorine or chlorine and in which, in addition, one or two CH groups may be replaced by N, or are a 1,4-cyclohexylene radical which has, in particular, a trans-configuration and in which, in addition, one or two non-adjacent CH.sub.2 groups may be replaced by --O--, or are a piperidine-1,4-diyl radical or a 1,4-bicyclo[2.2.2]octylene radical; and that m or n is 1 at least once in one of the four substituents of the methane, liquid-crystalline state to the isotropic phase (clearing point). Consequently, they are highly suitable for use as chemically stable components in liquid-crystalline media which are themselves suitable, due to their favorable optical and dielectric anisotropies, for the production of electro-optical displays, especially as they are chemically and thermally stable.
DESCRIPTION OF THE INVENTION
As is known, such devices are based on the change in the preferential direction of the molecular alignment, which is determined by surface effects, by an electric field. The plane of vibration of polarized light can thereby be rotated or the absorption of dissolved dichroic dyes can be changed. In addition, liquid-crystalline media having advantageous optical properties can be prepared for the production of temperature displays, which are based on selective reflection of natural light (cf. H. Kelker et al., Chem. Ing. Tech., Vol.45, p.1005 (1973)). The novel compounds which contain optically active carbon atoms in one or more radicals R, Sp, Z.sub.1 and Z.sub.2 are suitable for this purpose.
Furthermore, optical storage elements which can be erased by means of the liquid-crystalline media according to the invention can be produced. The principle of such devices is described in D. Coates, Thermotropic Liquid Crystals, John Wiley & Sons, Ed. G. W. Gray, 1987, pp.99ff).
The compounds of the general formula II are furthermore distinguished by low volatility, which is connected to their comparatively high m
REFERENCES:
patent: 4774028 (1988-09-01), Imai et al.
K. J. Toyne, University of Hull, Liquid Crystal Behavior in Relation to Molecular Structure, pp. 29-62.
C. Destrade, Disc-like Mesogen Polymorphism, pp. 122-146, Mol. Cryst. Liq. Cryst., 1984, vol. 106.
H. Kelker, Chemie Ingenieur Technik, Verfahrenstechnik Techn Chemie, Apparatewesen, 2 Aug.-Heft 1973, Heft 16, pp. 1005-1048.
Technische Anwendungen flussiger Kristalle.
D. Coates, Standard Telecommunication Laboratories, Materials Requirements for Smetic Liquid Crystal Displays, pp. 99-118.
"Handbook of Liquid Crystals" Schumann, pp. 69-113 edited by Kelker/Rolf Hatz, Basil, 1980.
"Synthesis of Calamitic Liquid Crystals by Transition Metal Catalyzed Cross-Coupling Reaction", Portsch Kontakte (Darmstadt) 1988 (2) pp. 15-28.
"Liquid Crystals" Tschierske et al. vol. 5, No. 1, pp. 177-190 1989.
Consortium fur Elektrochemische Industrie GmbH
Wu Shean
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