3,4,5-trifluorobenzenes, and their use in liquid-crystal mixture

Details 3,4,5-trifluorobenzenes, and their use in liquid-crystal mixture 3,4,5-trifluorobenzenes, and their use in liquid-crystal mixture

1996-04-04

1998-02-10

Wu, Shean C.

Compositions

Liquid crystal compositions

Containing nonsteryl liquid crystalline compound of...

25229961, 25229966, 25229967, 25229901, 349182, C09K 1930, C09K 1934, G02F 113

Patent

active

057165432

DESCRIPTION:

BRIEF SUMMARY
DESCRIPTION

This application is a 371of PCT/EP/94/032, filed Sep. 26, 1994.
The unusual combination of anisotropic and fluid behavior of liquid crystals has led to their use in electro-optical switching and display devices, where their electrical, magnetic, elastic and/or thermal properties can be utilized for changes in alignment. Optical effects can be achieved, for example, with the aid of birefringence, the inclusion of dichroic dye molecules (guest-host mode) or light scattering.
Practical requirements are constantly increasing, not least because of the constantly increasing number of types of light valve (TN, STN, DSTN, TFT, ECB, DECB, DS, GH, PDLC, NCAP, SSFLC, DHF, SBF, etc). In addition to thermodynamic and electro-optical quantities, such as phase sequence and phase temperature range, refractive index, birefringence and dielectric anisotropy, response time, threshold voltage, steepness of the electro-optical characteristic line, elastic constants, electrical resistance, multiplexibility or pitch and/or polarization in chiral phases, the stability of liquid crystals to moisture, gases, temperature and electromagnetic radiation and to the materials with which they are in contact during and after the manufacturing process (for example alignment layers) is of considerable importance. Toxicological and ecological acceptability and price are increasing in importance.
A broad review of the area of liquid crystals is given, for example, in the following literature and in the references cited therein: H. Kelker, H. Hatz, Handbook of Liquid Crystals, Verlag Chemie, Weinheim, 1980; W. E. De Jeu, Physical Properties of Liquid Crystal Materials, Gordon and Breach, Philadelphia 1980; H. Kresse, Dielectric Behaviour of Liquid Crystals, Fortschritte der Physik, Berlin 1982, 30, 507-582; B. Bahadur, Liquid Crystals: Applications and Uses, World Scientific, Singapore, 1990; Landolt-Bornstein, New Series, Group IV, Volume 7 Liquid Crystals 1992-1993.
Specific derivatives of 3,4,5-trifluorobenzene and their use in nematic liquid-crystal mixtures are known (cf. DE-A 41 08 448, GB-A 2 253 403, EP-A 507 094, EP-A 502 406, DE-A 41 39 553, WO-A 92/06 148, DE-A 41 12 001, DE-A 41 07 389, EP-A 387 032).
However, since individual compounds have hitherto not been able simultaneously to satisfy all said requirements, there is a continuing demand for novel improved liquid-crystal mixtures and thus for a multiplicity of mesogenic and nonmesogenic compounds of various structures which enable the mixtures to be customized to a wide variety of applications.
Surprisingly, it has now been found that certain derivatives of 3,4,5-trifluorobenzene are particularly suitable for use in liquid-crystal mixtures.
The present invention therefore relates to novel 3,4,5-trifluorobenzene derivatives of the formula (I). ##STR2## in which the symbols and indices have the following meanings: R.sup.1 is H, a straight-chain or branched (with or without an asymmetrical carbon atom) alkyl having 1 to 15 carbon atoms in which, in addition, one or two nonadjacent --CH.sub.2 -groups may be replaced by --O--, CH.dbd.CH--,--C.tbd.C--, cyclopropane-1,2-diyl or --Si(CH.sub.3).sub.2 --, and in which, in addition, one or more H atoms in the alkyl radical may be substituted by F; pyridine-2,5-diyl, pyrimidine-2,5-diyl in which one or two H atoms may be replaced by F, trans-1,4-cyclohexylene, 1,3-dioxane-2,5-diyl or naphthalene-2,6-diyl, --,--CH.dbd.CH--, --C.tbd.C--,--CH.sub.2 CH.sub.2 CH.sub.2 --, --CH.sub.2 CH.sub.2 CH.sub.2 --O--, --O--CH.sub.2 CH.sub.2 CH.sub.2 --, --CH.sub.2 CH.sub.2 CO--O--, --O--CO--CH.sub.2 CH.sub.2 --, --CH.sub.2 --O--, --O--CH.sub.2 --, --CO--O-- or --O--CO--; greater than zero.
The novel substances are distinguished by a favorable temperature position of the nematic phase and by good solubility.
In a preferred embodiment of the invention, the symbols and indices in the formula (I) have the following meanings: which one or two H atoms may be replaced by F, or trans- 1,4-cyclohexylene; --C.tbd.C--, --CH.sub.2 --O--, --O--CH.sub.2 --,

REFERENCES:
patent: 5032313 (1991-07-01), Goto et al.
patent: 5487845 (1996-01-01), Reiffenrath et al.

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