2-Fluorocyclohexene derivatives

Details 2-Fluorocyclohexene derivatives 2-Fluorocyclohexene derivatives

1995-04-05

1996-10-01

Wu, Shean C.

Compositions

Liquid crystal compositions

25229961, 25229963, 25229962, 25229966, 359103, 570131, C09K 1952, C09K 1934, C09K 1930, G02F 113, C07C 2310

Patent

active

055608639

DESCRIPTION:

BRIEF SUMMARY
This application is a 371 of PCT/EP94/02546 filed Aug. 1, 1994.
The present invention relates to 2-fluorocyclohexene derivatives of the formula I ##STR2## where R is an alkyl or alkenyl radical having up to 18 carbon atoms which is unsubstituted or substituted by CN or by at least one halogen and in which one or more non-adjacent CH.sub.2 groups can be replaced by a radical selected from the group consisting of --O--, --S--, --CO--, --O--CO--, --CO--O-- and --C.tbd.C--, replaced by N, CH.sub.2 groups can be replaced by --O-- or --S--, 1,4-bicyclo[2.2.2]octylene or naphthalene-2,6-diyl radical, halogen atoms or cyano and/or methyl groups, --OCH.sub.2 --, --CH.sub.2 O--, --C.tbd.C--, --(CH.sub.2).sub.4 --, --CH.dbd.CH--CH.sub.2 CH.sub.2 -- or a single bond, --O--, --S-- or a single bond, and Y is CN, F, Cl or halogenated alkyl or alkenyl having 1 to 5 carbon atoms, Cl or CN, L.sup.1 and L.sup.2 are fluorine.
The invention furthermore relates to the use of these compounds as components of liquid-crystalline media and to liquid-crystal and electro-optical display elements containing the liquid-crystalline media according to the invention.
The compounds of the formula I can be used as components of liquid-crystalline media, in particular for displays based on the principle of the twisted cell, including highly twisted variants thereof, such as, for example, STN or SBE, the guest-host effect, the effect of deformation of aligned phases or the effect of dynamic scattering, in particular from matrix liquid-crystal displays (MLC displays).
The invention had the object of finding novel, stable, liquid-crystalline or mesogenic compounds which are suitable as components of liquid-crystalline media and in particular have comparatively low viscosity and high positive dielectric anisotropy.
Compounds of the formula ##STR3## are disclosed in J0 5310616.
It has now been found that compounds of the formula I are eminently suitable as components of liquid-crystalline phases. In particular, they have comparatively low viscosities. They can be used to obtain stable liquid-crystalline phases having a broad mesophase range advantageous values for the optical and dielectric anisotropy, which are at the same time distinguished by very favorable values for the resistivity. Significant advantages can thus be achieved, in particular in the case of media for matrix liquid-crystal displays (MLC displays) or Supertwist displays.
In addition, the provision of compounds of the formula I very generally considerably broadens the range of liquid-crystalline substances which are suitable, from various application points of view, for the preparation of liquid-crystalline mixtures.
The compounds of the formula I have a broad range of applications. Depending on the chosen substituents, these compounds can be used as base materials from which liquid-crystalline phases are predominantly composed; however, it is also possible to add compounds of the formula I to liquid-crystalline base materials from other classes of compound in order, for example, to modify the dielectric and/or optical anisotropy of the dielectric of this type and/or to optimize its threshold voltage and/or its viscosity and/or resistivity.
In the pure state, the compounds of the formula I are colorless and form liquid-crystalline mesophases in a temperature range which is favorably located for electro-optical use. They are stable chemically, thermally and to light.
The invention thus relates to the compounds of the formula I, in particular the compounds of the formula I in which n+m=2 and/or L.sup.1 and L.sup.2 are F.
The invention furthermore relates to the use of these compounds as components of liquid-crystalline media.
The invention furthermore relates to liquid-crystalline media containing at least one compound of the formula I and to liquid-crystal display elements, in particular electro-optical display elements, in particular matrix liquid-crystal displays, containing media of this type.
For reasons of simplicity, A.sup.2 below denotes ##STR4## Cyc denotes a 1,4-cyclohexy

REFERENCES:
patent: 4846998 (1989-07-01), Pohl et al.
patent: 5356560 (1994-10-01), Reiffenrath et al.

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