Difluorobenzonitriles and liquid-crystalline medium

Details Difluorobenzonitriles and liquid-crystalline medium Difluorobenzonitriles and liquid-crystalline medium

1990-11-19

1993-04-20

Stoll, Robert L.

Compositions

Liquid crystal compositions

Containing nonsteryl liquid crystalline compound of...

25229963, 25229966, 544242, 544335, 546286, 546301, C09K 1934, C09K 1930, C07D23902, C07D21384

Patent

active

052040178

DESCRIPTION:

BRIEF SUMMARY
SUMMARY OF THE INVENTION

The invention relates to novel difluorobenzonitriles of the formula I ##STR4## in which Y is alkyl, alkenyl, alkoxy, oxaalkyl or alkenyloxy containing in each case 1 to 12 carbon atoms, ##STR5## where X is CH or N, and the other radical A.sup.1 or A.sup.2 is selected from the group comprising ##STR6## one of the radicals Z.sup.1 and Z.sup.2 is a single bond and the other radical Z.sup.1 or Z.sup.2 is --CH.sub.2 CH.sub.2 -- or a single bond, and and one of the radicals A.sup.1 and A.sup.2 =2,5-pyrimidinediyl and the other radical A.sup.1 or A.sup.2 =1,4-phenylene, A.sup.1 is 2,5-pyrimidinediyl.
The invention relates furthermore to the use of said compounds as components of liquid-crystalline media and also liquid crystal and electro-optical display components which contain the liquid-crystalline media according to the invention.
The compounds of the formula I can be used as components for liquid-crystalline media, in particular for displays based on the principle of the twisted cell, the guest-host effect, the deformation of aligned phases effect or the dynamic scattering effect.
The object of the invention was to find novel, stable, liquid-crystalline or mesogenic compounds which are suitable as components of liquid-crystalline media and, in particular, at the same time have a comparatively low viscosity and also an extremely high dielectric anisotropy accompanied at the same time by good low-temperature behavior.
It has now been found that compounds of the formula I are eminently suitable as components of liquid-crystalline media. In particular, they have comparatively low viscosities. With their aid, stable liquid-crystalline media with a wide mesophase range and advantageous values for the optical and dielectric anisotropy can be obtained.
Liquid crystals of the formula ##STR7## are already known from DE 3,209,178. EP 0,317,175 discloses pyrimidine derivatives of the formula ##STR8## which are, however, notable for very high melting points.
In view of the wide variety of fields of application of those compounds having very high .DELTA..epsilon., it was, however, desirable to have further compounds available which have properties made-to-measure for the particular applications and have markedly higher values for .DELTA..epsilon., than the compounds known from DE 3,209,178 and have more beneficial mesophases, better miscibility with other liquid crystals and higher thermal and UV stability than the compounds known from EP 0,317,175.
In addition, the provision of the compounds of the formula I very generally extends appreciably the range of liquid-crystalline substances which are suitable for preparing liquid-crystalline mixtures from various application engineering points of view.
The compounds of the formula I have a wide field of application. Depending on the choice of the substituents, these compounds can serve as base materials from which liquid-crystalline media are predominantly composed; however, compounds of the formula I may also be added to liquid-crystalline base materials from other compound classes in order, for example, to influence the dielectric and/or optical anisotropy of such a dielectric and/or to optimize its threshold voltage and/or its viscosity.
The compounds of the formula I are colorless in the pure state and form liquid-crystalline mesophases in a temperature range which is beneficially situated for electro-optical use. They are stable chemically, thermally and towards light.
The invention consequently relates to the compounds of the formula I and also to the use of said compounds as components of liquid-crystalline media. The invention furthermore relates to liquid-crystalline media having a content of at least one compound of the formula I and also to liquid crystal display components, in particular electro-optical display components which contain such media.
The compounds of the formula I accordingly embrace compounds of the subformulae Ia to Im: ##STR9## Of these, those of the formulae Ia and Id are particularly preferred.
Y preferably denotes alkyl

REFERENCES:
patent: 4512636 (1985-04-01), Andrews et al.
patent: 4551264 (1985-11-01), Eidenschink et al.
patent: 4853152 (1989-08-01), Goto

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