GB2138437A

GB2138437A - Cyclohexanecarboxylic acid liquid-crystal materials

Info

Publication number: GB2138437A
Application number: GB08310766A
Authority: GB
Inventors: Alexandr Vasilievic Ivaschenko; Ljudimila Alexeevn Karamysheva; Mikhail Fedorovich Grebenkin; Vladimir Grigorievi Rumyantsev; Evgeny Ivanovich Kovshev; Viktor Vasilievich Titov; Sofia Isaakovna Torgova; Ute Bottger; Adelbert Wiegeleben; Horst Zaschke; Dietrich Demus
Original assignee: Individual
Current assignee: Individual
Priority date: 1983-04-21
Filing date: 1983-04-21
Publication date: 1984-10-24
Also published as: GB2138437B; GB8310766D0

Abstract

A liquid-crystal material for use in electrooptical devices comprises at least: two 4-n-alkyl-trans- cyclohexanecarboxylic acids of the formula <IMAGE> wherein n = 4 to 6, the components being present in the following proportions, per cent by weight: 4-n-butyl-trans-cyclohexanecarboxylic acid 31 to 65, 4-n-amyl-trans-cyclohexanecarboxylic acid 14 to 33, and/or 4-n-hexyl-trans-cyclohexanecarboxylic acid 30 to 60. It may also incorporate 2 to 25% by weight of a 4-n-alkyl-trans-cyclohexanecarboxylic acid nitrile of the formula: <IMAGE> wherein n = 2 to 8.

Description

SPECIFICATION Liquid crystal material The present invention relates to liquid crystals and, more specifically, to liquid-crystal materials which are useful as a working body in electrooptical devices, as anisotropic solvents for spectroscopy and as a liquid phase in gas-liquid chromatography.

One of the most important characteristics of a liquid-crystal material is a temperature range of the existence of the mesophase limited by the transition into the solid-crystal state on the side of low temperatures and by the transition into a common isotropic liquid on the side of high temperatures. Liquid-crystal materials are mixtures if several individual compounds. The temperature range of the mesophase of such a mixture is determined by the properties of the mixture components and by the number thereof.

An increased number of components results in a broadened range of the mesophase temperature. Multicomponent mixtures, however, are more complicated in manufacture. Temperatures of phase transitions of most advantageous basic mixtures which can be used for preparing liquid-crystal materials are shown in Table 1 hereinbelow (cf. Proceedings of "10 Freiburger Arbeitstagung Flussigekristalle", March, 1980).

Also known is a liquid-crystal material which is a mixture consisting of 70% by weight of 4-nbytyl-trans-cyclo-hexanecarboxylic acid and 30% by weight of 4-n-hexyl-trans-cyclohexanecarboxylic acid having a nematic phase within the temperature range of from 1 5 to + 95"C (cf.

G.W.Gray, D.G.McDonnel, 7 Congres International de Cristaux Liquides, Bordeaux, 1978, Abstr. A 02).

Table 1

No. Formula of the compound Content of Temperature, C of: incorporated in the the compo liquid-crystal material und, wt. % melting clearing 1 15 C3 H7 MCN C5H MCN CN 52 0 + 36 C7H15 H15 33 2 29 C3 H7 C5H11McN 41 -3 +50 C7 Ij1HCN 30 3 32 C3H7 2}COO v CN C5H11COO CN 42 +19 +76 7 HiSH COO CN 26

4 23 C3H7COO W OC2H5 C9COO vOC2H5 38 +15 +72 CsHnCOO OCH3 39 The basic disadvantages of these materials reside in a narrow temperature range of liquidcrystal state of the mesophase and a high melting point which restricts their use, especially within the range of low temperatures.

It is an object of the present invention to provide a liquid-crystal material possessing a wide temperature range of the nematic mesophase existence and a low melting point which would make it possible to broden the field of its applications.

This object has been accomplished by the provision of a liquid-crystal material comprising, according to the present invention, at least two 4-n-alkyl-trans-cyclohexanecarboxylic acids of the general formula:

wherein n = 4 to 6, the components being used in the following proportions, percent by weight: 4-n-butyl-trans-cyclohexanecarboyxlic acid 31 to 65 4-ny-amyl-trans-cyclohexanecarboxylic acid 14 to 33 and/or 4-n-hexyl-trans-cyclohexanecarboxylic acid 30 to 60.

An embodiment of the material according to the present invention is a liquid-crystal material which, in order to lower melting temperature and increase anisoptropy of dielectric constant, additionally contains 4-n-alkyl-trans-cyclo-hexanecarboxylic acid nitrile of the general formula:

wherein n = 2 to 8.

The amount of the nitrile can be varied within the range of from 2 to 25% by weight. The present invention relates to liquid-crystal materials with low melting temperatures (down to - 34"C) and high (up to 93"C) clearing temperatures. The material according to the present invention also incorporates two or three components and its manufacture is substantially more simple than that of the prior art liquid crystals. The materials according to the present invention have a high (up to 10" Ohm.m) resistivity and the value of dielectric anisotropy very close to zero. This enables their use as basic materials for the creation of liquid-crystal mixtures for electrooptical devices operating both on the effect of dynamic light scattering and on the basis of field orientation effects.

The liquid-crystal material according to the present invention in practicing thereof is produced by way of mixing, in the above-specified weight proportions, the components mentioned hereinbefore, followed by heating of the resulting mixture to a temperature by 5-10"C above the clearing temperature and subsequent cooling to room temperature.

For a better understanding of the present invention some specific examples illustrating compositions of the liquid-crystal material are given hereinbelow by way of illustration.

Example 1 A liquid-crystal material is prepared by mixing 39.5% by weight of 4-n-butyl-trans-cyclohexanecarboxylic acid, 39.5% by weight of 4-n-hexyl-trans-cyclohexanecarboxylic acid and 21% by weight of 4-n-hexyl-trans-cyclohexanecarboxylic acid nitrile. The resulting mixture is heated to the temperature of 70 C under stirring and then cooled to room temperature. The thus-produced material has the following characteristics: melting point - 34"C, clearing temperature + 58 C.

The material according to the present invention as produced in this Example is a turbid liquid in the liquid crystalline state and a colourless transparent liquid in the isotropic state, stable in storage and operation in electrooptical cells.

In Table 2 Examples 2 through 9 are summarized illustrating compositions of the liquidcrystalline material according to the pesent invention and properties thereof.

Table 2 Composition Temperature, C, F: Example (component and its No. content, per cent by weight) melting clearing 1 2 3 4 2 1-40.0 11-40.0 - 33 + 57 IV-20.0 3 1-50.0 - 27.0 + 93.0 11-50.0 4 1-49.5 11-50.5 - 25 . - 27 + 92.8 5 II-49.5 #24#-27 + 93.2 11-49.5 6 1-40.5 11-40.5 - 32 + 60 IV-19.0 7 1-39.5 11-39.5 -34 + 60 V-21.0 8 1-31 111-33 - 8 + 98.2 11-36 9 1-54.2 111-1 4.6 - II + 93.2 11-31.2 The symbols employed in Table 2 stand for: 1-4-n-butyl-trans-cyclohexanecarboxylic acid; II-4-n-hexyl-trans-cyclohexanecarboxylic acid; III-4-namyl-trans-cyclohexanecarboxylic acid; IV-4-n-butyl-trans-cyclohexanecarboxylic acid nitrile; v-4-n-hexyl-trans-cyclohexanecarboxylic acid nitrile.

Claims

1. A liquid-crystal material containing at least two 4-n-alkyl-trans-cyclohexanecarboxylic acids of the general formula

wherein n = 4 to 6, the components being used in the following proportions, per cent by weight: 4-n-butyl-trans-cyclohexanecarboxylic acid 31 to 65 4-n-amyl-trans-cyclohexanecarboxylic acid 14 to 33 and/or 4-n-hexyl-trans-cyclohexanecarboxylic acid 30 to 60.

2. A liquid-crystal material according to Claim 1, containing 50% by weight of 4-n-butyltrans-cyclohexanecarboxylic acid and 50% by weight of 4-n-hexyl-trans-cycloxanecarboxylic acid.

3. A liquid-crystal material according to Claim 1, incorporating a 4-n-alkyl-trans-cyclohexanecarboxylic acid nitrile of the formula:

wherein n = 2 to 8.

4. A liquid-crystal material according to Claim 3, wherein the content of said 4-n-alkyl-transcyclohexane-carboxylic acid nitrile is 2 to 25% by weight.

5. A liquid-crystal material according to Claim 1, 3 and 4 which consists of 39.5% by weight of 4-n-butyl-trans-cyclohexanecarboxylic acid, 39.5% by weight of 4-n-hexyl-transcyclohexanecarboxylic acid and 21.0% by weight of 4-n-hexyl-trans-cyclohexanecarboxylic acid nitrile.

6. A liquid-crystal material according to any one of the foregoing Claims 1 to 5, substantially as disclosed in the Specification and Examples 1 through 9 hereinbefore.