JPS6050177B2 - liquid crystal compound - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to novel ester-based liquid crystal compounds and mixtures thereof.

As is well known, in order to use a liquid crystal display element for general purposes, the liquid crystal material used therein is required to maintain a liquid state over as wide a temperature range as possible and to be stable.

It is difficult to meet these requirements with a single compound, and at present it is common to use a mixture of several types of liquid crystal compounds. The present invention is a novel liquid crystal compound that can be used for this purpose, exhibiting a nematic state near room temperature, and is very useful as a component of nematic liquid crystals used in various liquid crystal device systems. Deutscher et al., in East German patent WP 105701, describe several p-alkylphenyl esters of trans-4-n-pentylcyclohexanecarboxylic acid. That is, in the above compound, the p-alkyl group is an ethyl group (p-
The nematic liquid crystal temperature range of ethyl phenyl ester) is 29-42'C, the nematic liquid crystal temperature range of those whose p-alkyl group is n-propyl group is 43-440C, and the nematic liquid crystal temperature range of those whose p-alkyl group is n-pentyl group is 36-42'C. It is stated that the nematic liquid crystal temperature range is 480C.
These compounds are chemically stable and excellent, but for practical use, it is desired that they have a lower melting point and a higher clearing point (N-I point). From this point of view, the present inventors synthesized p-n butylphenyl ester of trans-4-n-bentylcyclohexanecarboxylic acid with a longer p-alkyl group, but the crystals of this product melted at 37°C. It turned out to be a smectic liquid crystal, changed from a smectic state to a nematic state at 47°C, and became a transparent liquid at 51°C, which is a rather unfavorable tendency for a nematic liquid crystal. This suggests that in this type of liquid crystal, by lengthening the p-alkyl group of the phenyl group, the tendency to adopt a smectic state becomes stronger. Therefore, the present inventors searched for a similar compound with a shorter chain length of the alkyl group attached to the phenyl group and a wider nematic temperature range.As a result, the length of the alkyl group attached to the cyclohexane ring was determined. The present invention was achieved by discovering that a more preferable compound can be obtained when the length is shortened. That is, the present invention is a pn-alkylphenyl ester of trans-4-butylcyclohexanecarboxylic acid represented by the following general formula (1) and a mixture containing the same.

(However, in the above formula, m represents an integer of 4 to 7.) This compound is produced by a method as shown in Examples later, and in the formula (1) obtained in this way, m = 4,5 , 6, 7, and 8 are shown in Table 1.

Among the above, the compound where m=8 does not take a nematic state but only a smectic state and cannot be used as a linematic liquid crystal.

All other compounds with m=4,5,6,7 are trans-41n-pentylcyclohexacarboxylic acid p-
It has a favorable characteristic of having a lower melting point than alkyl cyanophenyl esters (where the alkyl group is ethyl, propyl, or pentyl). Next, Table 2 shows examples of liquid crystal materials in which 2 to 4 components of the present compound are mixed.

This is better than treating one compound alone.
This is because it is more convenient to use a four-component mixed liquid crystal material when it is mixed with other nematic liquid crystals.
It was difficult to measure the C-N point accurately because it has a strong tendency to be in a supercooled state;
It is certain that it is lower than the -N point.

Furthermore, since the N-I point, which is the upper limit of the nematic temperature, is still low, it can be improved by mixing with another nematic liquid crystal having a high N-1 point. For example, the trans-4
-n-pentylcyclohexanecarboxylic acid p-n-pentylphenyl ester (C-N point 36-C, N-1 point 4
8 and others, trans-4-n-pentylcyclohexanecarboxylic acid p-ethoxyphenyl ester (C1N point 35.
1-C, N-1 point 75.1teC), trans-41n-
Pentylcyclohexanecarboxylic acid p-ethoxyphenyl ester (C-N point: 56 DEG C., N-1 point: 85.5 DEG C.) is a preferred compound to be mixed for this purpose.
The liquid crystal mixture thus obtained has negative dielectric anisotropy, is chemically extremely stable and colorless, and has a low viscosity, unlike Schiff compounds represented by MBBM (methoxybenzylidene butylaniline). Since the value is low, the display response speed becomes faster, which is an advantage.

Next, we will show some typical uses of these liquid crystal mixtures: 1 So-called DAP (DefOrmatjO
Use as a base for liquid crystal materials used in electro-optical elements using the nOfAllgnedPhase) method.The liquid crystal mixture described above has a large negative dielectric anisotropy value, such as 4-(2-methylbutyl)biphenyl-4'' monocarboxylic acid. DMP display can be made by adding 4-n-heptyl-2-cyanophenyl ester.

(Example 5). 2. Use as a liquid crystal base for memory type display By adding a cholesterol derivative such as cholesteryl oleyl carbonate to the above liquid crystal mixture, a focal conic white state and a planar transparent state are utilized. A liquid crystal material for memory type display is obtained.

3. Use as a liquid crystal for twisted nematic displays The operational characteristics of liquid crystals for twisted nematic displays (TND) can be improved by mixing the liquid crystal mixture described above with a liquid crystal having positive dielectric anisotropy. .

Example 7, which will be described later, is an example used to adjust the driving voltage of a TND liquid crystal. The method for molding the compound of the present invention and the method for utilizing the same will be explained in more detail below with reference to Examples. Example 1 [Production of compound where m = 4 in formula (1)] 900 y of p-n-butylbenzoic acid, 700 mL of acetic acid,
The platinum oxide catalyst 129 is placed in a 10e stainless steel autoclave, heated and stirred at 60 DEG C. under a hydrogen pressure of 20 to 5 ton, and reacted until almost the theoretical amount of hydrogen has been absorbed.

After degassing, the autoclave is opened to remove the catalyst and the acetic acid is distilled off to obtain a residue of about 920 y. It consists primarily of cis-4-n-butylcyclohexanecarboxylic acid. This product was heated at 200°C with 7e of N-methyl-2-pyrrolidone and 450q of sodium methoxide.
After heating and stirring for a while, the mixture was cooled, water 15e was added thereto, acidified with hydrochloric acid, and extracted with 3' hexane. After washing the hexane solution with water, the hexane is distilled off, and the target product is distilled under reduced pressure. Boiling point 136-138 C (1.5 wrftHg) yield 90
It was 0g. This is trans-n-4-cyclohexanecarboxylic acid containing a small amount of cis isomer. Next, add 90f of thionyl chloride to this 100y! After heating on a water bath for 1 hour, excess thionyl chloride was distilled off.
The residue is trans-4-n-butylcyclohexanecarboxylic acid chloride. This acid chloride was added to a solution of p-n-butylphenol 81y dissolved in pyridine 150mt, and the reaction was carried out at 50°C for 1 hour. Hydrochloric acid was added under ice cooling to make it acidic, and then extracted with toluene. The extract was washed with water. After washing with dilute caustic soda solution and re-washing with water, toluene is distilled off and recrystallized from ethanol to obtain colorless crystals of 76V, ie, p-n-butylphenyl ester of trans-4-n-butylcyclohexanecarboxylic acid.

This crystal once melts at 24.5°C and then has a melting point of 25.
New crystals form at 2°C.

Also, this one is a monotropic liquid crystal and the N-1 point is 20'C.
It is. The elemental analysis values agreed well with the theoretical values as shown below, and it was confirmed that the product was the desired product. Analytical value Theoretical value (as C2lH32O2) C79.5%
79.69%HlO. 20%
(1) Formula m= Compounds 5, 6, 7, and 8 were produced in the same manner as in Example 1.

All are colorless crystals, and their respective elemental analyses, infrared absorption spectra, and non-NMR spectra do not contradict each other as structural formulas. Also, the liquid crystal temperature range of these compounds is the same as the first one above.
As shown in the table. Example 5 Trans-4-n-butylcyclohexanecarboxylic acid p-n-butylphenyl ester (m=4 in formula (1)) (to) trans-4-n-butylcyclohexanecarboxylic acid p-n- Pentylphenyl ester (m=5 in formula (1)) (
A) Trans-4-n-butylcyclohexanecarboxylic acid p-ethoxyphenyl ester (A) Trans-4-n-pentylcyclohexanecarboxylic acid p-ethoxyphenyl ester 2(2)4-(2-
methylbutyl)biphenyl-4″monocarphonic acid 4-n-
A mixed liquid crystal consisting of 11 parts of heptyl-2-cyanophenyl ester (the manufacturing method is shown in Reference Example 2) was prepared,
When this mixed liquid crystal is sealed in a cell made by combining two sheets of Nesa glass with vertical alignment surface treatment, the liquid crystal becomes uniformly vertically aligned and can be viewed by sandwiching it between two linear polarizers arranged in parallel Nicols. When it is worshiped, light passes through it.

When a voltage is applied to the Nesa film and observed, light is blocked by the so-called DAP effect. In this case, the response threshold voltage is 2.7V
, the saturation voltage was 3■. Reference Example 2 [Synthesis of 4-(2-methylbutylbiphenyl-4'-monocarboxylic acid 4-n-heptyl-2-cyanophenyl ester)] 4-(2-methylbutyl)biphenyl-4'-monocarboxylic acid is a patent application of the present applicant. Japanese Patent Application No. 50-44496
1-122045) by a method similar to the synthesis method described in No. 1-122045).

This material has a melting point of 22rC and a clearing point of 245°C. On the other hand, 4-n-heptyl-2-cyanophenol is 4-n-
N heptyl-2-bromophenol and cuprous cyanide
-Synthesized by reacting in 200°C for 4 hours in methyl-2-pyrrolidone. It is a pale yellow crystal with a melting point of 87°C. Add an excess of thionyl chloride to 4-(2-methylbutyl)-biphenylcarboxylic acid, heat under reflux for 1 hour to convert it to acid chloride, distill off the excess thionyl chloride, and then add equimolar 4-thionyl chloride in the presence of an excess of pyridine. -Heptyl 2
- reacted with cyanophenol.

By recrystallizing the product from ethanol, 4-(2
-methylbutyl)-biphenyl-4'-. carboxylic acid 4
-Heptyl cyanophenyl ester was obtained as colorless crystals. The melting point (C-N point) was 44°C, and the clearing point was 68°C. In addition, the elemental analysis values are as follows and are in good agreement with the theoretical values. Analytical value Theoretical value (as C32H37O2) C82. O% 82.18%H
8. O% 7.98% This was used as a component of the liquid crystal composition of Example 5.

Example 7 p-n-pentyl p''-cyanobiphenyl 45% p-
n-heptyl p'-cyanobiphenyl
3.0%p-n-octyloxy-p″-cyanobiphenyl
15% p-n-pentyl-p''-cyanoterphenyl
A liquid crystal mixture with a composition of 10% has a nematic temperature range of -10°C to 60°C, the threshold voltage of the electro-optic effect by the TND (twisted nematic display) method is 1.4V, and the saturation voltage is 2.1V ( 25℃).

A liquid crystal composition obtained by adding and mixing part of trans-4-cyclohexanecarboxylic acid p-ethoxyphenyl ester and w part of trans-n-fubutylcyclohexanecarboxylic acid p-n-heptyl phenyl ester to 70 parts of this liquid crystal composition is - It has a nematic temperature range of 20°C to 62'C, the threshold voltage of the TND method effect is 1.8cm, the saturation voltage is 2.5V, and the dynamic drive is much lower than that of the original composition. characteristics become superior. Example 8 Trans-4-n-butylcyclohexanecarboxylic acid p
-n-butylphenyl ester (m=4 in formula (1)
2-trans-4-n-butylcyclohexanecarboxylic acid p-n-pentylphenyl ester (Compound where m=5 in formula (1)) 2-trans-4-n-butylcyclohexanecarboxylic acid p-n-hexylphenyl ester Ester (compound where m=6 in formula (1)) 2-trans-4-n-butylcyclohexanecarboxylic acid p-ethoxyphenyl ester 2-4
-(2-methybutyl)biphenyl-4″ monocarboxylic acid 4
The liquid crystal composition obtained by mixing -n-pentylphenyl ester w part 4-(β-n-propyloxy)ethoxybenzoic acid 4'-cyanophenyl ester 1CyIffI) is a liquid crystal having positive dielectric constant anisotropy. The nematic liquid crystal temperature range is 2 to 56°C.

Claims (1)

[Claims] 1. Trans-4 represented by the general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (I) (in the above formula, m represents an integer from 4 to 7)
-p-alkylphenyl ester of n-butylcyclohexanecarboxylic acid. 2 A nematic liquid crystal characterized by containing at least one compound represented by the general formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (II) (in the above formula, m represents an integer from 4 to 7) material.