JPS5846497B2 - 1 4-Bis-(4'-Methylhydroquinone ester)-Methylhydroquinone ester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a novel organic compound that exhibits a nematic liquid crystal state with negative dielectric anisotropy at temperatures above its melting point.

Nematic liquid crystals having negative dielectric anisotropy are used in display devices that utilize the fact that applying a voltage to vertically aligned liquid crystal cells disturbs the alignment of liquid crystal molecules and causes light scattering.

Organic compounds used in liquid crystal display devices must be in a nematic state, so the nematic temperature range of the liquid crystal material must be wide, especially in order to use the liquid crystal display device at temperatures in a natural environment without a constant temperature device. Practically required.

However, there is currently no single compound that satisfies these requirements, and therefore only compositions consisting of several types of compounds can be put to practical use.

Each of the compounds constituting the liquid crystal composition having a wide nematic temperature range is required to have an appropriate temperature range and as wide a nematic temperature range as possible.

In general, the nematic temperature range of a single compound having negative dielectric anisotropy is relatively wide, at most 50°C, and 100°C is an exception.

An example of one exhibiting this exceptionally wide nematic temperature range is the ()-compound shown below or its analogous compound.

An object of the present invention is to provide a novel nematic liquid crystal compound that is a single compound and has a wide nematic temperature range and negative dielectric anisotropy, and a method for producing the same.

→(The present inventors searched for a compound having a wide nematic temperature range that can be used for the above purpose, and found that the compound represented by the following formula (I) has a wider nematic temperature range, and arrived at the present invention. .

(In the formula, R represents a straight-chain alkyl group having 3 to 9 carbon atoms.) That is, the present invention is characterized in that 4-acyloxybenzoic acid is condensed with methylhydroquinone via its acid chloride. The present invention relates to a method for producing 1,4-bis-(4'-acyloxybenzoic acid)-methylhydroquinone ester.

These are novel compounds and are very useful as nematic liquid crystals.

The 4-acyloxybenzoic acid used in the present invention is produced by a known method and purified before use.

Furthermore, the methylhydroquinone used in the present invention can be produced by a known method or purified from a commercially available product.

To obtain an ester of 4-acyloxybenzoic acid and methylhydroquinone, first an acid chloride of 4-acyloxybenzoic acid is prepared and then reacted with methylhydroquinone.

To describe this reaction force method in more detail, first, thionyl chloride in an amount of 4-acyloxybenzoic acid or more, preferably 1.2 to 1.5 molar equivalents, is added to a certain amount of 4-acyloxybenzoic acid, and the mixture is heated under reflux for a certain period of time to form an acid. After distilling off excess thionyl chloride under reduced pressure, a suitable inert solvent (eg, benzene, toluene, etc.) is added to dissolve and dilute.

Prepare a cold solution of 1 molar equivalent of methylhydroquinone (preferably a purified product) of this acid chloride in several times the amount of pyridine that can be dissolved at room temperature, and add this to the inert solution of the acid chloride. is added dropwise with stirring and heated slowly for about 1 hour.It is convenient to use an inert solvent such as benzene because the temperature of the reactant can be kept constant by reflux.

After the reaction is completed, the reaction product is poured into cold water, and after adding an appropriate amount of an inert solvent, the aqueous layer is separated and washed in the order of dilute hydrochloric acid, 6N aqueous sodium hydroxide solution, and water.

Then, after distilling off the inert solvent, purification using a suitable recrystallization solvent (e.g., evaluene, benzene, ethanol, etc.) yields colorless crystals of 1,4-bis(4/-acyloxybenzoic acid)-methylhydroquinone. The ester, compound (I), is obtained.

The melting point of compound (I) is around 140°C, and the nematic temperature range is wide over 100°C (all of the above-mentioned known compounds are below 100°C).

Since Compound (I) has a wide nematic temperature range in this way, it can be added to a mixture of other liquid crystal compounds having negative dielectric anisotropy to create dynamic scattering liquid crystals with a wide nematic temperature range. Not only can it be used for display, but also
In addition to liquid crystal compositions having positive dielectric anisotropy, by widening the nematic temperature range of the liquid crystal composition, it can also be used in field-effect liquid crystal displays.

Hereinafter, embodiments of the present invention and its effects will be described in more detail with reference to Examples and Application Examples.

Example 1 1.4-bis-(4'-butyryloxybenzoic acid dimethylhydroquinone ester ((■) in the formula R-C3
In the case of H7).

4-Butyryloxybenzoic acid 20.8, F (0,1
14.3 mol) of thionyl chloride was placed in a 3001 rLl eggplant-shaped flask. Add F (0.12 mol) and gently reflux on a heating mantle for 1 to 2 hours.

After completion of the reaction, the pressure was reduced to remove excess thionyl chloride, and then 30 portions of benzine was added vertically.

Meanwhile, in a 200ml flask, add 6.4 ml of methylhydroquinone.
g (0.05 mol) is dissolved in 16 ml (0.2 mol) of pyridine, and the above acid chloride solution is slowly added thereto while cooling.

After heating this in a water bath for about 2 hours, it was poured into ice water, benzene was added, and after washing with dilute hydrochloric acid, 6N aqueous sodium hydroxide solution, and water in that order, the benzene was distilled off, and the remaining crystals were recrystallized with benzene. 17.9& of colorless crystals were obtained (yield 71.0%).

This crystal, ie, 1,4-bis-(4'-butyryloxybenzoic acid)-methylhydroquinone, exhibited a nematic liquid crystal state over a wide range of 133 to 250°C (temperature: 117°C).

The elemental analysis values are as follows, and the infrared absorption spectrum is shown in FIG.

Example 2 1.4-bis-(4'-octanoyloxybenzoic acid)
-Methylhydroquinone ester (R=C in formula (I)
7H1)).

In Example 1 above, 4-octanoyloxybenzoic acid 26.4.9 (0,
46.4 g of colorless crystals were obtained (yield 75.2%) in exactly the same manner except that 1 mol) was used.

This compound, 1,4-bis-(4'-octanoyloxybenzoic acid)-methylhydroquinone ester, is 141
It exhibited a liquid crystal state between ~243°C (temperature within 10200°C).

Moreover, the elemental analysis values were as follows.

The nematic temperature range of a 3=2 (molar ratio) mixture of p-methoxybenzylidene-p'-n-butylaniline and p-ethoxybenzylidene-p'-n-butylaniline is -10 to 56°C; 1,4-bis-(4'-butyryloxybenzoic acid)- obtained in Example 1
By adding 3 parts by weight of methylhydroquinone ester, it was possible to achieve a nematic temperature range of -5 to 65°C.

By sealing this mixed liquid crystal into a vertically aligned liquid crystal cell assembled using two transparent indium oxide electrodes, a dynamic scattering type liquid crystal device could be fabricated.

Application example 2 A 1:1 (molar ratio) mixture of pn-butylbenzoic acid-pn-hexyloxyphenyl ester and p-anisic acid-p'-hebutylphenyl ester has a nematic temperature range of 0 to 46°C. However, 1,4-bis-(4'-butyryloxybenzoic acid)- obtained in Example 1 was added to this mixture.
By adding 3 weights of methylhydroquinone ester, a nematic temperature range of -2 to 53°C could be achieved, and a dynamic scattering liquid crystal device could be produced in the same manner as in Application Example 1.

[Brief explanation of the drawing]

FIG. 1 is an infrared absorption spectrum of the compound of the present invention (formula (I) with R=C3H7) obtained in Example 1.

Claims (1)

[Claims] A general formula characterized by condensing 14-acyloxybenzoic acid with methylhydroquinone via its acid chloride (in the above formula, R represents a linear alkyl group having 3 to 9 carbon atoms) A method for producing 1,4-bis-(4'-acyloxybenzoic acid)-methylhydroquinone ester represented by: