JPH086047B2 - Dichroic trisazo dye for liquid crystal display - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a novel trisazo dichroic dye for liquid crystal display.

[0002]

2. Description of the Related Art In recent years,
Liquid crystal display devices have been widely used from the viewpoint of energy saving and miniaturization. Most of the currently used liquid crystal display elements utilize the electro-optical effect of twisted nematic type liquid crystal, and display is made with the combination of two polarizing plates as an essential condition. The reality is that there are many restrictions. As an alternative liquid crystal display method, so-called guest-host type liquid crystal display utilizing the electro-optical effect of a colored liquid crystal composition in which a dichroic dye is dissolved in a nematic liquid crystal has been studied, and some of them have already been used for watches and home appliances. It has begun to be used as a display element in products and industrial instruments.

The principle of this guest-host type liquid crystal display system is that the dichroic dye molecules which are guests are oriented and arranged according to the arrangement of the liquid crystal molecules which are hosts. That is, when an external stimulus is applied, usually with an electric field, the liquid crystal molecules change their alignment direction from the “off” state to the “on” state, but at the same time, the dichroic dye molecules also change the alignment direction. As a result, it is based on the principle that the degree of light absorption by the dye molecules in both states changes, and display is performed.

The dichroic dye used here has sufficient coloring ability even in a small amount, has a large dichroic ratio,
Basic conditions are that it shows a large contrast when no voltage is applied, it has sufficient compatibility with liquid crystals, it has excellent durability and stability, and it does not deteriorate the performance of the device even when used for a long time. It is necessary to prepare for the minimum.

Various dichroic dyes have been proposed to satisfy the above conditions, and some of them are already digital locks.
Although they are beginning to be used in meters, etc., those that show a large dichroic ratio have poor durability, or they have excellent durability but do not have the dichroicity that allows a clear display in practical use. At present, many of them still have drawbacks that need to be improved.

[0006]

Means for Solving the Problems The inventors of the present invention have made diligent studies in view of such circumstances, and as a result, have found a novel dichroic dye having a large dichroic ratio and excellent durability. It was The liquid crystal display dye of the present invention has a biphenyl skeleton having a 4-carbonyloxy group at the terminal of the long axis of the molecule through an azo group, and at least one naphthyl skeleton and a phenyl skeleton, or three phenyl skeletons bonded to the biphenyl skeleton. And a dichroic dye according to the present invention is represented by the general formula (1)

[0007]

[Chemical 3]

[Wherein X represents an alkyl group, an alkoxyalkyl group, a phenyl group or a cyclohexyl group which may be substituted at the p-position with an alkyl or alkoxy group, and P is substituted with a halogen atom, a methyl group or a methoxy group. Optionally 1,4-phenylene group or 1,
Represents a 4-naphthylene group, Ar represents a 1,4-phenylene group or a 1,4-naphthylene group, Y ₁ represents a hydrogen atom, a methyl group or meth

[0009]

[Chemical 4] R is an alkyl group, a phenyl group which may be substituted at the p-position with an alkyl group or an alkoxy group, or a cyclohexyl group, R ₁ is a hydrogen atom or a lower alkyl group, and R ₂ is a lower alkyl group or the p-position. Alkyl,
A benzyl group which may be substituted with an alkoxy or phenyl group. ] It is the dichroic trisazo dye for liquid crystal displays shown by these. Specific examples of X in the general formula (1) for a liquid crystal dye according to the present invention include:

[0010]

[Chemical 5]

Groups having a structural formula such as When an alkyl group is present at the end of X, the number of carbon atoms is preferably 15 or less. Y ₁ and Y ₂ and Y ₃ described later
As specific examples of, -H, -Cl, -Br, -I,-
F, -CN, -OH, -OCH _3, but like -CH ₃ and the like, Y ₁ when to Y ₃ are both hydrogen atoms large dichroic effect, also including the purity and the raw material of the reaction product It is advantageous and preferable in terms of manufacturing cost. Further, as a specific example of Z,

[0012]

[Chemical 6]

Groups having a structural formula such as The trisazo dye of the present invention can be synthesized by a conventional method. For example, the general formula (2)

[0014]

[Chemical 7]

[In the formula, X has the same meaning as in the general formula (1). ] The compound represented by the general formula (3)

[0016]

Embedded image

[Wherein Y ₁ has the same meaning as in the general formula (1). ] The compound represented by the general formula (4)

[0018]

[Chemical 9]

[In the formula, X and Y ₁ have the same meanings as in the general formula (1). ] The monoazo compound represented by this is obtained. Next, the compound of the general formula (4) is diazotized to give the compound of the general formula (5)

[0020]

[Chemical 10]

[Wherein Y ₂ is a hydrogen atom, a halogen atom,
Represents a methyl group or a methoxy group. ] Or a compound represented by the general formula (6)

[0022]

[Chemical 11]

[Wherein Y ₃ is a hydrogen atom, a halogen atom,
Represents a methyl group or a methoxy group. ] The compound of formula (7), which is the precursor of formula (1) of the present invention, is hydrolyzed by coupling with methanesulfonate.

[0024]

[Chemical 12]

[In the formula, X, Y ₁ and P have the same meanings as in the general formula (1). ] The disazo compound represented by these is obtained. Next, these disazo compounds are further diazotized to give a compound represented by the general formula (8)

[0026]

[Chemical 13]

[In the formula, Z ′ represents a hydroxyl group, an amino group or a dialkylamino group. ] The trisazo compound of the general formula (1) can be obtained by coupling with a compound represented by the formula [1]. When Z ′ is a hydroxyl group, Z ′ can be converted into a substituent corresponding to Z in the compound of the general formula (1) by subsequently reacting with a desired alkylating agent or acylating agent after completion of coupling. .

As described above, the trisazo dye of the general formula (1) of the present invention can be synthesized by appropriately selecting the coupling component from the compound of the general formula (2) as a raw material. Further, X in the general formula (1) can be introduced by esterification by a conventional method after synthesizing a trisazo compound using 4'-aminobiphenyl-4-carboxylic acid as a starting material.

The dichroic dye of the present invention can be contained in a liquid crystal and used in a display device usually used as a liquid crystal composition for color display. As the liquid crystal, various liquid crystals, for example, biphenyl liquid crystal (such as Merck's product number E-8),
Phenylcyclohexane liquid crystals (Merck's product numbers ZLI-1132, ZLI-1840, etc.), Schiff base liquid crystals, ester liquid crystals, pyrimidine liquid crystals, tetrazine liquid crystals and other nematic liquid crystals showing positive or negative dielectric anisotropy These may be used alone or in combination. In addition to these nematic liquid crystals, cholesteryl nonanoate or an optically active 4-cyano-
So-called phase transition type liquid crystal to which an optically active substance such as 4′-isopentylbiphenyl is added can also be used. Further, a smectic liquid crystal having so-called display memory performance which exhibits irreversible orientation depending on the direction of voltage application, and a memory type smectic liquid crystal using a liquid crystal having a thermal smectic-nematic phase transition phenomenon can also be used.

The dye according to the present invention may be used alone or in combination of two or more. The concentration of the dye to be used may be within the range in which the dye dissolves in the liquid crystal and within the range in which the dye molecules can be sufficiently aligned and controlled by the alignment of the liquid crystal molecules.
It is preferable to use it at a concentration of 01 to 10% by weight, preferably 0.01 to 5% by weight.

It is also possible to mix the dichroic dye according to the present invention with another dichroic dye or a dye having no dichroism to use as a desired hue, and there is no limitation. The dichroic dye is dissolved in the liquid crystal by mixing a desired amount of the dye with the liquid crystal and stirring the mixture for a long time, or by heating the liquid crystal to a temperature above the temperature at which the liquid crystal becomes an isotropic liquid and stirring it for the desired color display. It can be a liquid crystal composition.

[0032]

EXAMPLES Representative examples of the dichroic dye of the present invention will be specifically described below with reference to Examples and Table-1. The dichroic ratios shown in Examples and Table 1 are characteristic values that most characterize the usefulness of the novel dichroic dyes of the present invention. The dichroic ratios shown in Examples and Table 1 are 0.5% by weight of each dye, and a typical nematic liquid crystal manufactured by Merck Co. (product number ZLI).
-1840) and sealed in a liquid crystal cell with a thickness of 10 μm that has been previously treated for homogeneous alignment, and then placed in the optical path of the spectrophotometer to measure the maximum absorption wavelength with linearly polarized light parallel to the liquid crystal array. Absorbance (A
‖) And the absorbance at the same wavelength (A⊥) measured by applying linearly polarized light at right angles to the liquid crystal array

[0033]

[Equation 1] It is calculated from Parts indicate parts by weight, and% indicates% by weight.

Example 1 Monoazo process formula

[0035]

Embedded image

After dissolving 7 parts of the compound represented by the following in 400 parts of N, N-dimethylformamide (hereinafter abbreviated as DMF), 20 parts of 35% hydrochloric acid was added, and the mixture was cooled to 5 ° C. or lower and 10
% Aqueous solution of sodium nitrite was added dropwise, and the mixture was stirred at the same temperature for 2 hours, and then sulfamic acid was added to obtain a diazotized solution.
After the pH of this diazotized solution was set to 4, 57.5 parts of an aqueous solution in which 7.5 parts of sodium anilinomethanesulfonate was dissolved was added, and the mixture was stirred at 0 to 5 ° C for 2 hours. The reaction solution is ice water 10
It was discharged to 00 parts and filtered. The obtained cake was dispersed in 1 liter of water, stirred at 85 to 90 ° C. for 8 hours, filtered, washed with water, and dried.

[0037]

[Chemical 15] 11 parts of a crude product of the monoazo compound represented by

Disazo step After dissolving 4 parts of the obtained monoazo compound in 200 parts of DMF, 12 parts of 35% hydrochloric acid was added, and the mixture was cooled to 5 ° C. or lower and 10
% Sodium nitrite aqueous solution (12 parts) was added dropwise, the mixture was stirred at the same temperature for 2 hours, and then sulfamic acid was added to obtain a diazotized solution.
To this diazotized solution, 2.2 parts of α-naphthylamine was added to DMF.
What was melt | dissolved in 10 parts was dripped, and it stirred at 0-5 degreeC for 2 hours. The reaction solution was discharged into 500 parts of ice water, filtered, washed with water,
The obtained solid was added to 100 parts of a 5% aqueous sodium hydroxide solution,
The mixture was heated and stirred at 90 ° C for 2 hours. After cooling, filtration, washing with water,
Dried and expression

[0039]

Embedded image 5 parts of a crude product of the disazo compound represented by

Trisazo step 5 parts of the obtained disazo compound was dissolved in 300 parts of DMF, 10 parts of 35% hydrochloric acid was added, and the mixture was cooled to 0 to 5 ° C.
% 8% aqueous sodium nitrite solution was added dropwise, and the mixture was stirred at the same temperature for 2 hours, and then sulfamic acid was added to obtain a diazotized solution. To this diazotized solution, 2 parts of phenol dissolved in 30 parts of 10% aqueous sodium hydroxide solution was added dropwise, and pH = 7 at 0-5 ° C.
Stir to ~ 9 for 2 hours. The reaction solution was discharged into 500 parts of ice water, filtered, washed with water, dried,

[0041]

[Chemical 17]

4.5 parts of a crude product of the trisazo compound represented by The crude product was dissolved in toluene and separated and purified by column chromatography packed with silica gel. A dye of 1 was obtained.

Measurement of dichroic ratio Next, in a small beaker, a liquid crystal manufactured by Merck Co. (product number ZLI
-1840) 10 parts were added, and No. 1 in Table-1 was further added. 1
0.05 part of the above dye was added and heated to about 80 ° C. to obtain a completely clear solution. Then, after the contents were left to cool, the colored liquid crystal solution was sealed in the liquid crystal display device. This display device showed an orange color when no voltage was applied, and when the voltage was applied, only the electrode part became colorless, showing good contrast.
The dichroic ratio is 13.0 at the maximum absorption wavelength of 469 nm.
Met. A black panel temperature of 63 is obtained by using this display device with a xenon fade meter (manufactured by Suga Test Instruments Co., Ltd.).
When a light resistance test was conducted by irradiating at ± 2 ° C for 100 hours, the decrease in absorbance at the maximum absorption wavelength of 465 nm was only 4%. That is, the light resistance retention rate was 96%, which was a good result.

Example 2 Formula synthesized as in Example 1

[0045]

Embedded image

3 parts of the compound of (1) was dissolved in 60 parts of DMF, 0.8 parts of potassium carbonate and 0.2 part of potassium iodide were added, and the mixture was stirred at 70 ° C. for 1 hour and then n-butyl bromide (1.
5 parts was added, and the mixture was stirred at 80 ° C. for 2 hours. After cooling to room temperature, discharge into 300 parts of water, filter, wash with methanol, wash with water,

[0047]

[Chemical 19]

A crude product of the compound of was obtained. The dichroic ratio of this purified dye (No. 2 in Table-1) has a maximum absorption wavelength of 465n.
It was 16.4 in m. When the light resistance test was conducted in the same manner as in Example 1, the light resistance retention rate was 97%, which was a good result.

Example 3 Synthesis was carried out in the same manner as in Example 1 except that the anisinomethanesulfonic acid was used instead of α-naphthylamine in the disazo step of Example 1, and the formula was used.

[0050]

Embedded image A disazo compound represented by 4.5 parts of this disazo compound was dissolved in 100 parts of DMF, 5 parts of 35% hydrochloric acid was added, and the mixture was stirred at room temperature for 30 minutes and then cooled to 0 to 5 ° C.
8.3 parts of 10% sodium nitrite aqueous solution was added dropwise, and 2 at the same temperature.
After stirring for an hour, sulfamic acid was added to obtain a diazotized solution. N, N-dimethylaniline 1.
5 parts was added, and the mixture was stirred at 0 to 5 ° C for 2 hours. After discharging into 500 parts of water, filtration, washing with water and drying,

[0051]

[Chemical 21]

A crude product of the compound represented by the formula: was obtained. The dichroic ratio of this purified dye (No. 3 in Table 1) was 15.3 at the maximum absorption wavelength of 553 nm. When a light resistance test was conducted in the same manner as in Example 1, the light resistance retention rate was 96.
A good result was obtained. Hereinafter, the dichroic ratio and light retention of the trisazo dye obtained by synthesis and purification according to these methods are shown in Table-1.

Comparative Example 1 Formula

[Chemical formula 22] When the dichroism of the compound represented by 1 was measured in the same manner as in Example 1, the dichroism at the absorption maximum wavelength of 468 nm was 8.6, and the light retention was 84%.

Comparative Example 2 Formula

[Chemical formula 23] When the dichroism of the compound represented by 1 was measured in the same manner as in Example 1, the dichroism at the absorption maximum wavelength of 519 nm was 9.2, and the light retention was 81%.

Comparative Example 3 Formula

[Chemical formula 24] When the dichroism of the compound represented by the above is measured in the same manner as in Example 1, the dichroism is 1 at the absorption maximum wavelength of 511 nm.
Although it was 0.1, the solubility in the liquid crystal was very poor, and it was 0.
It was 2% or less. Therefore, the degree of coloring was less than the practical level, and it was colored only in a very pale color. Further, the light resistance retention was 91%, which was a relatively poor result.

[0056]

The dye according to the present invention has a large dichroic ratio as is clear from Examples and Comparative Examples, and has excellent durability.

[0057]

[Table 1]

[0058]

[Table 2]

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Claims (1)

[Claims] 1. A compound represented by the general formula (1): [Wherein X represents an alkyl group, an alkoxyalkyl group, a phenyl group or a cyclohexyl group which may be substituted at the p-position with an alkyl or alkoxy group, and P is substituted with a halogen atom, a methyl group or a methoxy group. Represents a 1,4-phenylene group or a 1,4-naphthylene group, and Ar is a 1,4-phenylene group or 1,4-phenylene group.
It represents a 4-naphthylene group, and Y ₁ is a hydrogen atom, a methyl group or meth R is an alkyl group, a phenyl group which may be substituted at the p-position with an alkyl group or an alkoxy group, or a cyclohexyl group, R ₁ is a hydrogen atom or a lower alkyl group, and R ₂ is a lower alkyl group or the p-position. Alkyl,
A benzyl group which may be substituted with an alkoxy or phenyl group. ] The dichroic trisazo dye for liquid crystal displays shown by these.