JPH0662868B2 - Dichroic trisazo dye for liquid crystal display - Google Patents

Description

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

[Problems to be Solved by Prior Art and Invention]

In recent years, liquid crystal display devices have been widely used from the viewpoint of energy saving and miniaturization. Most of the liquid crystal display elements currently in use 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, a 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. It has begun to be used as a display element in products and industrial instruments.

The principle of this guest-host liquid crystal display system is that the dichroic dye molecules that are guests are oriented and arranged according to the arrangement of the liquid crystal molecules that 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, the degree of light absorption by the dye molecules in both states changes, and it is based on the principle that display is performed.

The dichroic dye used here has a sufficient coloring ability even in a small amount, has a large dichroic ratio, exhibits a large contrast when no voltage is applied, and has a sufficient compatibility with liquid crystals. Basically, it is necessary to have conditions such as possession, excellent durability, stability, and not deteriorating the performance of the device even when used for a long time.

Various dichroic dyes have been proposed to meet the above conditions, and some have already begun to be used in digital locks, meters, etc., but those exhibiting a large dichroic ratio have poor durability. At present, many of them have drawbacks to be improved, such as excellent durability but not having dichroism for practically clear display.

[Means for solving problems]

As a result of intensive studies in view of such circumstances, the present inventors have found a new dichroic dye having a large dichroic ratio and excellent durability.

The dye for liquid crystal display of the present invention is a triphenylazo dye having 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 bonded to the biphenyl skeleton. The dichroic dye according to the present invention is characterized by having the general formula (I) [In the formula, X represents an alkyl group, an alkoxyalkyl group, a phenyl group which may be substituted at the p-position with an alkyl or alkoxy group, or a cyclohexyl group, and Ar represents a 1,4-phenylene group or a 1,4-naphthylene group. Represents, Y ₁ , Y ₂ and Y ₃ represent a hydrogen atom, a methyl group or a methoxy group, Z represents a hydroxyl group, an alkoxy group, R is an alkyl group, a phenyl or cyclohexyl group which may be substituted at the p-position with an alkyl group or an alkoxy 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 a dichroic trisazo dye for liquid crystal display shown by these.

Specific examples of X in the general formula (I) for a liquid crystal dye according to the present invention include: And a group 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.

Specific examples of Y ₁ , Y ₂ and Y ₃ include —H, —Cl,
-Br, -I, -F, -CN, -OH, -OCH 3, -
Although CH _{3 and the} like can be mentioned, when Y ₁ , Y ₂ and Y ₃ are all hydrogen atoms, the dichroic effect is large, and it is advantageous from the viewpoint of the purity of the reaction product and the production cost of the raw materials, which is preferable.

Further, as a specific example of Z, And a group 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 (II) [In the formula, X has the same meaning as in formula (I). ] After the diazotization of the compound represented by the general method, the general formula (III) [In the formula, Y ₁ has the same meaning as in formula (I). ] The compound of the general formula (IV) [In the formula, X and Y ₁ have the same meanings as in formula (I). ] The monoazo compound represented by this is obtained. Alternatively, the diazotized compound of the general formula (II) can be converted to the general formula (V) [In the formula, Y ₁ has the same meaning as in formula (I). ] The compound represented by the general formula (I
The monoazo compound of V) is obtained.

Next, the compound of the general formula (IV) is diazotized to give the general formula (VI) or the general formula (VI) [In the formula, Y ₂ and Y ₃ have the same meanings as in formula (I). ] Further coupling with a methanesulfonate salt of the general formula (VII) which is a precursor of the general formula (I) of the present invention [In the formula, X, Y ₁ , Y ₂ and Y ₃ have the same meanings as in formula (I). ] The disazo compound represented by these is obtained.

Then, these disazo compounds are further diazotized to give a compound represented by the general formula (VIII) [In the formula, Z'represents a hydroxyl group, an amino group or a dialkylamino group, and Y ₁ has the same meaning as in the general formula (I). ] The trisazo compound of the general formula (I) can be obtained by coupling with a compound represented by

When Z'is a hydroxyl group, Z'can be converted into a substituent corresponding to Z in the compound of the general formula (I) by subsequently reacting with a desired alkylating agent or acylating agent after completion of coupling. .

Thus, the trisazo dye general formula (I) of the present invention can be synthesized by appropriately selecting the coupling component from the compound of the general formula (II) as a raw material.

X in the general formula (I) is 4'-aminobiphenyl-
It is also possible to synthesize the trisazo compound using 4-carboxylic acid as a starting material and then introduce the trisazo compound by a conventional esterification.

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 (product number E-8 manufactured by Merck, etc.), phenylcyclohexane liquid crystal (product number ZLI-1 manufactured by Merck) are used.
132, ZLI-1840, etc.), Schiff-based liquid crystals, ester-based liquid crystals, pyrimidine-based liquid crystals, tetrazine-based liquid crystals, and other nematic liquid crystals exhibiting positive or negative dielectric anisotropy, and these may be used alone or in combination. . Further, a so-called phase transition type liquid crystal in which an optically active substance such as cholesteryl nonanoate or optically active 4-cyano-4'-isopentylbiphenyl is added to these nematic liquid crystals 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 dye concentration used is
The dye may be dissolved in the liquid crystal, and the dye molecules may be sufficiently aligned and controlled by the alignment of the liquid crystal molecules. Generally, the concentration of 0.01 to 10% by weight based on the liquid crystal, It is preferably used at a concentration of 0.01 to 5% by weight.

Further, the dichroic dye according to the present invention and another dichroic dye, or
It is also possible to mix with a dye having no dichroism as a desired hue and is not limited at all, the dissolution of the dichroic dye in the liquid crystal, mixing a desired amount of the dye with the liquid crystal and stirring for a long time, Alternatively, the liquid crystal composition can be formed into a desired liquid crystal composition for color display by stirring the liquid crystal only at a temperature higher than a temperature at which the liquid crystal becomes an isotropic liquid.

〔Example〕

Hereinafter, typical examples of the dichroic dye of the present invention will be specifically described 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 obtained by dissolving 0.5% by weight of each dye in a liquid crystal (product number ZLI-1840) manufactured by Merck Co., which is a typical nematic liquid crystal, and processed so as to be homogeneously aligned in advance. After enclosing it in a liquid crystal cell of 10 μm in length, it was placed in the optical path of the spectrophotometer and the linearly polarized light parallel to the liquid crystal array was applied to measure the absorbance (A _‖ ) at the maximum absorption wavelength and the linearly polarized light perpendicular to the liquid crystal array. The absorbance (A _⊥ ) at the same wavelength measured by It is calculated from

Parts indicate parts by weight, and% indicates% by weight.

Example 1 Monoazo process formula After dissolving 7 parts of the compound represented by the above in 400 parts of N, N-dimethylformamide (hereinafter abbreviated as DMF), 20 parts of 35% hydrochloric acid was added, cooled to 5 ° C. or lower, and 25 parts of 10% sodium nitrite aqueous solution was added. After dropwise addition and stirring at the same temperature for 2 hours, sulfamic acid was added to obtain a diazotized solution. The pH of this diazotized solution was adjusted to pH 4, 4.2 parts of α-naphthylamine was added, and the mixture was stirred at 0 to 5 ° C for 2 hours. The reaction solution is ice water 100
It was discharged to 0 parts and filtered. The cake obtained was dispersed in water 1, stirred at 85 to 90 ° C. for 8 hours, filtered, washed with water and dried, 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.
Add 2 parts of aniline methanesulfonic acid to this diazotized solution
What was melt | dissolved in F10 part was dripped, and it stirred at 0-5 degreeC for 2 hours. The reaction liquid was discharged into 500 parts of ice water, filtered and washed with water, and the obtained solid was added to 100 parts of a 5% aqueous sodium hydroxide solution, and the mixture was heated with stirring at 90 ° C. for 2 hours. After cooling, filtration, washing with water and drying, 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.
It was stirred at 9 for 2 hours. Discharge the reaction solution to 500 parts of ice water,
Filtered, washed with water, dried, 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 medium NO. 1 dye was obtained.

Dichroic ratio measurement Next, in a small beaker, Merck liquid crystal (product number ZLI
-1840) 10 parts, and further, 0.05 part of the dye of No. 1 in Table 1 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 was 13.0 at the maximum absorption wavelength of 469 nm.

This display device was irradiated with a xenon fade meter (manufactured by Suga Test Instruments Co., Ltd.) at a black panel temperature of 63 ± 2 ° C. for 100 hours, and a light resistance test was conducted. As a result, the absorbance at the absorption maximum wavelength of 465 nm decreased. Was only 4%. That is, the light resistance retention rate was 96%, which was a good result.

Example 2 Formula synthesized in the same manner as in Example 1 3 parts of the above compound is dissolved in 60 parts of DMF, 0.8 parts of potassium carbonate and 0.2 parts of potassium iodide are added, and after stirring at 70 ° C. for 1 hour, 1.5 parts of n-butyl bromide is added,
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, A crude product of the above compound was obtained.

The dichroic ratio of this purified dye (NO. 2 in Table 1) was 16.4 at the maximum absorption wavelength of 465 nm.

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 performed in the same manner as in Example 1 and the formula 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 after stirring at room temperature for 30 minutes,
After cooling to 0 to 5 ° C., 8.3 parts of a 10% sodium nitrite aqueous solution was added dropwise, and after stirring at the same temperature for 2 hours, 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, A crude product of the compound represented by

The dichroic ratio of this purified dye (NO. 3 in Table 1) was 15.3 at the maximum absorption wavelength of 553 nm.

When the light resistance test was conducted in the same manner as in Example 1, the light resistance retention rate was 96%, which was a good result.

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 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 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 The dichroism of the compound represented by the formula (1) was measured in the same manner as in Example 1.
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.

Continuation of the front page (56) Reference JP-A-59-47261 (JP, A) JP-A-58-84858 (JP, A) JP-A-59-4674 (JP, A)

Claims (1)

[Claims] 1. A general formula (I) [In the formula, X represents an alkyl group, an alkoxyalkyl group, a phenyl group which may be substituted at the p-position with an alkyl or alkoxy group, or a cyclohexyl group, and Ar represents a 1,4-phenylene group or a 1,4-naphthylene group. Represents, Y ₁ , Y ₂ and Y ₃ represent a hydrogen atom, a methyl group or a methoxy group, Z represents a hydroxyl group, an alkoxy group, R is an alkyl group, a phenyl or cyclohexyl group which may be substituted at the p-position with an alkyl group or an alkoxy 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 display shown by these.