JPH06340879A - Dichroic coloring matter for liquid crystal additive - Google Patents

Abstract

PURPOSE:To obtain a dichroic coloring matter for liquid crystal additive which has a low capability of dyeing a resin film, a high dichroic ratio, and a high durability by producing it from 1,5-dihydroxy-4,8-dinitroanthraquinone. CONSTITUTION:1,5-Dihydroxy-4,8-dinitroanthraquinone of formula I is reacted with a phenyl ether compd. of formula II (wherein R<3> is alkyl; and R<4> is H, halogen, methyl, ethyl, methoxy, or ethoxy) and then with a potassium salt of a thiophenol of formula III (wherein R<1> is alkyl, cycloalkyl, alkoxy, alkylamino, dialkylamino, halogen, or H; and R<2> is H, halogen, methyl, ethyl, methoxy, or ethoxy). Amino groups of the resulting product are alkylated, giving the objective coloring matter expressed by formula IV or V (wherein R<5> is H or alkyl).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel blue dichroic dye added to liquid crystals. In particular, the invention provides a dichroic dye exhibiting high performance for polymer dispersed liquid crystal display (hereinafter abbreviated as PDLC).

[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 liquid crystal display elements currently in use utilize the electro-optical effect of twisted nematic type liquid crystal, and display is made as an essential condition when combined with two polarizing plates. The reality is that they are restricted by. 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, and some of them have already been used for watches and home appliances. , Is used as a display element in industrial instruments and the like.

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, which is usually an electric field, is applied, 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 their alignment direction. Based on the principle that the degree of light absorption by dye molecules in both states changes, and display is performed.

Recently, an element in which this liquid crystal display system is applied to PDLC, that is, a system in which a liquid crystal layer is enclosed in a polymer matrix and sandwiched between plastic sheets with electrodes for display, has been put into practical use. The method of using by adding a dichroic dye in the liquid crystal composition used here,
It has proved to be a very advantageous method for the purpose of increasing the contrast.

[0006] PDLC is a display method which has received a great deal of attention because it has excellent characteristics such as a large area and a light weight, as compared with a conventional device using a glass cell.

[0007]

The dichroic dye used here has sufficient coloring ability with a small amount, exhibits a large contrast, has sufficient compatibility with liquid crystals, and has durability. It is excellent and stable, and does not deteriorate the performance of the device even if it is used for a long time. It requires the same conditions as the conventional dichroic dye for guest-host, but in the case of PDLC, The condition that the resin layer, which is the polymer matrix, is not dyed and colored is added.

The dyed and colored portion remains uncolored because the orientation direction cannot be changed even when a voltage is applied, which causes a reduction in contrast and is a decisive defect in display. Among the compounds that have been developed as blue-based dichroic dyes,
These improvements have been strongly desired because there is no dye capable of satisfying the performance of all of the above conditions.

[0009]

Means for Solving the Problems The inventors of the present invention have made earnest studies in view of such a situation, and as a result, satisfy the conditions (1) to (3) required for a guest-host dichroic dye in PDLC, and improve the durability. We have found a new dichroic dye which is excellent, has a large dichroic ratio, and does not dye the matrix resin layer. That is, the present invention provides a liquid crystal dye of the general formula
(1) (Chemical formula 1)

[0010]

[Chemical 1] Alternatively, the general formula (2)

[0011]

[Chemical 2]

[Wherein R ¹ is an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, an alkoxy group which may have a substituent, or a substituent which has a substituent]. Represents an alkylamino group, a dialkylamino group which may have a substituent, a halogen atom or a hydrogen atom, and R ² and R ⁴ represent a hydrogen atom, a halogen atom, a methyl group, an ethyl group, a methoxy group or an ethoxy group. R ³ may be the same or different, R ³ represents an alkyl group which may have a substituent, and R ⁵ represents a hydrogen atom or an alkyl group which may have a substituent. ] A dichroic dye for liquid crystal addition represented by the following is provided.

The feature of the dichroic dye of the present invention is that a substituted phenyl group is introduced at the 2-position of the anthraquinone skeleton and a substituted phenylthio group is introduced at the 4-position or 8-position,
As a result, the dichroism, durability and colorability of the resin are remarkably improved as compared with similar known anthraquinone type dichroic dyes.

The liquid crystal dye according to the present invention is represented by the general formula (1) or (2), and the general formula (1),
Specific examples of R ¹ in (2) include methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, dodecyl group, isopropyl group, isobutyl group. , Tert-
As a butyl group, a cyclohexyl group, a 3,5-dimethylhexyl group, and an alkoxy group, a methoxy group, an ethoxy group, a propyloxy group, a butyloxy group, a hexyloxy group, a cyclohexyloxy group, an isobutyloxy group,
Examples of the heptyloxy group, dodecyloxy group and halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

Specific examples of R ² and R ⁴ include hydrogen atom, fluorine atom, chlorine atom, bromine atom, iodine atom, methyl group, ethyl group, methoxy group and ethoxy group.

Specific examples of R ³ and R ⁵ are methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, dodecyl group, 3-
Examples thereof include methylhexyl group, 3,5,5-trimethylhexyl group, methoxyethyl group, butoxyethyl group, methoxyethoxyethyl group, hydroxyethyl group and 2-chloroethyl group.

The dichroic dye of the general formula (1) or (2) of the present invention can be easily synthesized by a conventional method.

That is, 1,5-dihydroxy-4,8-dinitroanthraquinone of the general formula (3) (Chemical formula 3) and a phenyl ether compound of the general formula (4) (Chemical formula 4) [in the formula, R
³ and R ⁴ represent the same substituent as R ³ and R ⁴ in the general formula (1) or (2). ] In sulfuric acid in the presence of boric acid at a low temperature to give compounds of the general formulas (5) and (6) (formula 5).

Further, the compounds of the general formulas (5) and (6) are treated with a thiophenol compound of the general formula (7) (formula 6) in a polar organic solvent such as dimethylacetamide, dimethylformamide, dimethylsulfoxide and sulfolane. During,
R ¹ and R ² represents a general formula (8) and (9) (Formula 6) the same substituents as R ¹ and R ² in formula. The compounds of the general formulas (8) and (9) (that is, R ⁵ = H in the compound of the general formula (1) or (2)) can be obtained by reacting with the potassium salt of

[0020]

[Chemical 3]

[0021]

[Chemical 4]

[0022]

[Chemical 5]

[0023]

[Chemical 6]

Further, in order to alkylate the 4- or 8-position amino group, the compounds of the general formulas (8) and (9) are reacted with the corresponding aldehyde and carboxylic acid in water or a water / polar solvent. By making the general formula (1)
And the compounds of (2) can be obtained.

[0025]

[Chemical 7]

The crude dye of the general formula (1) or (2) thus obtained can be purified by recrystallization, column chromatography or the like to obtain a highly pure dye.

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.

The liquid crystal used is, for example, 4-cyano-4'-n-pentylbiphenyl, 4-cyano-4'-.
Cyano-biphenyl liquid crystal such as n-propoxybiphenyl, 4-cyano-4'-n-pentoxybiphenyl, 4-cyano-4'-n-octoxybiphenyl, 4-cyano-4'-n-pentylterphenyl Mixture (for example, Merck's product code E-8) or trans-4
-N-propyl- (4-cyanophenyl) -cyclohexane, trans-4-n-pentyl- (4-cyanophenyl) -cyclohexane, trans-4-n-heptyl- (4-cyanophenyl) -cyclohexane, trans- A cyclohexane-based liquid crystal mixture such as 4-n-pentyl- (4′-cyanobiphenyl) -cyclohexane (for example, product numbers ZLI-1132 and ZLI-18 manufactured by Merck & Co., Inc.).
40) and the like.

Furthermore, in the state in which no electric field is applied, in which an optically active substance such as cholesteryl nonanoate or optically active 4-cyano-4'-isopentylbiphenyl is added to the liquid crystal mixture, it is in a cholesteric phase state and in an electric field applied state. It is also possible to use so-called chiral nematic liquid crystal mixtures which undergo a phase transition to the nematic phase state.

The liquid crystal is not limited to the above examples, but other biphenyl liquid crystals, phenylcyclohexane liquid crystals, Schiff base liquid crystals, ester liquid crystals,
Pyrimidine-based liquid crystals, tetrazine-based liquid crystals, and other liquid crystals can be used alone or as a mixture.

The dye according to the present invention may be used alone or in combination of two or more. The concentration of the dye used is within the limit that the dye dissolves in the liquid crystal,
Moreover, the dye molecules may be within a range in which the alignment of the liquid crystal molecules can be sufficiently controlled by the alignment of the liquid crystal molecules.
It is preferable to use it at a concentration of 1 to 10% by weight, preferably 0.1 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 and use it as a desired hue, without any limitation. The dichroic dye is dissolved in the liquid crystal by mixing a predetermined amount of the dye with the liquid crystal and stirring the mixture for a long time or by heating it to a temperature above the temperature at which the liquid crystal becomes an isotropic liquid. It can be a liquid crystal composition.

[0033]

Various dichroic dyes used in the conventional PDLC have been proposed. However, since the dichroic dye used for dyeing the base resin film layer causes a decrease in contrast and the dichroic ratio is low, It has drawbacks such as not being able to display clearly in practical use and lacking in durability. However, the dichroic dye of the present invention represented by the general formula (1) or (2) has low dyeability to a resin film, has a large dichroic ratio, and has high durability, and therefore, the dye is practically used. It is an extremely valuable pigment.

[0034]

Examples Synthesis examples of the anthraquinone-based dichroic dye of the present invention are shown below, and Table 1 shows typical dye structures, dichroic ratio and maximum absorption wavelength in the liquid crystal E-44 manufactured by Merck. Show.

The dichroic ratio shown in Table 1 is 1.0% by weight for each dye.
Was dissolved in a typical nematic liquid crystal manufactured by Merck & Co. (product number E-44) and sealed in a liquid crystal cell having a thickness of 10 μm which was previously processed for homogeneous alignment. The absorbance (A‖) measured by applying a linearly polarized light parallel to the array and the absorbance (A⊥) measured by applying a linearly polarized light perpendicular to the liquid crystal array,
The following formula (Equation 1)

[0036]

[Equation 1] It is calculated from

All the dichroic dyes of the present invention showed extremely high dichroic ratio and were compounds having no matrix resin dyeing property in PDLC. In addition, "part" in an Example shows a weight part.

Example 1 25.8 parts of boric acid was suspended in 857 parts of 94% sulfuric acid, dissolved by heating, cooled to room temperature, and 1,5-dihydroxy-4,
17.2 parts of 8-dinitroanthraquinone are suspended and stirred at room temperature for 1 hour. The solution is cooled to -8 ° C and n
-22.8 parts of hexyl phenyl ether is added dropwise over 1 hour, and the temperature is kept at the same temperature for 2 hours. The obtained reaction liquid was discharged into 1100 parts of ice water, filtered, washed with water and dried to obtain a mixture 3 of the following formulas (10) and (11)
6.0 parts were obtained.

[0039]

[Chemical 8]

On the other hand, 4.0 parts of 4-tert-butylthiophenol, 1.7 parts of potassium hydroxide and 100 parts of dimethylacetamide (hereinafter abbreviated as DMA) were mixed and heated and dehydrated to 150 ° C. under a nitrogen stream. As a result, a potassium salt of thiophenol is obtained. The reaction solution is cooled to 80 ° C., 11.4 parts of the compounds of the above formulas (10) and (11) are added, and the reaction is carried out for 2 hours. The reaction solution was discharged into 300 parts of water, filtered, washed with water and dried to obtain the following formulas (12) and (1
3) 15.0 parts of a crude mixture of the compound of Chemical formula 9 was obtained. This was dissolved in toluene and separated and purified by column chromatography using a column packed with silica gel to obtain 1.2 parts of pure formula (12) (dye of dye No. 5 in Table 1) and formula (13) (dye no. 6 dyes) was obtained.

[0041]

[Chemical 9]

Next, 1 part of the above dye was added to 100 parts of liquid crystal E-44 (trade name of nematic liquid crystal manufactured by Merck & Co., Inc.) in a small beaker and heated to about 80 ° C. to obtain a completely clear solution. Then, after the contents were left to cool, the colored liquid crystal was sealed in the liquid crystal display element under reduced pressure. This display device showed a red color when no voltage was applied, and when the voltage was applied, only the electrode portions became colorless, showing good contrast. Further, the dichroic ratio of the dye of dye No. 5 in Table 1 is 630 nm at the maximum absorption wavelength.
Was 11.8, and the dye of Dye No. 6 in Table 1 was 13.4 at the maximum absorption wavelength of 627 nm.

Further, when light irradiation was carried out for 200 hours using a sunshine weather meter, no change was observed in either case and good light resistance was exhibited.

Liquid crystal E-4 in which 2% of this dye is dissolved
4 (Merck nematic liquid crystal brand name) 40 parts, water 16
Part, 3.7 parts of PVA 20/30 (trade name of Airco),
Gantres 169 (polymethyl vinyl ether / maleic anhydride copolymer manufactured by GAF) (0.2 parts) and glycerin (0.1 parts) were mixed and vigorously stirred with a homogenizer to form an emulsion.

The produced emulsion was previously mixed with indium
A tin oxide (ITO) vapor-deposited Mylar film is coated to a thickness of 0.5 mm. The film thus obtained was placed on another Mylar film coated with ITO, and 10
It was left in a dryer at 0 ° C. for 1 hour. Furthermore, after cooling to room temperature, activation with a direct current voltage of 100 V gave an opaque blue liquid crystal film.

When an alternating voltage of 60 Hz and 100 V was applied to this liquid crystal film, it changed from blue to colorless and good contrast was obtained. In addition, this film display board 2
After leaving it for a week at room temperature, it was placed in acetone, the liquid crystal layer was extracted, and the dyeability of the resin with the dye was examined only with the matrix resin film. No coloring was observed at all, and good results were shown.

Example 2 2.5 parts of the crude product of the formulas (12) and (13) obtained in Example 1 were added with 27.9 parts formic acid, 2.1 parts water and 11.0 parts 37% formalin. Mix, heat to 80 ° C., react at the same temperature for 2 hours, then cool to room temperature. The precipitate is filtered, washed with water and dried to obtain the following formulas (14) and (15)
2.4 parts of a crude mixture of the above compounds are obtained. This was purified by column chromatography in the same manner as in Example 1 to obtain 1.1 parts of dye No. 51 and 1.4 parts of dye No. 52 in Table 4.

[0048]

[Chemical 10] Regarding the dichroic ratio of these purified dyes, the dye of dye No. 51 in Table 4 showed 9.0 at the maximum absorption wavelength of 655 nm, and the dye of dye No. 52 in Table 4 had 10.2 at 654 nm.
showed that. In a 200-hour light resistance test with a sunshine weather meter, no deterioration in performance was observed and good results were shown. Further, the resin film also showed good contrast, and the resin was not dyed.

Example 3 Instead of n-hexylphenyl ether of Example 1, n was used.
With hexyl (2-methylphenyl) ether,
The same operation as in Example 1 was performed to obtain the following equations (16) and (1
7) (Dye Nos. 7 and 8 in Table 1) were obtained.

[0050]

[Chemical 11]

The dichroic ratio of these purified dyes is dye No. 7
The dye of No. 8 showed 11.5 at the maximum absorption wavelength of 629 nm, and the dye of dye No. 8 showed 13.0 at the maximum absorption wavelength of 626 nm. In a 200-hour light resistance test with a sunshine weather meter, no deterioration in performance was observed and good results were shown. Further, PDLC showed good contrast and no coloring was observed.

Example 4 4-n-hexyloxythiophenol was used in place of 4-tert-butylthiophenol of Example 1,
The same operation as in Example 1 is performed to obtain the following equations (18) and (1
9) The dye of Chemical formula 12 was obtained (dyes of dye numbers 31 and 32 in Table 2).

[0053]

[Chemical 12]

The dichroic ratio of these purified dyes is dye No. 3
The dye of No. 1 showed 13.8 at the maximum absorption wavelength of 632 nm, and the dye of No. 32 showed 11.9 at the maximum absorption wavelength of 629 nm. In a 200-hour light resistance test with a sunshine weather meter, no deterioration in performance was observed and good results were shown. Further PD
LC also showed good contrast and no dyeing property was observed.

Example 5 The procedure of Example 1 was repeated using acetic acid instead of formic acid and acetaldehyde instead of formalin, and the dyes of the following formulas (20) and (21) (formula 13) were used. Was obtained (dye numbers 55 and 56 in Table 4).

[0056]

[Chemical 13]

The dichroic ratio of these purified dyes is dye No. 5
The dye of 5 showed 8.8 at the maximum absorption wavelength of 657 nm, and the dye of dye No. 56 showed 9.9 at the maximum absorption wavelength of 654 nm. In a 200-hour light resistance test with a sunshine weather meter, no deterioration in performance was observed and good results were shown. Further PDLC
Also showed good contrast and no coloring was observed.

The dichroic ratios of the dyes synthesized and purified according to these methods are shown in Tables 1 to 4 below.

Tables 1 to 4 also show the results obtained by measuring the matrix resin dyeing properties in PDLC in the same manner as in Example 1. The positions of the substituents in the table are shown according to the following general formula (13) (Chemical Formula 13).

[0060]

[Chemical 14]

[0061]

[Table 1]

[0062]

[Table 2]

[0063]

[Table 3]

[0064]

[Table 4]

Claims (1)

[Claims] 1. The general formula (1) Or the general formula (2) [In the formula, R ¹ is an alkyl group which may have a substituent, a cycloalkyl group which may have a substituent, an alkoxy group which may have a substituent, and an alkyl which may have a substituent. An amino group, a dialkylamino group which may have a substituent, a halogen atom or a hydrogen atom, R ² and R ⁴ represent a hydrogen atom, a halogen atom, a methyl group, an ethyl group, a methoxy group or an ethoxy group, and R ³ may be the same or different and R ³ represents an alkyl group which may have a substituent, and R ⁵ represents a hydrogen atom or an alkyl group which may have a substituent. ] The dichroic dye for liquid crystal addition represented by.