JPH0813932B2 - Water-soluble azo dye and polarizing film containing the same - Google Patents

Description

TECHNICAL FIELD The present invention relates to an azo dye which is useful as a dichroic dye for a polyvinyl alcohol-based polarizing film, and a polarizing film containing the dye, in addition to dyeing various kinds of fabrics and papers.

2. Description of the Related Art Conventionally, iodine has been used as a dichroic dye for a polyvinyl alcohol-based polarizing film, and has a characteristic of exhibiting a high polarization rate. On the other hand, the durability of the polarizing film is poor due to high volatility of iodine. There is. For this reason, polarizing films using synthetic dyes have been manufactured, but there are still many problems in the polarization ratio, fastness and the like.

Problems to be Solved by the Invention Synthetic dyes used in a potavinyl alcohol-based polarizing film are often diverted from existing fibers, so that the polarization ratio is considerably lower than that of iodine-based ones and their applications are limited. Therefore, the development of a dye showing a polarization rate similar to that of iodine is desired.

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, the formula (1) was obtained as a free acid. [In the formula (1), X is 2-carboxyvinyl group or 4-sulfophenylazo group, R ₁ is H, methyl group, methoxy group, ethoxy group or acetylamino group, and R ₂ is H, methyl group, methoxy group. R ₃ represents a group or an ethoxy group, and R ₃ represents an amino group, a methylamino group, an ethylamino group, an acetylamino group, a benzoylamino group, a phenylamino group or a 4-carboxyphenylamino group, respectively. Note that
R ₃ is bound to the 6- or 7-position of the naphthalene ring] or a water-soluble dye represented by this or a copper complex salt dye thereof is excellent in fastness such as heat resistance and light resistance and, in particular, has a polarization ratio. The present invention has been completed by finding that it is excellent. That is, the present invention provides a water-soluble dye represented by the above formula (1) or a copper complex salt dye thereof as a free acid and a polarizing film containing the same.

 The present invention will be described in detail.

The water-soluble dye of the formula (1) can be easily produced by a known diazotization and coupling method according to a usual method for producing an azo dye.

That is, 4-aminocinnamic acid or 4-aminoazobenzene-4'-sulfonic acid is diazotized to give p-cresidine, 2,5
-Dimethoxyaniline, 2,5-diethoxyaniline, m
-Toluidine, 2,5-xylidine, m-acetylaminoaniline, m-acetylamino-o-anisidine and the like are coupled by a conventional method to produce an aminoazo compound having an amino group as an intermediate. In this case, when coupling to aniline or m-anisidine, the amino group is changed to an ω-methanesulfonic acid derivative once, then coupled, and then hydrolyzed with an alkali to obtain an amino group-containing azo compound.

In the above, the diazotization method is a normal method in which a diazo component such as hydrochloric acid, a sulfuric acid or other aqueous mineral acid solution or a suspension is mixed with a nitrite such as sodium nitrite, or a diazo component is neutral or weakly alkaline. The reverse method of adding nitrite and mixing this with a mineral acid may be used. An appropriate temperature for the diazotization is -10 to 40 ° C.

The coupling may be carried out by mixing an acidic aqueous solution of amines such as hydrochloric acid and acetic acid with the above diazo solution and neutralizing them to adjust the pH to 3-5. A suitable coupling temperature is -10 to 40 ° C.

The aminoazo compound thus formed is usually precipitated under these conditions, so that it can be taken out over time, or if desired, the suspension can proceed to the next diazo step.

If the diazonium salt is sparingly soluble and becomes a suspension, it can be overused as a press cake in the next diazo step.

The intermediate aminoazo compound thus obtained was diazotized to obtain J-acid, γ-acid, N-methyl J acid, N-ethyl J
Acid, N-methyl gamma acid, N-acetyl J acid, N-acetyl gamma acid, N-benzoyl J acid, N-phenyl J acid, N-
The water-soluble dye of the formula (1) is obtained by alkaline coupling with (4-carboxyphenyl) J acid, N-phenylγ acid and the like.

In the above, the diazotization method may be the above-mentioned normal method, but the reverse method is preferable when the solubility of the aminoazo compound is extremely small when the aminoazo compound is acidic. The diazotization temperature is between 0 and
40 ° C is appropriate. The diazo liquid is a suspension, which can be used as it is or can be used to remove the diazonium salt press cake.

For coupling, a small amount of the suspension or diazonium salt of the diazonium salt is added to the aqueous alkali solution of the coupling component. At this time, an alkali is added as necessary so that the solution maintains pH 8 to 11. As the alkali, it is preferable to use carbonates such as sodium, potassium and lithium, and amines such as ammonia, mono, di and triethanolamine. In addition to this, hydroxides or bicarbonates such as sodium and potassium may be used in combination. Good. If necessary, a usual coupling accelerator such as pyridine or urea may be added.

A suitable coupling temperature is -10 to 40 ° C. After completion of the coupling, if necessary, sodium chloride and / or potassium chloride are added, and salted out and taken out.

Further, in order to obtain the copper complex salt of the water-soluble dye of the formula (1), a usual method may be used. That is, the water-soluble dye of the formula (1) is mixed with a copper salt such as copper sulfate, copper chloride, copper acetate or the like in an aqueous solution usually at 70 to 110.
Heat to ° C. At this time, if necessary, an organic amine such as ammonia, monoethanolamine, diethanolamine, monopropanolamine, or pyridine can be added.

As a substrate for preparing the polarizing film of the present invention, a fibrin resin (cellophane), PVA, modified PVA, a copolymer of PVA and another resin, or the like is used. Of these, preferred are PVA, modified PVA, copolymers of PVA with other resins, and the like, and these are hereinafter referred to as PVA-based substrates. As a PVA-based substrate, in addition to ordinary pure PVA, an unsaturated carboxylic acid or a derivative thereof, an unsaturated sulfonic acid or a derivative thereof, an α-olefin having 2 to 30 carbon atoms, and the like are copolymerized and modified with less than about 15 mol%. And polyvinyl acetal such as modified polyvinyl alcohol, polyvinyl formal, polyvinyl acetoacetal and polyvinyl butyral, and saponified ethylene-vinyl acetate copolymer having an ethylene content of 15 to 55 mol%. Examples of the method for producing a polarizing film from these substrates include a method of dyeing a molded PVA-based film itself, a method of adding a dye to a solution of a PVA-based resin, and a method of forming a film after dyeing an undiluted solution. . First, a general dyeing method and a stretching method for a PVA-based film will be described.

In a dye bath containing a water-soluble dye of the formula (1) or a copper complex thereof and, if necessary, a dyeing aid such as an inorganic salt or a surfactant, a PVA system is used at 0 to 70 ° C, preferably 30 to 45 ° C. Dipping and dyeing the film, then optionally boric acid treatment,
dry. In order to impart a polarizing function to the dyed film, it is stretched uniaxially by 2 times or more, particularly preferably 2.5 to 4 times before dyeing, after dyeing or during dyeing. In the case of stretching before or after dyeing, in addition to wet stretching, it may be performed under dry conditions (usually in the range of room temperature to 180 ° C.). Is stretched at 30 to 45 ° C.

Next, in the method of forming a film after dyeing the undiluted solution, first, a PVA-based substrate (resin) is dissolved in a solvent such as water, an organic solvent, or a water-alcohol mixed solvent, and a water-soluble dye of the formula (1) or a copper complex salt dye thereof Is added and stock solution staining is performed. The dyeing stock solution is formed into a film by a casting method, a solution coating method, an extrusion method, or the like, to produce a dyed film. In order to impart a polarizing function to the dyed film thus obtained, the dyed film is uniaxially stretched under the same wet or dry conditions as described above.

Here, the uniaxial stretching means that the film is completely stretched only in the uniaxial direction (free-width uniaxial stretching), and that the film is slightly stretched in a direction perpendicular to the stretching direction to prevent shrinkage in the width direction (uniaxial stretching with a constant width). Stretching).

As a method for dyeing a film, dyeing by immersion or dyeing by undiluted solution as described above is common.However, a method of preparing a printing paste, printing this on a film, heating and dyeing by internal diffusion is used. Can also be adopted.

The water-soluble dye represented by the formula (1) or its copper complex salt dye can be used alone or in admixture thereof, and further, various hues can be obtained by blending these dyes with other dyes. It is possible to manufacture a polarizing film having a high polarization rate, which is dyed with. In particular, when a water-soluble dye represented by formula (1) or its copper complex salt dye is used as a compounding component for gray or black which is frequently used, a polarizing film having excellent polarizing ability and preferable absorption characteristics can be obtained. Also, its heat stability is excellent.

The polarizing film produced in this way is used as it is, and especially in the field where high durability is required, a supporting film such as polyester, vinyl chloride, cellulose triacetate, acrylic resin, polyether sulfone, etc. It can be used as a polarizing plate having a high polarization rate and high durability by coating with an acrylic resin or the like.

In recent years, new types of liquid crystal displays that use the birefringence of liquid crystals, that is, super twist type (having a larger twist angle than conventional twist nematic) and ferroelectric liquid crystal type liquid crystal displays have appeared. Has come.
When a conventional iodine-based polarizing plate is used for these birefringent liquid crystal displays, the entire screen is colored yellow or purple, and the display quality is deteriorated. However, the polarizing plate of the present invention is a color polarizing plate that corrects it. Excellent as a board.

Examples The present invention will be described below with reference to specific examples. In the examples
Parts indicate parts by weight.

Example 1. 29.9 parts (1/10 mol) of sodium 4-aminoazobenzene-4'-sulfonate were dissolved in 300 parts of water, and 25 parts of concentrated hydrochloric acid and 6.9 parts of sodium nitrite were added to diazotize. After 13.7 parts of cresidine was dissolved in an aqueous hydrochloric acid solution, sodium acetate was added to neutralize the mixture to pH 4 for coupling. After completion of the reaction, filtration was performed to obtain a presscake containing 41.5 parts of the disazo compound represented by the following formula (2).

This press cake is dissolved in 1000 parts of water by neutralizing with sodium hydroxide, and a solution obtained by adding 8 parts of sodium nitrite thereto is added dropwise to 200 parts of a 10% hydrochloric acid solution at about 20 ° C. to obtain a diazo compound. It has become. After completion of the diazotization, excess nitrous acid was decomposed by adding sulfamic acid, and the suspension of this diazonium salt was mixed with 31.5 parts of N-phenyl J acid and a 10% sodium carbonate aqueous solution.
The solution was added dropwise to 600 parts at about 20 ° C. for coupling. After stirring for 2 hours, 90 parts of sodium chloride was added for salting out, the mixture was stirred overnight, filtered, washed with a 5% aqueous sodium chloride solution, and dried to obtain 70 parts of the trisazo dye represented by the following formula (3).

A 0.3 g / l dye bath of this trisazo dye was prepared and kept at 40 ° C., and a polyvinyl alcohol film having a thickness of 75 μ was dipped and dyed for 2 minutes. The wet dyed film is stretched 4 times in a 5% aqueous solution of boric acid at 40 ° C. and washed in this state with water.
It was dried to produce a blue-violet polarizing film. As a result of measuring the polarization ratio ρ (max) at the absorption maximum λmax of the polarizing film, the single plate transmittance is 43%, λmax is 580 nm, and ρ (max) is 97.5.
%Met.

Here, the polarization ratio ρ (max) at the absorption maximum wavelength λmax is the parallel transmittance T _‖ (max) and the orthogonal transmittance T _⊥ at that wavelength.
It is expressed by the following equation using (max).

C. which is known as a blue-violet dye for polarizing films for comparison.
Using I.Direct Violet 9 (Structure below) When the polarizing film was prepared in the same manner as described above, λmax was 575 nm, and ρ (max) was 92.5% when the transmittance of the single plate was 43%, and the dye of the present invention was superior.

Further, the magnitude of thermal discoloration during the production of the polarizing film was measured by the following method. That is, two polarizing films dyed with the dye of the formula (3) and stretched were prepared, one of which was air-dried, and the other was dried in a hot air drier at 80 ° C. for 10 minutes to measure the color difference between them. The color was measured using a C light source by the L ^* , a ^* , b ^* measuring method, and the color difference (ΔE) was calculated from the following formula.

Here, Δa ^* and Δb ^* are the difference between a ^* and b ^* between the two materials and L ₁
^* Is the lightness, a ^* is the red line direction, and b ^* is the numerical value showing the yellow-blue hue.

When the dye of formula (3) is used, when the transmittance is 43%, ΔE
Was 1.1. In CI Direct Violet 9 for comparison, it was found that the dye of the present invention was superior to 2.0 in CI Direct Violet 9.

Example 2 In place of N-phenyl J acid in Example 1, 25.3 parts of N-methyl J acid or 34.3 parts of N-benzoyl J acid were used and represented by formulas (4) and (5), respectively. A trisazo dye was obtained.

A polyvinyl alcohol film was treated with an aqueous solution of these trisazo dyes in the same manner as in Example 1 to produce a polarizing film. The dye of formula (4) is blue-violet and has a transmittance of 43% on a single plate.
, The maximum absorption wavelength is 575 nm and the polarization rate at this time is 96.0
%Met. The dye of the formula (5) was ruby red, the maximum absorption wavelength was 555 nm, and the polarization rate was 96.5%.

Example 3. 16.3 parts (1/10 mol) of 4-aminocinnamic acid was dissolved in 600 parts of water together with 4 parts of sodium hydroxide, and 22 parts of concentrated hydrochloric acid and 6.9 parts of sodium nitrite were added to diazotize. Into this p-
A solution prepared by dissolving 13.7 parts of cresidine in 10 parts of methanol was added, and then sodium acetate was added to neutralize to pH 4 for coupling. After completion of the reaction, filtration was performed to obtain a presscake containing 30 parts of the monoazo compound represented by the following formula (6).

The press cake was neutralized and dissolved in 1000 parts of water with sodium hydroxide. A solution prepared by adding 8 parts of sodium nitrite thereto was added dropwise to 200 parts of a 10% hydrochloric acid solution at about 20 ° C to diazotize. After completion of the diazotization, excess nitrous acid was decomposed by adding sulfamic acid and then filtered to obtain a press cake of a diazonium salt. A solution prepared by suspending 600 parts of this diazonium salt in water was added with 23.9 parts of J acid and a 10% sodium carbonate aqueous solution.
The solution was added dropwise to 300 parts of the solution at about 20 ° C. for coupling. After stirring for 2 hours, 90 parts of sodium chloride was added for salting out, the mixture was stirred overnight, filtered, washed with a 10% aqueous sodium chloride solution and dried to obtain 55 parts of a disazo dye represented by the following formula (7).

A polyvinyl alcohol film was treated with the aqueous solution of this disazo dye in the same manner as in Example 1 to produce a reddish purple polarizing film. When the transmittance of the single plate was 43%, the maximum absorption wavelength was 570 nm and the polarization rate was 95.5%.

Example 4 Instead of J acid in Example 3, 23.9 parts of gamma acid or N
The same operation was carried out using 32.5 parts of phenyl J acid to obtain the disazo dyes represented by the formulas (8) and (9), respectively.

A polyvinyl alcohol film was treated with an aqueous solution of these disazo dyes in the same manner as in Example 1 to produce a polarizing film. When the dye of formula (8) was gray and had a single-plate transmittance of 43%, the maximum absorption wavelength was 595 nm and the polarization rate was 94.0%. The dye of formula (9) is purple-blue and has a maximum absorption wavelength of 585n.
In m, the polarization rate at this time was 97.0%.

When the color change of this polarizing film was measured in the same manner as in Example 1, a value of ΔE = 1.2 was shown.

Example 5. Dyes of the general formula (1) shown in the following table were produced in the same manner as in Examples 1 to 4.

In the table, X ₁ and X ₂ represent 4-carboxyvinyl group and 4-sulfophenylazo group, respectively, and hue and λmax are those when dyed on a polyvinyl alcohol film.

Example 6. 70 parts of the dye of formula (9) described in Example 4 above was dissolved in 1000 parts of water, 70 parts of concentrated ammonia water was added, and then an aqueous solution of 24 parts of crystalline copper sulfate was added and heated at 90 ° C. for 3 hours. . Add 60 parts of sodium chloride, cool and salt out, stir overnight, then filter.
% Sodium chloride aqueous solution and dried to obtain 71 parts of the trisazo dye represented by the following formula (31).

A polyvinyl alcohol film was treated with the aqueous solution of the trisazo dye in the same manner as in Example 1 to produce a blue polarizing film. If the single plate transmittance is 43%, the maximum absorption wavelength is 60.
At 5 nm, the polarization rate was 95.1%.

Example 7 The copper complex salt dyes shown in the following table were produced in the same manner as in Example 6 using the dyes of the above formulas as raw materials.

Both the hue and λmax are obtained by dyeing a polyvinyl alcohol film.

EFFECTS OF THE INVENTION A water-soluble dis (or tris) azo dye which can be used for dyeing a Poval film to give a polarizing film having a high polarization rate and a high thermal stability is obtained. This polarizing film has excellent optical characteristics as a blue-violet type polarizing film.

Claims (2)

[Claims] 1. A free acid of the formula (1) [In the formula (1), X represents a 2-carboxyvinyl group or a 4-sulfophenylazo group, R ₁ represents H, a methyl group, a methoxy group, an ethoxy group or an acetylamino group, and R ₂ represents H, a methyl group, A methoxy group or an ethoxy group, and R ₃ represents an amino group, a methylamino group, an ethylamino group, an acetylamino group, a benzoylamino group, a phenylamino group or a 4-carboxyphenylamino group, respectively. Note that
R ₃ is bonded to the 6- or 7-position of the naphthalene ring] or a water-soluble dye or a copper complex salt dye thereof 2. A polarizing film containing a water-soluble dye of formula (1) according to claim 1 or a copper complex dye thereof.