JPH0312606A - Water soluble azo dye and polarizing film containing this dye - Google Patents

Abstract

PURPOSE:To obtain a high polarization factor and thermal stability by using a specific water soluble dye or the copper complex salt dye thereof as a free acid. CONSTITUTION:The water soluble dye expressed by formula I or the copper complex dye thereof is used as the free acid. In the formula I, A denotes a benzene ring or naphthalene ring which may have a methyl group; R denotes an amino group, methyl amino group, ethyl amino group or phenyl amino group, respectively. Such water soluble dye is easily produced by a known diazotization and coupling method in compliance with the process for producing ordinary dyes. The water soluble trisazo dye which yields the polarizing film having the high polarization factor and high thermal stability is obtd. in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Use The present invention relates to an azo dye which is useful as a dichroic dye for polyvinyl alcohol-based polarizing films, in addition to dyeing various textiles and papers, and to polarizing films containing the same.

Conventional technology Conventionally, iodine has been used as a dichroic dye for polyvinyl alcohol-based polarizing films, and although it has the characteristic of exhibiting a high polarization rate, the problem is that the durability of the polarizing film is poor due to the volatility of iodine. There is. For this reason, polarizing films using synthetic dyes have been manufactured, but there are still many problems with their polarization rate, fastness, etc.

Problems to be Solved by the Invention Synthetic dyes used in polyvinyl alcohol-based polarizing films are often repurposed from existing textile dyes, so their polarization ratio is considerably lower than that of iodine-based dyes, and their uses are limited. Therefore, it is desired to develop a dye that exhibits a polarization ratio comparable to that of iodine.

Means for Solving the Problems The present inventors conducted intensive studies to solve the above-mentioned problems, and as a result, as a free acid, the formula (1) [In formula (1), A is a benzene ring that may have a methyl group or In the naphthalene ring, R represents an amine group, a methylamine group, an ethylamino group or a phenylamino group, respectively. ] The water-soluble dye represented by or this copper complex dye has heat resistance,
The present invention was completed by discovering that it has excellent fastness such as light resistance and is particularly excellent in polarization rate. That is, the present invention provides a water-soluble dye represented by the above formula (1) as a free acid or a copper complex dye thereof, and a polarizing film containing the same.

The present invention will be described in detail.

The water-soluble dye of formula (1) can be easily produced by a known diazotization and coupling method in accordance with a conventional azo dye production method.

Namely, sulfanilic acid, metanilic acid, 2-methylaniline-4-sulfonic acid, aniline-2,4-disulfonic acid,
Aniline-2,5-disulfonic acid, naphthionic acid, 2-
Naphthylamine-6-sulfonic acid, 2-naphthylamine-4,8-disulfonic acid, 2-naphthylamine-3,6
-Disulfonic acid, 2-naphthylamine-5,7-disulfonic acid, 2-naphthylamine-6,8-disulfonic acid, etc. are diazotized and coupled with p-cresidine by a conventional method to produce a monoazo compound, which is then re-coupled. It is diazotized and coupled to p-cresidine to produce a disazo intermediate having an amine group. In the production of these intermediates, the diazotization method involves mixing a nitrite such as sodium nitrite with an aqueous solution or suspension of a mineral acid such as hydrochloric acid or sulfuric acid of the diazo component, or a neutral method of adding a nitrite such as sodium nitrite to the diazo component. Alternatively, a method may be used in which nitrite is added to a slightly alkaline aqueous solution and the mineral acid is mixed with the nitrite. The appropriate temperature for diazotization is -10 to 40°C.

Coupling can be carried out by mixing the above diazo solution with an acidic aqueous solution of amines such as hydrochloric acid or acetic acid and neutralizing it to p) 13 to 7. A suitable coupling temperature is 10 to 40°C.

The produced aminoazo compound can be taken out as it is or by precipitating by acid precipitation or salting out and filtered, but if desired, it can also proceed to a diazotization step in the form of a solution or suspension.

If the diazonium salt is poorly soluble and forms a suspension, it can be filtered and used as a press cake in the next diazotization step.

The intermediate disazo compound thus obtained is diazotized and coupled to J-acid, N-methyl J-acid, N-ethyl J-acid, or N-phenyl J-acid in an alkaline manner to form the formula (1).
of water-soluble dye is obtained.

In the above, the diazotization method may be carried out by the above-mentioned normal method, but when the aminoazo compound has extremely low solubility in acidic conditions, the progressive method is preferable. Diazotization temperature is 0-4
0°C is suitable.

The diazo solution is a suspension, which can be used as is or filtered to obtain a press cake of diazonium salt.

For coupling, a suspension of the diazonium salt or the diazonium salt is added little by little to an alkaline aqueous solution of the coupling component. An alkali is added as necessary so that this liquid removal maintains a pH of 8 to 11. As the alkali, it is preferable to use carbonates such as sodium, potassium, and lithium, amines such as ammonia, mono-, di-, and triethanolamine, and hydroxides and bicarbonates such as sodium and potassium may also be used in combination. good.

Further, if necessary, a conventional coupling accelerator such as pyridine or urea may be added.

A suitable coupling temperature is -10 to 40°C. After the coupling is completed, sodium chloride or/and potassium chloride is added as necessary to salt out and take out.

The copper complex salt of the water-soluble dye of Bunmu (1) can be obtained by a conventional method. That is, the water-soluble dye of formula (1) is in an aqueous solution,
Copper salts such as copper sulfate, copper chloride, copper acetate and usually 70 to 110
Heat to ℃. At this time, organic amines such as ammonia, monoethanolamine, diethanolamine, monoglobanolamine, and pyridine can be added as required.

As the base material for preparing the polarizing film of the present invention, cellulose resin (cellophane), PVA, modified PVA, copolymers of PVA and other resins, etc. are used. Among these, preferred are PVA and modified PVA.

These are copolymers of PVA and other resins, and are hereinafter referred to as P.
It is called VA base material. As a PVA base material, ordinary pure P
In addition to VA, modified polyvinyl alcohol, polyvinyl formal, polyvinyl acetate copolymerized with less than about 15 mol% of unsaturated carboxylic acids or derivatives thereof, unsaturated sulfonic acids or derivatives thereof, α-olefins having 2 to 30 carbon atoms, etc. Examples include acetal, polyvinyl acetal such as polyvinyl butyral, saponified ethylene-vinyl acetate copolymer having an ethylene content of 15 to 55 mol%, and the like. Examples of methods for manufacturing polarizing films from these base materials include a method of dyeing the molded PVA film itself, a method of adding dye to a solution of PVA resin, and forming a film after dyeing the undiluted solution. . First, a general dyeing method and stretching method for PVA film will be explained.

0 in a dyebath containing the water-soluble dye of formula (1) or its copper complex and, if necessary, dyeing aids such as inorganic salts and surfactants.
The PVA-based film is immersed and dyed at a temperature of .degree. C. to 70.degree. C., preferably 30 to 45.degree. C., then treated with boric acid if necessary, and dried. In order to impart a polarizing function to the dyed film, it is stretched uniaxially by a factor of 2 or more, preferably 2.5 to 4 times, before, after or during dyeing. When stretching is carried out before or after dyeing, it may be carried out under dry conditions (usually in the range of room temperature to 180°C) in addition to wet stretching, and when stretching is carried out simultaneously with dyeing, it may be carried out in a dye bath at 0 to 70°C. Preferably it is stretched at 30 to 45°C.

Next, the method of forming a film after dyeing with a stock solution is to first dissolve the PVA base material (resin) in a solvent such as water, an organic solvent, or a water-alcohol mixed solvent, and then dye the water-soluble dye of formula (1) or its copper complex salt. and perform stock solution staining.

This dye stock solution is formed into a film by a casting method, a solution coating method, an extrusion method, etc. to produce a dyed film. In order to impart a polarizing function to the dyed film leaked through the process, the dyed film is uniaxially stretched under the same wet or dry conditions as described above.

Here, - axial stretching refers to completely stretching the film only in one axis direction (free width - axial stretching), as well as slightly stretching the film in the direction perpendicular to the stretching direction to prevent shrinkage in the width direction (constant It also means width uniaxial stretching).

In addition, as a method for dyeing films, the above-mentioned dyeing by dipping or dyeing with a stock solution is common, but there is also a method in which printing paste is prepared, printed on the film, heated, and dyed by internal diffusion. You can also hire them.

The water-soluble dyes represented by formula (1) or their copper complex salt dyes can be used alone or in combination, and can also be used to create various hues by blending these dyes with other dyes. It is possible to produce a polarizing film dyed with a high polarization rate. Gray, which is often used for special cleaning, can be changed by using a water-soluble dye represented by formula (1) or its copper complex salt dye as a blank compounding component, and a polarizing film exhibiting excellent polarizing ability and favorable absorption characteristics. It also has excellent stability against heat.

The polarizing film produced in this way can be used as is, or in fields where particularly high durability is required, a support film made of polyester, vinyl chloride, cellulose X) reacetate, acrylic resin, polyether sulfone, etc. It can also be coated with a special acrylic resin or the like and used as a polarizing plate with a high polarization rate and high durability.

Among the dyes of formula (1) of the present invention, defective formulas (2) and (4)
Give an example of a preferable dye.

A press cake containing 47.5 parts of a disazo compound represented by the following formula was obtained by filtration.

That is, these dyes have a preferable deep blue hue, good dyeing properties for PVA, and a high color value, and are particularly advantageous in that polarizing films with high polarization ratios can be obtained. Furthermore, it has good water solubility and is easy to handle.

Example The present invention will be explained below using specific examples.

In the examples, all structural formulas are shown in free acid form, and parts are by weight.

Example 1゜2-Methyl-5-methoxy-4-aminoazobenzene-
34.3 parts (+/10 mol) of sodium 4'-sulfonate was dissolved in 300 parts of water, 25 parts of concentrated hydrochloric acid and 6.9 parts of sodium nitrite were added to diazotize it, and 13.7 parts of p-cresidine was added thereto. was dissolved in an aqueous hydrochloric acid solution and added, and then sodium acetate was added to neutralize to pH 4, followed by coupling. After the reaction is completed, the press cake is hydroxylated in 2000 parts of warm water.) Neutralize and dissolve with IJum, add 8 parts of sodium nitrite to the solution, and add 40 parts of 5% hydrochloric acid solution.
0 parts at about 20°C to diazotize.

After completion of diazotization, excess nitrous and sulfamino acids were added for decomposition, and the suspension of this diazonium salt was mixed with 31.5 parts of N-phenyl J acid and 600 parts of a 10% aqueous sodium carbonate solution.
The mixture was added dropwise at about 20° C. to the solution dissolved in the solution. After stirring for 2 hours, 90 parts of sodium chloride was added to salt out the mixture, stirred overnight, filtered, washed with a 3% aqueous sodium chloride solution, and dried to obtain 72 parts of trisazo dye represented by the following formula (2).

A dye bath of 0.3 g/-e of this trisazo dye was prepared and 40
A polyvinyl alcohol film having a thickness of 75 μm was immersed and dyed for 2 minutes while maintaining the temperature at °C. The wet dyed film was stretched 4 times in a 5% boric acid aqueous solution at 40°C, washed with water, and dried to produce a blue-violet polarizing film. The polarization rate ρ(
The single plate transmittance was 43%, λmax was 600 nm, and ρ(max) was 97.5%.

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

For comparison, C is known as a blue-violet dye for polarizing films.
, 1. When a polarizing film was prepared in the same manner as above using Direct Violet 9 (the structural formula below), λn1a
X is ρ(rna) when the single plate transmittance is 43% at 575 nm.
x) was 92.5%, showing that the dye of the present invention was superior.

Example 2 A trisazo dye represented by formula (3) was obtained by using 25.3 parts of N-methyl J acid in place of N-phenyl J acid in Example 1.

A polyvinyl alcohol film was treated with this aqueous solution of trisazo dye in the same manner as in Example 1 to produce a pre-reddish polarizing film. The polarization rate ρ(max) at the absorption maximum λmax of the polarizing film was measured, and the single plate transmittance was 43%.
λmax was 585 nm and ρ(max) was 955%.

Example 3 2-amino-4,8-naphthalenedisulfonic acid 30.3
(1/IQ mol) in 6 parts of water and 26 parts of concentrated hydrochloric acid.
1 part and 7 parts of sodium nitrite were added to diazotize the mixture. After completion of the reaction, excess nitrous acid and sulfamic acid were added to decompose it, and then 13.7 parts of p-cresidine dissolved in an aqueous hydrochloric acid solution was added thereto, and sodium acetate was added at 15 to 20°C.
It was neutralized to H4 and coupled. After the reaction was completed, the precipitated crystals were filtered to obtain 43.7 parts of a monoazo compound of the following formula.

This monoazo compound was neutralized and dissolved with sodium hydroxide in 500 parts of water, and a solution containing 8 parts of sodium nitrite was added dropwise to 300 parts of a 10% aqueous hydrochloric acid solution at 15 to 20°C to diazotize.

After the completion of the reaction, excess nitrous acid was decomposed with sulfamic acid, 13.7 parts of p-cresidine was dissolved in an aqueous hydrochloric acid solution, and sodium acetate was added at 15 to 20°C.
It was neutralized with p^ and coupled.

After the reaction was completed, the precipitated crystals were filtered to obtain 52.2 parts of a disazo compound of the following formula.

Next, this disazo compound is dissolved in 100'n parts of water by neutralization with sodium hydroxide, and a solution of 7 parts of sodium nitrite is added to 15-20 parts of 10% aqueous hydrochloric acid solution.
It was added dropwise at ℃ to diazotize.

After completion of diazotization, the diazonium salt solution was decomposed with excess nitrous acid and sulfamic acid, and then the diazonium salt solution was dissolved in N-phenyl J acid 30.5%.
The mixture was added dropwise to a solution of 500 parts of IJum aqueous solution at 15 to 20°C for coupling.

After completion of the reaction, add 100 parts of sodium chloride and salt out,
After filtration and drying, 79 parts of trisazo dye of the following formula were obtained.

A dye bath containing 0.3 g/ffl of this trisazo dye was prepared, and a polyvinyl alcohol film was treated in the same manner as in Example 1 to produce a blue polarizing film. As a result of measuring the polarization coefficient ρ (max) at the absorption maximum λmax of the polarizing film, the single plate transmittance was 43%, /imaX was 600 river n
ρ(max) was 97.5%.

Example 4 In the same manner as in Examples 1 to 3, dyes of general formula (1) shown in the following table were produced.

In the table, hue and λmax both indicate the value when the PVA film was dyed.

Example 5 7 parts of the dye of formula (2) described in Example 1 above was dissolved in 100 parts of water, 7.0 parts of monoethanolamine was added thereto, an aqueous solution of 2.4 parts of crystalline copper sulfate was added, and the mixture was heated at 90°C. It was heated for 3 hours. Add 6.0 parts of sodium chloride, cool and salt out, stir overnight, filter, wash with 5% sodium chloride aqueous solution, and dry to obtain a trisazo dye represented by the following formula (16) 6.
I got 1 copy.

A polyvinyl alcohol film was treated with this aqueous solution of trisazo dye in the same manner as in Example 1 to produce a blue polarizing film. As a result of measuring the polarization rate ρ (max) at the absorption maximum λjnax of the polarizing film, the single plate transmittance was 43
%, λmax is 535 nm and ρ(max) is 96.
It was 0%.

Example 6 46.3 parts of trisazo dye of formula (4) described in Example 3 (
1/20 mole) was dissolved in 1000 parts of water, 18.3 parts of monoethanolamine was added to the solution, and then copper sulfate (CuS04
・13 parts of 5H20) were added and heated to cause a copperization reaction at 90 to 95°C. After the reaction was completed, 80 parts of sodium chloride was added to salt out the mixture, followed by filtration and drying to obtain 46.8 parts of trisazo copper complex dye of the following formula.

A dye bath containing 0.3 g/4 of this trisazo copper complex dye was prepared, and a polyvinyl alcohol film was treated in the same manner as in Example 1 to produce a greenish-blue polarizing film.

The polarization rate ρ(m
As a result of measuring the single plate transmittance, λmax was 630 nm, and ρ(max) was 95.9%.

Example 7 Effects of the Invention In particular, a water-soluble trisazo dye was obtained which, when used for dyeing poval films, provides a polarizing film having a high polarization index and high thermal stability. This polarizing film has excellent optical properties as a blue polarizing film.

Hue and λmax are both for those dyed on PV and A films.

Claims (1)

[Claims] 1. Formula (1) as a free acid ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (1) [In formula (1), A is a benzene ring or a naphthalene ring that may have a methyl group, R represents an amino group, a methylamino group, an ethylamino group or a phenylamino group, respectively. ] Water-soluble dye represented by or this copper complex salt dye 2, a polarizing film containing the water-soluble dye of formula (1) described in claim 1 or this copper complex dye