JPWO2018135617A1 - Azo compound or salt thereof, and dye polarizing film and dye polarizing plate containing the same - Google Patents

Abstract

Provided are a high-performance dye-based polarizing film and a dye-based polarizing plate having excellent polarizing performance, particularly a neutral gray high-performance dye-based film and a dye-based polarizing plate, and an azo compound or a salt thereof capable of producing the same. The purpose is to do. The following formula (1): (wherein A1 and A2 are each independently represented by a hydrogen atom or the following formula (2): except that both A1 and A2 are hydrogen atoms) An azo compound or a salt thereof is provided.

Description

  The present invention relates to a novel azo compound or a salt thereof, and a dye-based polarizing film containing them.

  A polarizing plate having a light transmitting / shielding function is a basic component of a display device such as a liquid crystal display (LCD) together with a liquid crystal having a light switching function. Applications of this LCD include small computers such as calculators and watches in the early days, notebook computers, word processors, liquid crystal projectors, liquid crystal televisions, car navigation systems, indoor / outdoor information display devices, measuring devices, and the like. Further, it can be applied to a lens having a polarization function, and has been applied to sunglasses with improved visibility, and in recent years to polarized glasses compatible with 3D televisions. In addition, it has been applied to practical information terminals such as wearable terminals. Since the applications of the polarizing plate as described above are widespread, it is used under a wide range of conditions from low temperature to high temperature, low humidity to high humidity, and low light to high light. There is a need for polarizing plates with excellent properties.

  Currently, polarizing films are stretched and oriented films of polyvinyl alcohol or derivatives thereof, or polyene films formed by orienting polyene by dehydrochlorination of polyvinyl chloride films or dehydration of polyvinyl alcohol films. The substrate is produced by dyeing or containing iodine or a dichroic dye as a dichroic dye. Among these, an iodine-based polarizing film using iodine as a dichroic dye is excellent in polarization performance, but is weak against water and heat, and is durable when used at high temperature and high humidity for a long time. There is a problem with sex. In order to improve the durability, treatment with an aqueous solution containing formalin or boric acid or a method of using a polymer film having low moisture permeability as a protective film has been considered, but the effect is not sufficient. On the other hand, a dye-type polarizing film using a dichroic dye as a dichroic dye is superior in moisture resistance and heat resistance to an iodine-type polarizing film, but generally has insufficient polarizing performance.

  For example, water-soluble azo compounds described in Patent Document 1 to Patent Document 5 are known as dyes used in the production of a dye-based polarizing film.

  In a polarizing film of neutral color (hereinafter also referred to as “neutral gray”) formed by adsorbing and orienting several dichroic dyes on a polymer film, the orientation directions of the two polarizing films are orthogonal to each other. If there is light leakage (color leakage) of a specific wavelength in the visible light wavelength region when the light is superimposed on the liquid crystal (orthogonal position), the hue of the liquid crystal display changes in the dark state when the polarizing film is mounted on the liquid crystal panel. May end up. Therefore, when a polarizing film is mounted on a liquid crystal display device, several dichroic dyes are adsorbed and oriented on the polymer film to prevent discoloration of the liquid crystal display due to color leakage at a specific wavelength in the dark state. In the neutral gray polarizing film, the transmittance at the orthogonal position (orthogonal transmittance) in the wavelength region of the visible light region must be uniformly reduced.

  Until recently, in order to improve the clarity of images on a liquid crystal display, images were displayed with high luminance. In hybrid cars and outdoor display devices (for example, industrial instruments and wearable terminals) equipped with such a display, there has been a demand for longer battery driving time. For this reason, a polarizing plate exhibiting a neutral gray hue with good polarization performance (hereinafter referred to as a “neutral gray polarizing plate” so that the sharpness of the image can be improved even if the luminance is reduced in order to reduce the power consumption of the liquid crystal display. Is also called for.). Further, in the in-vehicle liquid crystal display, there is a demand for a polarizing plate that does not change the degree of polarization even in a high-temperature and high-humidity environment in a summer car. Previously, iodine-based polarizing plates with good polarization performance and neutral gray were used for in-vehicle liquid crystal displays. However, the iodine-based polarizing plate has a problem that light resistance, heat resistance, and moist heat resistance are not sufficient because iodine is a dichroic dye as described above. In order to solve this problem, a neutral gray polarizing plate using a dye-based dichroic dye as a polarizer has been used. Neutral gray polarizing plates are usually used in combination with pigments of three primary colors (red, green, and blue) in order to improve the average transmittance and polarization performance in the entire visible light wavelength region. Therefore, it was necessary to develop a dichroic dye having good polarization performance for each of the three primary colors.

  Further, the bright line of the light source is different for each liquid crystal display. Therefore, in developing a dichroic dye having good polarization performance, it is particularly important to design the wavelength of the pigment in accordance with the wavelength of the emission line. For this reason, it is necessary for the three primary color pigments to reliably control light in a limited wavelength range, and to suppress the absorption in other wavelength ranges as much as possible and to have excellent polarization performance.

Japanese Patent Laid-Open No. 3-012606 JP 2001-33627 A International Publication No. 2009/154055 JP 2003-327858 A Japanese Patent Laid-Open No. 3-12606 JP-A-2005-171231

  However, the conventional blue colorant for polarizing plates is a dye having a copper complex structure as described in Patent Document 6, and in this case, the absorption in the short wavelength region (400 to 500 nm) is increased due to the influence of the copper complex, When the three primary color pigments are combined, there is a drawback that a neutral gray hue cannot be realized. Therefore, it has been desired to develop a blue pigment that can produce a neutral gray polarizing plate that suppresses absorption on the short wavelength side and has improved transmittance and polarization performance in the entire visible light wavelength region.

  Accordingly, an object of the present invention is to enable high-performance dye-based polarizing films and dye-based polarizing plates having excellent polarizing performance, in particular, neutral gray high-performance dye-based films and dye-based polarizing plates, and production thereof. To provide an azo compound or a salt thereof.

  As a result of diligent research to achieve such an object, the present inventors have found that a polarizing film and a polarizing plate containing a specific azo compound or a salt thereof have excellent polarizing performance and a neutral gray hue. As a result, the present invention has been completed.

That is, the present invention relates to the following [1] to [15].
[1]
Following formula (1):

(In the formula, A ₁ and A ₂ are each independently a hydrogen atom or the following formula (2):

(In the formula, the ring substituted by R ₁ and the sulfo group is a benzothiazole ring when a ring represented by a broken line is not present, and a naphthothiazole ring when a ring represented by a broken line is present. R ₁ is a chlorine atom, a sulfo group, a nitro group, a hydroxy group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an alkyl group having 1 to 4 carbon atoms having a sulfo group, hydroxy A C1-C4 alkyl group having a group, a C1-C4 alkyl group having a carboxy group, a C1-C4 alkoxy group having a sulfo group, a C1-C4 alkoxy group having a hydroxy group And a group consisting of a C 1-4 alkoxy group having a carboxy group,
B is a phenylene group or naphthylene group which may have a substituent, and the substituent is a chlorine atom, a sulfo group, a nitro group, a hydroxy group, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms. An alkyl group having 1 to 4 carbon atoms having a sulfo group, an alkyl group having 1 to 4 carbon atoms having a hydroxy group, an alkyl group having 1 to 4 carbon atoms having a carboxy group, and an alkyl group having 1 to 4 carbon atoms having a sulfo group Selected from the group consisting of an alkoxy group, an alkoxy group having 1 to 4 carbon atoms having a hydroxy group, and an alkoxy group having 1 to 4 carbon atoms having a carboxy group (in the case where there are a plurality of them, each independently)
m is an integer of 1 to 3)
Except that A ₁ and A ₂ are both hydrogen atoms,
(The two bonds of -NH- are each independently bonded to the substitution position indicated by a or b)
Or a salt thereof.
[2]
Formula (2) is the following formula (3):

(Wherein R _1a is a substituted ring, and R _1a represents the same as R ₁ in formula (2);
R ₂ and R ₃ are each independently a hydrogen atom, a chlorine atom, a sulfo group, a nitro group, a hydroxy group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a carbon number 1 to 1 having a sulfo group. 4 alkyl groups, hydroxy groups having 1 to 4 carbon atoms, carboxyl groups having 1 to 4 carbon atoms, sulfo groups having 1 to 4 carbon atoms, hydroxy groups having carbon atoms Selected from the group consisting of 1-4 alkoxy groups and C 1-4 alkoxy groups having a carboxy group;
m ₁ represents the same meaning as m in formula (2)),
Or following formula (4):

(R _1b in the formula is substituted, and R _1b is the same as R ₁ in formula (2),
R _{4 to} R ₆ are each independently a hydrogen atom, a chlorine atom, a sulfo group, a nitro group, a hydroxy group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a carbon number 1 to 1 having a sulfo group. 4 alkyl groups, hydroxy groups having 1 to 4 carbon atoms, carboxyl groups having 1 to 4 carbon atoms, sulfo groups having 1 to 4 carbon atoms, hydroxy groups having carbon atoms Selected from the group consisting of 1-4 alkoxy groups and C 1-4 alkoxy groups having a carboxy group;
m ₂ represents the same meaning as m in formula (2))
The azo compound or a salt thereof according to [1] represented by
[3]
The azo compound or salt thereof according to [2], wherein A ₁ and A ₂ are each independently represented by formula (3) or formula (4).
[4]
The azo compound or a salt thereof according to [2], wherein A ₁ is represented by formula (3) or formula (4), and A ₂ is a hydrogen atom.
[5]
R _1b in Formula (4) is a hydrogen atom, a chlorine atom, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms, and R _{4 to} R ₆ are each independently a hydrogen atom or carbon number. The azo compound or a salt thereof according to any one of [2] to [4], which is an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms which may have a sulfo group.
[6]
R _1a in formula (3) is a hydrogen atom, a chlorine atom or an alkyl group having 1 to 4 carbon atoms, and R ₂ and R ₃ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a sulfo group. The azo compound or a salt thereof according to any one of [2] to [5], which is an alkoxy group having 1 to 4 carbon atoms which may have
[7]
The azo compound or a salt thereof according to any one of [1] to [6], wherein the —NH— substitution position in formula (1) is a.
[8]
A dye-based polarizing film comprising the azo compound or a salt thereof according to any one of [1] to [7] and a polarizing film substrate.
[9]
A dye-based polarizing film comprising at least one kind of the azo compound or a salt thereof according to any one of [1] to [7] and an organic dye other than the azo compound and a polarizing film substrate.
[10]
A dye-based polarizing film comprising two or more azo compounds or salts thereof according to any one of [1] to [7], one or more organic dyes other than these, and a polarizing film substrate.
[11]
The dye-based polarizing film according to any one of [8] to [10], wherein the polarizing film substrate is a film formed from a polyvinyl alcohol resin or a derivative thereof.
[12]
A dye-based polarizing plate obtained by laminating a transparent protective layer on at least one surface of the dye-based polarizing film according to any one of [8] to [11].
[13]
A liquid crystal display device comprising the dye-based polarizing film according to any one of [8] to [11] or the dye-based polarizing plate according to [12].
[14]
The dye-type polarizing film in any one of [8]-[11] which exhibits neutral gray.
[15]
[14] A vehicle-mounted display device or an outdoor display device comprising the dye-based polarizing plate according to [14] or a dye-based polarizing plate obtained by bonding a transparent protective layer to at least one surface of the dye-based polarizing film.

  The present invention relates to a high-performance dye-based polarizing film and a dye-based polarizing plate having excellent polarizing performance, in particular, a neutral gray high-performance dye-based film and a dye-based polarizing plate, and an azo compound that enables production thereof. The salt can be provided. In one embodiment, the polarizing plate of the present invention has moisture resistance, heat resistance, and / or light resistance.

<Azo compound or salt thereof>
The azo compound of the present invention has the following formula (1):

It is represented by
In formula (1), the two bonds of —NH— are each independently bonded to the substitution position represented by a or b.

A ₁ and A ₂ are a hydrogen atom or the following formula (2):

It is represented by However, when both of A ₁ and A ₂ is a hydrogen atom is excluded. One of A ₁ and A ₂ is a hydrogen atom, and the other is represented by formula (2), or both A ₁ and A ₂ are represented by formula (2). Preferably, both A ₁ and A ₂ are represented by formula (2).

In the formula (2), the ring substituted by R ₁ and the sulfo group is a benzothiazole ring when there is no ring represented by a broken line, and naphtho when a ring represented by a broken line is present. Thiazole ring. When there is no ring represented by a broken line, that is, when the ring substituted by R ₁ is a benzothiazole ring, the substitution positions of R ₁ and the sulfo group are not particularly limited, but only the 4-position, only the 6-position, A combination of the 4th and 6th positions and a combination of the 6th and 7th positions are preferable, and a combination of only the 6th position and the 4th and 6th positions is more preferable. When a ring represented by a broken line is present, that is, when the ring substituted by R ₁ is a naphthothiazole ring, the substitution position of the sulfo group and R ₁ is not particularly limited, but a combination of the 6-position and the 8-position, A combination of the 4th, 6th and 8th positions, and a combination of the 4th, 7th and 9th positions are preferred, and a combination of the 6th and 8th positions is more preferred.

R ₁ is a hydrogen atom, a chlorine atom, a sulfo group, a nitro group, a hydroxy group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an alkyl group having 1 to 4 carbon atoms having a sulfo group, hydroxy A C1-C4 alkyl group having a group, a C1-C4 alkyl group having a carboxy group, a C1-C4 alkoxy group having a sulfo group, a C1-C4 alkoxy group having a hydroxy group And a group consisting of an alkoxy group having 1 to 4 carbon atoms having a carboxy group. A sulfo group and an alkoxy group having 1 to 4 carbon atoms are preferred. When there are a plurality of R ₁ , they are each independently selected.

  The lower alkoxy group having a hydroxy group is preferably a linear alkoxy group in which the end of the alkoxy group is substituted with a hydroxy group, more preferably a 4-hydroxypropoxy group or a 4-hydroxybutoxy group. The lower alkoxy group having a carboxy group is preferably a linear alkoxy group in which the end of the alkoxy group is substituted with a carboxy group, and more preferably a 4-carboxypropoxy group or a 4-carboxybutoxy group. The lower alkoxy group having a sulfo group is preferably a linear alkoxy group in which the end of the alkoxy group is substituted with a sulfo group, and more preferably a 4-sulfopropoxy group or a 4-sulfobutoxy group.

  B is a phenylene group or naphthylene group which may have a substituent. The bonding position between B and the two azo groups is not limited. Substituents are hydrogen atom, chlorine atom, sulfo group, nitro group, hydroxy group, alkyl group having 1 to 4 carbon atoms, alkoxy group having 1 to 4 carbon atoms, alkyl group having 1 to 4 carbon atoms having sulfo group, hydroxy A C1-C4 alkyl group having a group, a C1-C4 alkyl group having a carboxy group, a C1-C4 alkoxy group having a sulfo group, a C1-C4 alkoxy group having a hydroxy group And a group consisting of an alkoxy group having 1 to 4 carbon atoms having a carboxy group. When there are a plurality of substituents, they are each independently selected. When B is a phenylene group which may have a substituent, the substitution position is not particularly limited, but a combination of the 2-position and the 5-position and a combination of the 3-position and the 5-position are preferred, and a combination of the 2-position and the 5-position is preferred. Particularly preferred. When B is a naphthylene group which may have a substituent, the substitution position is not particularly limited, but only the 2-position, the 6-position, the 7-position only, the combination of the 2-position and the 6-position, and the 2-position and the 7-position Is preferable, and only the 2nd position and the 2nd and 7th positions are particularly preferable.

Formula (2) is preferably the following formula (3):

Or, formula (4):

It is represented by

In formula (3), the ring in which R _1a and R _1a are substituted represents the same meaning as the ring in which R ₁ and R ₁ in formula (2) are substituted.
R ₂ and R ₃ represent the same meaning as the substituent that B in Formula (2) may have. Preferred are a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, and an alkoxy group having 1 to 4 carbon atoms having a sulfo group.
m ₁ represents the same meaning as m in formula (2).

In the formula (4), the ring in which R _1b and R _1b are substituted has the same meaning as the ring in which R ₁ and R ₁ in the formula (2) are substituted.
R < ₄ > -R < ₆ > represents the same meaning as the substituent which B in Formula (2) may have. A hydrogen atom, a sulfo group, a hydroxy group, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms is preferable.
m ₂ represents the same meaning as m in Formula (2).

  The azo compound represented by the formula (1) may be in a free form or a salt form. The salt can be, for example, an alkali metal salt such as a lithium salt, a sodium salt, and a potassium salt, or an organic salt such as an ammonium salt or an alkylamine salt. The salt is preferably a sodium salt.

Next, specific examples of the azo compound represented by the formula (1) are given below. In addition, the sulfo group, carboxy group, and hydroxy group in a formula are represented with the form of free acid.

  The azo compound represented by the formula (1) or a salt thereof is, for example, according to a method for producing a normal azo dye as described in Patent Document 3 and dye chemistry (Toyo Hosoda, 1957, page 621). It can be produced by diazotization and coupling.

The following method is mentioned as an example of a specific manufacturing method.
The aminothiazoles represented by the following formula (A) are diazotized and subjected to primary coupling with anilines represented by the following formula (B) or aminonaphthalenes represented by the following formula (C), and the following formula (D Or a monoazoamino compound represented by the following formula (E).

The monoazoamino compound (D) or (E) is diazotized, respectively, and secondarily coupled with a naphthol compound of the following formula (F) to obtain an azo compound of the formula (1).

In formulas (A) to (F), the substitution positions of R ₁ and R ₁ represent the same meaning as in formula (2), R ₂ and R ₃ represent the same meaning as in formula (3), and R _{4 to} R ₆ represent the same meaning as in formula (4), and m represents the same meaning as in formula (2).

  In the above production method, the diazotization step is performed by a conventional method in which a nitrite such as sodium nitrite is mixed with a mineral acid aqueous solution or suspension such as hydrochloric acid or sulfuric acid of the diazo component, or a neutral or weak diazo component. It is preferable to carry out by the reverse method of adding nitrite to an alkaline aqueous solution and mixing this with mineral acid. The temperature for diazotization is suitably -10 to 40 ° C. In addition, the coupling step with anilines is preferably carried out by mixing acidic aqueous solutions such as hydrochloric acid and acetic acid and the above diazo liquids under acidic conditions at a temperature of −10 to 40 ° C. and a pH of 2 to 7.

  The monoazo compound of the formula (D) or the formula (E) obtained by coupling is filtered as it is, precipitated by aciding out or salting out and filtered out, or in the next step as a solution or suspension. You can also go to. If the diazonium salt is insoluble and in suspension, it can be filtered and used as a press cake in the next coupling step.

  The secondary coupling reaction between the diazotized compound of the monoazo compound of the formula (D) or the formula (E) and the naphthols represented by the formula (F) is neutral at a temperature of −10 to 40 ° C. and a pH of 7 to 10. It is preferably carried out under alkaline conditions. After completion of the reaction, the obtained azo compound or salt of the formula (1) is preferably precipitated by salting out and filtered out. Further, when purification is necessary, salting out may be repeated or precipitated from water using an organic solvent. Examples of the organic solvent used for purification include water-soluble organic solvents such as alcohols such as methanol and ethanol, and ketones such as acetone.

  The aminothiazole compound represented by the formula (A) is represented as 2-aminobenzothiazole when there is no ring represented by a broken line, for example, 2-amino-6-sulfobenzothiazole, 2-amino Examples include -7-methoxy-6-sulfobenzothiazole, 2-amino-4,6-disulfobenzothiazole, and 2-amino-7-methoxy-4,6-disulfobenzothiazole. The aminothiazole compound represented by the formula (A) is represented as 2-aminonaphthothiazole when a ring represented by a broken line exists, for example, 2-amino-6,8-disulfonaphthothiazole, 2-amino-4,6,8-trisulfonaphthothiazole, 2-amino-4-chloro-6,8-disulfonaphthothiazole, 2-amino-6-sulfopropoxy-4,8-disulfonaphthothiazole, 2-amino-6-sulfopropoxy-4,7,8-trisulfonaphthothiazole, 2-amino-6-methoxy-4,7,8-trisulfonaphthothiazole, 2-amino-7-sulfopropoxy-4, 9-disulfonaphthothiazole, 2-amino-4-sulfopropoxy-5,7,9-trisulfonaphthothiazole, etc., and 2-amino-6 Sulfo benzothiazole, 2-amino-7-methoxy-6-sulfo-benzothiazole, and 2-amino-6,8-di-sulfo-naphthoquinone chestnut azoles are preferred.

  Examples of the anilines of the formula (B) include anilines having a lower alkoxyl group having a sulfo group. Examples include 3- (2-amino-4-methylphenoxy) propane-1-sulfonic acid, 3- (2-aminophenoxy) propane-1-sulfonic acid, and 3- (2-amino-4-methylphenoxy). ) Butane-1-sulfonic acid and the like. Examples of other anilines include aniline, 2-methylaniline, 3-methylaniline, 2-ethylaniline, 3-ethylaniline, 2,5-dimethylaniline, 2,5-diethylaniline, 2-methoxyaniline, Examples include 3-methoxyaniline, 2-methoxy-5-methylaniline, 2,5-dimethoxyaniline, 3,5-dimethylaniline, 2,6-dimethylaniline, and 3,5-dimethoxyaniline. Preferably, 2-methoxy-5-methylaniline and 2,5-dimethoxyaniline are used. These anilines may have an amino group protected. Examples of the aminonaphthalenes of the formula (C) include 1-aminonaphthalene, 1-aminonaphthalene-6-sulfonic acid, 1-aminonaphthalene-7-sulfonic acid, 1-amino-2-methoxynaphthalene-6-sulfone. Acid, 1-amino-2-methoxynaphthalene-7-sulfonic acid, 1-amino-2-ethoxynaphthalene-6-sulfonic acid, and 1-amino-2-ethoxynaphthalene-7-sulfonic acid, preferably Examples include 1-aminonaphthalene-7-sulfonic acid and 1-amino-2-methoxynaphthalene-7-sulfonic acid. In these aminonaphthalenes, the amino group may be protected. Examples of the protecting group include the ω-methanesulfone group.

  The azo compound or salt thereof according to the present invention is useful as a dye for a polarizing film. The azo compound or a salt thereof according to the present invention is a blue dye, and has a maximum absorption wavelength in the vicinity of 600 to 670 nm, for example. According to the azo compound or a salt thereof according to the present invention, it is possible to produce a high-performance dye-based polarizing plate having excellent polarization performance, in particular, there is little color leakage at an orthogonal position in the wavelength region of the visible light region, A neutral gray high-performance dye-based polarizing plate can be realized. In one embodiment, the azo compound or a salt thereof according to the present invention can be suitably used for producing a neutral gray polarizing plate for vehicle use or outdoor display used under high temperature and high humidity conditions.

<Dye-type polarizing film>
The dye-based polarizing film includes a dichroic dye containing at least an azo compound represented by the formula (1) or a salt thereof, and a polarizing film substrate. The dye-based polarizing film can be either a color polarizing film or a neutral gray polarizing film, and is preferably a neutral gray polarizing film. Here, “Neutral Gray” means that there is little light leakage (color leakage) at a specific wavelength in the wavelength region of the visible light region in a state where two polarizing films are superposed so that their orientation directions are orthogonal to each other. means.

  The dye-based polarizing film may contain one or more azo compounds represented by the formula (1) or a salt thereof as a dichroic dye, and may further contain one or more other organic dyes as necessary. it can. The other organic dye used in combination is not particularly limited, but is a dye having absorption characteristics in a wavelength region different from the absorption wavelength region of the azo compound represented by the formula (1) or a salt thereof, and has high dichroism. It is preferable. Examples of the organic dye used in combination include C.I. I. direct. Yellow 12, C.I. I. direct. Yellow 28, C.I. I. direct. Yellow 44, C.I. I. direct. Orange 26, C.I. I. direct. Orange 39, C.I. I. direct. Orange 71, C.I. I. direct. Orange 107, C.I. I. direct. Red 2, C.I. I. direct. Red 31, C.I. I. direct. Red 79, C.I. I. direct. Red 81, C.I. I. direct. Red 247, C.I. I. direct. Green 80, and C.I. I. direct. Representative examples include Green 59 and dyes described in Patent Documents 1 to 5. These dyes are contained in the dye-type polarizing film as free acids or as alkali metal salts (for example, Na salt, K salt, Li salt), ammonium salts, or salts of amines.

  When other organic dyes are used in combination, depending on whether the target dye-based polarizing film is a neutral gray polarizing film, a color polarizing film for liquid crystal projectors, or other color polarizing films, The type is different. The mixing ratio of other organic dyes is not particularly limited, but the total of one or more organic dyes is 0.1 to 10 with respect to 100 parts by mass of the azo compound of formula (1) or a salt thereof. It is preferable that it is the range of a mass part.

  In the case of a neutral gray polarizing film, the types of other organic dyes used together and the blending ratio thereof are adjusted so that the obtained polarizing film has less color leakage in the wavelength region of the visible light region.

  In the case of a color polarizing film, when the obtained polarizing film has a high single-plate average light transmittance in a specific wavelength range, and the two polarizing films are stacked so that the absorption axes are orthogonal (orthogonal position) For example, a single plate average light transmittance of 39% or more in a specific wavelength region and an average light transmittance in an orthogonal position of 0.4 or less are used in combination. Adjustment of the kind of other organic dye and its compounding ratio is performed. Here, the single plate average light transmittance is a polarizing plate or a single polarizing plate (hereinafter simply referred to as a polarizing plate) not provided with a support such as an AR (antireflection) layer and a transparent glass plate. It is an average value of light transmittance in a specific wavelength region when natural light is incident on (used in the meaning). The average light transmittance at the orthogonal position is an average value of light transmittance in a specific wavelength region when natural light is incident on two polarizing films or polarizing plates arranged so that the orientation directions are orthogonal.

  Dye-type polarizing film of various colors or neutral gray dye-type polarizing film contains at least the azo compound represented by the formula (1) or a salt thereof, and further contains another organic dye as necessary. In a polarizing film substrate (for example, a polymer film) by a known method, orientated, mixed with a liquid crystal, or oriented by a coating method.

  The polarizing film substrate is preferably a polymer film, more preferably a film formed from a polyvinyl alcohol resin or a derivative thereof. Specific examples of the polarizing film substrate include polyvinyl alcohol or derivatives thereof, and any of these modified with olefins such as ethylene and propylene, and unsaturated carboxylic acids such as crotonic acid, acrylic acid, methacrylic acid, and maleic acid. And the like. As the polarizing film substrate, a film formed from polyvinyl alcohol or a derivative thereof is suitably used from the viewpoints of dye adsorption and orientation. The thickness of the polarizing film substrate is usually 30 to 100 μm, preferably about 50 to 80 μm.

  When the polarizing film substrate is a polymer film, a method of dyeing the polymer film can be usually employed to contain the dichroic dye containing at least the azo compound of the formula (1) or a salt thereof. . For example, the staining can be performed as follows. First, a dye bath is prepared by dissolving the azo compound of the present invention or a salt thereof and, if necessary, other organic dyes in water. The dye concentration in the dye bath is not particularly limited, but is usually selected from the range of about 0.001 to 10% by mass. Moreover, you may use a dyeing assistant as needed, for example, it is suitable to use mirabilite at the density | concentration of about 0.1-10 mass%. The polymer film is immersed in the dyeing bath thus prepared for 1 to 10 minutes, for example, and dyeing is performed. The dyeing temperature is preferably about 40 to 80 ° C.

  Orientation of the dichroic dye containing the azo compound of the formula (1) or a salt thereof is performed by stretching a dyed polymer film. As a stretching method, any known method such as a wet method or a dry method can be used. The stretching of the polymer film may optionally be performed before dyeing. In this case, the water-soluble dye is oriented at the time of dyeing. The polymer film containing and orienting the water-soluble dye is subjected to post-treatment such as boric acid treatment by a known method as necessary. Such post-treatment is performed for the purpose of improving the light transmittance and the degree of polarization of the dye-based polarizing film. The conditions for boric acid treatment vary depending on the type of polymer film used and the type of dye used, but generally the boric acid concentration of the boric acid aqueous solution is 0.1 to 15% by mass, preferably 1 to 10% by mass. The treatment is performed, for example, by immersing in a temperature range of 30 to 80 ° C., preferably 40 to 75 ° C., for example, for 0.5 to 10 minutes. Further, if necessary, the fixing treatment may be performed together with an aqueous solution containing a cationic polymer compound.

  The obtained dye-based polarizing film can be used as a polarizing plate by attaching a protective film, and can further be provided with a protective layer or an AR layer and a support, if necessary. Applications of various color dye polarizing plates and neutral gray dye polarizing films include, for example, liquid crystal projectors, calculators, watches, notebook computers, word processors, liquid crystal televisions, car navigation, indoor / outdoor measuring instruments and displays for cars, etc. And lenses and glasses. The dye-based polarizing film has high polarization performance comparable to a polarizing film using iodine, and is excellent in durability. For this reason, it is particularly suitable for various liquid crystal display bodies, liquid crystal projectors, in-vehicle use, and outdoor display use (for example, display use of industrial instruments and wearable use) that require high polarization performance and durability.

<Dye-based polarizing plate>
The dye-based polarizing plate can be obtained by pasting a transparent protective film on one side or both sides of the dye-based polarizing film. Since the dye-based polarizing plate includes the above-described dye-based polarizing film, it has excellent polarizing performance. As a material for forming the transparent protective film, a material excellent in optical transparency and mechanical strength is preferable. For example, in addition to a cellulose acetate film and an acrylic film, a tetrafluoroethylene / hexafluoropropylene copolymer Fluorine films such as polyester film, polyolefin resin or polyamide resin are used. The transparent protective film is preferably a triacetyl cellulose (TAC) film or a cycloolefin film. The thickness of the protective film is preferably 40 to 200 μm.

  Examples of adhesives that can be used to bond the polarizing film and the protective film include polyvinyl alcohol adhesives, urethane emulsion adhesives, acrylic adhesives, and polyester-isocyanate adhesives. Agents are preferred.

  A transparent protective layer may be further provided on the surface of the dye-based polarizing plate. Examples of the further transparent protective layer include an acrylic or polysiloxane hard coat layer and a urethane protective layer. In order to further improve the single plate light transmittance, it is preferable to provide an AR layer on the protective layer. The AR layer can be formed by vapor deposition or sputtering treatment of a material such as silicon dioxide or titanium oxide, and can be formed by thinly applying a fluorine-based material. The dye-based polarizing plate can be used as an elliptically polarizing plate by further attaching a retardation plate to the surface.

  The dye-based polarizing plate may be either a color polarizing plate or a neutral polarizing plate depending on the application.

  Neutral gray polarizing plate has excellent polarization performance. In one embodiment, the neutral gray polarizing plate has less color leakage at a right angle in the wavelength region of the visible light region. Furthermore, in one aspect, the neutral gray polarizing plate is characterized by preventing discoloration and deterioration of polarization performance even in a high temperature and high humidity state, and having less light leakage in an orthogonal position in the visible light region. It is suitable for.

  A neutral gray polarizing plate for in-vehicle use or outdoor display is a polarizing plate with an AR layer provided with an AR layer on a polarizing plate composed of a polarizing film and a protective film in order to further improve the single plate light transmittance. An AR layer provided with a support such as a transparent resin and a polarizing plate with a support are more preferable. The AR layer can be provided on one side or both sides of the polarizing plate. The support is preferably provided on one side of the polarizing plate, and may be provided on the polarizing plate via an AR layer or directly. The support preferably has a flat portion for attaching a polarizing plate, and since it is used for optical purposes, it is preferably a transparent substrate. The transparent substrate is roughly divided into an inorganic substrate and an organic substrate, inorganic substrates such as soda glass, borosilicate glass, crystal substrate, sapphire substrate, and spinel substrate, and acrylic, polycarbonate, polyethylene terephthalate, polyethylene naphthalate, and Although organic substrates, such as a cycloolefin polymer, are mentioned, an organic substrate is preferable. The thickness and size of the transparent substrate may be a desired size.

  A color polarizing plate is excellent in polarization performance. In one embodiment, a color polarizing plate is suitable for use in liquid crystal projectors, in-vehicle use, and outdoor display because it does not cause discoloration or deterioration in polarization performance even in a high-temperature and high-humidity state. A color polarizing plate can be produced by attaching a protective film to a dye-based polarizing film to form a polarizing plate, and providing a protective layer or an AR layer and a support, if necessary.

  A color polarizing plate with a support for in-vehicle use or outdoor display is manufactured by, for example, applying a transparent adhesive (adhesive) agent to the flat surface of the support, and then attaching a dye-based polarizing plate to the coated surface. Can do. Alternatively, a transparent adhesive (adhesive) agent may be applied to the dye-based polarizing plate, and then a support may be attached to the coated surface. The adhesive (adhesive) agent used here is preferably, for example, an acrylic ester-based one. In addition, when using this dye-type polarizing plate as an elliptically polarizing plate, it is normal to stick a phase difference plate side to a support body side, but you may stick a polarizing plate side to a transparent substrate.

<Liquid crystal display device>
A liquid crystal display device includes the dye-based polarizing film or the dye-based polarizing plate. Liquid crystal display devices are used for displays such as calculators, watches, notebook computers, word processors, liquid crystal televisions, car navigation systems, and measuring instruments and displays indoors and outdoors, and particularly require high polarization performance and durability. It is suitably used for various liquid crystal displays, for example, for in-vehicle use and outdoor display (for example, display use for industrial instruments and wearable use).

  The dye-based polarizing film or the dye-based polarizing plate provided in the liquid crystal display device is preferably neutral gray. By using a neutral gray dye-based polarizing film or a dye-based polarizing plate, it is possible to prevent discoloration of the liquid crystal display due to color leakage of a specific wavelength in a dark state.

  In the liquid crystal display device, a dye-based polarizing plate is disposed on one or both of the incident side and the emission side of the liquid crystal cell. The dye-based polarizing plate may or may not be in contact with the liquid crystal cell, but is preferably not in contact from the viewpoint of durability. When the polarizing plate is in contact with the liquid crystal cell on the emission side of the liquid crystal cell, the liquid crystal cell can be used as a support for the dye-based polarizing plate. When the dye-based polarizing plate is not in contact with the liquid crystal cell, it is preferable to use a dye-based polarizing plate using a support other than the liquid crystal cell. Further, from the viewpoint of durability, it is preferable that a dye-type polarizing plate is disposed on both the incident side and the exit side of the liquid crystal cell, and further the polarizing plate surface of the dye-type polarizing plate is on the liquid crystal cell side and the support surface is the light source. It is preferable to arrange on the side. The incident side of the liquid crystal cell is the light source side, and the opposite side is referred to as the emission side.

  A liquid crystal cell included in a liquid crystal display device for in-vehicle use or outdoor display is, for example, an active matrix type, and a liquid crystal is sealed between a transparent substrate on which an electrode and a TFT are formed and a transparent substrate on which a counter electrode is formed. It is preferable to be formed. Light emitted from a light source such as a cold-cathode tube lamp or a white LED passes through a neutral gray polarizing plate, and then passes through a liquid crystal cell, a color filter, and further a neutral gray polarizing plate and is projected onto a display screen.

  In the on-vehicle display device or the outdoor display device configured as described above, the neutral gray polarizing plate has brightness and excellent polarization performance. Further, in one embodiment, the display device for in-vehicle use or outdoor display has durability and light resistance, and therefore, it is difficult to cause discoloration or deterioration of polarization performance even in a high temperature and high humidity state in a vehicle or outdoors, and has a feature of high reliability. Have.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, these are illustrations and do not limit this invention at all. In the examples, “%” and “parts” are based on mass unless otherwise specified.

[Example 1]
After adding 36.0 parts of 2-aminonaphthothiazole-6,8-disulfonic acid to 100 parts of 98% sulfuric acid and dissolving at 50 ° C., 12.6 parts of 60% nitric acid was added and 40% at 5-10 ° C. 50 parts of nitrosylsulfuric acid was added dropwise in about 10 minutes and reacted for 1 hour to obtain a diazo reaction liquid. Next, 15.3 parts of 2,5-dimethoxyaniline was added and dissolved in an acidic aqueous solution obtained by diluting 10.4 parts of 35% hydrochloric acid with 100 parts of water. The diazo reaction liquid was dropped into this aqueous solution over 3 hours and stirred overnight to complete the coupling reaction. Thereafter, filtration was performed to obtain 41.9 parts of a monoazoamino compound represented by the following formula (46).

  41.9 parts of the obtained monoazoamino compound (46) was added to 200 parts of water, and 25% sodium hydroxide was added thereto to dissolve the monoazoamino compound. 13.8 parts of 40% sodium nitrite aqueous solution was added thereto, then 25.0 parts of 35% hydrochloric acid was added at 20-30 ° C., and the mixture was stirred at 20-30 ° C. for 1 hour to obtain a diazo compound. On the other hand, 36.9 parts of 6,6′-iminobis (1-hydroxynaphthalene-3-sulfonic acid) was added to 100 parts of water, and 25% aqueous sodium hydroxide solution was added thereto to make it weakly alkaline. Iminobis (1-hydroxynaphthalene-3-sulfonic acid) was dissolved. The diazotized compound obtained previously was added dropwise to this solution while maintaining the pH at 8 to 10, and stirred to complete the coupling reaction. Then, after salting out with sodium chloride, it filtered and 63.7 parts of compounds represented by Formula (5) were obtained. The maximum absorption wavelength of the compound in a 20% aqueous pyridine solution was 675 nm.

[Example 2]
Example 1 except that 36.9 parts of 6,6′-iminobis (1-hydroxynaphthalene-3-sulfonic acid) are replaced with 36.9 parts of 7,7′-iminobis (1-hydroxynaphthalene-3-sulfonic acid) In the same manner as above, 63.7 parts of a compound represented by the formula (6) was obtained. The maximum absorption wavelength of the compound in a 20% aqueous pyridine solution was 678 nm.

[Example 3]
It is represented by the formula (11) in the same manner as in Example 1 except that 36.0 parts of 2-aminonaphthothiazole-6,8-disulfonic acid is replaced with 23.0 parts of 2-aminobenzothiazole-6-sulfonic acid. 55.4 parts of this compound were obtained. The maximum absorption wavelength of the compound in a 20% aqueous pyridine solution was 647 nm.

[Example 4]
The same procedure as in Example 1 was repeated except that 36.0 parts of 2-aminonaphthothiazole-6,8-disulfonic acid was replaced with 26.0 parts of 2-amino-7-methoxybenzothiazole-6-sulfonic acid. ) 57.3 parts of a compound represented by The maximum absorption wavelength in a 20% aqueous pyridine solution was 667 nm.

[Example 5]
A diazotate was obtained from 41.9 parts of the compound represented by the formula (46) in the same manner as in Example 1, and 79.6 parts of the compound represented by the formula (5) were added to 200 parts of water. The solution was added dropwise to the dissolved aqueous solution while maintaining the pH at 9 to 11, and stirred to complete the coupling reaction. Then, after salting out with sodium chloride, it filtered and 78.4 parts of compounds represented by Formula (16) were obtained. The maximum absorption wavelength of the compound in a 20% aqueous pyridine solution was 700 nm.

[Example 6]
78.4 parts of a compound represented by the formula (17) was obtained in the same manner as in Example 5 except that the compound represented by the formula (5) was changed to the compound represented by the formula (6). The maximum absorption wavelength of the compound in a 20% aqueous pyridine solution was 701 nm.

[Example 7]
In the same manner as in Example 1 and Example 5 except that 36.0 parts of 2-aminonaphthothiazole-6,8-disulfonic acid was replaced with 23.0 parts of 2-amino-benzothiazole-6-sulfonic acid, the formula ( 28. 1 part of the compound represented by 28) was obtained. The maximum absorption wavelength of the compound in a 20% aqueous pyridine solution was 665 nm.

[Example 8]
Example 1 and Example 5 except that 23.0 parts of 2-aminonaphthothiazole-6,8-disulfonic acid was replaced with 26.0 parts of 2-amino-7-methoxybenzothiazole-6-sulfonic acid. , 68.1 parts of a compound represented by the formula (31) were obtained. The maximum absorption wavelength of the compound in a 20% aqueous pyridine solution was 675 nm.

[Example 9]
40.6 parts of monoazo compound represented by the formula (47) was obtained in the same manner as in Example 1 except that 15.3 parts of 2,5-dimethoxyaniline was replaced with 13.7 parts of 2-methoxy-5-methylaniline. It was.

  In the same manner as in Example 5 except that 41.9 parts of the compound represented by the formula (46) are replaced with a compound represented by 40.6 parts of the compound represented by the formula (47), the compound represented by the formula (32) is represented. To obtain 77.6 parts of the disazo compound. The maximum absorption wavelength of the compound in a 20% aqueous pyridine solution was 685 nm.

[Production Example 1: Polarizing film]
Polyvinyl alcohol having a thickness of 75 μm was soaked for 4 minutes in a staining solution comprising a 45 ° C. aqueous solution containing 0.03% of the compound of formula (5) obtained in Example 1 and 0.1% of sodium sulfate. . This film was stretched 5 times at 50 ° C. in a 3% boric acid aqueous solution, washed with water and dried while maintaining a tensioned state to obtain a polarizing film.

[Preparation Examples 2 to 9, Comparative Example 1: Polarizing Film]
Instead of the compound of the formula (5), the formulas (6), (11), (14), (16), (17), (28), (31), (32) obtained in Examples 2 to 9 were used. A polarizing film was obtained in the same manner as in Production Example 1 except that the azo compound (1) was used. As a comparative example, a polarizing film was obtained in the same manner as in the preparation example of the present invention using the compound of the formula (III-1) described in Example 1 of Patent Document 6.

(Measurement of maximum absorption wavelength and polarization rate of polarizing film)
Regarding the polarizing films obtained in Production Examples 1 to 9 and Comparative Example 1 of the polarizing film, the maximum absorption wavelength and the polarization rate were measured. The measurement of the maximum absorption wavelength of the polarizing film and the calculation of the polarization rate were calculated by measuring the parallel transmittance and orthogonal transmittance at the time of incidence of polarized light using a spectrophotometer (manufactured by Hitachi, Ltd .; U-4100). Here, the parallel transmittance (Ky) is the transmittance when the absorption axis of the absolute polarizer and the absorption axis of the polarizing film are parallel, and the orthogonal transmittance (Kz) is the absorption axis of the absolute polarizer and the polarizing film. The transmittance when the absorption axis is orthogonal is shown. The parallel transmittance and orthogonal transmittance of each wavelength were measured at 1 nm intervals at 380 to 900 nm. Using each measured value, the polarization rate of each wavelength was calculated from the following formula (i), and the largest polarization rate at 380 to 900 nm and the absorption wavelength (nm) at that time were obtained. The results are shown in Table 1.

Polarization rate (%) = [(Ky−Kz) / (Ky + Kz)] × 100 (i)

  As shown in Table 1, polarizing films prepared using these compounds had a maximum absorption wavelength on the long wavelength side in the visible light region of about 680 to 740 nm, and all had a high polarization rate.

(Measurement of color of polarizing film)
Using the compound of formula (III-1) described in Example 1 of Patent Document 6 so that the polarizing film has the same transmittance as the polarizing film of Preparation Example 3 using the compound of formula (11) The polarizing films thus prepared were subjected to chromaticity measurement at the parallel time and at the orthogonal time with the above spectrophotometer. The results are shown in Table 2.

If the b ^* value is a positive value, it will be yellow, and if it is a negative value, it will be blue. Originally, if the polarizing film has a maximum absorption wavelength near 610 nm, the b ^* value will be a negative value when parallel and orthogonal, but the polarizing film using the compound of formula (11) will have a negative value. It was shown and had the original blue color. On the other hand, the polarizing film using the compound of the comparative example had a positive value and was visually green. From this result, it is shown that the polarizing film using the compound of the formula (11) has little side absorption in a region other than the maximum absorption wavelength, particularly in a region of 500 nm or less, and can be very useful as a blue component of three primary colors. Showing sex.

[Production Example 10: Production Example of Neutral Gray Polarizing Plate]
As a staining solution, 0.2% of the compound of the formula (17), C.I. I. direct. 0.07% orange 39, C.I. I. direct. A polarizing film was produced in the same manner as in Production Example 1 except that a 45 ° C. aqueous solution having a concentration of 0.02% red 81 and 0.1% sodium sulfate was used. The obtained polarizing film had a maximum absorption wavelength of 555 nm, the single plate average transmittance at 380 to 700 nm was 40%, the average light transmittance at orthogonal positions was 0.02%, and had a high degree of polarization. . Furthermore, the transmissivity in the visible light region was almost constant for both parallel and orthogonal positions, and a neutral gray hue was exhibited.
One triacetyl cellulose film (TAC film; manufactured by Fuji Photo Film Co., Ltd .; trade name TD-80U) was laminated on both surfaces of this polarizing film with an adhesive of an aqueous polyvinyl alcohol solution. Next, an AR support (manufactured by NOF Corp .; Realak X4010) was laminated on one TAC film using an adhesive to obtain a neutral gray dye-based polarizing plate with an AR support. Like the polarizing film, the obtained polarizing plate exhibited a neutral gray hue and had a high polarization rate.
Furthermore, although data are not shown, the obtained polarizing plate showed durability for a long time even in a high temperature and high humidity state, and was excellent in light resistance against long-time exposure.

Claims (15)

Following formula (1):

(In the formula, A ₁ and A ₂ are each independently a hydrogen atom or the following formula (2):

(In the formula, the ring substituted by R ₁ and the sulfo group is a benzothiazole ring when a ring represented by a broken line is not present, and a naphthothiazole ring when a ring represented by a broken line is present. R ₁ is a chlorine atom, a sulfo group, a nitro group, a hydroxy group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an alkyl group having 1 to 4 carbon atoms having a sulfo group, hydroxy A C1-C4 alkyl group having a group, a C1-C4 alkyl group having a carboxy group, a C1-C4 alkoxy group having a sulfo group, a C1-C4 alkoxy group having a hydroxy group And a group consisting of a C 1-4 alkoxy group having a carboxy group,
B is a phenylene group or naphthylene group which may have a substituent, and the substituent is a chlorine atom, a sulfo group, a nitro group, a hydroxy group, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms. An alkyl group having 1 to 4 carbon atoms having a sulfo group, an alkyl group having 1 to 4 carbon atoms having a hydroxy group, an alkyl group having 1 to 4 carbon atoms having a carboxy group, and an alkyl group having 1 to 4 carbon atoms having a sulfo group Selected from the group consisting of an alkoxy group, an alkoxy group having 1 to 4 carbon atoms having a hydroxy group, and an alkoxy group having 1 to 4 carbon atoms having a carboxy group (in the case where there are a plurality of them, each independently)
m is an integer of 1 to 3)
Except that A ₁ and A ₂ are both hydrogen atoms,
(The two bonds of -NH- are each independently bonded to the substitution position indicated by a or b)
Or a salt thereof. Formula (2) is the following formula (3):

(Wherein R _1a is a substituted ring, and R _1a represents the same as R ₁ in formula (2);
R ₂ and R ₃ are each independently a hydrogen atom, a chlorine atom, a sulfo group, a nitro group, a hydroxy group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a carbon number 1 to 1 having a sulfo group. 4 alkyl groups, hydroxy groups having 1 to 4 carbon atoms, carboxyl groups having 1 to 4 carbon atoms, sulfo groups having 1 to 4 carbon atoms, hydroxy groups having carbon atoms Selected from the group consisting of 1-4 alkoxy groups and C 1-4 alkoxy groups having a carboxy group;
m ₁ represents the same meaning as m in formula (2)),
Or following formula (4):

(R _1b in the formula is substituted, and R _1b is the same as R ₁ in formula (2),
R _{4 to} R ₆ are each independently a hydrogen atom, a chlorine atom, a sulfo group, a nitro group, a hydroxy group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or a carbon number 1 to 1 having a sulfo group. 4 alkyl groups, hydroxy groups having 1 to 4 carbon atoms, carboxyl groups having 1 to 4 carbon atoms, sulfo groups having 1 to 4 carbon atoms, hydroxy groups having carbon atoms Selected from the group consisting of 1-4 alkoxy groups and C 1-4 alkoxy groups having a carboxy group;
m ₂ represents the same meaning as m in formula (2))
The azo compound or its salt of Claim 1 represented by these. The azo compound or a salt thereof according to claim 2, wherein A ₁ and A ₂ are each independently represented by formula (3) or formula (4). The azo compound or a salt thereof according to claim 2, wherein A ₁ is represented by formula (3) or (4), and A ₂ is a hydrogen atom. R _1b in Formula (4) is a hydrogen atom, a chlorine atom, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms, and R _{4 to} R ₆ are each independently a hydrogen atom or carbon number. The azo compound or a salt thereof according to any one of claims 2 to 4, which is an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms which may have a sulfo group. R _1a in formula (3) is a hydrogen atom, a chlorine atom or an alkyl group having 1 to 4 carbon atoms, and R ₂ and R ₃ are each independently a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, or a sulfo group. The azo compound or a salt thereof according to any one of claims 2 to 5, which is an alkoxy group having 1 to 4 carbon atoms which may contain   The azo compound or a salt thereof according to any one of claims 1 to 6, wherein the -NH-substitution position in formula (1) is a.   A dye-based polarizing film comprising the azo compound or a salt thereof according to claim 1 and a polarizing film substrate.   A dye-based polarizing film comprising at least one kind of the azo compound or a salt thereof according to any one of claims 1 to 7 and an organic dye other than the azo compound and a polarizing film substrate.   A dye-based polarizing film comprising two or more types of the azo compound according to claim 1 or a salt thereof, one or more types of organic dyes other than these, and a polarizing film substrate.   The dye-type polarizing film in any one of Claims 8-10 whose polarizing film base material is a film formed from polyvinyl alcohol resin or its derivative (s).   The dye type polarizing plate obtained by bonding a transparent protective layer to at least one surface of the dye type polarizing film in any one of Claims 8-11.   A liquid crystal display device comprising the dye-based polarizing film according to claim 8 or the dye-based polarizing plate according to claim 12.   The dye-type polarizing film according to any one of claims 8 to 11, which exhibits neutral gray.   A vehicle-mounted display device or an outdoor display device comprising the dye-based polarizing plate according to claim 14 or a dye-based polarizing plate obtained by bonding a transparent protective layer to at least one surface of the dye-based polarizing film.