TWI822935B - Azo compound or salt thereof, and dye-based polarizing film and dye-based polarizing plate containing the same - Google Patents

Abstract

Provided is an azo compound represented by the following formula (1) or a salt thereof,

wherein, in the formula (1),

A¹ represents a phenyl group which may have a substituent, or a heterocyclic group which may have a substituent,

A², A³ and A⁴ each independently represent a phenyl group which may have a substituent or a naphthyl group which may have a substituent,

R¹ represents a hydrogen atom, a hydroxy group, a C1 to 4 alkoxy group, a substituted or unsubstituted amino group,

m represents an integer of 0 to 5,

M represents a hydrogen atom or ion, a metal ion, or an ammonium ion,

n represents 1 or 2,

k represents 0 or 1, and

hydrogen atoms of ring a and ring b may be substituted with substituent R¹ and substituent SO₃M.

Description

Azo compounds or salts thereof, and dye-based polarizing films and dye-based polarizing plates containing the compounds or salts thereof

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

Polarizing plates with light transmission and shielding functions are used in display devices such as liquid crystal displays (LCDs) together with liquid crystals with light switching functions. The applicable fields of this LCD have also gradually expanded from the early commercial electronic calculators, clocks and other small machines to notebook computers, word processors, LCD projectors, LCD TVs, car navigation and indoor and outdoor information display devices, and measuring machines. wait. In addition, it can also be applied to lenses with polarizing functions, and has been used in sunglasses with improved visibility, and in recent years, polarized glasses corresponding to 3D TVs, etc. In addition, it is not only used in displays, but also in applications for improving accuracy in authenticity judgment devices, and in image sensors such as CCD and CMOS, which cut off reflected light to improve the signal-to-noise (S/N) ratio. .

Generally, polarizing plates are made by dyeing or containing iodine or dichroic dyes as polarizing elements in a polarizing film base material. The polarizing film base material is a film of polyvinyl alcohol or its derivatives that has been stretched and aligned. Or a polyene-based film that is aligned through the dehydrochlorination reaction of a polyvinyl chloride film or the dehydration of a polyvinyl alcohol-based film to generate polyene. Among these, iodine-based polarizing films that use iodine as a polarizing element have excellent polarizing properties, but are weak to water and heat, and have problems with durability when used under high temperature and high humidity conditions for a long time. . On the other hand, dye-based polarizing films using dichroic dyes as polarizing elements have excellent moisture resistance and heat resistance compared with iodine-based polarizing films, but generally have insufficient polarizing performance.

In recent years, in applications such as identification light sources for touch panels, surveillance cameras, sensors, anti-counterfeiting, and communication equipment, polarizing plates for not only the visible light wavelength range (visible range) but also the infrared wavelength range have been required. (infrared area) polarizing plate. In order to respond to these demands, there are the following descriptions: an infrared polarizing plate using an iodine-based polarizing plate that has been polyolefinized in Patent Document 1, an infrared polarizing plate using a wire grid such as Patent Document 2 or 3, For example, Patent Document 4 discloses an infrared polarizer stretched from glass containing microparticles, and Patent Document 5 or 6 uses a cholesteric liquid crystal. In Patent Document 1, durability, heat resistance, wet heat durability, and light resistance are weak, and practicality is poor. For example, the wire grid type in Patent Document 2 or 3 can be processed into a film type and is gradually popularized because it is stable as a product. However, if the surface does not have nanoscale unevenness, the optical properties cannot be maintained and the surface cannot be contacted, so the uses are limited, and it is difficult to perform anti-reflective and anti-glare (anti-glare) processing. As in Patent Document 4, a glass elongated type containing fine particles has high durability and has high dichroism, so it has good practicality. However, since it is a glass that contains fine particles and stretches at the same time, the element itself is fragile and fragile. Moreover, it lacks flexibility like conventional polarizing plates, so it has problems such as surface processing and bonding with other substrates. The technologies of Patent Document 5 and Patent Document 6 use circular polarization technology that has been disclosed in the past. However, since the color changes depending on the viewing angle and they are basically polarizing plates that utilize reflection, stray light is generated and absolute polarization is difficult to form. That is, there is still no absorption-type polarizing element like a common iodine-based polarizing plate that is as flexible as a film type and has high durability corresponding to the infrared region. Light board. This is because the dichroic dyes used in these applications only absorb in the visible region and cannot absorb in the infrared region.

As pigments and dyes that absorb in the infrared region, there are diimmonium pigments, naphthalocyanine pigments, cyanine pigments, etc. However, these pigments are weak in durability and Very few people show dichromatism. In addition, even though azo dyes are highly durable, there are very few dyes that absorb in the infrared region. Among azo dyes, dyes that absorb in the infrared region include, for example, the dyes described in Patent No. 4244243. However, there is no description of its dichroism. In the examples, N,N-dimethylformamide (hereinafter referred to as DMF) medium was used, and its important use as a polarizing plate and its solubility in water have not yet been revealed. Absorption of near-infrared light in aqueous media.

In particular, it is known that among general water-soluble azo dyes, their absorption wavelengths in aqueous media are different from those in other media. For example, compound (I-1) of Japanese Unexamined Patent Application No. 2007-84803 shows a maximum absorption of 406 nm in aqueous solution. The wavelength, however, is 440nm in the polyvinyl alcohol film, and it is known that the absorption wavelength changes depending on the medium. That is, it has been found that the absorption wavelength shown in the state of being dissolved or dispersed in a medium is different from the absorption wavelength shown in the state of dichroism, that is, the state of polarizing function. Accordingly, among water-soluble azo compounds, there is a need for dyes that absorb in the infrared region in water or in hydrophilic polymers important for polarizing plate applications.

[Prior technical literature]

[Patent Document]

[Patent Document 1] US2,494,686

[Patent Document 2] Japanese Patent Application Publication No. 2016-148871

[Patent Document 3] Japanese Patent Application Publication No. 2013-24982

[Patent Document 4] Japanese Patent Application Publication No. 2004-86100

[Patent Document 5] International Publication No. 2015/087709

[Patent Document 6] Japanese Patent Application Publication No. 2013-64798

[Patent Document 7] Japanese Patent Application Laid-Open No. 2-167791

[Patent Document 8] International Publication No. 2013/035560

[Patent Document 9] Japanese Patent Application Publication No. Sho 63-33477

[Non-patent literature]

[Non-patent document 1] "Dye Chemistry"; written by Toyo Hosoda, Gihodo Publishing Co., Ltd., 1957, page 621

One object of the present invention is to provide a novel azo compound. Another object of the present invention is to provide a novel dichroic dye azo compound and a polarizing film containing the compound. Another object of the present invention is to provide a water-soluble dichroic dye azo compound that absorbs in the infrared region, and a polarizing film that exhibits a polarizing function for infrared light containing the compound.

The inventors of the present invention have discovered a novel azo compound as a result of intensive research to achieve these objectives. Furthermore, it was novelly discovered that a film containing the azo compound can function as a polarizing plate by aligning the azo compound. Furthermore, it was discovered that, in one aspect of the present invention, a polarizing plate containing a novel azo compound with absorption in the infrared region can act on infrared light.

That is, the present invention relates to the following.

[Invention 1]

An azo compound or a salt thereof, the azo compound is represented by the following formula (1),

式(1)中，

In formula (1),

A ¹ represents a phenyl group which may have a substituent, or a heterocyclic group which may have a substituent,

A ² , A ³ and A ⁴ each independently represent a phenyl group which may have a substituent or a naphthyl group which may have a substituent,

R ¹ represents a hydrogen atom, a hydroxyl group, a C1 to 4 alkoxy group, a substituted or unsubstituted amine group,

m represents an integer from 0 to 5,

M represents hydrogen atom or ion, metal ion, or ammonium ion,

n means 1 or 2,

k represents 0 or 1,

The hydrogen atoms of ring a and ring b may be substituted by substituent R ¹ or substituent SO ₃ M.

[Invention 2]

The azo compound or a salt thereof according to Invention 1, wherein A ¹ in the above formula (1) represents an optionally substituted heterocyclic group.

[Invention 3]

The azo compound or a salt thereof according to Invention 2, wherein the heterocyclic group which may have a substituent is selected from the group consisting of groups represented by the following formulas (2) to (4);

式(2)至(4)中，

In formulas (2) to (4),

Each of 4 aliphatic hydrocarbon group, C1 to 4 aliphatic hydrocarbon group having a carboxyl group, C1 to 4 alkoxy group having a sulfonic acid group, C1 to 4 alkoxy group having a hydroxyl group, C1 to 4 alkoxy group having a carboxyl group base,

q ¹ represents an integer from 0 to 4, q ² represents an integer from 0 to 6,

M represents hydrogen atom or ion, metal ion, or ammonium ion,

n ¹ and n ² each represent an integer from 0 to 3,

In each formula, * represents the bonding position with the azo bond.

[Invention 4]

The azo compound or salt thereof according to any one of Inventions 1 to 3, wherein in the above formula (1), A ² , A ³ and A ⁴ are each independently represented by the following formula (5) or formula (6) ), at least one of A ² , A ³ and A ⁴ is represented by formula (5);

式(5)中，

In formula (5),

R ² represents a hydrogen atom, a hydroxyl group, a C1 to 4 aliphatic hydrocarbon group, a C1 to 4 alkoxy group, a substituted or unsubstituted amino group, or a C1 to 4 alkoxy group having a sulfonic acid group,

m ² represents an integer from 0 to 6,

M represents hydrogen atom or ion, metal ion, or ammonium ion,

n ³ represents an integer from 0 to 2;

式(6)中，

In formula (6),

R ¹¹ and R ¹² each independently represent a hydrogen atom, a C1 to 4 aliphatic hydrocarbon group, a C1 to 4 alkoxy group, a C1 to 4 alkoxy group having a hydroxyl group, or a C1 to 4 alkoxy group having a sulfonic acid group. base.

[Invention 5]

The azo compound or salt thereof according to invention 1, wherein the above formula (1) is represented by the following formula (7),

式(7)中，

In formula (7),

A ⁵ is the same as A ¹ in the above formula (1),

R ³ and R ⁴ each independently represent a hydrogen atom, a hydroxyl group, a C1 to 4 alkoxy group, a substituted or unsubstituted amine group,

m ³ and m ⁴ each represent an integer from 0 to 5,

M represents hydrogen atom or ion, metal ion, or ammonium ion,

n ⁴ means 1 or 2.

[Invention 6]

The azo compound or salt thereof according to invention 1, wherein the above formula (1) is represented by the following formula (8),

式(8)中，

In formula (8),

A ⁶ is the same as A ¹ in the above formula (1),

R ⁵ , R ⁶ , and R ⁷ each independently represent a hydrogen atom, a hydroxyl group, a C1 to 4 alkoxy group, or a substituted or unsubstituted amine group,

m ⁵ to m ⁷ each represent an integer from 0 to 5,

M represents hydrogen atom or ion, metal ion, or ammonium ion,

n ⁵ means 1 or 2.

[Invention 7]

The azo compound or salt thereof according to invention 1, wherein the above formula (1) is represented by the following formula (9),

式(9)中，

In formula (9),

R ⁸ , R ⁹ and R ¹⁰ each independently represent a hydrogen atom, a hydroxyl group, a C1 to 4 alkoxy group, a substituted or unsubstituted amine group,

m ⁸ to m ¹⁰ each represent an integer from 0 to 5,

M represents a hydrogen atom or ion, a metal ion, or an ammonium ion, and n ⁶ represents 1 or 2.

[Invention 8]

A polarizing film containing at least one of the azo compound or salt thereof according to any one of Inventions 1 to 7.

[Invention 9]

The polarizing film _of invention 8, wherein the absorbance ratio Rd _{(=A H /} A _L ) At least one of the wavelengths showing a value of 5 or more is between 700 and 1500 nm.

[Invention 10]

The polarizing film according to Invention 8 or 9, which contains the azo compound or salt thereof according to any one of Inventions 1 to 7, and one or more organic dyes other than the azo compound or salt thereof.

[Invention 11]

The polarizing film according to any one of Inventions 8 to 10, which displays neutral gray.

[Invention 12]

The polarizing film according to any one of Inventions 8 to 11, wherein a film containing polyvinyl alcohol resin or a derivative thereof is used as the base material.

[Invention 13]

A polarizing plate provided with a transparent protective layer on at least one side of the polarizing film according to any one of Inventions 8 to 12.

[Invention 14]

A display device using the polarizing film according to any one of Inventions 8 to 12 or the polarizing plate according to Invention 13.

[Invention 15]

The display device according to invention 14 is for vehicle or outdoor display use.

The azo compound or its salt of the present invention can be used as a dye for polarizing films. In one aspect, the azo compound or salt thereof of the present invention is water-soluble. In one aspect, the azo compound or salt thereof of the present invention is dichroic. In one aspect, the polarizing film or polarizing plate of the present invention has absorption in the infrared region, and can be treated in the same manner as the conventional polarizing film or polarizing plate for light used in the infrared region. In one aspect, the polarizing film or polarizing plate of the present invention is flexible. In one aspect, the polarizing film or polarizing plate of the present invention is physically stable. In one aspect, since the polarizing film or polarizing plate of the present invention is an absorptive polarizing plate, no stray light is generated. In one aspect, the polarizing film or polarizing plate of the present invention has high weather resistance (at least one of heat resistance, moisture and heat resistance, and light resistance).

The present invention relates to a novel azo compound or a salt thereof, and its further object is to use the dye to dye, extend and orient a film and exhibit anisotropic absorption. The infrared region generally refers to 700 to 30000nm, but the polarizing film containing the compound obtained by the present invention, It functions as a polarizing film for near-infrared rays, and the wavelength of near-infrared rays refers to the wavelength of 700 to 1500 nm, and becomes a polarizing film that exhibits polarizing function at this wavelength.

<Azo compound or its salt>

The azo compound or salt thereof of the present invention is represented by the above formula (1).

In the above formula (1), A ¹ represents a phenyl group which may have a substituent or a heterocyclic group which may have a substituent, and A ² , A ³ and A ⁴ each independently represent a phenyl group which may have a substituent or a heterocyclic group which may have a substituent. Naphthyl group with a substituent, R ¹ represents a hydrogen atom, a hydroxyl group, a (C1 to 4) alkoxy group having 1 to 4 carbon atoms, a substituted or unsubstituted amino group, m represents an integer from 0 to 5, and M represents a hydrogen atom or ion, metal ion, or ammonium ion, n represents 1 or 2, k represents 0 or 1, and the hydrogen atoms of ring a and ring b may be substituted by substituent R ¹ or substituent SO ₃ M.

In the above-mentioned ^A1 , the substituent of the phenyl group which may have a substituent is not particularly limited, but examples thereof include: an aliphatic hydrocarbon group of C1 to 4 which may have a substituent; an alkyl group of C1 to 4 which may have a substituent. Oxygen group, C1 to 4 alkoxy group which may have a sulfonic acid group, aryloxy group which may have a substituted group, hydroxyl group, sulfonic acid group, carboxyl group, nitro group, substituted or unsubstituted amino group, amide group, etc., Preferably, the substituent is selected from the group consisting of C1 to 4 alkoxy groups, sulfonic acid groups, nitro groups, and carboxyl groups that may have substituents.

Examples of the C1 to C4 aliphatic hydrocarbon group which may have a substituent include: linear aliphatic hydrocarbon groups such as methyl, ethyl, n-propyl, n-butyl; isopropyl, secondary butyl, tertiary butyl, etc. Branched aliphatic hydrocarbon groups such as butyl; cyclic aliphatic hydrocarbon groups such as cyclobutyl.

Examples of the C1 to C4 alkoxy group which may have a substituent include: methoxy, ethoxy, n-propoxy, n-butoxy, isopropoxy, secondary butoxy, tertiary Butoxy, cyclobutoxy, etc.

Examples of the C1 to C4 alkoxy group which may have a sulfonate group include: sulfonate methoxy group, sulfonate ethoxy group, 3-sulfonate propoxy group, and 4-sulfonate butoxy group. base, 3-sulfonate butoxy group, etc.

Examples of the above-mentioned aryloxy group which may have a substituent include a phenoxy group, a naphthyloxy group, and the like.

Examples of the substituted or unsubstituted amino group include monosubstituted amino groups such as amino group, methylamino group, ethylamine group, n-propylamine group, n-butylamino group, monoanilino group, mononaphthylamine group, etc. Disubstituted amino groups such as methylamino group, diethylamine group, diphenylamine group, N-ethyl-N-methylamino group, N-ethyl-N-anilino group, etc. In addition, these substituted amine groups may further have substituents.

The "substituent" in the C1 to C4 aliphatic hydrocarbon group which may have a substituent and the C1 to C4 alkoxy group which may have a substituent is not particularly limited, and examples thereof include: hydroxyl group, sulfonic acid group, carboxyl group , the above-mentioned substituted or unsubstituted amine group, amide group, etc.

The "substituent" in the above-mentioned aryloxy group which may have a substituent and the "substituent" which the substituted amino group may have are not particularly limited, and examples thereof include: C1 to 4 aliphatic hydrocarbon groups which may have a substituent. .

The phenyl group which may have a substituent in the above A ¹ is more preferably a group selected from the group consisting of a sulfonic acid group, a carboxyl group, a C1 to 4 alkoxy group having a sulfonic acid group, a C1 to 4 aliphatic hydrocarbon group, and a C1 to 4 alkyl group. At least one substituent selected from the group consisting of an oxygen group, a halogen atom, a nitro group, an amino group, a C1 to 4 aliphatic hydrocarbon-substituted amine group, and a C1 to 4 aliphatic hydrocarbon-substituted acylamino group. phenyl.

In the case where the phenyl group has two or more substituents, at least one of these substituents is a sulfonic acid group, or a nitro group, or a carboxyl group, or a C1 to 4 alkoxy group having a sulfonic acid group, and the others are The substituent is preferably a sulfonic acid group, a nitro group, a C1 to 4 aliphatic hydrocarbon group, a C1 to 4 alkoxy group, a C1 to 4 alkoxy group having a sulfonic acid group, a carboxyl group, a chlorine group, a bromo group, a nitro group group, amino group, C1 to C4 aliphatic hydrocarbon substituted amino group, or C1 to C4 aliphatic hydrocarbon substituted acylamine group. Other substituents are preferably sulfonate group, methyl, ethyl, methoxy, ethoxy, carboxyl, sulfonate ethoxy, sulfonate propoxy, sulfonate butoxy, chlorine group , Nitro or amino group, preferably sulfonate, carboxyl, nitro, methyl, methoxy, sulfonateethoxy, sulfonatepropoxy, or sulfonatebutoxy, especially It is a sulfonate group, carboxyl group, nitro group, methyl group, methoxy group, sulfonate butoxy group.

In the above-mentioned phenyl group that may have a substituent in A ¹ , the position of the substituent is not particularly limited, but it is preferably only the 2-position, only the 4-position, a combination of the 2-position and the 6-position, or a combination of the 2-position and the 4-position. , the combination of 3 and 5 digits is better, and the best is only 2 digits, only 4 digits, a combination of 2 and 4 digits, or a combination of 3 and 5 digits. In addition, only the 2nd position and only the 4th position means that only the 2nd or 4th position has a substituent other than one hydrogen atom.

Preferable examples of A ¹ mentioned above, when the azo bond is at the 1-position, include a phenyl group having a sulfonic acid group at the 2-position, a nitro group at the 4-position, and a carboxyl group each at the 3-position and 5-position. phenyl.

The above-mentioned A ¹ preferably represents a heterocyclic group which may have a substituent.

唑基、咪唑基、噻吩基、呋喃基、吡咯基、噻二唑基、吡唑基、吡啶基、哌

基、喹啉基、苯并咪唑基、萘并咪唑基、苯并噻唑基、萘并噻唑基、苯并噻二唑基等，較佳係苯并噻唑基或萘并噻唑基，其中，更佳係選自由後述之上述式(2)至(4)所示之基所構成之群組的基。 Examples of the heterocyclic group which may have a substituent include: thiazolyl,

Azolyl, imidazolyl, thienyl, furyl, pyrrolyl, thiadiazolyl, pyrazolyl, pyridyl, piperazolyl

base, quinolyl, benzimidazolyl, naphthimidazolyl, benzothiazolyl, naphthothiazolyl, benzothiadiazolyl, etc., preferably benzothiazolyl or naphthothiazolyl, among which, more Preferably, the group is selected from the group consisting of groups represented by the above formulas (2) to (4) described below.

The "substituent" in the above-mentioned heterocyclic group which may have a substituent is not particularly limited, and may be the same as the substituent which the above-mentioned C1 to 4 aliphatic hydrocarbon group which may have a substituent may have, and preferably has a sulfonic acid group as a substituent.

In the above formula (1), A ² , A ³ and A ⁴ each independently represent a phenyl group which may have a substituent or a naphthyl group which may have a substituent. The phenyl group which may have a substituent may be the same as those described in the above-mentioned item ^A1 . In the naphthyl group which may have a substituent, the substituent is not particularly limited and may be the same as the substituent that the C1 to 4 aliphatic hydrocarbon group which may have a substituent mentioned above may have. As will be described later, in the above formula (1), it is preferable that A ² , A ³ and A ⁴ are each independently represented by the above formula (5) or formula (6), and at least one of A ² , A ³ and A ⁴ is A system is shown in equation (5).

In the above formula (1), R ¹ represents a hydrogen atom, a hydroxyl group, a C1 to 4 alkoxy group, or a substituted or unsubstituted amine group.

In the above formula (1), M represents a hydrogen atom or ion, a metal ion, or an ammonium ion. Examples of metal ions include alkali metal ions such as lithium ions, sodium ions, and potassium ions, and alkaline earth metal ions such as calcium ions and magnesium ions. Examples of ammonium ions include ammonium ions, methylammonium ions, dimethylammonium ions, triethylammonium ions, tetraethylammonium ions, tetra-n-propylammonium ions, tetra-n-butylammonium ions, triethanolammonium ions, etc. . More specifically, for example, when M is a hydrogen atom or ion, it represents sulfonic acid (-SO ₃ H), and when M is a sodium ion, it represents sodium sulfonate (-SO ₃ Na). When M is an ammonium ion, it represents ammonium sulfonate (-SO ₃ NH ₄ ).

The hydrogen atoms of ring a and ring b in the above formula (1) may be substituted by the above substituent (R ¹ ) or the above substituent (-SO ₃ M).

In the above formula (1), it is preferred that any one or both of ring a and ring b are substituted with a sulfonic acid group. In addition, those in which ring b is substituted by a hydroxyl group are also preferred. Among them, when the azo bonding portion of ring a is located at position 1, particularly preferred ones are: those in which position 2 is substituted with a hydroxyl group in the counterclockwise direction, those in which positions 3 and 7 are substituted with sulfonic acid groups, and those in which position 4 is substituted. Those at position 2 are substituted with a sulfonic acid group, those at the 2nd position are substituted with a hydroxyl group, those at the 4th position are substituted with a sulfonic acid group, and those at the 7th position are substituted with a sulfonic acid group.

In the above formulas (2) to (4), to 4 aliphatic hydrocarbon groups, C1 to 4 aliphatic hydrocarbon groups having a hydroxyl group, C1 to 4 aliphatic hydrocarbon groups having a carboxyl group, C1 to 4 alkoxy groups having a sulfonic acid group, C1 to 4 alkyl groups having a hydroxyl group Oxygen group, or C1 to 4 alkoxy group having a carboxyl group, q ¹ represents an integer from 0 to 4, q ² represents an integer from 0 to 6, M represents a hydrogen atom or ion, metal ion, or ammonium ion, n ¹ , n ² each represents an integer from 0 to 3. In each formula, * represents the bonding position with the azo bond, a C1 to 4 aliphatic hydrocarbon group, a C1 to 4 alkoxy group, and a C1 to 4 aliphatic group with a sulfonic acid group. The hydrocarbon group, the C1 to C4 alkoxy group having a sulfonic acid group, and M may each be the same as above.

Examples of the halogen group include a fluorine group, a chlorine group, a bromine group, an iodine group, and the like, and a chlorine group and a bromine group are preferred, and a chlorine group is more preferred.

Examples of the C1 to C4 aliphatic hydrocarbon group having a hydroxyl group include: hydroxymethyl, hydroxyethyl, hydroxy-n-propyl, hydroxy-n-butyl, hydroxyisopropyl, hydroxy-secondary butyl, hydroxyl -Tertiary butyl etc.

Examples of the C1 to C4 aliphatic hydrocarbon group having a carboxyl group include: carboxymethyl, carboxyethyl, carboxyl-n-propyl, carboxyl-n-butyl, carboxyisopropyl, carboxyl-secondary butyl, carboxyl -Tertiary butyl etc.

Examples of the C1 to C4 alkoxy group having a hydroxyl group include: hydroxymethoxy, hydroxyethoxy, hydroxy-n-propoxy, hydroxy-n-butoxy, hydroxyisopropoxy, hydroxy-di Grade butoxy, hydroxyl-tertiary butoxy, etc.

Examples of the C1 to C4 alkoxy group having a carboxyl group include: carboxyl methoxy group, carboxyl ethoxy group, carboxyl-n-propoxy group, carboxyl-n-butoxy group, carboxyl isopropoxy group, carboxyl-di Grade butoxy, carboxyl-tertiary butoxy, etc.

In the above formula (1), A ² , A ³ , and A ⁴ each independently represent the above formula (5) or formula (6), and at least one of A ² , A ³ , and A ⁴ is represented by the formula (5). , which is better because a wide-band polarizing element can be obtained.

In the above formula (5), R ² represents a hydrogen atom, a hydroxyl group, a C1 to 4 aliphatic hydrocarbon group, a C1 to 4 alkoxy group, a substituted or unsubstituted amino group, or a C1 to 4 group having a sulfonic acid group. Alkoxy group, m ² represents an integer from 0 to 6, M represents a hydrogen atom or ion, metal ion, or ammonium ion, n ³ represents an integer from 0 to 2, aliphatic hydrocarbon group with C1 to 4, alkoxy group with C1 to 4 The group, the substituted or unsubstituted amino group, the C1 to C4 alkoxy group having a sulfonic acid group, and M may each be the same as above.

In the above formula (5), m ² preferably represents an integer from 0 to 4, more preferably an integer from 0 to 2, and particularly preferably 0 or 1. R ² preferably represents a hydrogen atom or a hydroxyl group. n ³ preferably represents 0 or 1, more preferably represents 1, when the azo group on the side of A ¹ in formula (1), A ⁵ in formula (7), and A ⁶ in formula (8) is located at the 1 position When, the substitution position of R ² is preferably the 2nd, 3rd, or 5th position. Particularly preferably, the 2- or 3-position is substituted by a hydrogen atom or a methoxy group, and particularly preferably, the 3-position is substituted. The 8-position is preferably substituted by a hydrogen atom or a hydroxyl group, and particularly preferably, it is substituted by a hydroxyl group. In the above formula (1), A ³ and A ⁴ preferably have the structure shown in formula (5). This is because the azo compound of the present invention is used to obtain a polarizing film with a high degree of polarization for a wide band. of pigments. Specifically, the best ones are when k=0, A ³ has the structure of formula (5), and when k=1, A ⁴ has the structure of formula (5).

In the above formula (6), R ¹¹ and R ¹² each independently represent a hydrogen atom, a C1 to 4 aliphatic hydrocarbon group, a C1 to 4 alkoxy group, a C1 to 4 alkoxy group having a hydroxyl group, or a sulfonate group. C1 to 4 alkoxy group of acid group, C1 to 4 aliphatic hydrocarbon group, C1 to 4 alkoxy group, C1 to 4 alkoxy group with hydroxyl group, C1 to 4 alkoxy group with sulfonic acid group Each can be the same as above.

In the above formula (1), when A ³ and A ⁴ have the structure shown in formula (6), it is preferable that R ¹¹ or R ¹² each independently represents a hydrogen atom or an alkoxy group with C1 to 4. This is because The azo compound of the present invention is a pigment used to obtain a polarizing film with a wide band and high polarization degree. It is more preferred that each of the azo compounds independently represents a methoxy group or an ethoxy group. It is particularly preferred that R ¹¹ and R ¹² represent a methoxy group. base. Specifically, when k=0 and A ³ has the structure of formula (6), R ¹¹ and R ¹² preferably represent a methoxy group. When k = 1 and A ⁴ has the structure of formula (6), R ¹¹ and R ¹² Tejia means methoxy.

The above formula (1) is preferably represented by the above formula (7). In the above formula (7), A ⁵ is the same as A ¹ in the above formula (1), and R ³ and R ⁴ each independently represent a hydrogen atom, a hydroxyl group, a C1 to 4 alkoxy group, a substituted or unsubstituted As for the amino group, m ³ and m ⁴ each represent an integer from 0 to 5. M represents a hydrogen atom or ion, a metal ion, or an ammonium ion, and n ⁴ represents 1 or 2. Each of the C1 to C4 alkoxy group, the substituted or unsubstituted amino group, and M may be the same as above. The above formula (1) is preferably represented by formula (7). This is because a near-infrared polarizing film with a wider frequency band and high polarization degree can be obtained.

The above formula (1) is preferably represented by the above formula (8). In the above formula (8), A ⁶ is the same as A ¹ in the above formula (1), and R ⁵ , R ⁶ , and R ⁷ each independently represent a hydrogen atom, a hydroxyl group, a C1 to 4 alkoxy group, a substituted or For unsubstituted amino groups, m ⁵ to m ⁷ each represent an integer from 0 to 5. M represents a hydrogen atom or ion, a metal ion, or an ammonium ion, and n ⁵ represents 1 or 2. Each of the C1 to C4 alkoxy group, the substituted or unsubstituted amino group, and M may be the same as above. The above formula (1) is preferably represented by formula (8), because a near-infrared polarizing film with a wider frequency band and high polarization degree can be obtained.

The above-mentioned formula (1) may also be preferably represented by the above-mentioned formula (9). In the above formula (9), R ⁸ , R ⁹ , and R ¹⁰ each independently represent a hydrogen atom, a hydroxyl group, a C1 to 4 alkoxy group, a substituted or unsubstituted amino group, and m ⁸ to m ¹⁰ each represent 0 to 5. is an integer, M represents a hydrogen atom or ion, a metal ion, or an ammonium ion, n ⁶ represents 1 or 2, and the C1 to 4 alkoxy group, substituted or unsubstituted amino group, and M can each be the same as above. The above formula (1) is preferably represented by formula (9). This is because a near-infrared polarizing film with a wider frequency band and high polarization degree can be obtained.

Next, the following series lists specific examples of the azo compound represented by the above formula (1) or its salt. In addition, the sulfonic acid group, carboxyl group and hydroxyl group in the formula are represented by the form of free acid.

The azo compound represented by the above-mentioned formula (1), formulas (7) to (9) or its salt can be produced by, for example, following the general azo dye manufacturing method described in Patent Document 3 and Non-patent Document 1. , manufactured by diazotization and coupling.

As an example of a specific manufacturing method, the manufacturing method of the above-mentioned formula (7) is demonstrated below.

Diazotizing the following formula (A) belonging to aminebenzenes or thiazoles, and coupling it once with 1-aminonaphthalenes represented by the following formula (B) to obtain the following formula (C) The monoazoamine-based compound shown. The monoazoamine compound (C) is diazotized and secondarily coupled with a 1-aminonaphthalene compound represented by the following formula (D) to obtain a bisphosphonium compound represented by the following formula (E). Azoamine-based compounds. The azo compound of formula (7) is obtained by diazotizing this disazoamine compound (E) and coupling it three times with naphthols of the following formula (F).

In the above-mentioned production method, the diazotization step is preferably performed by a so-called synchronization method in which a nitrite such as sodium nitrite is mixed with a mineral acid aqueous solution or suspension of a diazo component such as hydrochloric acid or sulfuric acid, or by a so-called synchronization method. The so-called reverse method is carried out by adding nitrite to a neutral or weakly alkaline aqueous solution of the diazo component and mixing it with mineral acid. The appropriate temperature for diazotization is -10 to 40°C. In addition, the coupling step with anilines is preferably performed by mixing an acidic aqueous solution such as hydrochloric acid and acetic acid with each of the above diazo liquids under acidic conditions at a temperature of -10 to 40°C and a pH of 2 to 7.

The azo compounds of formula (C) and formula (E) obtained by coupling can be filtered directly, precipitated and filtered by acid precipitation or salt precipitation, or can be directly contacted in the form of a solution or suspension. Down steps. In the case where the diazonium salt is poorly soluble and in suspension, it can be filtered and used as a press cake in the subsequent coupling step.

The third coupling reaction between the diazotide of the disazoamine compound of the above formula (E) and the naphthols represented by the above formula (F) is preferably carried out at a temperature of -10 to 40°C and a pH of 7 to 10 alkaline to alkaline proceed under the conditions. After the reaction is completed, the obtained azo compound or salt of formula (7) is preferably precipitated by salting out, filtered and taken out. In addition, when purification is required, the azo compound can be precipitated from water by repeated salting out or using an organic solvent. Examples of organic solvents used for purification include water-soluble organic solvents such as alcohols such as methanol and ethanol, and ketones such as acetone.

The azo compound or its salt of the present invention can be used as a dye for polarizing films. According to the azo compound or its salt of the present invention, a high-performance dye-based near-infrared polarizing plate with polarizing properties in the near-infrared region and moisture resistance/heat resistance/light resistance can be produced. In addition, by using dyes with polarizing properties in the visible region, a high-performance dye-based polarizing plate that can control neutral gray in not only the current visible region but also the near-infrared region can be realized. Accordingly, the azo compound or its salt of the present invention is suitable for the production of neutral gray polarizing plates for vehicles or outdoor displays used under high-temperature and high-humidity conditions, and various sensors that must control the near-infrared region.

<Dye-based polarizing film>

As the polarizing function, a dichroic ratio calculated from the difference in transmittance, the degree of polarization, or the light absorption ratio (absorbance ratio) in the different axes can usually be used. One of the indicators of polarizing function in this application is polarization degree. However, as a preferred aspect of this application, among the transmittance when polarized light is incident, the axis showing the highest transmittance for polarized light is Among the absorbance ratios of the absorbance and the absorbance of the axis showing the lowest transmittance for polarized light, at least one wavelength with an absorbance ratio showing a value of 5 or more is a polarizing film between 700 and 1500 nm. This absorbance ratio is usually called a dichroic ratio. If the dichroic ratio is 5 or more, it shows normal absorption anisotropy, that is, it has a polarizing function. The dichromatic ratio is preferably high, more preferably 10 or more, and particularly preferably 20 or more. When the dichroic ratio is less than 5, absorption anisotropy is definitely shown, but the absorption anisotropy, that is, the use as a polarizing function is significantly reduced. In addition, it is preferable that the wavelength at which the dichromatic ratio shows the highest value is 700 to 1500 nm, but it is not necessarily limited to this. By using the equation (1) The compound has an absorption anisotropy with a dichroic ratio of 5 or more at 700 to 1500nm, that is, it has a polarizing function, which is the characteristic of this case, and can be obtained with a higher dichroic ratio of 10 or more at 700 to 1500nm. The polarizing film has unprecedented features. Specifically, it means that when the monomer transmittance is set to 30%, the polarization degree of dichroic ratio 5 is 88.2%, that is, it shows a polarization degree of nearly 90%, while the polarization degree of dichroic ratio 10 is 98.3 %, that is, it shows about 99% polarization degree.

The dye-based polarizing film of the present invention includes a dichroic dye containing at least an azo compound represented by formula (1) or a salt thereof, and a polarizing film base material. The dye-based polarizing film of the present invention not only functions as a near-infrared polarizing film, but can also function as a color polarizing film that functions in the visible area. In particular, it can be produced as a polarizing film with a neutral gray phase in the visible area. Here, "neutral gray" refers to one that has less light leakage (color leakage) at specific wavelengths in the visible region and near-infrared region when two polarizing films are overlapped so that their alignment directions are orthogonal to each other. Specifically, in a state where two polarizing films are stacked so that their alignment directions are orthogonal to each other so that the hue becomes neutral gray, among the absorption wavelengths of 460 nm, 550 nm, and 610 nm, each wavelength is preferably independently At the same time, it has a transmittance of 3% or less, preferably 1% or less, more preferably 0.3% or less, particularly preferably 0.1% or less, particularly preferably 0.05% or less. At this time, the wavelength of the near-infrared region is, for example, 850nm or 950nm. Among them, the transmittance is 3% or less, preferably 1% or less, more preferably 0.3% or less, particularly preferably 0.1% or less, and particularly preferably 0.05% or less. Controlling the transmittance of each absorption wavelength of 460nm, 550nm, and 610nm is a wavelength that has a strong impact on transparency. Since blue, green, and red are wavelengths with strong sensitivity, the transmittance of each wavelength must be controlled at Neutral gray, and preferably one that can also control the transmittance in the infrared region to almost the same level of transmittance.

The dye-based polarizing film of the present invention contains, as a dichroic pigment, an azo compound represented by formula (1) or a salt thereof, singly or in plural, and may further contain one or more azo compounds or salts thereof as needed. of other organic dyes. There are no special restrictions on other organic dyes used together, as long as they are consistent with formula (1). A dye having dichroism in a wavelength range in which the absorption wavelength range of the azo compound or its salt is different is preferably one with high dichroism. Examples of organic dyes used in combination include: C.I. Direct Yellow 12, C.I. Direct Yellow 28, C.I. Direct Yellow 44, C.I. Direct Orange 26, C.I. Direct Orange 39, C.I. Direct Orange 71, C.I. Direct Orange 107, C.I. Direct Red 2, C.I. Direct Red 31, C.I. Direct Red 79, C.I. Direct Red 81, C.I. Direct Red 247, C.I. Direct Blue 69, C.I. Direct Blue 78, C.I. Direct Blue 247, C.I. Direct Green 80, and C.I. Direct Green 59, etc. as dyes Representative example. These pigments are contained in the dye-based polarizing film as free acids, or alkali metal salts (such as Na salt, K salt, Li salt), ammonium salts, or amine salts.

When the azo compound represented by formula (1) or its salt is used in combination with other organic dyes, the hue system of the visible area of the intended dye-based polarizing film depends on neutral gray polarizing films and color polarizing films for liquid crystal projectors. , other color polarizing films, so that the types of other organic dyes they want to prepare are different. The proportion of other organic dyes is not particularly limited, but based on the mass of the azo compound of formula (1) or its salt, the total amount of one or more organic dyes is preferably in the range of 0.1 to 10 parts by mass. .

In the case of a neutral gray polarizing film with a polarizing function in the near-infrared region, in order to reduce the color leakage of the obtained polarizing film in the visible region, other organic dyes used simultaneously with the pigment of formula (1) can be adjusted. Types and proportions.

The near-infrared dye-based polarizing film of the present invention or the dye-based polarizing film having a neutral gray polarizing function in the near-infrared region can be produced by the following method: containing at least an azo compound represented by formula (1) or its Salts and dichroic pigments that may include other organic dyes as needed are contained and aligned on the polarizing film substrate (such as a polymer film) by conventional methods, and are mixed with the liquid crystal or applied by coating. It is aligned with the polarizing film substrate.

The polarizing film base material is a polymer film, preferably a film obtained by forming a hydrophilic polymer film, and more preferably a film composed of polyvinyl alcohol resin or its derivatives. As a pro-industrial material that can be used as a polarizing film substrate Water-based polymers are not particularly limited, but refer to membranes with high affinity for water. It means, for example, a film containing water or swelling when immersed or contacted with water as a medium. Specifically, polyvinyl alcohol-based resins, amylose-based resins, starch-based resins, cellulose-based resins, polyacrylate-based resins, and derivatives thereof can be used. A dichroic dye having absorption in the infrared region is contained in a film made of these resins, and is aligned by stretching to obtain a polarizing plate. In consideration of the inclusion of a dichroic dye and cross-linking, etc., a film made of a polyvinyl alcohol-based resin is most suitable. Examples include polyvinyl alcohol or its derivatives, and those modified by olefins such as ethylene and propylene, and unsaturated carboxylic acids such as crotonic acid, acrylic acid, methacrylic acid, and maleic acid. . From the viewpoint of dye adsorption and orientation, it is appropriate to use a film composed of polyvinyl alcohol or its derivatives as a polarizing film base material. The thickness of the polarizing film base material is usually 10 to 100 μm, preferably about 25 to 80 μm.

When the base material of the polarizing film is a polymer film, and when it contains a dichroic dye containing at least the azo compound of formula (1) or a salt thereof, a method of dyeing the polymer film can usually be used. Dyeing can be performed, for example, as follows. First, the azo compound of the present invention or its salt, and if necessary other organic dyes are dissolved in water to prepare a dye bath. The dye concentration in the dye bath is not particularly limited, but is usually selected from a range of about 0.001 to 10% by mass. In addition, dyeing auxiliaries may be used as necessary. For example, it is suitable to use Glauber's salt at a concentration of about 0.1 to 10% by mass. In the dye bath prepared in this way, the polymer film is immersed for, for example, 1 to 10 minutes to perform dyeing. The preferred dyeing temperature is around 40 to 80°C.

Alignment of the dichroic dye containing the azo compound of formula (1) or its salt can be performed by extending the dyed polymer film. As the stretching method, any conventional method such as a wet method or a dry method can be used. The extension of the polymer membrane can be carried out before dyeing depending on the situation. In this case, the dye is aligned at the time of dyeing. The polymer film containing dyes and aligned can be subjected to post-treatment such as boric acid treatment by conventional methods if necessary. This post-processing is to improve the light transmission of the dye-based polarizing film. This is done for the purpose of rate and polarization. The conditions for boric acid treatment vary depending on the type of polymer membrane used and the type of dye used, but generally speaking, the boric acid concentration of the boric acid aqueous solution is set to 0.1 to 10% by mass, preferably 0.5 to 7% by mass. The range, particularly preferably, is 1 to 5% by mass, and the treatment is, for example, in a temperature range of 30 to 80°C, preferably 40 to 75°C, such as immersing and extending for 0.5 to 10 minutes. Moreover, if necessary, an aqueous solution containing a cationic polymer compound can also be used for repair treatment. In addition, the polarizing film base material using the pigment of the present invention can be obtained by stretching at pH 4 to 9 in the aqueous solution during the immersion in the stretching step, or in the step before stretching, or/in the step after further stretching. The polarizing film of the invention is preferably processed at a pH of 6 to 9 in the stretching step or the step after stretching. This is because a polarizing film in the near-infrared region with a wider bandwidth and longer wavelength can be obtained. The pH of the aqueous solution during treatment is particularly a method of adjusting the pH of the boric acid aqueous solution to 6 to 9. Preferably, the treatment is performed by adding alkaline substances such as sodium hydroxide, potassium hydroxide, and borax. Polymer membranes, especially those made of polyvinyl alcohol or its derivatives, are one of the better forms to use borax for stretching. In the case of using borax, boric acid and borax can be used together. As long as the pH of the treatment step is 6 to 9, the wavelength range of the polarizing function of the polarizing film using the pigment of the present invention can be broadened, but the more preferred range is 6.5 to 8.5, and the particularly preferred range is 6.5 to 8.0. Better form.

The dye-based polarizing film obtained by attaching a protective film can be used as a polarizing plate, and a protective layer, AR (anti-reflection) layer, support, etc. can be provided as needed. Examples of uses for dye-based polarizing films include: liquid crystal projectors, electronic calculators, clocks, notebook computers, word processors, LCD televisions, car navigation systems, indoor and outdoor measuring instruments or displays, and lenses or glasses. Authenticity determination devices, image sensor applications such as CCD or CMOS, etc. The dye-based polarizing film has high polarizing performance comparable to conventional polarizing films using iodine even in the near-infrared region, and is also excellent in durability. Therefore, it is particularly suitable for those who need It is used for various liquid crystal displays, liquid crystal projectors, vehicles, and outdoor displays that require high polarization performance and durability (such as display applications for industrial instruments and portable applications), and security devices that require high reliability.

<Dye-based polarizing plate>

The dye-based polarizing plate can be obtained by laminating a transparent protective film on at least one side of the dye-based polarizing film. Since the dye-based polarizing plate includes the above-mentioned dye-based polarizing film, it has excellent polarizing performance and moisture resistance/heat resistance/light resistance. As a material for forming a transparent protective film, a material excellent in optical transparency and mechanical strength is preferred. In addition to cellulose acetate-based films and acrylic-based films, for example, tetrafluoroethylene/hexafluoropropylene-based copolymers, etc. can be used. Fluorine-based membranes are membranes composed of polyester resin, polyolefin resin, or polyamide resin. The transparent protective film is preferably a triacetylcellulose (TAC) film or a cyclic olefin film. The thickness of the protective film is usually 10 to 200 μm, preferably 20 to 100 μm.

Examples of adhesives that can be used to bond the polarizing film and the protective film together include polyvinyl alcohol-based adhesives, urethane emulsion-based adhesives, acrylic-based adhesives, and adhesives made of polyols and isocyanates. etc., preferably polyvinyl alcohol-based adhesives.

A transparent protective layer can be further provided on the surface of the dye-based polarizing plate. Furthermore, examples of the transparent protective layer include an acrylic or polysiloxane hard coat layer, a urethane protective layer, and the like. In addition, since the light transmittance of the single board can be further improved, it is preferable to provide an AR layer on the protective layer. The AR layer can be formed by, for example, evaporating or sputtering a material such as silicon dioxide or titanium oxide, and can be formed by coating a thin fluorine-based material. The dye-based polarizing plate can also be used as a circular polarizing plate or an elliptical polarizing plate by attaching a retardation plate to the surface.

The dye-based polarizing plate can be either the above-mentioned near-infrared polarizing plate or a neutral polarizing plate with polarizing function in the near-infrared region depending on the application. The neutral gray polarizing plate of the present invention has the following characteristics: less orthogonal color leakage in the visible region and near-infrared region, excellent polarizing performance, and even high-temperature It can also prevent discoloration and degradation of polarization performance under high temperature and high humidity conditions, and has less light leakage in the orthogonal position in the viewing area; it is especially suitable for vehicles or outdoor displays, and security devices that require high reliability.

Near-infrared polarizing plates for vehicles or outdoor displays, or neutral gray polarizing plates with polarizing function in the near-infrared region. In polarizing plates composed of polarizing films and protective films, in order to further improve the light transmittance of the single plate, Preferably, an AR layer is provided as a polarizing plate with an AR layer. More preferably, an AR layer with a support such as a transparent resin and a polarizing plate with a support are further provided. The AR layer can be disposed on one or both sides of the polarizing plate. The support is preferably provided on one side of the polarizing plate, and can be provided on the polarizing plate through the AR layer or directly. The support body preferably has a flat surface for attaching the polarizing plate, and is preferably a transparent substrate used for optical purposes. Transparent substrates are roughly divided into inorganic substrates and organic substrates. Examples include inorganic substrates such as soda glass, borosilicate glass, crystal substrates, sapphire substrates, and spinel substrates, as well as acrylic, polycarbonate, and polyterephthalate. Organic substrates such as ethylene naphthalate, polyethylene naphthalate, and cyclic olefin polymers are preferably organic substrates. The thickness and size of the transparent substrate can be desired.

Near-infrared polarizing plates have excellent polarizing performance and do not cause discoloration or degradation of polarizing performance even under high temperature and high humidity conditions. Therefore, they are suitable for use in LCD projectors, vehicles, outdoor displays, and maintenance that require high reliability. For installation. The polarizing film used in these polarizing plates can also be manufactured by the method described in the manufacturing method of the dye-based polarizing film of the present invention. Moreover, a protective film is attached to the polarizing plate and a protection is provided as needed. layer or AR layer and support, etc.

Infrared polarizers near the support for vehicles or outdoor displays, or neutral polarizers and color polarizers with polarizing functions in the near-infrared region can be used, for example, by coating a transparent adhesive (adhesive) on the flat surface of the support agent, and then attach a dye-based polarizing plate to the coated surface to manufacture. In addition, a transparent adhesive (adhesive) agent can also be coated on the dye-based polarizing plate, and then the support can be attached to the coated surface. The adhesive (adhesive) agent used here is preferably an acrylic agent, for example. Furthermore, this dye-based polarizing plate was used as an elliptically polarizing plate. When using the plate, the phase difference plate side is usually attached to the support side, but the polarizing plate side can also be attached to the transparent substrate.

[Example]

The present invention will be described in more detail below based on examples, which are illustrative rather than limiting. The % and parts in the examples are based on quality unless otherwise specified.

[Example 1]

(step 1)

21.8 parts of 2-amino-5-nithenylsulfonic acid was added to 500 parts of water and dissolved with 25% sodium hydroxide, and then 35% hydrochloric acid was added to adjust the pH to 0.2. To the obtained liquid, add 17.3 parts of 40% sodium nitrite aqueous solution to prepare a diazo liquid. On the other hand, 22.3 parts of 8-aminonaphthalene-2-sulfonic acid was added to 200 parts of water, and dissolved in 25% sodium hydroxide aqueous solution to make it weakly alkaline. In this liquid, the diazo liquid obtained previously was added dropwise to maintain the pH at 4.5 to 6.0, and stirred to complete the coupling reaction. Thereafter, the mixture was salted out with sodium chloride and filtered to obtain 241 parts of wet cake of the monoazo compound represented by formula (101).

(step 2)

241 parts of the obtained wet cake of the monoazo compound (101) were added to 300 parts of water and stirred to suspend. The pH of the aforementioned suspension was adjusted to 9.0 using 25% sodium hydroxide, and 34.5 parts of a 40% sodium nitrite aqueous solution was added thereto. The obtained suspension was dropped into a mixture of 200 parts of water and 50 parts of 35% hydrochloric acid to prepare a diazo liquid. On the other hand, add 22.3 parts of 8-aminonaphthalene-2-sulfonic acid to 200 parts of water, and dissolve it with 25% sodium hydroxide. The solution dissolves and becomes weakly alkaline. In this liquid, the diazo liquid obtained previously was added dropwise to maintain the pH at 4.5 to 6.0, and stirred to complete the coupling reaction. Thereafter, the mixture was salted out with sodium chloride and filtered to obtain 342 parts of wet cake of the disazo compound represented by formula (102).

(step 3)

34.2 parts of the obtained wet cake of the disazo compound (102) was added to 200 parts of water and stirred to suspend. Use 25% sodium hydroxide to adjust the pH of the suspension to 9.0, and add 6.9 parts of 40% sodium nitrite aqueous solution. The obtained suspension was dropped into a mixture of 100 parts of water and 20 parts of 35% hydrochloric acid to prepare a diazo liquid. On the other hand, 10.0 parts of 1,5-dihydroxynaphthalene-2,6-disulfonic acid was added to 200 parts of water, and dissolved in 25% sodium hydroxide aqueous solution to make it weakly alkaline. In this liquid, the diazo liquid obtained previously was added dropwise to maintain the pH at 6.5 to 8.0, and stirred to complete the coupling reaction. Thereafter, after salting out with sodium chloride, 14.0 parts of an azo compound represented by formula (10) was obtained by filtering and drying.

<Production of polarizing films and polarizing plates>

A polyvinyl alcohol film (VF-PS #7500 manufactured by Kuraray Co., Ltd.) with a saponification degree of 99% or more and an average polymerization degree of 2400 was immersed in warm water at 45° C. for 3 minutes, and swelling treatment was performed to increase the elongation ratio to 1.30 times. In a 45°C dyeing solution containing 1500 parts by mass of water, 1.5 parts by mass of anhydrous sodium sulfate, and 0.30 parts by mass of an azo compound (10), The swollen membrane was immersed for 10 minutes and the azo compound was contained in the membrane. The obtained membrane was immersed in a 40°C aqueous solution containing 20 g/l of boric acid (manufactured by Societa Chimica Larderello S.P.A.) for 1 minute. While extending the immersed membrane 5.0 times, the stretching treatment was performed for 5 minutes in a 50° C. aqueous solution containing 15.0 g/l boric acid and 15.0 g/l borax. The obtained film was kept in a tensioned state and washed by immersing it in water at 25° C. for 20 seconds. The washed film was dried at 70° C. for 9 minutes to obtain a polarizing film. For this polarizing film, polyvinyl alcohol (NH-26 manufactured by Japan Vam & Poval Co., Ltd.) dissolved in water at 4% was used as an adhesive, and an alkali-treated cellulose triacetate film (TD manufactured by Fuji Film Co., Ltd. -80) is laminated to obtain a polarizing plate. The obtained polarizing plate maintains the optical properties of the above-mentioned polarizing film, especially transmittance, polarization degree, etc. This polarizing plate was used as a measurement sample in Example 1.

[Example 2]

68.4 parts of the wet cake of the disazo compound (102) obtained in Example 1 was added to 400 parts of water and stirred to suspend. The pH of the aforementioned suspension was adjusted to 9.0 using 25% sodium hydroxide, and 13.8 parts of 40% sodium nitrite aqueous solution was added thereto. The obtained suspension was dropped into a mixture of 100 parts of water and 40 parts of 35% hydrochloric acid to prepare a diazo liquid. On the other hand, 4.5 parts of 8-aminonaphthalene-2-sulfonic acid was added to 150 parts of water, and dissolved in 25% sodium hydroxide aqueous solution to make it weakly alkaline. In this liquid, the diazo liquid obtained previously was added dropwise to maintain the pH at 4.5 to 6.0, and stirred to complete the coupling reaction. Thereafter, the mixture was salted out with sodium chloride and filtered to obtain 100 parts of wet cake of the trisazo compound represented by formula (103).

Add 50 parts of the wet cake of the obtained trisazo compound (103) to 200 parts of water, and stir to suspend. Use 25% sodium hydroxide to adjust the pH of the suspension to 9.0, and add 6.9 parts of 40% sodium nitrite aqueous solution. The obtained suspension was dropped into a mixture of 100 parts of water and 25 parts of 35% hydrochloric acid to prepare a diazo liquid. On the other hand, 10.0 parts of 1,5-dihydroxynaphthalene-2,6-disulfonic acid was added to 100 parts of water, and dissolved in 25% sodium hydroxide aqueous solution to make it weakly alkaline. In this liquid, the diazo liquid obtained previously was added dropwise to maintain the pH at 6.5 to 8.0, and stirred to complete the coupling reaction. Thereafter, after salting out with sodium chloride, 5.0 parts of an azo compound represented by formula (14) was obtained by filtering and drying.

<Production of polarizing films and polarizing plates>

The above-mentioned compound (14) was used instead of the compound (10) used in the production of the polarizing film in Example 1, and in the extension treatment, an extension treatment was performed for 5 minutes in an aqueous solution containing 30.0 g/l boric acid at 50°C, and A polarizing plate was produced in the same manner as in Example 1, except that an aqueous solution of pH 7.5 containing sodium hydroxide was applied for 30 seconds in the water washing process after stretching, and was used as a measurement sample in Example 2.

[Example 3]

50 parts of the wet cake of the trisazo compound (103) obtained in Example 2 was added to 200 parts of water, and stirred to suspend. Use 25% sodium hydroxide to adjust the pH of the suspension to 9.0, and add 6.9 parts of 40% sodium nitrite aqueous solution. The obtained suspension was dropped into a mixture of 100 parts of water and 25 parts of 35% hydrochloric acid to prepare a diazo liquid. On the other hand, 4.5 parts of 8-aminonaphthalene-2-sulfonic acid was added to 100 parts of water, and dissolved in 25% sodium hydroxide aqueous solution to make it weakly alkaline. In this liquid, the diazo liquid obtained previously was added dropwise to maintain the pH at 4.5 to 6.0 and stir to complete the coupling reaction. Thereafter, after salting out with sodium chloride, filtration was performed to obtain 80 parts of wet cake of the tetrasazo compound represented by formula (104).

80 parts of the wet cake of the obtained tetrasazo compound (104) was added to 300 parts of water and stirred to suspend. The pH was maintained at 4.0 to 4.5 using 35% hydrochloric acid and stirred at 70 to 75°C for 3 days. Thereafter, after salting out with sodium chloride, 5.0 parts of an azo compound represented by formula (16) was obtained by filtering and drying.

<Production of polarizing films and polarizing plates>

Except that the compound (16) described above was used instead of the compound (10) used in the production of the polarizing film in Example 1, a polarizing plate was produced in the same manner as in Example 1 and used as a measurement sample in Example 3.

[Example 4]

(step 1)

Add 18.1 parts of 5-aminoisophthalic acid and 75 parts of 35% hydrochloric acid to 100 parts of water and suspend them. To the obtained liquid, 18.1 parts of 40% sodium nitrite aqueous solution was added to prepare a diazo liquid. On the other hand, 24.7 parts of 8-amino-4-hydroxynaphthalene-2-sulfonic acid was added to 200 parts of water, and dissolved in 25% sodium hydroxide aqueous solution to make it weakly alkaline. In this liquid, the diazo liquid obtained previously was added dropwise to maintain the pH at 4.5 to 6.0, and stirred to complete the coupling reaction. Thereafter, after salting out with sodium chloride, filtration was performed to obtain 150 parts of wet cake of the monoazo compound represented by formula (105).

(step 2)

150 parts of the obtained wet cake of the monoazo compound (105) was added to 300 parts of water, and stirred to suspend. The pH of the aforementioned suspension was adjusted to 9.0 using 25% sodium hydroxide, and 18.1 parts of 40% sodium nitrite aqueous solution was added thereto. The obtained liquid was added dropwise to a mixture of 100 parts of water and 60 parts of 35% hydrochloric acid to prepare a diazo liquid. On the other hand, 22.3 parts of 8-aminonaphthalene-2-sulfonic acid and 300 parts of N-methyl-2-pyrrolidone were added to 300 parts of water, and dissolved in a 25% sodium hydroxide aqueous solution to become weakly alkaline. In this liquid, the diazo liquid obtained previously was added dropwise to maintain the pH at 4.5 to 6.0, and stirred to complete the coupling reaction. Thereafter, the mixture was salted out with sodium chloride and filtered to obtain 130 parts of wet cake of the disazo compound represented by formula (106).

(step 3)

130 parts of the obtained wet cake of the disazo compound (106) was added to 300 parts of water, and stirred to suspend. The pH of the aforementioned suspension was adjusted to 9.0 using 25% sodium hydroxide, and 17.3 parts of a 40% sodium nitrite aqueous solution was added thereto. The obtained suspension was dropped into a mixture of 100 parts of water and 30 parts of 35% hydrochloric acid to prepare a diazo liquid. On the other hand, 24.7 parts of 8-amino-4-hydroxynaphthalene-2-sulfonic acid and 300 parts of N-methyl-2-pyrrolidinone were added to 300 parts of water, and dissolved in 25% sodium hydroxide aqueous solution to form Weakly alkaline. In this liquid, the diazo liquid obtained previously was added dropwise to maintain the pH at 4.5 to 6.0, and stirred to complete the coupling reaction. Use 25% sodium hydroxide to make the obtained The pH of the reaction liquid became 9.0, and after salting out with sodium chloride, it was filtered to obtain 50 parts of wet cake of the trisazo compound represented by formula (107).

(Step 4)

80 parts of the wet cake of the obtained trisazo compound (107) was added to 300 parts of water and stirred to suspend. The pH was maintained at 4.0 to 4.5 using 35% hydrochloric acid and stirred at 50 to 60°C for 5 days. Thereafter, after salting out with sodium chloride, 3.0 parts of an azo compound represented by formula (108) was obtained by filtering and drying.

<Production of polarizing films and polarizing plates>

The above-mentioned compound (108) was used instead of the compound (10) used in the production of the polarizing film in Example 1, and in the stretching treatment, in addition to applying a stretching treatment for 5 minutes in a 50° C. aqueous solution containing 30.0 g/l boric acid , operate similarly to Example 1 to prepare a polarizing plate, and use it as a measurement sample in Example 4.

[Example 5]

Except using 22.3 parts of 8-aminonaphthalene-2-sulfonic acid instead of 24.7 parts of 8-amino-4-hydroxynaphthalene-2-sulfonic acid in step 1 of Example 4, operate in the same manner as Example 4 to obtain the formula ( 4.0 parts of the azo compound shown in 109).

<Production of polarizing films and polarizing plates>

Except that the compound (109) was used instead of the compound (10) used in the production of the polarizing film in Example 1, a polarizing plate was produced in the same manner as in Example 1 and used as a measurement sample in Example 5.

[Example 6]

Except that 18.1 parts of 5-aminoisophthalic acid is used to replace 21.8 parts of 2-amino-5-nitrobenzene sulfonic acid in step 1 of Example 1, the same operation is performed as in Example 1 to obtain the coupling compound represented by formula (110). 9.0 parts of nitrogen compounds.

<Production of polarizing films and polarizing plates>

Except that the compound (110) was used instead of the compound (10) used in the production of the polarizing film in Example 1, a polarizing plate was produced in the same manner as in Example 1 and used as a measurement sample in Example 6.

[Example 7]

In addition to using 18.1 parts of 5-aminoisophthalic acid to replace 21.8 parts of 2-amino-5-nitrobenzenesulfonic acid in step 1 of Example 1, and using 10.0 parts of 1,5-dihydroxynaphthalene-2-sulfonic acid. Except for 10.0 parts of 1,5-dihydroxynaphthalene-2,6-disulfonic acid in step 3, proceed in the same manner as in Example 1 to obtain 4.0 parts of an azo compound represented by formula (111).

<Production of polarizing films and polarizing plates>

Except that the compound (111) was used instead of the compound (10) used in the production of the polarizing film in Example 1, a polarizing plate was produced in the same manner as in Example 1 and used as a measurement sample in Example 7.

[Example 8]

In step 3 of Example 4, except that 22.3 parts of 8-aminonaphthalene-2-sulfonic acid was used instead of 24.7 parts of 8-amino-4-hydroxynaphthalene-2-sulfonic acid, the same operation was performed as in Example 4 to obtain 4.0 parts of the azo compound represented by formula (112).

<Production of polarizing films and polarizing plates>

Except that the compound (112) was used instead of the compound (10) used in the production of the polarizing film in Example 1, a polarizing plate was produced in the same manner as in Example 1 and used as a measurement sample in Example 8.

[Example 9]

(step 1)

Suspended 23.0 parts of 2-aminobenzothiazole-6-sulfonic acid in 130 parts of 50% sulfuric acid, and dripped 34.0 parts of 40% nitrososulfuric acid at 5 to 10°C for about 20 minutes while stirring, to obtain Diazo reaction solution. On the other hand, 22.3 parts of 8-aminonaphthalene-2-sulfonic acid was added to 200 parts of water, and dissolved in 25% sodium hydroxide aqueous solution to make it weakly alkaline. In this liquid, the diazo liquid obtained previously was added dropwise to maintain the pH at 4.5 to 6.0, and stirred to complete the coupling reaction. Thereafter, the mixture was salted out with sodium chloride and filtered to obtain 241 parts of wet cake of the monoazo compound represented by formula (113).

(step 2)

241 parts of the obtained wet cake of the monoazo compound (113) were added to 300 parts of water, and stirred to suspend. The pH of the aforementioned suspension was adjusted to 9.0 using 25% sodium hydroxide, and 34.5 parts of a 40% sodium nitrite aqueous solution was added thereto. The obtained suspension was dropped into a mixture of 200 parts of water and 50 parts of 35% hydrochloric acid to prepare a diazo liquid. On the other hand, 22.3 parts of 8-aminonaphthalene-2-sulfonic acid was added to 200 parts of water, and dissolved in 25% sodium hydroxide aqueous solution to make it weakly alkaline. In this liquid, the diazo liquid obtained previously was added dropwise to maintain the pH at 4.5 to 6.0, and stirred to complete the coupling reaction. Thereafter, after salting out with sodium chloride, the mixture was filtered to obtain 342 parts of wet cake of the disazo compound represented by formula (114).

(step 3)

34.2 parts of the obtained wet cake of the disazo compound (114) was added to 200 parts of water, and stirred to suspend. Use 25% sodium hydroxide to adjust the pH of the suspension to 9.0, and add 6.9 parts of 40% sodium nitrite aqueous solution. The obtained suspension was dropped into a mixture of 100 parts of water and 20 parts of 35% hydrochloric acid to prepare a diazo liquid. On the other hand, 10.0 parts of 1,5-dihydroxynaphthalene-2,6-disulfonic acid was added to 200 parts of water, and dissolved in 25% sodium hydroxide aqueous solution to make it weakly alkaline. In this liquid, the diazo liquid obtained previously was added dropwise to maintain the pH at 6.5 to 8.0, and stirred to complete the coupling reaction. Thereafter, after salting out with sodium chloride, 14.0 parts of an azo compound represented by formula (30) was obtained by filtering and drying.

<Production of polarizing films and polarizing plates>

Except that the compound (30) was used instead of the compound (10) used in the production of the polarizing film in Example 1, a polarizing plate was produced in the same manner as in Example 1 and used as a measurement sample in Example 9.

[Comparative example 1]

Add 14 parts of 4-((4-aminophenyl)diazenyl)benzenesulfonic acid to 200 parts of water and stir to suspend. Use 25% sodium hydroxide to adjust the pH of the suspension to 9.0, and add 9.1 parts of 40% sodium nitrite aqueous solution. The obtained suspension was dropped into a mixture of 100 parts of water and 20 parts of 35% hydrochloric acid to prepare a diazo liquid. On the other hand, 16.0 parts of 1,5-dihydroxynaphthalene was added to 200 parts of water, and dissolved in a 25% sodium hydroxide aqueous solution to make it slightly alkaline. In this liquid, the diazo liquid obtained previously was added dropwise to maintain the pH at 6.5 to 8.0, and stirred to complete the coupling reaction. Thereafter, after salting out with sodium chloride, 10.0 parts of an azo compound represented by formula (115) was obtained by filtering and drying.

<Production of polarizing films and polarizing plates>

Except that the compound (115) was used instead of the compound (10) used in the production of the polarizing film in Example 1, a polarizing plate was produced in the same manner as in Example 1 and used as a measurement sample in Comparative Example 1.

[Comparative example 2]

In step 1 of Example 1, in addition to replacing 21.8 parts of 2-amino-5-nithenylsulfonic acid with 47.3 parts of 8-amino-8-toluenesulfonyloxynaphthalene-3,6-disulfonic acid Except for this, the same operation as step 1 and step 2 of Example 1 was performed to obtain 300 parts of wet cake of the azo compound represented by formula (116).

Add 300 parts of the wet cake of the obtained disazo compound (116) to 800 parts of water and stir to suspend. Use 25% sodium hydroxide aqueous solution to maintain the pH at 10.5 to 11.0 and stir at 70 to 90°C. 2 hours. Thereafter, after salting out with sodium chloride, 30.0 parts of an azo compound represented by formula (117) was obtained by filtering and drying.

<Production of polarizing films and polarizing plates>

Except that the compound (117) was used instead of the compound (10) used in the production of the polarizing film in Example 1, a polarizing plate was produced in the same manner as in Example 1 and used as a measurement sample in Comparative Example 2.

[Comparative example 3]

<Production of polarizing films and polarizing plates>

It was produced in the same manner as in Example 1 except that the following compound (118) described in Example 2 of Japanese Patent Application Laid-Open No. 2003-64276 was used instead of the compound (10) used in the production of the polarizing film in Example 1. A polarizing plate was used as a measurement sample in Comparative Example 3.

[Comparative example 4]

<Production of polarizing films and polarizing plates>

It was produced in the same manner as in Example 1, except that the following compound (119) described in Example 2 of Japanese Patent Publication No. 60-168743 was used instead of the compound (10) used in the production of the polarizing film in Example 1. A polarizing plate was used as a measurement sample in Comparative Example 4.

[Comparative example 5]

<Production of polarizing films and polarizing plates>

The same operation as Example 1 was performed except that the following compound (120) described in Compound Example No. 1 of Japanese Patent Application Laid-Open No. 2001-56412 was used instead of the compound (10) used in the preparation of the polarizing film in Example 1. A polarizing plate was produced and used as a measurement sample of Comparative Example 5.

[Comparative example 6]

<Production of polarizing films and polarizing plates>

A polarizing plate was produced in the same manner as in Example 1, except that the following compound (121) described in Japanese Patent Application Laid-Open No. 11-269136 was used instead of the compound (10) used in the preparation of the polarizing film in Example 1. Measurement sample of Comparative Example 6. However, the following compound (121) is not soluble in water and is not contained in the polyvinyl alcohol film, that is, it does not function as a polarizing film.

(Measurement of the maximum absorption wavelength of polarizing plates, their transmittance and polarization degree)

For the polarizing plates obtained in Examples 1 to 9 and Comparative Examples 1 to 6, the maximum absorption wavelength, the single transmittance (%) of the wavelength, and its polarization degree (%) were measured. In the measurement of the maximum absorption wavelength (nm, λmax) of the polarizing plate and the calculation of the polarization degree, the parallel transmittance (Ky, %) and the orthogonal transmittance (Kz, %) when the polarized light is incident are measured using a spectrophotometer (Hitachi U-4100 manufactured by Seisakusho) was measured. Here, parallel transmittance (Ky) means: the transmittance when the absorption axis of the absolute polarizer used in the measurement is parallel to the absorption axis of the polarizer; orthogonal transmittance (Kz) means: the absolute polarization used in the measurement The transmittance when the absorption axis of the sheet is orthogonal to the absorption axis of the polarizing plate. The parallel transmittance and orthogonal transmittance of each wavelength are measured at 5nm intervals from 380 to 1200nm. Using the measured values, calculate the monomer transmittance at each wavelength using the following formula (i), and calculate the polarization degree at each wavelength using the following formula (ii) to obtain the highest value between 380 and 1200 nm. The polarization degree, its maximum absorption wavelength ( λ max), and the monomer transmittance. In addition, Ky and Kz are converted into absorbance (A _L =log(1/(Ky/100)), A _H =log(1/(Kz/100)), and the dichroic ratio Rd(=A _H /A _L =log(Kz/100)/log(Ky/100)). In addition, it was confirmed that the wavelength range in which the dichroic ratio shows a value of 5 or more, and the wavelength range in which the dichroic ratio shows a value of 10 or more .The results are shown in Table 1. In addition, since the measurement sample of Comparative Example 6 did not show polarizing function, it is not described in Table 1.

Transmittance (%)=(Ky+Kz)/2 (i)

Polarization degree (%)=[(Ky-Kz)/(Ky+Kz)]×100 (ii)

[Table 1]

As shown in Table 1, the polarizing plates obtained in Examples 1 to 9 have high polarizing properties at the maximum absorption wavelength ( λ max), and all of them have a dichroic ratio (Rd) of 5 or more in the near-infrared region. Absorption anisotropy, that is, it has polarizing function. In addition, even above 900nm, it also exhibits a dichroic ratio of more than 10, that is, it has high polarization in a wide frequency band.

On the other hand, in Comparative Examples 1 to 5, the frequency bands in which the dichromatic ratio is 5 or more are all limited to a wavelength range of less than 700 nm. It was found that the compounds of Comparative Examples 1 to 3 and 5, as described in Japanese Patent Application Laid-Open No. 11-269136, had at least one -OH group at the p-position of the diazene group and had almost no wavelength above 700 nm. With polarizing function. Especially in Comparative Example 2, since there is no wavelength range in which the dichroism ratio is 5 or more, it is found that the polarizing function is significantly low. Furthermore, it was found that the λ max of Comparative Example 1, which is similar to the dye represented by the structural formula (III) in Japanese Patent Application Laid-Open No. 11-269136, is 540 nm, and a compound similar to the dye represented by the structural formula (X) is used. The λ max of Comparative Example 2 is 590 nm, and neither of them has a maximum absorption wavelength in the near-infrared region under the polarizing plate state.

[Example of making neutral gray polarizing plate]

As the dyeing solution, a 45° C. aqueous solution with a concentration of 0.2% of compound (14) obtained in Example 2, C.I. Direct Orange 39 0.07%, C.I. Direct Red 81 0.02%, and Glauber's Salt 0.1% was used. The polarizing film was produced in the same manner as in Example 1. The obtained polarizing film has an average single-plate transmittance of 38% from 380 to 1200 nm, an average light transmittance of orthogonal position of 0.02%, and a dichroic ratio across a wide frequency band with a high polarization degree of more than 10. Moreover, both the parallel position and the orthogonal position have a neutral gray hue in the visible area. Each piece of cellulose triacetate film (TAC film; manufactured by Fuji Film Co., Ltd.; trade name: TD-80U) is laminated on both sides of the polarizing film via an adhesive of a polyvinyl alcohol aqueous solution. Next, an AR support (ReaLook X4010 manufactured by NOF Co., Ltd.) was laminated on the TAC film on one side using an adhesive to obtain a neutral gray dye-based polarizing plate with an AR support. The obtained polarizing plate has the same neutral gray hue as the polarizing film, and has a high degree of polarization from the visible region to the near-infrared region. The obtained polarizing plate shows long-term durability even in a high-temperature and high-humidity state, and is also excellent in light resistance against long-term exposure.

[Industrial availability]

Polarizing films and polarizing plates obtained by using the azo compound represented by formula (1) or its salt can have high polarization degree in the infrared region, or from the visible region to the infrared region. The obtained polarizing plate shows long-term durability even in a high-temperature and high-humidity state. Furthermore, it is also excellent in light resistance against long-term exposure, and is extremely useful. Therefore, the polarizing plate obtained by using the azo compound represented by formula (1) or its salt can be applied to sensors, lenses, switching elements, isolators, cameras, and indoor and outdoor measuring instruments that require high polarization. Or vehicle-mounted devices such as driver sensing modules. In addition, it can be better used in devices that sense infrared rays, such as infrared panels, spatial infrared touch modules, etc., and can be used together with conventional displays, such as computers. Monitors, clocks, notebook computers, word processors, LCD TVs, polarized lenses, polarized glasses, car navigation, etc. are not only visual displays, but also modules that utilize infrared light.

Claims (15)

An azo compound or a salt thereof, the azo compound is represented by the following formula (1),

In the formula (1), A ¹ represents a phenyl group which may have a substituent, or a heterocyclic group which may have a substituent, and A ² , A ³ and A ⁴ each independently represent a group having SO ₃ M and may have a hydroxyl group selected from the group consisting of C1 to 4 alkoxy groups, and naphthyl groups as substituents of substituted or unsubstituted amino groups, R ¹ represents a hydrogen atom, hydroxyl group, C1 to 4 alkoxy groups, substituted or unsubstituted amino groups, m represents 0 to an integer of 5, M represents a hydrogen atom or ion, metal ion, or ammonium ion, n represents 1 or 2, k represents 0 or 1, the hydrogen atoms of ring a and ring b can be substituted by the substituent R ¹ or the substituent SO ₃ Replaced by M. The azo compound or salt thereof according to claim 1, wherein A ¹ in the above formula (1) represents a heterocyclic group which may have a substituent. The azo compound or salt thereof according to claim 2, wherein the heterocyclic group which may have a substituent is selected from the group consisting of groups represented by the following formulas (2) to (4) ;

In formulas (2) to (4), Aliphatic hydrocarbon group, C1 to 4 aliphatic hydrocarbon group with hydroxyl group, C1 to 4 aliphatic hydrocarbon group with carboxyl group, C1 to 4 alkoxy group with sulfonic acid group, C1 to 4 alkoxy group with hydroxyl group , a C1 to 4 alkoxy group having a carboxyl group, q ¹ represents an integer from 0 to 4, q ² represents an integer from 0 to 6, M represents a hydrogen atom or an ion, a metal ion, or an ammonium ion, and n ¹ and n ² each represent Represents an integer from 0 to 3. In each formula, * indicates the bonding position with the azo bond. The azo compound or salt thereof as described in any one of items 1 to 3 of the claimed patent scope, wherein in the above formula (1), A ² , A ³ and A ⁴ are each independently represented by the following formula (5) shown;

In formula (5), R ² represents a hydrogen atom, a hydroxyl group, a C1 to 4 alkoxy group, or a substituted or unsubstituted amine group, m ² represents an integer from 0 to 6, and M represents a hydrogen atom or ion, metal ion, Or ammonium ion, n ³ represents an integer from 1 to 2. For example, the azo compound or salt thereof described in claim 1, wherein the above formula (1) is represented by the following formula (7),

In formula (7), A ⁵ is the same as A ¹ in the above formula (1), and R ³ and R ⁴ each independently represent a hydrogen atom, a hydroxyl group, a C1 to 4 alkoxy group, or a substituted or unsubstituted amine group. , m ³ and m ⁴ each represent an integer from 0 to 5, M represents a hydrogen atom or ion, a metal ion, or an ammonium ion, and n ⁴ represents 1 or 2. For example, the azo compound or salt thereof described in claim 1, wherein the above formula (1) is represented by the following formula (8),

In the formula (8), A ⁶ is the same as A ¹ in the above formula (1), and R ⁵ , R ⁶ and R ⁷ each independently represent a hydrogen atom, a hydroxyl group, an alkoxy group of C1 to 4, substituted or unsubstituted For the amine group, m ⁵ to m ⁷ each represent an integer from 0 to 5, M represents a hydrogen atom or ion, a metal ion, or an ammonium ion, and n ⁵ represents 1 or 2. For example, the azo compound or salt thereof described in claim 1, wherein the above formula (1) is represented by the following formula (9),

In formula (9), R ⁸ , R ⁹ , and R ¹⁰ each independently represent a hydrogen atom, a hydroxyl group, an alkoxy group with C1 to 4, or a substituted or unsubstituted amino group, and m ⁸ to m ¹⁰ each represent a value between 0 and 5. An integer, M represents a hydrogen atom or ion, a metal ion, or an ammonium ion, and n ⁶ represents 1 or 2. A polarizing film containing at least one of the azo compounds or salts thereof as described in any one of items 1 to 7 of the patent application. The polarizing film _described in item 8 of the patent application, wherein the absorbance _ratio Rd (= At least one of the wavelengths showing a value of A _H /A _L above 5 is between 700 and 1500 nm. The polarizing film described in Item 8 or 9 of the patent application contains an azo compound or a salt thereof as described in any one of Items 1 to 7 of the patent application, and one or more of the azo compounds or Organic dyes other than their salts. For example, the polarizing film described in item 8 or 9 of the patent application scope displays neutral gray. The polarizing film according to claim 8 or 9, wherein a film containing polyvinyl alcohol resin or a derivative thereof is used as a base material. A polarizing plate is provided with a transparent protective layer on at least one side of the polarizing film described in any one of items 8 to 12 of the patent application. A display device using the polarizing film described in any one of items 8 to 12 of the patent application or the polarizing plate described in item 13 of the patent application. The display device described in Item 14 of the patent application is for vehicle or outdoor display use.