JP7724160B2 - Azo compounds or salts thereof, and dye-based polarizing films, dye-based polarizing plates, and displays containing the same - Google Patents

Description

The present invention relates to a novel azo compound or a salt thereof, as well as a dye-based polarizing film, a dye-based polarizing plate, and a display device containing the same.

Polarizing plates, which have the ability to transmit and block light, are fundamental components of displays such as liquid crystal displays (LCDs), along with liquid crystals, which have the ability to switch light. Applications for LCDs range from early compact devices such as calculators and clocks to laptops, word processors, LCD projectors, LCD TVs, car navigation systems, and indoor and outdoor measuring instruments. Polarizing plates can also be applied to lenses, such as sunglasses with improved visibility and, more recently, polarized glasses compatible with 3D televisions. As the range of uses for polarizing plates expands, they are used in a wide range of conditions, from low to high temperatures, low to high humidity, and low to high light levels, creating a demand for polarizing plates with high polarization performance and durability.

Currently, polarizing plates are manufactured by stretching and orienting polyvinyl alcohol or its derivative films containing iodine or dichroic dyes, or by orienting polyene-based films produced by dehydrochlorinating polyvinyl chloride films or dehydrating polyvinyl alcohol films to form polyenes. The iodine or dichroic dye significantly affects the polarization characteristics and durability of polarizing plates. Iodine-based polarizing films, which use iodine, have excellent polarization performance but are susceptible to water and heat, resulting in poor durability when used for long periods under high temperature and humidity conditions. While methods to improve durability have been considered, such as treating them with aqueous solutions containing formalin or boric acid or using a polymer film with low moisture permeability as a protective layer, these methods are not particularly effective. On the other hand, dye-based polarizing films, which use dyes, have superior moisture and heat resistance compared to iodine-based polarizing films, but generally lack sufficient polarization performance.

In recent years, images have been displayed at high brightness on LCD displays to improve their clarity. Hybrid cars, mobile devices, and other devices equipped with such displays require longer battery life. This has created a demand for polarizing plates that can maintain image brightness and color clarity even when brightness is reduced to reduce power consumption.

However, when polarizing films, which are made by adsorbing and aligning several dyes onto a polymer film, leaking light (color leakage) at specific wavelengths in the visible light range can cause the hue of the LCD display to change in the dark when attached to an LCD panel. Therefore, to prevent discoloration of the LCD display due to color leakage at specific wavelengths in the dark when attached to an LCD display device, a neutral-color polarizing film made by dyeing or incorporating several dyes into the polymer film must be used to uniformly reduce the cross-polarization transmittance (cross transmittance) in the visible light range. Furthermore, in-car LCD displays require polarizers that maintain their polarization even in harsh environments, such as the high temperature and humidity experienced inside a car during the summer. Therefore, iodine-based polarizers, which offer excellent polarization performance and a neutral gray color, have been used. However, as mentioned above, iodine-based polarizers suffer from insufficient light resistance, heat resistance, and humidity and heat resistance. To address this issue, dye-based neutral gray polarizers, which are dyed or incorporate several dichroic dyes, have begun to be used. Dye-based neutral gray polarizers generally use a combination of dyes in the three primary colors of light: red, blue, and yellow. However, as mentioned above, the polarization performance of dye-based neutral gray polarizers is insufficient. Therefore, it was necessary to develop dichroic dyes with good polarization performance for each of the three primary colors.

As mentioned above, dye-based polarizers are characterized by the fact that they contain or dye each of the three primary color components of light with independent dyes that correspond to each of them in order to control them. Light sources used in modern LCD panels include cold cathode fluorescent lamps and LEDs, but the wavelength of the light emitted from these panels varies depending on the system, and even for the same system, it often varies between panel manufacturers. Therefore, when developing dichroic dyes with good polarization performance, it is particularly important to design dichroic dyes with absorption wavelengths that match the wavelength of the light source.

Dyes used in the production of dye-based polarizing films such as those described above include water-soluble azo compounds described in, for example, Patent Documents 1 to 5.

Japanese Patent Application Publication No. 03-012606 Japanese Patent Application Laid-Open No. 2001-33627 JP 2009-132794 A Japanese Patent Application Laid-Open No. 2001-240762 Japanese Patent Application Laid-Open No. 2001-108828 Japanese Patent Application Publication No. 156759/1983 Japanese Patent Application Laid-Open No. 1996-291259

"Dye Chemistry" by Yutaka Hosoda, Gihodo Publishing Co., Ltd., 1957, 621 pages

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 plate containing the same. Another object of the present invention is to provide a dichroic dye azo compound that absorbs in a specific visible light region and a polarizing film containing the same that exhibits excellent polarization performance. Furthermore, another object of the present invention is to provide a neutral gray polarizing plate containing the novel dichroic dye azo compound.

As a result of intensive research to achieve this objective, the inventors discovered a novel azo compound that absorbs light in a specific visible light region. Furthermore, they discovered that by orienting the azo compound in a film containing the azo compound, the film can function as a polarizing film or polarizing plate.

That is, the present invention relates to, but is not limited to, the following:
[Invention 1]
An azo compound represented by the following formula (1) or a salt thereof:

(In the formula, A ₁ and A ₂ each independently represent a naphthyl group which may have a substituent, or a phenyl group which may have a substituent; m, n, and p each independently represent 0 or 1, and either m or n represents 1; and R ₁ to R ₁₂ each independently represent a hydrogen atom or a substituent).
[Invention 2]
The azo compound or salt thereof according to Invention 1, wherein in the formula (1), A ₁ and A ₂ are each independently a naphthyl group optionally having at least one substituent selected from the group consisting of a C1-4 alkoxy group having a sulfo group, a hydroxy group, and a sulfo group, or a phenyl group optionally having at least one substituent selected from the group consisting of a C1-4 alkoxy group having a sulfo group, a sulfo group, and a carboxy group.
[Invention 3]
3. The azo compound or salt thereof according to Invention 1 or 2, wherein, in the formula (1), A ₁ and A ₂ each independently represent a naphthyl group optionally having a substituent selected from the group consisting of a C1-4 alkoxy group having a sulfo group, a hydroxy group, and a sulfo group.
[Invention 4]
4. The azo compound or salt thereof according to any one of Inventions ₁ to ₃ , wherein in the formula (1), R ₁ , R ₂ , R ₁₁ and R ₁₂ are each independently a hydrogen atom, a C1-4 alkyl group or a C1-4 alkoxy group, and R 3 to R 10 are each independently a hydrogen atom, a C1-4 alkoxy group having a sulfo group, a C1-4 alkoxy group or a C1-4 alkyl group.
[Invention 5]
5. The azo compound or salt thereof according to any one of Inventions 1 to 4, wherein in the formula (1), the phenyl group which may have a substituent is a phenyl group represented by the following formula (2):

(In the formula, one of R ₁₃ and R ₁₄ represents a sulfo group, a carboxy group, or a C1-4 alkoxy group having a sulfo group, and the other represents a hydrogen atom, a sulfo group, a carboxy group, a C1-4 alkoxy group having a sulfo group, a C1-4 alkyl group, a C1-4 alkoxy group, a halogen atom, a nitro group, an amino group, a C1-4 alkyl-substituted amino group, or a C1-4 alkyl-substituted acylamino group, and * in the formula represents the bonding position to the terminal amide group or azo group in formula (1)).
[Invention 6]
6. The azo compound or salt thereof according to claim 5, wherein in the formula (2), one of R ₁₃ and R ₁₄ is a sulfo group or a carboxy group, and the other is a hydrogen atom, a sulfo group, a carboxy group, a chloro group, a methyl group, or a methoxy group.
[Invention 7]
7. The azo compound or salt thereof according to any one of Inventions 1 to 6, wherein in the formula (1), the naphthyl group which may have a substituent is a naphthyl group represented by the following formula (3):

(wherein R ₁₅ represents a hydrogen atom, a C1-4 alkoxy group having a sulfo group, a hydroxy group, or a sulfo group, q represents an integer of 1 to 3, and * represents the bonding position with the terminal amide group or azo group in formula (1)).
[Invention 8]
8. The azo compound or salt thereof according to any one of Inventions 1 to 7, wherein in the formula (1), R ₃ to R ₁₀ are each independently a group selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, a methoxy group, and a 3-sulfopropoxy group.
[Invention 9]
The azo compound or salt thereof according to any one of Inventions 1 to 8, wherein the formula (1) is represented by the following formula (4):

(wherein A ₁ , A ₂ , R ₁ to R ₁₂ , m, n, and p are the same as in the above formula (1)).
[Invention 10]
10. The azo compound or a salt thereof according to any one of Inventions 1 to 9, wherein p is 0.
[Invention 11]
10. The azo compound or salt thereof according to any one of Inventions 1 to 9, wherein p is 1.
[Invention 12]
12. A dye-based polarizing film comprising the azo compound or a salt thereof according to any one of Inventions 1 to 11 and a substrate.
[Invention 13]
The dye-based polarizing film according to Invention 12 further comprises one or more organic dyes having a structure other than the azo compound or a salt thereof.
[Invention 14]
14. The dye-based polarizing film according to claim 12, wherein the substrate is a film containing a polyvinyl alcohol resin or a derivative thereof.
[Invention 15]
15. A dye-based polarizing film according to any one of Inventions 12 to 14, which exhibits neutral gray.
[Invention 16]
A dye-based polarizing plate comprising the dye-based polarizing film according to any one of Inventions 12 to 15, and a transparent protective film attached to one or both sides of the dye-based polarizing film.
[Invention 17]
A display device comprising the dye-based polarizing film according to any one of Inventions 12 to 15 or the dye-based polarizing plate according to Invention 16.

The azo compound or salt thereof of the present invention is useful as a dye for polarizing films. In one embodiment, the azo compound or salt thereof of the present invention is water-soluble. In one embodiment, the azo compound or salt thereof of the present invention is dichroic. In one embodiment, the dye-based polarizing film or dye-based polarizing plate of the present invention has high polarization performance comparable to that of polarizing films using iodine, and also has excellent durability. Therefore, it is suitable for use in various liquid crystal display devices and liquid crystal projectors, as well as in automotive applications requiring high polarization performance and durability, and for display applications in industrial instruments used in various environments.

<Azo compound or its salt>
The azo compound or a salt thereof of the present invention is represented by the above formula (1).

In formula (1), _A1 and _A2 each independently represent a naphthyl group which may have a substituent, or a phenyl group which may have a substituent; m, n, and p each independently represent 0 or 1, provided that either m or n is 1; and _R1 to _R12 each independently represent a hydrogen atom or a substituent.

Examples of the naphthyl group in the naphthyl group that may have the above substituent include a 1-naphthyl group and a 2-naphthyl group, with a 2-naphthyl group being preferred.

The substituent in the naphthyl group which may have a substituent is not particularly limited, and examples thereof include a C1-4 (1 to 4 carbon atoms) aliphatic hydrocarbon group which may have a substituent, a C1-4 alkoxy group which may have a substituent, an aryloxy group which may have a substituent, a hydroxy group, a sulfo group, a carboxy group, a substituted or unsubstituted amino group, an amido group, and the like. A C1-4 alkoxy group which may have a substituent, a hydroxy group, or a sulfo group is preferred, and a C1-4 alkoxy group which has a sulfo group, a hydroxy group, or a sulfo group is more preferred. The number and substitution positions of the substituents on the naphthyl group are not particularly limited, but for example, when A in the above formula (1) is represented by the following formula, if there are two substituents, and the site to which the azo bond or amide bond is bonded is the 2-position, a combination of the 5-position and the 7-position, a combination of the 4-position and the 8-position, or a combination of the 6-position and the 8-position is preferred, and if there are three substituents, a combination of the 3-position, the 5-position and the 7-position, or a combination of the 3-position, the 6-position and the 8-position is preferred.

Examples of the C1-4 aliphatic hydrocarbon group in the C1-4 aliphatic hydrocarbon group that may have the above-mentioned substituent include straight-chain alkyl groups such as methyl, ethyl, n-propyl, and n-butyl, branched-chain alkyl groups such as sec-butyl and tert-butyl, and unsaturated hydrocarbon groups such as vinyl.

Examples of the C1-4 alkoxy group in the C1-4 alkoxy group, which may have the above-mentioned substituent, include a methoxy group, an ethoxy group, an n-propoxy group, an n-butoxy group, a sec-butoxy group, and a tert-butoxy group.

Examples of the aryloxy group in the aryloxy group that may have the above substituents include a phenoxy group and a naphthoxy group.

Examples of the substituted or unsubstituted amino group include mono-substituted amino groups such as amino, methylamino, ethylamino, n-propylamino, n-butylamino, monophenylamino, and mononaphthylamino, and di-substituted amino groups such as dimethylamino, diethylamino, and diphenylamino. These substituted amino groups may further have a substituent.

The substituents on the optionally substituted C1-4 aliphatic hydrocarbon groups and optionally substituted C1-4 alkoxy groups are not particularly limited and include, for example, hydroxy groups, sulfo groups, carboxy groups, substituted or unsubstituted amino groups, and amido groups. The substituents on the optionally substituted aryloxy groups and substituted amino groups are not particularly limited and include, for example, optionally substituted C1-4 aliphatic hydrocarbon groups.

Preferred substituents on the phenyl group, which may have the above substituents, include a sulfo group, a carboxy group, a C1-4 alkoxy group having a sulfo group, a C1-4 alkyl group, a C1-4 alkoxy group, a halogen atom, a nitro group, an amino group, a C1-4 alkyl-substituted amino group, and a C1-4 alkyl-substituted acylamino group. When the phenyl group has two or more substituents, it is preferred that at least one of the substituents is a sulfo group, a carboxy group, or a lower alkoxy group having a sulfo group, and that the other substituents are a sulfo group, a hydrogen atom, a lower alkyl group, a lower alkoxy group, a lower alkoxy group having a sulfo group, a carboxy group, a chloro group, a bromo group, a nitro group, an amino group, a lower alkyl-substituted amino group, or a lower alkyl-substituted acylamino group. The other substituents are more preferably a sulfo group, a hydrogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, a carboxy group, a sulfoethoxy group, a sulfopropoxy group, a sulfobutoxy group, a chloro group, a nitro group, or an amino group, and particularly preferably a sulfo group, a carboxy group, a hydrogen atom, a methyl group, or a methoxy group. The substitution position is not particularly limited, but when the bonding position to the terminal amide group in formula (1) is the 1st position, preferably the 2nd position only, the 4th position only, a combination of the 2nd and 6th positions, a combination of the 2nd and 4th positions, or a combination of the 3rd and 5th positions, and particularly preferably the 2nd position only, the 4th position only, a combination of the 2nd and 4th positions, or a combination of the 3rd and 5th positions. Note that the 2nd position only and the 4th position only indicate that only the 2nd or 4th position has one substituent other than a hydrogen atom. In the specification and claims of the present application, the "lower" in "lower alkyl" and "lower alkoxy" refers to C1 to C4 (1 to 4 carbon atoms).

It is preferable that A ₁ and A ₂ in the formula (1) are each independently a naphthyl group which may have a substituent selected from the group consisting of a C1-4 alkoxy group having a sulfo group, a hydroxy group, and a sulfo group, or a phenyl group which may have a substituent, and it is more preferable that A ₁ and A ₂ are each independently a naphthyl group which may have a substituent selected from the group consisting of a C1-4 alkoxy group having a sulfo group, a hydroxy group, and a sulfo group.

In the formula (1), R ₁ to R ₁₂ each independently represent a hydrogen atom or a substituent. The substituent is not particularly limited, but may be the same as that described above in the section on the naphthyl group which may have a substituent.

In the formula (1), it is preferred that R ₁ , R ₂ , R ₁₁ and R ₁₂ are each independently a hydrogen atom, a C1-4 alkyl group or a C1-4 alkoxy group, and R ₃ to R ₁₀ are each independently a hydrogen atom, a C1-4 alkyl group, a C1-4 alkoxy group or a C1-4 alkoxy group having a sulfo group.

In the formula (1), the phenyl group which may have a substituent is preferably the formula (2). In the formula (2), one of R ₁₃ or R ₁₄ is a sulfo group, a carboxy group, or a C1-4 alkoxy group having a sulfo group, and the other is a hydrogen atom, a sulfo group, a carboxy group, a C1-4 alkoxy group having a sulfo group, a C1-4 alkyl group, a C1-4 alkoxy group, a halogen atom, a nitro group, an amino group, a C1-4 alkyl-substituted amino group, or a C1-4 alkyl-substituted acylamino group; it is preferable that one of R ₁₃ or R ₁₄ is a sulfo group or a carboxy group, and the other is a hydrogen atom, a sulfo group, a carboxy group, a methyl group, or a methoxy group. Furthermore, * in the formula (2) indicates the bonding position with the terminal amide group in the formula (1).

In the formula (1), the naphthyl group which may have a substituent is preferably represented by the formula (3). In the formula (3), R ₁₅ is a hydrogen atom, a C1-4 alkoxy group having a sulfo group, a hydroxy group, or a sulfo group, and is preferably a hydrogen atom. q is an integer of 1 to 3, and is preferably 2. In the formula (3), * indicates the bonding position with the terminal amide group in the formula (1).

In the formula (1), it is preferable that R ₃ to R ₁₀ each independently represent a group selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, a methoxy group, and a 3-sulfopropoxy group.

The formula (1) is preferably represented by the formula (4): In the formula (4), A ₁ , A ₂ , R ₁ to R ₁₂ , m, n, and p may be the same as those in the formula (1).

In the formula (4), it is preferred that A ₁ and A ₂ are each independently a naphthyl group which may have a substituent selected from the group consisting of a C1-4 alkoxy group having a sulfo group and a sulfo group, or a C1-4 alkoxy group having a sulfo group, a C1-4 alkoxy group, a carboxy group, a halogen atom, a nitro group, a sulfo group, a substituted or unsubstituted amino group, or a phenyl group which may have an amido group; either A ₁ or A ₂ is a naphthyl group which may have a substituent selected from the group consisting of a C1-4 alkoxy group having a sulfo group and a sulfo group; m, n, and p are each independently 0 or 1, and either m or n is 1; R ₁ , R ₂ , R ₁₁ , and R ₁₂ are each independently a hydrogen atom, a C1-4 alkyl group, or a C1-4 alkoxy group; and R ₃ to R ₁₀ are each independently a hydrogen atom, a C1-4 alkyl group, a C1-4 alkoxy group, or a C1-4 alkoxyl group having a sulfo group. Furthermore, it is more preferable that A ₁ and A ₂ are each independently a naphthyl group which may have a substituent selected from the group consisting of a C1-4 alkoxy group having a sulfo group and a sulfo group, or a phenyl group which may have a carboxy group, a halogen atom or a sulfo group, either A ₁ or A ₂ is a naphthyl group which may have a substituent selected from the group consisting of a C1-4 alkoxy group having a sulfo group and a sulfo group, m, n and p are each independently 0 or 1 and either m or n is 1, R ₁ , R ₂ , R ₁₁ and R ₁₂ are each independently a hydrogen atom, a methyl group or a methoxy group, and R ₃ to R ₁₀ are each independently a hydrogen atom, a methyl group, a methoxy group or a 3-sulfopropoxy group. Furthermore, it is particularly preferred that _A1 and _A2 are each independently a naphthyl group which may have a substituent selected from the group consisting of a 3-sulfopropoxy group and a sulfo group, m, n, and p are each independently 0 or 1, and either m or n is 1, _R1 , _R2 , _R11 , and _R12 are each independently a hydrogen atom, a methyl group, or a methoxy group, and _R3 to _R10 are each independently a hydrogen atom, a methyl group, a methoxy group, or a 3-sulfopropoxy group. Furthermore, it is highly preferred that _A1 and _A2 are each 6,8-disulfonaphthalene or 6-sulfo-8-(3-sulfopropoxy)naphthalene, m, n, and p are each independently 0 or 1, and either m or n is 1, _R1 , _R2 , _R11 , and _R12 are each independently a hydrogen atom, a methyl group, or a methoxy group, and _R3 to _R10 are each independently a hydrogen atom, a methyl group, a methoxy group, or a 3-sulfopropoxy group. Furthermore, it is most preferable that _A1 and _A2 are each 6,8-disulfonaphthalene or 6-sulfo-8-(3-sulfopropoxy)naphthalene, n is 1, _R1 , _R2 , _R11 , and _R12 are each independently a hydrogen atom, a methyl group, or a methoxy group, and _R3 to _R10 are each independently a hydrogen atom, a methyl group, a methoxy group, or a 3-sulfopropoxy group.

In one embodiment, p is 0. In one embodiment, p is 1.

Next, specific examples of the azo compound or salt thereof represented by the formula (1) where p is 0 are given below. In the formula, the sulfo group, carboxy group and hydroxy group are represented in the form of free acid.

Next, specific examples of the azo compound or salt thereof represented by the formula (1) where p is 1 are given below. In the formula, the sulfo group, carboxy group and hydroxy group are represented in the form of free acid.

The azo compound represented by formula (1) may be in the form of a free acid or a salt. Examples of such salts include alkali metal salts such as lithium salts, sodium salts, and potassium salts, ammonium salts, and organic salts such as amine salts. Sodium salts are preferred.

The azo compound represented by formula (1) or its salt can be produced by diazotization and coupling in accordance with the conventional azo dye production method described in Non-Patent Document 1, followed by reaction with a ureidating agent such as that described in Patent Document 3.

The specific manufacturing method is shown below.

Amino Compound on the _A1 Side When m is 1 An aniline which may have a substituent as represented by the following formula (L1) is reacted with an acid chloride represented by the following formula (L2) in the same manner as in Patent Document 7, followed by a reduction reaction to obtain an aminobenzoylaniline represented by the following formula (L12).

In the formula (L1), _A1 has the same meaning as in the formula (1). In the formula (L2), _R1 and _R2 have the same meaning as in the formula (1). In the formula (L12), _A1 , _R1 and _R2 have the same meaning as in the formula (1).

Next, the aniline represented by the above formula (L12) is diazotized in the same manner as in Non-Patent Document 1, and coupled with the aniline represented by the following formula (L3) to obtain a monoazoamino compound represented by the following formula (L123).

In the formula (L3), R ₃ and R ₄ have the same meanings as in the formula (1). In the formula (L123), A ₁ and R ₁ to R ₄ have the same meanings as in the formula (1).

Next, the monoazoamino compound represented by the above formula (L123) is diazotized in the same manner as in Non-Patent Document 1, and coupled with an aniline of the following formula (L4) to obtain a disazoamino compound represented by the following formula (L1234).

In the above formula (L3), _R5 and _R6 have the same meanings as in the above formula (1). In the above formula (L1234), _A1 and _R1 to _R6 have the same meanings as in the above formula (1).

Amino Compound on the _A1 Side When m is 0 An aniline represented by the following formula (L1), which may have a substituent, is diazotized in the same manner as in Non-Patent Document 1, and coupled with an aniline of the above formula (L3), to obtain a monoazoamino compound represented by the following formula (L13).

In the formula (L1), A ₁ has the same meaning as in the formula (1). In the formula (L13), A ₁ and R ₃ to R ₄ have the same meaning as in the formula (1).

Next, the monoazoamino compound represented by the above formula (L13) is diazotized in the same manner as in Non-Patent Document 1, and coupled with the aniline of the above formula (L4) to obtain a disazoamino compound represented by the following formula (L134).

In the above formula (L134), A ₁ and R ₃ to R ₆ have the same meanings as in the above formula (1).

Amino Compound on _A2 Side When p is 1 and n is 1 An aniline having a substituent as represented by the following formula (R1) is reacted with an acid chloride represented by the following formula (R2) in the same manner as in Patent Document 1, followed by a reduction reaction to obtain an aminobenzoylaniline represented by the following formula (R12).

In the above formula (R1), _A2 has the same meaning as in the above formula (1). In the above formula (R2), _R11 and _R12 have the same meaning as in the above formula (1). In the above formula (R12), _A2 , _R11 and _R12 have the same meaning as in the above formula (1).

Next, the aniline represented by the above formula (R12) is diazotized in the same manner as in Non-Patent Document 1, and coupled with the aniline represented by the following formula (R3) to obtain a monoazoamino compound represented by the following formula (R123).

In the formula (R3), R ₉ and R ₁₀ have the same meanings as in the formula (1). In the formula (R123), A ₂ and R ₉ to R ₁₂ have the same meanings as in the formula (1).

Next, the monoazoamino compound represented by the above formula (R123) is diazotized in the same manner as in Non-Patent Document 1, and coupled with an aniline of the following formula (R4) to obtain a disazoamino compound represented by the following formula (R1234).

In the above formula (R4), R ₇ and R ₈ have the same meanings as in the above formula (1). In the above formula (R1234), A ₂ and R ₇ to R ₁₂ have the same meanings as in the above formula (1).

Amino Compound on _A2 Side When p is 1 and n is 0 An aniline which may have a substituent and is represented by the following formula (R1) is diazotized in the same manner as in Non-Patent Document 1, and coupled with an aniline of the above formula (R3) to obtain a monoazoamino compound represented by the following formula (R13).

In the formula (R1), _A2 has the same meaning as in the formula (1). In the formula (R13), _A2 and _R9 to _R10 have the same meaning as in the formula (1).

Next, the monoazoamino compound represented by the above formula (R13) is diazotized in the same manner as in Non-Patent Document 1, and coupled with the aniline of the above formula (R4) to obtain a disazoamino compound represented by the following formula (R134).

In the above formula (R134), A ₁ and R ₇ to R ₁₀ have the same meanings as in the above formula (1).

Amino Compound on _A2 Side When p is 0 and n is 1 An aniline which may have a substituent as represented by the following formula (R1) is reacted with an acid chloride represented by the following formula (R2) in the same manner as in Patent Document 7, followed by a reduction reaction to obtain an aminobenzoylaniline represented by the following formula (R12).

In the above formula (R1), _A2 has the same meaning as in the above formula (1). In the above formula (R2), _R11 and _R12 have the same meaning as in the above formula (1). In the above formula (R12), _A2 , _R11 and _R12 have the same meaning as in the above formula (1).

Next, the aniline represented by the above formula (R12) is diazotized in the same manner as in Non-Patent Document 1, and coupled with the aniline represented by the following formula (R4) to obtain a monoazoamino compound represented by the following formula (R124).

In the formula (R4), _R7 and _R8 have the same meanings as in the formula (1). In the formula (R124), _A2 , _R7 , _R8 , _R9 , _R11 , and _R12 have the same meanings as in the formula (1).

Amino Compound on _A2 Side When p is 0 and n is 0 An aniline which may have a substituent and is represented by the following formula (R1) is diazotized in the same manner as in Non-Patent Document 1, and coupled with an aniline of the above formula (R4) to obtain a monoazoamino compound represented by the following formula (R14).

In the formula (R1), _A2 has the same meaning as in the formula (1). In the formula (R14), _A2 , _R7 and _R8 have the same meaning as in the formula (1).

The above-mentioned A1 _- side amino compound (L1234) or (L134) and the above-mentioned A2 _- side amino compound (R1234), (R134), (R124), or (R14) are reacted with a ureidating agent (for example, 4-nitrophenyl chloroformate) to obtain the azo compound of formula (1) ([m, n, p] = [1,1,1], [1,0,1], [1,1,0], [1,0,0], [0,1,1], [0,0,1], [0,1,0], or [0,0,0]).

The diazotization process can be carried out either by the conventional method, in which a nitrite such as sodium nitrite is mixed with an aqueous solution or suspension of the diazo component in a mineral acid such as hydrochloric acid or sulfuric acid, or by the inverse method, in which a nitrite is added to a neutral or weakly alkaline aqueous solution of the diazo component and then mixed with a mineral acid. The appropriate temperature for diazotization is -10 to 40°C. The coupling process with anilines is preferably carried out by mixing an aqueous acidic solution of hydrochloric acid, acetic acid, or the like with each of the above diazo solutions, at a temperature of -10 to 40°C and acidic conditions of pH 2 to 7.

The azo compound obtained by coupling can be precipitated by acid precipitation or salt precipitation and filtered, or it can be carried to the next step as a solution or suspension. If the diazonium salt is poorly soluble and forms a suspension, it can be filtered and used as a press cake in the next coupling step.

Specific conditions for the ureidation reaction using phenyl chloroformate are as shown on page 57 of Patent Document 3, with a temperature of 10 to 90°C and a pH of 3 to 11 being preferred, with 20 to 80°C and a pH of 4 to 10 being more preferred, and 20 to 70°C and a pH of 6 to 9 being particularly preferred. Ureidation agents that can be used include, but are not limited to, 4-nitrophenyl chloroformate, phenyl chloroformate, phosgene, triphosgene, ethyl chloroformate, butyl chloroformate, isobutyl chloroformate, 4-fluorophenyl chloroformate, 4-chlorophenyl chloroformate, 4-bromophenyl chloroformate, diphenyl carbonate, bis(2-methoxyphenyl) carbonate, bis(pentafluorophenyl) carbonate, bis(4-nitrophenyl) carbonate, and 1,1'-carbonyldiimidazole. The ureidating agent is preferably phenyl chloroformate, 4-nitrophenyl chloroformate, 4-chlorophenyl chloroformate, diphenyl carbonate, or bis(4-nitrophenyl) carbonate, more preferably phenyl chloroformate or 4-nitrophenyl chloroformate.

After the ureidation reaction is complete, the resulting azo compound of formula (1) is precipitated by salting out and filtered. If purification is required, the salting out process can be repeated or the compound can be precipitated from water using an organic solvent. Examples of organic solvents used for purification include water-soluble organic solvents such as alcohols (e.g., methanol, ethanol) and ketones (e.g., acetone).

The aromatic amines represented by A ₁ -NH ₂ (L1) and A ₂ -NH ₂ (R1), which are starting materials for synthesizing the azo compound represented by the formula (1), are naphthylamines or anilines.

It is preferable to use naphthylamines containing one or more groups selected from the group consisting of a hydrogen atom, a lower alkoxy group having a sulfo group, a hydroxy group, and a sulfo group. Examples of naphthylamines include 4-aminonaphthalenesulfonic acid, 7-aminonaphthalene-3-sulfonic acid, 1-aminonaphthalene-6-sulfonic acid, 1-aminonaphthalene-7-sulfonic acid, 7-aminonaphthalene-1,3-disulfonic acid, 6-aminonaphthalene-1,3-disulfonic acid, 7-aminonaphthalene-1,5-disulfonic acid, and 7-aminonaphthalene-1,3,6-trisulfonic acid. Preferred are 7-aminonaphthalene-3-sulfonic acid, 6-aminonaphthalene-1,3-disulfonic acid, 7-aminonaphthalene-1,4-disulfonic acid, 7-aminonaphthalene-1,5-disulfonic acid, 2-amino-8-hydroxy-naphthalene-6-sulfonic acid, 3-amino-8-hydroxynaphthalene-6-sulfonic acid, 1-aminonaphthalene-3,6,8-trisulfonic acid, 2-amino-5-hydroxynaphthalene-1,7-disulfonic acid, and 1-aminonaphthalene-3,8-disulfonic acid. Examples of naphthylamines having a sulfo group and a lower alkoxy group having a sulfo group include 7-amino-3-(3-sulfopropoxy)naphthalene-1-sulfonic acid, 7-amino-3-(4-sulfobutoxy)naphthalene-1-sulfonic acid, 7-amino-4-(3-sulfopropoxy)naphthalene-2-sulfonic acid, 7-amino-4-(4-sulfobutoxy)naphthalene-2-sulfonic acid, 6-amino- 2-amino-5-(3-sulfopropoxy)naphthalene-1,7-disulfonic acid, 6-amino-4-(3-sulfopropoxy)naphthalene-2-sulfonic acid, 6-amino-4-(4-sulfobutoxy)naphthalene-2-sulfonic acid, 2-amino-5-(3-sulfopropoxy)naphthalene-1,7-disulfonic acid, 6-amino-4-(3-sulfopropoxy)naphthalene-2,7-disulfonic acid, and 7-amino-3-(3-sulfopropoxy)naphthalene-1,5-disulfonic acid.

Anilines include 4-aminobenzenesulfonic acid, 3-aminobenzenesulfonic acid, 2-aminobenzenesulfonic acid, 4-aminobenzoic acid, 2-amino-5-methylbenzenesulfonic acid, 2-amino-5-ethylbenzenesulfonic acid, 2-amino-5-propylbenzenesulfonic acid, 2-amino-5-butylbenzenesulfonic acid, 4-amino-3-methylbenzenesulfonic acid, 4-amino-3-ethylbenzenesulfonic acid, 4-amino-3-propylbenzenesulfonic acid, 4-amino-3-butylbenzenesulfonic acid, and 2-amino-5-methoxybenzenesulfonic acid. benzenesulfonic acid, 2-amino-5-ethoxybenzenesulfonic acid, 2-amino-5-propoxybenzenesulfonic acid, 2-amino-5-butoxybenzenesulfonic acid, 4-amino-3-methoxybenzenesulfonic acid, 4-amino-3-ethoxybenzenesulfonic acid, 4-amino-3-propoxybenzenesulfonic acid, 4-amino-3-butoxybenzenesulfonic acid, 2-amino-4-sulfobenzoic acid, 2-amino-5-sulfobenzoic acid, 4-amino-3-sulfobenzoic acid, 5-amino-2-chlorobenzoic acid, 5-aminoisophthalic acid, 2-amino-5- Chlorobenzenesulfonic acid, 2-amino-5-bromobenzenesulfonic acid, 2-amino-5-nitrobenzenesulfonic acid, 2,5-diaminobenzenesulfonic acid, 2-amino-5-dimethylaminobenzenesulfonic acid, 2-amino-5-diethylaminobenzenesulfonic acid, 5-acetamido-2-aminobenzenesulfonic acid, 4-aminobenzene-1,3-disulfonic acid, 2-aminobenzene-1,4-disulfonic acid, 4-amino-2-methylbenzenesulfonic acid, 2-(4-aminophenoxy)ethane-1-sulfonic acid, 3-(4-aminophenoxy)ethane-1-sulfonic acid L) Propane-1-sulfonic acid, 4-(4-aminophenoxy)butane-1-sulfonic acid, 2-(3-aminophenoxy)ethane-1-sulfonic acid, 3-(3-aminophenoxy)propane-1-sulfonic acid, 4-(3-aminophenoxy)butane-1-sulfonic acid, 2-amino-5-(2-sulfoethoxy)benzenesulfonic acid, 2-amino-5-(3-sulfopropoxy)benzenesulfonic acid, 2-amino-5-(4-sulfobutoxy)benzenesulfonic acid, 2-amino-5-(2-sulfoethoxy)benzoic acid, 2-amino-5-(3-sulfopropoxy) 4-amino-3-(2-sulfoethoxy)benzoic acid, 4-amino-3-(3-sulfopropoxy)benzenesulfonic acid, 4-amino-3-(4-sulfobutoxy)benzenesulfonic acid, 4-amino-3-(2-sulfoethoxy)benzoic acid, 4-amino-3-(3-sulfopropoxy)benzoic acid, 4-amino-3-(4-sulfobutoxy)benzoic acid, 2-(4-amino-3-methylphenoxy)ethane-1-sulfonic acid, 3-(4-amino-3-methylphenoxy)prop 4-(4-amino-3-methylphenoxy)butane-1-sulfonic acid, 2-(4-amino-3-ethylphenoxy)ethane-1-sulfonic acid, 3-(4-amino-3-ethylphenoxy)propane-1-sulfonic acid, 4-(4-amino-3-ethylphenoxy)butane-1-sulfonic acid, 2-(4-amino-3-propylphenoxy)ethane-1-sulfonic acid, 3-(4-amino-3-propylphenoxy)propane-1-sulfonic acid, 4-(4-amino-3-propylphenoxy)butane-1-sulfonic acid, 2-(4-amino-3 4-(4-amino-3-butylphenoxy)ethane-1-sulfonic acid, 3-(4-amino-3-butylphenoxy)propane-1-sulfonic acid, 4-(4-amino-3-butylphenoxy)butane-1-sulfonic acid, 2-(4-amino-3-methoxyphenoxy)ethane-1-sulfonic acid, 3-(4-amino-3-methoxyphenoxy)propane-1-sulfonic acid, 4-(4-amino-3-methoxyphenoxy)butane-1-sulfonic acid, 2-(4-amino-3-ethoxyphenoxy)ethane-1-sulfonic acid, 3-(4-amino-3-ethoxyphenoxy)propane-1-sulfonic acid Examples of suitable aromatic amines include 4-(4-amino-3-ethoxyphenoxy)butane-1-sulfonic acid, 2-(4-amino-3-propoxyphenoxy)ethane-1-sulfonic acid, 3-(4-amino-3-propoxyphenoxy)propane-1-sulfonic acid, 4-(4-amino-3-propoxyphenoxy)butane-1-sulfonic acid, 2-(4-amino-3-butoxyphenoxy)ethane-1-sulfonic acid, 3-(4-amino-3-butoxyphenoxy)propane-1-sulfonic acid, and 4-(4-amino-3-butoxyphenoxy)butane-1-sulfonic acid. The amino group of these aromatic amines may be protected. An example of a protecting group is an ω-methanesulfonic group.

The aromatic amines (L3), (L4), (R3), and (R4) that are primary and secondary couplers include aniline, 2-methylaniline, 2-ethylaniline, 2-propylaniline, 2-butylaniline, 3-methylaniline, 3-ethylaniline, 3-propylaniline, 3-butylaniline, 2,5-dimethylaniline, 2,5-diethylaniline, 2-methoxyaniline, 2-ethoxyaniline, 2-propoxyaniline, 2-butoxyaniline, 3-methoxyaniline, 3-ethoxyaniline, 3-propoxyaniline, 3-butoxyaniline, 2-methoxy-5-methylaniline, 2,5-Dimethoxyaniline, 3,5-Dimethylaniline, 2,6-Dimethylaniline, 3,5-Dimethoxyaniline, 3-(2-amino-4-methylphenoxy)propane-1-sulfonic acid, 3-(2-aminophenoxy)propane-1-sulfonic acid, 4-(2-amino-4-methylphenoxy)butane-1-sulfonic acid, 4-(2-aminophenoxy)butane-1-sulfonic acid, 2-(2-amino-4-methylphenoxy)ethane-1-sulfonic acid, 2-(2-aminophenoxy)ethane-1-sulfonic acid, 3-(3-amino-4-methylphenoxy)propane-1-sulfonic acid, 3-(3-amino phenoxy)propane-1-sulfonic acid, 4-(3-amino-4-methylphenoxy)butane-1-sulfonic acid, 4-(3-aminophenoxy)butane-1-sulfonic acid, 2-(3-amino-4-methylphenoxy)ethane-1-sulfonic acid, 2-(3-aminophenoxy)ethane-1-sulfonic acid, 3-(2-amino-4-methoxyphenoxy)propane-1-sulfonic acid, 4-(2-amino-4-methoxyphenoxy)butane-1-sulfonic acid, 2-(2-amino-4-methoxyphenoxy)ethane-1-sulfonic acid, 3-(3-amino-4-methoxyphenoxy)propane-1-sulfonic acid, 4- Examples of suitable aromatic amines include (3-amino-4-methoxyphenoxy)butane-1-sulfonic acid, 2-(3-amino-4-methoxyphenoxy)ethane-1-sulfonic acid, 3-(2-amino-4-ethoxyphenoxy)propane-1-sulfonic acid, 4-(2-amino-4-ethoxyphenoxy)butane-1-sulfonic acid, 2-(2-amino-4-ethoxyphenoxy)ethane-1-sulfonic acid, 3-(3-amino-4-ethoxyphenoxy)propane-1-sulfonic acid, 4-(3-amino-4-ethoxyphenoxy)butane-1-sulfonic acid, and 2-(3-amino-4-ethoxyphenoxy)ethane-1-sulfonic acid. The amino group of these aromatic amines may be protected. An example of a protecting group is an ω-methanesulfonic group.

Examples of acid chlorides (L2) and (R2) include 4-nitrobenzoyl chloride, 3-methyl-4-nitrobenzoyl chloride, 2-methyl-4-nitrobenzoyl chloride, 3-ethyl-4-nitrobenzoyl chloride, 2-ethyl-4-nitrobenzoyl chloride, 3-propyl-4-nitrobenzoyl chloride, 2-propyl-4-nitrobenzoyl chloride, 3-butyl-4-nitrobenzoyl chloride, 2-butyl-4-nitrobenzoyl chloride, 3-methoxy-4-nitrobenzoyl chloride, 3-ethoxy-4-nitrobenzoyl chloride, 3-propoxy-4-nitrobenzoyl chloride, 3-butoxy-4-nitrobenzoyl chloride, 2-methoxy-4-nitrobenzoyl chloride, 2-ethoxy-4-nitrobenzoyl chloride, 2-propoxy-4-nitrobenzoyl chloride, and 2-butoxy-4-nitrobenzoyl chloride.

<Dye-based polarizing film>
The dye-based polarizing film of the present invention contains, in a substrate, an azo compound represented by formula (1) or a salt thereof as a dichroic dye. The dye-based polarizing film may be either a polarizing film exhibiting neutral gray (hereinafter also referred to as a "neutral gray polarizing film") or a color polarizing film, with a neutral gray polarizing film being preferred. Here, "neutral gray" means that when two polarizing films are superimposed so that their orientation directions are perpendicular to each other (hereinafter also referred to as "orthogonal orientation"), the transmittance for each wavelength in the visible light wavelength range (400 to 700 nm) is 1% or less, preferably 0.4% or less.

The dye-based polarizing film of the present invention contains, as a dichroic dye, one or a combination of multiple azo compounds represented by formula (1) above or salts thereof, and may further contain, as necessary, one or more organic dyes having a structure other than the azo compounds or salts thereof (hereinafter also referred to as "other organic dyes"). There are no particular restrictions on the other organic dyes, but they are preferably dyes with high dichroic properties that have absorption characteristics in a wavelength range different from the absorption wavelength range of the azo compound represented by formula (1) above or salts thereof. Representative examples of other organic dyes include CI Direct Yellow 12, CI Direct Yellow 28, CI Direct Yellow 44, CI Direct Orange 26, CI Direct Orange 39, CI Direct Orange 71, CI Direct Orange 107, CI Direct Red 2, CI Direct Red 31, CI Direct Red 79, CI Direct Red 81, CI Direct Red 247, CI Direct Green 80, and CI Direct Green 59, as well as dyes described in Patent Documents 1 to 6. However, depending on the purpose, it is preferable to use dyes developed for polarizing plates such as those described in Patent Documents 1 to 6. These organic dyes are used as free acids, alkali metal salts (e.g., sodium salts, potassium salts, and lithium salts), ammonium salts, or salts of amines.

When other organic dyes are used in combination, the type of organic dye to be blended will vary depending on whether the intended polarizing film is, for example, a neutral gray polarizing film, a color polarizing film for liquid crystal projectors, or other color polarizing films. There are no particular limitations on the blending ratio, but generally, it is preferable to use a total of 0.01 to 100 parts by weight of at least one other organic dye per 1 part by weight of the azo compound of formula (1) or its salt, with a range of 0.1 to 10 parts by weight being even more preferable.

When the desired polarizing film is a neutral gray polarizing film, the types and blending ratios of other organic dyes used in combination are adjusted so that the resulting polarizing film has little color leakage in the visible light wavelength range, for example, so that the average single transmittance in the visible light range (400 to 700 nm) is 39% or more and the average transmittance in the orthogonal direction for each wavelength is 1.0% or less, preferably 0.4% or less.

When the desired polarizing film is a color polarizing film, the types and blending ratios of other organic dyes used in combination are adjusted so that the resulting polarizing film has a high single-plate average light transmittance in a specific wavelength range and a low average light transmittance in the orthogonal direction, for example, so that it has a single-plate average light transmittance of 39% or more and an average light transmittance in the orthogonal direction of 0.4% or less in a specific wavelength range.

Dye-based polarizing films can be produced by incorporating a dichroic dye containing an azo compound represented by formula (1) or its salt, and optionally other organic dyes, into a substrate for the polarizing film (e.g., a polymer film, hereinafter also referred to as "polarizing film substrate") and orienting it using a known method, mixing it with liquid crystals, or orienting it using a coating method.

The polarizing film substrate is preferably a hydrophilic polymer film, and is preferably a film made of polyvinyl alcohol resin or its derivatives. Specific examples of polarizing film substrates include polyvinyl alcohol resin or its derivatives, and those modified with olefins such as ethylene and propylene, or unsaturated carboxylic acids such as crotonic acid, acrylic acid, methacrylic acid, and maleic acid. Films made of polyvinyl alcohol resin or its derivatives are preferred as polarizing film substrates from the viewpoint of dye adsorption and orientation. The thickness of the polarizing film substrate is typically 10 to 100 μm, and preferably 20 to 80 μm.

When the polarizing film substrate is a polymer film, the azo compound of formula (1) or its salt is typically incorporated into the polymer film by dyeing the polymer film. Dyeing is typically performed as follows: First, a dye bath is prepared by dissolving the azo compound of formula (1) or its salt, and, if necessary, other organic dyes, in water. The dye concentration in the dye bath is not particularly limited, but is typically selected from the range of approximately 0.001 to 10% by weight. If necessary, a dyeing assistant may also be used; for example, it is preferable to use Glauber's salt at a concentration of approximately 0.1 to 10% by weight. The polymer film can be immersed in the dye bath prepared in this manner for, for example, 1 to 10 minutes to dye the film. The dyeing temperature is preferably approximately 30 to 80°C.

Orientation of the azo compound represented by formula (1) or its salt is achieved by stretching a polymer film dyed with a dichroic dye. The stretching ratio is generally 2 to 8 times, but is not limited thereto. It is preferably 3 to 7.5 times, and more preferably 4 to 7 times. Any known stretching method, such as a wet method or a dry method, may be used. Stretching of the polymer film may be performed before dyeing, if necessary. In this case, the water-soluble dye is oriented at the time of dyeing. The polymer film containing and oriented with the water-soluble dye may be subjected to post-treatment, such as boric acid treatment, by a known method, if necessary. This post-treatment is performed to improve the light transmittance and polarization degree of the polarizing film. The conditions for the boric acid treatment vary depending on the type of polymer film and the type of dye used, but generally the boric acid concentration of the boric acid aqueous solution is, for example, 0.1 to 15% by mass, preferably 1 to 10% by mass, and the treatment is carried out by immersion for 0.5 to 10 minutes at a temperature of 30 to 80° C., preferably 40 to 75° C. If necessary, a fixing treatment may also be carried out in combination with an aqueous solution containing a cationic polymer compound.

Applications of the dye-based polarizing film of the present invention include, for example, liquid crystal projectors, calculators, clocks, notebook computers, word processors, liquid crystal televisions, car navigation systems, indoor and outdoor measuring instruments and displays, as well as lenses and eyeglasses. The dye-based polarizing film of the present invention has high polarization performance comparable to that of polarizing films using iodine and also has excellent durability. For this reason, it is particularly suitable for applications requiring high polarization performance and durability, such as various liquid crystal displays for in-vehicle and outdoor displays (e.g., displays for industrial instruments and wearable applications), and liquid crystal projectors.

<Dye-based polarizing plate>
The dye-based polarizing plate of the present invention can be obtained by laminating a transparent protective film on one or both sides of a dye-based polarizing film. The dye-based polarizing plate has excellent polarization performance and durability (moisture resistance, heat resistance, and light resistance) due to the inclusion of the dye-based polarizing film. Materials that are excellent in optical transparency and mechanical strength are preferred for forming the transparent protective film, and examples of such materials include cellulose acetate films, acrylic films, fluorine-based films such as tetrafluoroethylene/hexafluoropropylene copolymers, and films made of polyester resins, polyolefin resins, or polyamide resins. The transparent protective film is preferably a triacetyl cellulose (TAC) film or a cycloolefin film. The thickness of the protective film is typically preferably 20 to 200 μm.

In the dye-based polarizing plate of the present invention, the dye-based polarizing film and the transparent protective film can be bonded together using an adhesive. Examples of adhesives that can be used include polyvinyl alcohol-based adhesives, urethane emulsion-based adhesives, acrylic-based adhesives, and polyester-isocyanate-based adhesives, with polyvinyl alcohol-based adhesives being preferred.

A transparent protective layer may be further provided on the surface of the dye-based polarizing plate of the present invention. Examples of transparent protective layers include acrylic or polysiloxane-based hard coat layers and urethane-based protective layers. Furthermore, to further improve the single-plate light transmittance of the dye-based polarizing plate of the present invention, it is preferable to provide an antireflection layer (hereinafter also referred to as an "AR layer") on this transparent protective layer. The AR layer can be formed, for example, by vapor deposition or sputtering of a substance such as silicon dioxide or titanium oxide, or by thinly applying a fluorine-based substance. It is preferable that the dye-based polarizing plate further includes a support. The dye-based polarizing plate can also be used as an elliptical polarizing plate by attaching a retardation plate to the surface.

The dye-based polarizer of the present invention may be either a neutral gray polarizer or a color polarizer depending on the application.

The above-mentioned neutral gray polarizer has a neutral color, little color leakage in the orthogonal direction in the polarization range of visible light, excellent polarization performance, and is highly heat-resistant, preventing discoloration and deterioration of polarization performance even under high-temperature and high-humidity conditions, making it suitable for use in vehicles or outdoor displays.

Neutral gray polarizing plates for in-vehicle or outdoor displays are preferably polarizing plates composed of a dye-based polarizing film and a transparent protective film, to which an AR layer is attached to further improve the unit light transmittance, and polarizing plates with an AR layer and a support, in which both an AR layer and a support such as a transparent resin are attached, are more preferred. The AR layer can be attached on one or both sides of the polarizing plate. The support is preferably attached on one side of the polarizing plate, and may be attached directly to the polarizing plate, or the AR layer may be attached to the support. Polarizing plates with an AR layer and a support preferably have an AR layer/polarizing plate/support with an AR layer in this order. The support preferably has a flat surface for attaching the polarizing plate, and because it is for optical applications, it is preferably a transparent substrate. Transparent substrates are broadly divided into inorganic substrates and organic substrates, including inorganic substrates such as soda glass, borosilicate glass, quartz substrates, sapphire substrates, and spinel substrates, and organic substrates such as acrylic, polycarbonate, polyethylene terephthalate, polyethylene naphthalate, and cycloolefin polymers, with organic substrates being preferred. The thickness and size of the transparent substrate may be any desired size.

The above-mentioned color polarizing plate has excellent polarization performance and does not discolor or lose its polarization performance even under high temperature and humidity conditions, making it suitable for use in LCD projectors and display devices such as those mounted in cars and for outdoor displays.

Color polarizing plates for LCD projectors have brightness and excellent polarization performance, and in the required wavelength ranges for the polarizing plate (A. When using an ultra-high pressure mercury lamp: 420-500 nm for the blue channel, 500-580 nm for the green channel, and 600-680 nm for the red channel; B. Peak wavelengths when using a three-primary color LED lamp: 430-450 nm for the blue channel, 520-535 nm for the green channel, and 620-635 nm for the red channel), the average light transmittance of the single plate is 39% or more and the average light transmittance in the orthogonal direction is 0.4% or less. More preferably, the average light transmittance of the single plate in the required wavelength range for the polarizing plate is 41% or more and the average light transmittance in the orthogonal direction is 0.3% or less, and more preferably 0.2% or less. Even more preferably, the average light transmittance of the single plate in the required wavelength range for the polarizing plate is 42% or more and the average light transmittance in the orthogonal direction is 0.1% or less.

The single-plate average light transmittance is the average value of light transmittance in a specific wavelength range when natural light is incident on a single polarizing plate (hereinafter simply referred to as a "polarizing plate") that does not have an AR layer or a support such as a transparent glass plate. The orthogonal average light transmittance is the average value of light transmittance in a specific wavelength range when natural light is incident on two polarizing plates that are stacked so that their orientation directions are perpendicular to each other.

The polarizing film used in color polarizers for in-vehicle or outdoor displays may be a dye-based polarizer, optionally provided with a protective layer or AR layer and a support, similar to a neutral gray polarizer. A color polarizer with a support can be obtained, for example, by applying a transparent adhesive (pressure-sensitive adhesive) to the flat surface of the support and then attaching a dye-based polarizer to this coated surface. Alternatively, a transparent adhesive (pressure-sensitive adhesive) may be applied to the dye-based polarizer and then attaching a support to this coated surface. The adhesive (pressure-sensitive adhesive) is preferably an acrylic ester-based adhesive. When this dye-based polarizer is used as an elliptical polarizer, it is typically attached to the support on the retarder side, resulting in a layer order of dye-based polarizer/retarder/support. However, the polarizer side may also be attached to the support, resulting in a layer order of retarder/polarizer/support.

<Display device>
The display device of the present invention includes the dye-based polarizing film or dye-based polarizing plate described above. Examples of the display device include liquid crystal display devices and organic electroluminescence display devices. For example, the display device is used in displays for calculators, clocks, notebook computers, word processors, LCD televisions, car navigation systems, and indoor and outdoor measuring instruments and indicators. The display device is particularly suitable for in-vehicle or outdoor displays (e.g., industrial instrument displays and wearable devices) that require high polarization performance and durability. The dye-based polarizing film or dye-based polarizing plate included in the display device is preferably neutral gray.

In liquid crystal display devices, a dye-based polarizer is placed on either the entrance side or the exit side of the liquid crystal cell, or both. The dye-based polarizer may or may not be in contact with the liquid crystal cell, but from the perspective of durability, it is preferable that it is not in contact. When the dye-based polarizer is in contact with the liquid crystal cell on the exit side of the liquid crystal cell, the liquid crystal cell can serve as the support for the dye-based polarizer. When the dye-based polarizer is not in contact with the liquid crystal cell, it is preferable to use a dye-based polarizer with a support other than the liquid crystal cell. Furthermore, from the perspective of durability, it is preferable to place dye-based polarizers on both the entrance side and the exit side of the liquid crystal cell, and it is further preferable to place the polarizer surface of the dye-based polarizer facing the liquid crystal cell and the support surface facing the light source. Note that the entrance side of the liquid crystal cell refers to the light source side, and the opposite side is called the exit side.

The liquid crystal cell used in a liquid crystal display device is preferably an active matrix type, formed by sealing liquid crystal between a transparent substrate on which electrodes and TFTs (Thin Film Transistors) are formed and a transparent substrate on which an opposing electrode is formed. Light emitted from a light source such as a cold cathode tube lamp or white LED passes through a dye-based polarizer, then through the liquid crystal cell, a color filter, and another dye-based polarizer before being projected onto the display screen.

The present invention will be described in more detail below with reference to the following examples, which are merely illustrative and do not limit the present invention in any way. Percentages and parts in the examples are by weight unless otherwise specified.

(Example 1: Synthesis of the azo compound of the formula (6))
30.3 parts of 7-aminonaphthalene-1,3-disulfonic acid was added to 400 parts of water and dissolved with sodium hydroxide, and 20.5 parts of 4-nitrobenzoyl chloride was added and stirred for 6 hours at 40 to 60° C. Subsequently, 15.0 g of iron powder and 13 parts of 35% hydrochloric acid were added and stirred at 80° C. for 5 hours to complete the reaction. The iron powder was removed by filtration, and the filtrate was concentrated to obtain 33.9 parts of an aminobenzoylaminonaphthalene compound represented by the following formula (128).

33.9 parts of the obtained aminobenzoylaminonaphthalene compound (128) was added to 400 parts of water and dissolved with sodium hydroxide, and 5.5 parts of sodium nitrite was added, and 25.1 parts of 35% hydrochloric acid was added at 10 to 30°C, and the mixture was stirred at 10 to 30°C for 1 hour to perform diazotization. Subsequently, 9.7 parts of 2,5-dimethylaniline was added, and while stirring at 20 to 30°C, sodium carbonate was added to adjust the pH to 3, and the mixture was further stirred to complete the coupling reaction, and the precipitated target product was filtered and dried to obtain 26.7 parts of a monoazoamino compound represented by the following formula (129).

Next, 30.3 parts of 7-aminonaphthalene-1,3-disulfonic acid was added to 400 parts of water and dissolved with sodium hydroxide, and 6.9 parts of sodium nitrite was added, and 31.3 parts of 35% hydrochloric acid was added at 10 to 30°C, and the mixture was stirred for 1 hour at 10 to 30°C to perform diazotization. Subsequently, 12.1 parts of 2,5-dimethylaniline was added, and while stirring at 20 to 30°C, sodium carbonate was added to adjust the pH to 3, and the mixture was further stirred to complete the coupling reaction, and the precipitated target product was collected by filtration and dried to obtain 30.5 parts of a monoazoamino compound represented by the following formula (130).

30.5 parts of the obtained monoazoamino compound (130) was added to 400 parts of water and dissolved with sodium hydroxide, and 4.8 parts of sodium nitrite was added, and 21.9 parts of 35% hydrochloric acid was added at 10 to 30° C., and the mixture was stirred for 1 hour at 10 to 30° C. to diazotize. Subsequently, 9.6 parts of 2-methoxy-5-methylaniline was added, and while stirring at 20 to 30° C., sodium carbonate was added to adjust the pH to 3, and the mixture was further stirred to complete the coupling reaction, and the precipitated target product was filtered and dried to obtain 28.6 parts of a disazoamino compound represented by the following formula (131).

26.7 parts of the resulting monoazoamino compound (129) and 28.6 parts of the disazoamino compound (131) were added to 400 parts of water, dissolved with sodium hydroxide, and 9.9 parts of 4-nitrophenyl chloroformate was added. The mixture was stirred at 60-80°C for 5 hours to form a ureido compound. Salting out with sodium chloride was performed, and the precipitated target product was collected by filtration and dried to obtain 6.7 parts of the ureido compound represented by the above formula (6), an azo compound of the present invention. The maximum absorption wavelength of this compound in a 20% aqueous pyridine solution was 435 nm.

(Example 2: Synthesis of the azo compound of the formula (13))
30.3 parts of 7-aminonaphthalene-1,3-disulfonic acid was added to 400 parts of water and dissolved with sodium hydroxide, and 22.0 parts of 3-methyl-4-nitrobenzoyl chloride was added and stirred for 6 hours at 40 to 60° C. Subsequently, 15.0 g of iron powder and 13 parts of 35% hydrochloric acid were added and stirred at 80° C. for 5 hours to complete the reaction. The iron powder was removed by filtration, and the filtrate was concentrated to obtain 30.6 parts of an aminobenzoylaminonaphthalene compound represented by the following formula (132).

30.6 parts of the obtained aminobenzoylaminonaphthalene compound (132) was added to 400 parts of water and dissolved with sodium hydroxide, and 4.8 parts of sodium nitrite was added, and 21.9 parts of 35% hydrochloric acid was added at 10 to 30° C., and the mixture was stirred for 1 hour at 10 to 30° C. to perform diazotization. Subsequently, 17.2 parts of 3-(2-amino-4-methylphenoxy)propane-1-sulfonic acid was added, and while stirring at 20 to 30° C., sodium carbonate was added to adjust the pH to 4.0, and the mixture was further stirred to complete the coupling reaction. The precipitated target product was collected by filtration and dried to obtain 38.8 parts of a monoazoamino compound represented by the following formula (133).

Next, 30.3 parts of 7-aminonaphthalene-1,3-disulfonic acid was added to 400 parts of water and dissolved with sodium hydroxide, and 6.9 parts of sodium nitrite was added, and 31.3 parts of 35% hydrochloric acid was added at 10 to 30°C, and the mixture was stirred for 1 hour at 10 to 30°C to perform diazotization. Subsequently, 12.3 parts of 2-methoxyaniline was added, and while stirring at 20 to 30°C, sodium carbonate was added to adjust the pH to 3, and the mixture was further stirred to complete the coupling reaction, and the precipitated target product was collected by filtration and dried to obtain 26.2 parts of a monoazoamino compound represented by the following formula (134).

26.2 parts of the obtained monoazoamino compound (134) was added to 400 parts of water and dissolved with sodium hydroxide, and 4.1 parts of sodium nitrite was added, and 18.8 parts of 35% hydrochloric acid was added at 10 to 30° C., and the mixture was stirred for 1 hour at 10 to 30° C. to perform diazotization. Subsequently, 14.7 parts of 3-(2-amino-4-methylphenoxy)propane-1-sulfonic acid was added, and while stirring at 20 to 30° C., sodium carbonate was added to adjust the pH to 4, and the mixture was further stirred to complete the coupling reaction. The precipitated target product was filtered and dried to obtain 33.3 parts of a disazoamino compound represented by the following formula (135).

26.2 parts of the resulting monoazoamino compound (133) and 33.3 parts of the disazoamino compound (135) were added to 400 parts of water, dissolved with sodium hydroxide, and 9.7 parts of 4-nitrophenyl chloroformate was added. The mixture was stirred at 60-80°C for 5 hours to form a ureido compound. Salting out with sodium chloride was performed, and the precipitated target product was collected by filtration and dried to obtain 5.1 parts of the ureido compound represented by the above formula (13), an azo compound of the present invention. The maximum absorption wavelength of this compound in a 20% aqueous pyridine solution was 434 nm.

(Example 3: Synthesis of the azo compound of the formula (29))
42.2 parts of the aminobenzoylaminonaphthalene compound of the above formula (128) was added to 400 parts of water and dissolved with sodium hydroxide, and 6.9 parts of sodium nitrite was added, and 31.3 parts of 35% hydrochloric acid was added at 10 to 30° C., and the mixture was stirred for 1 hour at 10 to 30° C. to diazotize. Subsequently, 13.7 parts of 2-methoxy-5-methylaniline was added, and while stirring at 20 to 30° C., sodium carbonate was added to adjust the pH to 3, and the mixture was further stirred to complete the coupling reaction, and the precipitated target product was filtered and dried to obtain 42.8 parts of a monoazoamino compound represented by the following formula (136).

21.4 parts of the obtained monoazoamino compound (136) was added to 300 parts of water and dissolved with sodium hydroxide, and 2.8 parts of sodium nitrite was added, and 11.7 parts of 35% hydrochloric acid was added at 10 to 30° C., and the mixture was stirred for 1 hour at 20 to 30° C. to perform diazotization. Subsequently, 9.2 parts of 3-(2-amino-4-methylphenoxy)propane-1-sulfonic acid was added, and while stirring at 20 to 30° C., sodium carbonate was added to adjust the pH to 4.0, and the mixture was further stirred to complete the coupling reaction. The precipitated target product was filtered and dried to obtain 24.8 parts of a disazoamino compound represented by the following formula (137).

24.8 parts of the resulting disazoamino compound (137) and 21.4 parts of the compound represented by formula (136) were added to 500 parts of water, dissolved with sodium hydroxide, and 7.6 parts of 4-nitrophenyl chloroformate were added and stirred at 50-70°C for 8 hours to form a ureido compound. Salting out with sodium chloride was performed, and the precipitated target product was collected by filtration and dried to obtain 3.5 parts of the ureido compound represented by formula (29), an azo compound of the present invention. The maximum absorption wavelength of this compound in a 20% aqueous pyridine solution was 447 nm.

(Example 4: Synthesis of the azo compound of the formula (46))
36.1 parts of 6-amino-4-(3-sulfopropoxy)naphthalene-2-sulfonic acid was added to 400 parts of water and dissolved with sodium hydroxide, and 22.0 parts of 3-methyl-4-nitrobenzoyl chloride was added and stirred for 6 hours at 40 to 60° C. Subsequently, 15.0 g of iron powder and 13 parts of 35% hydrochloric acid were added and stirred at 80° C. for 5 hours to complete the reaction. The iron powder was removed by filtration, and the filtrate was concentrated to obtain 29.7 parts of an aminobenzoylaminonaphthalene compound represented by the following formula (138).

29.7 parts of the aminobenzoylaminonaphthalene compound of the above formula (138) was added to 400 parts of water and dissolved with sodium hydroxide, and 4.1 parts of sodium nitrite was added, and 18.8 parts of 35% hydrochloric acid was added at 10 to 30° C., and the mixture was stirred for 1 hour at 10 to 30° C. to diazotize. Subsequently, 8.2 parts of 2-methoxy-5-methylaniline was added, and while stirring at 20 to 30° C., sodium carbonate was added to adjust the pH to 3, and the mixture was further stirred to complete the coupling reaction, and the precipitated target product was filtered and dried to obtain 27.0 parts of a monoazoamino compound represented by the following formula (139).

27.0 parts of the obtained monoazoamino compound (139) was added to 400 parts of water and dissolved with sodium hydroxide, and 3.2 parts of sodium nitrite was added, and 13.1 parts of 35% hydrochloric acid was added at 20 to 30° C., and the mixture was stirred for 1 hour at 20 to 30° C. to perform diazotization. Subsequently, 5.8 parts of 2-methoxy-5-methylaniline was added, and while stirring at 20 to 30° C., sodium carbonate was added to adjust the pH to 3, and the mixture was further stirred to complete the coupling reaction, and the precipitated target product was filtered and dried to obtain 20.0 parts of a disazoamino compound represented by the following formula (140).

Next, 10.9 parts of 7-aminonaphthalene-1,3-disulfonic acid was added to 200 parts of water and dissolved with sodium hydroxide, and 2.5 parts of sodium nitrite was added, and 11.3 parts of 35% hydrochloric acid was added at 10 to 30°C, and the mixture was stirred for 1 hour at 10 to 30°C to perform diazotization. Subsequently, 4.9 parts of 2-methoxy-5-methylaniline was added, and while stirring at 20 to 30°C, sodium carbonate was added to adjust the pH to 3, and the mixture was further stirred to complete the coupling reaction, and the precipitated target product was collected by filtration and dried to obtain 11.3 parts of a monoazoamino compound represented by the following formula (141).

20.0 parts of the resulting disazoamino compound (140) and 11.3 parts of the monoazoamino compound (141) were added to 500 parts of water, dissolved with sodium hydroxide, and 5.0 parts of 4-nitrophenyl chloroformate were added and stirred at 50-70°C for 8 hours to form a ureido compound. Salting out with sodium chloride was performed, and the precipitated target product was collected by filtration and dried to obtain 4.0 parts of the ureido compound represented by formula (46), an azo compound of the present invention. The maximum absorption wavelength of this compound in a 20% aqueous pyridine solution was 448 nm.

(Example 5: Synthesis of the azo compound of the formula (54))
45.0 parts of the monoazoamino compound of formula (139) was added to 600 parts of water and dissolved with sodium hydroxide, and 4.8 parts of sodium nitrite was added, and 21.9 parts of 35% hydrochloric acid was added at 20 to 30° C., and the mixture was stirred at 20 to 30° C. for 1 hour to perform diazotization. Subsequently, 8.5 parts of 2,5-dimethylaniline was added, and while stirring at 20 to 30° C., sodium carbonate was added to adjust the pH to 3, and the mixture was further stirred to complete the coupling reaction. The precipitated target product was filtered and dried to obtain 27.1 parts of a disazoamino compound represented by the following formula (142).

Next, 14.2 parts of 6-aminonaphthalene-1,3-disulfonic acid was added to 300 parts of water and dissolved with sodium hydroxide, and 3.2 parts of sodium nitrite was added, and 14.7 parts of 35% hydrochloric acid was added at 10 to 30° C., and the mixture was stirred for 1 hour at 10 to 30° C. to perform diazotization. Subsequently, 6.4 parts of 2-methoxy-5-methylaniline was added, and while stirring at 20 to 30° C., sodium carbonate was added to adjust the pH to 3, and the mixture was further stirred to complete the coupling reaction. The precipitated target product was collected by filtration and dried to obtain 15.8 parts of a monoazoamino compound represented by the following formula (143).

27.1 parts of the resulting disazoamino compound (142) and 15.8 parts of the monoazoamino compound (143) were added to 500 parts of water, dissolved with sodium hydroxide, and 7.0 parts of 4-nitrophenyl chloroformate were stirred at 50-70°C for 8 hours to form a ureido compound. Salting out with sodium chloride was performed, and the precipitated target product was collected by filtration and dried to obtain 4.1 parts of the ureido compound represented by the above formula (54), an azo compound of the present invention. The maximum absorption wavelength of this compound in a 20% aqueous pyridine solution was 430 nm.

(Example 6: Synthesis of azo compound of formula (56))
25.3 parts of the aminobenzoylaminonaphthalene compound represented by the above formula (128) was added to 400 parts of water and dissolved with sodium hydroxide, and 4.1 parts of sodium nitrite was added, and 18.8 parts of 35% hydrochloric acid was added at 10 to 30° C., and the mixture was stirred for 1 hour at 10 to 30° C. to diazotize. Subsequently, 8.2 parts of 2-methyl-5-methoxyaniline was added, and while stirring at 20 to 30° C., sodium carbonate was added to adjust the pH to 3, and further stirring was continued to complete the coupling reaction, and the precipitated target product was filtered and dried to obtain 24.0 parts of a monoazoamino compound represented by the following formula (144).

Next, 25.3 parts of 2,4-disulfoaniline was added to 300 parts of water and dissolved with sodium hydroxide, and 6.9 parts of sodium nitrite was added, and 31.3 parts of 35% hydrochloric acid was added at 10 to 30°C, and the mixture was stirred for 1 hour at 10 to 30°C to perform diazotization. Subsequently, 12.1 parts of 2,5-dimethylaniline was added, and while stirring at 20 to 30°C, sodium carbonate was added to adjust the pH to 3, and the mixture was further stirred to complete the coupling reaction, and the precipitated target product was collected by filtration and dried to obtain 27.0 parts of a monoazoamino compound represented by the following formula (145).

27.0 parts of the obtained monoazoamino compound (144) was added to 400 parts of water and dissolved with sodium hydroxide, and 4.8 parts of sodium nitrite was added, and 21.9 parts of 35% hydrochloric acid was added at 10 to 30° C., and the mixture was stirred for 1 hour at 20 to 30° C. to perform diazotization. Subsequently, 9.6 parts of 2-methoxy-5-methylaniline was added, and while stirring at 20 to 30° C., sodium carbonate was added to adjust the pH to 3, and the mixture was further stirred to complete the coupling reaction, and the precipitated target product was filtered and dried to obtain 22.4 parts of a disazoamino compound represented by the following formula (146).

24.0 parts of the resulting monoazoamino compound (144) and 22.4 parts of the disazoamino compound (146) were added to 400 parts of water, dissolved with sodium hydroxide, and 8.4 parts of 4-nitrophenyl chloroformate was added. The mixture was stirred at 60-80°C for 5 hours to form a ureido compound. Salting out with sodium chloride was performed, and the precipitated target product was collected by filtration and dried to obtain 3.2 parts of the ureido compound represented by the above formula (56), an azo compound of the present invention. The maximum absorption wavelength of this compound in a 20% aqueous pyridine solution was 439 nm.

(Example 7: Synthesis of the azo compound of the formula (66))
13.7 parts of 4-aminobenzoic acid was added to 300 parts of water and dissolved with sodium hydroxide, and 20.5 parts of 4-nitrobenzoyl chloride was added and stirred for 6 hours at 40 to 60° C. Subsequently, 15.0 g of iron powder and 13 parts of 35% hydrochloric acid were added and stirred at 80° C. for 5 hours to complete the reaction. The iron powder was removed by filtration, and the filtrate was concentrated to obtain 17.9 parts of an aminobenzoylaminobenzoic acid compound represented by the following formula (147).

17.9 parts of the obtained aminobenzoylaminobenzoic acid compound (147) was added to 400 parts of water and dissolved with sodium hydroxide, and 4.8 parts of sodium nitrite was added, and 21.9 parts of 35% hydrochloric acid was added at 10 to 30°C, and the mixture was stirred at 10 to 30°C for 1 hour to perform diazotization. Subsequently, 17.2 parts of 3-(2-amino-4-methylphenoxy)propane-1-sulfonic acid was added, and while stirring at 20 to 30°C, sodium carbonate was added to adjust the pH to 4, and the mixture was further stirred to complete the coupling reaction, and the precipitated target product was collected by filtration and dried to obtain 25.1 parts of a monoazoamino compound represented by the following formula (148).

Next, 27.0 parts of the monoazoamino compound of the above formula (145) was added to 400 parts of water and dissolved with sodium hydroxide, and 4.8 parts of sodium nitrite was added, and 21.9 parts of 35% hydrochloric acid was added at 10 to 30° C., and the mixture was stirred for 1 hour at 20 to 30° C. to perform diazotization. Subsequently, 17.2 parts of 3-(2-amino-4-methylphenoxy)propane-1-sulfonic acid was added, and while stirring at 20 to 30° C., sodium carbonate was added to adjust the pH to 4, and the mixture was further stirred to complete the coupling reaction, and the precipitated target product was collected by filtration and dried to obtain 31.4 parts of a disazoamino compound represented by the following formula (149).

25.1 parts of the resulting monoazoamino compound (148) and 31.4 parts of the disazoamino compound (149) were added to 500 parts of water, dissolved with sodium hydroxide, and 9.8 parts of 4-nitrophenyl chloroformate was added. The mixture was stirred at 60-80°C for 5 hours to form a ureido compound. Salting out with sodium chloride was performed, and the precipitated target product was collected by filtration and dried to obtain 5.7 parts of the ureido compound represented by formula (66), an azo compound of the present invention. The maximum absorption wavelength of this compound in a 20% aqueous pyridine solution was 446 nm.

(Example 8: Synthesis of the azo compound of the formula (87))
17.0 parts of 2-chloro-4-aminobenzoic acid was added to 300 parts of water and dissolved with sodium hydroxide, and 20.5 parts of 4-nitrobenzoyl chloride was added and stirred for 6 hours at 40 to 60° C. Subsequently, 15.0 g of iron powder and 13 parts of 35% hydrochloric acid were added and stirred at 80° C. for 5 hours to complete the reaction. The iron powder was removed by filtration, and the filtrate was concentrated to obtain 21.8 parts of an aminobenzoylaminobenzoic acid compound represented by the following formula (150):

21.8 parts of the obtained aminobenzoylaminobenzoic acid compound (150) was added to 400 parts of water and dissolved with sodium hydroxide, and 5.2 parts of sodium nitrite was added, and 23.5 parts of 35% hydrochloric acid was added at 10 to 30°C, and the mixture was stirred for 1 hour at 10 to 30°C to perform diazotization. Subsequently, 10.3 parts of 2-methoxy-5-methylaniline was added, and while stirring at 20 to 30°C, sodium carbonate was added to adjust the pH to 3, and the mixture was further stirred to complete the coupling reaction, and the precipitated target product was filtered and dried to obtain 19.8 parts of a monoazoamino compound represented by the following formula (151).

19.8 parts of the resulting monoazoamino compound (150) and 34.7 parts of the disazoamino compound of formula (137) were added to 500 parts of water, dissolved with sodium hydroxide, and 8.4 parts of 4-nitrophenyl chloroformate was added. The mixture was stirred at 60-80°C for 8 hours to form a ureido compound. Salting out with sodium chloride was performed, and the precipitated target product was collected by filtration and dried to obtain 3.8 parts of the ureido compound represented by formula (87), an azo compound of the present invention. The maximum absorption wavelength of this compound in a 20% aqueous pyridine solution was 441 nm.

Example 9: Synthesis of azo compound of formula (92)
22.2 parts of 6-aminonaphthalene-2-sulfonic acid was added to 400 parts of the solution, dissolved with sodium hydroxide, and 20.5 parts of 4-nitrobenzoyl chloride was added and stirred for 6 hours at 40 to 60° C. Subsequently, 15.0 g of iron powder and 13 parts of 35% hydrochloric acid were added and stirred at 80° C. for 5 hours to complete the reaction. The iron powder was removed by filtration, and the filtrate was concentrated to obtain 20.5 parts of an aminobenzoylaminonaphthalene compound represented by the following formula (152):

20.5 parts of the obtained aminobenzoylaminonaphthalene compound (151) was added to 400 parts of water and dissolved with sodium hydroxide, and 4.1 parts of sodium nitrite was added, and 18.8 parts of 35% hydrochloric acid was added at 10 to 30°C, and the mixture was stirred for 1 hour at 10 to 30°C to perform diazotization. Subsequently, 8.2 parts of 2-methoxy-5-methylaniline was added, and while stirring at 20 to 30°C, sodium carbonate was added to adjust the pH to 3, and the mixture was further stirred to complete the coupling reaction, and the precipitated target product was collected by filtration and dried to obtain 17.7 parts of a monoazoamino compound represented by the following formula (153).

17.7 parts of the obtained monoazoamino compound (153) was added to 300 parts of water and dissolved with sodium hydroxide, and 2.5 parts of sodium nitrite was added, and 11.3 parts of 35% hydrochloric acid was added at 10 to 30° C., and the mixture was stirred for 1 hour at 20 to 30° C. to perform diazotization. Subsequently, 17.2 parts of 3-(2-amino-4-methylphenoxy)propane-1-sulfonic acid was added, and while stirring at 20 to 30° C., sodium carbonate was added to adjust the pH to 4, and the mixture was further stirred to complete the coupling reaction. The precipitated target product was filtered and dried to obtain 21.5 parts of a disazoamino compound represented by the following formula (154).

21.5 parts of the resulting disazoamino compound (154) and 14.8 parts of the monoazoamino compound of formula (148) above were added to 500 parts of water, dissolved with sodium hydroxide, and 5.8 parts of 4-nitrophenyl chloroformate was added. The mixture was stirred at 60-80°C for 8 hours to form a ureido compound. Salting out with sodium chloride was performed, and the precipitated target product was collected by filtration and dried to obtain 1.8 parts of the ureido compound of formula (92) above, an azo compound of the present invention. The maximum absorption wavelength of this compound in a 20% aqueous pyridine solution was 445 nm.

(Example 10: Synthesis of azo compound of formula (1002))
30.6 parts of the aminobenzoylaminonaphthalene compound (132) was added to 400 parts of water and dissolved with sodium hydroxide, and 4.8 parts of sodium nitrite was added, and 21.9 parts of 35% hydrochloric acid was added at 10 to 30°C, and the mixture was stirred at 10 to 30°C for 1 hour to perform diazotization. Subsequently, 10.0 parts of 2,5-dimethylaniline was added, and while stirring at 20 to 30°C, sodium carbonate was added to adjust the pH to 3.5, and the mixture was further stirred to complete the coupling reaction, and the precipitated target product was collected by filtration and dried to obtain 35.0 parts of a monoazoamino compound represented by the following formula (1001).

400 parts of water was added to 35.0 parts of the monoazoamino compound represented by the above formula (1001) and 33.3 parts of the disazoamino compound represented by the above formula (135), and the mixture was dissolved with sodium hydroxide. 9.7 parts of 4-nitrophenyl chloroformate was added and stirred at 60 to 80°C for 5 hours to form a ureido compound. Salting out was performed with sodium chloride, and the precipitated target product was collected by filtration and dried to obtain 5.1 parts of a ureido compound represented by formula (1002), which is an azo compound of the present invention. The maximum absorption wavelength of this compound in a 20% aqueous pyridine solution was 438 nm.

(Example p1: Synthesis of the azo compound of formula (p32))

30.6 parts of the aminobenzoylaminonaphthalene compound (132) was added to 400 parts of water and dissolved with sodium hydroxide, and 4.8 parts of sodium nitrite was added, and 21.9 parts of 35% hydrochloric acid was added at 10 to 30°C, and the mixture was stirred at 10 to 30°C for 1 hour to perform diazotization. Subsequently, 13.2 parts of 2-methoxy-5-methylaniline was added, and while stirring at 20 to 30°C, sodium carbonate was added to adjust the pH to 4.0, and the mixture was further stirred to complete the coupling reaction. The precipitated target product was filtered and dried to obtain 38.8 parts of a monoazoamino compound represented by the following formula (p102).

38.8 parts of the obtained monoazoamino compound (p102) was added to 300 parts of water and dissolved with sodium hydroxide, and 2.8 parts of sodium nitrite was added, and 11.7 parts of 35% hydrochloric acid was added at 10 to 30°C, and the mixture was stirred at 20 to 30°C for 1 hour to perform diazotization. Subsequently, 9.2 parts of 3-(2-amino-4-methylphenoxy)propane-1-sulfonic acid was added, and while stirring at 20 to 30°C, sodium carbonate was added to adjust the pH to 4.0, and the mixture was further stirred to complete the coupling reaction. The precipitated target product was filtered and dried to obtain 24.8 parts of a disazoamino compound represented by the following formula (p103).

24.8 parts of the resulting disazoamino compound (p103) was added to 400 parts of water and dissolved with sodium hydroxide. 9.7 parts of 4-nitrophenyl chloroformate was added and stirred at 60-80°C for 5 hours to form a ureido compound. Salting out with sodium chloride was performed, and the precipitated target product was collected by filtration and dried to obtain 5.1 parts of the ureido compound of the present invention represented by the above formula (p32). The maximum absorption wavelength of this compound in a 20% aqueous pyridine solution was 494 nm.

(Example p2: Synthesis of azo compound of formula (p6))

28.6 parts of disazoamino compound (131) and 24.8 parts of disazoamino compound (p103) obtained in Example p1 were added to 400 parts of water, dissolved with sodium hydroxide, and 9.9 parts of 4-nitrophenyl chloroformate was added. The mixture was stirred at 60-80°C for 5 hours to form a ureido compound. Salting out with sodium chloride was performed, and the precipitated target product was collected by filtration and dried to obtain 2.7 parts of the ureido compound represented by formula (p6) of the present invention. The maximum absorption wavelength of this compound in a 20% aqueous pyridine solution was 490 nm.

(Example p3: Synthesis of the azo compound of formula (p42))

26.7 parts of the monoazoamino compound (129) was added to 300 parts of water and dissolved with sodium hydroxide, and 2.8 parts of sodium nitrite was added, and 11.7 parts of 35% hydrochloric acid was added at 10 to 30° C., and the mixture was stirred at 20 to 30° C. for 1 hour to perform diazotization. Subsequently, 9.2 parts of 3-(2-amino-4-methylphenoxy)propane-1-sulfonic acid was added, and while stirring at 20 to 30° C., sodium carbonate was added to adjust the pH to 4.0, and the mixture was further stirred to complete the coupling reaction. The precipitated target product was filtered and dried to obtain 24.8 parts of a disazoamino compound represented by the following formula (p108).

24.8 parts of the resulting disazoamino compound (p108) was added to 400 parts of water and dissolved with sodium hydroxide. 9.7 parts of 4-nitrophenyl chloroformate was added and stirred at 60-80°C for 5 hours to form a ureido compound. Salting out with sodium chloride was performed, and the precipitated target product was collected by filtration and dried to obtain 5.1 parts of the ureido compound of the present invention represented by the above formula (p42). The maximum absorption wavelength of this compound in a 20% aqueous pyridine solution was 484 nm.

(Example p4: Synthesis of the azo compound of formula (p20))

22.4 parts of disazoamino compound (146) and 24.8 parts of disazoamino compound (p103) obtained in Example p1 were added to 400 parts of water, dissolved with sodium hydroxide, and 8.4 parts of 4-nitrophenyl chloroformate was added. The mixture was stirred at 60-80°C for 5 hours to form a ureido compound. Salting out with sodium chloride was performed, and the precipitated target product was collected by filtration and dried to obtain 2.2 parts of the ureido compound represented by formula (p20) of the present invention. The maximum absorption wavelength of this compound in a 20% aqueous pyridine solution was 480 nm.

(Example p5: Synthesis of the azo compound of the above formula (p27))

24.0 parts of disazoazoamino compound (140) were added to 400 parts of water and dissolved with sodium hydroxide. 8.4 parts of 4-nitrophenyl chloroformate were added and stirred at 60-80°C for 5 hours to form a ureido compound. Salting out with sodium chloride was performed, and the precipitated target product was collected by filtration and dried to obtain 4.2 parts of the ureido compound of the present invention represented by the above formula (p27). The maximum absorption wavelength of this compound in a 20% aqueous pyridine solution was 488 nm.

(Example p6: Synthesis of the azo compound of the above formula (p29))

25.1 parts of the monoazoamino compound (148) was added to 300 parts of water and dissolved with sodium hydroxide, and 2.8 parts of sodium nitrite was added, and 11.7 parts of 35% hydrochloric acid was added at 10 to 30° C., and the mixture was stirred at 20 to 30° C. for 1 hour to perform diazotization. Subsequently, 9.2 parts of 3-(2-amino-4-methylphenoxy)propane-1-sulfonic acid was added, and while stirring at 20 to 30° C., sodium carbonate was added to adjust the pH to 4.0, and the mixture was further stirred to complete the coupling reaction. The precipitated target product was filtered and dried to obtain 24.8 parts of a disazoamino compound represented by the following formula (p116).

24.8 parts of the resulting disazoazoamino compound (p116) was added to 400 parts of water, dissolved with sodium hydroxide, and 8.4 parts of 4-nitrophenyl chloroformate was added. The mixture was stirred at 60-80°C for 5 hours to form a ureido compound. Salting out with sodium chloride was performed, and the precipitated target product was collected by filtration and dried to obtain 3.2 parts of the ureido compound of the present invention represented by the above formula (p29). The maximum absorption wavelength of this compound in a 20% aqueous pyridine solution was 486 nm.

(Examples f1 to f10 and fp1 to fp6: Preparation of dye-based polarizing films)
A 75 μm-thick polyvinyl alcohol film was immersed for 4 minutes in a 45°C aqueous solution (dye bath) containing 0.03% of each of the azo compounds obtained in Examples 1 to 10 and p1 to p6 and 0.1% sodium sulfate. The film was then removed and stretched 5 times at 50°C in a 3% aqueous boric acid solution, washed with water while maintaining tension, and dried to obtain a dye-based polarizing film of the present invention. The maximum absorption wavelength and polarization ratio of the resulting dye-based polarizing film are shown in Table 1. As shown in Table 1, all of the polarizing films prepared using these compounds had high polarization ratios.

The maximum absorption wavelength of the polarizing film was measured and the polarization rate was calculated using the parallel transmittance and crossed transmittance when polarized light was incident, measured using a spectrophotometer (U-4100 manufactured by Hitachi, Ltd.).
Here, the parallel transmittance (Ky) is the transmittance measured by setting the absorption axis of an absolute polarizer (a polarizing plate with a polarization degree of 99.99%) parallel to the absorption axis of a polarizing film, and the orthogonal transmittance (Kz) is the transmittance measured by setting the absorption axis of the absolute polarizer perpendicular to the absorption axis of a polarizing film.
The parallel transmittance and crossed transmittance for each wavelength were measured at 1 nm intervals from 380 to 780 nm. Using the measured values, the polarization rate for each wavelength was calculated using the following formula (I), and the highest polarization rate in the range from 380 to 780 nm and the maximum absorption wavelength (nm) at that time were obtained.
Polarization rate (%) = [(Ky-Kz)/(Ky+Kz)] x 100 (I)

(Comparative Example 1: Preparation of polarizing film)
A comparative dye-based polarizing film was prepared in the same manner as in Example f1, except that CI Direct Orange 39 was used instead of the compound of formula (6).

(Comparative Example 2: Preparation of polarizing film)
A comparative dye-based polarizing film was prepared in the same manner as in Example f1, except that CI Direct Yellow 44 was used instead of the compound of formula (6).

One index of image quality is contrast, which indicates the difference in brightness between white and black displays. Table 2 shows the contrast at the maximum absorption wavelength of the dye-based polarizing films obtained in Examples f1 to f10 and fp1 to fp6 and Comparative Examples 1 and 2. Here, contrast refers to the ratio of parallel transmittance to crossed transmittance (contrast = parallel transmittance at the maximum absorption wavelength (Ky) / crossed transmittance at the maximum absorption wavelength (Kz)), and the higher this value, the better the polarization performance of the polarizing plate. For contrast measurement, samples were prepared so that the parallel transmittance at the maximum absorption wavelength of the dye-based polarizing film was the same, and evaluation was performed. As shown in Table 2, the dye-based polarizing films of Examples f1 to f10 and fp1 to fp6 all had higher contrast than the dye-based polarizing films of Comparative Examples 1 and 2.

(Example n1: Preparation of neutral gray polarizing plate)
A dye-based polarizing film of the present invention was prepared in the same manner as in Example f1, except that a 45°C aqueous solution containing 0.1% of the compound of formula (6) obtained in Example 1, 0.2% of CI Direct Red 81, 0.05% of CI Direct Blue 274, and 0.1% of sodium sulfate was used as the dye bath. The resulting polarizing film had a single-plate average transmittance of 42% at 380 to 700 nm, an average transmittance in the crossed direction of 0.02% or less, a high degree of polarization over a wide wavelength range, and a neutral gray hue. Triacetyl cellulose films (TAC film: Fujifilm Corporation, product name TD-80U) were laminated to both sides of the polarizing film using an adhesive made of an aqueous polyvinyl alcohol solution, and a support (NOF Corporation, Realook X4010) with an AR layer was attached using a pressure-sensitive adhesive to obtain a dye-based polarizing plate of the present invention, laminated in this order: TAC/polarizing film/TAC/AR support. The obtained dye-based polarizing plate exhibited a neutral gray hue similar to the state of the polarizing film, and had a high polarization rate.

(Example n2: Preparation of neutral gray polarizing plate)
A dye-based polarizing film of the present invention was prepared in the same manner as in Example f1, except that a 45°C aqueous solution containing 0.1% of the compound of formula (13) obtained in Example 2, 0.2% of CI Direct Red 81, 0.05% of CI Direct Blue 274, and 0.1% of sodium sulfate was used. The resulting polarizing film had a single-plate average transmittance of 42% at 380 to 700 nm, an average transmittance in the crossed direction of 0.02% or less, a high degree of polarization over a wide wavelength range, and a neutral gray hue. Triacetyl cellulose films (TAC film: Fujifilm Corporation, product name TD-80U) were laminated to both sides of the polarizing film using an adhesive made of an aqueous polyvinyl alcohol solution, and a support (NOF Corporation, Realook X4010) with an AR layer was attached using a pressure-sensitive adhesive to obtain a dye-based polarizing plate of the present invention, in which TAC/polarizing film/TAC/AR support were laminated in this order. The obtained dye-based polarizing plate exhibited a neutral gray hue, similar to the polarizing film, and had a high polarization rate.

(Example n3: Preparation of neutral gray polarizing plate)
A dye-based polarizing film of the present invention was prepared in the same manner as in Example f1, except that a 45°C aqueous solution containing 0.1% of the compound of formula (66) obtained in Example 7, 0.2% of CI Direct Red 81, 0.05% of CI Direct Blue 274, and 0.1% of sodium sulfate was used. The resulting polarizing film had a single-plate average transmittance of 42% in the 380-700 nm range and an average crossed transmittance of 0.02% or less, exhibiting a high degree of polarization over a wide wavelength range and a neutral gray hue. Triacetyl cellulose films (TAC film: Fujifilm Corporation, product name TD-80U) were laminated to both sides of the polarizing film using an aqueous polyvinyl alcohol adhesive, and a support (NOF Corporation, Realook X4010) with an AR layer was attached using a pressure-sensitive adhesive to obtain a dye-based polarizing plate of the present invention, laminated in this order: TAC/polarizing film/TAC/AR support. The obtained dye-based polarizing plate exhibited a neutral gray hue, similar to the polarizing film, and had a high polarization rate.

(Example n4: Preparation of neutral gray polarizing plate)
A dye-based polarizing film of the present invention was prepared in the same manner as in Example f1, except that a 45°C aqueous solution containing 0.1% of the compound of formula (1002) obtained in Example 10, 0.2% of CI Direct Red 81, 0.05% of CI Direct Blue 274, and 0.1% of sodium sulfate was used. The resulting polarizing film had a single-plate average transmittance of 42% at 380 to 700 nm, an average transmittance in the crossed direction of 0.02% or less, a high degree of polarization over a wide wavelength range, and a neutral gray hue. Triacetyl cellulose films (TAC film: Fujifilm Corporation: product name TD-80U) were laminated to both sides of the polarizing film using an adhesive made of an aqueous polyvinyl alcohol solution, and a support (NOF Corporation: Realook X4010) with an AR layer was attached using a pressure-sensitive adhesive to obtain a dye-based polarizing plate of the present invention, laminated in this order: TAC/polarizing film/TAC/AR support. The obtained dye-based polarizing plate exhibited a neutral gray hue, similar to the polarizing film, and had a high polarization rate.

(Example np1: Preparation of neutral gray polarizing plate)
A dye-based polarizing film of the present invention was prepared in the same manner as in Example f1, except that a 45°C aqueous solution containing 0.1% of the compound of formula (p32) obtained in Example p1, 0.2% of CI Direct Red 81, 0.05% of CI Direct Blue 274, and 0.1% of sodium sulfate was used as the dye bath. The resulting polarizing film had a single-plate average transmittance of 42% at 380 to 700 nm, an average transmittance in the crossed direction of 0.02% or less, a high degree of polarization over a wide wavelength range, and a neutral gray hue. Triacetyl cellulose films (TAC film: Fujifilm Corporation, product name TD-80U) were laminated to both sides of the polarizing film using an adhesive made of an aqueous polyvinyl alcohol solution, and a support (NOF Corporation, Realook X4010) with an AR layer was attached using a pressure-sensitive adhesive to obtain a dye-based polarizing plate of the present invention, laminated in this order: TAC/polarizing film/TAC/AR support. The obtained dye-based polarizing plate exhibited a neutral gray hue similar to the state of the polarizing film, and had a high polarization rate.

(Example np2: Preparation of neutral gray polarizing plate)
A dye-based polarizing film of the present invention was prepared in the same manner as in Example f1, except that a 45°C aqueous solution containing 0.1% of the compound of formula (p6) obtained in Example p2, 0.2% of CI Direct Red 81, 0.05% of CI Direct Blue 274, and 0.1% of sodium sulfate was used. The resulting polarizing film had a single-plate average transmittance of 42% at 380 to 700 nm, an average transmittance in the crossed direction of 0.02% or less, a high degree of polarization over a wide wavelength range, and a neutral gray hue. Triacetyl cellulose films (TAC film: Fujifilm Corporation, product name TD-80U) were laminated to both sides of the polarizing film using an adhesive made of an aqueous polyvinyl alcohol solution, and a support (NOF Corporation, Realook X4010) with an AR layer was attached using a pressure-sensitive adhesive to obtain a dye-based polarizing plate of the present invention, laminated in this order: TAC/polarizing film/TAC/AR support. The obtained dye-based polarizing plate exhibited a neutral gray hue, similar to the polarizing film, and had a high polarization rate.

(Example np3: Preparation of neutral gray polarizing plate)
A dye-based polarizing film of the present invention was prepared in the same manner as in Example f1, except that a 45°C aqueous solution containing 0.1% of the compound of formula (p20) obtained in Example p4, 0.2% of CI Direct Red 81, 0.05% of CI Direct Blue 274, and 0.1% of sodium sulfate was used. The resulting polarizing film had a single-plate average transmittance of 42% in the 380-700 nm range and an average crossed transmittance of 0.02% or less, exhibiting a high degree of polarization over a wide wavelength range and a neutral gray hue. Triacetyl cellulose films (TAC film: Fujifilm Corporation: product name TD-80U) were laminated to both sides of the polarizing film using an aqueous polyvinyl alcohol adhesive, and a support (NOF Corporation: Realook X4010) with an AR layer was attached using a pressure-sensitive adhesive to obtain a dye-based polarizing plate of the present invention, laminated in this order: TAC/polarizing film/TAC/AR support. The obtained dye-based polarizing plate exhibited a neutral gray hue, similar to the polarizing film, and had a high polarization rate.

(Moisture and heat resistance test)
The neutral gray polarizing plates obtained in Examples n1 to n4 and np1 to np3 were left for 400 hours under conditions of 80°C and 90% RH, and the change in single-plate average transmittance was measured. As a result, there was no change in single-plate average transmittance even after 400 hours, which indicates that the dye-based polarizing plates of the present invention exhibit durability (moist heat resistance) over long periods of time under high-temperature and high-humidity environments.

(Lightfastness test)
Next, the average single-plate light transmittance (%) was measured after irradiating the AR support side with ultraviolet light of 300 to 400 nm at an intensity of 100 W/ ^m² in a chamber temperature of 70°C using a Super Xenon Weather Meter SX75 manufactured by Suga Test Instruments Co., Ltd. As a result, the dye-based polarizing plate of the present invention showed no change in average single-plate transmittance even after 200 hours had passed in the xenon light resistance test, confirming that the plate also has excellent light resistance to long-term exposure to light.

From the above, it has been demonstrated that the dye-based polarizing plate of the present invention has excellent polarization performance and is a high-performance dye-based polarizing plate that is moisture-resistant, heat-resistant, and light-resistant.

Dye-based polarizing plates using the azo compound or its salt of the present invention can be used in in-vehicle displays, liquid crystal projectors, OLEDs, polarized lenses, polarized glasses, etc., which require high durability.

Claims (14)

An azo compound represented by the following formula (1) or a salt thereof , wherein in formula (1), A ₁ and A ₂ each independently represent a naphthyl group which may have a substituent, or a phenyl group which may have a substituent;
(In formula (1) , m, n, and p each independently represent 0 or 1, and either m or n represents 1; and R ₁ to R ₁₂ each independently represent a hydrogen atom or a substituent .)
The optionally substituted phenyl group is a phenyl group represented by the following formula (2):
(In formula (2), one of R ₁₃ and R ₁₄ represents a sulfo group, a carboxy group, or a C1-4 alkoxy group having a sulfo group, and the other represents a hydrogen atom, a sulfo group, a carboxy group, a C1-4 alkoxy group having a sulfo group, a C1-4 alkyl group, a C1-4 alkoxy group, a halogen atom, a nitro group, an amino group, a C1-4 alkyl-substituted amino group, or a C1-4 alkyl-substituted acylamino group, and * represents the bonding position with the terminal amide group or azo group in formula (1))
An azo compound or a salt thereof, wherein the naphthyl group which may have a substituent is a naphthyl group represented by the following formula (3):
(In formula (3), R ₁₅ represents a hydrogen atom, a C1-4 alkoxy group having a sulfo group, a hydroxy group, or a sulfo group, q represents an integer of 1 to 3, and * represents the bonding position with the terminal amide group or azo group in formula (1)). 2. The azo compound or salt thereof according to claim 1 , wherein in the formula (1), A ₁ and A ₂ are each independently a naphthyl group represented by the formula (3) . 3. The azo compound or salt thereof according to claim 1 _{or 2} , wherein in the formula (1), R ₁ , R ₂ , R ₁₁ and R ₁₂ each independently represent a hydrogen atom, a C1-4 alkyl group or a C1-4 alkoxy group, and R 3 to R 10 each independently represent a hydrogen atom, a C1-4 alkoxy group having a sulfo group, a C1-4 alkoxy group or a C1-4 alkyl group. 4. The azo compound or salt thereof according to claim 1 , wherein in formula (2), one of R ₁₃ and R ₁₄ is a sulfo group or a carboxy group, and the other is a hydrogen atom, a sulfo group, a carboxy group, a chloro group, a methyl group, or a methoxy group. 5. The azo compound or salt thereof according to claim 1 , wherein in formula (1), R ₃ to R ₁₀ are each independently a group selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, a methoxy group, and a 3-sulfopropoxy group. The azo compound or salt thereof according to any one of claims 1 to 5 , wherein the formula (1) is represented by the following formula (4):
(wherein A ₁ , A ₂ , R ₁ to R ₁₂ , m, n, and p are the same as in formula (1) above). 7. The azo compound or a salt thereof according to claim 1 , wherein p is 0. 7. The azo compound or a salt thereof according to claim 1 , wherein p is 1. A dye-based polarizing film comprising the azo compound or salt thereof according to any one of claims 1 to 8 and a substrate. 10. The dye-based polarizing film according to claim 9 , further comprising one or more organic dyes having a structure other than the azo compound or the salt thereof. 11. The dye-based polarizing film according to claim 9 , wherein the substrate is a film containing a polyvinyl alcohol resin or a derivative thereof. The dye-based polarizing film according to any one of claims 9 to 11 , which exhibits a neutral gray color. A dye-based polarizing plate comprising the dye-based polarizing film according to any one of claims 9 to 12 and a transparent protective film attached to one or both sides of the dye-based polarizing film. A display device comprising the dye-based polarizing film according to any one of claims 9 to 12 or the dye-based polarizing plate according to claim 13 .