阅读说明：本技术 偏光元件及使用该偏光元件的偏光板以及光学构件等 (Polarizing element, and polarizing plate and optical member using the same ) 是由 望月典明 服部由侑 中村光则 樋下田贵大 于 2019-09-04 设计创作，主要内容包括：本发明的偏光元件,包含：以式(1)所示的偶氮化合物或其盐、以式(2)所示的偶氮化合物或其盐、及基材；(式(1)中,Ar-1表示具有取代基的苯基或具有取代基的萘基,Rr-1至Rr-4分别独立地表示氢原子、C1至4烷基、C1至4烷氧基或具有磺基的C1至4烷氧基,Xr-1表示可具有取代基的胺基、可具有取代基的苯基胺基、可具有取代基的苯基偶氮基、可具有取代基的苯甲酰基、可具有取代基的苯甲酰基胺基或可具有取代基的萘并三唑基,m表示0或1)；(式(2)中,Ab-1表示具有取代基的苯基或具有取代基的萘基,Rb-1至Rb-5分别独立地表示氢原子、C1至4烷基、C1至4烷氧基或具有磺基的C1至4的烷氧基,Xb-1表示可具有取代基的胺基、可具有取代基的苯基胺基、可具有取代基的苯基偶氮基、可具有取代基的苯甲酰基、可具有取代基的苯甲酰基胺基或可具有取代基的萘并三唑基)。(The polarizing element of the present invention comprises: an azo compound represented by the formula (1) or a salt thereof, an azo compound represented by the formula (2) or a salt thereof, and a base material; (in the formula (1), Ar 1 Represents a substituted phenyl group or a substituted naphthyl group, Rr 1 To Rr 4 Each independently represents a hydrogen atom, a C1 to 4 alkyl group, a C1 to 4 alkoxy group or a C1 to 4 alkoxy group having a sulfo group, Xr 1 Represents an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a benzoyl group which may have a substituent, a benzoylamino group which may have a substituent or a naphthotriazole group which may have a substituent, and m represents 0 or 1); (in the formula (2, Ab) 1 Represents a substituted phenyl group or a substituted naphthyl group, Rb 1 To Rb 5 Each independently represents a hydrogen atom, a C1 to 4 alkyl group, a C1 to 4 alkoxy group or a C1 to 4 alkoxy group having a sulfo group, Xb 1 Represents an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a benzoyl group which may have a substituent, a benzoylamino group which may have a substituent or a naphthotriazole group which may have a substituent).)

1. A polarizing element comprising:

an azo compound represented by the formula (1) or a salt thereof, an azo compound represented by the formula (2) or a salt thereof, and a base material;

in the formula (1), Ar₁Represents a substituted phenyl group or a substituted naphthyl group, Rr₁To Rr₄Each independently represents a hydrogen atom, a C1 to 4 alkyl group, a C1 to 4 alkoxy group or a C1 to 4 alkoxy group having a sulfo group, Xr₁Represents an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a benzoyl group which may have a substituent, a benzoylamino group which may have a substituent or a naphthotriazole group which may have a substituent, and m represents 0 or 1;

in the formula (2), Ab₁Represents a substituted phenyl group or a substituted naphthyl group, Rb₁To Rb₅Each independently represents a hydrogen atom, a C1 to 4 alkyl group, a C1 to 4 alkoxy group or a C1 to 4 alkoxy group having a sulfo group, Xb₁Represents an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a benzoyl group which may have a substituent, a benzoylamino group which may have a substituent or a naphthotriazole group which may have a substituent.

2. The polarizing element according to claim 1, wherein the azo compound represented by formula (2) is an azo compound represented by formula (3),

in formula (3), Ab₁、Rb₁To Rb₅And Xb₁The same as described in the above formula (2).

3. The polarizing element according to claim 1 or 2, wherein Rb₅Is methoxy.

4. The polarizing element according to any one of claims 1 to 3, further comprising an azo compound represented by formula (4),

in the formula (4), Ay₁Represents sulfo, carboxyl, hydroxyl, C1 to 4 alkyl or C1 to 4 alkoxy, Ry₁To Ry₄Each independently represents a hydrogen atom, a C1 to 4 alkyl group or a C1 to 4 alkoxy group, and p represents 1,2, or 3.

5. The polarizing element according to any one of claims 1 to 4, wherein the substrate is a film containing a polyvinyl alcohol resin.

6. A polarizing plate includes: the polarizing element according to any one of claims 1 to 5, and a transparent protective layer provided on one or both surfaces of the polarizing element.

7. An optical member, machine or device, comprising the polarizing element according to any one of claims 1 to 5 or the polarizing plate according to claim 6.

Technical Field

The present invention relates to a dye-based polarizing element, and a polarizing plate and an optical member using the same.

Background

The polarizing element is generally manufactured by adsorbing and orienting iodine as a dichroic dye or a dichroic dye onto a base film such as a polyvinyl alcohol resin. A protective film made of triacetyl cellulose or the like is bonded to at least one surface of the polarizer via an adhesive layer to produce a polarizing plate. The polarizing plate can be used for liquid crystal display devices and the like. A polarizing plate using iodine as a dichroic dye is called an iodine-based polarizing plate, and a polarizing plate using a dichroic dye as a dichroic dye is called a dye-based polarizing plate. Among these, the dye-based polarizing plate is characterized by high heat resistance, high humidity and heat durability, high stability, and high color selectivity for blending a dichroic dye.

In addition, dye-based polarizing elements containing azo compounds have been disclosed in patent documents 1 to 4 and non-patent documents 1 and 2.

[ Prior art documents ]

[ patent document ]

[ patent document 1] Japanese patent application laid-open No. 11-218611

[ patent document 2] Japanese patent application laid-open No. 2001-033627

[ patent document 3] Japanese patent application laid-open No. 2004-251962

[ patent document 4] Japanese patent laid-open publication No. 2004-075719

[ patent document 5] Japanese patent application laid-open No. H08-291259

[ patent document 6] Japanese patent application laid-open No. 2002-275381.

[ non-patent document ]

[ non-patent document 1] FINIANFENG, "DYE CHEMICAL", Tech-Proch-Touch-Press limited, 1957, page 621-

[ non-patent document 2] was examined and maintained in the Yangtze Dynasty, "application of functional pigment" (issue 1, brush), published by CMC GmbH, 6 months 2002, P.98-104.

Disclosure of Invention

[ problems to be solved by the invention ]

The present invention aims to provide a polarizing element, a polarizing plate, an optical member, and the like (hereinafter also referred to as "polarizing element and the like") having optical characteristics (polarizing performance, contrast, and the like) equivalent to or more excellent than those of the known polarizing element.

[ means for solving the problems ]

The present inventors have made extensive studies to solve the above problems, and as a result, have found that the optical characteristics of a polarizing element can be improved by combining 2 types of azo compounds having specific structures, and have finally completed the present invention.

That is, the present invention relates to inventions 1 to 7 below, but is not limited to these.

[ invention 1]

The polarizing element of the present invention comprises:

an azo compound represented by the formula (1) or a salt thereof, an azo compound represented by the formula (2) or a salt thereof, and a base material;

(in the formula (1), Ar₁Represents a substituted phenyl group or a substituted naphthyl group, Rr₁To Rr₄Each independently represents a hydrogen atom, a C1 to 4 alkyl group, a C1 to 4 alkoxy group or a C1 to 4 alkoxy group having a sulfo group, Xr₁Represents an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a benzoyl group which may have a substituent, a benzoylamino group which may have a substituent or a naphthotriazole group which may have a substituent, and m represents 0 or 1);

(in the formula (2, Ab)₁Represents a substituted phenyl group or a substituted naphthyl group, Rb₁To Rb₅Each independently represents a hydrogen atom, a C1 to 4 alkyl group, a C1 to 4 alkoxy group or a C1 to 4 alkoxy group having a sulfo group, Xb₁Represents an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a benzoyl group which may have a substituent, a benzoylamino group which may have a substituent or a naphthotriazole group which may have a substituent).

[ invention 2]

The polarizing element according to invention 1, wherein the azo compound represented by formula (2) is an azo compound represented by formula (3).

(in the formula (3, Ab)₁、Rb₁To Rb₅And Xb₁And the above formula (2) areThe same).

[ invention 3]

The polarizing element according to claim 1 or 2, wherein Rb₅Is methoxy.

[ invention 4]

The polarizing element according to any one of inventions 1 to 3, further comprising an azo compound represented by formula (4),

(in the formula (4), Ay₁Represents sulfo, carboxyl, hydroxyl, C1 to 4 alkyl or C1 to 4 alkoxy, Ry₁To Ry₄Each independently represents a hydrogen atom, a C1 to 4 alkyl group or a C1 to 4 alkoxy group, and p represents 1,2 or 3).

[ invention 5]

The polarizing element according to any one of claims 1 to 4, wherein the substrate is a film containing a polyvinyl alcohol resin.

[ invention 6]

A polarizing plate includes: the polarizing element according to any one of inventions 1 to 5, and a transparent protective layer provided on one surface or both surfaces of the polarizing element.

[ invention 7]

An optical member, a device or an apparatus, comprising the polarizing element according to any one of claims 1 to 5 or the polarizing plate according to claim 6.

[ Effect of the invention ]

According to the present invention, a polarizing element and the like having excellent optical characteristics can be provided. In one embodiment, the polarizing element of the present invention has excellent durability (moisture resistance, heat resistance, etc.). In one embodiment, the polarizing element of the present invention has preferable polarizing performance and contrast, and can meet the recent demand for high-definition displays. In one embodiment, the polarizing element or the like of the present invention has a high transmittance and a small change in polarization degree under a high-temperature and/or high-humidity environment, which are desired in recent years for a touch panel, an organic EL display, or the like.

Detailed Description

In the specification of the present application, a free body containing an azo compound, a salt of an azo compound, a mixture of a free body (free acid or free base) and a salt, and the like are sometimes described as an "azo compound". In addition, in the specification of the present application, a "substituent" includes a hydrogen atom as an expedient.

< polarizing element >

The polarizing element of the present invention comprises: a base material, an azo compound represented by the above formula (1), and an azo compound represented by the above formula (2). When the azo compound represented by the above formula (1) is the azo compound represented by the above formula (3), a polarizing element having a higher degree of polarization can be realized. The polarizing element of the present invention preferably further contains an azo compound represented by the above formula (4) in addition to the azo compounds represented by the above formulae (1) and (2). Accordingly, a polarizing element having a higher degree of polarization can be realized. That is, it is particularly preferable that the base material contains azo compounds represented by the above formulae (1), (2) and (4). When the azo compound used in the present invention has a functional group such as a hydroxyl group, a carboxyl group, or a sulfo group, the azo compound may be used as a free acid, a salt, or a mixture of a free acid and a salt.

Examples of the salt of the azo compound include alkali metal salts such as lithium salt, sodium salt, and potassium salt; alkaline earth metal salts such as calcium salts; an ammonium salt; organic salts such as alkylamine salts and alkanolamine salts are preferably lithium salts, sodium salts, potassium salts, or ammonium salts, more preferably lithium salts or sodium salts, and still more preferably sodium salts.

The azo compound can be generally synthesized in the art by performing a known diazotization and coupling reaction according to a known synthesis method of an azo compound (for example, page 626 of non-patent document 1). The polarizing element can be produced by dissolving an azo compound in a solution and impregnating the substrate with the solution in a dyeing step.

The azo compound represented by the above formula (1) will be described.

In the above formula (1), Ar₁Represents a substituted phenyl group or a substituted naphthyl group.

Ar₁In the case of a phenyl group having a substituent, at least 1 of the amino groups substituted with a sulfo group, a carboxyl group, a C1 to 4 alkyl group, a C1 to 4 alkoxy group, a C1 to 4 alkoxy group having a sulfo group, a nitro group, a benzoyl group, an amino group, an acetylamino group and a C1 to 4 alkylamino group is more preferable, and at least 1 of the amino groups having a sulfo group or a carboxyl group is more preferable. The phenyl group has 2 substituents, at least 1 of the substituents is sulfo or carboxyl, the other substituents are preferably sulfo, carboxyl, C1 to 4 alkyl, C1 to 4 alkoxy, C1 to 4 alkoxy having sulfo, nitro, benzoyl, amino, acetylamino and C1 to 4 alkylamino substituted amino, more preferably sulfo, methyl, ethyl, methoxy, epoxy, carboxyl, nitro, benzoyl and amino, particularly preferably sulfo, methyl, methoxy, epoxy, benzoyl and carboxyl. The C1 to 4 alkoxy group having a sulfo group is preferably a linear alkoxy group, and the substitution position of the sulfo group is preferably an alkoxy terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably a 3-sulfopropoxy group. The number of sulfo groups of the substituted phenyl group is preferably 1 or 2, and the substitution position is not particularly limited, but when the bonding position to the CONH site in formula (1) is the 1-position, only the 4-position, the combination of the 2-position and the 4-position, and the combination of the 3-position and the 5-position are more preferred.

In the above formula (1), Ar₁In the case of a substituted naphthyl group, the naphthyl group may be bonded to the CONH site at the 1-position or may be bonded at the 2-position. More preferably, the naphthyl group is bonded at its 2-position to the CONH site. The naphthyl group is more preferably substituted by at least 1 having a sulfo group, a hydroxyl group, a carboxyl group, and a C1 to 4 alkoxy group having a sulfo group, and is more preferably substituted by at least 1 sulfo group or carboxyl group. When 2 or more substituents are present, it is more preferable that at least 1 of the substituents is a sulfo group, and the other substituents are selected from the group consisting of a sulfo group, a hydroxyl group, a carboxyl group, and a C1 to 4 alkoxy group having a sulfo group. The C1 to 4 alkoxy group having a sulfo group is more preferably a linear alkoxy group, and the substitution position of the sulfo group is more preferably an alkoxy terminal, and is more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably a 3-sulfopropoxy group. The above-mentioned substituted naphthyl groupWhen the number of sulfo groups as substituents is 2, the combination of the 4-and 8-positions and the combination of the 6-and 8-positions is more preferable, when the position of the sulfo group on the naphthyl group and the bonding position of the CONH site are 2-positions. When the number of sulfo groups contained in the naphthyl group is 3, and the bonding position to the CONH site in formula (1) is the 2-position, a combination of the 3-, 6-and 8-positions is particularly preferable as the substitution position of the sulfo group.

In the above formula (1), Rr₁To Rr₄Each independently represents a hydrogen atom, a C1 to 4 alkyl group, a C1 to 4 alkoxy group, or a C1 to 4 alkoxy group having a sulfo group. Rr₁To Rr₄More preferably, each independently is a hydrogen atom, a C1 to 4 alkyl group, or a C1 to 4 alkoxy group, and still more preferably a hydrogen atom, a methyl group, or a methoxy group. The C1 to 4 alkoxy group having a sulfo group is preferably a linear alkoxy group, and the substitution position of the sulfo group is preferably an alkoxy terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably a 3-sulfopropoxy group.

In the formula (1), m represents 0 or 1. When M is 0, it is easy to produce a polarizing plate having less wavelength dependence, that is, a polarizing element or a polarizing plate having neutral gray color, and when M is 1, it exhibits high degree of polarization, and therefore, each of them is a more preferable form.

In the above formula (1), Xr₁Represents an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a benzoyl group which may have a substituent, a benzoylamino group which may have a substituent or a naphthotriazole group which may have a substituent, with a phenylamino group which may have a substituent being more preferred.

Xr₁When the naphthotriazole group is a naphthotriazole group which may have a substituent, the naphthotriazole is 1, 2-naphthotriazole or 2, 3-naphthotriazole, and 2, 3-naphthotriazole is more preferable. Xr (x of X)₁The bonding position with the naphthyl group is not particularly limited, but the 2-position (central nitrogen atom) of the triazole ring portion is more preferable.

The above-mentioned amino group which may have a substituent(s) is more preferably one which may have a substituent(s) selected from the group consisting of a hydrogen atom, a hydroxyl group, a carboxyl group, a C1 to 4 alkyl group which may have a sulfo group, and a C1 to 4 alkoxy group which may have a sulfo groupThe amino group having 1 or 2 substituents is more preferably an amino group which may have 1 or 2 substituents selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, a methoxy group and an epoxy group. The above-mentioned phenylamino group which may have a substituent(s) is (are) preferably a phenylamino group which may have 1 or 2 substituents selected from the group consisting of a hydrogen atom, a C1 to 4 alkyl group, a C1 to 4 alkoxy group, a sulfo group, an amino group, a hydroxyl group and a C1 to 4 alkylamino group, and is more preferably a phenylamino group which may have 1 or 2 substituents selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfo group and an amino group. The phenylazo group which may have a substituent is preferably a phenylazo group having 1 to 3 kinds selected from the group consisting of a hydrogen atom, a hydroxyl group, a C1 to 4 alkyl group, a C1 to 4 alkoxy group, an amino group and a carboxyethylamino group. The optionally substituted benzoyl group is preferably a benzoyl group having 1 or more species selected from the group consisting of a hydrogen atom, a hydroxyl group, a sulfo group, an amino group and a carboxyethylamino group. The optionally substituted benzoylamino group is preferably 1 type of benzoylamino group selected from the group consisting of a hydrogen atom, a hydroxyl group, an amino group, and a carboxyethylamino group. The naphthotriazolyl group which may have a substituent is more preferably a naphthotriazolyl group having 1 to 3 kinds selected from the group consisting of a hydrogen atom, a hydroxyl group, a carboxyl group, a C1 to 4 alkyl group, a C1 to 4 alkoxy group, a sulfo group, an amino group, and a carboxyethylamino group, and is more preferably a naphthotriazolyl group having 1 to 3 sulfo groups. Xr (x of X)₁More preferred is a benzoylamino group which may have a substituent or a phenylamino group which may have a substituent, and still more preferred is a phenylamino group which may have a substituent. The position of the substituent in the phenylamino group which may have a substituent, the phenylazo group which may have a substituent, the benzoyl group which may have a substituent, or the benzoylamino group which may have a substituent is not particularly limited, but when the number of the substituents is 1, it is particularly preferable to substitute the p-position for the bonding position of the amino group, azo group, carbonyl group, or amide group bonded to the naphthalene ring in the formula (1). The substitution position in the naphthotriazole group which may have a substituent is not particularly limited, but when the number of the substituent is 1, the 4-position or 6-position of the naphthalene ring part in the case where the ring-contracting position with the triazole ring is numbered as "1-position and 2-position" or "2-position and 3-position" is preferableWhen the number of the substituents is 2, a combination of the 5-position and the 7-position or a combination of the 6-position and the 8-position is more preferable (see the following figure).

Examples of the method for obtaining the azo compound represented by the above formula (1) include, but are not limited to, the methods described in patent document 5 and patent document 6.

Further specific examples of the azo compound represented by the above formula (1) are shown below.

The azo compound represented by the above formula (2) will be described.

In the above formula (2), Ab₁Represents a substituted phenyl group or a substituted naphthyl group.

Ab₁In the case of a substituted phenyl group, the phenyl group preferably has at least 1 of a sulfo group, a carboxyl group, a C1 to 4 alkyl group, a C1 to 4 alkoxy group, a C1 to 4 alkoxy group having a sulfo group, a nitro group, a benzoyl group, an amino group, an acetylamino group and a C1 to 4 alkylamino substituted amino group as a substituent, and more preferably has at least 1 sulfo group or a carboxyl group. When the phenyl group has 2 or more substituents, at least 1 of these substituents is a sulfo group or a carboxyl group, and the other substituents are sulfo groups, carboxyl groups, C1 to 4 alkyl groupsC1 to 4 alkoxy, C1 to 4 alkoxy having a sulfo group, nitro, hydroxyl, amino or substituted amino (especially acetylamino or C1 to 4 alkylamino) are more preferable, sulfo, carboxyl, methyl, ethyl, methoxy, epoxy, nitro, hydroxyl or amino are more preferable, sulfo, carboxyl, methyl, ethyl, methoxy, epoxy, nitro or amino are still more preferable, sulfo, carboxyl, methyl, methoxy or epoxy are particularly preferable. In addition, other substituents are preferably sulfo, C1 to 4 alkyl or C1 to 4 alkoxy. Further, the C1 to 4 alkoxy group having a sulfo group is more preferably a linear alkoxy group, and the substitution position of the sulfo group is more preferably an alkoxy group terminal. The C1 to 4 alkoxy group having a sulfo group is more preferably a 3-sulfopropoxy group or a 4-sulfobutoxy group, and particularly preferably a 3-sulfopropoxy group. The number of substituents on the substituted phenyl group is preferably 1 or 2, more preferably 2. The position of the substituent on the phenyl group is not particularly limited, but the position is only 4, or a combination of 2 and 4, or a combination of 3 and 5, and particularly a combination of 2 and 4, with respect to the azo bond position in the formula (2).

In the above formula (2), Ab₁In the case of a substituted naphthyl group, it is more preferable that the naphthyl group has at least 1 sulfo group as a substituent, and in the case of a substituted naphthyl group having 2 or more, at least 1 of these substituents is a sulfo group, and the other substituents are preferably sulfo groups, hydroxyl groups, carboxyl groups or C1 to 4 alkoxy groups having sulfo groups. Further, the C1 to 4 alkoxy group having a sulfo group is more preferably a linear alkoxy group, and the substitution position of the sulfo group is more preferably an alkoxy group terminal. The above-mentioned C1 to 4 alkoxy group having a sulfo group is more preferably a 3-sulfopropoxy group or a 4-sulfobutoxy group, particularly preferably a 3-sulfopropoxy group. When the number of substitution of the sulfo group in the substituted naphthyl group is 2, and the substitution position of the sulfo group is such that the azo bond position in the formula (2) is the 2-position, a combination of the 4-position and the 8-position or a combination of the 6-position and the 8-position is more preferable, and a combination of the 6-position and the 8-position is particularly preferable. When the number of sulfo groups on the naphthyl group is 3, the substitution position of the sulfo group is particularly preferably a combination of the 1-position and the 3-and 6-positions.

In the above formula (2), Xb₁Can representThe amino group which may have a substituent, the phenylamino group which may have a substituent, the phenylazo group which may have a substituent, the benzoyl group which may have a substituent, the benzoylamino group which may have a substituent or the naphthotriazole group which may have a substituent, the benzoylamino group which may have a substituent, the phenylamino group which may have a substituent, the phenylazo group which may have a substituent or the naphthotriazole group which may have a substituent are more preferable, the benzoylamino group which may have a substituent, the phenylamino group which may have a substituent or the phenylazo group which may have a substituent is more preferable, and the phenylamino group which may have a substituent is particularly preferable.

The above-mentioned amine group preferably has 1 to 2 substituents. The substituent is preferably a hydrogen atom, a methyl group, a methoxy group, a sulfo group, an amino group, or a C1 to 4 alkylamino group.

The above-mentioned phenylamino group preferably has 1 to 2 substituents. The substituent is preferably a hydrogen atom, a C1 to 4 alkyl group, a C1 to 4 alkoxy group, a hydroxyl group, a carboxyl group, a sulfo group, an amino group, or a substituted amino group, more preferably a hydrogen atom, a methyl group, a methoxy group, a sulfo group, an amino group, or a substituted amino group, still more preferably a hydrogen atom, a methyl group, a methoxy group, a sulfo group, an amino group, or a C1 to 4 alkylamino group, particularly preferably a hydrogen atom, a methoxy group, or an amino group.

The phenylazo group preferably has 1 to 3 substituents. The substituent is preferably a hydrogen atom, a C1 to 4 alkyl group, a C1 to 4 alkoxy group, a hydroxyl group, a carboxyl group, a sulfo group, an amino group, or a substituted amino group, more preferably a hydrogen atom, a hydroxyl group, a carboxyl group, a C1 to 4 alkyl group, a C1 to 4 alkoxy group, an amino group, or a carboxyethylamino group, still more preferably a hydrogen atom, a hydroxyl group, an amino group, a methyl group, a methoxy group, or a carboxyl group, and particularly preferably a hydroxyl group.

The benzoyl group preferably has 1 substituent. The substituent is preferably a hydrogen atom, a C1 to 4 alkyl group, a C1 to 4 alkoxy group, a hydroxyl group, a carboxyl group, a sulfo group, an amino group, or a substituted amino group, more preferably a hydrogen atom, an amino group, a substituted amino group, or a hydroxyl group, still more preferably a hydrogen atom, an amino group, or a carboxyethylamino group, and particularly preferably an amino group.

The benzoylamino group preferably has 1 substituent. The substituent is preferably a hydrogen atom, a C1 to 4 alkyl group, a C1 to 4 alkoxy group, a hydroxyl group, a carboxyl group, a sulfo group, an amino group, or a substituted amino group, more preferably a hydrogen atom, an amino group, a substituted amino group, or a hydroxyl group, still more preferably a hydrogen atom, an amino group, or a carboxyethylamino group, and particularly preferably an amino group.

Xb₁When the naphthotriazole group is a naphthotriazole group which may have a substituent, the naphthotriazole is 1, 2-naphthotriazole or 2, 3-naphthotriazole, and 2, 3-naphthotriazole is more preferable. Xb₁The bonding position with the naphthyl group is not particularly limited, but the 2-position (central nitrogen atom) of the triazole ring portion is more preferable. The naphthotriazolyl group is more preferably substituted with 1 to 3 substituents, and still more preferably substituted with 2 substituents. The substituent is preferably a hydrogen atom, a hydroxyl group, a carboxyl group, a C1 to 4 alkyl group, a C1 to 4 alkoxy group, a sulfo group, an amine group, or a carboxyethylamino group, and more preferably a sulfo group.

Xb as described above₁The substituent is a phenylamino group having a substituent, a phenylazo group having a substituent, a benzoyl group having a substituent, or a benzoylamino group having a substituent, and when the substituent is 1, the position of the substituent is not particularly limited, but the p-position is more preferable for the amino group, azo group, carbonyl group, or amide group of the phenylamino group, phenylazo group, benzoyl group, or benzoylamino group. Xb as described above₁In the case of a naphthotriazolyl group having a substituent, the substitution position is not particularly limited, but in the case of 1 substituent, the 4-position or 6-position of the naphthalene ring portion in the case where the condensed ring position number with the triazole ring is "1-and 2-positions" or "2-and 3-positions" is more preferable, and in the case of 2 substituents, the combination of 5-and 7-positions or the combination of 6-and 8-positions is more preferable.

In the above formula (2), Rb₁To Rb₅Each independently represents a hydrogen atom, a C1 to 4 alkyl group, a C1 to 4 alkoxy group, or a C1 to 4 alkoxy group having a sulfo group, with a hydrogen atom, a C1 to 4 alkyl group, or a C1 to 4 alkoxy group being more preferred, and a hydrogen atom, a methyl group, or a methoxy group being more preferred. The C1 to 4 alkoxy group having a sulfo group is preferably a linear alkoxy group, and the substitution position of the sulfo group is terminated by an alkoxy groupIs more preferred. Preferable examples of the C1 to 4 alkoxy group having a sulfo group include a 3-sulfopropoxy group and a 4-sulfobutoxy group, and a 3-sulfopropoxy group is particularly preferable. In addition, Rb₅The methoxy group is particularly preferable because the polarizing performance of the polarizing element is particularly improved.

When the azo compound represented by the formula (2) is the azo compound represented by the formula (3), the polarizing performance of the polarizing element is further improved. In the above formula (3), Ab₁、Rb₁To Rb₅And Xb₁The same as described in the above formula (2).

In order to further improve the optical characteristics of the polarizing element, the azo compound represented by the following formula (5) is more preferably used in the formula (2).

In the above formula (5), Ab₁、Rb₂、Rb₄And Xb₁Are the same as those described for the above formula (2).

In the above formula (5), Rb₂And Rb₄Each independently represents a hydrogen atom, a C1 to 4 alkyl group, a C1 to 4 alkoxy group, or a C1 to 4 alkoxy group having a sulfo group, but a hydrogen atom, a methyl group, or a methoxy group is more preferable, and a hydrogen atom or a methyl group is more preferable. The azo compound represented by the above formula (2) is preferably one having a structure represented by the above formula (5) because the polarization characteristics can be particularly improved.

The azo compounds represented by the above formulae (2), (3) and (5) can be synthesized, for example, by the synthesis method described in non-patent document 1, or by diazotization and coupling described in international publication nos. 2012/108169 and 2012/108173. The method for synthesizing the azo compound represented by the above formula (2), formula (3) or formula (5) is not limited to the method described in the above document. The azo compounds represented by the above formulae (2), (3) and (5) may be converted into copper complex salt chloride compounds by treatment with copper sulfate or the like.

Specific examples of the azo compound represented by the above formula (2) are as follows. In addition, the following compounds represent sulfo and hydroxy as free acids, but may be in the form of salts.

In the above polarizing element, the content of the azo compound represented by the above formula (2) is more preferably in the range of 10 to 5000 parts by weight, and still more preferably in the range of 20 to 3000 parts by weight, relative to 100 parts by weight of the azo compound represented by the above formula (1).

The polarizing element may further include the formula (4).

Examples of the method for synthesizing the azo compound represented by the above formula (4) include, but are not limited to, the method described in non-patent document 1 and the method described in international publication No. 2007/138980.

Examples of the azo compound represented by the above formula (4) include, but are not limited to, azo compounds described in C.I.direct yellow 12, C.I.direct yellow 72, C.I.direct orange 39(CAS No.: 1325-54-8), and International publication No. 2007/138980.

Specific examples of the azo compound represented by the above formula (4) are as follows. In addition, the following examples of compounds represent sulfo and carboxyl groups as free acids, but sulfo or carboxyl groups may be in the form of salts.

In the above polarizing element, the content of the azo compound represented by the above formula (4) is more preferably in the range of 1 to 1000 parts by weight, and still more preferably in the range of 5 to 800 parts by weight, relative to 100 parts by weight of the azo compound represented by the above formula (1).

In the above polarizing element, in accordance with color adjustment or the like, other organic dyes (in particular, azo compounds) than the azo compounds represented by the above formulae (1), (2) and (4), for example, 1 or more kinds of azo compounds described in non-patent document 2, such as azo compounds, may be used in combination with the azo compounds represented by the above formulae (1) and (2), or in combination with the azo compounds represented by the above formulae (1), (2) and (4). The other organic dye to be used in combination is not particularly limited, but is a dye capable of dyeing a hydrophilic polymer, and is preferably a dye having light absorption in a wavelength region different from the absorption wavelength region of the azo compound, which is represented by the formula (1) and the formula (2), respectively, and having high dichroism. Specific examples of the other organic dyes include azo compounds described in non-patent document 2 (e.g., c.i. direct yellow 28), and azo compounds such as c.i. direct red 2, c.i. direct red 31, c.i. direct red 79, c.i. direct red 247, c.i. direct green 80, c.i. direct green 59, c.i. direct blue 202, and c.i. direct violet 9. These azo compounds can be used in the form of a free acid, or in the form of a salt of an alkali metal salt (e.g., sodium salt, potassium salt, lithium salt), ammonium salt, amine salt, or the like. When other organic dyes are optionally used in combination, the types of the other organic dyes to be blended can be changed depending on whether the target polarizing element is a polarizing element having a more neutral color, a polarizing element having a characteristic color, a color polarizing element for a liquid crystal projector, or another color polarizing element. The amount of the other organic dye to be blended (in the case of two or more types, the total amount of these blended) is not particularly limited, but is generally preferably in the range of 0.1 to 1000 parts by weight based on 100 parts by weight of the total amount of the azo compound represented by each of the above formulae (1), (2) and (4).

The substrate is preferably a hydrophilic polymer. The hydrophilic polymer is not particularly limited, but examples thereof include polyvinyl alcohol or a derivative thereof, amylose-based resins, starch-based resins, cellulose-based resins, and polyacrylate-based resins, and the substrate containing the azo compound is most preferably polyvinyl alcohol or a derivative thereof (hereinafter referred to as "polyvinyl alcohol-based resin") because of its dyeing properties, resin crosslinking properties, and the like. The polarizing element can be produced by forming the substrate into a film shape, adsorbing the azo compound or other formulation onto the film-shaped substrate, and applying orientation treatment such as stretching.

The method for producing the polyvinyl alcohol resin is not particularly limited, and a known production method can be used. The polyvinyl alcohol resin can be produced, for example, by saponifying a polyvinyl acetate resin (a homopolymer or copolymer of vinyl acetate). Examples of the polyvinyl acetate resin include polyvinyl acetate which is a homopolymer of vinyl acetate, and a copolymer of another monomer copolymerizable with vinyl acetate. Examples of the copolymer of another monomer copolymerizable with vinyl acetate include copolymers of unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The polyvinyl alcohol resin may be modified, and for example, polyvinyl formaldehyde or polyvinyl acetaldehyde modified with aldehydes may be used.

The saponification degree of the polyvinyl alcohol resin is not limited, but is usually 85% or more, more preferably 95% or more, still more preferably 99% or more, and particularly preferably 99.5% or more, from the viewpoint of preventing elution of the polyvinyl alcohol resin, in-plane unevenness in optical properties, reduction in dyeability in a dyeing step, or significant reduction in productivity due to initiation of cutting in an elongation step.

The polymerization degree of the polyvinyl alcohol resin is not limited, but 10000 or less is preferable from the industrial viewpoint of preventing the polyvinyl alcohol resin from becoming hard, or from lowering the film-forming property and the elongation property to lower the productivity. In order to improve the optical characteristics of the polarizing element, the polymerization degree of the polyvinyl alcohol resin is preferably 1000 to 10000, more preferably 2000 to 10000, still more preferably 3500 to 10000, particularly preferably 5000 to 10000. The polymerization degree of the polyvinyl alcohol resin is a viscosity average polymerization degree, and can be determined by a known method in this technical field.

Hereinafter, a specific method for producing a polarizing element will be described by taking as an example a case where the substrate is a film made of a polyvinyl alcohol resin.

First, a green film made of the polyvinyl alcohol resin is obtained by forming a film of the polyvinyl alcohol resin. The film-forming method of the polyvinyl alcohol resin may employ: a method of melt-extruding a water-containing polyvinyl alcohol resin; a vertical flow film formation method, a wet film formation method (a method of forming a film by discharging in a weak solvent); a gel film-forming method (a method of cooling and gelling an aqueous solution of a polyvinyl alcohol resin once, and then removing a solvent by extraction); a cast film-forming method (a method in which an aqueous solution of a polyvinyl alcohol resin is flowed onto a substrate and dried); and a method of combining these methods, but these methods are not limited.

The solvent used in the above-mentioned film formation is not particularly limited, and examples thereof include dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone (Methyl pyrollidone), ethylene glycol, glycerol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, trimethylolpropane, ethylenediamine, diethylenetriamine, and water. The solvent may be used in 1 kind, or 2 or more kinds may be mixed and used. The amount of the solvent used for film formation is not limited, but is preferably 70% by weight or more based on the whole film-forming stock solution (a mixed solution containing a polyvinyl alcohol resin and a solvent used for film formation) from the viewpoints of preventing the viscosity of the film-forming stock solution from increasing, making it difficult to filter or defoam the film during preparation, and making it difficult to obtain a blank film free of foreign matter or defects. The amount of the solvent is preferably 95% by weight or less from the viewpoints of preventing the viscosity of the film forming solution from being too low, making it difficult to control the target thickness, increasing the influence of surface shaking by wind during drying, increasing the drying time, and reducing the productivity.

A plasticizer may be used in the production of the embryonic film. Examples of the plasticizer include glycerin, diglycerin, ethylene glycol, propylene glycol, and low-molecular-weight polyethylene glycol, but are not limited thereto. The amount of the plasticizer to be used is not particularly limited, but is usually preferably in the range of 5 to 15 parts by weight based on 100 parts by weight of the polyvinyl alcohol resin.

Examples of the method for drying the embryonic membrane after the film formation include, but are not limited to, drying with hot air, contact drying using a hot roll, and drying with an infrared heater. Further, 1 kind of these drying methods may be used alone, or 2 or more kinds may be used in combination. The drying temperature is also not particularly limited, but is preferably in the range of 50 to 70 ℃.

The embryonic film after the drying is preferably subjected to a heat treatment in order to control the degree of swelling to a predetermined range described later. The heat treatment method is not particularly limited as long as it is a method capable of passing heat treatment, and examples thereof include a method of hot air and a method of contacting a green film with a hot roll. Further, 1 kind of these methods may be used alone, or 2 or more kinds may be used in combination. The heat treatment temperature is not particularly limited, but is preferably in the range of 110 to 140 ℃. The time for the heat treatment is preferably 1 to 10 minutes, but is not particularly limited.

The thickness of the embryonic membrane obtained in the above step is not limited, but is preferably 20 μm or more from the viewpoint of preventing the membrane from easily breaking. Further, from the viewpoint of preventing an increase in stress applied to the film during stretching, an increase in mechanical load in the stretching step, and the necessity of a large-scale apparatus for withstanding the load, 100 μm or less is preferable. More preferably 20 to 80 μm, still more preferably 20 to 60 μm.

The green film made of the polyvinyl alcohol resin obtained in the above step is subjected to a swelling step.

The swelling step is performed by immersing the embryonic membrane made of a polyvinyl alcohol resin in a solution at 20 to 50 ℃ for 30 seconds to 10 minutes. The solution is preferably an aqueous solution. Since swelling of the film may occur during the dyeing treatment of the azo compound, the swelling step may be omitted in the case of shortening the time required for producing the polarizing element.

The swelling degree F of the embryonic membrane is not limited, but is preferably 180% or more, more preferably 200% or more, from the viewpoint of preventing a significant decrease in elongation at the time of elongation, increasing the possibility of breakage, and making sufficient elongation difficult. In addition, from the viewpoint of preventing significant wrinkles, sagging, and cutting during stretching, 260% or less is more preferable, and 240% or less is more preferable. More preferably 200 to 240%, still more preferably 210 to 230%. In order to control the degree of swelling F, for example, the degree of swelling F can be selected appropriately at a temperature and a time when the heat treatment is performed on the formed embryonic membrane.

The swelling degree F of the embryonic membrane can be measured by a method known in the art, for example, the following method. First, the embryonic membrane was cut into 5cm × 5cm, and immersed in distilled water at 30 ℃ for 1 liter of 4 hours. The immersed membrane was taken out from the distilled water, and water droplets on the membrane surface were absorbed by the filter paper with 2 sheets of filter paper therebetween, and then the weight "β (g)" of the membrane immersed in water was measured. The membrane impregnated with the absorbed water droplets was dried in a dryer at 105 ℃ for 20 hours, cooled in a decanter for 30 minutes, and then the weight "γ (g)" of the dried membrane was measured. Then, the swelling degree F of the embryonic membrane was calculated by the following numerical formula (v).

Swelling degree F ═ 100 × β/γ (%). v)

After the above step, a dyeing step is performed. In the dyeing step, the azo compound represented by each of the formulae (1) and (2) and optionally other azo compounds (the azo compound represented by the formula (4) or the other organic dye described above) (hereinafter also referred to as "azo compound(s) of the formula (1)) are adsorbed to the polyvinyl alcohol resin film.

The dyeing step is not particularly limited as long as the azo compound of formula (1) or the like can be adsorbed on the polyvinyl alcohol resin film, but can be performed, for example, by immersing the polyvinyl alcohol resin film in a solution containing the azo compound of formula (1) or the like. The temperature of the solution in the dyeing step is more preferably 5 to 60 ℃, still more preferably 20 to 50 ℃, particularly preferably 35 to 50 ℃. The time for immersion in the solution may be appropriately adjusted, but is preferably adjusted to 30 seconds to 20 minutes, more preferably 1 to 10 minutes. The dyeing method is preferably a method of immersing the polyvinyl alcohol resin film in the above solution, but may be a method of applying the solution to the polyvinyl alcohol resin film.

The solution containing the azo compound of formula (1) and the like may contain sodium carbonate, sodium hydrogencarbonate, sodium chloride, sodium sulfate, anhydrous sodium sulfate, sodium tripolyphosphate and the like as a dyeing assistant. The content of the dyeing assistant may be adjusted to any concentration according to the time and temperature of dyeing by dyeing property, but is preferably 0 to 5% by weight, more preferably 0.1 to 2% by weight.

After the dyeing step, a washing step (hereinafter, referred to as "washing step 1") may be performed. The washing step 1 is a step of washing the dye solvent attached to the surface of the polyvinyl alcohol resin film in the dyeing step with a washing liquid. By performing this washing step 1, migration of the dye in the solution to be treated next can be suppressed. This washing step 1 generally uses water as the washing liquid. The specific step of the washing step 1 is not particularly limited, and a method of immersing the resin film in a washing liquid is preferable, but a method of applying a washing liquid to a polyvinyl alcohol resin film may be used. The time required for the washing step 1 is not particularly limited, but is preferably 1 to 300 seconds, more preferably 1 to 60 seconds. The temperature of the washing liquid in the washing step 1 must be a temperature at which the hydrophilic polymer is insoluble, and is generally 5 to 40 ℃.

After the dyeing step or after the washing step 1, a step of including at least 1 kind of crosslinking agent and/or hydrolysis resistance agent in the polyvinyl alcohol resin film may be performed. For example, boric acid, boron compounds such as borax or ammonium borate, polyaldehydes such as glyoxal or glutaraldehyde, polyisocyanate-based compounds such as biuret, isocyanurate, or block, titanium-based compounds such as titanyl sulfate, etc. may be used as the crosslinking agent, and other compounds such as ethylene glycol glycidyl ether and polyamide epichlorohydrin may be used, but boric acid is more preferable. Examples of the hydrolysis resistance agent include succinic peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerol diglycidyl ether, ammonium chloride, magnesium chloride, and the like.

The crosslinking agent and/or hydrolysis resistant agent used in the step of containing the crosslinking agent and/or hydrolysis resistant agent in the polyvinyl alcohol resin film is usually used in the state of a solution dissolved in a solvent. The solvent is preferably water, but is not limited thereto. The concentration of the crosslinking agent and/or hydrolysis resistant agent contained in the solution in this step is preferably 0.1 to 6.0% by weight, more preferably 1.0 to 4.0% by weight, based on the solvent, as represented by boric acid as an example. The temperature of the above solution used in this step is preferably 5 to 70 ℃ and more preferably 5 to 50 ℃. The method of containing the crosslinking agent and/or the hydrolysis resistant agent in the polyvinyl alcohol resin film is more preferably a method of immersing the polyvinyl alcohol resin film in a solution of the crosslinking agent and/or the hydrolysis resistant agent, but may be a method of applying the solution to the polyvinyl alcohol resin film. The time required for this step is more preferably 30 seconds to 6 minutes, and still more preferably 1 to 5 minutes. However, this step can be omitted when it is not necessary to add a crosslinking agent and/or a hydrolysis resistant agent to the polyvinyl alcohol resin film and the time required for producing the polarizing element is to be shortened, or when crosslinking treatment or hydrolysis resistant treatment is not necessary.

After the dyeing step, or after the washing step 1, or after the step of containing the crosslinking agent and/or hydrolysis resistant agent, an elongation step is performed. The stretching step is a step of stretching the polyvinyl alcohol resin film toward the 1-axis. The stretching method may be either wet stretching or dry stretching. The elongation is 3 times or more, although the present invention can be achieved, more preferably 5 times to 7 times. The elongation step may be performed by elongation in 1 stage, but may be performed by elongation in a plurality of stages of 2 stages or more.

In the case of the dry drawing method, when the drawing heating medium is an air medium, the temperature of the air medium at the time of drawing is preferably from room temperature to 180 ℃. In addition, it is preferable to perform the stretching treatment in an atmosphere with a humidity of 20 to 95% RH. Specific examples of the stretching method include, but are not limited to, inter-roll zone stretching, roll heating stretching, rolling stretching, infrared heating stretching, and the like.

In the case of the wet stretching method, it is preferable to perform stretching treatment by stretching the polyvinyl alcohol resin film in water, a water-soluble organic solvent, or a mixed solution thereof, and immersing the polyvinyl alcohol resin film in a solution containing the crosslinking agent and/or hydrolysis resistant agent. The crosslinking agent and/or hydrolysis resistant agent can be the same as those described above, but boric acid or borax is more preferable, and boric acid is particularly preferable. The stretching of the polyvinyl alcohol resin film is performed in a solution containing at least 1 or more kinds of crosslinking agents and/or hydrolysis resistance agents. The concentration of the crosslinking agent and/or hydrolysis resistance agent in the foregoing elongation step is, for example, more preferably 0.5 to 15% by weight, and still more preferably 2.0 to 8.0% by weight. The draw ratio is more preferably 2 to 9 times, still more preferably 5 to 8 times. The stretching temperature is more preferably 40 to 70 ℃ and still more preferably 45 to 60 ℃. The extension time is usually 30 seconds to 20 minutes, but 1 to 5 minutes is more preferable. The wet stretching step may be performed by 1-stage stretching, but may be performed by 2-stage or more multi-stage stretching.

After the above-mentioned stretching step, a washing step of washing the film surface (hereinafter referred to as "washing step 2") may be performed because the crosslinking agent and/or hydrolysis resistant agent may precipitate or foreign matter may adhere to the film surface. The time required for the washing step 2 is preferably 1 second to 5 minutes. The washing method in the washing step 2 is preferably a method of immersing in a washing liquid, but a method of applying a washing liquid to a polyvinyl alcohol resin film may be used. The washing step 2 may be a 1-stage treatment or a multi-stage treatment of 2 stages or more. The temperature of the washing liquid used in the washing step 2 is not particularly limited, but is usually 5 to 50 ℃, and more preferably 10 to 40 ℃.

Examples of the solvent that can be used in each step include water; dimethyl sulfoxide; n-methylpyrrolidone (Methyl pyrrolidone); alcohols such as methanol, ethanol, propanol, isopropanol, glycerol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and trimethylolpropane; and amines such as ethylenediamine and diethylenetriamine, but not limited thereto. In addition, a mixture of 2 or more of these solvents may also be used. The most preferred solvent is water.

After the stretching step or the washing step 2, a step of drying the polyvinyl alcohol resin film is performed. The drying step may be natural drying, but in order to further improve the drying efficiency, the moisture on the surface may be removed by means of compression with a roller, an air knife (air knife), a water absorbing roller, or the like, or the air drying may be performed simultaneously with or instead of the moisture removal. The temperature of the drying step is more preferably 20 to 100 ℃ and still more preferably 60 to 100 ℃. The time required for this drying step may be in the range of 30 seconds to 20 minutes, but is more preferably 5 to 10 minutes.

The polarizing element of the present invention can improve optical characteristics by using a base material, and an azo compound represented by formula (1) and an azo compound represented by formula (2). In one embodiment, the polarizing element of the present invention also has excellent durability.

< polarizing plate >

The polarizing plate of the present invention comprises: the polarizer includes a polarizer and a transparent protective layer provided on one or both surfaces of the polarizer. The transparent protective layer may be provided as a coating layer made of a transparent polymer or a laminate of transparent films. The transparent polymer or transparent film forming the transparent protective layer is preferably a transparent polymer or transparent film having high mechanical strength and good thermal stability. Examples of the transparent polymer or transparent film used for the transparent protective layer include cellulose acetate resins such as triacetylcellulose or diacetylcellulose or films thereof, acrylic resins or films thereof, polyvinyl chloride resins or films thereof, nylon resins or films thereof, polyester resins or films thereof, polyacrylate resins or films thereof, cyclic polyolefin resins or films thereof containing cyclic olefins such as norbornene as monomers, polyethylene, polypropylene, polyolefins having a ring system to norbornene skeleton or copolymers thereof, polymers (or resins) having imide and/or amide in the main chain or side chain, or films thereof. The transparent protective layer may be provided with a liquid crystalline resin or a film thereof. The thickness of the protective film is, for example, about 0.5 to 200 μm. The polarizer may be provided with 1 layer of resin or film on one surface thereof, 2 or more layers of the same or different type of resin or film on one surface thereof, or 1 or more layers of the same or different type of resin or film on both surfaces thereof.

In order to bond the transparent protective layer and the polarizing element, an adhesive may be used. The adhesive is not particularly limited, but a polyvinyl alcohol adhesive is more preferable. Examples of the polyvinyl alcohol adhesive include, but are not limited to, Gohsenol (registered trademark) NH-26 (manufactured by Nippon synthetic chemical industries Co., Ltd.), Exceval (registered trademark) RS-2117 (manufactured by Kuraray Co., Ltd.), and the like. A crosslinking agent and/or a hydrolysis resistant agent may be added to the adhesive. The polyvinyl alcohol adhesive may be mixed with a maleic anhydride-isobutylene copolymer, and in this case, a crosslinking agent may be optionally mixed. Examples of the maleic anhydride-isobutylene copolymer include Isobam (registered trademark) #18 (manufactured by Kuraray Co., Ltd.), Isobam (registered trademark) #04 (manufactured by Kuraray Co., Ltd.), ammonia-modified Isobam (registered trademark) #104 (manufactured by Kuraray Co., Ltd.), ammonia-modified Isobam (registered trademark) #110 (manufactured by Kuraray Co., Ltd.), imidized Isobam (registered trademark) #304 (manufactured by Kuraray Co., Ltd.), and imidized Isobam (registered trademark) #310 (manufactured by Kuraray Co., Ltd.). The crosslinking agent optionally mixed with the maleic anhydride-isobutylene copolymer may use a water-soluble polyepoxy compound. Examples of the water-soluble polyepoxy compound include Denacol EX-521 (manufactured by Nagasechemx Co., Ltd.), and TETRAD (registered trademark) -C (manufactured by Mitsubishi GAS chemical Co., Ltd.). In addition, as the adhesive, known adhesives other than a polyvinyl alcohol adhesive such as a urethane adhesive, an acrylic adhesive, and an epoxy adhesive can be used. In addition, additives such as zinc compounds, chlorides, and iodides may be added to the adhesive in a concentration of about 0.1 to 10 wt% for the purpose of improving the adhesion of the adhesive and improving the water resistance. The additive is not limited to this. The polarizing plate is obtained by bonding a transparent protective layer to one or both sides of the polarizing element with an adhesive and then drying or heat-treating the bonded layer at an appropriate temperature.

The polarizing plate is optional, and in the case of being bonded to a display device such as a liquid crystal display device or an organic electroluminescence (organic light emitting diode) display device, various functional layers for improving a viewing angle and/or contrast, a layer or a film having a luminance improving property may be provided on the surface of the transparent protective layer which is a non-exposed surface after bonding. It is preferable to use an adhesive for bonding a polarizing plate to a layer or a film of these or a display device. Examples of the material constituting the adhesive layer include suitable polymers such as acrylic resins, silicone resins, polyesters, polyurethanes, polyamides, polyethers, fluororesins, and rubbers, as base polymers, and more preferably acrylic (co) polymer resin compositions using acrylic resins, and techniques using acrylic (co) polymer resin compositions include, but are not particularly limited to, those described in jp 59-111114 a and jp 4-254803 a.

The polarizing plate may be provided with various known functional layers such as an antireflection layer, an antiglare layer, and a hard coat layer on the other surface of the transparent protective layer, that is, on the exposed surface. In order to produce these various functional layers, a coating method is preferred, but a method of bonding a film having a function thereof via the adhesive or the pressure-sensitive adhesive may be used. In addition, the functional layer may be a layer or a film that controls retardation.

The polarizing plate of the present invention, which comprises a polarizing element comprising a base material and an azo compound represented by formula (1) and an azo compound represented by formula (2), and a transparent protective layer provided on one or both sides of the polarizing element, has improved optical properties by using the azo compound represented by formula (1) and the azo compound represented by formula (2). In one embodiment, the polarizing element of the present invention is also excellent in durability against light, heat, and humidity.

< optical Member, etc. >

The polarizing element and the polarizing plate of the present invention can be used for optical members, machines, or devices (optical members and the like). The optical member and the like using the polarizing element or the polarizing plate of the present invention have high contrast. In one embodiment, the optical member and the like of the present invention have high durability and the high contrast is maintained for a long period of time.

The polarizing element and the polarizing plate of the present invention are provided with a protective layer, a functional layer, a support, and the like as needed, and can be used in display devices such as liquid crystal projectors, electronic computers, clocks, notebook computers, document processors, liquid crystal televisions, polarizing lenses, polarizing glasses, head-up displays, navigators, organic electroluminescence displays, and indoor and outdoor meters and displays, and optical devices such as these.

In the method of applying the polarizing plate of the present invention, the polarizing plate of the present invention may be attached to a support, and the polarizing plate as the attached support may be used. The support is preferably a polarizing plate having a flat surface portion. The support is preferably a glass molded product for optical use. Examples of the glass molded article include a glass plate, a lens, and a prism (e.g., a triangular prism, a cubic prism). For example, a capacitor lens with a polarizing plate can be used in a liquid crystal projector by attaching a polarizing plate to the lens. In addition, a polarizing plate may be attached to a lens, and a polarizing beam splitter with a polarizing plate or a bidirectional prism with a polarizing plate may be used in a liquid crystal projector. In addition, a polarizing plate may be attached to the liquid crystal cell. Examples of the material of the glass molded article include inorganic glasses such as soda glass, borosilicate glass, crystal, and sapphire, and organic polymers such as acrylic resin and polycarbonate. The thickness or size of the glass plate may be set to a desired size according to the object. In the polarizing plate with a support made of glass, an antireflection layer (Ar layer) is preferably provided on one or both of the glass surface and the polarizing plate surface in order to further improve the single-plate light transmittance. In this case, a transparent adhesive (pressure-sensitive adhesive) is applied to the surface of the support, for example, the surface of the flat surface of the support, and the polarizing plate of the present invention is attached to the applied surface. Alternatively, a transparent adhesive (pressure-sensitive adhesive) may be applied to the polarizing plate, and then the support may be attached to the applied surface. The adhesive (sticking agent) used herein is preferably an acrylate, for example. In the case where the polarizing plate and the retardation plate are used in combination as an elliptical polarizing plate, the retardation plate side of the elliptical polarizing plate is usually attached to the support, but the support may be attached to the polarizing plate side of the elliptical polarizing plate.

A display device including the polarizing element of the present invention or the polarizing plate of the present invention is also one embodiment of the present invention. In addition, one of particularly preferable applications of the polarizing plate of the present invention is a liquid crystal display device. The liquid crystal display device may be, for example, a reflection type, transmission type, or transmission/reflection type liquid crystal display device including a liquid crystal cell, and a polarizing element of the present invention or a polarizing plate of the present invention disposed on one side or both sides of the liquid crystal cell. The liquid crystal cell may be any suitable type, for example, an active matrix type liquid crystal cell typified by a thin film transistor type, or a simple matrix type liquid crystal cell typified by a twisted nematic or super twisted nematic type. A display device including the polarizing element or the polarizing plate of the present invention can provide not only high polarization degree, that is, contrast, but also high durability. The durability of the display device is reduced by not changing color and reducing contrast even in an environment of 115 ℃ or 85 ℃ with a relative humidity of 85%. When the contrast value is 100 or more and the polarization degree is 98% or more, the display device is more preferably a display device, more preferably a display device having a contrast value of 1000 or more and a polarization degree of 99% or more, and most preferably a display device having a contrast value of 1100 or more and a polarization degree of 99.9% or more.

In the liquid crystal display device of the present invention, for example, 1 or 2 or more prism array sheets, lens array sheets, light diffusion plates, backlights, and other suitable optical members may be disposed at appropriate positions. In the case where the polarizing element of the present invention, the polarizing plate of the present invention, or another optical member is provided, these may be the same on both sides or may be different on both sides.

The liquid crystal display device of the present invention may have an adhesive layer for adhering to other members such as a liquid crystal cell on one side or both sides of the polarizing element of the present invention or the polarizing plate of the present invention. The adhesive layer may be formed using any adhesive substance or adhesive, and is not particularly limited. Examples of the material constituting the adhesive layer include base polymers and the like made of suitable polymers such as acrylic resins, silicone resins, polyesters, polyurethanes, polyamides, polyethers, fluororesins, and rubbers.

The liquid crystal display device of the present invention can be used for all liquid crystal display devices such as Twisted Nematic (TN) type, Super Twisted Nematic (STN) type, Thin Film Transistor (TFT) type, Vertical Alignment (VA) type, and in-plane switching (IPS) type.

[ examples ]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited thereto. The transmittance, the polarization degree, and the contrast ratio of the polarizing plates obtained in examples and comparative examples were evaluated as follows.

[ method for measuring transmittance and polarization degree of polarizing plate ]

The transmittance at each wavelength of 1 polarizing plate was assumed to be the single transmittance Ts, the transmittance at each wavelength when 2 polarizing plates were overlapped so that the absorption axis directions of the polarizing plates were the same was assumed to be the parallel bit transmittance Tp, the transmittance at each wavelength when 2 polarizing plates were overlapped so that the absorption bearings thereof were orthogonal was assumed to be the orthogonal bit transmittance Tc, the single transmittance corrected for the visibility by the chromaticity function (C light source 2 ° field of view) was assumed to be Ys, the parallel bit transmittance corrected for the visibility by the chromaticity function (C light source 2 ° field of view) was assumed to be Yp, and the orthogonal bit transmittance corrected for the visibility by the chromaticity function (C light source 2 ° field of view) was assumed to be Yc. The respective transmittances Ts, Tp, Tc, Ys, Yp, and Yc were measured at 5nm intervals using a spectrophotometer ("U-4100" manufactured by Hitachi High Technologies, Ltd.).

The polarization degree ρ y (%) of the polarizing plate is determined from the parallel bit transmittance Yp for the visibility correction and the cross bit transmittance Yc for the visibility correction in accordance with the following formula (6).

ρy(％)＝{(Yp-Yc)/(Yp+Yc)}^1/2×100…(6)

The contrast ratio CR is calculated from the parallel bit transmittance Yp of the visibility correction and the quadrature bit transmittance Yc of the visibility correction according to the following expression (7).

CR＝Yp/Yc…(7)

[ example 1]

< fabrication of polarizing element >

A polyvinyl alcohol film having a saponification degree of 99% or more and a film thickness of 60 μm (VF-PE #6000 manufactured by Kuraray Co., Ltd.; hereinafter simply referred to as "film") was used as a substrate. The resultant was immersed in 35 ℃ warm water for 3 minutes and subjected to swelling treatment. 0.25 parts by weight of the compounds of examples 1 to 3 of the azo compound of the formula (1) (synthesized in example 1 of Japanese unexamined patent publication No. 8-291259 by changing 6.9 parts of 1-amino-2-methoxy-5-methylbenzene to 5.4 parts of 1-amino-5-methylbenzene), 1.5 parts by weight of the azo compound of examples 2 to 4 of the azo compound of the formula (2) (the azo compound of the formula (2) described in Compound example 45 of International publication No. 2012/108169), 0.14 parts by weight of the azo compound of examples 4 to 2 of the azo compound of the formula (4) (the azo compound of the formula (2) described in example 1 of International publication No. 2007/138980), and 2.0 parts by weight of sodium tripolyphosphate, And 2000 parts by weight of water were mixed to prepare an aqueous solution at 45 ℃. The swollen membrane was immersed in the 45 ℃ aqueous solution, and the azo compounds were adsorbed on the membrane. The film having adsorbed each of the azo compounds was washed with water and then immersed in an aqueous solution containing 2 wt% of boric acid at 40 ℃ for 1 minute (boric acid treatment). The film obtained by the boric acid treatment was stretched 6.0 times and immersed in an aqueous solution at 58 ℃ containing 3.0 wt% of boric acid for 5 minutes (boric acid treatment). The membrane obtained by the boric acid treatment was immersed in water at normal temperature for 20 seconds while being in a stretched state (washing treatment). The film obtained by the washing treatment was immediately dried at 60 ℃ for 5 minutes to obtain a polarizing element having a monomer transmittance of about 41% and a film thickness of 23 μm. In the above manner, a polarizing element using a polyvinyl alcohol film containing the azo compound represented by each of the formulae (1), (2), and (4) was produced.

< production of polarizing plate >

Both sides of the polarizing element obtained above were laminated (Laminate) in a constitution of TAC/adhesive layer/polarizing element/adhesive layer/TAC by using a polyvinyl alcohol adhesive and an alkali-treated triacetyl cellulose FILM (TD-80U manufactured by Fuji FILM Co., Ltd.; hereinafter, abbreviated as "TAC") with a FILM thickness of 80 μm. Accordingly, a polarizing plate was obtained. The obtained polarizing plate was used as a measurement sample.

[ example 2]

As the azo compound represented by the above formula (2), a polarizing element having a monomer transmittance of about 41% and a film thickness of 23 μm and a polarizing plate were prepared as measurement samples using polyvinyl alcohol films containing the azo compounds represented by the above formulae (1), (2) and (4) in the same manner as in example 1 except that 2.2 parts by weight of the azo compound of compound examples 2 to 19 of the present application (synthesized by changing 7.7 parts of 2, 5-dimethylaniline used in the steps of obtaining formulae (70) to (71) to 9.7 parts of 2, 5-dimethoxyaniline) was used instead of the azo compound of compound examples 2 to 4 of the present application of example 1 in example 4 of international publication No. 2012/108169).

[ example 3]

As the azo compound represented by the above formula (2), a polarizing element having a monomer transmittance of about 41% and a film thickness of 23 μm and a polarizing plate were prepared as measurement samples using polyvinyl alcohol films containing the azo compounds represented by the above formulae (1), (2) and (4) in the same manner as in example 1 except that 2.1 parts by weight of the azo compound of compound examples 2 to 13 of the present application (synthesized by changing 7.7 parts of 2, 5-dimethylaniline used in the steps of obtaining formulae (70) to (71) to 9.7 parts of 2, 5-dimethoxyaniline) was used instead of the azo compound of compound examples 2 to 4 of the present application of example 1 in example 3) of the present application shown in formula (2) to 13 of the present application shown in international publication No. 2012/108169.

[ example 4]

As the azo compound represented by the above formula (2), a polyvinyl alcohol film containing azo compounds represented by the above formula (1), the above formula (2) and the above formula (4) was used in the same manner as in example 1 except that 1.45 parts by weight of the azo compound of the present application example 2-17 (obtained by changing 7.7 parts of 2, 5-dimethylaniline used in the steps of obtaining the formula (70) to the formula (71) to 9.7 parts of 2, 5-dimethoxyaniline and further changing 16.1 parts of 6-phenylamino-1-naphthol-3-sulfonic acid of the 4-time coupling agent to 17.6 parts of 6- [ (4-hydroxyphenyl) azo ] -1-naphthol-3-sulfonic acid) was used in place of the azo compound of the present application example 2-4 of example 1, a polarizer having a single transmittance of about 41% and a film thickness of 23 μm and a polarizing plate were prepared as measurement samples.

[ example 5]

As the azo compound represented by the above formula (2), a polarizing element having a monomer transmittance of about 41% and a film thickness of 23 μm and a polarizing plate were prepared as measurement samples using polyvinyl alcohol films containing the azo compounds represented by the above formulae (1), (2) and (4) in the same manner as in example 1 except that 1.9 parts by weight of the azo compound of compound examples 2 to 25 of the present application (synthesized by changing 7.7 parts of 2, 5-dimethylaniline used in the steps of obtaining the formulae (68) to (69) to 9.7 parts of 2, 5-dimethoxyaniline) was used instead of the azo compound of compound examples 2 to 4 of the present application of example 1 in example 2 of international publication No. 2012/108173).

[ example 6]

As the azo compound represented by the above formula (1), a polarizing element having a monomer transmittance of about 42% and a film thickness of 23 μm and a polarizing plate were produced using polyvinyl alcohol films containing the azo compounds represented by the above formulae (1), (2) and (4) as measurement samples in the same manner as in example 1 except that 0.18 parts by weight of the azo compound of compound examples 1 to 9 (synthesized by changing 34.6 parts of a hydrogen sulfide acid to 36.2 parts of 5-aminoisophthalic acid and 6.9 parts of 1-amino-2-methoxy-5-methylbenzene to 5.4 parts of 1-amino-5-methylbenzene in example 1) was used instead of the azo compound of compound examples 1 to 3 of example 1).

[ example 7]

As the azo compound represented by the above formula (1), a polyvinyl alcohol film containing the azo compounds represented by the above formula (1), formula (2) and formula (4) was used in the same manner as in example 1 except that 0.25 part by weight of the azo compound of the present application examples 1 to 8 (which was synthesized by changing 34.6 parts of a hydrogen sulfide acid to 51.0 parts of 2, 4-disulfanilide, 6.9 parts of 1-amino-2-methoxy-5-methylbenzene to 4.7 parts of aniline, and 15.8 parts of 1-hydroxynaphthalene-6-phenylamino-3-sulfonic acid to 12.7 parts of 1-hydroxynaphthalene-6-methylamino-3-sulfonic acid in example 1) was used instead of the azo compound of the present application examples 1 to 3 of example 1, a polarizer having a single transmittance of about 41% and a film thickness of 23 μm and a polarizing plate were prepared as measurement samples.

[ example 8 ]

A polyvinyl alcohol film containing azo compounds represented by the above formula (1), formula (2) and formula (4) was used in the same manner as in example 1 except that the azo compound of example 1-17 (International publication No. 2015/152026, example 1, in which 39.8 parts of 6- (4-aminobenzoylamino) -4-hydroxynaphthalene-2-sulfonic acid used in the synthesis of formula (80) was changed to 48.7 parts of 6- (4-aminobenzoylamino) -4-hydroxynaphthalene-2-sulfonic acid, and 12.1 parts of 3-methylaniline used in the synthesis of formula (81) was changed to 10.5 parts of aniline) was used as the azo compound of formula (1), and 0.21 parts by weight of the azo compound was used in place of the azo compound of example 1-3 of example 1, a polarizer having a single transmittance of about 41% and a film thickness of 23 μm and a polarizing plate were prepared as measurement samples.

[ example 9 ]

As the azo compound represented by the above formula (1), compounds of examples 1 to 21 (obtained by changing 39.8 parts of 7- (4-aminobenzoylamino) -4-hydroxynaphthalene-2-sulfonic acid used in the synthesis of the formula (82) in example 2 of International publication No. 2015/152026 to 48.7 parts of 6- (4-aminobenzoylamino) -4-hydroxynaphthalene-2-sulfonic acid, changing 12.1 parts of 2, 5-methylaniline used in the synthesis of the formula (83) to 10.5 parts of aniline, changing 9.7 parts of 2, 5-dimethylaniline used in the synthesis of the formula (84) to 8.4 parts of aniline, and changing 17.7 parts of 7-phenylamino-4-hydroxynaphthalene-2-sulfonic acid to 20.1 parts of 7- (4-aminobenzoylamino) -4-hydroxynaphthalene-2-sulfonic acid) were used A polarizing element having a monomer transmittance of about 42% and a film thickness of 23 μm and a polarizing plate were prepared as measurement samples using polyvinyl alcohol films containing azo compounds represented by the above formulae (1), (2) and (4) in the same manner as in example 1 except that 0.29 part of an azo compound was used instead of the azo compounds of the present application of example 1 and examples 1 to 3.

[ example 10 ]

As the azo compound represented by the above formula (4), a polarizing element having a monomer transmittance of about 41% and a film thickness of 23 μm and a polarizing plate were produced as a measurement sample using a polyvinyl alcohol film containing the azo compound represented by each of the above formulae (1), (2) and (4) in the same manner as in example 1 except that 0.20 parts by weight of the azo compound described in compound example 4-1 of the present application was used instead of the azo compound of compound example 4-2 of example 1 of the present application. The compound example 4-1 of the present application was obtained by the following synthesis method. First, 10.8 parts of hydrogen sulfide acid was added to 500 parts of water and dissolved in sodium hydroxide. After cooling, 32 parts of 35% hydrochloric acid was added thereto at 10 ℃ or lower, 6.9 parts of sodium nitrite was added thereto, and the mixture was stirred at 5 to 10 ℃ for 1 hour. To this was added 20.9 parts of sodium aniline- ω -methanesulfonate, and sodium carbonate was added while stirring at 20 to 30 ℃ to prepare a solution having a pH of 3.5. The coupling reaction was terminated by further stirring, and filtration was carried out to obtain 17 parts of a monoazo compound. After 12 parts of the obtained monoazo compound and 21 parts of 4,4 '-dinitrostilbene-2, 2' -sulfonic acid were dissolved in 300 parts of water, 12 parts of sodium hydroxide were added thereto, and condensation reaction was carried out at 90 ℃. Then, 9 parts of glucose was reduced, salting out was performed with sodium chloride, and then filtration was performed to obtain 16 parts of an azo compound represented by compound example 4-1 of the present application.

[ example 11 ]

A polarizing element having a monomer transmittance of about 41% and a film thickness of 23 μm and a polarizing plate were produced as measurement samples using polyvinyl alcohol films containing azo compounds represented by the above formulae (1) and (2) in the same manner as in example 1, except that c.i. direct yellow 28 described in non-patent document 2 was used instead of the azo compound of compound example 4-2 of the present application in example 1.

[ example 12 ]

A polarizer having a monomer transmittance of about 41% and a film thickness of 23 μm and a polarizing plate were produced as measurement samples using polyvinyl alcohol films containing azo compounds represented by the above formulae (1) and (2) in the same manner as in example 1 except that c.i.direct orange 72 was used instead of the azo compound in compound example 4-2 of the present application of example 1.

[ comparative example 1]

A polarizing element having a monomer transmittance of about 40% and a film thickness of 23 μm was produced using the azo compound described in example 2 of Japanese patent application laid-open No. 11-218611, and a polarizing plate was produced, and the thus produced polarizing plate was used as a measurement sample.

[ comparative example 2]

A polarizing element having a monomer transmittance of about 41% and a film thickness of 23 μm was produced using the azo compound described in example 3 of Japanese patent application laid-open No. 2001-033627, and a polarizing plate was produced, and the thus produced polarizing plate was used as a measurement sample.

[ comparative example 3]

A polarizer having a monomer transmittance of about 41% and a film thickness of 23 μm was produced using the azo compound described in example 1 of Japanese patent application laid-open No. 2004-251962, and a polarizing plate was produced, and the thus produced polarizing plate was used as a measurement sample.

[ comparative example 4]

A polarizer having a monomer transmittance of about 41% and a film thickness of 23 μm and a polarizing plate were produced as a measurement sample using a polyvinyl alcohol film containing an azo compound in the same manner as in example 1 except that 0.2 parts by weight of c.i.direct red 81, which is a cis-azo dye having the same color, was used instead of the azo compound in compound examples 1 to 3 of example 1 so that the monomer transmittance could be adjusted to 41% by the dyeing time of example 1.

[ comparative example 5]

A polarizer having a monomer transmittance of about 41% and a 23 μm thickness was produced and a polarizing plate was produced as a measurement sample by using a polyvinyl alcohol film containing an azo compound in the same manner as in example 1 except that 0.2 part by weight of the dye (azo compound) described in example 1 of Japanese patent publication No. 64-5623 of the azo compound showing the same color blue was used in place of the azo compound in compound examples 2-4 of example 1 in the manner of adjusting the monomer transmittance to 41% in the dyeing time of example 1.

< evaluation of optical Properties >

Table 1 shows the measurement results of the monomer transmittance Ys (%), the parallel transmittance Yp (%), the orthogonal transmittance Yc (%), the polarization degree ρ y (%) and the contrast value CR in the polarizing plates of examples 1 to 12 and comparative examples 1 to 5.

[ TABLE 1]

As can be seen from table 1, the polarizing plates of the present invention of examples 1 to 12 are polarizing plates having improved polarizing performance and contrast as compared to those using a known azo compound.

< evaluation of durability >

Next, changes in optical characteristics were observed when the polarizing plates of examples 1 to 12 and comparative examples 1 to 5 were held at 115 ℃ for 1000 hours and at 85 ℃ and 85% humidity for 1000 hours. As a result, the polarizing plate of the present invention showed no decrease in contrast or polarization degree in the environment of 115 ℃ and 85% RH.

As is clear from the results of examples 1 to 12 and comparative examples 1 to 5, the optical characteristics and durability of the polarizing element and the polarizing plate of the present invention are improved. Therefore, by using the polarizing element or the polarizing plate, a liquid crystal display device and a polarizing lens having excellent polarization characteristics and high durability can be obtained.

[ possibility of Industrial use ]

The present invention can provide a polarizing element, a polarizing plate, an optical member, and the like, which have optical characteristics equivalent to or more excellent than those of the known polarizing element, polarizing plate, optical member, and the like. The polarizing element or the polarizing plate of the present invention can be used for display devices such as liquid crystal projectors, electronic computers, clocks, notebook computers, document processors, liquid crystal televisions, polarizing lenses, polarizing glasses, head-up displays, navigators, organic electroluminescence displays (generally referred to as OLEDs), and indoor and outdoor monitors or displays, and optical devices used for the display devices. A liquid crystal display device including the polarizing element of the present invention or the polarizing plate of the present invention is one of the embodiments of the present invention. In addition, a display device including the polarizing element or the polarizing plate of the present invention as one of the particularly preferable uses of the polarizing plate of the present invention can provide not only high polarization degree, that is, contrast, but also high durability. The durability is to provide a display device which is free from discoloration and reduced in contrast even in an environment of 115 ℃ or 85 ℃ with a relative humidity of 85%. Particularly preferred applications are applicable to regions where not only high contrast but also heat resistance, moist heat resistance, and light resistance are required, such as vehicle displays, liquid crystal projectors, head-up displays, and outdoor displays.