TWI776000B - Achromatic polarizing element, and achromatic polarizing plate and display using the same - Google Patents

Abstract

The Polarizing element of the present invention comprises: an azo compound represented by the formula (1) or a salt thereof, and an azo compound represented by the formula (2) or a salt thereof.

In the formula, Ar₁ represents a phenyl group having a substituent or a naphthyl group having a substituent, Rr₁ to Rr₄ each independently represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms which has a sulfo group, j represents 0 or 1, Xr₁ 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 or a benzoylamino group which may have a substituent;

In the formula, Ag₁ represents a phenyl group having a substituent or a naphthyl group, Bg and Cg are each independently represented by the following formula (3) or formula (4), and either one is represented by the formula (3), Xg₁ 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 or a benzoylamino group which may have a substituent;

In the formula, Rg₁ represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms which has a sulfo group, p₁ represents an integer of 0 to 2;

In the formula, Rg₂ and Rg₃ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms which has a sulfo group.

Description

Achromatic polarizing element, achromatic polarizing plate and display device using the same

The present invention relates to a colorless dye-based polarizing element, a colorless polarizing plate and a display device using the polarizing element.

The polarizing element is generally based on a polyene-based film that is oriented by a polyene-based film produced by a stretch-oriented film of polyvinyl alcohol or its derivatives, dehydrochlorination of a polyvinyl chloride film, or dehydration of a polyvinyl alcohol-based film. It is manufactured by orienting the adsorption of iodine or dichroic dyes. The polarizing plate system obtained by bonding the protective film which consists of triacetate cellulose etc. to this polarizing element via an adhesive agent layer can be used for a liquid crystal display device etc.. Polarizing plates that use iodine as a dichroic dye are called iodine-based polarizing plates, and on the other hand, polarizing plates that use dichroic dyes such as dichroic azo compounds as dichroic dyes are called dye-based polarizing plates polarizer. Among them, dye-based polarizing plates have high heat resistance, high humidity and heat durability, and high stability, and are characterized by high color selectivity due to the blending of pigments. High-grade iodine-based polarizing plates have problems of low transmittance and contrast. Therefore, in addition to maintaining high durability and a variety of colors, a polarizing element with higher transmittance and high polarization characteristics is desired.

Furthermore, even in the case of dye-based polarizers with various color selectivities, conventional polarizers are superimposed so that the absorption axis directions of two polarizers are parallel to each other (hereinafter, also referred to as "parallel position"). When arranged to display white (hereinafter, also referred to as "white display" or "bright display".), there is a problem that white appears yellowish from white. In order to improve the problem of white yellowing, even if the polarizing element is produced to suppress yellowing, the polarizing plate so far has two polarizing elements in a positional relationship in which the absorption axis directions are orthogonal to each other (hereinafter, also referred to as "orthogonal"). When black is displayed in a superimposed arrangement in the manner of "bit" (hereinafter, also referred to as "black display" or "dark display".), there may be a problem that black appears blue. Therefore, a polarizing plate that displays colorless white when white is displayed and black when black is required is required. In particular, it is difficult to obtain a high-quality white polarizing plate during white display, which is commonly referred to as a paper-white polarizing plate.

In order to make the polarizing plate colorless, the transmittance of each wavelength must have a constant value in the parallel position or the orthogonal position regardless of the wavelength, but such a polarizing plate has not been obtained so far.

The reason for the difference in hue between the white display and the black display is that the wavelength dependence of transmittance is different between the parallel position and the orthogonal position, and in particular, the transmittance is not constant over the entire visible light region. Furthermore, dichroism is not constant over the entire visible light region and is one of the factors that make it difficult to realize a colorless polarizer.

Taking an iodine-based polarizing plate as an example, an iodine-based polarizing plate using polyvinyl alcohol (hereinafter, also referred to as "PVA") as a base material and using iodine as a dichroic dye generally has 480 nm and 600 nm as the center. absorption. The absorption at 480 nm is attributed to the complex of polyiodine I ₃ ^- and PVA, and the absorption at 600 nm is attributed to the complex of polyiodine I ₅ ^- and PVA. Regarding the degree of polarization (dichroism) in each wavelength, the degree of polarization (dichroism) obtained from the complex of polyiodine I ₅ ^- and PVA is higher than the degree of polarization (dichroic) obtained from the complex of polyiodine I ₃ ^- and PVA. The resulting degree of polarization (dichroism) is higher. In short, if the transmittance of the orthogonal position is constant in each wavelength, the transmittance of the parallel position will become higher at 600 nm than at 480 nm, which will cause a yellowing phenomenon of white when displaying white. Conversely, if the transmittance of the parallel position is constant, the transmittance of the orthogonal position will be lower at 600 nm than at 480 nm, so when black is displayed, black is colored blue. Since the case where white appears yellow at the time of white display generally gives an impression of progress of deterioration, it is hardly preferable. In addition, when the black display is lacking in blue, since it is not clear black, it gives an impression of lack of luxury. In addition, in the iodine-based polarizing plate, there is no complex based on the wavelength mainly in the vicinity of 550 nm where the luminous factor (also called "visual degree") is high, so it is difficult to control the hue.

In this way, since the degree of polarization (dichroism) of each wavelength is not constant, wavelength dependence of the degree of polarization occurs. In addition, since there are only two dichroic dyes at 480 nm and 600 nm that absorb by the complex obtained by iodine and PVA, the iodine-based polarizing plate composed of iodine and PVA cannot adjust the hue.

A method of improving the hue of an iodine-based polarizing plate is described in Patent Document 1 and Patent Document 2. In Patent Document 1, the neutral coefficient is calculated, and a polarizing plate whose absolute value is 0 to 3 is described. In Patent Document 2, the transmittance of 410 nm to 750 nm is within ±30% of the average value, and in addition to iodine, a polarizing film in which direct dyes, reactive dyes, or acid dyes are added to adjust coloring is described. Moreover, like patent document 3, the technique of a colorless dye-type polarizing plate is also disclosed.

[Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2002-169024

[Patent Document 2] Japanese Patent Application Laid-Open No. 10-133016

[Patent Document 3] WO2014/162635

[Patent Document 4] Japanese Patent Laid-Open No. 8-291259

[Patent Document 5] Japanese Patent Laid-Open No. 2002-275381

[Patent Document 6] WO2015/152026

[Patent Document 7] Japanese Patent Application Laid-Open No. 1-161202

[Patent Document 8] Japanese Patent Application Laid-Open No. 1-172907

[Patent Document 9] Japanese Patent Application Laid-Open No. 1-183602

[Patent Document 10] Japanese Patent Laid-Open No. 1-248105

[Patent Document 11] Japanese Patent Laid-Open No. 1-265205

[Patent Document 12] Japanese Patent Publication No. 7-92531

[Patent Document 13] Japanese Patent Laid-Open No. 2008-065222

[Patent Document 14] Japanese Patent Laid-Open No. 2003-215338

[Patent Document 15] Japanese Patent Application Laid-Open No. 11-218611

[Patent Document 16] Japanese Patent Laid-Open No. 2001-033627

[Patent Document 17] Japanese Patent Laid-Open No. 2004-251962

[Patent Document 18] Japanese Patent Laid-Open No. 8-291259

[Non-patent literature] [Non-Patent Document 1]

Application of functional pigments (published by CMC Corporation, 1st edition, supervised by Masahiro Irie, pp. 98-100)

However, for the polarizing plate of Patent Document 1, it is known from Example 1 that even if the neutral coefficient (Np) is low, the hue system a* value of the parallel position obtained from JIS Z 8729 is -1.67, and the b* value is -1.67. is 3.51, so it appears yellow-green when white is displayed. In addition, the a* value of the hue system of the orthogonal position is 0.69, but the b* value is -3.40, so it becomes a polarizing plate that displays blue in black. In addition, the polarizing film of Patent Document 2 is obtained by using only one polarizing film to measure the a value and b value in the UCS color space with an absolute value of 2 or less, which is not the case of white display when two polarizing films are superimposed. In the hue of the two when displayed in black, a colorless one can appear at the same time. Moreover, the average value of the monomer transmittance of the polarizing film of Patent Document 2 was 31.95% in Example 1 and 31.41% in Example 2, which were relatively low values. As described above, the polarizing film of Patent Document 2 has low transmittance, and therefore does not have sufficient performance in the fields requiring high transmittance and high contrast, especially in the fields of liquid crystal display devices and organic electroluminescence. Furthermore, the polarizing film system of Patent Document 2 uses iodine as the main dichroic dye, so after the durability test, especially, after the humid heat durability test (for example, the environment of 85°C, 85% relative humidity), the color changes greatly, and it is durable. Bad sex.

On the other hand, the dye-based polarizing plate is excellent in durability, but the wavelength dependence is the same as that of the iodine-based polarizing plate in which the parallel position and the orthogonal position are different. There are hardly any azo compounds exhibiting dichroism of the same hue in the parallel position and the orthogonal position, and even if they exist, the dichroism (polarization characteristic) is low. Depending on the type of azo compound with dichroism, there are azo compounds with completely different wavelength dependencies in the orthogonal and parallel positions, such as yellow when white is displayed, and blue when black is displayed. compound. In addition, since the color sensitivity of people will be different depending on the light and dark, even if the color correction of the dye-based polarizing plate is assumed, it is necessary to have an orthogonal position. Up to the color correction suitable for each of the brightness and darkness of the light produced by the control of the polarized light. In each of the parallel position and the orthogonal position, a colorless polarizing plate cannot be achieved unless the transmittance is almost constant at each wavelength and has no wavelength dependence. Furthermore, in order to obtain a polarizing element with high transmittance and high contrast, in addition to satisfying constant transmittance in parallel and orthogonal positions, the polarization degree (dichromatic ratio) of each wavelength must also be high and constant. When one kind of azo compound is applied to the polarizing element, the wavelength dependence of transmittance of each wavelength in the orthogonal position and the parallel position is different, and in order to prepare two or more kinds of azo compounds, each wavelength is constant. When achieving the penetration rate, the penetration rate of the parallel position and the orthogonal position of each type must also be considered, and the relationship between the two color ratios of two or more types must be precisely controlled.

On the other hand, even if the relationship between the transmittance and the dichromatic ratio of each wavelength in the parallel position and the orthogonal position is precisely controlled to make the transmittance constant, it is still impossible to achieve high transmittance and high contrast. That is, the higher the transmittance or the higher the degree of polarization, the more difficult it is to become a colorless polarizer with a high transmittance or a high degree of polarization. It is extremely difficult to obtain an achromatic polarizing plate with high transmittance and/or high contrast, which cannot be achieved by applying only dichroic pigments of the three primary colors of the color. In particular, it is extremely difficult to simultaneously achieve constant transmittance and high dichroism at each wavelength in parallel. Even if the white color is only slightly tinted, high-quality white cannot be expressed. In addition, the brightness of the white system in the bright state is high, and the sensitivity is also high, so it is particularly important. Therefore, as far as polarizing elements are concerned, it is increasingly required to display high-quality paper-like colorless white when displaying white, display colorless black when displaying black, and have a luminous factor corrected monomer transmittance of more than 35%. And polarizing element with high polarization degree. In Patent Document 3, a colorless polarizer is also described in white display and black display, but further performance improvement is desired.

Therefore, the object of the present invention is to provide a high-performance achromatic polarizer to And an achromatic polarizer and a display device using the polarizing element, the achromatic polarizing element has high transmittance and high degree of polarization, and is achromatic in both white display and black display, especially, white display The time series presents a high-quality white.

In order to solve the above-mentioned problems, the inventors of the present invention, as a result of diligent research, found that by preparing the azo compounds of the formula (1) and the formula (2), there is no wavelength dependence in the dichroism, and there is no wavelength dependence in the parallel position and the orthogonal position. They are colorless, and can produce polarizing elements with an unprecedented high degree of polarization. The inventors of the present invention first discovered that even with a high transmittance, wavelength independence in the visible light region can be achieved, and developed a white with high-quality paper-like quality, commonly known as a white with higher polarization that can achieve paper white degree of polarizing element.

That is, the present invention relates to the following.

Invention 1

A polarizing element comprising: an azo compound represented by formula (1) or a salt thereof, and an azo compound represented by formula (2) or a salt thereof,

In the formula, Ar ₁ represents a substituted phenyl group or a substituted naphthyl group, and Rr ₁ to Rr ₄ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, and an alkoxy group having 1 to 4 carbon atoms. , or an alkoxy group with a carbon number of 1 to 4 having a sulfonic acid group, j represents 0 or 1, Xr ₁ represents an amino group that can have a substituent, a phenylamino group that can have a substituent, and a benzene that can have a substituent azo, optionally substituted benzylamino, or optionally substituted benzylamino;

In the formula, Ag ₁ represents a substituted phenyl group or a substituted naphthyl group, Bg and Cg are each independently represented by the following formula (3) or formula (4), and any one of them is represented by the formula (3) As shown, Xg ₁ represents an amino group that may have a substituent, a phenylamino group that may have a substituent, a phenylazo group that may have a substituent, a benzyl group that may have a substituent, or a substituted group the benzylamino group;

In the formula, Rg ₁ represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an alkoxy group having a sulfonic acid group having 1 to 4 carbon atoms, and p ₁ represents 0 to 2 the integer;

In the formula, Rg ₂ and Rg ₃ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an alkoxy group having sulfonic acid group having 1 to 4 carbon atoms.

Invention 2

The polarizing element according to the invention 1, wherein Cg in the above formula (2) is represented by the above formula (3).

Invention 3

The polarizing element according to Invention 1 or 2, wherein the azo compound represented by the above formula (2) or a salt thereof is an azo compound represented by the following formula (5) or a salt thereof,

In the formula, Ag ₂ represents a substituted phenyl group or a substituted naphthyl group, and Rg ₄ and Rg ₅ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group, or a sulfonic acid group. The alkoxy group with 1 to 4 carbon atoms, Xg ₂ represents an amino group that can have a substituent, a phenylamino group that can have a substituent, a phenylazo group that can have a substituent, and a benzyl that can have a substituent In the acyl group or the optionally substituted benzylamino group, p ₂ and p ₃ each independently represent an integer of 0 to 2.

Invention 4

The polarizing element according to the invention 3, wherein p ₂ and p ₃ described in the above formula (5) are 1 or 2, respectively.

Invention 5

The polarizing element according to any one of Inventions 1 to 4, wherein Xr ₁ of the above formula (1) is a phenylamino group which may have a substituent.

The polarizing element according to any one of Inventions 1 to 5, wherein Xg ₁ represented by the above formula (2) is a phenylamino group which may have a substituent.

Invention 7

The polarizing element according to any one of the inventions 1 to 6, further comprising an azo compound represented by the following formula (6) or a salt thereof,

In formula (6), Ay ₁ represents a sulfonic acid group, a carboxyl group, a hydroxyl group, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms, and Ry ₁ to Ry ₄ each independently represent a hydrogen atom, carbon An alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an alkoxy group having a sulfonic acid group having 1 to 4 carbon atoms, and k represents an integer of 1 to 3.

Invention 8

The polarizing element according to any one of Inventions 1 to 7, wherein the transmittance of each wavelength obtained by measuring the transmittance of each wavelength obtained by overlapping two polarizing elements so that their respective absorption axis directions are parallel to each other, The difference between the average transmittance from 420nm to 480nm and the average transmittance from 520nm to 590nm is less than 2.5% in absolute terms, and the difference between the average transmittance from 520nm to 590nm and the average transmittance from 600nm to 640nm in absolute terms The value was calculated as 3.0% or less.

Invention 9

The polarizing element according to any one of Inventions 1 to 8, wherein, according to JIS Z 8781-4:2013, the absolute values of the a* value and the b* value obtained during transmittance measurement using natural light are in The above-mentioned polarizers are all 1.0 or less (-1.0≦a*-s≦1.0, -1.0≦b*-s≦1.0), and the two polarizers are arranged so that their respective absorption axis directions are parallel to each other. In the state of overlapping and arranging, they are all below 2.0 (-2.0≦a*-p≦2.0, -2.0≦b*-p≦2.0); among them, a*-s represents the a* value of the monomer, b* -s represents the b* value in the monomer, a*-p represents the a* value in the parallel position, and b*-p represents the b* value in the parallel position.

Invention 10

The polarizing element according to any one of the inventions 1 to 9, wherein the light-emitting factor correction of the polarizing element has a single transmittance of 35% to 45%, and the two polarizing elements are absorbed by their respective The axes overlap in such a way that they become parallel to each other The average transmittance of each wavelength from 520 nm to 590 nm obtained in the state of the configuration is 28% to 45%.

Invention 11

The polarizing element according to any one of inventions 1 to 10, wherein the transmittance of each wavelength is obtained by arranging the two polarizing elements so that their respective absorption axis directions are arranged to overlap each other so as to be orthogonal to each other. Among them, the difference between the average transmittance from 420nm to 480nm and the average transmittance from 520nm to 590nm is less than 1.0% in absolute value, and the difference between the average transmittance from 520nm to 590nm and the average transmittance from 600nm to 640nm The absolute value is 1.0% or less.

Invention 12

The polarizing element according to any one of Inventions 1 to 10, wherein the orthorhombic transmittance of each wavelength in the wavelength bands of 420 nm to 480 nm, 520 nm to 590 nm, and 600 nm to 640 nm is 1% or less, or The degree of polarization is above 97%.

Invention 13

The polarizing element according to any one of inventions 1 to 10, wherein the two polarizing elements are arranged so as to overlap each other so that their respective absorption axis directions are orthogonal to each other, conforming to JIS Z 8781-4 : In 2013, the absolute values of a* value and b* value obtained by measuring the transmittance of natural light are both below 2.0 (-2.0≦a*-c≦2.0, -2.0≦b*-c≦2.0) ; Among them, a*-c represents the a* value in the orthogonal position, and b*-c represents the b* value in the orthogonal position.

Invention 14

The polarizing element according to any one of Inventions 1 to 13, wherein the polarizing element comprises a polyvinyl alcohol-based resin film as a base material.

Invention 15

A polarizing plate comprising the polarizing element described in any one of claims 1 to 14 of the patent application scope, and a transparent protective layer provided on one side or both sides of the polarizing element.

Invention 16

A display device comprising the polarizing element described in any one of claims 1 to 14 of the patent application scope, or the polarizing plate described in the claim 15 claim scope.

The present invention can provide a high-performance achromatic polarizing element with high transmittance and high degree of polarization, and at the same time showing high-quality white in white display, especially, the polarizing element in white display and black display Both are achromatic, and an achromatic polarizer and a display device using the achromatic polarizer.

In the description of the present case and the scope of the patent application, the case of expressly expressing the free form is excluded, and sometimes only "azo compounds or their salts" are referred to as "azo compounds".

In the description of the present application and the scope of the patent application, "lower" of lower alkyl group, lower alkoxy group, and lower alkylamine group means that the number of carbon atoms is 1 to 4, preferably 1 to 3. In addition, in the present specification and the scope of the patent application, the "substituent group" conveniently includes a hydrogen atom. The term "may have a substituent" also includes a case where it does not have a substituent. For example, "optionally substituted phenyl" includes unsubstituted individual phenyl groups and substituted phenyl groups.

Examples of the "lower (carbon number 1 to 4) aliphatic hydrocarbon group" include straight-chain alkyl groups such as methyl, ethyl, n-propyl, and n-butyl, and branched-chain alkyl groups such as sec-butyl and tert-butyl. , unsaturated hydrocarbon groups such as vinyl, etc.

The "lower (carbon number 1 to 4) alkoxy group" includes, for example, a methoxy group, an ethoxy group, a propoxy group, a n-butoxy group, a 2nd butoxy group, a 3rd butoxy group, and the like.

<Polarizing element>

The polarizing element of the present invention includes the azo compound represented by the above formula (1) or a salt thereof, and the azo compound represented by the above formula (2) or a salt thereof. The polarizing element of the present invention may further optionally include the azo compound represented by the above formula (6), and preferably includes the substrates of the formula (1), the formula (2) and the formula (6).

The above-mentioned base material is preferably a dichroic dye, especially a film made of a hydrophilic polymer capable of adsorbing azo compounds. The hydrophilic polymer is not particularly limited, and examples thereof include polyvinyl alcohol-based resins, amylose-based resins, starch-based resins, cellulose-based resins, and polyacrylate-based resins. From the viewpoints of dyeability, processability, and crosslinking properties of the dichroic dye, polyvinyl alcohol-based resins and derivatives thereof are the most suitable hydrophilic polymers. A polarizing element can be produced by adsorbing an azo compound or its salt on a substrate and applying an orientation treatment such as stretching.

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

In the above formula (1), Ar ₁ represents a substituted phenyl group or a substituted naphthyl group, and Rr ₁ to Rr ₄ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a sulfonic acid group The lower alkoxy group, j represents 0 or 1, Xr ₁ represents an amino group that can have a substituent, a phenylamino group that can have a substituent, a phenylazo group that can have a substituent, and a benzene that can have a substituent A carboxyl group, or a benzylamino group which may have a substituent.

The above-mentioned substituted phenyl group or substituted naphthyl group will be explained. When Ar ₁ is a substituted phenyl group, it preferably has at least one sulfonic acid group or carboxyl group as its substituent. When the phenyl group has two or more substituents, at least one of the substituents is a sulfonic acid group or a carboxyl group, and the other substituents are preferably a sulfonic acid group, a carboxyl group, a lower alkyl group, a lower alkoxy group, a sulfonic acid group Lower alkoxy, nitro, benzyl, amino, acetylamino, or lower alkylamino substituted amino group of acid group, other substituents are more preferably sulfonic acid group, methyl group, ethyl group , methoxy group, ethoxy group, carboxyl group, nitro group, benzyl group, or amine group, particularly preferably sulfonic acid group, methyl group, methoxy group, ethoxy group, benzyl group, or carboxyl group. The above-mentioned lower alkoxy group with sulfonic acid group is preferably a straight-chain alkoxy group, and the substitution position of the sulfonic acid group is preferably an alkoxy terminal, more preferably 3-sulfopropoxy and 4-sulfobutoxy group, but particularly preferred is 3-sulfopropoxy. The number of sulfonic acid groups in the phenyl group is preferably 1 or 2, and the substitution position is not particularly limited, but when the substitution position of the amide group is the 1-position, it is preferably only the 4-position, the 2-position and the 4-position Combinations, and combinations of 3 and 5 digits.

When the above-mentioned Ar ₁ is a naphthyl group with a substituent, the substituent preferably has at least one sulfonic acid group, a hydroxyl group, an alkoxy group with a carbon number of 1 to 4 having a sulfonic acid group, and when it has two or more substituents, At least one of these substituents is a sulfonic acid group, and the other substituents are preferably a sulfonic acid group, a hydroxyl group, a carboxyl group, or a lower alkoxy group having a sulfonic acid group. The lower alkoxy group with a sulfonic acid group is preferably a straight-chain alkoxy group, and the substitution position of the sulfonic acid group is preferably an alkoxy terminal, more preferably 3-sulfopropoxy and 4-sulfobutoxy , but the particularly preferred system is 3-sulfopropoxy. When the number of sulfonic acid groups is 2, the position of the sulfonic acid group on the naphthyl group is when the substitution position of the amide group is the 2-position, preferably the combination of the 4-position and the 8-position, and the combination of the 6-position and the 8-position, A combination of 6-bit and 8-bit is better. When the number of sulfonic acid groups possessed by the naphthyl group is 3, the substitution position of the sulfonic acid group is preferably a combination of the 3-position, the 6-position and the 8-position.

The above Rr ₁ to Rr ₄ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfonic acid group. Rr ₁ to Rr ₄ are preferably each independently a hydrogen atom, a lower alkyl group, or a lower alkoxy group, more preferably a hydrogen atom, a methyl group, or a methoxy group. The lower alkoxy group with a sulfonic acid group is preferably a straight-chain alkoxy group, and the substitution position of the sulfonic acid group is preferably an alkoxy terminal, more preferably 3-sulfopropoxy and 4-sulfobutoxy , but the particularly preferred system is 3-sulfopropoxy.

The above j represents 0 or 1. When j is 0, since it is easy to control the color, the absolute values of the a* value and the b* value obtained by measuring the transmittance in the case of using natural light according to JIS Z 8781-4:2013 are obtained by making the two polarizers respectively Since it is easy to adjust to 2.0 or less in the state which overlaps and arranges so that absorption axis direction may become mutually parallel, it is a preferable form for adjusting a color. When j is 1, since a high degree of polarization is exhibited, it is one of the preferable forms for performance improvement.

The above 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 benzyl group which may have a substituent, or a benzene which may have a substituent Carboxylamido group. The amino group which may have a substituent preferably has one or two substitutions selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfonic acid group, an amino group, and a lower alkylamine group The amine group of the group, more preferably, has one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, an amino group, and a lower alkylamine group amine group. The optionally substituted phenylamino group preferably has one or two selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfonic acid group, an amino group, and a lower alkylamine group A phenylamino group having one substituent, more preferably a phenylamino group having one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfonic acid group, and an amine group . The benzyl group which may have a substituent preferably has one benzyl group selected from the group consisting of a hydrogen atom, a hydroxyl group, a sulfonic acid group, an amino group, and a carboxyethylamino group. The optionally substituted benzylamino group preferably has one benzylamino group selected from the group consisting of a hydrogen atom, a hydroxyl group, an amino group, and a carboxyethylamino group. The optionally substituted phenylazo group preferably has a group selected from the group consisting of a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an amino group and a carboxyethylamino group. 1 to 3 phenylazo groups of the group. Xr ₁ is preferably an amino group which may have a substituent, a benzylamino group which may have a substituent, and a phenylamino group which may have a substituent, more preferably an amino group which may have a substituent, The phenylamino group of the base. The position of the substituent is not particularly limited, but when Xr ₁ is a group having a phenyl group, one of the substituents is particularly preferably at the bonding position indirectly bonded to the naphthalene skeleton represented by the formula (1). The p-position is substituted, and as a specific example, in the case of a phenylamino group, it is preferable to have a substituent at the p-position with respect to the amino group.

As a method for obtaining the azo compound represented by the above formula (1), for example, the methods described in Patent Documents 4 to 6 and the like are mentioned, but not limited thereto.

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

Next, the compound of the above formula (2) will be described.

In the above formula (2), Ag ₁ represents a substituted phenyl group or a substituted naphthyl group. When Ag ₁ is a substituted phenyl group, it preferably has at least one sulfonic acid group or carboxyl group as a substituent. When the phenyl group has two or more substituents, at least one of the substituents is a sulfonic acid group or a carboxyl group, and the other substituents are preferably a sulfonic acid group, a carboxyl group, a lower alkyl group, a lower alkoxy group, or a sulfonic acid group. The lower alkoxy group, nitro group, amino group, acetylamino group, or lower alkylamine group substituted amino group. Other substituents are preferably sulfonic acid group, methyl group, ethyl group, methoxy group, ethoxy group, carboxyl group, nitro group, or amine group, particularly preferably sulfonic acid group, methyl group, methoxy group, ethoxy group , or carboxyl. The lower alkoxy group with a sulfonic acid group is preferably a straight-chain alkoxy group, and the substitution position of the sulfonic acid group is preferably an alkoxy terminal, more preferably 3-sulfopropoxy and 4-sulfobutoxy, especially The preferred system is 3-sulfopropoxy. The number of substituents that the phenyl group has is preferably 1 or 2, and the substitution position is not particularly limited, but when the position of the azo group is the 1-position, it is preferably only the 4-position, a combination of the 2-position and the 4-position, and A combination of 3 and 5 digits. When Ag ₁ is a substituted naphthyl group, it preferably has at least one sulfonic acid group as its substituent. When the naphthyl group has two or more substituents, at least one of the substituents is a sulfonic acid group, a hydroxyl group, an alkoxy group with a carbon number of 1 to 4 having a sulfonic acid group, and the other substituents are preferably a sulfonic acid group , hydroxyl, carboxyl, or lower alkoxy with a sulfonic acid group. The particularly preferred naphthyl group has two or more sulfonic acid groups as substituents. The lower alkoxy group with a sulfonic acid group is preferably a straight-chain alkoxy group, and the substitution position of the sulfonic acid group is preferably an alkoxy terminal, more preferably 3-sulfopropoxy and 4-sulfobutoxy, but Particularly preferred is 3-sulfopropoxy. When the number of sulfonic acid groups contained in the naphthyl group is 2, the substitution position of the sulfonic acid group is the 2-position of the azo group, preferably the combination of the 4-position and the 8-position, and the combination of the 6-position and the 8-position combination, preferably a combination of 6-bit and 8-bit. When the number of sulfonic acid groups possessed by the naphthyl group is 3, the substitution position of the sulfonic acid group is preferably a combination of the 3-position, the 6-position and the 8-position when the substitution position of the azo group is set to the 2-position.

Bg and Cg in the above formula (2) are each independently represented by the above formula (3) or the above formula (4), but any one of Bg and Cg is represented by the above formula (3).

In the above formula (3), Rg ₁ represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfonic acid group, preferably a hydrogen atom, a lower alkyl group, or a lower alkoxy group, More preferably, it is a hydrogen atom, a methyl group, or a methoxy group. Particularly preferred Rg ₁ may be a hydrogen atom or a methoxy group. The lower alkoxy group with a sulfonic acid group is preferably a straight-chain alkoxy group, and the substitution position of the sulfonic acid group is preferably an alkoxy terminal, more preferably 3-sulfopropoxy and 4-sulfobutoxy, Particularly preferred is 3-sulfopropoxy. In formula (3), the azo group substituted on the Ag ₁ side is set to the 1-position, and the substitution position of Rg ₁ is preferably the 2-position or the 3-position, more preferably the 3-position. p ₁ represents an integer of 0 to 2. When it has a sulfonic acid group (p ₁ is 1 or 2), the substitution position of the sulfonic acid group may be the 6-position or the 7-position, preferably the 6-position.

In the above formula (4), Rg ₂ and Rg ₃ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfonic acid group, preferably a hydrogen atom, a lower alkyl group, The lower alkoxy group or the lower alkoxy group having a sulfonic acid group is more preferably a hydrogen atom, a methyl group, a methoxy group, a 3-sulfopropoxy group, or a 4-sulfopropoxy group. The substitution position of Rg ₂ or Rg ₃ is that the azo group substituted on the Ag ₁ side in the above formula (2) is set to the 1-position, and only the 2-position, only the 5-position, the 2-position and the 5-position, the 3-position and the 5 bits, 2 bits and 6 bits, or a combination of 3 bits and 6 bits, but preferably 2 bits only, 5 bits only, 2 bits and 5 bits. In addition, only the 2-position and only the 5-position means that only the 2-position or the 5-position has a substituent other than one hydrogen atom.

Xg ₁ in the above formula (2) 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 benzyl group which may have a substituent or a substituted group. A substituted benzylamino group. Xg ₁ is preferably an amino group which may have a substituent or a phenylamino group which may have a substituent, and more preferably a phenylamino group which may have a substituent. The amino group which may have a substituent preferably has one or two amino groups selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfonic acid group, an amino group, and a lower alkylamine group , and more preferably an amine group having one or two hydrogen atoms, a methyl group, and a sulfonic acid group. The optionally substituted phenylamino group preferably has one or two selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfonic acid group, an amino group, and a lower alkylamine group A phenylamino group having one substituent, more preferably a phenylamino group having one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfonic acid group, and an amine group . The phenylazo group is preferably selected from the group consisting of a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having a carbon number of 1 to 4, an amino group, a hydroxyl group and a carboxyethylamino group 1 to 3 phenylazo groups. The benzyl group which may have a substituent is preferably a benzyl group having one substituent selected from the group consisting of a hydrogen atom, a hydroxyl group, an amino group, and a carboxyethylamino group. The benzylamino group which may have a substituent is preferably a benzylamino group having one substituent selected from the group consisting of a hydrogen atom, a hydroxyl group, an amino group, and a carboxyethylamino group. The position of the substituent is not particularly limited, but when Xg ₁ is a group having a phenyl group, one of the substituents is located at the p-position with respect to the bonding position indirectly bonded to the naphthalene skeleton represented by the formula (2). It is particularly preferable, and when a specific example is a phenylamino group, it is preferable to have a substituent at the p-position with respect to the amino group.

When the azo compound represented by the above formula (2) or a salt thereof is the azo compound represented by the above formula (5) or a salt thereof, in particular, it is preferable to improve performance.

In the above formula (5), Ag ₂ represents the same meaning as Ag ₁ in the formula (2). Rg ₄ and Rg ₅ each independently represent the same meaning as Rg ₁ in formula (3). Xg ₂ has the same meaning as Xg ₁ in formula (2). p ₂ and p ₃ each independently represent the same meaning as p ₁ in the formula (2). In particular, it is preferable that p ₂ and p ₃ are independently 1 or 2 because the polarization characteristics are improved.

In the above-mentioned polarizing element, the content of the azo compound represented by the above formula (2) or its salt is preferably 0.01 to 5000 parts by mass relative to 100 parts by mass of the content of the azo compound of the above formula (1), more It is preferably 0.1 to 3000 parts by mass, more preferably 10 to 1000 parts by mass, still more preferably 40 to 400 parts by mass.

The azo compound represented by the above formula (2) or a salt thereof can be synthesized by, for example, the methods described in Patent Documents 7 to 12, but not limited thereto.

Specific examples of the azo compound represented by the above formula (2) include C.I. Direct Blue 34, C.I. Direct Blue 69, C.I. Direct Blue 70, C.I. Direct Blue 71, C.I. Direct Blue 72, C.I. Direct Blue 75, C.I. Direct Blue 78. C.I. Direct Blue 81, C.I. Direct Blue 82, C.I. Direct Blue 83, C.I. Direct Blue 186, C.I. Direct Blue 258, Benzochrome Fast Blue FG (C.I.34225), Benzo Fast Blue BN (C.I.34120), C.I. Direct Azo compounds such as green 51.

Hereinafter, specific examples of the azo compound represented by the above formula (2) are shown as free acids.

The above-mentioned polarizing element has a higher transmittance and a higher degree of polarization than the conventional achromatic polarizing plate by containing the combination of the azo compound represented by the above-mentioned formula (1) and the above-mentioned formula (2). In white display, high quality like paper white, commonly known as paper white, can still be achieved. In black display, colorless black can still be achieved, especially high-level clear black, and dye-based polarizers with higher quality than the previous ones can be achieved. Polarizer for higher contrast.

In order to further improve the performance, the polarizing element preferably contains the azo compound represented by the above formula (6) in addition to the azo compound represented by the formula (1) and the formula (2).

In the above formula (6), Ay ₁ is a sulfonic acid group, a carboxyl group, a hydroxyl group, a lower alkyl group, or a lower alkoxy group, preferably a sulfonic acid group or a carboxyl group. Ry ₁ to Ry ₄ are each independently a hydrogen atom, a sulfonic acid group, a lower alkyl group, a lower alkoxy group, a lower alkoxy group having a sulfonic acid group, preferably a hydrogen atom, a sulfonic acid group, a lower alkyl group, a lower The alkoxy group is more preferably a hydrogen atom, a methyl group, or a methoxy group. k represents an integer from 1 to 3.

In the above polarizing element, the azo compound represented by the above formula (6) or a salt thereof The content is preferably 0.01 to 300 parts by mass, more preferably 0.1 to 200 parts by mass, and even more preferably 30 to 200 parts by mass, relative to 100 parts by mass of the azo compound of the formula (1).

The azo compound represented by the above formula (6) particularly affects the transmittance of 400 to 500 nm. In the polarizing element, the transmittance and the degree of polarization (dichroism) on the short wavelength side of 400 to 500 nm have an influence on the removal of bluing during black display or the yellowing of white during white display. Although the azo compound represented by the formula (6) suppresses the decrease in the transmittance on the short wavelength side in the parallel position of the polarizing element, it can improve the polarization characteristics (dichroism) of 400 to 500 nm, and can further reduce the time of white display. The removal of blue when yellowing and black are displayed. The polarizing element further contains the azo compound represented by the formula (6), the transmittance of the monomer after the luminous factor correction is in the range of 35 to 66%, the monomer is more colorless, and it appears when white is displayed. The higher quality is as white as paper, and moreover, it is better because the degree of polarization is increased.

The azo compound represented by the formula (6) or a salt thereof can be synthesized by the method described in, for example, WO2007/138980, but a commercially available one can also be obtained.

Specific examples of the azo compound represented by the formula (6) include, for example, C.I. direct yellow 4, C.I. direct yellow 12, C.I. direct yellow 72, and C.I. direct orange 39, and compounds having a stilbene structure described in WO2007/138980 and the like. Azo compounds and the like, but not limited to these.

More specific examples of the azo compound represented by the formula (6) are as follows. In addition, compound examples are shown in the form of a free acid.

The azo compounds represented by the above formula (1), formula (2) and formula (6) may be in a free form or in a salt form, respectively. Salts can be alkali metal salts such as lithium salts, sodium salts, and potassium salts, or organic salts such as ammonium salts, alkylamine salts, and the like. The salt is preferably a sodium salt.

The said polarizing element contains the azo compound represented by Formula (1) and Formula (2), and may further contain the azo compound represented by Formula (6) optionally. The above-mentioned polarizing element can have properties such as the a* value and b* value of chromaticity in the preferred range described later, the single transmittance after luminous factor correction, and the average transmittance in a specific wavelength band. For example, in the transmittance of each wavelength of the polarizing element alone, the transmittance can be made constant. Furthermore, in the parallel position of each wavelength, the transmittance can be made constant, that is, no color can be provided in the hue of the parallel position when the absorption axes of the two polarizers are parallel. Furthermore, in the orthogonal position, the transmittance of each wavelength can be made constant at the same time, that is, achromatic color can be provided in the color phase of the orthogonal position when the absorption axes of the two polarizers are orthogonal. hue. Depend on Therefore, because the polarizing element of the present application contains formulas (1) and (2), and optionally contains the azo compound represented by formula (6), not only high transmittance but also high contrast, that is, high polarization degree can be provided. polarizing element, and can provide polarizing element with achromatic hue.

The mixing ratio of the above-mentioned azo compound in the above-mentioned polarizing element is further adjusted so that the content of each of the above-mentioned azo compounds is suitable so that the transmittance and the chromaticity are in the preferred ranges described later. The performance of the polarizing element will not only change due to the blending ratio of each azo compound in the polarizing element, but also the swelling degree or elongation ratio of the substrate that adsorbs the azo compound, dyeing time, dyeing temperature, pH during dyeing, salt the influence of various factors. Therefore, the compounding ratio of each azo compound can be determined according to the swelling degree of the substrate, the temperature, time, pH, type of salt, concentration of salt, and even extension ratio during dyeing.

(Transmittance after luminous factor correction)

The transmittance after correction of the luminous factor mentioned above is the transmittance corrected by the luminous factor of the human eye obtained according to JIS Z 8722:2009. In order to correct the measurement of the transmittance of each wavelength used, a C light source (2-degree field of view) can be used for the measurement sample (such as a polarizing element or a polarizing plate) and the spectrum can be measured every 5 nm or 10 nm for each wavelength from 400 to 700 nm The transmittance was obtained by correcting it as a luminous factor according to JIS Z 8722:2009. The transmittance after the correction of the luminous factor is: the transmittance of the single unit after the luminous factor correction of the polarizing element or polarizing plate when measuring the single body; two polarizing elements or polarizing plates will be used and their absorption axes will be The transmittance of parallel position is corrected to the transmittance of the light-emitting factor when the light-emitting factor is corrected; the transmittance when two polarizers or polarizers are used and their absorption axes are perpendicular to each other is corrected to the light-emitting factor Orthogonal transmittance after luminous factor correction.

(I) The difference between the average transmittances of the two wavelength bands

It is preferable that the difference of the average transmittance of the said polarizing element between specific wavelength bands is a predetermined value or less. The average transmittance is the average of the transmittances of each wavelength in a specific wavelength band.

The wavelength bands of 420 nm to 480 nm, 520 nm to 590 nm, and 600 nm to 640 nm are based on the main wavelength bands of the color matching function used for calculation when displaying colors in JIS Z 8781-4:2013. Specifically, in the XYZ color matching function according to JIS Z 8701 of JIS Z 8781-4:2013, x (λ) with a maximum value of 600 nm, y (λ) with a maximum value of 550 nm, and a maximum value of 455 nm. When the respective maximum value of z(λ) of the value is set to 100, the respective wavelengths showing a value of 20 or more are the respective wavelength bands of 420 nm to 480 nm, 520 nm to 590 nm, and 600 nm to 640 nm.

The transmittance obtained by measuring two polarizers at each wavelength in a state where the absorption axis directions are parallel to each other is also called the "parallel transmittance" of each wavelength. In addition, the average transmittance of each wavelength from ○ nm to Δnm is also referred to as "AT _○-Δ ". Regarding the parallel position transmittance of each wavelength of the polarizing element of the present invention, the absolute value of the difference between AT _420-480 and AT _520-590 is preferably 2.5% or less, more preferably 1.8% or less, still more preferably 1.5% or less, and 1.0% or less for the best-in-class system. Furthermore, regarding the parallel position transmittance of each wavelength, the difference between AT _520-590 and AT _600-640 is preferably 3.0% or less in absolute value, more preferably 2.0% or less, and still more preferably 1.5% or less, and 1.0% or less for the best-in-class system. Such a polarizing element can display high-quality paper-like white in the parallel position.

The transmittance obtained by measuring two polarizers at each wavelength in a state where they are arranged so that the absorption axis directions are orthogonal to each other (in black display or in dark display) is also referred to as "orthogonal transmission for each wavelength". Rate". Regarding the orthogonal transmittance of each wavelength of the polarizing element of the present invention, the difference between AT _420-480 and AT _520-590 is preferably 1.0% or less in absolute value _, and AT _520-590 and AT _600-640 The difference is 1.0% or less in absolute terms. In this way, the polarizing element can display colorless black in the orthogonal position. Furthermore, regarding the orthogonal position transmittance of each wavelength, the difference between AT _420-480 and AT _520-590 in absolute terms is preferably 0.6% or less, more preferably 0.3% or less, and more preferably 0.1% the following. Regarding the transmittance of the orthogonal position, the difference between AT _520-590 and AT _600-640 in absolute terms is preferably 1.0% or less, more preferably 0.6% or less, more preferably 0.3% or less, and particularly good is 0.1 %.

Furthermore, when the average transmittance in the above wavelength bands 420nm to 480nm, 520nm to 590nm, and 600nm to 640nm is adjusted as described above, the wavelength bands of 380nm to 420nm, 480nm to 520nm, and 640nm to 780nm The respective average transmittances of single transmittance, parallel transmittance, and orthogonal transmittance have little effect on the hue of the polarizing element, but it is still better to do a certain degree of adjustment. . Regarding the monomer transmittance of each wavelength, the difference between AT _380-420 and AT _420-480 is preferably 15% or less, and the difference _between AT 480-520 and AT _420-480 is 15% or less, AT _480-520 The difference with AT _520-590 is less than 15%, and the difference between AT _640-780 and AT _600-640 is less than 20%.

(II) The value of the transmittance of the monomer after the correction of the luminous factor

The above-mentioned polarizing element preferably has a single transmittance of 35% to 66% after the luminous factor correction. The transmittance of the monomer after the correction of the luminous factor is the transmittance of the luminous factor corrected according to JIS Z 8722:2009 for one measurement sample (eg, polarizing element or polarizing plate). As far as the performance of polarizers is concerned, although they are looking for a higher transmittance, if the transmittance of a single unit after the luminous factor correction is 35% to 60%, even if it is used in a display device, it can be used without any sense of incongruity. Appears bright. The higher the transmittance, the lower the degree of polarization. Therefore, from the viewpoint of balance with the degree of polarization, the transmittance of the monomer after luminous factor correction is preferably 37% to 50%, more preferably 38% to 50%. 45%. If the transmittance of the monomer after the correction of the luminous factor exceeds 65%, the degree of polarization will decrease, but seek the bright transmittance of the polarizing element, Or specific polarization performance and contrast ratio, the transmittance of monomer after luminous factor correction can exceed 65%.

(III) Average transmittance in specific wavelength band

The polarizing element is preferably one whose AT _520-590 measured at the parallel position is 25% to 50%. When such a polarizing element is provided in a display device, it can be set as a bright and clear display device with high brightness. The transmittance of the wavelength band from 520 nm to 590 nm is based on one of the main wavelength bands of the color matching function used in the calculation when displaying colors in JIS Z 8781-4:2013. In particular, each wavelength band from 520 nm to 590 nm is the wavelength band with the highest luminous factor according to the color matching function, and the transmittance in this range can be close to the transmittance confirmed visually. Therefore, it is extremely important to adjust the transmittance in the wavelength band from 520 nm to 590 nm. The AT _520-590 measured in parallel is more preferably 28% to 45%, and more preferably 30% to 40%. Furthermore, the polarization degree of the polarizing element at this time may be 80% to 100%, but preferably 90% to 100%, more preferably 97% to 100%, still more preferably 99% or more, and particularly preferably 99.5%. %above. The higher the degree of polarization is better, but in the relationship between the degree of polarization and the transmittance, it can be adjusted to the appropriate transmittance and degree of polarization according to the difference between the emphasis on brightness or the degree of polarization (or contrast).

(chromaticity a* value and b* value)

The chromaticity a* value and b* value are values obtained by measuring the transmittance of natural light according to JIS Z 8781-4:2013. The display method of object color specified in JIS Z 8781-4:2013 is equivalent to the display method of object color specified by the International Commission on Illumination (abbreviation: CIE). The measurement of chromaticity a* value and b* value is performed by irradiating natural light to a measurement sample (for example, a polarizing element or a polarizing plate). In the following, the chromaticity a* value and b* value obtained for one measurement sample are a*-s and b*-s, and the absorption axis directions of two measurement samples are parallel to each other. The chromaticity a* value and b* value obtained in the state of the pattern arrangement (in the case of white display) are expressed as a*-p and b*-p, for The chromaticity a* value and b* value obtained in the state where the absorption axis directions of the two measurement samples are arranged so as to be orthogonal to each other (when displayed in black) are expressed as a*-c and b*-c.

It is preferable that the absolute values of a*-s and b*-s of the above-mentioned polarizing element are 1.0 or less, respectively, and the absolute values of a*-p and b*-p are preferably 2.0 or less, respectively. Such a polarizing element has a neutral color alone, and can display high-quality white when displaying white. The absolute value of a*-p and b*-p of the polarizing element is preferably 1.5 or less, and more preferably 1.0 or less. Furthermore, as for the polarizing element, the absolute values of a*-c and b*-c are preferably 2.0 or less, respectively, more preferably 1.0 or less. Such a polarizing element can display colorless black when black is displayed. Even if the absolute value of the chromaticity a* value and the b* value only has a difference of 0.5, a person can perceive a difference in color, and sometimes a large difference in color can be perceived depending on the person. Therefore, in the polarizing element, it is extremely important to control these values. In particular, when the absolute values of a*-p, b*-p, a*-c, and b*-c are each less than or equal to 1.0, it is almost impossible to recognize the white when displaying white and the black when displaying black. color, a good polarizer can be obtained. Achromaticity can be achieved in the parallel position, that is, high-quality white like paper, and a colorless and high-quality clear black can be realized in the orthogonal position. However, the influence of the hue imparted to black by the display device is not limited to this. Originally, in a state of no light (darkness), even if there is a hue, black will be seen. Therefore, when the degree of polarization is high, that is, when the transmittance in the orthogonal position is low, even if the absolute values of a*-c and b*-c are not 2.0 or less, respectively, the polarizer can impart black color. As a result of research by the present inventors, it was found that when the orthorhombic transmittance of each wavelength in the wavelength bands of 420 nm to 480 nm, 520 nm to 590 nm, and 600 nm to 640 nm is less than 1% or the degree of polarization is about 97% or more, regardless of a* What is the absolute value of -c and b*-c, both can provide black visually, so it is better. In the wavelength bands of 420nm to 480nm, 520nm to 590nm, and 600nm to 640nm, the orthogonal bit transmittance is less than 0.6% or the degree of polarization is more than 98%, because it can visually provide black, so it is better, It is particularly preferred when the orthogonal position transmittance of each wavelength is 0.3% or less or the polarization degree is 99% or more.

From the above-mentioned matters, when two polarizers are arranged so that the absorption axis directions are perpendicular to each other, a preferable method for providing the color of black is achieved by satisfying any one of 1) to 3) below.

1) The transmittance of each wavelength (hereinafter, also referred to as "positive" for each wavelength) obtained by measuring the transmittance of each wavelength obtained by measuring two polarizers in a state where the absorption axis directions are orthogonal to each other (in black display or in dark display) Intersection penetration rate"), the difference between AT _420-480 and AT _520-590 is 1.0% or less in absolute value, and the difference between AT _520-590 and AT _600-640 is 1.0% or less in absolute value

2) The absolute values of a*-c and b*-c are respectively 2.0 or less

3) Orthogonal transmittance at each wavelength of 420 nm to 480 nm, 520 nm to 590 nm, and 600 nm to 640 nm in the wavelength bands is less than 1% or the degree of polarization is about 97% or more.

The polarizing element of the present invention has high contrast ratio and high transmittance, and has colorlessness and high polarization degree in a single body. Furthermore, the polarizing element of the present invention can display high quality like paper white (paper white) when displaying white, and can display colorless black when displaying black, especially clear black with a high-level sense. There is still no polarizing element with such high transmittance and achromaticity. The polarizing element of the present invention further has high durability, especially, durability against high temperature and high humidity.

In addition, compared with the commonly used iodine-based polarizing plate or Patent Document 3, the polarizing element of the present invention absorbs less light with a wavelength of 700 nm or more, so even if it is irradiated with light such as sunlight, it has the so-called less heat generation. advantage. For example, when a liquid crystal display is used outdoors or the like, sunlight is irradiated on the liquid crystal display, and as a result, the polarizing element is also irradiated. The solar system also has light with a wavelength of 700 nm or more, including near-infrared rays with a heating effect. For example, using The polarizing element of the azo compound described in Example 3 of JP-A No. 02-061988 absorbs near-infrared light with a wavelength of around 700 nm, and thus generates a little heat, but the polarizing element of the present invention absorbs very little near-infrared light. , so even if it is exposed to sunlight outdoors, there is little heat generation. The polarizing element of the present invention is excellent in that there is little deterioration due to less heat generation.

<Production method of polarizing element>

Hereinafter, the production method of a specific polarizing element will be described by taking as an example a case where a base material made of a polyvinyl alcohol-based resin adsorbs an azo compound and is produced. In addition, the manufacturing method of the polarizing element of this invention is not limited to the following manufacturing method.

(Preparation of embryonic membrane)

The embryonic membrane system can be produced by producing a polyvinyl alcohol-based resin film. The polyvinyl alcohol-based resin is not particularly limited, and a commercially available one may be used, or one synthesized by a known method may be used. The polyvinyl alcohol-based resin can be obtained, for example, by saponifying a polyvinyl acetate-based resin. In addition to polyvinyl acetate which is a homopolymer of vinyl acetate, the polyvinyl acetate-based resin can also be exemplified by a copolymer of vinyl acetate and other monomers which can be copolymerized therewith. Examples of other monomers copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The degree of saponification of the polyvinyl alcohol-based resin is usually about 85 to 100 mol%, more preferably 95 mol% or more. The polyvinyl alcohol-based resin can be further modified, and for example, polyvinyl acetal modified with aldehydes, polyvinyl acetal, or the like can also be used. The degree of polymerization of the polyvinyl alcohol-based resin refers to the viscosity-average degree of polymerization, which can be obtained by a known method in the technical field, and is usually about 1,000 to 10,000, more preferably about 1,500 to 6,000.

The method of producing the polyvinyl alcohol-based resin film described above is not particularly limited, and a film can be formed by a known method. In this case, the polyvinyl alcohol-based resin film system may contain glycerin, ethylene glycol, propylene glycol, low Molecular weight polyethylene glycol etc. as plasticizer. The amount of the plasticizer is preferably 5 to 20% by mass, more preferably 8 to 15% by mass in the total amount of the film. The membrane thickness of the embryonic membrane is not particularly limited, for example, about 5 μm to 150 μm, preferably about 10 μm to 100 μm.

(swelling step)

The embryo membrane obtained by the above is subjected to swelling treatment. The swelling treatment is preferably performed by immersing the embryo membrane in a solution of 20 to 50° C. for 30 seconds to 10 minutes. The solution is preferably water. The stretching ratio is preferably adjusted to 1.00 to 1.50 times, more preferably 1.10 to 1.35 times. In order to shorten the manufacturing time of the polarizing element, since the embryo membrane will also swell during the dyeing process described later, the swelling process can also be omitted.

(Dyeing step)

In the dyeing step, the resin film obtained by the swelling treatment of the embryo film adsorbs and impregnates the azo compound. When the swelling step is omitted, the swelling treatment of the embryonic membrane can be performed simultaneously with the dyeing step. Since the treatment of adsorbing and impregnating the azo compound is a step of coloring the resin film, it is regarded as a coloring step.

As the azo compound used in the dyeing step, a mixture of the azo compounds represented by the formula (1) and the formula (2) or a salt thereof is used. Further, the azo compound represented by the formula (6) or a salt thereof is optionally used. Furthermore, the azo compound of the dichroic dye exemplified in Non-Patent Document 1 and the like can be arbitrarily used to adjust the color to the extent that the performance of the polarizing element of the present application is not impaired. These azo compounds can also be used in the form of free acids and salts of the compounds. Such salts are, for example, alkali metal salts such as lithium salts, sodium salts, and potassium salts, or organic salts such as ammonium salts and alkylamine salts, and are preferably sodium salts.

The dyeing step is not particularly limited as long as it is a method of adsorbing and impregnating the pigment into the resin film, and it is preferably performed by, for example, immersing the resin film in the dyeing solution, or can also be performed by applying the dyeing solution to the resin film. Each azo compound in the dyeing solution can be, for example, 0.001 to 10 Adjust within the range of mass %.

The temperature of the solution in this step is preferably 5 to 60°C, more preferably 20 to 50°C, and particularly preferably 35 to 50°C. The time of immersion in the solution can be adjusted appropriately, but is preferably adjusted to 30 seconds to 20 minutes, more preferably 1 to 10 minutes.

In addition to the azo compound, the dyeing solution can also contain dyeing auxiliaries as required. As a dyeing assistant, sodium carbonate, sodium bicarbonate, sodium chloride, sodium sulfate, anhydrous sodium sulfate, sodium tripolyphosphate, etc. are mentioned, for example. The content of dyeing auxiliaries can be adjusted at any concentration according to the time and temperature required for the dyeability of the dye, but the respective content in the dyeing solution is preferably 0.01 to 5% by mass, more preferably 0.1 to 2% by mass good.

(washing step 1)

After the dyeing step, a washing step (hereinafter, also referred to as "washing step 1") may be performed before proceeding to the subsequent steps. The dyeing and cleaning step 1 is a step of washing the dyeing solution adhering to the surface of the resin film in the dyeing step. By performing the cleaning step 1, the migration of the dye into the subsequent treatment solution can be suppressed. In the cleaning step 1, water is generally used as a cleaning liquid. The cleaning method is preferably immersion in a cleaning solution, but the cleaning can also be performed by applying the cleaning solution to the resin film. The washing time is not particularly limited, but is preferably 1 to 300 seconds, more preferably 1 to 60 seconds. The temperature of the cleaning solution in the cleaning step 1 must be a temperature at which the material constituting the resin film (for example, a hydrophilic polymer, in this case a polyvinyl alcohol-based resin) does not dissolve. Generally, it is cleaned at 5 to 40 °C. However, even without the step of cleaning step 1, there is no problem in performance, so the cleaning step can be omitted.

(step containing cross-linking agent and/or water repellent)

After the dyeing step or the washing step 1, a step containing a crosslinking agent and/or a water repellant may be performed. The method of containing the crosslinking agent and/or the water repellent in the resin film is preferably immersion in the treatment solution, but it is also possible to The treatment solution is applied or applied to the resin film. The treatment solution contains at least one of a crosslinking agent and/or a water repellent, and a solvent. The temperature of the treatment solution in this step is preferably 5 to 70°C, more preferably 5 to 50°C. The treatment time in this step is preferably 30 seconds to 6 minutes, more preferably 1 to 5 minutes.

As the cross-linking agent, boron compounds such as boric acid, borax, or ammonium borate; polyaldehydes such as glyoxal and glutaraldehyde; polyisocyanate-based compounds such as biuret type, trimeric isocyanate type or block type; titanyl sulfate Other titanium compounds such as ethylene glycol glycidyl ether, polyamide epichlorohydrin, etc. can be used. Water repellents include, for example, peroxysuccinic acid, ammonium persulfate, calcium perchlorate, phenyl ethyl ether, ethylene glycol diglycidyl ether, glycerol diglycidyl ether, ammonium chloride or magnesium chloride, etc. The best system uses boric acid. The solvent used for the crosslinking agent and/or the waterproofing agent is preferably water, but it is not limited. The concentration of the crosslinking agent and/or the water repellent can be appropriately determined according to the type by those with ordinary knowledge in the technical field to which the invention pertains, but if boric acid is used as an example, the concentration in the treatment solution is 0.1 to 6.0 mass % is preferred, more preferably 1.0 to 4.0 mass %. However, it is not necessary to contain a cross-linking agent and/or a water-repellent agent. If the time is to be shortened and the cross-linking treatment or the water-repellent treatment is unnecessary, this treatment step can be omitted.

(extension step)

After the dyeing step, the washing step 1, or the step containing a crosslinking agent and/or a water repellant, an extension step is performed. The stretching step is performed by uniaxially stretching the resin film. The stretching method may be either a wet stretching method or a dry stretching method. The extension ratio is preferably more than 3 times, more preferably 4 to 8 times, and particularly preferably 5 to 7 times.

In the wet stretching method, the resin film is preferably stretched in water, a water-soluble organic solvent, or a mixed solution thereof. Preferably, it is immersed in at least one cross-linking agent and/or waterproofing agent in the solution, while carrying out extension treatment. The cross-linking agent and the water-repellent can be used in the same manner as above in the step containing the cross-linking agent and/or the water-repellent. The concentration in the solution of the crosslinking agent and/or the water repellent in the extension step is, for example, preferably 0.5 to 15% by mass, more preferably 2.0 to 8.0% by mass. The extension temperature is preferably 40 to 60°C, more preferably 45 to 58°C. The extension time is usually 30 seconds to 20 minutes, but preferably 2 to 5 minutes. The wet stretching step can be performed by one-stage stretching, but can also be performed by two or more multi-stage stretching.

In the dry stretching method, when the stretching heating medium is an air medium, the temperature of the air medium is preferably from normal temperature to 180° C. to stretch the resin film. In addition, the humidity is preferably set in an environment of 20 to 95% RH. Although the heating method includes, for example, a roll zone stretching method, a roll heating stretching method, a pressure stretching method, and an infrared heating stretching method, the stretching method is not limited thereto. The extending step may be extended in one stage, but may be carried out by extending in two or more stages.

(washing step 2)

After the stretching step, the crosslinking agent and/or water repellent may be precipitated on the surface of the resin film, or foreign matter may be adsorbed, so the cleaning step (hereinafter, also referred to as the "cleaning step") for cleaning the surface of the resin film can be performed. 2"). The cleaning time is preferably 1 second to 5 minutes. As a cleaning method, the resin film is preferably immersed in a cleaning solution, but may be cleaned by applying or coating the solution to the resin film. The cleaning solution is preferably water. The washing process may be performed in one stage, or a multi-stage process in two or more stages may be performed. The temperature of the solution in the cleaning step is not particularly limited, but is usually 5 to 50°C, preferably 10 to 40°C.

In addition to water, the treatment liquid or its solvent used in the treatment step up to this point includes, for example, dimethylsulfoxide, N-methylpyrrolidone, methanol, ethanol, propanol, isopropanol, glycerin, and ethylene glycol. , propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, alcohols such as trimethylolpropane, amines such as ethylenediamine and diethylenetriamine, etc., but not limited to these. The best system for the treatment liquid or its solvent water. Moreover, these process liquids or its solvent system may be used individually by 1 type, and may use a mixture of 2 or more types.

(drying step)

After the stretching step or the cleaning step 2, a drying step of the resin film is performed. The drying treatment system can be carried out by natural drying, but in order to further improve drying efficiency, it can be carried out by removing moisture on the surface with roll compression, air knife, or suction roll, etc., and/or can also be dried by blowing air. conduct. The drying treatment temperature is preferably carried out at 20 to 100°C, and more preferably at 60 to 100°C. The drying treatment time is, for example, 30 seconds to 20 minutes, but preferably 5 to 10 minutes.

In the manufacturing method of the polarizing element, the swelling degree of the substrate in the swelling step, the mixing ratio of each azo compound in the dyeing step, the temperature, pH of the dyeing solution, sodium chloride or mirabilite, sodium tripolyphosphate and other salts The type of , its concentration, and the dyeing time, and the stretching ratio in the stretching step are preferably adjusted so that the polarizing element satisfies at least one of the following conditions (i) to (v) ^- , more preferably (vi) and (vii) conditions.

For (i) parallel position penetration, the absolute value of the difference between AT _420-480 and AT _520-590 was 2.5 or less, and the absolute value of the difference between AT _520-590 and AT _600-640 was 2.0 or less.

(ii) For orthogonal bit penetration, the absolute value of the difference between AT _420-480 and AT _520-590 is 1.0 or less, and the absolute value of the difference between AT _520-590 and AT _600-640 is 1.0 or less.

(iii) The transmittance of the monomer after luminous factor correction is 35% to 45%.

(iv) The absolute values of the a* value and the b* value are both 1.0 or less in the polarizer alone, and 2.0 or less in the parallel position.

(v) The absolute values of the a* value and the b* value measured by the orthogonal position are both 2 or less.

(vi) Parallel bit transmittance for each wavelength, 28 to 45% for AT _520-590 .

(vii) The difference _between AT _380-420 and AT _420-480 is less than 15% in the single transmittance of each wavelength or the orthogonal position transmittance of each wavelength, AT 480-520 and AT _420-480 The difference is 15% or less, the difference between AT _480-520 and AT _520-590 is 15% or less, and/or the difference between AT _640-780 and AT _600-640 is 20% or less.

By the above method, a polarizing element can be produced which includes at least a combination of the azo compounds represented by the formula (1) and the formula (2), or an azo compound that optionally includes the azo compound represented by the formula (6). combination. In this way, although the polarizing element has higher transmittance and higher polarization degree than the conventional polarizing element, when two polarizing elements are stacked and arranged in such a way that the absorption axis directions are parallel, high-quality paper-like white can be displayed. And the monomer has a neutral color (neutral gray) hue. In addition, when two polarizers are superimposed and arranged so that the absorption axis directions are perpendicular to each other, a colorless black with a sense of luxury is displayed. In addition, the polarizing element has high durability against high temperature and high humidity.

<Polarizer>

The polarizing plate of the present invention includes a polarizing element and a transparent protective layer provided on one side or both sides of the polarizing element. The transparent protective layer is provided for the purpose of improving the water resistance of the polarizing element or the handling properties.

The above-mentioned transparent protective layer is a protective film formed by using a transparent substance. The protective film is a film having a layer shape that can maintain the shape of the polarizing element, preferably a plastic having excellent transparency, mechanical strength, thermal stability, and moisture shielding properties. A layer equivalent to this can be formed to provide the same function. Examples of plastics constituting the protective film include polyester-based resins, acetate-based resins, polyether-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, and polyenes. Thermoplastic resins such as hydrocarbon-based resins and acrylic resins, thermosetting resins such as acrylic-based, urethane-based, acrylic-urethane-based, epoxy-based, and polysiloxane-based resins, or UV-curable resins, etc. Among them, polyolefin-based resins include, for example, amorphous polyolefin-based resins, resins having norbornene-based monomers or polymerized units of cyclic polyolefins such as polycyclic norbornene-based monomers . Generally speaking, it is better to choose a protective film that does not hinder the performance of the polarizing element after laminating the protective film, such a protective film is particularly preferably a triacetyl cellulose (TAC) composed of a cellulose acetate resin. and norbornene. Moreover, as long as the effect of the present invention is not impaired, the protective film may be subjected to hard coating treatment, anti-reflection treatment, anti-sticking or diffusion, anti-glare, or the like for the purpose of treatment. The thickness of the transparent protective layer is usually 10 to 200 μm.

The polarizing plate is preferably between the transparent protective layer and the polarizing element, and further includes an adhesive layer for bonding the transparent protective layer and the polarizing element. The adhesive system constituting the adhesive layer is not particularly limited, and examples thereof include polyvinyl alcohol-based adhesives, urethane emulsion-based adhesives, acrylic-based adhesives, and polyester-isocyanate-based adhesives. Alcohol-based adhesives are suitable. The polyvinyl alcohol-based adhesive includes, for example, Gohsenol NH-26 (manufactured by Nippon Synthetic Co., Ltd.), Exceval RS-2117 (manufactured by Kuraray Co., Ltd.), and the like, but is not limited thereto. A crosslinking agent and/or a waterproofing agent can be added to the adhesive. The polyvinyl alcohol-based adhesive is preferably a maleic anhydride-isobutylene copolymer, and an adhesive mixed with a cross-linking agent can be used as needed. Maleic anhydride-isobutylene copolymers include, for example, Isobam #18 (manufactured by Kuraray), Isobam #04 (manufactured by Kuraray), ammonia-modified Isobam #104 (manufactured by Kuraray), and ammonia-modified Isobam #110 (manufactured by Kuraray). ), imidized Isobam #304 (manufactured by Kuraray), and imidized Isobam #310 (manufactured by Kuraray). In this case, a water-soluble polyvalent epoxy compound can be used as the crosslinking agent. Examples of the water-soluble polyvalent epoxy compound include Denacol EX-521 (manufactured by Nagase Chemtex) and Tetrad-C (Mitsui Gas). System Chemical Co., Ltd.) and so on. Moreover, well-known adhesive agents, such as a urethane type, an acrylic type, and an epoxy type, can also be used for the adhesive agent other than a polyvinyl alcohol-type resin. In particular, it is preferable to use polyvinyl alcohol modified with an acetylacetate group, and moreover, it is preferable to use polyvalent aldehyde as the crosslinking agent. In addition, additives such as zinc compounds, chlorides, and iodides may be contained individually or simultaneously at a concentration of about 0.1 to 10% by mass for the purpose of improving the adhesive strength or water resistance of the adhesive. The additive system of the adhesive is not particularly limited, and can be appropriately selected by those with ordinary knowledge in the technical field to which the invention pertains. After bonding the transparent protective layer and the polarizing element with an adhesive, a polarizing plate can be obtained by drying or heat treatment at an appropriate temperature.

When the polarizing element or polarizing plate is attached to display devices such as liquid crystal and organic electroluminescence (commonly referred to as OLED or OEL) depending on the situation, a viewing angle can also be provided on the surface of the protective layer or film that becomes the non-exposed surface. Various functional layers for improvement and/or contrast improvement, and layers or films with brightness enhancement properties. Various functional layers are, for example, layers or films for controlling retardation. The polarizing plate is preferably attached to these films or display devices by an adhesive.

The polarizing element or the polarizing plate may have various known functional layers such as an AR layer (anti-reflection layer), an anti-glare layer, and a hard coat layer on the exposed surface of the transparent protective layer or film. The coating method is preferable to produce the layers having the various functions, but the films having the functions can also be pasted through an adhesive or an adhesive.

As said hard coat layer, the hard coat layer of acrylic type or polysiloxane type, the protective layer of urethane type, etc. are mentioned, for example. In addition, with the above AR layer, it is expected to further improve the light transmittance of the single plate. The AR layer can be formed by, for example, silicon dioxide, titanium oxide, etc., by vapor deposition or sputtering, or by thinly coating a fluorine-based substance.

The polarizing element or polarizing plate is attached to, for example, liquid crystal, organic electroluminescent In the case of display devices such as light (commonly referred to as OLED or OEL), various functional layers for viewing angle improvement and/or contrast improvement can also be provided on the surface of the transparent protective layer or film that becomes the non-exposed surface, and have brightness enhancement properties. layer or film. Various functional layers are, for example, layers or films for controlling retardation (hereinafter, also referred to as "retardation plates"). The polarizing plate of the present invention can also be used as an elliptically polarizing plate by attaching a retardation plate. The polarizing plate is preferably attached to these films or display devices by means of an adhesive.

The polarizing plate of the present invention can achieve achromaticity while having high transmittance and high degree of polarization, especially, high-quality white like paper can be displayed in white display, and high durability of neutral black can be displayed in black display polarizer.

<Display device>

The polarizing element or polarizing plate of the present invention is provided with a protective layer or functional layer and a transparent support such as glass, crystal, sapphire, etc. as required, and is applied to liquid crystal projectors, electronic computers, clocks, notebook computers, word processors, LCD TVs, polarized lenses, polarized glasses, navigators, and indoor and outdoor measuring instruments or monitors, etc.

In particular, the polarizing element or polarizing plate of the present invention can also be applied to organic electroluminescence and the like in addition to liquid crystal display devices such as reflective liquid crystal display devices, transflective liquid crystal display devices, and liquid crystal display devices. The liquid crystal display device using the polarizing element or polarizing plate of the present invention can display high-quality paper white and neutral black. Furthermore, the liquid crystal display device is a liquid crystal display device with high durability, high reliability, long-term high contrast ratio and high color reproducibility.

[Example]

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto. The % in the example is the quality standard unless otherwise stated.

[Example 1]

A polyvinyl alcohol film (VF-PS #7500 manufactured by Kuraray Co., Ltd.) with an average degree of polymerization of 2400 and a saponification degree of 99% or more was immersed in warm water at 45°C for 2 minutes, and a swelling treatment was performed to make the stretch ratio 1.30 times. A dyeing solution at 45°C containing 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of Glauber's salt, 0.105 parts by mass of the compound of formula (1-4), and 0.22 parts by mass of the compound of formula (2-11) , the swollen film was immersed for 7 minutes and 30 seconds so that the film contained the azo compound. The obtained film was immersed in a 40°C aqueous solution containing 20 g/l of boric acid (manufactured by Societa Chimica Larderello s.p.a.) for 1 minute. While stretching the film after immersion by 5.0 times, stretching treatment was performed for 5 minutes in an aqueous solution containing 30.0 g/l of boric acid at 50°C. The obtained film was immersed in water at 25° C. for 20 seconds while maintaining the tensioned state for washing treatment. The film after washing was dried at 70° C. for 9 minutes to obtain a polarizing element. For this polarizing element, polyvinyl alcohol (NH-26, manufactured by VAM & POVAL, Japan) was dissolved in water at 4% and used as an adhesive, and an alkali-treated triacetin-based cellulose film (Fuji Photographic Film) was used as an adhesive. A polarizing plate was obtained by laminating ZRD-60, manufactured by the company. The obtained polarizing plate has the optical properties of the above-mentioned polarizing element, especially maintaining the single transmittance of each wavelength, the parallel position transmittance of each wavelength, the orthogonal position transmittance of each wavelength, hue, degree of polarization, etc. This polarizing plate was used as the measurement sample of Example 1.

[Example 2]

Except that the swollen film was mixed with 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of Glauber's salt, 0.15 parts by mass of the compound of formula (1-18), and 0.28 parts by mass of the compound of formula (2-12). A polarizing plate was produced in the same manner as in Example 1 except that 0.05 parts by mass of the compound of the formula (6-1) was treated in a dyeing solution at 45°C for 6 minutes, and the azo compound was contained.

[Example 3]

Except for the swollen film containing 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, no 1.5 parts by mass of Glauber's salt, 0.17 parts by mass of the compound of the formula (1-22), 0.28 parts by mass of the compound of the formula (2-20), 0.11 parts by mass of the compound of the formula (6-1) in a dyeing solution at 45°C A polarizing plate was produced in the same manner as in Example 1 except that the azo compound was treated for 5 minutes and 30 seconds.

[Example 4]

Except that the swollen film was mixed with water containing 1500 parts by mass, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of Glauber's salt, 0.145 parts by mass of the compound of formula (1-3), and 0.28 parts by mass of the compound of formula (2-12). A polarizing plate was produced in the same manner as in Example 1 except that 0.24 parts by mass of the compound of formula (6-1) was treated in a dyeing solution at 45°C for 6 minutes and 15 seconds, and the azo compound was contained.

[Example 5]

Except that the swollen film was mixed with 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of Glauber's salt, 0.145 parts by mass of the compound of formula (1-4), and 0.28 parts by mass of the compound of formula (2-12). A polarizing plate was produced in the same manner as in Example 1 except that 0.255 parts by mass of the compound of formula (6-1) was treated in a dyeing solution at 45°C for 6 minutes and 15 seconds, and the azo compound was contained.

[Example 6]

Except that the swollen film was mixed with 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of Glauber's salt, 0.165 parts by mass of the compound of formula (1-4), and 0.31 parts by mass of the compound of formula (2-13). 295 parts by mass of the compound of formula (6-1) was treated in a dyeing solution at 45°C for 6 minutes, except that the azo compound was contained, and a polarizing plate was produced in the same manner as in Example 1.

[Example 7]

Except that the swollen film was mixed with water containing 1500 parts by mass, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of Glauber's salt, 0.155 parts by mass of the compound of formula (1-10), and 0.28 parts by mass of the compound of formula (2-12). A polarizing plate was produced in the same manner as in Example 1 except that 0.265 parts by mass of the compound of formula (6-1) was treated in a dyeing solution at 45°C for 6 minutes and 30 seconds, and the azo compound was contained.

[Example 8]

Except that the swollen film was mixed with water containing 1500 parts by mass, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of Glauber's salt, 0.155 parts by mass of the compound of formula (1-8), and 0.28 parts by mass of the compound of formula (2-5). A polarizing plate was produced in the same manner as in Example 1 except that 0.265 parts by mass of the compound of formula (6-1) was treated in a dyeing solution at 45°C for 7 minutes and 15 seconds, and the azo compound was contained.

[Example 9]

Except that the swollen film was mixed with 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of Glauber's salt, 0.155 parts by mass of the compound of formula (1-8), and 0.28 parts by mass of the compound of formula (2-10). A polarizing plate was produced in the same manner as in Example 1 except that 0.265 parts by mass of the compound of formula (6-1) was treated in a dyeing solution at 45°C for 7 minutes, and the azo compound was contained.

[Example 10]

Except that the swollen film was mixed with 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of Glauber's salt, 0.155 parts by mass of the compound of formula (1-8), and 0.30 parts by mass of the compound of formula (2-12). A polarizing plate was produced in the same manner as in Example 1 except that 0.275 parts by mass of the compound of formula (6-1) was treated in a dyeing solution at 45°C for 7 minutes, and the azo compound was contained.

[Example 11]

Except that the swollen film was mixed with 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of Glauber's salt, 0.155 parts by mass of the compound of formula (1-8), and 0.30 part by mass of the compound of formula (2-9). A polarizing plate was produced in the same manner as in Example 1 except that 0.275 parts by mass of the compound of formula (6-1) was treated in a dyeing solution at 45°C for 7 minutes, and the azo compound was contained.

[Example 12]

Except that the swollen film was mixed with 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of Glauber's salt, 0.18 parts by mass of the compound of formula (1-4), and 0.57 parts by mass of the compound of formula (2-3) A polarizing plate was produced in the same manner as in Example 1 except that 0.26 parts by mass of the compound of formula (6-1) was treated in a dyeing solution at 45°C for 7 minutes, and the azo compound was contained.

[Example 13]

Except that the swelled film was mixed with 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of Glauber's salt, 0.18 parts by mass of the compound of formula (1-4), and 0.45 parts by mass of the compound of formula (2-4) A polarizing plate was produced in the same manner as in Example 1 except that 0.26 parts by mass of the compound of formula (6-1) was treated in a dyeing solution at 45°C for 9 minutes, and the azo compound was contained.

[Example 14]

In Example 5, except that 0.23 parts by mass of the compound of formula (6-2) was substituted for 0.255 parts by mass of the compound of formula (6-1), the dyeing solution was treated for 6 minutes and 15 seconds, and the azo compound was contained , and the rest are the same as in Example 1 to produce a polarizing plate.

[Example 15]

Except that in Example 5, 0.22 parts by mass of C.I. direct orange 72 was substituted for 0.255 parts by mass of the compound of formula (6-1) and treated in the dyeing solution for 6 minutes, and the azo compound was contained, the rest were the same as those in the examples 1 In the same way, make a polarizing plate.

[Example 16]

In Example 5, except that 0.23 parts by mass of C.I. direct yellow 28 was substituted for 0.255 parts by mass of the compound of formula (6-1), the dyeing solution was treated for 6 minutes and 15 seconds, and the azo compound was contained, and the rest were treated with In the same manner as in Example 1, a polarizing plate was produced.

[Comparative Example 1]

As a general dye-based polarizing plate, a high-transmittance dye-based polarizing plate SHC-115 manufactured by Polatechno Co., Ltd., which has neutral gray, was obtained as a measurement sample.

[Comparative Example 2]

As a general dye-based polarizing plate, a dye-based polarizing plate SHC-128 manufactured by Polatechno Co., Ltd., which has a high contrast ratio of neutral gray, was obtained as a measurement sample.

[Comparative Examples 3 to 8]

According to the production method of Comparative Example 1 of Patent Document 13, the iodine-containing time was set to 5 minutes and 30 seconds in Comparative Example 3, 4 minutes and 45 seconds in Comparative Example 4, and 4 minutes and 45 seconds in Comparative Example 5. 15 minutes, 3 minutes and 30 seconds in Comparative Example 6, 4 minutes and 00 seconds in Comparative Example 7, and 5 minutes and 15 seconds in Comparative Example 8 to produce an iodine-based polarizing plate that does not contain The polarizing plate of the azo compound was used as the measurement sample.

[Comparative Example 9]

An iodine-based polarizing plate SKW-18245P manufactured by Polatechno Co., Ltd. showing paper white at the parallel position was obtained as a measurement sample.

[Comparative Examples 10 and 11]

Except that the aqueous solution (dyeing solution) containing only the azo compound in Example 1 has the same composition as that of Example 1 of Patent Document 3, the rest is the same as that of Example 1 of the present application, The time for immersing the swollen film in the aqueous solution was adjusted so as to have a transmittance approximately equal to that of Example 1, and an azo compound was contained to prepare a polarizing plate.

[Comparative Example 12]

In Example 5, the azo compound described in Synthesis Example 1 of Patent Document 14 was replaced by the compound of formula (1-4) and contained in the dyeing liquid in the same amount, and the azo compound was contained, and the rest were the same as those in the implementation. In the same manner as in Example 1, a polarizing plate was produced.

[Comparative Example 13]

Polarized light was produced in the same manner as in Example 1, except that in Example 5, C.I. Direct Red 4BH was substituted for the compound of formula (1-4) and contained in the dyeing solution in the same amount, and the azo compound was contained plate.

[Comparative Example 14]

As in Example 1 of Patent Document 15 concerning a dye-based polarizing plate, a polarizing plate was produced.

[Comparative Example 15]

As in Example 3 of Patent Document 16 concerning a dye-based polarizing plate, a polarizing plate was produced.

[Comparative Example 16]

As in Example 1 of Patent Document 17 concerning a dye-based polarizing plate, a polarizing plate was produced.

[Comparative Example 17]

A polarizing plate was produced as in Example 15 No. 1 of Patent Document 18 concerning a dye-based polarizing plate.

[Comparative Example 18]

Except in Example 5, 0.98 parts by mass of C.I. Direct Red 80 of an azo compound having the same color and having a ureido skeleton is used to replace the compound of formula (1-4), and the transmittance of each wavelength at the orthogonal position is about It is the same as in Example 1 except that it is adjusted so that its color becomes black. Make polarizers.

[Comparative Example 19]

Except that in Example 5, 0.45 parts by mass of C.I. direct blue 6 of an azo compound having a dichroism of the same color and having a dianisidine skeleton was used to replace the compound of formula (1-12), and each wavelength of the orthogonal position was used. The transmittance is approximately constant, and a polarizing plate was produced in the same manner as in Example 1 except that the color was designed to be black.

[Evaluation method]

The evaluation of the measurement samples obtained in Examples 1 to 16 and Comparative Examples 1 to 19 was performed as follows.

(a) The single transmittance Ts of each wavelength, the parallel transmittance Tp of each wavelength, and the orthogonal transmittance Tc of each wavelength

Using a spectrophotometer (“U-4100” manufactured by Hitachi, Ltd.), the individual transmittance Ts, parallel position transmittance Tp, and orthogonal position transmittance Tc of each wavelength of each measurement sample were measured. Here, the individual transmittance Ts of each wavelength is the transmittance of each wavelength when measured with one measurement sample. The parallel position transmittance Tp of each wavelength is the spectral transmittance of each wavelength measured by overlapping two measurement samples so that their absorption axis directions are parallel. The cross-position transmittance Tc of each wavelength is the spectral transmittance measured by overlapping two polarizers so that their absorption axes are orthogonal. Measurements were performed covering wavelengths from 400 to 700 nm. From the results obtained by the measurement, the obtained parallel position transmittance Tp and orthogonal position transmittance Tc are the average value of each wavelength in 420 to 480 nm and the average value of each wavelength in 520 to 590 nm, respectively. , and the average value of each wavelength in 600 to 640 nm are shown in Table 1.

(b) The transmittance Ys of the monomer after the correction of the luminous factor, the flatness after the correction of the luminous factor Line transmittance Yp, and orthogonal transmittance Yc after luminous factor correction

Calculate the transmittance Ys (%) of the monomer after the correction of the luminous factor, the transmittance of the parallel position Yp (%) after the correction of the luminous factor, and the transmittance of the orthogonal position Yc after the correction of the luminous factor of each measurement sample. (%). The single transmittance Ys (%) after luminous factor correction, the parallel transmittance Yp (%) after luminous factor correction, and the orthogonal transmittance Yc (%) after luminous factor correction are between 400 and 400. In the wavelength region of 700 nm, the above-mentioned single transmittance Ts of each wavelength, the parallel transmittance Tp of each wavelength, and the orthogonal transmittance Tc of each wavelength, obtained at each predetermined wavelength interval dλ (here, 5 nm) According to JIS Z 8722:2009, the transmittance is corrected to the luminous factor. Specifically, the above-mentioned individual transmittance Ts of each wavelength, parallel position transmittance Tp of each wavelength, and orthogonal position transmittance Tc of each wavelength are substituted into the following formulas (V to VII) to calculate respectively. . In addition, in the following formulae (V to VII), Pλ represents the spectral distribution of standard light (C light source), and yλ represents a 2-degree visual field color matching function. The results are shown in Table 1.

(c) Contrast

By calculating the parallel position after correction of the luminous factor measured using 2 pieces of the same measurement sample The contrast ratio (CR) was obtained from the ratio (Yp/Yc) of the transmittance to the transmittance at the orthogonal position after luminous factor correction. The results are shown in Table 1.

(d) The absolute value of the difference between the average transmittances of each wavelength in the two wavelength bands

Table 2 shows the average value of the parallel position transmittance Tp of each wavelength and the orthogonal position transmittance Tc of each wavelength at 520 to 590 nm and the average value of each wavelength at 420 to 480 nm for each measurement sample. The absolute value of the difference between the average values of wavelengths, and the absolute value of the difference between the average value of each wavelength in 520 to 590 nm and the average value of each wavelength in 600 to 640 nm.

As shown in Table 1 and Table 2, the parallel position transmittance Tp of each wavelength of the measurement samples of Examples 1 to 16 is 30% or more in average value in 520 to 590 nm, and has high transmittance. Furthermore, the parallel transmittance Tp of each wavelength is the difference of each wavelength in the range of 420 to 480 nm. The difference between the average value and the average value of each wavelength in 520 to 590 nm is 2.5% or less in absolute value, and the average value of each wavelength in 520 to 590 nm and the average value of each wavelength in 600 to 640 nm. The difference between the values was 3.0% or less in absolute terms, and both were very low values. In addition, the orthogonal position transmittance Tc of each wavelength is the difference between the average value of each wavelength in 420 to 480 nm and the average value of each wavelength in 520 to 590 nm is 1.0% or less in absolute value, and in 520 The difference between the average value of each wavelength to 590 nm and the average value of each wavelength in 600 to 640 nm is 1.0% or less in absolute terms, and both are very low values. Therefore, the measurement samples obtained in Examples 1 to 16 show that the average transmittance of each wavelength is approximately constant in the parallel position and the orthogonal position, respectively.

On the other hand, the measurement samples of Comparative Examples 1 to 9 and Comparative Examples 14 to 19 are the absolute values of the difference between the average values of the above-mentioned wavelength bands of the parallel-position transmittance Tp at each wavelength shown in Table 2, And, at least any one of the absolute values of the difference between the average values of the above-mentioned wavelength bands of the orthogonal bit transmittance Tc of each wavelength shows a high value.

In addition, when comparing Examples 1 to 16 and Comparative Examples 10 to 13 in which the transmittance of the monomer after the correction of the luminous factor was 39 to 42%, the contrast ratios of Comparative Examples 10 to 13 were 27 to 139. The contrast ratios of Examples 1 to 16 are more than 180. In particular, if Example 5 is compared with Comparative Example 12, the present case has a contrast ratio that is about 6 times higher. Thus, it can be seen that the polarizing plate system of the present invention has high performance.

(e) Polarization degree ρy after luminous factor correction

The luminous factor-corrected polarization degree ρy of each measurement sample was obtained by substituting the luminous-factor-corrected parallel-position transmittance Yp and the luminous-factor-corrected orthogonal-position transmittance Yc into the following equation. The results are shown in Table 3.

ρy={(Yp-Yc)/(Yp+Yc)} ^1/2 ×100 Formula (VIII)

(f) Chromaticity a* value and b* value

For each measurement sample, according to JIS Z 8781-4:2013, when measuring the single transmittance Ts of each wavelength, when measuring the parallel position transmittance Tp at each wavelength, and when measuring the orthogonal position transmittance Tc at each wavelength The respective chromaticity a* values and b* values were measured. The measurement was carried out using the above-mentioned spectrophotometer, and measured the transmitted color, the reflected color, and the incident from the outside of the room. The light source system uses a C light source. The results are shown in Table 3. Here, a*-s and b*-s, a*-p and b*-p, and a*-c and b*-c correspond to the individual transmittance Ts and parallel position transmittance Tp, respectively. And the chromaticity a* value and b* value when measuring the transmittance Tc of orthogonal position.

(g) Observation of color

For each measurement sample, two identical measurement samples were superimposed on a white light source in respective states of a parallel position and an orthogonal position, and the color observed at this time was examined. Observation was performed by 10 observers visually, and the most observed colors are shown in Table 3. In addition, in Table 3, the color of the parallel position refers to the color of the state in which two identical samples are overlapped so that their absorption axis directions are parallel to each other (when displayed in white), and the color of the orthogonal position refers to the color of the two identical samples. The color of the state (in the case of black display) in which the absorption axis directions are superimposed so that they are orthogonal to each other. Basically, the color of the polarized light is "white" in the parallel position, and "black" in the orthogonal position. The black color of purple is called "blue-purple".

As shown in Table 3, the measurement samples of Examples 1 to 16 have a monomer transmittance of 35% or more after luminescence factor correction. It can be seen that the measurement samples of Examples 1 to 16 have high transmittance, and at the same time exhibit a high degree of polarization of 99% or more, and can fully display white and black. Furthermore, in the measurement samples of Examples 1 to 16, the absolute values of a*-s, b*-s, and a*-p were respectively 1.0 or less, and the absolute values of b*-p were 2.0 or less, showing extremely low values. . When the measurement samples of Examples 1 to 16 were visually observed, they appeared high-quality paper-like white in the parallel position. Also, the wavelength band is 420 nm The transmittance of the orthogonal position in each wavelength to 480nm, 520nm to 590nm, and 600nm to 640nm is 1% or less or the polarization degree is about 97% or more, so black appears. On the other hand, Comparative Examples 1 to 9 and Comparative Examples 14 to 19 are at least any one of a*-s, b*-s, a*-p, b*-p, a*-c, and b*-c The above indicates a high value, or, as in Comparative Example 9, when the transmittance at the orthogonal position is 1% or more, if visually observed, it is not colorless at the parallel position or the orthogonal position.

From the above, the polarizing element of the present invention maintains high transmittance of the monomer and the transmittance of the parallel position, and at the same time, it can display high-quality white paper in the parallel position, which means that the monomer has high quality without coloring. The hue of a neutral color (a colorless neutral gray). Furthermore, it can be seen that the polarizing element of the present invention maintains a high transmittance of a single element after correction of the luminous factor, exhibits achromaticity in the parallel position, and also has a high degree of polarization. Furthermore, it can be seen that the polarizing element of the present invention can obtain a polarizing element that displays a colorless black with a high-quality feeling in an orthogonal position.

(h) Durability test

The measurement samples of Examples 1 to 16 and Comparative Examples 3 to 9 were applied in an environment of 85° C. and a relative humidity of 85% RH for 240 hours. As a result, the measurement samples of Examples 1 to 16 showed no change in transmittance or hue. On the other hand, in Comparative Examples 3 to 9, the degree of polarization was reduced by more than 10%, the b*-c was lower than -10, and the color of the appearance changed significantly to blue, especially when two measurement samples were arranged in the orthogonal position. (When displaying in black), the system is sufficiently blue. Therefore, it can be seen that Examples 1 to 16 have high durability.

[Industrial Availability]

From the above results, it can be seen that the polarizing element of the present invention not only has high transmittance and high polarization degree, but also has no color in both white display and black display, especially, white A high-performance achromatic polarizer, which exhibits high-quality white color during color display, and an achromatic polarizer and a display device using the achromatic polarizer, are extremely useful in the industry.

Claims (16)

A polarizing element comprising: an azo compound represented by formula (1) or a salt thereof, and an azo compound represented by formula (2) or a salt thereof,

In the formula, Ar ₁ represents a substituted phenyl group or a substituted naphthyl group, and Rr ₁ to Rr ₄ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, and an alkoxy group having 1 to 4 carbon atoms. , or an alkoxy group with a carbon number of 1 to 4 having a sulfonic acid group, j represents 0 or 1, Xr ₁ represents an amino group that can have a substituent, a phenylamino group that can have a substituent, and a benzene that can have a substituent azo, optionally substituted benzylamino, or optionally substituted benzylamino;

In the formula, Ag ₁ represents a substituted phenyl group or a substituted naphthyl group, and Bg and Cg are each independently represented by the following formula (3) or (4), and any one of them is represented by the formula (3) As shown, Xg ₁ represents an amino group that may have a substituent, a phenylamino group that may have a substituent, a phenylazo group that may have a substituent, a benzyl group that may have a substituent, or a substituted group the benzylamino group;

In the formula, Rg ₁ represents a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an alkoxy group having a sulfonic acid group having 1 to 4 carbon atoms, and p ₁ represents 0 to 2 the integer;

In the formula, Rg ₂ and Rg ₃ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an alkoxy group having a sulfonic acid group and having 1 to 4 carbon atoms; The content of the azo compound represented by the above formula (2) or a salt thereof is 0.01 to 5000 parts by mass relative to 100 parts by mass of the content of the azo compound of the above formula (1). The polarizing element according to claim 1, wherein Cg in the above formula (2) is represented by the above formula (3). The polarizing element according to claim 1 or 2, wherein the azo compound represented by the above formula (2) or a salt thereof is an azo compound represented by the following formula (5) or a salt thereof,

In the formula, Ag ₂ represents a substituted phenyl group or a substituted naphthyl group, and Rg ₄ and Rg ₅ each independently represent a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group, or a sulfonic acid group. The alkoxy group with 1 to 4 carbon atoms, Xg ₂ represents an amino group that can have a substituent, a phenylamino group that can have a substituent, a phenylazo group that can have a substituent, and a benzyl that can have a substituent In the acyl group or the optionally substituted benzylamino group, p ₂ and p ₃ each independently represent an integer of 0 to 2. The polarizing element according to claim 3, wherein p ₂ and p ₃ described in the above formula (5) are 1 or 2, respectively. The polarizing element according to claim 1 or 2, wherein Xr ₁ in the above formula (1) is a phenylamino group which may have a substituent. The polarizing element according to claim 1 or 2, wherein Xg ₁ described in the above formula (2) is a phenylamino group which may have a substituent. The polarizing element described in item 1 or 2 of the claimed scope further comprises an azo compound represented by the following formula (6) or a salt thereof,

In formula (6), Ay ₁ represents a sulfonic acid group, a carboxyl group, a hydroxyl group, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms, and Ry ₁ to Ry ₄ each independently represent a hydrogen atom, carbon An alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, or an alkoxy group having a sulfonic acid group having 1 to 4 carbon atoms, and k represents an integer of 1 to 3. The polarizing element according to claim 1 or 2, wherein the transmittance of each wavelength obtained by measuring two of the polarizing elements so that their respective absorption axis directions are parallel to each other is 420 nm. The difference between the average transmittance to 480nm and the average transmittance from 520nm to 590nm is less than 2.5% in absolute value, and the difference between the average transmittance from 520nm to 590nm and the average transmittance from 600nm to 640nm is in absolute value Calculated as 3.0% or less. The polarizing element according to claim 1 or 2, wherein the a* value and b are obtained when the above-mentioned polarizing element alone is based on JIS Z 8781-4:2013 and the transmittance is measured using natural light The absolute value of the * value is all below 1.0. Here, if a*-s is used to represent the a* value of the monomer, it is -1.0≦a*-s≦1.0, and if b*-s is used to represent the monomer. The value of b* is -1.0≦b*-s≦1.0; when the two polarizers are superimposed so that their respective absorption axis directions become parallel to each other, The absolute values of the a* value and the b* value obtained when the transmittance is measured according to JIS Z 8781-4:2013 and using natural light in the configuration state are both below 2.0. Here, if expressed as a*-p The a* value in the parallel position is -2.0≦a*-p≦2.0, and if b*-p is used to represent the b* value in the parallel position, it is -2.0≦b*-p≦2.0. The polarizing element according to claim 1 or 2, wherein the light-emitting factor correction of the polarizing element has a transmittance of 35% to 45%, and the two polarizing elements have their respective absorption axes. The average transmittance of each wavelength of 520 nm to 590 nm obtained in a state where the directions are overlapped and arranged so as to be parallel to each other is 28% to 45%. The polarizing element according to claim 1 or 2, wherein the transmittance of each wavelength is obtained by arranging two polarizing elements so that their respective absorption axis directions are overlapped and arranged so as to be orthogonal to each other. Among them, the difference between the average transmittance from 420nm to 480nm and the average transmittance from 520nm to 590nm is less than 1.0% in absolute value, and the difference between the average transmittance from 520nm to 590nm and the average transmittance from 600nm to 640nm The absolute value is 1.0% or less. The polarizing element according to item 1 or 2 of the claimed scope, wherein the orthorhombic transmittance of each wavelength in the wavelength bands of 420 nm to 480 nm, 520 nm to 590 nm, and 600 nm to 640 nm is less than 1%, or the polarized light The degree is above 97%. The polarizing element according to claim 1 or 2, wherein the two polarizing elements are arranged so as to overlap each other so that their respective absorption axis directions are orthogonal to each other, according to JIS Z 8781-4:2013 The absolute values of the a* value and the b* value obtained when measuring the transmittance using natural light are both below 2.0. Here, if a*-c represents the a* value at the orthogonal position, it is -2.0 ≦a*-c≦2.0, if b*-c represents the b* value at the orthogonal position, it is -2.0≦b*-c≦2.0. The polarizing element according to claim 1 or 2, wherein the polarizing element comprises a polyvinyl alcohol-based resin film as a base material. A polarizing plate comprising the polarizing element described in any one of claims 1 to 14 of the patent application scope, and a transparent protective layer provided on one side or both sides of the polarizing element. A display device comprising the polarizing element described in any one of claims 1 to 14 of the patent application scope, or the polarizing plate described in the claim 15 claim scope.