JPWO2019117131A1 - Achromatic polarizing element, and achromatic polarizing plate and display device using this - Google Patents

Abstract

A polarizing element containing 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 is a phenyl group having a substituent or a naphthyl group having a substituent. Rr1 to Rr4 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, where j is. Indicates 0 or 1, and Xr1 has an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, and a substituent. Indicates a benzoyl group which may be present or a benzoylamino group which may have a substituent; in the formula, Ag1 indicates a phenyl group or a naphthyl group having a substituent, and Bg and Cg are independent of each other. It is represented by the following formula (3) or formula (4), one of which is represented by the formula (3), and Xg1 may have an amino group or a substituent which may have a substituent. Indicates a phenylamino group, 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 is hydrogen. Indicates an 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 having a sulfo group, and p1 indicates an integer of 0 to 2; in the formula, Rg2 And Rg3 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 having a sulfo group.

Description

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

Polarizing elements are generally made of iodine on a substrate such as a stretch-oriented film of polyvinyl alcohol or a derivative thereof, or a polyene-based film in which polyene is generated and oriented by dehydroxation of a polyvinyl chloride film or dehydration of a polyvinyl alcohol-based film. It is manufactured by adsorbing and orienting a dichroic dye. A polarizing plate obtained by laminating a protective film made of triacetyl cellulose or the like on this polarizing element via an adhesive layer is used in a liquid crystal display device or the like. A polarizing plate using iodine as a dichroic dye is called an iodine-based polarizing plate, while a polarizing plate using a dichroic dye as a dichroic dye, for example, an azo compound having dichroism is a dye-based polarizing plate. Is called. Of these, dye-based polarizing plates have high heat resistance, high humidity heat durability, and high stability, and are characterized by high color selectivity due to the blending of dyes, while having the same degree of polarization. There is a problem that the transmittance and contrast are low as compared with the iodine-based polarizing plate. Therefore, a polarizing element having high transmittance and high polarization characteristics in addition to maintaining high durability and various color selectivity is desired.

Further, even in the case of dye-based polarizing plates having various color selectivity, the conventional polarizing elements have a positional relationship in which the absorption axis directions of the two polarizing elements are parallel to each other (hereinafter, also referred to as "parallel position"). There was a problem that the white color became yellowish white when it was arranged so as to be (.) To show white color (hereinafter, also referred to as “white display” or “bright display”). .. In order to improve the problem that the white color becomes yellowish, even if the polarizing element is manufactured by suppressing the yellowish color, the conventional polarizing plate has a position where the absorption axis directions of the two polarizing elements are orthogonal to each other. When they are arranged so as to be in a relationship (hereinafter, also referred to as “orthogonal position”) to indicate black (hereinafter, also referred to as “black display” or “dark display”), black is colored blue. There was a problem of doing. Therefore, there has been a demand for a polarizing plate that exhibits achromatic white when displayed in white and black when displayed in black. In particular, it has been difficult to obtain a polarizing plate having high-quality white when displayed in white, commonly known as a paper-white polarizing plate.

In order for the polarizing plate to be achromatic, it is necessary for the transmittance of each wavelength to be a substantially constant value regardless of the wavelength in the parallel position or the orthogonal position, but it has been possible to obtain such a polarizing plate. Was not done.

The reason why the hues of white display and black display are different is that the wavelength dependence of the transmittance is not the same in the parallel position and the orthogonal position, and in particular, the transmittance is not constant over the visible light region. Furthermore, the fact that the dichroism is not constant over the visible light region is one of the factors that make it difficult to realize an achromatic polarizing plate.

Taking an iodine-based polarizing plate as an example, iodine-based polarizing plates using polyvinyl alcohol (hereinafter, also referred to as “PVA”) as a base material and iodine as a dichroic dye generally have 480 nm and 600 nm. Has absorption centered on iodine. Absorption of 480nm is polyiodine _{I 3} ^- complex of the PVA, the absorption of 600nm polyiodine _{I 5} ^- is said to be due to the complex of the PVA. Polarization at each wavelength (dichroic) is polyiodine I ₅ ^- towards the polarization-based complex of a PVA (dichroic) is polyiodine I ₃ ^- polarization degree based on the complex of the PVA ( Higher than dichroism). That is, when trying to make the transmittance at the orthogonal position constant at each wavelength, the transmittance at the parallel position is higher at 600 nm than at 480 nm, and a phenomenon that white is colored yellow when displayed in white has occurred. On the contrary, when trying to make the transmittance at the parallel position constant, the transmittance at the orthogonal position is lower at 600 nm than at 480 nm, so that black is colored blue when displayed in black. If the white color is yellow when displayed in white, it generally gives the impression that deterioration has progressed, which is not preferable. Also, if the blue color disappears when displaying black, it gives the impression that there is no sense of luxury because it is not clear black. Further, in the iodine-based polarizing plate, it is difficult to control the hue mainly in the vicinity of 550 nm, which has high luminosity factor, because there is no complex based on the wavelength.

As described above, since the degree of polarization (dichroism) of each wavelength is not constant, the wavelength dependence of the degree of polarization has occurred. Further, since there are only two dichroic dyes of 480 nm and 600 nm, which are absorbed by the complex of iodine and PVA, the hue cannot be adjusted with the iodine-based polarizing plate composed of iodine and PVA.

Methods for improving the hue of an iodine-based polarizing plate are described in Patent Document 1 and Patent Document 2. Patent Document 1 describes a polarizing plate having a neutral coefficient calculated and an absolute value of 0 to 3. Patent Document 2 describes a polarizing film in which the transmittance at 410 nm to 750 nm is within ± 30% of the average value, and the color is adjusted by directly adding a dye, a reactive dye, or an acid dye in addition to iodine. Has been done. Further, as in Patent Document 3, a technique of an achromatic dye-based polarizing plate is also disclosed.

JP-A-2002-169024 Japanese Unexamined Patent Publication No. 10-13301 WO2014 / 162635 Japanese Unexamined Patent Publication No. 8-291259 JP-A-2002-275381 WO2015 / 152026 Japanese Unexamined Patent Publication No. 1-1612202 Japanese Unexamined Patent Publication No. 1-172907 Japanese Unexamined Patent Publication No. 1-183602 Japanese Unexamined Patent Publication No. 1-248105 Japanese Unexamined Patent Publication No. 1-265205 Special Fair 7-92531 Japanese Unexamined Patent Publication No. 2008-06522 Japanese Unexamined Patent Publication No. 2003-215338 Japanese Unexamined Patent Publication No. 11-218611 Japanese Unexamined Patent Publication No. 2001-033627 Japanese Unexamined Patent Publication No. 2004-251962 Japanese Unexamined Patent Publication No. 8-291259

Application of functional dyes (CMC Publishing Co., Ltd., 1st edition, supervised by Masahiro Irie, pp. 98-100)

However, as can be seen from Example 1 of Patent Document 1, for example, even if the neutral coefficient (Np) is low, the parallel hue obtained from JIS Z 8729 has an a * value of −1.67. Moreover, since the b * value is 3.51, it can be seen that the image is yellowish green when displayed in white. Further, the hue at the orthogonal position has an a * value of 0.69, but a b * value of -3.40, so that the black display is a blue polarizing plate. Further, the polarizing film of Patent Document 2 is obtained by setting the a value and the b value in the UCS color space measured using only one polarizing film to an absolute value of 2 or less, and two polarizing films are laminated. It was not possible to express achromatic colors at the same time in both the hues of white display and black display. The average value of the simple substance transmittance of the polarizing film of Patent Document 2 was 31.95% in Example 1 and 31.41% in Example 2, showing low values. As described above, since the polarizing film of Patent Document 2 has low transmittance, it does not have sufficient performance in fields where high transmittance and high contrast are required, particularly in fields such as liquid crystal display devices and organic electroluminescence. .. Further, since the polarizing film of Patent Document 2 uses iodine as the main dichroic dye, the color is obtained after the durability test, particularly after the wet heat durability test (for example, an environment of 85 ° C. and a relative humidity of 85%). The change was large and the durability was inferior.

On the other hand, the dye-based polarizing plate has excellent durability, but the wavelength dependence differs between the parallel position and the orthogonal position, which is the same as the iodine-based polarizing plate. There are almost no azo compounds showing dichroism showing the same hue at the parallel and orthogonal positions, and even if they exist, the dichroism (polarization characteristic) is low. Depending on the type of azo compound having dichroism, there are azo compounds having completely different wavelength dependence in the orthogonal and parallel positions, such as white in white display showing yellow and black in black display showing blue. .. In addition, since the sensitivity of human color differs depending on the brightness of light, even if the color of the dye-based polarizing plate is corrected, the brightness of the light generated by controlling the polarization from the orthogonal position to the parallel position will be different. Appropriate color correction is required. The achromatic polarizing plate cannot be achieved unless the transmittance is a substantially constant value at each wavelength at each of the parallel position and the orthogonal position and there is no wavelength dependence. Further, in order to obtain a polarizing element having high transmittance and high contrast, in addition to simultaneously satisfying a certain transmittance at parallel and orthogonal positions, the degree of polarization (bicolor ratio) of each wavelength is high and , Must be constant. Even when one type of azo compound is applied to a polarizing element, although the wavelength dependence of the transmittance of each wavelength is different between the orthogonal position and the parallel position, two or more types of azo compounds are blended to obtain a constant wavelength. In order to achieve the transmittance in, it is necessary to precisely control the relationship between two or more types of two-color ratios in consideration of the transmittance of each type of parallel position and orthogonal position.

On the other hand, even if the relationship between the transmittance and the two-color ratio of each wavelength in the parallel position and the orthogonal position can be precisely controlled and the transmittance can be made constant in each, it is possible to achieve high transmittance and high contrast. It wasn't done yet. That is, it is difficult to make the color achromatic as the transmittance or the degree of polarization becomes higher, and an achromatic polarizing plate having a high transmittance or a high degree of polarization has not been achieved. It is very difficult to obtain an achromatic polarizing plate with high transmittance and / or high contrast, which cannot be achieved by simply applying a dichroic dye of the three primary colors. In particular, it is extremely difficult to simultaneously achieve constant transmittance and high dichroism at each wavelength in the parallel position. White cannot express high-quality white even with a slight amount of color. In addition, white in the bright state is particularly important because it has high brightness and high sensitivity. Therefore, as a polarizing element, it exhibits achromatic white like high-quality paper when displayed in white, and exhibits achromatic black when displayed in black, and has a single transmittance of 35% or more and a high degree of polarization after correction of visual sensitivity. There is a demand for a polarizing element to have. Patent Document 3 also describes an achromatic polarizing plate at the time of white display and black display, but further improvement in performance is desired.

Therefore, an object of the present invention is high-performance achromatic polarized light which has high transmittance and high polarization degree and is achromatic in both white display and black display, and particularly exhibits high-quality white color in white display. It is an object to provide an element and an achromatic polarizing plate and a display device using the element.

As a result of diligent studies to solve the above problems, the present inventor has no wavelength dependence on dichroism due to the combination of the azo compounds of the formulas (1) and (2), and in each of the parallel position and the orthogonal position. We have found that it is possible to fabricate a polarizing element that is achromatic and has a higher degree of polarization than before. The present inventor has found for the first time that wavelength independence in the visible light region can be achieved even with high transmittance, and is higher than the ability to realize high-quality paper-like white, commonly known as paper white. We have developed a polarizing element with a degree of polarization.

That is, the present invention relates to the following.
Invention 1
A polarizing element containing 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, Ar ₁ represents a phenyl group having a substituent or a naphthyl group having a substituent, and Rr _{1 to} Rr ₄ are independently hydrogen atoms, alkyl groups having 1 to 4 carbon atoms, and 1 to 4 carbon atoms. Indicates an alkoxy group having an alkoxy group or a sulfo group and having 1 to 4 carbon atoms, j indicates 0 or 1, and Xr ₁ may have an amino group or a substituent. Indicates a good phenylamino group, 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, Ag ₁ represents a phenyl group having a substituent or a naphthyl group having a substituent, and Bg and Cg are independently represented by the following formulas (3) or (4), one of which is a formula. Represented by (3), Xg ₁ is an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, or a substituent. Indicates a benzoyl group which may have a benzoyl group, or a benzoylamino group which may have a substituent;

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 1 to 4 carbon atoms, and p ₁ is 0 to 2. Indicates an integer;

In the formula, Rg ₂ and Rg ₃ 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 and having a sulfo group.
Invention 2
The polarizing element according to the invention 1, wherein the 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 phenyl group having a substituent or a naphthyl group having a substituent, and Rg ₄ and Rg ₅ independently form a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group, or a sulfo group, respectively. It shows an alkoxy group having 1 to 4 carbon atoms, and Xg ₂ has an amino group which may have a substituent, a phenylamino group which may have a substituent, and a phenylazo which may have a substituent. group shown, which may have a substituent benzoyl group, or substituted indicates which may benzoylamino group, an integer of p _2, p ₃ each independently 0-2.
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.
Invention 6
The polarizing element according to any one of Inventions 1 to 5, wherein Xg ₁ described in the above formula (2) is a phenylamino group which may have a substituent.
Invention 7
The polarizing element according to any one of 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 sulfo group, a carboxy group, a hydroxy 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 are independent hydrogen atoms. , An alkyl group having 1 to 4 carbon atoms, an alcoholic group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms having a sulfo group, and k represents an integer of 1 to 3 carbon atoms.
Invention 8
In the transmittance of each wavelength obtained by stacking and measuring the two polarizing elements so that their absorption axis directions are parallel to each other, the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm are obtained. The difference between the above is 2.5% or less as an absolute value, and the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 600 nm to 640 nm is 3.0% or less as an absolute value. The polarizing element according to any one of the above.
Invention 9
According to JIS Z 8781-4: 2013, the absolute values of the a * value and b * value obtained when measuring the transmittance using natural light are
Both of the above polarizing elements are 1.0 or less (-1.0 ≤ a * -s ≤ 1.0, -1.0 ≤ b-s * ≤ 1.0).
In a state where the two polarizing elements are stacked and arranged so that their absorption axis directions are parallel to each other, both are 2.0 or less (-2.0 ≤ a * -p ≤ 2.0, -2.0". ≦ b * −p ≦ 2.0)
The polarizing element according to any one of the inventions 1 to 8 (a * -s indicates an a * value of a single substance, b * -s indicates a b * value of a single substance, and a * -p indicates a parallel position. Indicates the a * value in, and b * -p indicates b * in the parallel position).
Invention 10
The single transmittance of the above-mentioned polarizing element after correction of luminosity factor is 35% to 45%.
Inventions 1 to 9 have an average transmittance of 28% to 45% for each wavelength of 520 nm to 590 nm, which is obtained in a state where the two polarizing elements are stacked so that their absorption axis directions are parallel to each other. The polarizing element according to any one of the above.
Invention 11
In the transmittance of each wavelength obtained in a state where the two polarizing elements are stacked and arranged so that their absorption axis directions are orthogonal to each other.
The difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is 1.0% or less as an absolute value, and the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 600 nm to 640 nm. Is 1.0% or less as an absolute value,
The polarizing element according to any one of the inventions 1 to 10.
Invention 12
The polarized light according to any one of Inventions 1 to 10, wherein the orthogonal position transmittance at each wavelength of the wavelength band 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 97% or more. element.
Invention 13
The a * value and b * obtained when measuring the transmittance using natural light in accordance with JIS Z 8781-4: 2013 with the two polarizing elements stacked so that their absorption axis directions are orthogonal to each other. Any of Inventions 1 to 10, wherein the absolute value of each value is 2.0 or less (-2.0 ≤ a * -c ≤ 2.0, -2.0 ≤ b * -c ≤ 2.0). The polarizing element according to item 1 (a * -c indicates an a * value at an orthogonal position, and b * -c indicates a b * at an orthogonal position).
Invention 14
The polarizing element according to any one of inventions 1 to 13, wherein the polarizing element includes a polyvinyl alcohol-based resin film as a base material.
Invention 15
A polarizing plate including the polarizing element according to any one of the inventions 1 to 14 and a transparent protective layer provided on one side or both sides of the polarizing element.
Invention 16
A display device including the polarizing element according to any one of the inventions 1 to 14 or the polarizing plate according to the invention 15.

The present invention is a high-performance achromatic polarizing element that has high transmittance and high degree of polarization and exhibits high-quality white color when displayed in white. In particular, the polarizing element is absent in both white display and black display. It is possible to provide an achromatic polarizing plate and a display device that are colored and that use the same.

In the present specification and claims, the "azo compound or a salt thereof" may be simply referred to as an "azo compound" unless it clearly represents a free form.

In the specification and claims, the "lower" of the lower alkyl group, lower alkoxy group, and lower alkylamino group indicates that the carbon number is 1 to 4, preferably 1 to 3. Further, in the present specification and claims, the "substituent" includes a hydrogen atom for convenience. The phrase "may have a substituent" means that a case without a substituent is also included. For example, a "phenyl group which may have a substituent" includes a simple phenyl group which is not substituted and a phenyl group which has a substituent.

Examples of the "lower (1 to 4 carbon atoms) aliphatic hydrocarbon group" include linear alkyl groups such as methyl group, ethyl group, n-propyl group and n-butyl group, sec-butyl group and tert-. Examples thereof include a split-chain alkyl group such as a butyl group and an unsaturated hydrocarbon group such as a vinyl group.

Examples of the "lower (1 to 4 carbon atoms) alkoxy group" include a methoxy group, an ethoxy group, a propoxy group, an n-butoxy group, a sec-butoxy group, a tert-butoxy group and the like.

<Polarizing element>
The polarizing element according to the present invention includes an azo compound represented by the above formula (1) or a salt thereof, and an azo compound represented by the above formula (2) or a salt thereof. The polarizing element according to the present invention may further optionally further contain an azo compound represented by the above formula (6), and is a substrate containing the formulas (1), (2) and (6). It is preferable to have.

The base material is preferably a film obtained by forming a film of a dichroic dye, particularly a hydrophilic polymer capable of adsorbing an azo compound. The hydrophilic polymer is not particularly limited, and examples thereof include polyvinyl alcohol-based resins, amylose-based resins, starch-based resins, cellulosic resins, and polyacrylate-based resins. The hydrophilic polymer is most preferably a polyvinyl alcohol-based resin or a derivative thereof from the viewpoint of dyeability, processability, crosslinkability and the like of the dichroic dye. A polarizing element can be produced by adsorbing an azo compound or a salt thereof on a base material 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 phenyl group having a substituent or a naphthyl group having a substituent, and Rr _{1 to} Rr ₄ are independently hydrogen atoms, lower alkyl groups, lower alkoxy groups, or sulfo groups. Indicates a lower alkoxy group having a substituent, j indicates 0 or 1, and Xr ₁ has an amino group which may have a substituent, a phenylamino group which may have a substituent, and 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 is shown.

The phenyl group having the above-mentioned substituent or the naphthyl group having the substituent will be described. When Ar ₁ is a phenyl group having a substituent, it is preferable to have at least one sulfo group or carboxy group as the substituent. When the phenyl group has two or more substituents, at least one of the substituents is a sulfo group or a carboxy group, and the other substituents are a sulfo group, a carboxy group, a lower alkyl group, a lower alkoxy group, and the like. A lower alkoxy group having a sulfo group, a nitro group, a benzoyl group, an amino group, an acetylamino group, or a lower alkylamino group substituted amino group is preferable, and the other substituent is more preferably a sulfo group, a methyl group, an ethyl group. , A methoxy group, an ethoxy group, a carboxy group, a nitro group, a benzoyl group, or an amino group, and particularly preferably a sulfo group, a methyl group, a methoxy group, an ethoxy group, a benzoyl group, or a carboxy group. As the lower alkoxy group having a sulfo group, a linear alkoxy group is preferable, and the substituent of the sulfo group is preferably an alkoxy group terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, but particularly preferably. Is a 3-sulfopropoxy group. The number of sulfo groups contained in the phenyl group is preferably 1 or 2, and the substitution position is not particularly limited. However, when the substitution position of the amide group is the 1-position, only the 4-position is a combination of the 2-position and the 4-position. And a combination of 3rd and 5th positions is preferable.

When Ar ₁ is a naphthyl group having a substituent, it is preferable to have at least one alkoxy group having a sulfo group, a hydroxy group and a sulfo group and having 1 to 4 carbon atoms as the substituent, and two or more substituents. When having, at least one of those substituents is a sulfo group, and the other substituent is preferably a sulfo group, a hydroxy group, a carboxy group, or a lower alkoxy group having a sulfo group. As the lower alkoxy group having a sulfo group, a linear alkoxy group is preferable, and the substituent of the sulfo group is preferably an alkoxy group terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, but particularly preferably. It is a 3-sulfopropoxy group. When the number of sulfo groups is 2, the position of the sulfo group on the naphthyl group is preferably a combination of the 4-position and the 8-position and a combination of the 6-position and the 8-position when the substitution position of the amide group is the 2-position. A combination of 6th and 8th positions is more preferable. When the number of sulfo groups contained in the naphthyl group is 3, the combination of the 3-position, the 6-position and the 8-position is particularly preferable as the substitution position of the sulfo group.

The above Rr _{1 to} Rr ₄ independently represent a lower alkoxy group having a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a sulfo group. Rr _{1 to} Rr ₄ are independently, preferably a hydrogen atom, a lower alkyl group, or a lower alkoxy group, and more preferably a hydrogen atom, a methyl group, or a methoxy group. As the lower alkoxy group having a sulfo group, a linear alkoxy group is preferable, and the substituent of the sulfo group is preferably an alkoxy group terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, but particularly preferably. It is a 3-sulfopropoxy group.

The above j indicates 0 or 1. When j is 0, color control becomes easy, and according to JIS Z 8781-4: 2013, the absolute values of the a * value and b * value obtained at the time of transmittance measurement when using natural light are the polarizing element 2. It is a preferable form for color adjustment because it is easy to adjust both of the sheets to 2.0 or less in a state where the sheets are stacked so that their absorption axis directions are parallel to each other. When j is 1, it shows a high degree of polarization, which is one of the preferable forms for improving the performance.

The Xr ₁ may have an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, or a substituent. Indicates a good benzoyl group, or a benzoylamino group which may have a substituent. The amino group which may have a substituent is preferably one or two substituents selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, an amino group and a lower alkylamino group. An amino group having a group, more preferably 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 alkylamino group. It is an amino group having. The phenylamino group which may have a substituent is preferably one or 2 selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, an amino group, and a lower alkylamino 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 sulfo group, and an amino group. is there. The benzoyl group which may have a substituent is preferably a benzoyl group having one selected from the group consisting of a hydrogen atom, a hydroxy group, a sulfo group, an amino group, and a carboxyethylamino group. The benzoylamino group which may have a substituent is preferably a benzoylamino group having one selected from the group consisting of a hydrogen atom, a hydroxy group, an amino group, and a carboxyethylamino group. The phenylazo group which may have a substituent is preferably a group consisting of a hydrogen atom, a hydroxy 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. It is a phenylazo group having 1 to 3 selected from. Xr ₁ is preferably an amino group which may have a substituent, a benzoylamino group which may have a substituent, and a phenylamino group which may have a substituent, and more preferably. Is an amino group which may have a substituent and a phenylamino group which may have a substituent. 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 at the p-position with respect to the bond position indirectly bonded to the naphthalene skeleton represented by the formula (1). Substitution is particularly preferable, and as a specific example, in the case of a phenylamino group, it is preferable that the substituent is at the p-position with respect to the amino group.

Examples of the method for obtaining the azo compound represented by the above formula (1) include, but are not limited to, the methods described in Patent Documents 4 to 6 and the like.

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

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

In the above formula (2), Ag ₁ represents a phenyl group having a substituent or a naphthyl group having a substituent. When Ag ₁ is a phenyl group having a substituent, it is preferable to have at least one sulfo group or carboxy group as the substituent. When the phenyl group has two or more substituents, at least one of the substituents is a sulfo group or a carboxy group, and the other substituent is a sulfo group, a carboxy group, a lower alkyl group, a lower alkoxy group or a sulfo group. It is preferably a lower alkoxy group having a group, a nitro group, an amino group, an acetylamino group, or a lower alkylamino group substituted amino group. The other substituent is more preferably a sulfo group, a methyl group, an ethyl group, a methoxy group, an ethoxy group, a carboxy group, a nitro group or an amino group, and particularly preferably a sulfo group, a methyl group, a methoxy group or an ethoxy group. It is a group or a carboxy group. As the lower alkoxy group having a sulfo group, a linear alkoxy group is preferable, and the substituent of the sulfo group is preferably an alkoxy group terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably 3. − It is a sulfopropoxy group. The number of substituents of the phenyl group is preferably 1 or 2, and the substitution position is not particularly limited. However, when the position of the azo group is the 1-position, only the 4-position is the combination of the 2-position and the 4-position, and the 3-position. A combination of 5 and 5 is preferable. When Ag ₁ is a naphthyl group having a substituent, it is preferable to have at least one sulfo group as the substituent. When the naphthyl group has two or more substituents, at least one of the substituents is a sulfo group, a hydroxy group, an alkoxy group having 1 to 4 carbon atoms having a sulfo group, and the other substituent is sulfo. A lower alkoxy group having a group, a hydroxy group, a carboxy group, or a sulfo group is preferable. It is particularly preferable that the naphthyl group has two or more sulfo groups as a substituent. As the lower alkoxy group having a sulfo group, a linear alkoxy group is preferable, and the substituent of the sulfo group is preferably an alkoxy group terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, but particularly preferably. It is a 3-sulfopropoxy group. When the number of sulfo groups contained in the naphthyl group is 2, the substitution position of the sulfo group is preferably a combination of the 4-position and the 8-position and a combination of the 6-position and the 8-position when the position of the azo group is the 2-position. Is preferable, and the combination of the 6-position and the 8-position is more preferable. When the number of sulfo groups contained in the naphthyl group is 3, the substitution position of the sulfo 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 the 2-position.

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

In the above formula (3), Rg ₁ represents a lower alkoxy group having a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a sulfo group, and is preferably a hydrogen atom, a lower alkyl group, or a lower alkoxy group. It is preferably a hydrogen atom, a methyl group, or a methoxy group. A particularly preferable Rg ₁ is preferably a hydrogen atom or a methoxy group. As the lower alkoxy group having a sulfo group, a linear alkoxy group is preferable, and the substituent of the sulfo group is preferably an alkoxy group terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably 3. − It is a sulfopropoxy group. In the formula (3), the substitution position of Rg ₁ is preferably the 2-position or the 3-position, and more preferably the 3-position, with the azo group substituted on the Ag ₁ side as the 1-position. p ₁ is an integer of 0 to 2. If there is a sulfo group (p ₁ is 1 or 2) the substitution position of the sulfo group may have 6 or 7 position, preferably 6-position is good.

In the above formula (4), Rg ₂ and Rg ₃ each independently represent a lower alkoxy group having a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a sulfo group, and preferably a hydrogen atom, a lower alkyl group, or a lower alkoxy group. , Or a lower alkoxy group having a sulfo group, more preferably a hydrogen atom, a methyl group, a methoxy group, a 3-sulfopropoxy group, or a 4-sulfopropoxy group. As the substitution positions of Rg ₂ or Rg _3, the azo group substituted on the Ag ₁ side in the above formula (2) is used as the 1-position, and only the 2-position, the 5-position, the 2-position, the 5-position, and the 3-position are used. The 5th, 2nd and 6th positions, or the combination of the 3rd and 6th positions can be applied, but preferably only the 2nd position, only the 5th position, and the 2nd and 5th positions are preferable. Note that only the 2-position and the 5-position indicate that only the 2-position or the 5-position has one substituent other than the hydrogen atom.

Xg ₁ in the above formula (2) includes an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, and a substituent. Indicates a benzoyl group which may have a benzoyl group or a benzoylamino group which may have a substituent. 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. is there. The amino group which may have a substituent preferably has one or two selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, an amino group, and a lower alkylamino group. It is an amino group, more preferably an amino group having one or two hydrogen atoms, a methyl group and a sulfo group. The phenylamino group which may have a substituent is preferably one or 2 selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, an amino group, and a lower alkylamino 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 sulfo group, and an amino group. is there. The phenylazo group is preferably selected from the group consisting of a hydrogen atom, a hydroxy group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an amino group, a hydroxy group and a carboxyethylamino group. It is a phenylazo group having three. The benzoyl group which may have a substituent is preferably a benzoyl group having one substituent selected from the group consisting of a hydrogen atom, a hydroxy group, an amino group, and a carboxyethylamino group. The benzoylamino group which may have a substituent is preferably a benzoylamino group having one substituent selected from the group consisting of a hydrogen atom, a hydroxy 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 at the p-position with respect to the bond position indirectly bonded to the naphthalene skeleton represented by the formula (2). As a specific example, in the case of a phenylamino group, it is preferable that there is a substituent at the p-position with respect to the amino group.

The azo compound represented by the above formula (2) or a salt thereof is preferably the azo compound represented by the above formula (5) or a salt thereof because the performance is particularly improved.

In the above formula (5), Ag ₂ has the same meaning as Ag ₁ in the formula (2). Rg ₄ and Rg ₅ independently have the same meaning as Rg ₁ in the formula (3). Xg ₂ has the same meaning as Xg ₁ in the formula (2). P ₂ and p ₃ independently have the same meaning as p ₁ in equation (2). In particular, it is preferable that p ₂ and p ₃ are independently 1 or 2, respectively, in order to improve the polarization characteristics.

In the polarizing element, the content of the azo compound represented by the above formula (2) or a salt thereof is 0.01 to 5000 parts by mass with respect to 100 parts by mass of the content of the azo compound of the above formula (1). It is preferably 0.1 to 3000 parts by mass, 10 to 1000 parts by mass, and even 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 the methods described in, for example, Patent Documents 7 to 12, but is not limited thereto.

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

Specific examples of the azo compound represented by the above formula (2) are shown below in the form of a free acid.

By including the azo compound represented by the above formula (1) and the above formula (2) in combination, the polarizing element has a higher transmittance and a higher degree of polarization than the conventional achromatic polarizing plate. Achieves high-quality paper-like white, commonly known as paper white, when displayed in white, and achieves achromatic black when displayed in black, especially clear black with a high-class feel, and is more than conventional dye-based polarizing plates. It is possible to realize a polarizing plate having a high contrast.

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

In the above formula (6), Ay ₁ is a sulfo group, a carboxy group, a hydroxy group, a lower alkyl group, or a lower alkoxy group, and is preferably a sulfo group or a carboxy group. Ry _{1 to} Ry ₄ are lower alkoxy groups each independently having a hydrogen atom, a sulfo group, a lower alkyl group, a lower alkoxy group, and a sulfo group, preferably a hydrogen atom, a sulfo group, a lower alkyl group, and a lower alkoxy group. It is more preferably a hydrogen atom, a methyl group, or a methoxy group. k represents an integer of 1 to 3.

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

The azo compound represented by the above formula (6) particularly affects the transmittance at 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 affect the blue omission at the time of black display and the yellowing of white at the time of white display. The azo compound represented by the formula (6) improves the polarization characteristics (dichroism) of 400 to 500 nm while suppressing a decrease in the transmittance on the short wavelength side in the parallel position of the polarizing element, and is displayed in white. It is possible to further reduce the omission of yellowish and blue when displayed in black. By further containing the azo compound represented by the formula (6), the polarizing element exhibits more achromaticity by itself in the range of 35 to 66% of the simple substance transmittance after the luminosity factor correction, and is displayed in white. This is preferable because it expresses a high-quality paper-like white color and further improves the degree of polarization.

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 commercially available products can also be obtained.
Specific examples of the azo compound represented by the formula (6) include, for example, C.I. I. Direct Yellow 4, C.I. I. Direct Yellow 12, C.I. I. Direct Yellow 72, and C.I. I. There are, but are not limited to, Direct Orange 39 and azo compounds having a stilbene structure described in WO2007 / 138980 and the like.

Further specific examples of the azo compound represented by the formula (6) are given below. Examples of compounds are represented in the form of free acids.

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

The polarizing element contains an azo compound represented by the formula (1) and the formula (2), and can optionally further contain an azo compound represented by the formula (6). The polarizing element can have performances such as a * value and b * value, which are chromaticities in a preferable range described later, a single transmittance after correction of luminosity factor, and an average transmittance in a specific wavelength band. For example, the transmittance of each wavelength of the polarizing element alone can be made constant. Further, the transmittance can be made constant even in the parallel position of each wavelength, that is, an achromatic color can be provided in the hue of the parallel position when the absorption axes of the two polarizing elements are parallel. Further, the transmittance of each wavelength can be made constant at the same time even in the orthogonal position, that is, it is possible to provide an achromatic hue in the hue of the orthogonal position when the absorption axes of the two polarizing elements are orthogonal. From this, the polarization element of the present application contains the azo compounds represented by the formulas (1) and (2), and optionally the formula (6), so that the polarized light has high transmittance, high contrast, that is, high degree of polarization. Not only can it provide an element, but it can also provide a polarizing element that also has an achromatic hue.

It is preferable that the compounding ratio of the azo compound in the polarizing element is further adjusted so that the transmittance and the chromaticity are in the preferable ranges described later in the content of each of the azo compounds described above. The performance of the polarizing element varies not only with the compounding ratio of each azo compound in the polarizing element, but also with the degree of swelling and stretching ratio of the substrate on which the azo compound is adsorbed, the dyeing time, the dyeing temperature, the pH during dyeing, the influence of salts, and the like. It changes depending on various factors. Therefore, the blending ratio of each azo compound can be determined according to the degree of swelling of the base material, the temperature at the time of dyeing, the time, the pH, the type of salt, the concentration of salt, and the draw ratio.

(Transmittance after luminosity factor correction)
The transmittance after the luminosity factor correction is a transmittance corrected to the luminosity factor of the human eye, which is obtained according to JIS Z 8722: 2009. The transmittance of each wavelength used for correction is measured every 5 nm or 10 nm for each wavelength of 400 to 700 nm using a C light source (2 degree field) for a measurement sample (for example, a polarizing element or a polarizing plate). It can be obtained by measuring the spectral transmittance and correcting it to the visual sensitivity according to JIS Z 8722: 2009. As for the transmittance after the visual sensitivity correction, the single transmittance after the visual sensitivity correction when the polarizing element or the polarizing plate was measured by itself, the polarizing element, or two polarizing plates were used, and each absorption axis was made parallel. Parallel transmittance after correction of visibility when the transmittance at time is corrected to visibility, and transmittance when each absorption axis is orthogonal to each other using two polarizing elements or polarizing plates is used as visibility. There is orthogonal transmittance after correction of visual sensitivity when corrected.

(I) Difference in average transmittance between two wavelength bands It is preferable that the difference in average transmittance between specific wavelength bands of the above-mentioned polarizing element is not more than a predetermined value. The average transmittance is the average value of the transmittance of each wavelength in a specific wavelength band.

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

The transmittance obtained by measuring each wavelength in a state where two polarizing elements are stacked so as to be parallel to each other in the absorption axis direction (in bright display or white display) is measured in "parallel transmission" of each wavelength. Also called "rate". Further, the average transmittance of each wavelength from ○ nm to Δnm is also referred to as “AT _{○ − △} ”. Regarding the parallel transmittance of each wavelength of the polarizing element of the present invention, the difference between AT _420-480 and AT _520-590 is preferably 2.5% or less, more preferably 1.8% or less as an absolute value. , More preferably 1.5% or less, and particularly preferably 1.0% or less. Further, regarding the parallel transmittance of each wavelength, the difference between AT _520-590 and AT _600-640 is preferably 3.0% or less as an absolute value, more preferably 2.0% or less, still more preferably. It is 1.5% or less, particularly preferably 1.0% or less. Such a polarizing element can display a high-quality paper-like white color in a parallel position.

The transmittance obtained by measuring each wavelength in a state where two polarizing elements are stacked so that the absorption axis directions are orthogonal to each other (when displayed in black or when displayed in dark) is the "orthogonal transmission" of each wavelength. Also called "rate". Regarding the orthogonal position transmittance of each wavelength of the polarizing element of the present invention, the difference between AT _420-480 and AT _520-590 is 1.0% or less as an absolute value, and AT _520-590 and AT _600-640. The difference from is preferably 1.0% or less as an absolute value. Such a polarizing element can display an achromatic black color at an orthogonal position. Further, regarding the orthogonal position transmittance of each wavelength, the difference between AT _420-480 and AT _520-590 is preferably 0.6% or less, more preferably 0.3% or less, still more preferably 0. It is 1% or less. Regarding the orthogonal position transmittance, the difference between AT _520-590 and AT _600-640 as an absolute value is preferably 1.0% or less, more preferably 0.6% or less, still more preferably 0.3% or less, particularly. It is preferably 0.1%.

Further, the average transmittances of the single transmittance, the parallel position transmittance, and the orthogonal position transmittance at each wavelength of the wavelength band of 380 nm to 420 nm, 480 nm to 520 nm, and 640 nm to 780 nm are the above wavelength bands of 420 nm to 480 nm and 520 nm. When the average transmittance at ~ 590 nm and 600 nm to 640 nm is adjusted as described above, it is preferable that the average transmittance is adjusted to some extent, although the influence on the hue of the polarizing element is not large. For single transmittance of each _{wavelength, AT} is preferable that the difference is not more than 15% of the _380-420 and _{AT 420-480, AT 480-520} a difference between the _{AT 420-480} 15% or _{less, AT 480- It} is _preferable that the difference between ₅₂₀ and AT _520-590 is 15% or less, and the difference between AT _640-780 and AT _600-640 is 20% or less.

(II) Value of Single Transmittance After Luminosity Factor Correction The polarizing element preferably has a single transmittance of 35% to 66% after the luminosity factor correction. The single transmittance after the luminosity factor correction is the transmittance of one measurement sample (for example, a polarizing element or a polarizing plate) corrected to the luminosity factor according to JIS Z 8722: 2009. The performance of the polarizing plate is required to have a higher transmittance, but if the single transmittance after correction of the luminosity factor is 35% to 60%, the brightness can be expressed without discomfort even when used in a display device. Since the degree of polarization tends to decrease as the transmittance increases, the single transmittance after correction of luminosity factor is more preferably 37% to 50%, and even more preferably 38, from the viewpoint of the balance with the degree of polarization. % To 45%. If the single transmittance after luminosity factor correction exceeds 65%, the degree of polarization may decrease. However, when the bright transmittance of the polarizing element or a specific polarization performance or contrast is required, the luminosity factor is corrected. The single transmittance may exceed 65%.

(III) Average Transmittance in Specific Wavelength Band The polarizing element is _preferably AT _520-590 measured in a parallel position at 25% to 50%. When such a polarizing element is provided in a display device, it can be a clear display device that is bright and has high brightness. The transmittance of the wavelength band of 520 nm to 590 nm is one of the main wavelength bands based on the color matching function used in the calculation when showing a color in JIS Z 8781-4: 2013. In particular, each wavelength band of 520 nm to 590 nm is the wavelength band having the highest luminosity factor based on the color matching function, and the transmittance in this range is close to the transmittance that can be visually confirmed. Therefore, it is very important to adjust the transmittance in the wavelength band of 520 nm to 590 nm. The AT _520-590 measured in the parallel position is more preferably 28% to 45%, still more preferably 30% to 40%. Further, the degree of polarization of the polarizing element at this time may be 80% to 100%, preferably 90% to 100%, more preferably 97% to 100%, and further preferably 99% or more. Yes, particularly preferably 99.5% or more. It is preferable that the degree of polarization is high, but in the relationship between the degree of polarization and the degree of transmittance, it is necessary to adjust the degree of polarization to an appropriate degree depending on whether the degree of brightness or the degree of polarization (or contrast) is emphasized. Can be done.

(Saturation a * value and b * value)
The chromaticity a * value and b * value are values obtained at the time of measuring the transmittance of natural light according to JIS Z 8781-4: 2013. The object color display method defined in JIS Z 8781-4: 2013 corresponds to the object color display method defined by the International Commission on Illumination (abbreviation: CIE). The measurement of the chromaticity a * value and the b * value is performed by irradiating the measurement sample (for example, a polarizing element or a polarizing plate) with natural light. In the following, the chromaticity a * value and b * value required for one measurement sample are a * -s and b * -s, and the two measurement samples are arranged so that their absorption axis directions are parallel to each other. The chromaticity a * value and b * value required for the state (when displayed in white) are a * -p and b * -p, and the two measurement samples are arranged so that their absorption axis directions are orthogonal to each other (black display). The chromaticity a * value and b * value obtained for hour) are shown as a * -c and b * -c.

In the above-mentioned polarizing element, each of the absolute values of a * -s and b * -s is preferably 1.0 or less, and each of the absolute values of a * -p and b * -p is 2.0 or less. It is preferable to have. Such a polarizing element is a neutral color by itself, and can display high-quality white when displaying white. The absolute values of a * -p and b * -p of the polarizing element are more preferably 1.5 or less, still more preferably 1.0 or less. Further, in the polarizing element, each of the absolute values of a * -c and b * -c is preferably 2.0 or less, and more preferably 1.0 or less. Such a polarizing element can display achromatic black when displaying black. Even if there is a difference of 0.5 between the absolute values of the chromaticity a * value and the b * value, humans can perceive the difference in color, and some people may feel the difference in color greatly. Therefore, it is very important to control these values in the polarizing element. In particular, when the absolute values of a * -p, b * -p, a * -c, and b * -c are 1.0 or less, respectively, when white and black are displayed. A good polarizing plate can be obtained in which other colors can hardly be confirmed in black. It is possible to realize achromaticity in the parallel position, that is, a high-quality paper-like white color, and to realize a high-quality clear black color that is achromatic in the orthogonal position. However, the influence of the hue giving the black color of the display device is not limited to this, and in the absence of light (dark), the display device looks black even if it has a hue. Therefore, when the degree of polarization is high, that is, when the orthogonal position transmittance is low, the polarizing element can give black even if the absolute values of a * -c and b * -c are not 2.0 or less, respectively. As a result of our examination, when the orthogonal position transmittance at each wavelength of the wavelength band 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 about 97% or more, a * -c and b * It was found that it is preferable because black can be visually given regardless of the absolute value of −c. It is more preferable because black can be visually provided when the orthogonal position transmittance at each wavelength of the wavelength band 420 nm to 480 nm, 520 nm to 590 nm, and 600 nm to 640 nm is 0.6% or less or the degree of polarization is 98% or more. It is particularly preferable when the orthogonal position transmittance of each wavelength is 0.3% or less or the degree of polarization is 99% or more.

From the above, when two polarizing elements are stacked so as to be orthogonal to each other in the absorption axis direction, a preferable method for giving black to the hue is one of the following 1) to 3). Achieve by satisfying.
1) Transmittance of each wavelength obtained by measuring the state in which two polarizing elements are stacked so as to be orthogonal to each other in the absorption axis direction (when displayed in black or when displayed in dark) (hereinafter, ““ also referred to as the perpendicular position transmittance _"for.), as the difference between the absolute value of the _{aT 420-480} and _{aT 520-590,} not more than 1.0%, and _the difference between the _{aT 520-590} and _{aT 600-640} Is 1.0% or less as an absolute value 2) Each of the absolute values of a * -c and b * -c is 2.0 or less 3) Wavelength band 420 nm to 480 nm, 520 nm to 590 nm, and 600 nm to 640 nm, respectively. Orthogonal transmittance at wavelength is 1% or less or polarization degree is about 97% or more.

The polarizing element according to the present invention has achromaticity and a high degree of polarization by itself while having high contrast and high transmittance. Further, the polarizing element of the present invention can express high-quality paper-like white (paper white) when displayed in white, and express achromatic black, particularly high-quality clear black when displayed in black. Can be done. Until now, there has been no polarizing element having such high transmittance and achromaticity. The polarizing element of the present invention is also highly durable, particularly resistant to high temperatures and high humidity.

Further, since the polarizing element according to the present invention absorbs less light having a wavelength of 700 nm or more as compared with an iodine-based polarizing plate and Patent Document 3 which are generally used, heat is generated even when irradiated with light such as sunlight. It has the advantage of being less. For example, when the liquid crystal display is used outdoors, sunlight is applied to the liquid crystal display, and as a result, the polarizing element is also irradiated. Sunlight also has light having a wavelength of 700 nm or more, and includes near infrared rays having a heat generating effect. For example, a polarizing element using an azo compound as described in Example 3 of Japanese Patent Application Laid-Open No. 02-061988 generates a little heat because it absorbs near-infrared light having a wavelength of around 700 nm. Since the polarizing element absorbs very little near infrared rays, it generates less heat even when exposed to sunlight outdoors. The polarizing element of the present invention is excellent in that it generates less heat and therefore causes less deterioration.

<Manufacturing method of polarizing element>
Hereinafter, a specific method for producing a polarizing element will be described by taking as an example a case where an azo compound is adsorbed on a base material made of a polyvinyl alcohol-based resin. The method for manufacturing a polarizing element according to the present invention is not limited to the following manufacturing method.

(Preparation of original film)
The raw film can be produced by forming a polyvinyl alcohol-based resin. 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. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids and the like. The degree of saponification of the polyvinyl alcohol-based resin is usually preferably about 85 to 100 mol%, more preferably 95 mol% or more. The polyvinyl alcohol-based resin may be further modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can also be used. The degree of polymerization of the polyvinyl alcohol-based resin means the viscosity average degree of polymerization, which can be determined by a method well known in the art, and is usually preferably about 1,000 to 10,000, more preferably the degree of polymerization 1. , 500 to 6,000.

The method for forming the film of the polyvinyl alcohol-based resin is not particularly limited, and the film can be formed by a known method. In this case, the polyvinyl alcohol-based resin film may contain glycerin, ethylene glycol, propylene glycol, low molecular weight polyethylene glycol, or the like as a 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 film thickness of the raw film is not particularly limited, but is, for example, about 5 μm to 150 μm, preferably about 10 μm to 100 μm.

(Swelling process)
The raw film obtained as described above is subjected to a swelling treatment. The swelling treatment is preferably carried out by immersing the raw film in a solution at 20 to 50 ° C. for 30 seconds to 10 minutes. The solution is preferably water. The draw ratio is preferably adjusted to 1.00 to 1.50 times, more preferably 1.10 to 1.35 times. When the time for manufacturing the polarizing element is shortened, the swelling treatment can be omitted because the raw film swells even during the dyeing treatment described later.

(Dyeing process)
In the dyeing step, the resin film obtained by swelling the raw film is adsorbed and impregnated with the azo compound. When the swelling step is omitted, the swelling treatment of the raw film can be performed at the same time in the dyeing step. Since the process of adsorbing and impregnating the azo compound is a step of coloring the resin film, it is a dyeing step.

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

The dyeing step is not particularly limited as long as it is a method of adsorbing and impregnating the dye on the resin film, but is preferably performed by immersing the resin film in the dyeing solution, and is performed by applying the dyeing solution to the resin film. You can also do it. Each azo compound in the dyeing solution can be adjusted, for example, in the range of 0.001 to 10% by mass.

The solution temperature 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 it is preferably adjusted to 30 seconds to 20 minutes, more preferably 1 to 10 minutes.

The dyeing solution may further contain a dyeing aid, if necessary, in addition to the azo compound. Examples of the dyeing aid include sodium carbonate, sodium hydrogencarbonate, sodium chloride, sodium sulfate, anhydrous sodium sulfate, sodium tripolyphosphate and the like. The content of the dyeing aid can be adjusted at an arbitrary concentration depending on the time and temperature depending on the dyeability of the dye, but the content of each is preferably 0.01 to 5% by mass, preferably 0.1 to 5% by mass in the dyeing solution. 2% by mass is more preferable.

(Washing step 1)
After the dyeing step, a washing step (hereinafter, also referred to as “cleaning step 1”) can be performed before entering the next step. The dyeing and cleaning step 1 is a step of cleaning the dyeing solution adhering to the surface of the resin film in the dyeing step. By performing the washing step 1, it is possible to suppress the transfer of the dye into the liquid to be treated next. In the cleaning step 1, water is generally used as the cleaning liquid. The cleaning method is preferably immersed in a cleaning liquid, but cleaning can also be performed by applying the cleaning liquid to a 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 liquid in the cleaning step 1 needs to be a temperature at which the material constituting the resin film (for example, a hydrophilic polymer, here, a polyvinyl alcohol-based resin) does not dissolve. Generally, it is washed at 5 to 40 ° C. However, even if the cleaning step 1 is not performed, there is no problem in performance, so that the cleaning step can be omitted.

(Step of adding a cross-linking agent and / or a water resistant agent)
After the dyeing step or the washing step 1, a step of adding a cross-linking agent and / or a water resistant agent can be performed. The method of impregnating the resin film with a cross-linking agent and / or a water resistant agent is preferably to immerse the resin film in the treatment solution, but the treatment solution may be applied or applied to the resin film. The treatment solution contains at least one cross-linking agent and / or water resistant agent 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.

Examples of the cross-linking agent include a boron compound such as boric acid, borax or ammonium borate, a polyvalent aldehyde such as glioxal or glutaaldehyde, a polyvalent isocyanate compound such as biuret type, isocyanurate type or block type, and titanium oxy. Titanium-based compounds such as sulfate can be used, but ethylene glycol glycidyl ether, polyamide epichlorohydrin and the like can also be used. Examples of the water resistant agent include succinic peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, ammonium chloride, magnesium chloride and the like, but boric acid is preferable. Used. Water is preferred but not limited as the solvent for the cross-linking agent and / or the water resistant agent. The concentration of the cross-linking agent and / or the water-resistant agent can be appropriately determined by those skilled in the art depending on the type thereof, but in the case of boric acid as an example, the concentration in the treatment solution is 0.1 to 6.0 mass by mass. % Is preferable, and 1.0 to 4.0% by mass is more preferable. However, it is not essential to contain a cross-linking agent and / or a water-resistant agent, and if it is desired to shorten the time and the cross-linking treatment or the water-resistant treatment is unnecessary, this treatment step may be omitted. ..

(Stretching process)
After performing the dyeing step, the washing step 1, or the step of adding a cross-linking agent and / or a water resistant agent, a stretching step is performed. The stretching step is performed by stretching the resin film uniaxially. The stretching method may be either a wet stretching method or a dry stretching method. The draw ratio is preferably 3 times or more, more preferably 4 to 8 times, and particularly preferably 5 to 7 times.

In the case of the wet stretching method, it is preferable to stretch the resin film in water, a water-soluble organic solvent, or a mixed solution thereof. It is preferable to carry out the stretching treatment while immersing in a solution containing at least one cross-linking agent and / or water resistant agent. As the cross-linking agent and the water-resistant agent, the same ones as described above for the step of containing the cross-linking agent and / or the water-resistant agent can be used. The concentration of the cross-linking agent and / or the water resistant agent in the solution in the stretching step is preferably, for example, 0.5 to 15% by mass, more preferably 2.0 to 8.0% by mass. The stretching temperature is preferably 40 to 60 ° C., more preferably 45 to 58 ° C. The stretching time is usually 30 seconds to 20 minutes, but more preferably 2 to 5 minutes. The wet stretching step can be carried out in one step, but it can also be carried out by multi-step stretching in two or more steps.

In the case of the dry stretching method, when the stretching heating medium is an air medium, it is preferable to stretch the resin film at a temperature of the air medium from room temperature to 180 ° C. Further, the humidity is preferably in an atmosphere of 20 to 95% RH. Examples of the heating method include an inter-roll zone stretching method, a roll heating stretching method, a pressure stretching method, an infrared heating stretching method, and the like, but the stretching method is not limited. The stretching step can be carried out in one step, but can also be carried out by multi-step stretching in two or more steps.

(Washing step 2)
After the stretching step, a cross-linking agent and / or a water resistant agent may precipitate on the surface of the resin film, or foreign matter may adhere to the surface of the resin film. Can be referred to). The washing time is preferably 1 second to 5 minutes. The cleaning method is preferably to immerse the resin film in the cleaning liquid, but the solution can also be applied to the resin film or washed by coating. Water is preferable as the cleaning liquid. The cleaning treatment can be performed in one stage, or the multi-stage treatment in two or more stages can be performed. The solution temperature in the washing step is not particularly limited, but is usually 5 to 50 ° C, preferably 10 to 40 ° C.

The treatment liquid or its solvent used in the treatment steps up to this point includes water, for example, dimethyl sulfoxide, N-methylpyrrolidone, methanol, ethanol, propanol, isopropyl alcohol, glycerin, ethylene glycol, propylene glycol, diethylene glycol, and triethylene. Examples thereof include alcohols such as glycol, tetraethylene glycol or trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine, but the present invention is not limited thereto. The treatment liquid or its solvent is most preferably water. Moreover, these treatment liquids or the solvent thereof can be used individually by 1 type, but a mixture of 2 or more types can also be used.

(Drying process)
After the stretching step or the washing step 2, a drying step of the resin film is performed. The drying treatment can be carried out by natural drying, but in order to further improve the drying efficiency, it can be carried out by compression with a roll, removal of moisture on the surface with an air knife, a water absorbing roll, etc., and / or by air drying. You can also do it. As the drying treatment temperature, the drying treatment is preferably performed at 20 to 100 ° C., and more preferably 60 to 100 ° C. The drying treatment time is, for example, 30 seconds to 20 minutes, but is preferably 5 to 10 minutes.

In the method for producing a polarizing element, the degree of swelling of the base material in the swelling step, the compounding ratio of each azo compound in the dyeing step, the temperature of the dyeing solution, the pH, the type and concentration of salts such as sodium chloride, Glauber's salt, and sodium tripolyphosphate, 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), and of (vi) and (vii). It is more preferable to adjust so as to further satisfy the conditions.
(I) Regarding the parallel transmittance, the difference between AT _420-480 and AT _520-590 is 2.5 or less as an absolute value, and the difference between AT _520-590 and AT _600-640 is 2.0 as an absolute value. It becomes as follows.
(Ii) Regarding the orthogonal position transmittance, the difference between AT _420-480 and AT _520-590 is 1.0 or less as an absolute value, and the difference between AT _520-590 and AT _600-640 is 1.0 as an absolute value. It becomes as follows.
(Iii) The single transmittance after the luminosity factor correction is 35% to 45%.
(Iv) Each of the absolute values of the a * value and the b * value is 1.0 or less for the polarizing element alone and 2.0 or less for both the parallel positions.
(V) Each of the absolute values of the a * value and the b * value measured at the orthogonal position is 2 or less.
(Vi) AT _520-590 is 28 to 45% for the parallel transmittance of each wavelength.
(Vii) single axis transmittance of each wavelength, or in the perpendicular position transmittance of each _{wavelength, AT 380-420} a difference between the _{AT 420-480} 15% or _less, the difference between the _{AT 480-520} and _{AT 420-480} 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 containing at least a combination of azo compounds represented by the formulas (1) and (2) or optionally a combination of azo compounds represented by the formula (6) can be produced. Such a polarizing element has a higher transmittance and a higher degree of polarization than a conventional polarizing element, but is like high-quality paper when two polarizing elements are stacked so as to be parallel to each other in the absorption axis direction. It is a hue that can express white color and has a neutral color (neutral gray) by itself. Further, the polarizing element exhibits a high-quality achromatic black when two polarizing elements are stacked so as to be orthogonal to each other in the absorption axis direction. Further, the polarizing element has high durability against high temperature and high humidity.

<Polarizer>
The polarizing plate according to 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 and handleability of the polarizing element.

The transparent protective layer is a protective film formed by using a transparent substance. The protective film is a film having a layered shape capable of maintaining the shape of the polarizing element, and is preferably a plastic or the like having excellent transparency, mechanical strength, thermal stability, moisture shielding property, and the like. An equivalent function may be provided by forming a layer equivalent to this. Examples of plastics constituting the protective film include thermoplastic resins such as polyester resins, acetate resins, polyether sulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins and acrylic resins. Examples thereof include films obtained from thermosetting resins such as acrylic, urethane, acrylic urethane, epoxy and silicone, or ultraviolet curable resins, and among these, the polyolefin resin is an amorphous polyolefin resin. However, a resin having a polymerization unit of a cyclic polyolefin such as a norbornene-based monomer or a polycyclic norbornene-based monomer can be mentioned. In general, it is preferable to select a protective film that does not impair the performance of the polarizing element after laminating the protective film, and as such a protective film, triacetyl cellulose (TAC) made of a cellulose acetate resin and norbornene are particularly preferable. .. Further, the protective film may be subjected to a hard coat treatment, an antireflection treatment, a sticking prevention / diffusion treatment, an antiglare treatment, or the like, as long as the effects of the present invention are not impaired. The thickness of the transparent protective layer is usually preferably 10 to 200 μm.

It is preferable that the polarizing plate further includes an adhesive layer for adhering the transparent protective layer to the polarizing element between the transparent protective layer and the polarizing element. The adhesive constituting the adhesive layer is not particularly limited. Examples thereof include polyvinyl alcohol-based adhesives, urethane emulsion-based adhesives, acrylic-based adhesives, polyester-isocyanate-based adhesives, and the like, and polyvinyl alcohol-based adhesives are preferable. Examples of the polyvinyl alcohol-based adhesive include, but are not limited to, Gosenol NH-26 (manufactured by Nippon Synthetic Co., Ltd.) and Exevar RS-2117 (manufactured by Kuraray). A cross-linking agent and / or a water resistant agent can be added to the adhesive. As the polyvinyl alcohol-based adhesive, it is preferable to use a maleic anhydride-isobutylene copolymer, and if necessary, an adhesive mixed with a cross-linking agent can be used. Examples of the maleic anhydride-isobutylene copolymer include Isovan # 18 (manufactured by Kuraray), Isoban # 04 (manufactured by Kuraray), Ammonia-modified Isovan # 104 (manufactured by Kuraray), and Ammonia-modified Isovan # 110 (manufactured by Kuraray). ), Imidized Isovan # 304 (manufactured by Kuraray), Imidized Isovan # 310 (manufactured by Kuraray) and the like. A water-soluble polyvalent epoxy compound can be used as the cross-linking agent at that time. Examples of the water-soluble polyvalent epoxy compound include Denacol EX-521 (manufactured by Nagase Chemtech Co., Ltd.) and Tetrat-C (manufactured by Mitsui Gas Chemicals Co., Ltd.). Further, as an adhesive other than the polyvinyl alcohol-based resin, known adhesives such as urethane-based, acrylic-based, and epoxy-based adhesives can also be used. In particular, it is preferable to use polyvinyl alcohol modified with an acetoacetyl group, and further, it is preferable to use a polyhydric aldehyde as a cross-linking agent thereof. Further, for the purpose of improving the adhesive strength or water resistance of the adhesive, additives such as zinc compounds, chlorides and iodides are contained alone or simultaneously at a concentration of about 0.1 to 10% by mass. You can also. Additives to the adhesive are not particularly limited and can be appropriately selected by those skilled in the art. A polarizing plate can be obtained by bonding the transparent protective layer and the polarizing element with an adhesive and then drying or heat-treating at an appropriate temperature.

In some cases, when the polarizing element or the polarizing plate is attached to a display device such as a liquid crystal or an organic electroluminescence (commonly known as OLED or OEL), the viewing angle is improved and / or the surface of the protective layer or film which becomes an unexposed surface later. Various functional layers for improving contrast, layers or films having brightness improving properties can also be provided. The various functional layers are, for example, layers or films that control the phase difference. The polarizing plate is preferably attached to these films and display devices with an adhesive.

The polarizing element or the polarizing plate may be provided with various known functional layers such as an AR layer (antireflection layer), an antiglare layer, and a hard coat layer on the transparent protective layer or the exposed surface of the film. A coating method is preferable for producing layers having various functions, but a film having the functions can also be attached via an adhesive or an adhesive.

Examples of the hard coat layer include an acrylic or polysiloxane-based hard coat layer and a urethane-based protective layer. Further, the AR layer can be expected to further improve the single plate light transmittance. The AR layer can be formed by depositing or sputtering a substance such as silicon dioxide or titanium oxide, or by applying a thin coating of a fluorine-based substance.

In some cases, when the polarizing element or the polarizing plate is attached to a display device such as a liquid crystal or an organic electroluminescence (commonly known as OLED or OEL), the viewing angle is improved and / or the surface of the transparent protective layer or film which becomes a non-exposed surface is improved. Alternatively, various functional layers for improving contrast, and a layer or film having brightness improving property may be provided. The various functional layers are, for example, a layer or a film that controls the phase difference (hereinafter, also referred to as a "phase difference plate"). By attaching a retardation plate, the polarizing plate of the present invention can also be used as an elliptical polarizing plate. The polarizing plate is preferably attached to these films and display devices with an adhesive.

The polarizing plate according to the present invention can realize achromaticity while having high transmittance and high degree of polarization, and can express high-quality paper-like white color when displayed in white, and is black. It is a highly durable polarizing plate that can express a neutral black color when displayed.

<Display device>
The polarizing element or polarizing plate of the present invention is provided with a protective layer or a functional layer and a transparent support such as glass, crystal, or sapphire, if necessary, and is provided with a liquid crystal projector, a calculator, a clock, a notebook computer, a word processor, a liquid crystal television, or the like. It is applied to polarized lenses, polarized glasses, car navigation systems, and indoor and outdoor measuring instruments and indicators.

In particular, the polarizing element or polarizing plate of the present invention is suitably used for a liquid crystal display device, for example, a reflective liquid crystal display device, a transflective liquid crystal display device, and an organic electroluminescence device other than the liquid crystal display device. The liquid crystal display device using the polarizing element or the polarizing plate of the present invention can express high-quality paper-like white and neutral black. Further, the liquid crystal display device is a liquid crystal display device having high durability, high reliability, high contrast in the long term, and high color reproducibility.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. The% in the example is based on mass unless otherwise specified.

[Example 1]
A polyvinyl alcohol film (VF-PS # 7500 manufactured by Kuraray Co., Ltd.) having an average degree of polymerization of 2400 with a saponification degree of 99% or more was immersed in warm water at 45 ° C. for 2 minutes, and a swelling treatment was applied to increase the stretching ratio to 1.30 times. .. 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, 0.105 parts by mass of the compound of formula (1-4), 0 of the compound of formula (2-11). The swollen film was immersed in a dyeing solution at 45 ° C. containing .22 parts by mass for 7 minutes and 30 seconds to allow the film to contain an azo compound. The obtained film was immersed in an aqueous solution at 40 ° C. containing 20 g / l of boric acid (manufactured by Societa Chemica Larderello s.pa.) for 1 minute. The film after immersion was stretched 5.0 times in an aqueous solution at 50 ° C. containing 30.0 g / l of boric acid for 5 minutes. The obtained film was washed by immersing it in water at 25 ° C. for 20 seconds while maintaining its tension. The washed film was dried at 70 ° C. for 9 minutes to obtain a polarizing element. An alkali-treated triacetyl cellulose film (ZRD-manufactured by Fuji Photo Film Co., Ltd.) was prepared by dissolving polyvinyl alcohol (NH-26 manufactured by Nippon Vinegar Vipovar Co., Ltd.) in water at 4% of this polarizing element as an adhesive. 60) was laminated to obtain a polarizing plate. The obtained polarizing plate maintains the optical performance of the polarizing element, particularly the single transmittance of each wavelength, the parallel position transmittance of each wavelength, the orthogonal position transmittance of each wavelength, the hue, the degree of polarization, and the like. It was. This polarizing plate was used as the measurement sample of Example 1.

[Example 2]
The swollen film contains 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous glass, 0.15 parts by mass of the compound of formula (1-18), (2-12). The compound of the above compound was treated in a staining solution at 45 ° C. containing 0.28 parts by mass and 0.05 parts by mass of the compound of the formula (6-1) for 6 minutes in the same manner as in Example 1 except that the azo compound was contained. To prepare a polarizing plate.

[Example 3]
The swollen film contains 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous glass, 0.17 parts by mass of the compound of formula (1-22), and formula (2-20). ) Was treated in a staining solution at 45 ° C. containing 0.28 parts by mass and 0.11 parts by mass of the compound of formula (6-1) for 5 minutes and 30 seconds, except that the azo compound was contained. A polarizing plate was produced in the same manner as in the above.

[Example 4]
The swollen film contains 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous glass, 0.145 parts by mass of the compound of formula (1-3), and formula (2-12). ) Was treated in a staining solution at 45 ° C. containing 0.28 parts by mass and 0.24 parts by mass of the compound of the formula (6-1) for 6 minutes and 15 seconds, except that the azo compound was contained. A polarizing plate was produced in the same manner as in the above.

[Example 5]
The swollen film contains 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous glass, 0.145 parts by mass of the compound of formula (1-4), and formula (2-12). ) Was treated in a staining solution at 45 ° C. containing 0.28 parts by mass and 0.255 parts by mass of the compound of formula (6-1) for 6 minutes and 15 seconds, except that the azo compound was contained. A polarizing plate was produced in the same manner as in the above.

[Example 6]
The swollen film contains 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous Glauber's salt, 0.165 parts by mass of the compound of formula (1-4), and formula (2-13). ) Was treated for 6 minutes in a dyeing solution at 45 ° C. containing 0.31 parts by mass and 0.295 parts by mass of the compound of the formula (6-1), and the same as in Example 1 except that the azo compound was contained. A polarizing plate was prepared.

[Example 7]
The swollen film contains 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous glass, 0.155 parts by mass of the compound of formula (1-10), and formula (2-12). ) Was treated in a staining solution at 45 ° C. containing 0.28 parts by mass and 0.265 parts by mass of the compound of the formula (6-1) for 6 minutes and 30 seconds, except that the azo compound was contained. A polarizing plate was produced in the same manner as in the above.

[Example 8]
The swollen film contains 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous glass, 0.155 parts by mass of the compound of formula (1-8), and formula (2-5). ) Was treated in a staining solution at 45 ° C. containing 0.28 parts by mass and 0.265 parts by mass of the compound of the formula (6-1) for 7 minutes and 15 seconds, except that the azo compound was contained. A polarizing plate was produced in the same manner as in the above.

[Example 9]
The swollen film contains 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous glass, 0.155 parts by mass of the compound of formula (1-8), and formula (2-10). ) Was treated in a staining solution at 45 ° C. containing 0.28 parts by mass and 0.265 parts by mass of the compound of formula (6-1) for 7 minutes, and the same as in Example 1 except that the azo compound was contained. To prepare a polarizing plate.

[Example 10]
The swollen film contains 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous glass, 0.155 parts by mass of the compound of formula (1-8), and formula (2-12). ) Was treated in a staining solution at 45 ° C. containing 0.30 parts by mass and 0.275 parts by mass of the compound of formula (6-1) for 7 minutes, and the same as in Example 1 except that the azo compound was contained. To prepare a polarizing plate.

[Example 11]
The swollen film contains 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous glass, 0.155 parts by mass of the compound of formula (1-8), and formula (2-9). ) Was treated in a staining solution at 45 ° C. containing 0.30 parts by mass and 0.275 parts by mass of the compound of formula (6-1) for 7 minutes, and the same as in Example 1 except that the azo compound was contained. To prepare a polarizing plate.

[Example 12]
The swollen film contains 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous glass, 0.18 parts by mass of the compound of formula (1-4), and formula (2-3). ) Was treated in a staining solution at 45 ° C. containing 0.57 parts by mass and 0.26 parts by mass of the compound of formula (6-1) for 7 minutes, and the same as in Example 1 except that the azo compound was contained. To prepare a polarizing plate.

[Example 13]
The swollen film contains 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous glass, 0.18 parts by mass of the compound of formula (1-4), and formula (2-4). ) Was treated in a staining solution at 45 ° C. containing 0.45 parts by mass and 0.26 parts by mass of the compound of formula (6-1) for 9 minutes, and the same as in Example 1 except that the azo compound was contained. To prepare a polarizing plate.

[Example 14]
In Example 5, the compound of formula (6-2) of 0.23 parts by mass was treated with a staining solution in a staining solution for 6 minutes and 15 seconds instead of the compound of formula (6-1) of 0.255 parts by mass, and the azo compound was used. A polarizing plate was produced in the same manner as in Example 1 except that it contained.

[Example 15]
In Example 5, 0.255 parts by mass of C.I. is replaced with 0.255 parts by mass of the compound of formula (6-1). I. Polarized Orange 72 was treated with a staining solution for 6 minutes to prepare a polarizing plate in the same manner as in Example 1 except that an azo compound was contained.

[Example 16]
In Example 5, 0.25 parts by mass of C.I. is replaced with 0.255 parts by mass of the compound of formula (6-1). I. Direct Yellow 28 was treated with a stain solution for 6 minutes and 15 seconds to prepare a polarizing plate in the same manner as in Example 1 except that an azo compound was contained.

[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 a neutral gray color, was obtained and used as a measurement sample.

[Comparative Example 2]
As a general dye-based polarizing plate, a neutral gray dye-based polarizing plate SHC-128 manufactured by Polatechno Co., Ltd., which has a high contrast, was obtained and used as a measurement sample.

[Comparative Examples 3 to 8]
According to the production method of Comparative Example 1 of Patent Document 13, however, the iodine content time was set to 5 minutes and 30 seconds in Comparative Example 3, 4 minutes and 45 seconds in Comparative Example 4, 4 minutes and 15 seconds in Comparative Example 5, and 3 in Comparative Example 6. The time was 30 minutes, 30 seconds, 4 minutes and 00 seconds in Comparative Example 7, and 5 minutes and 15 seconds in Comparative Example 8, and an iodine-based polarizing plate, that is, a polarizing plate containing no azo compound was prepared and used as a measurement sample.

[Comparative Example 9]
An iodine-based polarizing plate SKW-18245P manufactured by Polatechno Co., Ltd., which shows a paper white color in a parallel position, was obtained and used as a measurement sample.

[Comparative Examples 10 and 11]
Permeation almost the same as that of Example 1 in the same manner as in Example 1 of the present application, except that only the aqueous solution (staining solution) containing the azo compound in Example 1 has the same composition as that of Example 1 of Patent Document 3. A polarizing plate was prepared by adjusting the time for immersing the swollen film in the aqueous solution so as to have a ratio and adding an azo compound.

[Comparative Example 12]
In Example 5, instead of the compound of the formula (1-4), the azo compound described in Patent Document 14 Synthesis Example 1 was contained in the staining solution in the same amount, and the azo compound was contained in the dyeing solution. A polarizing plate was prepared in the same manner.

[Comparative Example 13]
In Example 5, instead of the compound of formula (1-4), C.I. I. A polarizing plate was prepared in the same manner as in Example 1 except that Direct Red 4BH was contained in the staining solution in the same amount and an azo compound was contained.

[Comparative Example 14]
A polarizing plate was produced as in Example 1 of Patent Document 15 relating to a dye-based polarizing plate.

[Comparative Example 15]
A polarizing plate was produced as in Example 3 of Patent Document 16 relating to a dye-based polarizing plate.

[Comparative Example 16]
A polarizing plate was produced as in Example 1 of Patent Document 17 relating to a dye-based polarizing plate.

[Comparative Example 17]
Example 15 No. of Patent Document 18 relating to a dye-based polarizing plate. A polarizing plate was prepared as described in 1.

[Comparative Example 18]
In Example 5, 0.98 parts by mass of C.I., which is an azo compound having the same color and a ureido skeleton, instead of the compound of the formula (1-4). I. A polarizing plate was produced in the same manner as in Example 1 except that the transmittance of each wavelength at the orthogonal position was adjusted to be substantially constant and the color was black using Direct Red 80.

[Comparative Example 19]
In Example 5, 0.45 parts by mass of C.I., which is an azo compound having a dichroic dianisidine skeleton of the same color instead of the compound of the formula (2-12). I. A polarizing plate was produced using Direct Blue 6 in the same manner as in Example 1 except that the transmittance of each wavelength at the orthogonal position was designed to be substantially constant and the color was black.

[Evaluation method]
The measurement samples obtained in Examples 1 to 16 and Comparative Examples 1 to 19 were evaluated as follows.
(A) Single transmittance Ts of each wavelength, parallel transmittance Tp of each wavelength, and orthogonal transmittance Tc of each wavelength.
The single transmittance Ts, the parallel position transmittance Tp, and the orthogonal position transmittance Tc of each wavelength of each measurement sample were measured using a spectrophotometer (“U-4100” manufactured by Hitachi, Ltd.). Here, the simple substance transmittance Ts of each wavelength is the transmittance of each wavelength when the measurement sample is measured by one sheet. The parallel transmittance Tp of each wavelength is the spectral transmittance of each wavelength measured by superimposing two measurement samples so that their absorption axis directions are parallel to each other. The orthogonal position transmittance Tc of each wavelength is a spectral transmittance measured by superimposing two polarizing plates so that their absorption axes are orthogonal to each other. Measurements were made over wavelengths of 400-700 nm. The average value of each wavelength at 420 to 480 nm, the average value of each wavelength at 520 to 590 nm, and each at 600 to 640 nm of the parallel position transmittance Tp and the orthogonal position transmittance Tc obtained from the results obtained by the measurement. The average value of the wavelength is shown in Table 1.

(B) Single transmittance Ys after luminosity factor correction, parallel transmittance Yp after luminosity factor correction, and orthogonal transmittance Yc after luminosity factor correction.
The single transmittance Ys (%) after the luminosity factor correction, the parallel position transmittance Yp (%) after the luminosity factor correction, and the orthogonal position transmittance Yc (%) after the luminosity factor correction were obtained for each measurement sample. The single transmittance Ys (%) after the visual sensitivity correction, the parallel position transmittance Yp (%) after the visual sensitivity correction, and the orthogonal position transmittance Yc (%) after the visual sensitivity correction are in the wavelength region of 400 to 700 nm. JIS Z 8722: 2009 for each of the above-mentioned single transmittance Ts of each wavelength, the parallel position transmittance Tp of each wavelength, and the orthogonal position transmittance Tc of each wavelength obtained at predetermined wavelength intervals dλ (here, 5 nm). It is the transmittance corrected to the visual sensitivity according to. Specifically, the simple substance transmittance Ts of each wavelength, the parallel position transmittance Tp of each wavelength, and the orthogonal position transmittance Tc of each wavelength were substituted into the following equations (V to VII) to calculate each. In the following equations (V to VII), Pλ represents the spectral distribution of standard light (C light source), and yλ represents the two-degree visual field color matching function. The results are shown in Table 1.

(C) Contrast Contrast by calculating the ratio (Yp / Yc) of the parallel transmittance after luminosity factor correction and the orthogonal luminosity factor after luminosity factor correction, which are measured using two identical measurement samples. (CR) was calculated. The results are shown in Table 1.

(D) Absolute value of the difference in the average transmittance of each wavelength in the two wavelength bands Table 2 shows the parallel transmittance Tp of each wavelength of each measurement sample and the orthogonal transmittance Tc of each wavelength of 520 to 520. The absolute value of the difference between the average value of each wavelength at 590 nm and the average value of each wavelength at 420 to 480 nm is shown, and the difference between the average value of each wavelength at 520 to 590 nm and the average value of each wavelength at 600 to 640 nm. Indicates the absolute value.

As shown in Tables 1 and 2, the parallel transmittance Tp of each wavelength of the measurement samples of Examples 1 to 16 has an average value of 30% or more at 520 to 590 nm and has a high transmittance. It was. Further, regarding the parallel transmittance Tp of each wavelength, the difference between the average value of each wavelength at 420 to 480 nm and the average value of each wavelength at 520 to 590 nm is 2.5% or less as an absolute value, and 520. The difference between the average value of each wavelength at ~ 590 nm and the average value of each wavelength at 600 to 640 nm was 3.0% or less as an absolute value, both of which were very low values. Further, in the orthogonal position transmittance Tc of each wavelength, the difference between the average value of each wavelength at 420 to 480 nm and the average value of each wavelength at 520 to 590 nm is 1.0% or less as an absolute value, and 520. The difference between the average value of each wavelength at ~ 590 nm and the average value of each wavelength at 600 to 640 nm was 1.0% or less as an absolute value, both of which were very low values. Therefore, it was shown that the measurement samples obtained in Examples 1 to 16 had almost constant average transmittance at each wavelength in each of the parallel position and the orthogonal position.
On the other hand, in the measurement samples of Comparative Examples 1 to 9 and Comparative Examples 14 to 19, the absolute value of the difference in the average value between the wavelength bands of the parallel transmittance Tp of each wavelength shown in Table 2 and each wavelength. At least one of the absolute values of the difference between the average values of the orthogonal position transmittance Tc between the wavelength bands showed a high value.

Further, when comparing Examples 1 to 16 and Comparative Examples 10 to 13 in which the single transmittance after the luminosity factor correction is 39 to 42%, the contrast of Comparative Examples 10 to 13 is 27 to 139. The contrast of Examples 1 to 16 was 180 or more, and particularly when comparing Example 5 and Comparative Example 12, the present application had a contrast as high as about 6 times. As described above, it can be seen that the polarizing plate of the present application has high performance.

(E) Polarization degree ρy after luminosity factor correction
The degree of polarization ρy of each measurement sample after luminosity factor correction was obtained by substituting the parallel position transmittance Yp after luminosity factor correction and the orthogonal position transmittance Yc after luminosity factor correction into the following equations. The results are shown in Table 3.

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

(F) Luminous 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 transmittance Tp of each wavelength, and at each wavelength. The chromaticity a * value and b * value at each of the orthogonal position transmittance Tc measurements were measured. For the measurement, the above spectrophotometer was used, and both the transmitted color and the reflected color were incident from the outdoor side and measured. A C light source was used as the 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 have a single transmittance Ts, a parallel transmittance Tp, and an orthogonal transmittance, respectively. It corresponds to the chromaticity a * value and b * value at the time of Tc measurement, respectively.

(G) Observation of color For each measurement sample, two identical measurement samples were placed on a white light source in parallel and orthogonal positions, and the colors observed at that time were investigated. The observations were made visually by 10 observers, and Table 3 shows the most observed colors. In Table 3, the colors in the parallel position mean the colors in which two identical samples are stacked so that their absorption axis directions are parallel to each other (when displayed in white), and the colors in the orthogonal position are the same. It means the color in a state where two samples are stacked so that their absorption axis directions are orthogonal to each other (when displayed in black). Basically, the polarized color is "white" in the parallel position and "black" in the orthogonal position, but in the embodiment, for example, yellowish white is "yellow" and bluish purple. Black with a tinge is indicated as "blue-purple".

As shown in Table 3, the measurement samples of Examples 1 to 16 had a single transmittance of 35% or more after correction of luminosity factor. It was found that the measurement samples of Examples 1 to 16 showed a high degree of polarization of 99% or more while having a high transmittance, and could sufficiently express white and black. Further, in the measurement samples of Examples 1 to 16, the absolute value of each of a * -s, b * -s, and a * -p is 1.0 or less, and the absolute value of b * -p is 2.0 or less. It showed a very low value. The measurement samples of Examples 1 to 16 expressed a high-quality paper-like white color in a parallel position even when visually observed. Further, since the orthogonal position transmittance at each wavelength of the wavelength band 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 about 97% or more, black is expressed. On the other hand, in Comparative Examples 1 to 9 and Comparative Examples 14 to 19, at least one of a * -s, b * -s, a * -p, b * -p, a * -c and b * -c is used. When it showed a high value or when the orthogonal position transmittance was 1% or more as in Comparative Example 9, it was not achromatic in the parallel position or the orthogonal position when visually observed.

From the above, the polarizing element of the present invention can express high-quality paper-like white color in parallel position while maintaining high single-unit transmittance and parallel-position transmittance, and is high-quality without coloring by itself. It was shown to be a hue with a neutral color (achromatic neutral gray). Further, it can be seen that the polarizing element of the present invention maintains a single transmittance after high luminosity factor correction, exhibits achromaticity in a parallel position, and also has a high degree of polarization. Further, it can be seen that the polarizing element of the present invention makes it possible to obtain a polarizing element showing a high-quality achromatic black at an orthogonal position.

(H) Durability test The measurement samples of Examples 1 to 16 and Comparative Examples 3 to 9 were applied to an environment of 85 ° C. and a relative humidity of 85% RH for 240 hours. As a result, no change in transmittance or hue was observed in the measurement samples of Examples 1 to 16. On the other hand, in Comparative Examples 3 to 9, the degree of polarization decreased by 10% or more, b * -c became lower than -10, and the apparent color changed significantly to blue, and in particular, the two measurement samples were placed at orthogonal positions. When placed (when displayed in black), it developed a large blue color. Therefore, it was found that Examples 1 to 16 have high durability.

From the above results, the polarizing element according to the present invention has high transmittance and high degree of polarization, is achromatic in both white display and black display, and exhibits high-quality white color particularly in white display. It is an achromatic polarizing element and an achromatic polarizing plate and a display device using the same, and is extremely useful.

Claims (16)

A polarizing element containing 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, Ar ₁ represents a phenyl group having a substituent or a naphthyl group having a substituent, and Rr _{1 to} Rr ₄ are independently hydrogen atoms, alkyl groups having 1 to 4 carbon atoms, and 1 to 4 carbon atoms. Indicates an alkoxy group having an alkoxy group or a sulfo group and having 1 to 4 carbon atoms, j indicates 0 or 1, and Xr ₁ may have an amino group or a substituent. Indicates a good phenylamino group, 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, Ag ₁ represents a phenyl group having a substituent or a naphthyl group having a substituent, and Bg and Cg are independently represented by the following formulas (3) or (4), one of which is a formula. Represented by (3), Xg ₁ is an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, or a substituent. Indicates a benzoyl group which may have a benzoyl group, or a benzoylamino group which may have a substituent;

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 1 to 4 carbon atoms, and p ₁ is 0 to 2. Indicates an integer;

In the formula, Rg ₂ and Rg ₃ 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 and having a sulfo group. The polarizing element according to claim 1, wherein the 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 phenyl group having a substituent or a naphthyl group having a substituent, and Rg ₄ and Rg ₅ independently form a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group, or a sulfo group, respectively. It shows an alkoxy group having 1 to 4 carbon atoms, and Xg ₂ has an amino group which may have a substituent, a phenylamino group which may have a substituent, and a phenylazo which may have a substituent. group shown, which may have a substituent benzoyl group, or substituted indicates which may benzoylamino group, an integer of p _2, p ₃ each independently 0-2. The polarizing element according to claim ₃ , wherein p ₂ and p _{3 according} to the above formula (5) are 1 or 2, respectively. The polarizing element according to any one of claims 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 claims 1 to 5, wherein Xg ₁ described in the above formula (2) is a phenylamino group which may have a substituent. The polarizing element according to any one of claims 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 sulfo group, a carboxy group, a hydroxy 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 are independent hydrogen atoms. , An alkyl group having 1 to 4 carbon atoms, an alcoholic group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms having a sulfo group, and k represents an integer of 1 to 3 carbon atoms. In the transmittance of each wavelength obtained by stacking and measuring the two polarizing elements so that their absorption axis directions are parallel to each other, the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm are obtained. The difference between the above is 2.5% or less as an absolute value, and the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 600 nm to 640 nm is 3.0% or less as an absolute value. 7. The polarizing element according to any one of 7. According to JIS Z 8781-4: 2013, the absolute values of the a * value and b * value obtained when measuring the transmittance using natural light are
Both of the above polarizing elements are 1.0 or less (-1.0 ≤ a * -s ≤ 1.0, -1.0 ≤ b-s * ≤ 1.0).
In a state where the two polarizing elements are stacked and arranged so that their absorption axis directions are parallel to each other, both are 2.0 or less (-2.0 ≤ a * -p ≤ 2.0, -2.0". ≦ b * −p ≦ 2.0)
The polarizing element according to any one of claims 1 to 8 (a * -s indicates an a * value of a single substance, b * -s indicates a b * value of a single substance, and a * -p indicates a parallel value. Indicates the a * value at the position, and b * -p indicates b * at the parallel position). The single transmittance of the above-mentioned polarizing element after correction of luminosity factor is 35% to 45%.
The average transmittance of each wavelength of 520 nm to 590 nm, which is obtained by arranging the two polarizing elements on top of each other so that their absorption axis directions are parallel to each other, is 28% to 45%.
The polarizing element according to any one of claims 1 to 9. In the transmittance of each wavelength obtained in a state where the two polarizing elements are stacked and arranged so that their absorption axis directions are orthogonal to each other.
The difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is 1.0% or less as an absolute value, and the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 600 nm to 640 nm. Is 1.0% or less as an absolute value,
The polarizing element according to any one of claims 1 to 10. The invention according to any one of claims 1 to 10, wherein the orthogonal position transmittance at each wavelength of the wavelength band 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 97% or more. Polarizing element. The a * value and b * obtained when measuring the transmittance using natural light in accordance with JIS Z 8781-4: 2013 with the two polarizing elements stacked so that their absorption axis directions are orthogonal to each other. Any of claims 1 to 10, wherein the absolute value of each value is 2.0 or less (-2.0 ≤ a * -c ≤ 2.0, -2.0 ≤ b * -c ≤ 2.0). The polarizing element according to item 1 ((a * -c indicates an a * value at an orthogonal position, and b * -c indicates a b * at an orthogonal position). The polarizing element according to any one of claims 1 to 13, wherein the polarizing element includes a polyvinyl alcohol-based resin film as a base material. A polarizing plate including the polarizing element according to any one of claims 1 to 14 and a transparent protective layer provided on one side or both sides of the polarizing element. A display device including the polarizing element according to any one of claims 1 to 14 or the polarizing plate according to claim 15.