TW201823369A - Polarizing element, polarizing plate and liquid crystal display device using the same - Google Patents

Abstract

The present invention provides a polarizing element having high transmittance and high polarization degree, and a polarizing plate and a liquid crystal display device using the same. Also, the present invention provides a polarizing element comprising an azo compound represented by the formula (1a) or (1b) or a salt thereof, and an azo compound represented by the formula (2) or a salt thereof.

Description

   Polarizing element, and polarizing plate and liquid crystal display device using the same   

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

A polarizing element is generally manufactured by adsorbing iodine or a dichroic dye that is aligned with a dichroic dye on a polyvinyl alcohol-based resin film. Here, a polarizing plate obtained by bonding a protective film made of triethylsulfonate or the like with an adhesive layer interposed therebetween is used for a liquid crystal display device or the like. A polarizing plate using iodine as a dichroic dye is called an iodine-based polarizing plate. On the other hand, a polarizing plate using a dichroic dye such as a dichroic azo compound as a dichroic dye is called Dye-based polarizing plate. Among them, the dye-based polarizing plate has high heat resistance, high humidity and heat durability, and high stability, and has a high color selectivity by blending pigments. On the other hand, it has the same degree of polarization When comparing iodine-based polarizers, there is a problem that both the transmittance and the contrast are low. Therefore, in addition to maintaining high durability and various color selectivity, polarizing elements having higher transmittance and high polarization characteristics are desired.

In addition, even in the case of dye-based polarizing plates having various color selectivity, the polarizing elements so far have been such that the directions of the absorption axes of the two polarizing elements are parallel to each other (hereinafter, also referred to as "parallel positions"). In the overlapping arrangement, when white is displayed (hereinafter, also referred to as "when white is displayed" or "bright when displayed"), there is a problem that white appears slightly yellow. In order to improve the problem that this white color has a slight yellow color, even if it is a polarizing element made by suppressing the yellow color, the polarizers so far still have the problems of low polarization or low contrast, and extremely low durability.

So far, it is difficult to obtain a high degree of whiteness (commonly referred to as paper white) while obtaining high polarization and high contrast in a polarizing plate. This is because when trying to make the polarizer high contrast, in the parallel position, the transmittance on the short wavelength side will decrease, so that the absorption will increase, and the polarizer will show a slight yellow color. In other words, even though the parallel transmittance is constant at each wavelength in the visible light region, that is, even if the display paper is white, it is difficult to achieve high contrast. By realizing paper white, in addition to improving the contrast of the display, the color reproducibility when the display is bright when the liquid crystal display is displayed through the color filter is also highly improved. In order to be white, although the transmittance must be almost constant regardless of the wavelength in the parallel position, if there is no high contrast at the same time, it will be used in a display device and the display quality will decrease. Therefore, it is desired to have high contrast while being white in paper.

When an iodine-based polarizing plate is used as an example, an iodine-based polarizing plate using polyvinyl alcohol (hereinafter, also referred to as "PVA") as a base material and using iodine as a dichroic dye is generally 480 nm And 600nm centered absorption. It is said that the absorption at 480 nm is caused by a complex of polyiodine I ₃ ^- and PVA, and the absorption at 600 nm is caused by a complex of polyiodine I ₅ ^- and PVA. In terms of polarization (dichroism) at each wavelength, the degree of polarization (dichroism) based on the complex of polyiodine I ₅ ^- and PVA is higher than that based on the complex of polyiodine I ₃ ^- and PVA Object polarization (dichroism). In other words, when the transmittance of the vertical bit is set to be constant at each wavelength, the transmittance of the parallel bit is higher at 600 nm than at 480 nm. When white is displayed, white and yellow are generated. Conversely, when the transmittance of the parallel bit is set to a certain value, the transmittance of the vertical bit is lower than that of the 480 nm at 600 nm. When displaying black, the black is dyed blue, and the contrast becomes very low. . Furthermore, an iodine-based polarizing plate having a constant transmittance at a parallel position is further reduced in durability compared with a polarizing plate that emphasizes black when vertical. This system indicates that although the durability of iodine-based polarizers is generally low, the durability of polarizers with a fixed transmittance at a parallel position is lower. When white is displayed, white appears yellowish, and it generally cannot be said to be a good one because it generally has the impression of gradual deterioration. Also, when black is displayed, when the blue color is revealed, it is not obvious black, so it gives the impression of high-grade feeling, the contrast is lowered, and the durability is significantly lowered. In addition, in the iodine-based polarizing plate, the hue is difficult to control because the complex has no absorption complex at this wavelength, mainly around 550 nm, which has high visual sensitivity. In this way, since the degree of polarization (dichroism) of each wavelength is not constant, a wavelength dependence of the degree of polarization occurs. In addition, since only two dichroic pigments of 480 nm and 600 nm are absorbed by the complex of iodine and PVA, the hue of the iodine-based polarizing plate made of iodine and PVA cannot be adjusted.

A method for improving the hue of an iodine-based polarizing plate is described in Patent Document 1 or Patent Document 2. Patent Document 1 describes a polarizing plate in which a neutral coefficient is calculated and an absolute value is 0 to 3. Patent Document 2 describes that the transmittance between 410 nm and 750 nm is set within ± 30% of the average value. In addition to iodine, a direct dye, a reactive dye, or an acid dye is added and adjusted for coloring. Polarizing film.

In addition, to address the hue problem of the iodine-based polarizing plate, a coloring-type polarizing plate having no color in the parallel and vertical positions has also been developed (for example, Patent Document 3).

    [Prior technical literature]         [Patent Literature]    

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

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

[Patent Document 3] WO 2014/162635

However, in the polarizing plate of Patent Document 1, as is known from the examples, even if the neutral coefficient (Np) is low, the parallel hue obtained from JIS Z 8729 has a * value of -2 to -1, and b * The value is 2.5 to 4.0, so it can be seen that it appears yellowish green when displaying white. In addition, although the hue of the vertical bit is 0 to 1, but the b * value is -1.5 to -4.0, it becomes a polarizing plate that appears blue when displaying black.

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, not when the two polarizing films are overlapped. In the case of white display and black display, the color can be achromatic at the same time, and the contrast is very low. In addition, the average value of the unit transmittance of the polarizing film of Patent Document 2 was 31.95% in Example 1, and 31.41% in Example 2, which showed a low value. As described above, since the polarizing film of Patent Document 2 has a low transmittance, it does not have sufficient performance in fields requiring high transmittance and high contrast, particularly in the fields of liquid crystal display devices and organic electroluminescence. Moreover, since the polarizing film of Patent Document 2 mainly uses iodine as a dichroic pigment, after the durability test, especially after the wet heat durability test (for example, an environment of 85 ° C and a relative humidity of 85%), It changes a lot and the durability is poor.

On the other hand, although a dye-based polarizing plate is excellent in durability, it is the same as an iodine-based polarizing plate in that the wavelength dependence between the parallel position and the vertical position is different. Almost none of the dichroic azo compounds exhibiting the same hue in the parallel and vertical positions, even if they exist, the contrast (or polarization) is low. Depending on the type of dichroic azo compound, there are many white and yellow colors when displaying white, blue and black when displaying black, and the contrast is decreased. The wavelengths are vertical and parallel. Azo compounds with completely different dependencies. In addition, since human color sensitivity also varies depending on the light and darkness (transmittance) of light, even if the color correction of a dye-based polarizing plate is performed, it is necessary to have a color correction suitable for the light and dark of the light. The paper-white polarizing plate has almost a constant transmittance in each wavelength in the parallel position, which cannot be achieved without a wavelength-dependent state. Furthermore, in order to obtain a polarizing element with high transmittance and high contrast, in addition to satisfying a certain transmittance in parallel positions, it is necessary to increase the polarization degree (dichroic ratio) of each wavelength. Even in the case where one kind of azo compound is used in a polarizing element, it is necessary to consider its wavelength dependency, further adjust the azo compound, and accurately control the relationship between such transmittance and dichroic ratio.

On the other hand, even though the transmittance of the parallel bits can be accurately controlled and set to a certain level, high transmittance and high contrast cannot be achieved. In other words, if the transmittance is higher, it becomes more difficult to achieve high contrast, and a paper-white polarizer having high transmittance and high contrast cannot be achieved. It is very difficult to obtain a paper white polarizing plate with high transmittance and high contrast, which cannot be achieved by using only dichroic pigments of three primary colors. In particular, it is very difficult to achieve a certain transmittance and high dichroism in parallel positions at the same time. As long as white is mixed with a little color, high-quality white cannot be expressed. In addition, white in a bright state is particularly important because of its high brightness and high sensitivity. Therefore, as a polarizing element, a high-quality achromatic white paper-like color is required when displaying white, while showing high contrast, a single element having a transmittance of 35% or higher and a polarizing element having high polarization. Although Patent Document 3 describes a polarizing plate that is achromatic even when white is displayed and when black is displayed, it is desired to further improve performance.

Therefore, an object of the present invention is to provide a high-performance polarizing element having a high transmittance and a high contrast while displaying paper white when displaying white, and a polarizing plate and a liquid crystal display device using the polarizing element.

In order to solve the above-mentioned problems, the inventors have conducted a careful review and found that by blending a specific azo compound, a high-performance polarizing element can be prepared. The high-transmittance and white-colored display of High contrast. The inventor was the first in the world to discover that even with high transmittance, wavelength independence in the visible light region is achieved, and the development of a paper-like white (often referred to as paper white) that can achieve high grades Polarizing element with higher polarization.

That is, this invention relates to the following [invention 1] to [invention 12].

[Invention 1]

A polarizing element includes an azo compound represented by formula (1a) or (1b) or a salt thereof, and an azo compound represented by formula (2) or a salt thereof.

(In the formula, Ar ₁ represents a phenyl group or a naphthyl group having at least one substituent, and Rr ₁ to Rr ₄ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a sulfonic acid group. Lower alkoxy)

(In the formula, Av ₁ represents a phenyl group or a naphthyl group having at least one substituent selected from a sulfonic acid group and a carboxyl group, and Rv ₁ to Rv ₆ each independently represent a hydrogen atom, a lower alkyl group, or a lower alkoxy group. Or a lower alkoxy group having a sulfonic acid group, Xv ₁ means that it may have at least one selected from the group consisting of a lower alkyl group, a lower alkoxy group, a sulfonic group, an amine group, a lower alkylamino group, a hydroxyl group, a carboxyl group, And carboxyethylamino groups of substituents in the group of amino, phenylamino, phenylazo, naphthotriazolyl, or benzamylamino)

(In the formula, Ag ₁ represents a phenyl group or a naphthyl group having a substituent, Bg and Cg are each independently represented by formula (BC-N) or formula (BC-P), and at least one of them is a formula ( BC-N), Xg ₁ represents an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, or a benzamidineamino group which may have a substituent )

(In the formula, Rg ₁ represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfonic acid group, and k is an integer of 0 to 2)

(Rg ₂ and Rg ₃ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfonic acid group)

[Invention 2]

The polarizing element according to the invention 1 contains both at least one compound represented by formula (1a) or a salt thereof and at least one compound represented by formula (1b) or a salt thereof.

[Invention 3]

The polarizing element according to the invention 1 or 2, wherein Cg is represented by a formula (BC-N).

[Invention 4]

The polarizing element according to any one of Inventions 1 to 3, wherein the azo compound represented by the formula (2) is represented by the formula (2 ').

(In the formula, Ag ₁ and Xg ₁ are as defined in formula (2), Rg ₄ and Rg ₅ are as defined for Rg ₁ in formula (BC-N), and k ₁ and k ₂ are as in formula (BC -N) for the definition of k)

[Invention 5]

The polarizing element according to any one of Inventions 1 to 4, further comprising an azo compound represented by Formula (3) or a salt thereof.

(In the formula, Ay ₁ represents a sulfonic acid group, a carboxyl group, a hydroxyl group, a lower alkyl group, or a lower alkoxy group, and Ry ₁ to Ry ₄ each independently represent a hydrogen atom, a sulfonic acid group, a lower alkyl group, or Is a lower alkoxy group, and p represents an integer of 1 to 3)

[Invention 6]

The polarizing element according to any one of Inventions 1 to 5, wherein the polarizing element contains a polyvinyl alcohol-based resin film as a base material.

[Invention 7]

The polarizing element according to any one of Inventions 1 to 6, wherein the absolute values of a * value and b * value obtained when measuring the transmittance of natural light in accordance with JIS Z 8781-4: 2013 are in the aforementioned polarized light The element alone is 5.0 or less, and in a state where two pieces of the aforementioned polarizing elements are arranged so that their absorption axis directions are parallel to each other, they are both 2.0 or less.

[Invention 8]

The polarizing element according to any one of Inventions 1 to 7, wherein two pieces of the aforementioned polarizing elements are superimposed so that the absorption axis directions become parallel to each other and measured to obtain an average transmittance of 420 nm to 480 nm and 520 nm The absolute value of the difference between the average transmittance to 590 nm is 2.5% or less, and the absolute value of the difference between the average transmittance from 520 nm to 590 nm and the average transmittance from 600 nm to 640 nm is 2.0% or less.

[Invention 9]

The polarizing element according to any one of Inventions 1 to 8, wherein the single-element transmittance of the polarizing element is 35% to 65%, and the two polarizing elements are parallel to each other in the direction of their absorption axes. The average transmittance of 520nm to 590nm obtained in the state of overlapping arrangement is 25% to 45%.

[Invention 10]

A polarizing plate includes the polarizing element according to any one of Inventions 1 to 9, and a transparent protective layer provided on one or both sides of the polarizing element.

[Invention 11]

A liquid crystal display device includes the polarizing element according to any one of Inventions 1 to 9 or the polarizing plate according to Invention 10.

The present invention can provide a high-performance polarizing element, and a polarizing plate and a liquid crystal display device using the polarizing element, which display a paper white when displaying white, and have high transmittance and high contrast.

<Polarizing element>

The polarizing element of the present invention contains an azo compound represented by the formula (1a) or (1b) and an azo compound represented by the formula (2). Both of the azo compound represented by Formula (1a) and the azo compound represented by Formula (1b) may be arbitrarily contained. It may optionally further contain an azo compound represented by the formula (3).

It is preferable that the polarizing element contains such an azo compound or a salt thereof, and a substrate to which the above-mentioned azo compound or a salt is adsorbed.

The substrate is preferably a film or the like obtained by forming a hydrophilic polymer into a film capable of adsorbing a dichroic dye, especially an azo compound. The hydrophilic polymer is not particularly limited, but examples thereof include polyvinyl alcohol resins, amylose resins, starch resins, cellulose resins, polyacrylate resins, and derivatives thereof. . The hydrophilic polymer is preferably a polyvinyl alcohol-based resin and a derivative thereof from the viewpoints of dyeability, processability, and crosslinkability of a dichroic pigment. A polarizing element can be produced by adsorbing an azo compound or a salt thereof on the substrate and applying an alignment treatment such as stretching.

Next, the expression (1a) will be explained.

In formula (1a), Ar ₁ is a phenyl group or a naphthyl group having at least one substituent, and Rr ₁ to Rr ₄ are each independently a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a group having a sulfonic acid group. Lower alkoxy groups of acid groups. In addition, in the specification and patent application scope of the present case, "low" means that the carbon number is 1 to 4. For example, a lower alkyl group means an alkyl group having 1 to 4 carbon atoms.

In the formula (1a), when Ar ₁ is a phenyl group, it is preferably one having at least one substituent selected from the group consisting of a sulfonic acid group, a carboxyl group, and an alkoxy group. Those having at least one substituent are more preferred. When a phenyl group has two or more substituents, at least one of the substituents is a sulfonic acid group or a carboxyl group, and the other substituents are preferably selected from the group consisting of a sulfonic acid group, a carboxyl group, a lower alkyl group, and a lower alkoxy group. , A lower alkoxy group having a sulfonic acid group, a nitro group, an amine group, an ethylamino group, and a lower alkylamino group substituted with an amine group, more preferably selected from the group consisting of a sulfonic group, a methyl group, and an ethyl group , Methoxy, ethoxy, carboxyl, nitro, and amine groups, particularly preferably selected from the group consisting of sulfonic acid, methyl, methoxy, ethoxy, and carboxyl groups. As the lower alkoxy group having a sulfonic acid group, a linear alkoxy group is preferable, and a substitution position of the sulfonic acid group is preferably at an end of the alkoxy group. Such a lower alkoxy group having a sulfonic acid group is more preferably a 3-sulfonic acid propoxy group or a 4-sulfonic acid butoxy group, and particularly preferably a 3-sulfonic acid propoxy group.

When the phenyl group has a sulfonic acid group as a substituent, the number of sulfonic acid groups is preferably one or two. Although the position of the sulfonic acid group is not particularly limited, the number of sulfonic acid groups is one. In the case of the phenyl group at the 4th position, the sulfonic acid group is preferably the combination of the 2nd and the 4th position of the phenyl group, or the 3rd and the 3rd position of the phenyl group. A combination of five digits is preferred.

In the formula (1a), when Ar ₁ is a naphthyl group, it is preferable to have at least one sulfonic acid group as its substituent. When the naphthyl group has two or more substituents, at least one of the substituents is a sulfonic acid group, and the other substituents are preferably selected from the group consisting of a sulfonic acid group, a hydroxyl group, a carboxyl group, and a lower alkoxy group having a sulfonic acid group. Groups formed by the foundation. As the lower alkoxy group having a sulfonic acid group, a linear alkoxy group is preferable, and a substitution position of the sulfonic acid group is preferably at an end of the alkoxy group. Such a lower alkoxy group having a sulfonic acid group is more preferably a 3-sulfonic acid propoxy group or a 4-sulfonic acid butoxy group, and particularly preferably a 3-sulfonic acid propoxy group.

In the case where the number of sulfonic acid groups substituted in the naphthyl group is two, in the case where the substitution position of the azo group is set at the second position, the substitution position of the sulfonic acid group is set at the fourth position, the eighth position of the naphthyl group A combination of bits or a combination of 6th and 8th bits is preferable, and a combination of 6th and 8th bits is more preferable. When the number of sulfonic acid groups substituted in the naphthyl group is three, the substitution position of the sulfonic acid group is preferably a combination of the 3rd, 6th, and 8th positions.

In the formula (1a), Rr ₁ to Rr ₄ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfonic acid group. As the lower alkoxy group having a sulfonic acid group, a linear alkoxy group is preferable, and a substitution position of the sulfonic acid group is preferably at an end of the alkoxy group. Rr ₁ to Rr _{4 are} preferably each independently a hydrogen atom, methyl, ethyl, methoxy, ethoxy, 3-sulfopropoxy, or 4-sulfobutoxy Particularly preferred is a hydrogen atom, a methyl group, a methoxy group, or a 3-sulfonic acid propoxy group.

As the position of Rr ₁ to Rr ₄ on the phenyl group, it is preferably: only at the second position of the phenyl group, only at the fifth position, a combination of the second and sixth positions, and at the second position. The combination of the fifth position and the combination of the third and fifth positions are particularly preferable: only the second position, only the fifth position, and the combination of the second and fifth positions. Also, "only the first two" and "only in the first five" means about Rr ₁ and Rr _2, Rr ₁ and Rr _2, the two sides was a No. 2 or No. 5, and one of them is hydrogen A substituent other than an atom means a hydrogen atom. The same applies to Rr ₃ and Rr ₄ .

The azo compound represented by the formula (1a) is preferably an azo compound represented by the formula (1a '). By using the azo compound represented by the formula (1a '), the polarization performance of the polarizing element can be further improved.

(In formula (1a '), Ar ₁ and Rr ₁ to Rr ₄ are as defined in formula (1a))

Next, the expression (1b) will be explained.

In Formula (1b), Av ₁ represents a phenyl group or a naphthyl group having at least one substituent selected from a sulfonic acid group and a carboxyl group.

When Av ₁ is a phenyl group, it has at least one substituent selected from a sulfonic acid group or a carboxyl group. When the phenyl group has two or more substituents, at least one of the substituents is a sulfonic acid group or a carboxyl group, and the other substituents are preferably selected from a sulfonic acid group, a carboxyl group, a lower alkyl group, and a lower alkoxy group. A group consisting of a sulfonic group, a lower alkoxy group, a hydroxy group, a nitro group, a benzamidine group, an amine group, an ethylamino group, and a lower alkylamino group substituted with an amine group, more preferably selected from the group consisting of Groups of sulfonate, methyl, ethyl, methoxy, ethoxy, hydroxyl, carboxyl, nitro, amine, 3-sulfopropoxy, and 4-sulfobutoxy Particularly preferred is selected from the group consisting of sulfo, methyl, methoxy, carboxyl, and 3-sulfopropoxy. As the lower alkoxy group having a sulfonic acid group, a 3-sulfonic acid propoxy group or a 4-sulfonic acid butoxy group as described above is preferred, and a straight-chain alkoxy group is more preferable. The substitution position is preferably the terminal of the alkoxy group.

When the phenyl group has a sulfonic acid group as a substituent, the number of the sulfonic acid group is preferably one or two, and the substitution position of the sulfonic acid group is not particularly limited, but the sulfonic acid group is 1 In the case of the phenyl group, the fourth position is preferred. In the case of the sulfonic acid group, the combination is the combination of the 2nd and 4th positions of the phenyl group, or the 3rd and 5th positions. The combination is better. When the phenyl group has a carboxyl group as a substituent, the number of carboxyl groups is preferably one or two. Although the position of the carboxyl group is not particularly limited, when the carboxyl group is one, benzene is used. The 4th position of the group is preferred. When the carboxyl group is 2, the combination of the 2nd and 4th positions of the phenyl group or the combination of the 3rd and 5th positions is preferred.

When Av ₁ is a naphthyl group, it is preferable to have at least one sulfonic acid group as its substituent. When the naphthyl group has two or more substituents, at least one of the substituents is a sulfonic acid group, and the other substituents are selected from a sulfonic acid group, a hydroxyl group, a carboxyl group, and a lower alkoxy group having a sulfonic acid group. Groups are better. As the lower alkoxy group having a sulfonic acid group, a linear alkoxy group is preferable, and a substitution position of the sulfonic acid group is preferably at an end of the alkoxy group. Such a lower alkoxy group having a sulfonic acid group is more preferably a 3-sulfonic acid propoxy group or a 4-sulfonic acid butoxy group, and particularly preferably a 3-sulfonic acid propoxy group.

In the case where the number of sulfonic acid groups substituted in the naphthyl group is two, in the case where the substitution position of the azo group is set at the second position, the substitution position of the sulfonic acid group is set at the fourth position, the eighth position of the naphthyl group The combination of the bits is preferably the combination of the 6th and the 8th bits, and the combination of the 6th and the 8th bits is more preferable. When the number of sulfonic acid groups substituted in the naphthyl group is three, the substitution position of the sulfonic acid group is preferably a combination of the 3rd, 6th, and 8th positions. In the case where the number of sulfonic acid groups substituted in the naphthyl group is one, the substitution positions of the sulfonic acid group can be listed at the substitution positions of the naphthyl group such as the 3rd, 4th, 6th, and 8th positions as a comparison. The preferred replacement position is not limited thereto.

Rv ₁ to Rv ₆ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfonic acid group. As the lower alkoxy group having a sulfonic acid group, a linear alkoxy group is preferable, or a substitution position of the sulfonic acid group is preferably at an end of the alkoxy group. Rv ₁ to Rv ₆ are each independently, preferably a hydrogen atom, methyl, ethyl, methoxy, ethoxy, 3-sulfopropoxy, or 4-sulfobutoxy, Particularly preferred is a hydrogen atom, a methyl group, a methoxy group, a carboxyl group, or a 3-sulfonic acid propoxy group. When Rv ₆ is a hydrogen atom or a methyl group, the polarization performance of a polarizing element or a polarizing plate is further improved, which is preferable. Especially when Rv ₅ and Rv ₆ are a hydrogen atom and a methyl group, the polarization performance of a polarizing element or a polarizing plate can be greatly improved, so it is preferable.

Xv ₁ represents that it may have at least one substituent selected from the group consisting of a lower alkyl group, a lower alkoxy group, a sulfonic acid group, an amine group, a lower alkylamino group, a hydroxyl group, a carboxyl group, and a carboxyethylamino group. Amine, phenylamino, phenylazo, naphthotriazolyl, or benzamylamino.

In the case where Xv ₁ is an amine group which may have a substituent, the amine group is unsubstituted or preferably has one or two selected from lower alkyl, lower alkoxy, sulfonic acid, amine, and lower The substituents in the group of alkylamine groups are more preferably one or two substituents selected from the group of methyl, methoxy, sulfonic acid, amine, and lower alkylamino groups. base. Here, the amine group which may have a substituent is excluding the amine group which has a ring structure, such as a phenylamino group.

In the case where Xv ₁ is a phenylamino group which may have a substituent, the phenylamine group is unsubstituted or preferably has one or two selected from a lower alkyl group, a lower alkoxy group, a sulfonic acid group, and an amine The substituents in the group formed by a group and a lower alkylamino group preferably have one or two substituents selected from the group formed by a methyl group, a methoxy group, a sulfonic group, and an amine group.

In the case where Xv ₁ is a phenylazo group which may have a substituent, the phenylazo group is unsubstituted or preferably has 1 to 3 selected from a hydroxyl group, a lower alkyl group, a lower alkoxy group, and an amine group The substituents in the group consisting of carboxyl and carboxyethylamino are more preferably one to three substituents selected from the group consisting of methyl, methoxy, amine, and hydroxyl.

When Xv ₁ is a naphthotriazolyl group which may have a substituent, the naphthotriazolyl group is unsubstituted or preferably has one or two groups selected from the group consisting of a sulfonic acid group, an amine group, and a carboxyl group The substituent of the group preferably has one or two sulfonic acid groups as a substituent.

In the case where Xv ₁ is a benzamidineamino group which may have a substituent, the benzamidineamino group is unsubstituted or preferably has one selected from the group consisting of a hydroxyl group, an amino group, and a carboxyethylamino group. The substituent of the group preferably has one or two hydroxyl groups or amine groups as the substituent.

Xv _{1 is} preferably a benzamidineamino 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. Although the position of the substituent is not particularly limited, in the case where the phenylamino group has a substituent, it is preferable that one of the substituents is at the p position with respect to the amine group, and has a substituent in the benzamidineamino group. In the case, one of the substituents is preferably at the p position with respect to the carbonyl group.

The azo compound represented by the formula (1b) is particularly preferably an azo compound represented by the formula (1b '). By using the azo compound represented by the formula (1b '), the polarization performance of the polarizing element can be further improved.

In formula (1b '), Av ₁ , Rv ₂ , Rv ₄ to Rv ₆ , and Xv ₁ are as defined in the formula (1b).

Specific examples of the azo compound represented by the formula (1a) are listed below as a free acid.

Specific examples of the azo compound represented by the formula (1b) are listed below in the form of a free acid.

The azo compound represented by the formula (1a) or (1b) may be used alone or in combination of two or more. In one aspect, both the azo compound represented by the formula (1a) and the azo compound represented by the formula (1b) may be used.

The azo compound or a salt thereof represented by the formula (1a) can be synthesized by, for example, a method described in Japanese Patent Application Laid-Open No. 2009-155364 or the like and a method similar thereto, but is not limited thereto. For example, an azo compound represented by formula (1a) can be produced by reacting a base compound represented by formula (v) described later with a urethanizing agent such as phenyl chlorocarbonate at 20 to 95 ° C. As another method for synthesizing by urethanization, a method of urethanizing an amine compound using a phosgene compound or the like is known. By this synthesis method, an azo compound represented by the formula (1a) having a ureido skeleton can be obtained.

A specific synthesis method of the azo compound represented by the formula (1a) will be described below. First, the amines having a substituent as shown in formula (i) are diazotized by a method similar to the method described by Hosoda Toyoda, "Dye Chemistry", Kyodo, 1957, p.135-234. And, secondly, coupling with an aniline represented by formula (ii) to obtain a monoazoamino compound represented by formula (iii).

Ar-NH ₂ ‧‧‧ (i) (where Ar is the same as Ar ₁ in formula (1a))

(In the formula, R ₁ and R ₂ are respectively the same as Rr ₁ and Rr ₂ in formula (1a).)

(In the formula, Ar is the same as Ar _{1 in} formula (1a), and R ₁ and R ₂ are the same as Rr ₁ and Rr ₂ in formula (1a), respectively)

Next, the monoazoamino compound represented by the formula (iii) is diazotized and further coupled with the aniline represented by the formula (iv) twice to obtain the disazo compound represented by the formula (v). Amine compounds.

(In the formula, R ₃ and R ₄ are respectively the same as Rr ₃ and Rr ₄ in formula (1a).)

(In the formula, Ar represents the same as Ar _{1 of} formula (1a), R ₁ and R ₂ represent the same as Rr ₁ and Rr ₂ in formula (1a), and R ₃ and R ₄ represent the same as (Where Rr ₃ and Rr _{4 are the} same in formula (1a))

The diazotization step in the above reaction route is carried out according to the so-called cis-method of mixing nitrite such as sodium nitrite in an aqueous solution or suspension of a mineral acid such as hydrochloric acid or sulfuric acid with a diazo component, or in accordance with After adding a nitrite to a neutral or weakly alkaline aqueous solution of a diazo component, the so-called reverse method is performed by mixing the nitrite with a mineral acid. The temperature of the diazotization is suitably -10 to 40 ° C. The coupling step with anilines is performed by mixing an acidic aqueous solution such as hydrochloric acid and acetic acid with each of the above diazonium solutions, and performing the acidic condition at a temperature of -10 to 40 ° C and a pH of 2 to 7.

The monoazoamino compound or the diazoamino compound obtained through the coupling step can be directly or through acid precipitation, salting out, and filtered and taken out, or further maintain the solution or suspension A step of. When the diazonium salt is hardly soluble and is a suspension, the suspension can also be filtered, and the diazonium salt filtered in the form of a filter cake is further used in the coupling step.

The bisazoamine-based compound obtained through the above steps is then subjected to a ureido reaction with phenyl chlorocarbonate, thereby synthesizing an azo compound represented by the formula (1a). The ureido reaction is performed, for example, by a production method described in Japanese Patent Application Laid-Open No. 2009-155364 under neutral to alkaline conditions at a temperature of 10 to 90 ° C and a pH of 7 to 11. After the urethanization reaction was completed, the obtained azo compound was precipitated by salting out, followed by filtering. When purification is required, the azo compound obtained may be precipitated from water by repeated salting out or using an organic solvent. Examples of the organic solvent used in the purification include water-soluble organic solvents such as alcohols such as methanol and ethanol, and ketones such as acetone. In this way, an azo compound represented by the formula (1a) can be synthesized.

The azo compound represented by the formula (1b) can be produced by methods described in, for example, WO 2012/108169 and WO 2012/108173, but it is not limited to these.

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

In the 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, it is preferable to have at least one substituent selected from a sulfonic acid group and a carboxyl group. When the phenyl group has two or more substituents, at least one of the substituents is a sulfonic acid group or a carboxyl group, and the other substituents are a sulfonic acid group, a carboxyl group, a lower alkyl group, a lower alkoxy group, An acid-based lower alkoxy group, a nitro group, an amine group, an ethylamino group, or a lower alkylamino group is preferably substituted with an amine group. Other substituents are more preferably sulfo, methyl, ethyl, methoxy, ethoxy, carboxyl, nitro, or amine. Particularly preferred are sulfo, methyl, methoxy, Ethoxy or carboxyl. As the lower alkoxy group having a sulfonic acid group, a linear alkoxy group is preferred, and the substitution position of the sulfonic acid group is preferably at the end of the alkoxy group, more preferably a 3-sulfonic acid propoxy group and 4-sulfobutoxy, particularly preferred is 3-sulfopropoxy. The number of substituents in the phenyl group is preferably one or two. Although the position of substitution is not particularly limited, when the position of the azo group is set to the first position, it is set to only the fourth position. A combination of 2nd and 4th, and a combination of 3rd and 5th are preferred.

When Ag ₁ is a naphthyl group having a substituent, it is preferable to have at least one sulfonic acid group as a substituent. When the naphthyl group has two or more substituents, at least one of the substituents is a sulfonic acid group, and the other substituents are sulfonic acid group, hydroxyl group, carboxyl group, or a lower alkoxy group having a sulfonic acid group as good. The naphthyl group is particularly preferably one having two or more sulfonic acid groups as a substituent. As the lower alkoxy group having a sulfonic acid group, a linear alkoxy group is preferred, and the substitution position of the sulfonic acid group is preferably at the end of the alkoxy group, more preferably a 3-sulfonic acid propoxy group and 4-sulfobutoxy, but particularly preferred is 3-sulfopropoxy.

In the case where the number of sulfonic acid groups in the naphthyl group is 2, when the position of the sulfonic acid group is set to the second position, a combination of the fourth and eighth positions is preferred. , And the combination of the 6th and 8th positions is preferred, and the combination of the 6th and 8th positions is more preferred. When the number of sulfonic acid groups in the naphthyl group is 3, the substitution position of the sulfonic acid group is preferably a combination of the 3rd, 6th, and 8th positions.

Bg and Cg are each independently represented by formula (BC-N) or formula (BC-P), and at least one of Bg and Cg is represented by formula (BC-N). Cg is preferably represented by the formula (BC-N). When Cg is expressed by the formula (BC-N), it is possible to obtain a polarizing element with a high contrast while achieving higher-quality white paper.

In the formula (BC-N), Rg ₁ each independently represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfonic acid group. Rg _{1 is} 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. Particularly preferred Rg ₁ is a hydrogen atom or a methoxy group. As the lower alkoxy group having a sulfonic acid group, a linear alkoxy group is preferable, and the substitution position of the sulfonic acid group is preferably at the alkoxy terminal, more preferably 3-sulfonic acid propoxy group and 4 -Sulfobutoxy, particularly preferably 3-sulfopropoxy.

The substitution position of Rg ₁ is preferably the second or third position with respect to the azo group substituted in Ag _{1. When} the azo group on the Ag ₁ side is set to the first position, It is better to be in the third position. In the case of having a sulfonic acid group, the substitution position of the sulfonic acid group is preferably the 6th or 7th position, and more preferably the 6th position. In the formula (BC-N), k is an integer representing 0 to 2.

In the formula (BC-P), Rg ₂ and Rg ₃ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfonic acid group, preferably a hydrogen atom or a methyl group. Group, methoxy, 3-sulfopropoxy, or 4-sulfopropoxy.

Xg ₁ represents an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, or a benzamidineamino 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. In the scope of the patent application and the specification of the present application, "may have a substituent" means that it also includes a case without a substituent. For example, "the phenyl group which may have a substituent" includes an unsubstituted simple phenyl group and a phenyl group having a substituent. An amine group which may have a substituent, preferably one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfonic group, an amine group, and a lower alkylamine group The amine group of the group is more preferably an amine group having one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, and a sulfonic acid group. Among the amine groups which may have a substituent, amine groups having a ring structure such as a phenylamino group are excluded. A phenylamino group which may have a substituent, preferably having one or two members selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfonic group, an amine group, and a lower alkylamino group The phenylamino group of the substituent in the group is more preferably a benzene having one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfonic group, and an amine group. Amino group. Although the substitution position is not particularly limited, it is particularly preferred that one of the substituents is at the p position relative to the amine group of the phenylamino group.

The phenylazo group which may have a substituent is preferably one to three selected from a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an amine group, a hydroxyl group, And a phenylazo group as a substituent in the group of carboxyethylamino groups.

The benzamidineamino group which may have a substituent is preferably a benzamidineamino group having a substituent selected from the group consisting of a hydrogen atom, a hydroxyl group, an amine group, and a carboxyethylamino group.

Since the performance is particularly improved, the azo compound represented by formula (2) or a salt thereof is preferably an azo compound represented by formula (2 ') or a salt thereof.

In the formula (2 '), Ag ₁ is as defined in the formula ₁ Ag (2) is. Rg ₄ and Rg ₅ are each independently defined as Rg ₁ in formula (BC-N). Xg Xg is defined as _a system of ₁ (2). k ₁ and k ₂ are integers independently representing 0 to 2.

In the polarizing element of the present invention, the content of the azo compound represented by the formula (2) or a salt thereof is from 0.01 to 100 parts by mass based on the content of the azo compound represented by the formula (1a) or (1b). It is preferably 5,000 parts by mass, and more preferably 0.1 to 3,000 parts by mass.

The azo compound represented by formula (2) or a salt thereof can be exemplified by Japanese Patent Application Laid-Open No. 01-161202, Japanese Patent Application Laid-Open No. 01-172907, Japanese Patent Application Laid-Open No. 01-248105, and Japanese Patent Application Laid-Open No. 01 -265205, and Japanese Patent Application Laid-Open No. 01-172907, but are not limited to these.

Specific examples of the azo compound represented by formula (2) include the following azo compounds: CI Direct Blue 34, CI Direct Blue 69, CI Direct Blue 70, CI Direct Blue 71, CI Direct Blue 72, CI Direct Blue 75, CI Direct Blue 78, CI Direct Blue 81, CI Direct Blue 82, CI Direct Blue 83, CI Direct Blue 186, CI Direct Blue 258, Benzo Fast Chrome Blue FG (CI34225), Benzo Fast Blue BN (CI34120), CI Direct Green 51, etc.

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

The polarizing element contains a combination of an azo compound represented by the formula (1a) or (1b) or a salt thereof and an azo compound represented by the formula (2) or a salt thereof, and even if it has a polarized light more than conventional The board has higher transmittance and high polarization, and can still achieve high-quality paper-like white (usually called paper white) when displaying white.

In order to improve the polarizing performance of the polarizing element of the present invention, it is preferable to contain an azo compound represented by formula (1a) or (1b) or a salt thereof and an azo compound represented by formula (2) or a salt thereof. In addition, it further contains at least one azo compound represented by formula (3) or a salt thereof.

In formula (3), Ay ₁ represents a sulfonic acid group, a carboxyl group, a hydroxyl group, a lower alkyl group, or a lower alkoxy group, preferably a sulfonic acid group, a carboxyl group, or a lower alkoxy group, and more preferably a sulfonic acid Group, carboxyl group, methoxy group or ethoxy group, still more preferably a sulfonic group or a carboxyl group.

Ry ₁ to Ry ₄ each independently represent a hydrogen atom, a sulfonic acid group, a lower alkyl group, or a lower alkoxy group or a lower alkoxy group having a sulfonic acid group, preferably a hydrogen atom, a sulfonic acid group, A methyl group, an ethyl group, a methoxy group, or an ethoxy group, more preferably a hydrogen atom, a sulfonic group, a methyl group, or a methoxy group.

p is an integer from 1 to 3.

The azo compound represented by the formula (3) has an influence on the transmittance at 400 to 500 nm. In the polarizing element, the transmittance and polarization (dichroism) of the short wavelength side of 400 to 500 nm in particular have an effect on transmitting a blueish color when displaying black or a whiteish yellow feeling when displaying white. . The azo compound represented by the formula (3) does not decrease the transmittance on the short wavelength side of the parallel position of the polarizing element, and also improves the polarization characteristics (dichroism) in the range of 400 to 500 nm, which can be further reduced. The light yellow feeling when displaying white and the blue seeping out when displaying black. By further containing the azo compound represented by the formula (3), the polarizing element of the present invention can obtain a polarizing element that exhibits a more neutral hue and a higher degree of polarization.

The azo compound or a salt thereof represented by the formula (3) can be synthesized by a method described in, for example, WO 2007/138980, or a commercially available product can be used.

Examples of the azo compound represented by the formula (3) include, for example, CI Direct Yellow 4, CI Direct Yellow 12, CI Direct Yellow 72, CI Direct Orange 39, and diphenyl compounds described in WO 2007/138980. Azo compounds and the like having an ethylene structure are not limited thereto.

Specific examples of the azo compound represented by the formula (3) are listed below.

The azo compound represented by the formula (3) may be used alone or in combination of two or more.

In order to improve the polarizing performance of the polarizing element of the present invention, it is preferable to further contain an azo compound represented by the formula (2) or a salt thereof and an azo compound represented by the formula (3) or a salt thereof. Both the azo compound represented by (1a) or its salt and the azo compound represented by formula (1b) or its salt are both.

The polarizing element includes an azo compound represented by the formula (1a), an azo compound represented by the formula (1b), an azo compound represented by the formula (2), and an azo compound represented by the formula (3). Combination, even with high transmittance and high polarization, it can still achieve a higher grade of paper white when displaying white, and achieve clear black with a higher sense when displaying black.

The azo compound represented by formula (1a), the azo compound represented by formula (1b), the azo compound represented by formula (2), and the azo compound represented by formula (3) may be in a free form, It may be in the form of a salt. The salt may 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 of the present invention contains an azo compound represented by formula (1a) or (1b) and an azo compound represented by formula (2), and optionally contains an azo compound represented by formula (1a) and Both the azo compound represented by the formula (1b), and optionally further contain an azo compound represented by the formula (3). The polarizing element of the present invention can have properties such as desired chromaticity a * and b * values described later, a single transmittance, and an average transmittance in a specific wavelength band.

The blending ratio of the azo compound in the polarizing element is further adjusted as appropriate so that the transmittance and chromaticity become the preferred ranges described later in the content of each azo compound described above. The performance of polarizing elements is not only due to the mixing ratio of each azo compound in the polarizing element, but also due to the swelling degree or elongation of the substrate that adsorbs the azo compounds, the dyeing time, the dyeing temperature, the pH during dyeing, and the effects of salt Various factors vary. Therefore, the compounding ratio of each azo compound can be determined according to the degree of swelling of the substrate, temperature, time, pH, type of salt, salt concentration, and extension ratio in the substrate. The determination of such a blending ratio can be made by a person having ordinary knowledge in the art based on the following description without trial and error.

(Penetration)

The transmittance is the transmittance corrected for visual sensitivity obtained in accordance with JIS Z 8722: 2009. The transmittance can be measured by measuring the spectral transmittance of the test sample (for example, a polarizing element or a polarizing plate) at a wavelength of 400 to 700 nm every 5 nm or 10 nm. (C light source) correction is obtained by visual sensitivity.

(I) Difference in average transmittance between two wavelength bands

The polarizing element of the present invention preferably has a difference in average transmittance between specific wavelength bands below a predetermined value. The average transmittance is the average of the transmittance in a specific wavelength band.

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

The polarizing element of the present invention relates to a transmittance (hereinafter, also referred to as a polarizing element) measured by measuring a state where two polarizing elements are arranged so that the absorption axis directions are parallel to each other (when the display is bright or when the display is white). ("Parallel penetration"), the absolute value of the difference between the average transmittance of 420nm to 480nm and the average transmittance of 520nm to 590nm is preferably 2.5% or less, more preferably 1.8% or less, more preferably Below 1.5%, particularly preferred is below 1.0%. Regarding parallel bit transmittance, the absolute value of the difference between the average transmittance of 520nm to 590nm and the average transmittance of 600nm to 640nm is preferably 2.0% or less, more preferably 1.5% or less, and more preferably 1.0 %the following. Such a polarizing element can display high-quality paper-like white in parallel position.

In addition, the transmittance (hereinafter, also referred to as "vertical position") obtained by measuring the state where two polarizing elements are arranged so that the absorption axis direction is vertical (when black is displayed or when the display is dark) is measured. Transmittance "), the absolute value of the difference between the average transmittance of 420nm to 480nm and the average transmittance of 520nm to 590nm is less than 10%, and the average transmittance of 520nm to 590nm and the average transmittance of 600nm to 640nm The absolute value of the difference in transmittance is preferably 2.0% or less, and more preferably 1% or less. Such a polarizing element can display achromatic black in the vertical position. Regarding the vertical transmittance, the absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is preferably 2% or less, and more preferably 1% or less. Regarding the vertical bit transmittance, the absolute value of the difference between the average transmittance of 520nm to 590nm and the average transmittance of 600nm to 640nm is preferably 0.5% or less, more preferably 0.2% or less, and still more preferably 0.1%. the following.

In addition, the respective average transmittances of the individual transmittance, the parallel transmittance, and the vertical transmittance of each of the wavelength bands of 380 nm to 420 nm, 480 nm to 520 nm, and 640 nm to 780 nm are in The average transmittance in the above-mentioned wavelength bands of 420 nm to 480 nm, 520 nm to 590 nm, and 600 nm to 640 nm is adjusted as described above. Although it is difficult to be greatly affected by the pigment, it is preferably adjusted to some extent. The difference between the average transmittance of 380nm to 420nm and the average transmittance of 420nm to 480nm in the wavelength band is preferably 15% or less, preferably: the average transmittance of 480nm to 520nm and the average transmission of 420nm to 480nm The difference between the average transmittance is less than 15%, and the difference between the average transmittance of 480nm to 520nm and the average transmittance of 520nm to 590nm is less than 15%. The difference is less than 20%.

(II) monomer penetration

The polarizing element of the present invention preferably has a single transmittance of 35% to 65%. The single transmittance is a transmittance corrected for visual sensitivity in accordance with JIS Z 8722: 2009 for one measurement sample (for example, a polarizing element or a polarizing plate). As the performance of a polarizing plate, although a higher transmittance is required, if the unit transmittance is 35% to 60%, even if it is used in a display device, it can exhibit brightness without abnormality. As the transmittance is higher, the polarization degree tends to decrease, so from the viewpoint of balance with the polarization degree, the monomer transmission rate is preferably 37% to 50%, and more preferably 38% to 45%. %. Although the polarization degree may decrease when the transmission rate of the monomer exceeds 65%, the transmission rate of the unit may also exceed 65% when the bright transmission rate of a polarizing element or specific polarization performance or contrast is required.

(III) Average transmittance in a specific wavelength band

The polarizing element preferably has an average transmittance of 28% to 50% in a wavelength band of 520nm to 590nm measured in parallel. When such a polarizing element is installed in a display device, it can be used as a bright and clear display device with high brightness. The transmittance in the wavelength band from 520nm to 590nm is one of the main wavelength bands according to the color matching function used in the calculation when the color is displayed in JIS Z 8781-4: 2013. In particular, the wavelength bands of 520nm to 590nm are wavelength bands with the highest visual sensitivity according to the color matching function, and the transmittance in this range is close to the transmittance that can be confirmed visually. Therefore, it is very important to adjust the transmittance in the wavelength band of 520nm to 590nm. The average transmittance in the wavelength band of 520nm to 590nm measured in the parallel position is preferably 29% to 45%, and more preferably 30% to 40%. The polarization degree of the polarizing element at this time is preferably 80% to 100%, more preferably 95% to 100%, and even more preferably 99% to 100%. Although the polarization is better, the relationship between polarization and transmittance can be adjusted to the appropriate transmittance and polarization due to the importance of brightness or polarization (or contrast). .

(Chroma a * value and b * value)

The chromaticity a * value and b * value are values obtained when measuring the transmittance of natural light in accordance with JIS Z 8781-4: 2013. The display method of object colors formulated by JIS Z 8781-4: 2013 is equivalent to the display method of object colors formulated by the International Commission on Illumination (abbreviated as CIE). The measurement of chromaticity a * value and b * value is performed by irradiating a measurement sample (for example, a polarizing element or a polarizing plate) with natural light. In the following, the chromaticity a * values and b * values obtained for one measurement sample are expressed as a * -s and b * -s. For two measurement samples, the absorption axis directions are parallel to each other. The chromaticity a * value and b * value obtained in the state of the mode arrangement (when white is displayed) are expressed as a * -p and b * -p. For two measurement samples, the absorption axis directions are perpendicular to each other. The chromaticity a * value and b * value obtained in the state of the mode arrangement (when black is displayed) are expressed as a * -c and b * -c.

In the polarizing element of the present invention, each of the absolute values of a * -s and b * -s is preferably 5.0 or less, and more preferably 1.0 or less. Each of the absolute values of a * -p and b * -p is preferably 2.0 or less. Such a polarizing element has a neutral color in the monomer and can display high-quality white when displaying white. The absolute values of a * -p and b * -p of the polarizing element are preferably 1.5 or less, and more preferably 1.0 or less. The polarizing element preferably has an absolute value of a * -c and b * -c of 20.0 or less, more preferably 10.0 or less, more preferably 3.0 or less, and particularly preferably 1.0 or less. Such a polarizing element can display achromatic black when displaying black. In the absolute values of the chromaticity a * value and b * value, even if there is only a difference of 0.5, humans can feel a color difference, and they can feel a large color difference depending on the person. Therefore, it is very important to control these values in a polarizing element. In particular, when the absolute values of a * -p, b * -p, a * -c, and b * -c are 1.0 or less, it is almost impossible to confirm the presence of white when displaying white and black when displaying black. For other colors, a good polarizer can be obtained. In the parallel position, achromaticity, that is, high-grade white like paper, can be achieved, and in the vertical position, achromatic, high-quality, clear black can be realized.

The polarizing element of the present invention has high contrast and high transmittance, and has achromatic properties and high polarization of the monomer. In addition, the polarizing element of the present invention can express high-quality white (paper white) when displaying white, and the polarizing element of the present invention can exhibit achromatic color when displaying black because of its high contrast. Black, especially clear black with high-level sense. So far, such a polarizing element having both high transmittance and achromaticity has not existed. The polarizing element of the present invention further has high durability, particularly durability against high temperature and high humidity.

In addition, the polarizing element of the present invention has the advantage of less heat generation even when irradiated with light such as sunlight, since the absorption of light having a wavelength of 700 nm or more is less than that of a generally used iodine-based polarizing plate or Patent Document 3. For example, when a liquid crystal display is used outdoors or the like, sunlight irradiates the liquid crystal display, and as a result, the polarizing element is also irradiated. Sunlight also has light with a wavelength of more than 700nm, and contains near-infrared rays with a heating effect. For example, a polarizing element using an azo compound as described in Example 3 of Japanese Patent Publication No. 02-061988 has a slight heat generation because it absorbs near-infrared light near a wavelength of 700 nm. Since the absorption of near-infrared rays is extremely small, even if exposed to sunlight outdoors, the heat is still small. The polarizing element of the present invention is excellent in terms of less heat generation and less deterioration.

In the following, a case where a substrate made of a polyvinyl alcohol resin is made to adsorb an azo compound is taken as an example, and a specific method for producing a polarizing element will be described. The method of manufacturing the polarizing element of the present invention is not limited to the following manufacturing method.

(Preparation of raw film)

The raw material film can be produced by forming a polyvinyl alcohol-based resin into a film. The polyvinyl alcohol-based resin is not particularly limited, and a commercially available product may be used or may be synthesized by a known method. The polyvinyl alcohol-based resin can be obtained, for example, by saponifying a polyvinyl acetate-based resin. As the polyvinyl acetate-based resin, in addition to polyvinyl acetate homopolymer of vinyl acetate, copolymers of vinyl acetate and other monomers copolymerizable with vinyl acetate can also be exemplified. Examples of other monomers copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The saponification degree of the polyvinyl alcohol resin is usually about 85 to 100 mol%, more preferably 95 mol% or more. The polyvinyl alcohol-based resin may be further modified, and for example, polyvinyl acetal or polyvinyl acetal modified with aldehydes may be used. The degree of polymerization of the polyvinyl alcohol resin means the average degree of polymerization of the viscosity, which can be obtained by a well-known method in the technical field. Usually, it is preferably about 1,000 to 10,000, and more preferably the degree of polymerization is 1,500. To around 6,000.

The method of forming a polyvinyl alcohol-type resin into a film is not specifically limited, A film can be formed by a well-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, and more preferably 8 to 15% by mass in the total amount of the film. Although the film thickness of the raw material film is not particularly limited, it is, for example, about 5 μm to 150 μm, and preferably about 10 μm to 100 μm.

(Swelling step)

The raw material film obtained as described above is subjected to a swelling treatment. The swelling treatment is preferably performed by immersing the raw material film in a solution at 20 to 50 ° C for 30 seconds to 10 minutes. The solution is preferably water. The stretch magnification is preferably adjusted to 1.00 to 1.50 times, and more preferably adjusted to 1.10 to 1.35 times. In a case where the time for manufacturing the polarizing element is shortened, since the raw material film is swelled during the dyeing process described later, the swelling process may be omitted.

(Dyeing step)

In the dyeing step, an azo compound is adsorbed and impregnated on a resin film obtained by subjecting a raw material film to a swelling treatment. In the case where the swelling step is omitted, the swelling treatment of the raw film may be performed simultaneously in the dyeing step. The process of adsorbing and impregnating the azo compound is a dyeing step because it is a step of coloring the resin film.

As the azo compound, an azo compound represented by the formula (1a) or (1b) or a salt thereof and a mixture of the azo compound represented by the formula (2) or a salt thereof may be used, and may be further used arbitrarily. The formula (3) is an azo compound represented by the formula (4) or a salt thereof. It is also possible to use examples such as "application of functional pigments" (CMC (stock) publication, 1st print release, supervised by Iri Masaru, page 98 to 100) to the extent that the performance of the polarizing element of this case is not impaired. Azo compounds of dichroic dyes to adjust color. These azo compounds may be used in the form of a free acid, as well as a salt of the compound. Such a salt is, 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, and is preferably a sodium salt.

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

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

In addition to the azo compound, the dyeing solution may further contain a dyeing auxiliary agent as needed. Examples of the dyeing auxiliary include sodium carbonate, sodium bicarbonate, sodium chloride, sodium sulfate, anhydrous sodium sulfate, and sodium tripolyphosphate. Although the content of the dyeing assistant can be arbitrarily adjusted according to the time and temperature caused by the dyeability of the dye, the content of each is preferably 0.01 to 5 mass% in the dyeing solution, and 0.1 to 2 mass%. For the better.

(Washing step 1)

After the dyeing step, a washing step (hereinafter, also referred to as "washing step 1") may be performed before proceeding to the next step. The dyeing step 1 is a step of washing the dyeing solution attached to the surface of the resin film in the dyeing step. By performing the washing step 1, it is possible to suppress the migration of the dye into the subsequent treatment solution. In the washing step 1, water is generally used as a washing solution. Although the washing method is preferably immersed in a washing solution, it may be washed by applying a washing solution to a resin film. Although the washing time is not particularly limited, it is preferably 1 to 300 seconds, and more preferably 1 to 60 seconds. The temperature of the cleaning solution in the washing step 1 must 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, the washing treatment is performed at 5 to 40 ° C. However, since the performance problem does not occur even if there is no washing step 1, the washing step can be omitted.

(Step of making a cross-linking agent and / or a water-resistant agent)

After the dyeing step or the washing step 1, a step of containing a crosslinking agent and / or a water-resistant agent may be performed. Although the method of making a resin film contain a crosslinking agent and / or a water resistance agent is preferable to immerse in a processing solution, you may coat or coat a processing solution on a resin film. The treatment solution contains at least one kind of a cross-linking agent and / or a water-resistant agent and a solvent. The temperature of the processing solution in this step is preferably 5 to 70 ° C, and more preferably 5 to 50 ° C. The processing time in this step is preferably 30 seconds to 6 minutes, and more preferably 1 to 5 minutes.

As the crosslinking agent, for example, boron compounds such as boric acid, borax, or ammonium borate, polyaldehydes such as glyoxal or glutaraldehyde, biuret type, trimeric isocyanate type, or blocked polyisocyanates can be used. Compounds, titanium compounds such as titanyl sulfate, and the like, but other glycol-glycidyl alcohols, polyamido-epoxychloropropane, and the like can also be used. Examples of the water-resistant agent include succinic acid peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerol diglycidyl ether, ammonium chloride, or It is magnesium chloride or the like, but boric acid is preferably used. As the solvent used in the crosslinking agent and / or the water-resistant agent, water is preferred but not limited. The concentration of the cross-linking agent and / or the water-resistance agent may be appropriately determined by those having ordinary knowledge in the art depending on the type. When boric acid is used as an example, the concentration in the treatment solution is 0.1 to 6.0% by mass. Preferably, 1.0 to 4.0% by mass is more preferable. However, it is not necessary to include a cross-linking agent and / or a water-repellent agent. In a case where it is desired to shorten the time, and a cross-linking treatment or a water-repellent treatment is not necessary, this processing step may be omitted.

(Extended steps)

After performing a dyeing step, a washing step 1, or a step containing a cross-linking agent and / or a water-resistant agent, an extension step is performed. The stretching step is performed by uniaxially stretching the resin film. As the stretching method, either a wet stretching method or a dry stretching method can be used. The stretching 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 dry stretching method, when the stretching heating medium is an air medium, it is preferable that the temperature of the air medium stretches the resin film at a normal temperature to 180 ° C. The humidity is preferably in an environment of 20 to 95% RH. Examples of the heating method include, but are not limited to, an inter-roller area stretching method, a drum heating stretching method, a pressure stretching method, and an infrared heating stretching method. The stretching step may be performed by one-stage extension, but may also be performed by multi-stage extension of two or more stages.

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. The stretching treatment is preferably performed while immersing in a solution containing at least one kind of a crosslinking agent and / or a water-resistant agent. As a crosslinking agent and a water-resistant agent, the same thing as the above-mentioned about the process of making a crosslinking agent and / or a water-resistant agent can be used. The concentration of the cross-linking agent and / or the water-resistant agent in the solution in the extension step is, for example, preferably from 0.5 to 15% by mass, and more preferably from 2.0 to 8.0% by mass. The elongation temperature is preferably treated at 40 to 70 ° C, and more preferably 45 to 60 ° C. Although the extension time is usually 30 seconds to 20 minutes, it is more preferably 2 to 5 minutes. Although the wet stretching step can be performed in a single stage, it can also be performed in a multi-stage extension of two or more stages.

(Washing step 2)

After the stretching step, a cross-linking agent and / or a water-resistant agent or impurities are deposited on the surface of the resin film. Therefore, a cleaning step of washing the surface of the resin film (hereinafter, also referred to as a "washing step") can be performed. 2"). The washing time is preferably from 1 second to 5 minutes. The cleaning method is preferably a resin film immersed in a cleaning solution, but it can also be cleaned by coating or coating the solution on the resin film. As the cleaning solution, water is preferred. It can be washed in one stage, or it can be processed in two or more stages. The temperature of the solution in the washing step is not particularly limited, but is usually 5 to 50 ° C, preferably 10 to 40 ° C.

Examples of the processing liquid or solvent used in the processing steps up to this point include, in addition to water, dimethylsulfinium, N-methylpyrrolidone, methanol, ethanol, propanol, isopropyl Alcohols, glycerol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol or alcohols such as trimethylolpropane, amines such as ethylenediamine and diethylenetriamine, etc., but not Limited to these. The treatment liquid or its solvent is preferably water. These treatment liquids or their solvents may be used alone or as a mixture of two or more.

(Drying step)

After the stretching step or the washing step 2, a resin film drying step is performed. Although the drying process can be performed by natural drying, in order to improve the drying efficiency, it can be performed by the compression of the drum, the removal of water on the surface caused by the air knife, or the suction drum, etc., and / Alternatively, it may be performed by air drying. The drying treatment temperature is preferably a drying treatment at 20 to 100 ° C, and more preferably a drying treatment at 60 to 100 ° C. The drying treatment time is, for example, 30 seconds to 20 minutes, but preferably 5 to 10 minutes.

In the manufacturing method of the polarizing element, the swelling degree of the substrate in the swelling step, the mixing ratio of each azo compound in the dyeing step, the temperature of the dyeing solution, pH, sodium chloride or sodium sulfate (also known as thenardite) , The type of salt such as sodium tripolyphosphate or its concentration, the dyeing time, and the stretching ratio in the re-extension step are such that the polarizing element satisfies at least one of the following conditions (i) to (v) The adjustment is appropriate, and it is more suitable to further satisfy the conditions (vi) and (vii).

(i) Regarding parallel bit transmittance, the absolute value of the difference between the average transmittance of 420nm to 480nm and the average transmittance of 520nm to 590nm becomes 2.5 or less, and the average transmittance of 520nm to 590nm is equal to the average of 600nm to 640nm. The absolute value of the difference in transmittance becomes 2.0 or less.

(ii) Regarding the vertical bit transmittance, the absolute value of the difference between the average transmittance of 420nm to 480nm and the average transmittance of 520nm to 590nm becomes 10 or less, and the average transmittance of 520nm to 590nm is equal to the average of 600nm to 640nm. The absolute value of the difference in transmittance becomes 2.0 or less.

(iii) The monomer transmittance becomes 35% to 65%.

(iv) Each of the absolute values of a * value and b * value is 1.0 or less in the polarizing element alone and 2.0 or less in the parallel position.

(v) Each of the absolute values of a * value and b * value measured in the vertical position becomes 2 or less.

(vi) Regarding parallel bit transmittance, the average transmittance of 520 nm to 590 nm becomes 25 to 45%.

(vii) The difference between the average transmittance of 380nm to 420nm and the average transmittance of 420nm to 480nm becomes 15% or less, and the difference between the average transmittance of 480nm to 520nm and the average transmittance of 420nm to 480nm becomes 15% or less The difference between the average transmittance of 480nm to 520nm and the average transmittance of 520nm to 590nm becomes 15% or less, and / or the difference of the average transmittance of 640nm to 780nm and the average transmittance of 600nm to 640nm becomes 20 %the following.

By the above method, a polarizing element containing at least a combination of an azo compound represented by formula (1a) or (1b) and an azo compound represented by formula (2) can be manufactured. Although such a polarizer has higher transmittance and higher polarization than conventional polarizers, it can express high-quality paper-like properties when two polarizers are arranged in such a way that the absorption axis directions are parallel to each other. It has a white color and a neutral color (neutral gray) hue, and a high-contrast polarizer can be produced. In addition, the polarizing element has high durability against high temperature and high humidity.

<Polarizer>

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

The transparent protective layer is a protective film formed using a transparent substance. The protective film is a layered film that can maintain the shape of the polarizing element, and is preferably a plastic, which is excellent in transparency and mechanical strength, thermal stability, moisture shielding, and the like. The same function may be provided by forming the same layer. Examples of plastics constituting the protective film include polyester resins, acetate resins, polyether resins, polycarbonate resins, polyamide resins, polyimide resins, Thermoplastic resins such as polyolefin resins and acrylic resins; films obtained from thermosetting resins such as acrylic, urethane, acrylate, epoxy, and silicone, or ultraviolet curable resins Among them, as the polyolefin-based resin, an amorphous polyolefin-based resin and a polymerization unit having a cyclic polyolefin such as a norbornene-based monomer or a polycyclic norbornene-based monomer can be cited. Resin. Generally, it is better to choose a protective film that does not hinder the performance of the polarizing element after laminating the protective film. As such a protective film, triethyl cellulose (a cellulose acetate resin) is used. TAC) and norbornene are particularly preferred. In addition, the protective film may be subjected to hard coating treatment, treatment for preventing reflection, prevention of sticking, diffusion, anti-glare, and the like, without impairing the effects of the present invention.

The polarizing plate preferably includes an adhesive layer between the transparent protective layer and the polarizing element for bonding the transparent protective layer to the polarizing element. The adhesive constituting the adhesive layer is not particularly limited, but a polyvinyl alcohol-based adhesive is preferred. Examples of the polyvinyl alcohol-based adhesive include, but are not limited to, GOHSENOL NH-26 (manufactured by Nippon Gosei Co., Ltd.) and EXCEVAL RS-2117 (manufactured by Kuraray Co., Ltd.). A crosslinking agent and / or a water resistance agent may be added to the adhesive. As the polyvinyl alcohol-based adhesive, a maleic anhydride-isobutylene copolymer is preferably used, and an adhesive mixed with a cross-linking agent as required can be used. Examples of the maleic anhydride-isobutylene copolymer include ISOBAM # 18 (made by Kuraray), ISOBAM # 04 (made by Kuraray), ammonia modified ISOBAM # 104 (made by Kuraray), and ammonia modified Quality ISOBAM # 110 (made by Kuraray), imidized ISOBAM # 304 (made by Kuraray), and imidized ISOBAM # 310 (made by Kuraray). As the crosslinking agent at this time, a water-soluble polyvalent epoxy compound can be used. Examples of the water-soluble polyvalent epoxy compound include Denacol EX-521 (manufactured by Nagase ChemteX) and TETRAD-C (manufactured by Mitsui GAS Chemical Co., Ltd.). Moreover, as an adhesive other than a polyvinyl alcohol resin, well-known adhesives, such as an amine ester type, an acrylic type, and an epoxy type, can also be used. In particular, it is preferable to use polyvinyl alcohol modified with acetamidine, and it is more preferable to use polyaldehyde as the crosslinking agent. In addition, for the purpose of improving the adhesion of the adhesive or improving the water resistance, additives such as zinc compounds, chlorides, and iodides can be contained alone or simultaneously at a concentration of about 0.1 to 10% by mass. The additives are not particularly limited, and those skilled in the art can appropriately select them. After the transparent protective layer and the polarizing element are bonded with an adhesive, the polarizing plate can be obtained by drying or heat treatment at an appropriate temperature.

The polarizing plate depends on the situation, for example, when it is attached to a display device such as liquid crystal or organic electroluminescence (commonly referred to as OLED or OEL). The surface of the protective layer or film that will become a non-exposed surface afterwards can be set to improve the visual field Various functional layers that improve the angle and / or contrast, layers or films that enhance brightness. Various functional layers, such as a layer or a film that controls the phase difference. Polarizers, such films or display devices, are preferably adhered with a pressure-sensitive adhesive.

The polarizing plate may include various known functional layers such as an antireflection layer, an antiglare layer, and a hard coat layer on the exposed surface of the protective layer or film. In the production of the layer having various functions, although a coating method is preferred, a film having this function may be bonded via an adhesive or an adhesive.

Although the polarizing plate of the present invention has high transmittance and high polarization, it can realize achromaticity, especially when displaying white, it can express high-quality white like paper, and can exhibit high contrast and high durability. Sexual polarizer.

The polarizing element or polarizing plate of the present invention is provided with a protective layer or a functional layer and transparent supports such as glass, crystal, sapphire and the like according to needs, and can be applied to liquid crystal projectors, electronic computers, clocks, notebook computers, word processing Cameras, LCD TVs, polarized lenses, polarized glasses, car navigators, and measuring devices or displays inside and outside the house. In particular, the polarizing element or polarizing plate of the present invention is suitable for application to liquid crystal display devices, such as reflective liquid crystal display devices, transflective liquid crystal display devices, and organic electroluminescence. The liquid crystal display device using the polarizing element or polarizing plate of the present invention can present high-quality white paper and high contrast. The liquid crystal display device is a liquid crystal display device having high durability, high reliability, long-term high contrast, and high color reproducibility.

    [Example]    

Hereinafter, the present invention will be described in more detail through examples, but the present invention is not limited thereto.

[Example 1]

A polyvinyl alcohol film (VF-PS manufactured by Kuraray Co., Ltd.) having an average degree of polymerization of 2400 or more with a saponification degree of 99% or more was immersed in warm water at 45 ° C. for 2 minutes, and subjected to a swelling treatment to set the stretching ratio to 1.30 times. Compound Example [1a-25] 0.32 parts by mass, Compound Example [2-4] 0.20 parts by mass containing 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, as a compound of formula (1a) In the 45 ° C dyeing solution, the swollen film was immersed for 4 minutes and 30 seconds so that the film contained an azo compound. The obtained film was immersed in a 40 ° C aqueous solution containing 20 g / l of boric acid (manufactured by Societa Chimica Larderello s.p.a.) for 1 minute. The immersed film was stretched for 5.0 minutes in a 50 ° C aqueous solution containing 30.0 g / l of boric acid while being stretched to 5.0 times. The obtained film was kept in this tight state, and was washed by immersion in water at 25 ° C for 20 seconds. The washed film was dried at 70 ° C for 9 minutes to obtain a polarizing element. For this polarizing element, a polyvinyl alcohol (NH-26 manufactured by Japan VAM & POVAL) was dissolved in water at 4% as an adhesive, and an alkali-treated triethylammonium cellulose film (manufactured by Fujifilm) was used. ZRD-60) were laminated to obtain a polarizing plate. The obtained polarizing plate maintains the optical properties of the above-mentioned polarizing element, especially the single transmittance, hue, and polarization. This polarizing plate was used as a measurement sample of Example 1.

[Example 2]

Except the use of 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, and 1.5 parts by mass of anhydrous sodium sulfate, the compound example [1a-25] as a compound of formula (1a) was 0.32 parts by mass as described in formula (2) The compound CI Direct Blue 69 was 0.22 parts by mass in place of the dyeing liquid used in Example 1. The rest was the same as in Example 1 to produce a polarizing plate.

[Example 3]

Except the use of 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, and 1.5 parts by mass of anhydrous sodium sulfate, the compound example [1a-25] as a compound of formula (1a) was 0.32 parts by mass as described in formula (2) Compound Example [2-4] of the compound is 0.20 parts by mass, and Compound Example [3-1] as the compound of the formula (3) is 0.27 parts by mass in place of the dyeing solution used in Example 1, and the rest are the same as in the Example 1 A polarizing plate was produced in the same manner.

[Example 4]

A polarizing plate was produced in the same manner as in Example 3 except that the content time of the azo compound was changed from 4 minutes and 30 seconds to 3 minutes.

[Example 5]

A polarizing plate was produced in the same manner as in Example 3 except that the content time of the azo compound was changed from 4 minutes and 30 seconds to 2 minutes.

[Example 6]

Except the use of 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, and 1.5 parts by mass of anhydrous sodium sulfate, the compound example [1a-25] as a compound of formula (1a) was 0.32 parts by mass as described in formula (2) Compound Example [2-4] of the compound is 0.20 parts by mass of Compound Example [3-2] as a compound of formula (3) (n = 1 is 24%, n = 2 is 71%, and n = 3 is 5%) The polarizing plate was produced in the same manner as in Example 1 except that the dyeing liquid used in Example 1 was replaced by 0.24 parts by mass.

[Example 7]

A polarizing plate was produced in the same manner as in Example 6 except that the content time of the azo compound was changed from 4 minutes and 30 seconds to 3 minutes.

[Example 8]

A polarizing plate was produced in the same manner as in Example 6 except that the content time of the azo compound was changed from 4 minutes and 30 seconds to 2 minutes.

[Example 9]

A polarizing film was produced in the same manner as in Example 6 except that the content time of the azo compound was changed from 4 minutes and 30 seconds to 1 minute.

[Example 10]

Except for using 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, and 1.5 parts by mass of anhydrous sodium sulfate, 0.32 parts by mass of Compound Example [1a-25] as a compound of formula (1a), as described in Formula (2) Compound CI Direct Blue 69 was 0.22 parts by mass, and Compound Example [3-1] as a compound of formula (3) was replaced by 0.27 parts by mass in place of the dyeing solution used in Example 1. The rest was the same as in Example 1. And make a polarizing plate.

[Example 11]

Except for using 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, and 1.5 parts by mass of anhydrous sodium sulfate, 0.32 parts by mass of Compound Example [1a-25] as a compound of formula (1a), as described in Formula (2) The CI Direct Blue 69 of the compound is 0.22 parts by mass, and the compound example [3-2] (n = 1 is 24%, n = 2 is 71%, n = 3 is 5%) as a compound of the formula (3) is 0.20 mass Instead of the dyeing liquid used in Example 1. The remainder was fabricated in the same manner as in Example 1 to produce a polarizing plate.

[Example 12]

Except using 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, and 1.5 parts by mass of anhydrous sodium sulfate, the compound example [1a-25] as a compound of formula (1a) was 0.32 parts by mass, as described in formula (2) Compound Example [2-4] of the compound was 0.20 parts by mass and CI Direct Yellow 28 was 0.22 parts by mass in place of the dyeing liquid used in Example 1. The rest was the same as in Example 1 to produce a polarizing film.

[Example 13]

Except for using 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, and 1.5 parts by mass of anhydrous sodium sulfate, Compound Example [1a-13] as a compound of formula (1a) was 0.35 parts by mass as described in formula (2) Compound Example [2-4] of the compound was 0.20 parts by mass, and Compound Example [3-1] as the compound of the formula (3) was 0.27 parts by mass in place of the dyeing solution used in Example 1, and the rest were the same as in the Example. 1 In the same manner, a polarizing film was produced.

[Example 14]

Except for using 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, and 1.5 parts by mass of anhydrous sodium sulfate, 0.29 parts by mass of Compound Example [1a-5] as a compound of formula (1a), as described in Formula (2) Compound Example [2-4] of the compound was 0.20 parts by mass, and Compound Example [3-1] as the compound of the formula (3) was 0.27 parts by mass in place of the dyeing solution used in Example 1, and the rest were the same as in the Example. 1 In the same manner, a polarizing film was produced.

[Example 15]

Except for using 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, and 1.5 parts by mass of anhydrous sodium sulfate, 0.32 parts by mass of Compound Example [1a-25] as a compound of formula (1a) was used as the compound described in Formula (2) Compound Example [2-13] was 0.21 parts by mass, and Compound Example [3-1] as a compound of formula (3) was 0.27 parts by mass. Instead of the dyeing solution used in Example 1, the rest were the same as in Example 1. Similarly, a polarizing film was produced.

[Example 16]

Except for using 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, and 1.5 parts by mass of anhydrous sodium sulfate, 0.32 parts by mass of Compound Example [1a-25] as a compound of formula (1a), as described in Formula (2) Compound Example [2-15] of the compound was 0.243 parts by mass, and Compound Example [3-1] as the compound of the formula (3) was 0.27 parts by mass in place of the dyeing solution used in Example 1, and the rest were the same as in the Example. 1 In the same manner, a polarizing film was produced.

[Example 17]

Except for using 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, and 1.5 parts by mass of anhydrous sodium sulfate, 0.32 parts by mass of Compound Example [1a-25] as a compound of formula (1a), as described in Formula (2) Compound Example [2-23] of the compound was 0.218 parts by mass, and Compound Example [3-1] as the compound of the formula (3) was 0.27 parts by mass in place of the dyeing solution used in Example 1, and the rest were the same as in the Example. 1 In the same manner, a polarizing film was produced.

[Example 18]

Except the use of 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, and 1.5 parts by mass of anhydrous sodium sulfate, as a compound example of the compound of the formula (1b) [1b-33] was 0.15 part by mass of a compound example of the compound of the formula (2) [2-4] is 0.10 parts by mass of Compound Example [3-1] as a compound of formula (3) is 0.05 parts by mass in place of the dyeing liquid used in Example 1, and the content time of the azo compound is changed from 4 to 30 Except that the seconds were changed to 8 minutes and 00 seconds, the rest was the same as in Example 1 to produce a polarizing film.

[Example 19]

A polarizing film was produced in the same manner as in Example 18 except that the time during which the swollen film contained an azo compound in the dyeing step was changed from 8 minutes to 4 minutes.

[Example 20]

Except the use of 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, and 1.5 parts by mass of anhydrous sodium sulfate, as a compound example of the compound of the formula (1b) [1b-33] was 0.15 part by mass of a compound example of the compound of the formula (2) [2-4] 0.10 parts by mass of a compound example [3-2] as a compound of the formula (3) (n = 1 is 24%, n = 2 is 71%, n = 3 is 5%) is 0.05 parts by mass A polarizing film was produced in the same manner as in Example 18 except that the dyeing liquid used in Example 19 was replaced.

[Example 21]

Except the use of 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, and 1.5 parts by mass of anhydrous sodium sulfate, as a compound example of the compound of the formula (1b) [1b-33] was 0.15 part by mass of a compound example of the compound of the formula (2) [2-4] A polarizing film was produced in the same manner as in Example 18 except that the dyeing solution used in Example 19 was replaced by 0.10 parts by mass and CI Direct Yellow 28 was 0.05 parts by mass.

[Example 22]

Except using 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, and 1.5 parts by mass of anhydrous sodium sulfate, as a compound example of the compound of the formula (1b) [1b-56] is 0.25 part by mass, and as a compound example of the compound of the formula (2) [2-4] 0.10 parts by mass of the compound example [3-2] as a compound of formula (3) (n = 1 is 24%, n = 2 is 71%, n = 3 is 5%) is 0.05 parts by mass A polarizing film was produced in the same manner as in Example 18 except that the dyeing liquid used in Example 19 was replaced.

[Example 23]

Except for using 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, and 1.5 parts by mass of anhydrous sodium sulfate, 0.22 parts by mass of the compound example [1b-35] as a compound of the formula (1b) was used as a compound example of the compound of the formula (2) [2-4] 0.10 parts by mass of the compound example [3-2] as a compound of formula (3) (n = 1 is 24%, n = 2 is 71%, n = 3 is 5%) is 0.05 parts by mass A polarizing film was produced in the same manner as in Example 18 except that the dyeing liquid used in Example 19 was replaced.

[Example 24]

Except the use of 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, and 1.5 parts by mass of anhydrous sodium sulfate, 0.22 parts by mass of the compound example [1b-35] as a compound of the formula (1b), and compound examples of the compound of the formula (2) [2-17] 0.10 parts by mass of Compound Example [3-1] as a compound of formula (3) was replaced by 0.05 parts by mass in place of the dyeing solution used in Example 19, and the rest was the same as in Example 18. And make a polarizing film.

[Example 25]

Except using 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, and 1.5 parts by mass of anhydrous sodium sulfate, the compound example [1a-25] as a compound described in formula (1a) was 0.20 parts by mass, and as in formula (1b) Compound Example [1b-33] of the compound described in) is 0.15 parts by mass, Compound Example [2-17] as the compound described in Formula (2) is 0.1 part by mass, and Compound Example as the compound of formula (3) [3-1] A polarizing film was produced in the same manner as in Example 1 except that the dyeing solution used in Example 1 was replaced by 0.05 parts by mass.

[Example 26]

A polarizing film was produced in the same manner as in Example 25 except that the content time of the azo compound was changed from 4 minutes and 30 seconds to 3 minutes.

[Example 27]

Except using 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, and 1.5 parts by mass of anhydrous sodium sulfate, the compound example [1a-25] as the compound described in formula (1a) is 0.20 parts by mass, and as in formula (1b) Compound Example [1b-44] of the compound described in) is 0.17 parts by mass, and Compound Example [2-4] as the compound described in Formula (2) is 0.17 part by mass, as a compound example of the compound of Formula (3) [3-1] The polarizing film was produced in the same manner as in Example 1 except that the dyeing solution used in Example 1 was replaced by 0.05 parts by mass.

[Example 28]

Except using 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, and 1.5 parts by mass of anhydrous sodium sulfate, the compound example [1a-25] as the compound described in formula (1a) is 0.20 parts by mass, and as in formula (1b) Compound Example [1b-56] of the compound described in) is 0.23 parts by mass, and Compound Example [2-4] as the compound described in Formula (2) is 0.17 part by mass, as a compound example of the compound of Formula (3) [3-1] The polarizing film was produced in the same manner as in Example 1 except that the dyeing solution used in Example 1 was replaced by 0.05 parts by mass.

[Example 29]

Except using 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, and 1.5 parts by mass of anhydrous sodium sulfate, the compound example [1a-13] as the compound described in formula (1a) is 0.13 parts by mass and as in formula (1b) Compound Example [1b-35] of the compound described in) is 0.15 parts by mass, and Compound Example [2-4] as the compound described in Formula (2) is 0.17 part by mass, as a compound example of the compound of Formula (3) [3-1] The polarizing film was produced in the same manner as in Example 1 except that the dyeing solution used in Example 1 was replaced by 0.05 parts by mass.

[Comparative Examples 1 to 5]

Except that the azo compound-containing aqueous solution (dyeing solution) in Example 1 was set to have the same composition as that in Example 1 of Patent Document 3, and the time containing the azo compound (the immersion time of the dyeing tank with the swollen PVA film) ) To 12 minutes in Comparative Example 1, 10 minutes in Comparative Example 2, 8 minutes in Comparative Example 3, 5 minutes and 30 seconds in Comparative Example 4, and 4 in Comparative Example 5. Except for minutes, the rest was the same as in Example 1 to produce a polarizing plate containing an azo compound.

[Comparative Example 6]

A high-transmittance dye-based polarizing plate SHC-115 manufactured by Polatechno Corporation having a neutral gray color was obtained as a measurement sample.

[Comparative Example 7]

As a measurement sample, a dye-based polarizing plate SHC-128 manufactured by Polatechno Co., Ltd. having a neutral gray and high contrast was obtained.

[Comparative Examples 8 to 13]

According to the manufacturing method of Comparative Example 1 of Japanese Patent Application Laid-Open No. 2008-065222, the time for containing iodine is set to 5 minutes and 30 seconds in Comparative Example 8, 4 minutes and 45 seconds in Comparative Example 9, and It is 4 minutes and 15 seconds in 10, 3 minutes and 30 seconds in Comparative Example 11, 4 minutes and 00 seconds in Comparative Example 12, and 5 minutes and 15 seconds in Comparative Example 13. An iodine system containing no azo compound was produced. A polarizing plate was used as a measurement sample.

[Comparative Example 14]

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

[Comparative Example 15]

A polarizing plate was produced as described in Example 1 of Japanese Patent Application Laid-Open No. 11-218611 on dye-based polarizing plates.

[Comparative Example 16]

A polarizing plate was produced as described in Example 3 of Japanese Patent Application Laid-Open No. 2001-033627 on a dye-based polarizing plate.

[Comparative Example 17]

A polarizing plate was produced as described in Example 1 of Japanese Patent Application Laid-Open No. 2004-251962 on a dye-based polarizing plate.

[Comparative Example 18]

In addition to using the same-colored dichroic azo compound with a dianidine skeleton, 0.29 parts by mass of CI Direct Blue 6 to replace 0.1 parts by mass of the compound example [2-17], and the vertical position The transmittance is almost constant, and the color will be black. The rest is the same as in Example 25 to make a polarizing film.

[Evaluation]

Evaluation of the measurement samples obtained in Examples 1 to 29 and Comparative Examples 1 to 18 was performed as follows.

(a) Single unit transmittance Ts, parallel position transmittance Tp, and vertical position transmittance Tc

The individual transmittance Ts, the parallel transmittance Tp, and the vertical transmittance Tc of each measurement sample were measured using a spectrophotometer ("U-4100" manufactured by Hitachi, Ltd.). Here, the monomer transmittance Ts is the transmittance at each wavelength when measuring with a single measurement sample. The parallel transmittance Tp is the spectral transmittance of each wavelength measured by superposing two measurement samples so that their absorption axis directions are parallel. The vertical transmittance Tc is a spectral transmittance measured by superposing two polarizing plates so that their absorption axes become vertical. The measurement is performed across a wavelength of 400 to 700 nm.

The average values of the parallel bit transmittance Tp from 420 to 480 nm, the average values from 520 to 590 nm, and the average values from 600 to 640 nm are determined.

(b) Transmittance Ys, Yp, Yc, and Yc

The individual transmittance Ys, the parallel transmittance Yp, and the vertical transmittance Yc of each measurement sample were determined. The cell transmittance Ys, the parallel bit transmittance Yp, and the vertical bit transmittance Yc are obtained for the above-mentioned monomers at a predetermined wavelength interval dλ (here, 5 nm) in a wavelength region of 400 to 700 nm. Each of the transmittance Ts, the parallel transmittance Tp, and the vertical transmittance Tc is corrected to the transmittance of visual sensitivity in accordance with JIS Z 8722: 2009. Specifically, the above-mentioned monomer transmittance Ts, parallel bit transmittance Tp, and vertical bit transmittance Tc are substituted into the following formulae (I) to (III), and calculated respectively. In the following formulae (I) to (III), Pλ is a spectral distribution representing standard light (C light source), and yλ is a 2-degree field of view color matching function. The results are shown in Tables 1 and 2.

(c) Polarization ρy

The degree of polarization ρy of each measurement sample was obtained by substituting the parallel position transmittance Yp and the vertical position transmittance Yc into the following equations. The results are shown in Tables 3 and 4.

ρy = {(Yp-Yc) / (Yp + Yc)} ^1/2 × 100

(d) Chroma a * value and b * value

For each measurement sample, the chromaticity a * value and b * value in each of the measurement of the monomer transmittance Ts and the measurement of the para-parallel transmission Tp were measured in accordance with JIS Z 8781-4: 2013. In the measurement, the above-mentioned spectrophotometer was used, and the transmission color and the reflection color were both incident from the outdoor side and measured. The light source is a C light source. The results are shown in Tables 3 and 4. Here, a * -s and b * -s, a * -p, and b * -p correspond to the chromaticity a at the time of measurement of each of the unit transmittance Ts and the para-parallel transmittance Tp, respectively. * Value and b * value.

(e) Absolute value of the difference in average transmittance between the two wavelength bands

Obtain the absolute value of the difference between the average value of the parallel position transmittance Tp of each measurement sample in 520 to 590 nm and the average value in 420 to 480 nm, and the average value in 520 to 590 nm and 600 to 640 nm The absolute value of the difference between the average values is shown in Tables 3 and 4.

As shown in Tables 1 to 4, the measurement samples of Examples 1 to 29 show that the absolute values of a * -s and b * -s are both 5.0 or less, and the absolute values of a * -p and b * -p. Both are below 2.0, the hue of appearance is very neutral and paper white. In addition, the para-parallel transmittance Tp of the measurement samples of Examples 1 to 29 was an average of 25% or more at 520 to 590 nm. In addition, the absolute value of the difference between the average parallel transmittance Tp of the measurement samples of Examples 1 to 29 in 420 to 480 nm and the average in 520 to 590 nm was 1.5% or less, and it was 520 to The absolute value of the difference between the average value at 590 nm and the average value at 590 to 640 nm is 2.0% or less, and both are very low values.

On the other hand, in the measurement samples of Comparative Examples 1 to 5, when compared with the examples showing the same monomer transmittance (Ys), the polarization degree (ρy) was low, and the parallel transmittance was the same as that shown in the examples. (Yp) When compared with the examples, Yc is high, so it can be seen that the polarization function is lower than the examples. For example, when the polarization degree (ρy) of Example 3 having the same Ys is compared with that of Comparative Example 1, it is 99.95% with respect to Example 3, 98.15% with Comparative Example 1, and Example 3 with Comparative Example 1, Polarization is 1.8% higher. The comparison (Yp / Yc) with respect to Example 3 is 1985, Comparative Example 1 has a low value of about 53, and Example 3 has a high contrast of about 37 times that of Comparative Example 1.

In addition, when comparing the polarization degrees (ρy) of Example 25 and Comparative Example 3 showing the same Ys, it was 99.61% compared to Example 25, and Comparative Example 3 was about 95.57%. The polarization degree of Example 25 was compared with Compared with Example 3, it is 4.04% higher. The comparison (Yp / Yc) with respect to Example 25 is 256, Comparative Example 3 is about 22, and Example 25 has a high contrast of 11 times or more than that of Comparative Example 3.

In addition, when the parallel bit transmittance (Yp) of Example 2 having the same degree of polarization (ρy) was compared with Comparative Example 2, it was 37.68% compared to Example 2, 33.70% of Comparative Example 2, and Example 2 Compared with Comparative Example 2, Yp is 3.98% higher, indicating that even with the same degree of polarization, it is a bright polarizer.

Moreover, when Example 20 having the same degree of polarization (ρy) is compared with Comparative Example 1, Yp is 38.25% relative to Example 20 and 32.72% in Comparative Example 1. In the same polarization, Example 20 is compared with Compared with Example 1, Yp is 5.53% higher, showing that even with the same degree of polarization, it is a bright polarizer.

In the measurement samples of Comparative Examples 6 to 13 and 15 to 18, the absolute value of the difference between the average values between the two wavelength bands of the parallel bit transmittance Tp shown in Table 4 shows a high value.

The above shows that the polarizing plates of Examples 1 to 29, while maintaining a high single transmission and parallel transmission, can still present a high-quality paper-like white in parallel, and, The monomer has a neutral color (neutral gray). In addition, it can be seen that the polarizing plates of Examples 1 to 29 have high polarization while maintaining high transmittance and exhibiting achromaticity in parallel positions.

(f) Durability test

The measurement samples of Examples 1 to 29 and Comparative Examples 8 to 14 were left in an environment of 85 ° C. and a relative humidity of 85% RH for 240 hours. As a result, in the measurement samples of Examples 1 to 29, no change in transmittance and hue was observed. In contrast, the polarized light of Comparative Examples 8 to 14 decreased by more than 10%, and b * -c was lower than -10, and the color of the appearance turned blue, especially when two pieces of measurement samples were arranged in the vertical position. , Black will seriously appear blue. In particular, Comparative Example 14 showed a significant increase in transmittance and a decrease in polarization. From this fact, it can be seen that the liquid crystal display device using the polarizing plates of Examples 1 to 29 is a liquid crystal display device having high reliability, long-term high contrast, and high color reproducibility.

Claims (11)

A polarizing element comprising an azo compound represented by formula (1a) or (1b) or a salt thereof, and an azo compound represented by formula (2) or a salt thereof, In the formula, Ar ₁ is a phenyl group or a naphthyl group having at least one substituent, and Rr ₁ to Rr ₄ are each independently a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a sulfonic acid group. Lower alkoxy, In the formula, Av ₁ is a phenyl group or a naphthyl group having at least one substituent selected from a sulfonic acid group and a carboxyl group, and Rv ₁ to Rv ₆ are each independently a hydrogen atom, a lower alkyl group, or a lower alkoxy group. Or a lower alkoxy group having a sulfonic group, Xv ₁ means that it may have at least one selected from the group consisting of a lower alkyl group, a lower alkoxy group, a sulfonic group, an amine group, a lower alkylamino group, a hydroxyl group, and a carboxyl group And amine groups of substituents in the group of carboxyethylamino groups, phenylamino groups, phenylazo groups, naphthotriazolyl groups, or benzamidineamino groups In the formula, Ag ₁ represents a phenyl group or a naphthyl group having a substituent, Bg and Cg are each independently expressed by a formula (BC-N) or a formula (BC-P), and at least one of them is a formula (BC -N), Xg ₁ represents an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, or a benzamidineamino group which may have a substituent, In the formula, Rg ₁ is a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfonic acid group, and k is an integer of 0 to 2, Rg ₂ and Rg ₃ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfonic acid group.     The polarizing element according to item 1 of the scope of patent application contains both a compound represented by formula (1a) or a salt thereof and at least one compound represented by formula (1b) or a salt thereof.         The polarizing element according to item 1 or 2 of the scope of patent application, wherein Cg is represented by the formula (BC-N).     The polarizing element according to any one of claims 1 to 3, wherein the azo compound represented by formula (2) is represented by formula (2 '), In the formula, Ag ₁ and Xg ₁ are as defined in formula (2), Rg ₄ and Rg ₅ are the definitions for Rg ₁ as in formula (BC-N), and k ₁ and k ₂ are as in formula (BC-N ) For k. The polarizing element according to any one of claims 1 to 4, further comprising an azo compound represented by formula (3) or a salt thereof, In the formula, Ay ₁ represents a sulfonic acid group, a carboxyl group, a hydroxyl group, a lower alkyl group, or a lower alkoxy group, and Ry ₁ to Ry ₄ each independently represent a hydrogen atom, a sulfonic acid group, a lower alkyl group, or Lower alkoxy, p is an integer representing 1 to 3.     The polarizing element according to any one of claims 1 to 5, wherein the polarizing element contains a polyvinyl alcohol-based resin film as a base material.         The polarizing element according to any one of claims 1 to 6, in which the absolute value of a * value and b * value obtained when measuring the transmittance of natural light according to JIS Z 8781-4: 2013 In the aforementioned polarizing element alone, both are 5.0 or less, and in a state where two pieces of the aforementioned polarizing element are arranged so that their absorption axis directions are parallel to each other, they are both 2.0 or less.         The polarizing element according to any one of claims 1 to 7, in which two pieces of the aforementioned polarizing elements are superimposed so that the absorption axis directions become parallel to each other and measured to obtain an average transmission of 420 nm to 480 nm. The absolute value of the difference between the transmittance and the average transmittance of 520 nm to 590 nm is 2.5% or less, and the absolute value of the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 600 nm to 640 nm is 2.0% or less.         The polarizing element according to any one of claims 1 to 8 in the patent application scope, wherein a single transmittance of the aforementioned polarizing element is 35% to 65%, and when the two polarizing elements are oriented in the direction of their absorption axis, The average transmissivity of 520nm to 590nm obtained by overlapping and arranged in a parallel manner is 25% to 45%.         A polarizing plate includes the polarizing element according to any one of claims 1 to 9 and a transparent protective layer provided on one or both sides of the polarizing element.         A liquid crystal display device is provided with the polarizing element according to any one of claims 1 to 9 or a polarizing plate according to claim 10.