TWI734858B - 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 polarizing element

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

The polarizing element is generally manufactured by adsorbing iodine or dichroic dye aligned with a dichroic dye on a polyvinyl alcohol-based resin film. Here, the polarizing element has a polarizing plate obtained by bonding a protective film made of triacetyl cellulose or the like with an adhesive layer interposed therebetween, and is used in a liquid crystal display device or the like. Polarizing plates that use iodine as a dichroic pigment are called iodine-based polarizing plates. On the other hand, polarizing plates that use dichroic dyes such as dichroic azo compounds as dichroic pigments are called iodine-based polarizing plates. Dye-based polarizing plate. Among these, the dye-based polarizing plate has high heat resistance, high humidity and heat durability, and high stability. It also has the characteristics of high color selectivity through the blending of pigments. On the other hand, it has the same degree of polarization. When comparing the iodine-based polarizers, there is a problem of low transmittance and contrast. Therefore, in addition to maintaining high durability and diversified color selectivity, a polarizing element with higher transmittance and high polarization characteristics is desired.

In addition, even for dye-based polarizers with diverse color selectivity, the polarizing elements up to now are based on a method in which the absorption axis directions of two polarizing elements are parallel to each other (hereinafter, also referred to as "parallel position"). Overlapping arrangement, when displaying white (hereinafter, also referred to as "when displaying white" or "when displaying bright"), white may appear slightly yellowish. In order to alleviate this white with yellowish color problem, even the polarizing element manufactured by suppressing the yellowish color, the polarizing plate so far still has the problem of low degree of polarization or low contrast, and very low durability.

So far, it is difficult for the polarizing plates to present high-grade white (usually called paper white) while obtaining high polarization and high contrast. This is because when trying to make the polarizing plate high contrast, in the parallel position, the transmittance of the short wavelength side will decrease, so that the absorption will increase, and the polarizing plate will appear slightly yellow. In other words, even if the transmittance of the parallel position is constant in each wavelength of the visible light region, it is difficult to achieve high contrast even when the paper is white. By achieving 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 become paper white, the transmittance must be almost constant regardless of the wavelength in the parallel position, but if it is not at the same time high contrast, it will be used in a display device, and the display quality will be degraded. Therefore, it is expected that while the paper is white, it must also have high contrast.

When an iodine-based polarizing plate is used as an example, an iodine-based polarizing plate that uses polyvinyl alcohol (hereinafter, also referred to as "PVA") as a base material and uses iodine as a dichroic dye, generally has a 480nm And 600nm as the center of the absorption. It is said that the absorption at 480 nm is caused by the _{complex of polyiodine I 3} ^- and PVA, and the absorption at 600 nm is caused by the complex of polyiodine I ₅ ^- and PVA. In terms of the degree of polarization (dichroism) in 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 The degree of polarization (dichroism) of the object. In other words, when the transmittance of the vertical position is set to a certain value in each wavelength, the transmittance of the parallel position is higher at 600nm than at 480nm. When white is displayed, the white color will be dyed yellow. On the contrary, when the transmittance of the parallel position is set to a certain value, the transmittance of the vertical position at 600nm is lower than that at 480nm. When displaying black, the black is dyed blue and the contrast becomes very low. . Furthermore, an iodine-based polarizer with a constant transmittance in the parallel position is significantly lower in durability than a polarizer that emphasizes black when it is vertical. This system means that although iodine-based polarizers generally have low durability, the durability of polarizers with a certain parallel position transmittance is lower. When white is displayed, the white color is slightly yellowish, and since it generally has the impression of gradual deterioration, it cannot be said to be a good one. In addition, when black is displayed, when blue is revealed, since it is not obvious black, it gives the impression of high quality, the contrast will be reduced, and the durability will be significantly reduced. In addition, in the iodine-based polarizer, it is mainly near 550 nm where the visual sensitivity is high. Since there is no complex compound that absorbs at this wavelength, it is difficult to control the hue. In this way, since the degree of polarization (dichroism) of each wavelength is not constant, the wavelength dependence of the degree of polarization is generated. In addition, since only two dichroic pigments of 480 nm and 600 nm are absorbed by the complex of iodine and PVA, the iodine-based polarizer made of iodine and PVA cannot adjust the hue.

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 whose neutral coefficient is calculated and whose absolute value is 0 to 3. It is described in Patent Document 2 that the transmittance between 410nm and 750nm is set within ±30% of the average value. In addition to iodine, direct dyes, reactive dyes, or acid dyes are added and the coloring is adjusted.的polarizing film.

In addition, in response to the hue problem of iodine-based polarizers, dyed polarizers that are achromatic in the parallel position and the vertical position have also been developed (for example, Patent Document 3).

[Prior Technical Literature] [Patent Literature]

[Patent Document 1] JP 2002-169024 A

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

[Patent Document 3] WO 2014/162635

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

In addition, the polarizing film of Patent Document 2 is obtained when the a value and the b value in the UCS color space measured using only one polarizing film are set to an absolute value of 2 or less, not when the two polarizing films are overlapped. When displaying white and displaying black, the hue can be expressed as achromatic at the same time, and the contrast is also very low. In addition, the average value of the monomer transmittance of the polarizing film of Patent Document 2 is 31.95% in Example 1 and 31.41% in Example 2, which shows a low value. As such, the polarizing film of Patent Document 2 has a low transmittance, and therefore has insufficient performance in fields requiring high transmittance and high contrast, particularly in fields such as liquid crystal display devices and organic electroluminescence. In addition, the polarizing film of Patent Document 2 mainly uses iodine as a dichroic dye. Therefore, after a durability test, especially after a humid heat durability test (for example, an environment at 85°C and a relative humidity of 85%), the color Great changes and poor durability.

On the other hand, although the dye-based polarizing plate has excellent durability, it is the same as the iodine-based polarizing plate in terms of the wavelength dependence between the parallel position and the vertical position. There are almost no dichroic azo compounds exhibiting the same hue in the parallel position and the vertical position. Even if they exist, the contrast (or degree of polarization) is low. Depending on the type of dichroic azo compounds, there are many whites that appear yellow when displaying white, and blacks appear blue when displaying black, and the contrast decreases, etc., at the vertical and parallel wavelengths. Azo compounds with completely different dependencies. In addition, since the color sensitivity of humans also differs according to the brightness (transmittance) of light, even if the color correction of the dye-based polarizing plate is performed, the color correction for the brightness and darkness of the light is necessary. In the paper-white polarizer, in the parallel position, the transmittance is almost a certain value in each wavelength, and it cannot be achieved unless there is no wavelength dependence. Furthermore, in order to obtain a polarizing element with high transmittance and high contrast, in addition to satisfying a certain transmittance in the parallel position, the polarization degree (dichroic ratio) of each wavelength must be increased. Even if one type of azo compound is used in a polarizing element, its wavelength dependence must be considered, and the nitrogen compound must be further adjusted to precisely control the relationship between the transmittance and the dichroic ratio.

On the other hand, even if the transmittance of the parallel position can be precisely controlled and set to a certain level, high transmittance and high contrast cannot be achieved. In other words, the higher the transmittance, the more difficult it is to achieve high contrast, and it is impossible to achieve a paper-white polarizing plate with high transmittance and high contrast. It is very difficult to obtain a paper-white polarizer with high transmittance and high contrast. 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-grade 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, it is required to present a high-quality paper-like achromatic white color when displaying white, while displaying high contrast, a polarizing element with a single transmittance of 35% or more and a high degree of polarization. Although Patent Document 3 describes a polarizing plate that is achromatic even when displaying white and when displaying black, it is still desired to improve performance.

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

In order to solve the above-mentioned problems, the inventors of the present invention found after careful review that by compounding specific azo compounds, a high-performance polarizing element can be produced, which has a high transmittance and a paper white color when displaying white. High contrast. The inventor is the first in the world to discover that even with high transmittance, wavelength-independence in the visible light region can be achieved, and to develop a paper-like white (usually called paper white) that can achieve high quality Polarizing element with higher degree of polarization.

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

[Invention 1]

A polarizing element contains the azo compound represented by formula (1a) or (1b) or its salt, and the azo compound represented by formula (2) or its salt.

(式中，Ar₁表示至少具有1個取代基的苯基或是萘基，Rr₁至Rr₄是各別獨立地表示氫原子、低級烷基、低級烷氧基、或是具有磺酸基的低級烷氧基)

(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)

(式中，Av₁表示至少具有1個選自磺酸基及羧基之取代基之苯基或是萘基，Rv₁至Rv₆是各別獨立地表示氫原子、低級烷基、低級烷氧基、或是具有磺酸基的低級烷氧基，Xv₁表示可至少具有1個選自由低級烷基、低級烷氧基、磺酸基、胺基、低級烷基胺基、羥基、羧基、及羧基乙基 胺基所成群組之取代基的胺基、苯基胺基、苯基偶氮基、萘并三唑基或是苯甲醯基胺基)

(In the formula, Av ₁ represents a phenyl or 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, and a lower alkoxy group. 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 lower alkyl, lower alkoxy, sulfonic acid, amine, lower alkylamino, hydroxyl, carboxy, And carboxyethylamino group as a substituent of the amino group, phenylamino group, phenylazo group, naphthotriazole group or benzylamino group)

(式中，Ag₁表示具有取代基的苯基或是萘基，Bg及Cg是各別獨立地以式(BC-N)或是式(BC-P)表示，且至少一方是表示式(BC-N)，Xg₁是表示可以有取代基之胺基、可以有取代基之苯基胺基、可以有取代基之苯基偶氮基或是可以有取代基之苯甲醯基胺基)

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

(式中，Rg₁是表示氫原子、低級烷基、低級烷氧基、或是具有磺酸基之低級烷氧基，k是表示0至2的整數)

(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 represents an integer from 0 to 2)

(Rg₂及Rg₃是各別獨立地表示氫原子、低級烷基、低級烷氧基、或是具有磺酸基的低級烷氧基)

(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 as described in Invention 1 contains both of at least one compound represented by formula (1a) or its salt and at least one compound represented by formula (1b) or its salt.

[Invention 3]

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

[Invention 4]

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

(式中，Ag₁及Xg₁是如同式(2)中所定義，Rg₄及Rg₅是如同式(BC-N)中的針對Rg₁之定義，k₁及k₂是如同式(BC-N)中的針對k之定義)

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

[Invention 5]

The polarizing element described in any one of Inventions 1 to 4 further contains an azo compound represented by formula (3) or a salt thereof.

(式中，Ay₁是表示磺酸基、羧基、羥基、低級烷基、或是 低級烷氧基，Ry₁至Ry₄是各別獨立地表示氫原子、磺酸基、低級烷基、或是低級烷氧基，p表示1至3的整數)

(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, p represents an integer from 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 described in any one of Inventions 1 to 6, the absolute value of the a* value and b* value obtained when measuring the transmittance of natural light in accordance with JIS Z 8781-4:2013 In a single element, all are 5.0 or less, and in a state where the two polarizing elements are stacked so that their absorption axis directions are parallel to each other, they are all 2.0 or less.

[Invention 8]

The polarizing element according to any one of Inventions 1 to 7, wherein the two 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 in average transmittance to 590 nm is 2.5% or less, and the absolute value of the difference in 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-body transmittance of the polarizing element is 35% to 65%, and the absorption axis directions of the two polarizing elements are parallel to each other. The average transmittance from 520nm to 590nm is 25% to 45% in the state of overlapping configuration.

[Invention 10]

A polarizing plate is provided with a polarizing element as described in any one of Inventions 1 to 9 and a transparent protective layer provided on one or both sides of the aforementioned polarizing element.

[Invention 11]

A liquid crystal display device is provided with the polarizing element as described in any one of Inventions 1 to 9 or the polarizing plate as described in Invention 10.

The present invention can provide a high-performance polarizing element, a polarizing plate and a liquid crystal display device using the polarizing element, which display 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 formula (1a) or (1b) and an azo compound represented by formula (2). Both of the azo compound represented by the formula (1a) and the azo compound represented by the formula (1b) may be contained arbitrarily. Optionally, the azo compound represented by formula (3) may be further contained.

Preferably, the polarizing element contains these azo compounds or their salts, and a substrate on which the above-mentioned azo compounds or their salts are adsorbed.

The substrate is preferably a film obtained by forming a hydrophilic polymer into a film that can adsorb a dichroic dye, especially an azo compound, or the like. Although the hydrophilic polymer is not particularly limited, for example, polyvinyl alcohol-based resin, amylose-based resin, starch-based resin, cellulose-based resin, polyacrylate-based resin, and derivatives thereof, etc. . The hydrophilic polymer is preferably a polyvinyl alcohol-based resin and its derivatives from the viewpoints of the dyeability, processability, and crosslinkability of the dichroic dye. In the substrate, by adsorbing an azo compound or its salt, and applying alignment treatment such as extension, a polarizing element can be fabricated.

Next, the description of equation (1a).

In formula (1a), 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 sulfonyl group. Lower alkoxy of acid group. In addition, in the specification and scope of the patent application in this case, "low grade" means that the number of carbons is 1 to 4. For example, lower alkyl means an alkyl group having 1 to 4 carbon atoms.

In formula (1a), when Ar ₁ is a phenyl group, it is preferable to have at least one substituent selected from a sulfonic acid group, a carboxyl group, and an alkoxy group, and it is preferable to have a sulfonic acid group and a carboxyl group The one with at least one substituent is more preferable. When the phenyl group has two or more substituents, at least one of its substituents is a sulfonic acid group or a carboxyl group, and other substituents are preferably selected from sulfonic acid group, carboxyl group, lower alkyl group, lower alkoxy group , A group consisting of lower alkoxy, nitro, amino, acetamino and lower alkylamino substituted amino groups with sulfonic acid groups, more preferably selected from sulfonic acid groups, methyl groups, and ethyl groups , Methoxy, ethoxy, carboxyl, nitro and amino groups, particularly preferably selected from the group consisting of sulfonic acid, methyl, methoxy, ethoxy and carboxy. 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. Such a lower alkoxy group having a sulfonic acid group is more preferably 3-sulfopropoxy or 4-sulfobutoxy, and particularly preferably 3-sulfopropoxy.

In the case where the phenyl group has a sulfonic acid group as a substituent, the number of sulfonic acid groups is preferably one or two. In addition, although the substitution position of the sulfonic acid group is not particularly limited, the sulfonic acid group is one In the case of phenyl, it is better to be at the 4th position of the phenyl group. When there are two sulfonic acid groups, it is the combination of the 2nd and 4th positions of the phenyl group or the 3rd and the third position of the phenyl group. A combination of 5 digits is preferred.

In 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 sulfonic acid groups, hydroxyl groups, carboxyl groups, and lower alkoxy groups having sulfonic acid groups The group formed by the base. 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. Such a lower alkoxy group having a sulfonic acid group is more preferably 3-sulfopropoxy or 4-sulfobutoxy, and particularly preferably 3-sulfopropoxy.

In the case where the number of sulfonic acid groups substituted in the naphthyl group is 2, and the substitution position of the azo group is set to the second position, the substitution position of the sulfonic acid group is set at the fourth and eighth positions of the naphthyl group. The combination of positions or the combination of the 6th and 8th positions is preferable, and the combination of the 6th and the 8th positions is more preferable. When the number of sulfonic acid groups substituted 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.

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 preferred, and the substitution position of the sulfonic acid group is preferably at the end of the alkoxy group. Rr ₁ to Rr _{4 are} preferably each independently a hydrogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, a 3-sulfopropoxy group, or a 4-sulfobutoxy group , Particularly preferably a hydrogen atom, a methyl group, a methoxy group, or a 3-sulfopropoxy group.

The positions of Rr ₁ to Rr ₄ on the phenyl group are preferably: only in the second position of the phenyl group, only in the fifth position, in the combination of the second and sixth positions, and in the second and sixth positions. The combination of No. 5, and the combination of No. 3 and No. 5 are particularly preferred: only the No. 2 combination, No. 5 only, and the combination of No. 2 and No. 5. 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 Substituents other than atoms, the other side means a hydrogen atom. Rr ₃ and Rr _{4 have} the same meaning.

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

(式(1a’)中，Ar₁、及Rr₁至Rr₄，係如同式(1a)中所定義者)

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

Next, the description of equation (1b).

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 sulfonic acid group, carboxyl group, lower alkyl group, lower alkoxy group Group, a lower alkoxy group with a sulfonic acid group, a hydroxyl group, a nitro group, a benzyl group, an amino group, an acetamino group, and a lower alkylamino group substituted with the amino group, more preferably selected from the group Groups of sulfonic acid, methyl, ethyl, methoxy, ethoxy, hydroxyl, carboxy, nitro, amino, 3-sulfonic propoxy, and 4-sulfonic butoxy , Particularly preferably selected from the group consisting of sulfonic acid group, methyl group, methoxy group, carboxyl group, and 3-sulfonic acid group propoxy group. As the lower alkoxy group having a sulfonic acid group, the above-mentioned 3-sulfonic acid group propoxy group or 4-sulfonic acid group butoxy group is preferred, and a straight chain alkoxy group is preferred. The position of substitution is preferably at the end of the alkoxy group.

In the case where the phenyl group has a sulfonic acid group as a substituent, the number of sulfonic acid groups 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 this case, the 4th position of the phenyl group is preferred. In the case of two sulfonic acid groups, the combination of the 2nd and 4th positions of the phenyl group or the 3rd and 5th positions The combination is better. In the case where the phenyl group has a carboxyl group as a substituent, the number of carboxyl groups is preferably one or two. In addition, the substitution position of the carboxyl group is not particularly limited, but in the case of one carboxyl group, benzene is used. The 4th position of the phenyl group is preferred. When there are two carboxyl groups, the combination of the 2nd and 4th positions of the phenyl group or 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 the group consisting of sulfonic acid group, hydroxyl group, carboxyl group, and lower alkoxy group having sulfonic acid group Those who form a group are better. 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. Such a lower alkoxy group having a sulfonic acid group is more preferably 3-sulfopropoxy or 4-sulfobutoxy, and particularly preferably 3-sulfopropoxy.

In the case where the number of sulfonic acid groups substituted in the naphthyl group is 2, and the substitution position of the azo group is set to the second position, the substitution position of the sulfonic acid group is set at the fourth and eighth positions of the naphthyl group. The combination of the positions or the combination of the 6th and the 8th position is preferable, and the combination of the 6th and the 8th position is more preferable. When the number of sulfonic acid groups substituted 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. In the case where the number of sulfonic acid groups substituted in the naphthyl group is one, the substitution position of the sulfonic acid group can be listed as the substitution position of the naphthyl group such as the 3rd, 4th, 6th, and 8th positions. Good substitution position, but not limited to this.

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 preferred, or the substitution position of the sulfonic acid group is preferably at the end of the alkoxy group. Rv ₁ to Rv ₆ are each independently, preferably a hydrogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, a 3-sulfopropoxy group, or a 4-sulfobutoxy group, Particularly preferred is a hydrogen atom, a methyl group, a methoxy group, a carboxyl group or a 3-sulfopropoxy group. In addition, when Rv ₆ is a hydrogen atom or a methyl group, the polarization performance of the polarizing element or the polarizing plate is improved, which is preferable. Especially when Rv ₅ and Rv ₆ are hydrogen atoms and methyl groups, since the polarization performance of the polarizing element or the polarizing plate can be improved drastically, it is preferable.

Xv ₁ means 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 amino group, a lower alkylamino group, a hydroxyl group, a carboxyl group, and a carboxyethylamino group The amine group, phenylamino group, phenylazo group, naphthotriazole group or benzylamino group.

When Xv ₁ is an amino group that may have a substituent, the amino group is unsubstituted or preferably has one or two selected from lower alkyl, lower alkoxy, sulfonic acid, amino, and lower The substituent of the alkylamino group is more preferably one or two substituents selected from the group consisting of methyl, methoxy, sulfonic acid, amino, and lower alkylamino base. Here, the amine group which may have a substituent, except 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 phenylamino group is unsubstituted or preferably has one or two selected from lower alkyl, lower alkoxy, sulfonic acid, amine The substituents of the group formed by the amine group and the lower alkylamino group more preferably have one or two substituents selected from the group consisting of a methyl group, a methoxy group, a sulfonic acid group, and an amino 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 the group consisting of hydroxyl, lower alkyl, lower alkoxy, and amino groups The substituents of the group consisting of, and carboxyethylamino, more preferably have 1 to 3 substituents selected from the group consisting of methyl, methoxy, amino, and hydroxyl.

In the case where Xv ₁ is a naphthotriazole group which may have a substituent, the naphthotriazole group is unsubstituted or preferably has one or two selected from the group consisting of sulfonic acid group, amino group, and carboxyl group The substituent of the group preferably has one or two sulfonic acid groups as the substituent.

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

Xv _{1 is} preferably a benzylamino 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, when the phenylamino group has a substituent, one of the substituents is preferably at the p-position relative to the amino group, and the benzylamino group has a substituent In the case, one of the substituents is preferably at the p-position relative 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 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 defined as related in formula (1b).

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

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

The azo compound represented by this equation (1a) or (1b) may be used singly or in combination of two or more kinds. 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 represented by the formula (1a) or its salt can be synthesized by, for example, the method described in JP 2009-155364 A and the like and a method similar thereto, but it is not limited to these. For example, the azo compound represented by the formula (1a) can be produced by reacting the base compound represented by the formula (v) described later with a ureidolating agent such as phenyl chlorocarbonate at 20 to 95°C. Other methods for synthesizing by urea grouping are known methods of urea grouping an amine compound using a phosgene compound or the like. By this synthesis method, an azo compound represented by formula (1a) having a ureido skeleton can be obtained.

The specific synthesis method of the azo compound represented by formula (1a) is explained below. First, the amines with substituents represented by formula (i) are diazotized by the same method as described in Hosoda Toyosuke "Dye Chemistry", Gihodo, 1957, P.135-234. Then, it is coupled with the aniline represented by the formula (ii) to obtain the monoazoamine compound represented by the formula (iii).

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

(式中，R₁及R₂是分別表示與式(1a)中之Rr₁及Rr₂相同者)

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

(式中，Ar是表示與式(1a)的Ar₁相同者，R₁及R₂是分別表示與式(1a)中的Rr₁及Rr₂相同者)

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

Next, the monoazoamine compound represented by the formula (iii) is diazotized, and further, the aniline represented by the formula (iv) is coupled twice to obtain the bisazoamine represented by the formula (v) Amino compound.

(式中，R₃及R₄是分別表示與式(1a)中之Rr₃及Rr₄相同者)

(In the formula, R ₃ and R ₄ respectively represent the same as _{Rr 3} and Rr ₄ in formula (1a))

(式中，Ar是表示與式(1a)的Ar₁相同者，R₁及R₂是分別表示與式(1a)中的Rr₁及Rr₂相同者，R₃及R₄是分別表示與式(1a)中的Rr₃及Rr₄相同者)

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

The diazotization step in the above reaction pathway is carried out in accordance with the so-called cis method of mixing diazonium components in hydrochloric acid, sulfuric acid and other mineral acid aqueous solutions or suspensions with sodium nitrite and other nitrites, or in accordance with the After adding nitrite to the neutral or weakly alkaline aqueous solution of the diazonium component, it is carried out by the so-called reverse method in which it is mixed with mineral acid. The appropriate temperature for diazotization is -10 to 40°C. In addition, the coupling step with anilines is performed by mixing acidic aqueous solutions such as hydrochloric acid and acetic acid with the above-mentioned diazonium liquids under acidic conditions with a pH of 2 to 7 at a temperature of -10 to 40°C.

The mono-azoamine-based compound or bis-azoamine-based compound obtained by the coupling step can be taken out directly or by precipitation by acid precipitation or salting out and filtered, or by maintaining a solution or suspension for further A step of. When the diazonium salt is poorly soluble and a suspension, the suspension can also be filtered, and the filtered diazonium salt in the form of a filter cake is further used in the coupling step.

The bisazoamine-based compound obtained through the above-mentioned steps is then subjected to a ureido reaction with phenyl chlorocarbonate, thereby synthesizing the azo compound represented by formula (1a). This ureidolation reaction is carried out under neutral to alkaline conditions with a temperature of 10 to 90°C and a pH of 7 to 11 by the production method described in JP 2009-155364 A, for example. After the urea reaction is completed, the obtained azo compound is precipitated by salting out, and then filtered. In addition, when purification is necessary, it is only necessary to repeat salting out or use an organic solvent to precipitate the obtained azo compound from water. 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, the azo compound represented by 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 explained.

In formula (2), Ag ₁ represents a substituted phenyl group or a substituted naphthyl group. 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, and a sulfonic acid group. The lower alkoxy group, nitro group, amino group, acetamino group, or lower alkylamino group of the acid group is preferably substituted for the amino group. Other substituents are more preferably sulfonic acid, methyl, ethyl, methoxy, ethoxy, carboxy, nitro, or amine groups, particularly preferably sulfonic acid, methyl, methoxy, Ethoxy or carboxyl. As the lower alkoxy group having a sulfonic acid group, a straight-chain alkoxy group is preferred. The substitution position of the sulfonic acid group is preferably at the end of the alkoxy group, more preferably 3-sulfopropoxy and 4-sulfobutoxy, particularly preferably 3-sulfopropoxy. The number of substituents of the phenyl group is preferably one or two. Although the substitution position is not particularly limited, when the position of the azo group is set to the first position, it is only in the fourth position. , The combination of the 2nd and 4th positions, and the combination of the 3rd and 5th positions are preferred.

When Ag ₁ is a naphthyl group having a substituent, 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 its substituents is a sulfonic acid group, and the other substituents are sulfonic acid groups, hydroxyl groups, carboxyl groups, or lower alkoxy groups having sulfonic acid groups. good. It is particularly preferable that the naphthyl group has two or more sulfonic acid groups as a substituent. As the lower alkoxy group having a sulfonic acid group, a straight-chain alkoxy group is preferred. The substitution position of the sulfonic acid group is preferably at the end of the alkoxy group, more preferably 3-sulfopropoxy and 4-sulfobutoxy, but 3-sulfopropoxy is particularly preferred.

In the case where the number of sulfonic acid groups possessed by the naphthyl group is 2, the substitution position of the sulfonic acid group is preferably a combination of the 4th and 8th positions when the position of the azo group is set to the 2nd position. , And the combination at the 6th and 8th position is preferable, and the combination at the 6th and 8th position is even more preferable. When the number of sulfonic acid groups of 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). With Cg represented by the formula (BC-N), it is possible to obtain the effect of a polarizing element with high contrast while achieving a higher-quality paper white.

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 straight-chain alkoxy group is preferred, and the substitution position of the sulfonic acid group is preferably at the end of the alkoxy group, more preferably 3-sulfopropoxy and 4 -Sulfobutoxy, particularly preferably 3-sulfopropoxy.

The substitution position of Rg _{1 is preferably at the second or third position relative to the azo group substituted in Ag 1. In the} case where the azo group on the Ag ₁ side is set to the first position, It is better to be in the third place. In the case of having a sulfonic acid group, the substitution position of the sulfonic acid group is preferably the 6th position or the 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, a methyl group Group, methoxy, 3-sulfopropoxy, or 4-sulfopropoxy.

Xg ₁ represents an optionally substituted amino group, an optionally substituted phenylamino group, an optionally substituted phenylazo group, or an optionally substituted benzylamino group.

Xg _{1 is} preferably an optionally substituted amino group or an optionally substituted phenylamino group, and more preferably an optionally substituted phenylamino group. In the scope of patent application and specification of this case, "may have a substituent" means that it also includes the case where there is no substituent. For example, "the phenyl group which may have a substituent" includes a simple unsubstituted phenyl group and a substituted phenyl group. The amino 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 acid group, an amino group, and a lower alkylamino group The amino group of the group is more preferably an amino 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 amino groups that may have a substituent, an amino group having a ring structure such as a phenylamino group is excluded. The phenylamino group which may have a substituent, preferably has one or two selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfonic acid group, an amino group, and a lower alkylamino group The phenylamino group of the substituent in the group is more preferably benzene having one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfonic acid group, and an amino group Amino group. Although the substitution position is not particularly limited, it is particularly preferable that one of the substituents is at the p-position relative to the amino group of the phenylamino group.

The optionally substituted phenylazo group preferably has 1 to 3 selected from hydrogen atoms, hydroxyl groups, alkyl groups having 1 to 4 carbons, alkoxy groups having 1 to 4 carbons, amino groups, hydroxyl groups, And phenylazo as a substituent in the group formed by carboxyethylamino.

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

In particular, the performance will be improved. Therefore, the azo compound represented by formula (2) or its salt is preferably the azo compound represented by formula (2') or its salt.

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

In the polarizing element of the present invention, the content of the azo compound represented by the formula (2) or its salt is 0.01 to 100 parts by mass relative to the content of the azo compound of the formula (1a) or (1b) It is preferably 5000 parts by mass, and more preferably 0.1 to 3000 parts by mass.

The azo compound represented by the formula (2) or its salt can be described in, for example, Japanese Patent Application Publication No. 01-161202, Japanese Patent Application Publication No. 01-172907, Japanese Patent Application Publication No. 01-248105, Japanese Patent Application Publication No. 01 -265205 and JP 01-172907, but are not limited to these methods.

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 and so on.

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

The polarizing element contains the combination of the azo compound represented by formula (1a) or (1b) or its salt and the azo compound represented by formula (2) or its salt, even if it has a more polarized light than the conventional one. 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 polarization performance of the polarizing element of the present invention, it is preferable to contain the azo compound represented by formula (1a) or (1b) or its salt and the azo compound represented by formula (2) or its salt. In addition, it further contains at least one azo compound represented by the 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 carboxy group, or a lower alkoxy group, more preferably a sulfonic acid group Group, carboxyl group, methoxy group or ethoxy group, more preferably sulfonic acid group or 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 acid group, a methyl group, or a methoxy group.

p is an integer from 1 to 3.

The azo compound represented by formula (3) has an influence on the transmittance at 400 to 500 nm. Among the polarizing elements, the transmittance and polarization (dichroism) of the short wavelength side of 400 to 500 nm in particular have an effect on the blueness when displaying black or the yellowishness of white when displaying white. . The azo compound represented by the formula (3) will not reduce the transmittance of the short wavelength side of the parallel position of the polarizing element, and will improve the polarization characteristics (dichroism) in the 400 to 500 nm range, which can be further reduced The yellowish color when displaying white and the blue color when displaying black. The polarizing element of the present invention further contains the azo compound represented by formula (3), so that a polarizing element showing a more neutral hue and a higher degree of polarization can be obtained.

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

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

Hereinafter, specific examples of the azo compound represented by formula (3) are given.

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

In order to improve the polarization performance of the polarizing element of the present invention, it is preferable that in addition to the azo compound represented by formula (2) or its salt and the azo compound represented by formula (3) or its salt, it further contains the formula 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 contains an azo compound represented by formula (1a), an azo compound represented by formula (1b), an azo compound represented by formula (2), and an azo compound represented by formula (3) The combination of, even with high transmittance and high polarization, can still achieve a higher-quality paper white when displaying white, and a more advanced and clear black 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 free form, It can also be in the form of 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 and 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 of the azo compounds represented by the formula (1b) and optionally further contain the azo compound represented by the formula (3). The polarizing element of the present invention can have the desired chromaticity a* value and b* value, monomer transmittance, and average transmittance in a specific wavelength band as described later.

The blending ratio of the above-mentioned azo compound in the polarizing element is further suitably adjusted in the content of each of the above-mentioned azo compounds so that the transmittance and the chromaticity are within the preferable ranges described later. The performance of the polarizing element is not only due to the blending ratio of the azo compounds in the polarizing element, but also due to the swelling degree or extension ratio of the substrate that adsorbs the azo compound, the dyeing time, the dyeing temperature, the pH during dyeing, the influence of salt, etc. Various factors change. Therefore, the blending ratio of each azo compound can be determined in accordance with the degree of swelling of the substrate, the temperature, time, pH during dyeing, the type of salt, the concentration of the salt, and the stretching ratio. Such a determination of the blending ratio can be carried out by a person with ordinary knowledge in the field according to the following description without trial and error.

(Penetration rate)

The transmittance is the transmittance after the visual sensitivity correction obtained according to JIS Z 8722:2009. The transmittance can be measured by measuring the spectroscopic transmittance of the measurement sample (for example, a polarizing element or a polarizing plate) for each wavelength from 400 to 700nm, every 5nm or 10nm, and this with a 2 degree field of view ( C light source) calibration is obtained for visual sensitivity.

(I) The difference between the average transmittance of the 2 wavelength bands

In the polarizing element of the present invention, it is preferable that the difference in average transmittance between specific wavelength bands is below a predetermined value. The average transmittance is the average value of the transmittance in a specific wavelength band.

The wavelength bands are 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 600nm as the maximum value, y(λ) with 550nm as the maximum value, and 455nm When the respective maximum values of z(λ) as the maximum value are regarded as 100, the respective wavelength bands of 420 nm to 480 nm, 520 nm to 590 nm, and 600 nm to 640 nm that will become values of 20 or more are displayed.

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

In addition, regarding the transmittance (hereinafter, also referred to as "vertical position") measured when two polarizing elements are stacked so that the absorption axis direction becomes vertical (when displaying black or when displaying dark). 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, more preferably 1% or less. Such a polarizing element can display achromatic black in the vertical position. In addition, regarding the vertical transmittance, the absolute value of the difference between the average transmittance from 420 nm to 480 nm and the average transmittance from 520 nm to 590 nm is preferably 2% or less, and more preferably 1% or less. Regarding the vertical transmittance, the absolute value of the difference between the average transmittance from 520nm to 590nm and the average transmittance from 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 monomer transmittance, parallel transmittance, and vertical transmittance in each of the wavelength bands of 380nm to 420nm, 480nm to 520nm, and 640nm to 780nm, 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 are adjusted as described above. Although the pigment is not susceptible to large influences, it is better to adjust to some degree. The difference between the average transmittance of 380nm to 420nm and the average transmittance of 420nm to 480nm is preferably less than 15%, preferably: the average transmittance of 480nm to 520nm and the average transmittance of 420nm to 480nm The difference in rate is less than 15%, the difference between the average transmittance from 480nm to 520nm and the average transmittance from 520nm to 590nm is less than 15%, the average transmittance from 640nm to 780nm and the average transmittance from 600nm to 640nm The difference is 20% or less.

(II) monomer penetration rate

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

(III) Average transmittance in a specific wavelength band

The polarizing element should preferably have an average transmittance of 28% to 50% in the 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, high-brightness, and clear display device. The transmittance of the wavelength band from 520nm to 590nm is one of the main wavelength bands based on the color matching function used in the calculation when displaying colors in JIS Z 8781-4:2013. In particular, the wavelength bands from 520 nm to 590 nm are the 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 of the wavelength band from 520nm to 590nm. The average transmittance of the wavelength band from 520 nm to 590 nm measured in the parallel position is preferably 29% to 45%, more preferably 30% to 40%. In addition, the degree of polarization of the polarizing element at this time is preferably 80% to 100%, preferably 95% to 100%, and more preferably 99% to 100%. Although the degree of polarization is higher, the relationship between the degree of polarization and the transmittance can be adjusted to the appropriate transmittance and polarization due to the importance of brightness or the degree of polarization (or contrast). .

(Chromaticity a* value and b* value)

The chromaticity a* value and b* value are the values obtained when measuring the transmittance of natural light in accordance with JIS Z 8781-4:2013. JIS Z 8781-4: The method of expressing object color established by 2013 is equivalent to the method of expressing object color established by the International Commission on Illumination (abbreviated as CIE). The measurement of the 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 addition, in the following, the chromaticity a* value and b* value 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 method arrangement (when displaying white) are expressed as a*-p and b*-p, for the two measurement samples whose absorption axis directions are perpendicular to each other The chromaticity a* value and b* value obtained in the state of the mode arrangement (when displaying black) 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 can display high-grade white when the monomer is a neutral color and displays 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. In addition, for the polarizing element, each of the absolute values of a*-c and b*-c is preferably 20.0 or less, 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 value of the chromaticity a* value and b* value, even if there is only a difference of 0.5, humans can feel a chromatic aberration, and depending on the person, a large chromatic aberration can be felt. Therefore, in a polarizing element, it is very important to control these values. In particular, when the absolute values of a*-p, b*-p, a*-c, and b*-c are each less than 1.0, it is almost impossible to confirm the presence of white when displaying white and black when displaying black. Other colors can get a good polarizer. In the parallel position, it can achieve achromaticity, that is, high-grade paper-like white, and in the vertical position, it can achieve achromatic, high-quality, clear black.

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

In addition, the polarizing element of the present invention has the advantage of less heat generation even if it is irradiated with sunlight or other light because it absorbs less light at a wavelength of 700 nm or more than the commonly used iodine-based polarizer or Patent Document 3. For example, in the case of using a liquid crystal display outdoors, etc., sunlight irradiates the liquid crystal display, and as a result, it also irradiates the polarizing element. Sunlight also has wavelengths above 700nm and contains near-infrared rays that have a heat-generating effect. For example, a polarizing element using an azo compound as described in Example 3 of Japanese Patent Publication No. 02-061988, absorbs near-infrared light with a wavelength around 700 nm, and therefore generates some heat. However, the polarizing element of the present invention, Since the absorption of near-infrared rays is very small, there is little heat generation even when exposed to sunlight outside the house. The polarizing element of the present invention is superior in terms of less heat generation and less deterioration.

Hereinafter, a case where a substrate made of polyvinyl alcohol-based resin is made by adsorbing an azo compound is taken as an example, and a specific method of making a polarizing element will be described. Moreover, the manufacturing method of the polarizing element of this 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 one synthesized by a known method may be used. The polyvinyl alcohol-based resin can be obtained, for example, by saponifying a polyvinyl acetate-based resin. As the polyvinyl acetate-based resin, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate, copolymers of vinyl acetate and other monomers copolymerizable with vinyl acetate can also be exemplified. Examples of other monomers to be copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The degree of saponification of the polyvinyl alcohol resin is usually about 85 to 100 mol%, and more preferably 95 mol% or more. The polyvinyl alcohol-based resin may be further modified. For example, polyvinyl methyl acetal or polyvinyl acetal modified with aldehydes may be used. In addition, the degree of polymerization of polyvinyl alcohol-based resin means the average degree of polymerization of the viscosity, and can be obtained by a method known in the technical field. Usually, the degree of polymerization 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-based resin into a film is not particularly limited, and a known method can be used to form a film. In this case, the polyvinyl alcohol-based resin film may contain glycerin, ethylene glycol, propylene glycol, low molecular weight polyethylene glycol, etc. as a plasticizer. The amount of the plasticizer is preferably 5 to 20% by mass, more preferably 8 to 15% by mass in the total amount of the film. Although the film thickness of the raw material film is not particularly limited, it is, for example, about 5 μm to 150 μm, preferably about 10 μm to 100 μm.

(Swelling step)

The raw film obtained as described above is subjected to 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 from 1.00 to 1.50 times, and more preferably from 1.10 to 1.35 times. In the case of shortening the time for manufacturing the polarizing element, since the raw material film will swell during the dyeing process described later, the swelling process may be omitted.

(Dyeing step)

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

As the azo compound, the azo compound represented by formula (1a) or (1b) or its salt and the azo compound represented by formula (2) or a mixture of its salt are used, and can be further used arbitrarily The formula (3) is either the azo compound represented by the formula (4) or its salt. In addition, it is also possible to use the examples of "Functional Pigment Application" (CMC (Stock) publication, 1st edition, supervised by Masahiro Irie, pages 98 to 100) without compromising the performance of the polarizing element in this case. The dichroic dye of the azo compound adjusts the color. In addition to using these azo compounds in the form of free acids, salts of the compounds can also be used. 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, preferably a sodium salt.

The dyeing step is not particularly limited as long as it is a method of adsorbing and impregnating the dye in the resin film. For example, it is preferably performed by immersing the resin film in a dyeing solution, or it may be performed by coating the resin film with the dyeing solution. To proceed. Each azo compound in the dyeing solution can be adjusted in the range of 0.001 to 10% by mass, for example.

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 appropriately, it is better to adjust it to 30 seconds to 20 minutes, and more preferably 1 to 10 minutes.

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

(Washing step 1)

After the dyeing step, a washing step (hereinafter, also referred to as "washing step 1") can be performed before proceeding to the next step. 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 cleaning step 1, the migration of the dye into the liquid for subsequent treatment can be inhibited. In the washing step 1, water is generally used as the washing liquid. Although the washing method is preferably immersed in a washing liquid, it can also be washed by applying a washing liquid to the 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 cleaning step 1 must be a temperature at which the material constituting the resin film (for example, a hydrophilic polymer, here is a polyvinyl alcohol resin) does not dissolve. The cleaning treatment is generally carried out at 5 to 40°C. However, since there will be no performance problems even if there is no washing step 1, the washing step can be omitted.

(Steps to include cross-linking agent and/or 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. The method of making the resin film contain a crosslinking agent and/or a water-resistant agent is preferably immersed in the treatment solution, but the treatment solution may be applied or coated on the resin film. The treatment solution contains at least one cross-linking agent and/or a water-resistant agent, and a solvent. The temperature of the treatment solution in this step is preferably 5 to 70°C, more preferably 5 to 50°C. The processing time in this step is preferably 30 seconds to 6 minutes, 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 polyisocyanate can be used. Titanium-based compounds, titanium oxysulfate, etc., but other than this, ethylene glycol glycidyl alcohol, polyamide epichlorohydrin, etc. may also be used. Examples of water-resistant agents include peroxysuccinic acid, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerol diglycidyl ether, ammonium chloride or It is magnesium chloride, etc., but boric acid is preferably used. As the solvent used for the crosslinking agent and/or the water resistance agent, although water is preferred, it is not limited. The content of the crosslinking agent and/or water resistance agent can be appropriately determined by those skilled in the art according to the type. However, when boric acid is used as an example, the concentration is 0.1 to 6.0% by mass in the treatment solution. Preferably, it is more preferably 1.0 to 4.0% by mass. However, it is not necessary to contain a cross-linking agent and/or a water-resistant agent, and when it is desired to shorten the time, if the cross-linking treatment or the water-resistant treatment is not necessary, this treatment step can be omitted.

(Extension step)

After performing the dyeing step, the washing step 1, or the step of containing a cross-linking agent and/or a water-resistant agent, the extending step is performed. The stretching step is performed by uniaxially stretching the resin film. The extension method may use either a wet extension method or a dry extension method. The extension 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 better to stretch the resin film at the temperature of the air medium at room temperature to 180°C. In addition, the humidity is preferably set in an environment of 20 to 95% RH. As the heating method, for example, an inter-roller zone stretching method, a roller heating stretching method, a pressure stretching method, an infrared heating stretching method, etc. may be mentioned, but the stretching method is not limited. Although the stretching step may be one-stage stretching, it may also be performed by two-stage or more multi-stage stretching.

In the case of the wet stretching method, it is preferable to stretch the resin film in water, a water-soluble organic solvent, or a mixed solution thereof. It is preferable to perform the stretching treatment while immersing in a solution containing at least one kind of crosslinking agent and/or water resistance agent. As the cross-linking agent and the water-resistant agent, the same as those described above regarding the step of containing the cross-linking agent and/or the water-resistant agent can be used. The concentration of the crosslinking agent and/or water resistance agent in the solution in the extension step is preferably 0.5 to 15% by mass, and more preferably 2.0 to 8.0% by mass. The extension temperature is preferably processed at 40 to 70°C, 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 by one-stage stretching, it can also be performed by two-stage or more multi-stage stretching.

(Washing step 2)

After the stretching step, since the crosslinking agent and/or water-resistant agent or impurities adhere to the surface of the resin film, a cleaning step for cleaning the surface of the resin film (hereinafter, also referred to as "cleaning step") 2"). The washing time is preferably 1 second to 5 minutes. The cleaning method is preferably to immerse the resin film in a cleaning solution, but it can also be cleaned by coating the solution or coating on the resin film. As a cleanser, water is better. One-stage washing treatment can be used, or two-stage or more multi-stage treatment can be used. The solution temperature in the washing step is not particularly limited, but is usually 5 to 50°C, preferably 10 to 40°C.

As the treatment liquid or its solvent used in the treatment steps so far, in addition to water, for example, dimethyl sulfoxide, N-methylpyrrolidone, methanol, ethanol, propanol, isopropyl Alcohol, glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol or trimethylolpropane and other alcohols, ethylenediamine and diethylenetriamine and other amines, but not Limited to this. The treatment liquid or its solvent is preferably water. In addition, these treatment liquids or their solvents may be used singly or as a mixture of two or more types.

(Drying step)

After the stretching step or the washing step 2, a drying step of the resin film is performed. Although the drying treatment can be carried out by natural drying, in order to further improve the drying efficiency, it can be carried out by the compression of the drum or the removal of water from the surface caused by an air knife, or a suction drum, etc., and/ Or it can be dried by blowing air. The drying treatment temperature is preferably 20 to 100°C for drying treatment, and more preferably 60 to 100°C for drying treatment. 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 and pH of the dyeing solution, sodium chloride or sodium sulfate (also known as Glauber's salt) , The type of salt such as sodium tripolyphosphate or its concentration, and the dyeing time, and the stretching magnification in the re-extending step are to make the polarizing element meet at least one of the following conditions (i) to (v) Adjust as appropriate, and adjust as more appropriate in a way that further satisfies the conditions of (vi) and (vii).

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

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

(iii) The monomer penetration rate becomes 35% to 65%.

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

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

(vi) Regarding the parallel bit penetration rate, the average penetration rate from 520nm to 590nm becomes 25 to 45%.

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

By the above method, a polarizing element containing at least a combination of the azo compound represented by the formula (1a) or (1b) and the azo compound represented by the formula (2) can be manufactured. Although such a polarizing element has a higher transmittance and higher degree of polarization than the conventional polarizing element, it can express a high-quality paper-like appearance when two polarizing elements are stacked so that the absorption axis directions become parallel. It is white, and has a neutral color (neutral gray) hue in a single body, and can produce high-contrast polarizing elements. In addition, the polarizing element has high durability against high temperature and high humidity.

<Polarizer>

The polarizing plate of the present invention is provided with 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. It is preferably a plastic with excellent transparency, mechanical strength, thermal stability, and moisture shielding properties. It is also possible to provide the same function by forming the same layer. As an example of the plastic constituting the protective film, there can be cited: polyester resin, acetate resin, polyether turpentine resin, polycarbonate resin, polyamide resin, polyimide resin, Thermoplastic resins such as polyolefin resins and acrylic resins; films obtained from thermosetting resins such as acrylic, urethane, urethane, epoxy, and silicone, or ultraviolet curable resins, etc. Among them, as the polyolefin resin, there can be mentioned: amorphous polyolefin resin, which has a polymerized unit of a cyclic polyolefin such as a norbornene-based monomer or a polycyclic norbornene-based monomer. Resin. Generally, it is better to select a protective film that does not hinder the performance of the polarizing element after the protective film is laminated. As such a protective film, triacetyl cellulose ( TAC) and norbornene are particularly preferred. In addition, the protective film can be subjected to hard coating treatment, anti-reflection treatment, anti-sticking, diffusion, anti-glare treatment, etc., without impairing the effect of the present invention.

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

Depending on the situation, the polarizing plate can be installed on the surface of a protective layer or film that will become a non-exposed surface afterwards to improve the view Angle and/or various functional layers that improve contrast, layers or films with brightness enhancement properties. Various functional layers, for example, phase difference control layer or film. Polarizing plates, such films or display devices, are preferably attached by pressure-sensitive adhesive.

The polarizing plate may be provided with various known functional layers such as an anti-reflection layer, an anti-glare layer, and a hard coat layer on the exposed surface of the protective layer or the film. In the production of the layer with various functions, although the coating method is preferred, the film with this function can also be laminated through an adhesive or an adhesive.

Although the polarizing plate of the present invention has high transmittance and high degree of polarization, it can achieve achromaticity, especially when it displays white, it can express high-grade paper-like white, and it can express 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, etc. according to needs, and can be applied to liquid crystal projectors, electronic computers, clocks, notebook computers, and word processing Cameras, LCD TVs, polarized lenses, polarized glasses, car navigators, and measuring devices or displays inside and outside the house, etc. In particular, the polarizing element or polarizing plate of the present invention is suitable for use in liquid crystal display devices, such as reflective liquid crystal display devices, semi-transmissive 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 paper-like white and high contrast. In addition, the liquid crystal display device has 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]

The polyvinyl alcohol film (VF-PS manufactured by Kuraray Co., Ltd.) with a saponification degree of 99% or more and an average degree of polymerization of 2400 was immersed in warm water at 45°C for 2 minutes, and then the elongation ratio was set to 1.30 times by swelling treatment. Containing 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, compound example [1a-25] as a compound of formula (1a) 0.32 parts by mass, compound example [2-4] 0.20 parts by mass The swollen film is immersed in a 45°C dyeing solution for 4 minutes and 30 seconds so that the film contains 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 film after the immersion was stretched to 5.0 times and subjected to a stretching treatment for 5 minutes in a 50°C aqueous solution containing 30.0 g/l of boric acid. The obtained film was continuously maintained in this tight state, and was washed by immersing it 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, polyvinyl alcohol (NH-26 manufactured by VAM & POVAL Co., Ltd., Japan) was dissolved in water at 4% as an adhesive, and an alkali-treated triacetyl cellulose film (manufactured by Fujifilm Co., Ltd.) was used. ZRD-60) is laminated to obtain a polarizing plate. The obtained polarizing plate maintains the optical properties of the above-mentioned polarizing element, especially the monomer transmittance, hue, degree of polarization, and the like. This polarizing plate was used as the measurement sample of Example 1.

[Example 2]

Except for using 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, the compound example [1a-25] as a compound of formula (1a) is 0.32 parts by mass, as described in formula (2) The CI direct blue 69 of the compound was 0.22 parts by mass instead of the dyeing solution used in Example 1, and the rest was the same as in Example 1 to produce a polarizing plate.

[Example 3]

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

[Example 4]

Except that the time for containing the azo compound was changed from 4 minutes and 30 seconds to 3 minutes, the rest was the same as in Example 3 to produce a polarizing plate.

[Example 5]

Except that the time for containing the azo compound was changed from 4 minutes and 30 seconds to 2 minutes, the rest was the same as in Example 3 to produce a polarizing plate.

[Example 6]

Except for using 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, the compound example [1a-25] as a compound of formula (1a) is 0.32 parts by mass, as described in formula (2) The compound example [2-4] of the compound is 0.20 parts by mass, and the compound example [3-2] is the compound of formula (3) (n=1 is 24%, n=2 is 71%, n=3 is 5%) It was 0.24 parts by mass instead of the dyeing liquid used in Example 1, and the rest was the same as in Example 1 to produce a polarizing plate.

[Example 7]

Except that the time for containing the azo compound was changed from 4 minutes and 30 seconds to 3 minutes, the rest was the same as in Example 6, and a polarizing plate was produced.

[Example 8]

Except that the time for containing the azo compound was changed from 4 minutes and 30 seconds to 2 minutes, the rest was the same as in Example 6, and a polarizing plate was produced.

[Example 9]

Except that the time for containing the azo compound was changed from 4 minutes and 30 seconds to 1 minute, the rest was the same as in Example 6 to produce a polarizing film.

[Example 10]

Except for using 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, and the compound example [1a-25] as the compound of formula (1a) is 0.32 parts by mass, as described in formula (2) The CI Direct Blue 69 of the compound is 0.22 parts by mass, and the compound example [3-1] which is a compound of formula (3) is 0.27 parts by mass instead of the dyeing solution used in Example 1, and the rest is 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, 1.5 parts by mass of anhydrous sodium sulfate, and the compound example [1a-25] as the compound of formula (1a) is 0.32 parts by mass, as described in formula (2) The CI direct blue 69 of the compound is 0.22 parts by mass, and the compound example of the compound of formula (3) [3-2] (n=1 is 24%, n=2 is 71%, n=3 is 5%) is 0.20 mass To replace the dyeing solution used in Example 1. The rest is the same as in Example 1, and a polarizing plate is produced.

[Example 12]

Except for using 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, and 0.32 parts by mass of the compound example [1a-25] as the compound of formula (1a), as described in formula (2) The compound example [2-4] of the compound is 0.20 parts by mass and the CI Direct Yellow 28 is 0.22 parts by mass instead of the dyeing solution used in Example 1, and the rest is 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, 1.5 parts by mass of anhydrous sodium sulfate, the compound example [1a-13] as a compound of formula (1a) is 0.35 parts by mass, as described in formula (2) The compound example [2-4] of the compound is 0.20 parts by mass, and the compound example [3-1] of the compound of formula (3) is 0.27 parts by mass. 1 The same operation is performed to produce a polarizing film.

[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, the compound example [1a-5] as a compound of formula (1a) is 0.29 parts by mass, as described in formula (2) The compound example [2-4] of the compound is 0.20 parts by mass, and the compound example [3-1] of the compound of formula (3) is 0.27 parts by mass. 1 The same operation is performed to produce a polarizing film.

[Example 15]

Except using 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, and 0.32 parts by mass as the compound of formula (1a) in compound example [1a-25], as the compound described in formula (2) The compound example [2-13] is 0.21 parts by mass, and the compound example [3-1] as the compound of formula (3) is 0.27 parts by mass instead of the dyeing solution used in Example 1, and the rest are the same as those in Example 1. The same operation is used to produce a polarizing film.

[Example 16]

Except for using 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, and the compound example [1a-25] as the compound of formula (1a) is 0.32 parts by mass, as described in formula (2) The compound example [2-15] of the compound is 0.243 parts by mass, and the compound example [3-1] of the compound of formula (3) is 0.27 parts by mass. 1 The same operation is performed to produce a polarizing film.

[Example 17]

Except for using 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, and the compound example [1a-25] as the compound of formula (1a) is 0.32 parts by mass, as described in formula (2) The compound example [2-23] of the compound is 0.218 parts by mass, and the compound example [3-1] of the compound of formula (3) is 0.27 parts by mass. 1 The same operation is performed to produce a polarizing film.

[Example 18]

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, the compound example [1b-33] as the compound of formula (1b) is 0.15 parts by mass, and the compound example of the compound of formula (2) [2-4] is 0.10 parts by mass, and the compound example [3-1] as the compound of formula (3) is 0.05 parts by mass instead of the dyeing solution used in Example 1, and the containing time of the azo compound is changed from 4 minutes to 30 Except for changing the second to 8 minutes 00 seconds, the rest was the same as in Example 1, and a polarizing film was produced.

[Example 19]

Except that the time for the swollen film to contain the azo compound in the dyeing step was changed from 8 minutes to 4 minutes, the rest was the same as in Example 18 to produce a polarizing film.

[Example 20]

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, the compound example [1b-33] as the compound of formula (1b) is 0.15 parts by mass, and the compound example of the compound of formula (2) [2-4] is 0.10 parts by mass, and the compound example [3-2] as the compound of formula (3) (n=1 is 24%, n=2 is 71%, n=3 is 5%) is 0.05 parts by mass Except for replacing the dyeing solution used in Example 19, the rest is the same as in Example 18 to produce a polarizing film.

[Example 21]

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, the compound example [1b-33] as the compound of formula (1b) is 0.15 parts by mass, and the compound example of the compound of formula (2) Except that [2-4] is 0.10 parts by mass and CI Direct Yellow 28 is 0.05 parts by mass instead of the dyeing solution used in Example 19, the rest is the same as in Example 18 to produce a polarizing film.

[Example 22]

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, the compound example [1b-56] as the compound of formula (1b) is 0.25 parts by mass, and the compound example of the compound of formula (2) [2-4] is 0.10 parts by mass, and 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 Except for replacing the dyeing solution used in Example 19, the rest is the same as in Example 18 to produce a polarizing film.

[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, the compound example [1b-35] as the compound of formula (1b) is 0.22 parts by mass, and the compound example of the compound of formula (2) [2-4] is 0.10 parts by mass, and 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 Except for replacing the dyeing solution used in Example 19, the rest is the same as in Example 18 to produce a polarizing film.

[Example 24]

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, the compound example [1b-35] as the compound of formula (1b) is 0.22 parts by mass, and the compound example of the compound of formula (2) [2-17] is 0.10 parts by mass, and the compound example [3-1] which is a compound of formula (3) is 0.05 parts by mass instead of the dyeing solution used in Example 19. The rest is the same as in Example 18. And make a polarizing film.

[Example 25]

Except for using 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 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, as in formula (1b) The compound example [1b-33] of the compound described in) is 0.15 parts by mass, and the compound example [2-17] which is the compound described in formula (2) is 0.1 parts by mass, and the compound example is the compound of formula (3) [3-1] A polarizing film was produced in the same manner as in Example 1 except that it was 0.05 parts by mass instead of the dyeing solution used in Example 1.

[Example 26]

Except that the time for containing the azo compound was changed from 4 minutes and 30 seconds to 3 minutes, the rest was performed in the same manner as in Example 25 to produce a polarizing film.

[Example 27]

Except for using 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 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, as in formula (1b) The compound example [1b-44] of the compound described in) is 0.17 parts by mass, and the compound example [2-4] is 0.17 parts by mass, which is the compound of formula (3). [3-1] A polarizing film was produced in the same manner as in Example 1 except that 0.05 parts by mass was used in place of the dyeing solution used in Example 1.

[Example 28]

Except for using 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 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, as in formula (1b) The compound example [1b-56] of the compound described in) is 0.23 parts by mass, and the compound example [2-4] is 0.17 parts by mass, which is the compound of formula (3). [3-1] A polarizing film was produced in the same manner as in Example 1 except that 0.05 parts by mass was used in place of the dyeing solution used in Example 1.

[Example 29]

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

[Comparative Examples 1 to 5]

Except that the aqueous solution containing the azo compound (dyeing solution) in Example 1 is set to the same composition as that in Example 1 of Patent Document 3, and the time of containing the azo compound (the immersion time of the swollen PVA film against the dyeing tank ) Change 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 is 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 Co., Ltd. having a neutral gray color was obtained as a measurement sample.

[Comparative Example 7]

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

[Comparative Examples 8 to 13]

According to the preparation method of Comparative Example 1 in JP 2008-065222, the time for containing iodine is set to 5 minutes and 30 seconds in Comparative Example 8 and 4 minutes and 45 seconds in Comparative Example 9. 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 The polarizing plate is used as the measurement sample.

[Comparative Example 14]

An iodine-based polarizing plate SKW-18245P manufactured by Polatechno Co., Ltd., which showed a paper white color in the parallel position, was obtained and used as a measurement sample.

[Comparative Example 15]

The polarizing plate was produced as described in Example 1 of JP 11-218611 A on the dye-based polarizing plate.

[Comparative Example 16]

The polarizing plate was produced as described in Example 3 of JP 2001-033627 A on the dye-based polarizing plate.

[Comparative Example 17]

The polarizing plate was produced as described in Example 1 of JP 2004-251962 on the dye-based polarizing plate.

[Comparative Example 18]

In addition to the use of 0.29 parts by mass of CI Direct Blue 6 of the same color and dichroic azo compound with a dianisidine skeleton to replace 0.1 parts by mass of the compound example [2-17], and in the vertical position Except for the design in which the transmittance is almost constant and the color becomes black, the rest is the same as in Example 25 to produce a polarizing film.

[evaluate]

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

(a) Monomer penetration rate Ts, parallel position penetration rate Tp, and vertical position penetration rate Tc

The monomer transmittance Ts, parallel transmittance Tp, and 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 of each wavelength at the time of measurement with one measurement sample. Parallel transmittance Tp is the spectral transmittance of each wavelength measured by superimposing two measurement samples so that the absorption axis directions become parallel. The vertical transmittance Tc is the spectral transmittance measured by superimposing two polarizing plates so that the absorption axis becomes vertical. The measurement is performed across the wavelength of 400 to 700 nm.

Calculate the average value of the parallel bit transmittance Tp from 420 to 480 nm, the average value from 520 to 590 nm, and the average value from 600 to 640 nm, which are shown in Tables 1 and 2.

(b) Monomer penetration rate Ys, parallel position penetration rate Yp, and vertical position penetration rate Yc

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

(c) Polarization ρy

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

ρy={(Yp-Yc)/(Yp+Yc)} ^1/2 ×100

(d) Chromaticity a* value and b* value

For each measurement sample, in accordance with JIS Z 8781-4:2013, the chromaticity a* value and b* value in each of when the monomer transmittance Ts is measured and when the parallel position transmittance Tp is measured. In the measurement, the above-mentioned spectrophotometer is used, and the transmission color and the reflection color are both incident from the outdoor side and measured. The light source is 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 when the monomer transmittance Ts and the parallel transmittance Tp are measured, respectively *Value and b*value.

(e) The absolute value of the difference between the average transmittance of the two wavelength bands

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

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

On the other hand, the measurement samples of Comparative Examples 1 to 5, when compared with the examples showing the same monomer transmittance (Ys), have low polarization (ρy) and show the same parallel transmittance. When compared with the examples of (Yp), Yc is higher, so it can be seen that the polarization function is lower than that of the examples. For example, when comparing the polarization degree (ρy) of Example 3 with the same Ys and Comparative Example 1, it is 99.95% relative to Example 3, and that of Comparative Example 1 is 98.15%, and Example 3 is compared with Comparative Example 1. The degree of polarization is 1.8% higher. In addition, the contrast (Yp/Yc) with respect to Example 3 is 1985, Comparative Example 1 is 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 degree of polarization (ρy) of Example 25 and Comparative Example 3 showing the same Ys, the degree of polarization (ρy) of Example 25 is 99.61%, and that of Comparative Example 3 is about 95.57%. The degree of polarization of Example 25 is comparable to that of Comparative Example 3. Compared with Example 3, it is 4.04% higher. In addition, the contrast (Yp/Yc) with respect to Example 25 is 256, and Comparative Example 3 is about 22. Example 25 has a high contrast 11 times or more than that of Comparative Example 3.

In addition, when comparing the parallel transmission (Yp) of Example 2 with the same degree of polarization (ρy) and Comparative Example 2, it is 37.68%, and Comparative Example 2 is 33.70%, 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.

In addition, when comparing Example 20 with the same degree of polarization (ρy) with Comparative Example 1, Yp relative to Example 20 is 38.25%, and Comparative Example 1 is 32.72%. In the same degree of polarization, Example 20 is compared with Comparative Example 1. Compared with Example 1, Yp is 5.53% higher, which shows 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 of the two wavelength bands of the parallel position transmittance Tp shown in Table 4 showed high values.

The above shows that the polarizing plates of Examples 1 to 29, while maintaining high monomer transmittance and parallel transmittance, can still present a high-quality paper-like white in the parallel position, and, The monomer has a neutral color (neutral gray) hue. In addition, it can be seen that the polarizing plates of Examples 1 to 29 not only maintain high transmittance and exhibit achromaticity in parallel positions, but also have high polarization.

(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, the measurement samples of Examples 1 to 29 showed no change in transmittance and hue. In contrast, the degree of polarization of Comparative Examples 8 to 14 is reduced by more than 10%, and b*-c is lower than -10, and the color as the appearance becomes blue, especially when the two measurement samples are arranged in a vertical position. , Black will appear blue seriously. Especially in Comparative Example 14, a significant increase in the transmittance and a decrease in the degree of polarization are seen. 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 with high reliability, long-term high contrast, and high color reproducibility.

Claims (11)

A polarizing element containing the azo compound represented by formula (1a) or (1b) or its salt, and the azo compound represented by formula (2) or its salt,

In the formula, Ar ₁ represents a phenyl group or a naphthyl group with 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 The lower alkoxy group,

In the formula, Av ₁ represents a phenyl or 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, and a lower alkyl group. Oxy 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 lower alkyl, lower alkoxy, sulfonic acid, amino, lower alkylamino, hydroxyl, Amino group, phenylamino group, phenylazo group, naphthotriazole group, or benzylamino group as a substituent in the group formed by carboxyl and carboxyethylamino group,

In the formula, Ag ₁ represents a substituted phenyl or naphthyl group, Bg and Cg are each independently represented by formula (BC-N) or formula (BC-P), at least one of which is represented by formula (BC -N), Xg ₁ means an amino group which may have a substituent selected from the group consisting of a methyl group, a methoxy group, a sulfonic acid group, and an amino group, a phenylamino group which may have a substituent, and may have The substituted phenylazo group or the benzylamino 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 represents an integer from 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 described in item 1 of the scope of patent application contains at least one compound represented by formula (1a) or its salt and at least one compound represented by formula (1b) or its salt. For the polarizing element described in item 1 or 2 of the scope of patent application, Cg is represented by the formula (BC-N). For the polarizing element described in item 1 or 2 of the scope of patent application, 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 as defined in formula (BC-N) for Rg ₁ , and k ₁ and k ₂ are as defined in formula (BC-N ) For the definition of k. For example, the polarizing element described in item 1 or item 2 of the scope of patent application further contains the azo compound represented by formula (3) or its salt,

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 claim 1 or 2, wherein the polarizing element contains a polyvinyl alcohol-based resin film as a base material. For the polarizing element described in item 1 or 2 of the scope of patent application, the absolute value of the a* value and b* value obtained in the measurement of the transmittance of natural light according to JIS Z 8781-4:2013 is described in the foregoing In the single polarizing element, all are below 5.0, In a state where the two polarizing elements are stacked so that their absorption axis directions are parallel to each other, they are both 2.0 or less. The polarizing element described in the first or the second of the scope of patent application, wherein the two aforementioned polarizing elements are superimposed so that the absorption axis directions become parallel to each other and measured to obtain an average transmittance of 420nm to 480nm and The absolute value of the difference in average transmittance from 520 nm 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. For the polarizing element described in item 1 or 2 of the scope of patent application, wherein the monomer transmittance of the polarizing element is 35% to 65%, and the absorption axis directions of the two polarizing elements are parallel to each other. The average transmittance of 520nm to 590nm obtained by the overlapping arrangement state is 25% to 45%. A polarizing plate is provided with the polarizing element described in any one of items 1 to 9 in the scope of patent application, and a transparent protective layer provided on one or both sides of the aforementioned polarizing element. A liquid crystal display device is provided with the polarizing element described in any one of the first to 9th patent applications or the polarizing plate described in the 10th patent application.