TWI698500B - Achromatic polarization element, achromatic polarization plate using same and liquid crystal display device - Google Patents

Abstract

An object of the present invention is to provide an achromatic polarization element, achromatic polarization plate using same and liquid crystal display device. The achromatic polarization element has high transmissive and high polarization, and is achromatic in both at the time of white display and black display, especially has a high performance exhibiting a high-quality white at the time of white display.

The present invention provides a polarization element which contains: an azo compound or a salt thereof represented by the formula (1), an azo compound or a salt thereof represented by the formula (2), and an azo compound or a salt thereof represented by the formula (3).

Description

Colorless polarizing element, and colorless polarizing plate and liquid crystal display device using the polarizing element

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

The polarizing element is generally manufactured by adsorbing and aligning the iodine of the dichroic dye or the dichroic dye on the polyvinyl alcohol-based resin film. The polarizing plate obtained by bonding a protective film composed of triacetyl cellulose etc. to the polarizing element through the adhesive layer can be used in liquid crystal display devices and the like. Polarizers that use iodine as a dichroic pigment are called iodine-based polarizers. On the other hand, polarizers that use dichroic dyes such as dichroic azo compounds are called dyes. Department of polarizing plate. Among these, the dye-based polarizing plate has high heat resistance, high humidity and heat durability and high stability, and also has the characteristics of high color selectivity obtained by the blending of pigments. On the other hand, it has the same polarization Compared with high-degree iodine-based polarizers, there is a problem of low transmittance and contrast. Therefore, in addition to maintaining high durability and diversified color options, it is desirable to have higher transmittance and high bias. Polarizing element with light characteristics.

In addition, even if it is a dye-based polarizer with diversified color options, the polarizing elements still have a positional relationship in which the absorption axis directions of the two polarizing elements are parallel to each other (hereinafter, also referred to as "parallel position") When the method overlaps and displays white (hereinafter, also referred to as "white display"), there will be a problem that the white appears slightly yellowish white. In order to improve the white and yellowish problem, even if the polarizing element is made to suppress the yellowishness, the polarizing plate so far uses two polarizing elements to make the absorption axis directions orthogonal to each other (hereinafter, also referred to as "positive When displaying black (hereinafter, also referred to as "during black display"), the black appears blue when it is overlapped and arranged in the way of "intersection"). Therefore, a polarizing plate that shows colorless white when displaying white and colorless black when displaying black is sought. Especially, when displaying white, it is difficult to obtain a high-quality white polarizer commonly known as paper white. In order to make the polarizing plate colorless, in the parallel position or the orthogonal position, the transmittance must not vary with the wavelength, but basically a constant value, but such a polarizing plate has not yet been obtained. The reason why the hue of white display is different from that of black display is that the wavelength dependence of the transmittance in the parallel position and the orthogonal position is different, especially the transmittance of the visible light region is not constant. Furthermore, the fact that dichroism is not constant in the visible light region is also one of the reasons why it is difficult to realize the colorless polarizer.

Taking an iodine-based polarizer as an example, an iodine-based polarizer that uses polyvinyl alcohol (hereinafter, also referred to as "PVA") as a base material and iodine as a dichroic dye generally has 480nm and 600nm as the center The absorption. The absorption at 480 nm is believed to be due to the complex of polyiodine I ₃ ^- and PVA, and the absorption at 600 nm is due to the complex of polyiodine I ₅ ^- and PVA. The degree of polarization (dichroism) in each wavelength is based on the degree of polarization (dichroism) of the complex of polyiodide I ₅ ^- and PVA compared to the degree of polarization of the complex of polyiodide I ₃ ^- and PVA (two Color) is still high. That is, if it is desired to make the transmittance of the orthogonal position constant in each wavelength, and the transmittance of the parallel position is 600nm higher than 480nm, the phenomenon of white and yellowish white will occur during white display. On the contrary, if the transmittance of the parallel position is to be constant, the transmittance of the orthogonal position is lower than 480nm for the 600nm, so the black will be bluish when displaying black. When the white is displayed in white, when the white is yellow, it will bring the impression of general deterioration, so it is hard to say that it is better. In addition, when the black is displayed in blue, it is not a clear black, and it gives an impression of non-premium. In addition, in the iodine-based polarizer, the visibility is mainly around 550 nm, and since there is no complex compound based on this wavelength, the hue is difficult to control. 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 there are only two dichroic pigments at 480 nm and 600 nm that are absorbed by the complex of iodine and PVA, the iodine-based polarizer composed of iodine and PVA cannot adjust the hue.

The method of improving the hue of the iodine-based polarizing plate is described in Patent Document 1 or Patent Document 2. Patent Document 1 describes a polarizing plate whose intermediate coefficient is calculated and whose absolute value is 0 to 3. Patent Document 2 describes a polarizing film in which the transmittance between 410 nm and 750 nm is within ±30% of the average value, and a direct dye, reactive dye, or acid dye is added in addition to iodine to adjust the coloring.

In addition, colorless dyed polarizing plates have also been developed (for example, Patent Document 3).

[Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 4281261

[Patent Document 2] Japanese Patent No. 3357803

[Patent Document 3] WO2014/162635

However, the polarizing plate of Patent Document 1 shows from the examples that even if the intermediate coefficient (Np) is low, the a* value of the parallel position obtained from JIS Z 8729 is -2 to -1, and the b* value It is 2.5 to 4.0, so it appears yellow-green when displayed in white. In addition, the hue a* value of the orthogonal position is 0 to 1, but 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 by using only one polarizing film to measure the a value and b value in the UCS color space of the absolute value 2 or less, and the white display when the two polarizing films are overlapped and In the two hues when black is displayed, not the one that can appear colorless at the same time. Furthermore, 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 low transmittance, so it is not in the field of seeking high transmittance and high contrast, especially in the fields of liquid crystal display devices and organic electroluminescence. Polarizing plates with high transmittance and specific monomer transmittance of more than 40% have not been available so far. In particular, the higher the transmittance, the more difficult it is to obtain a colorless polarizer. Therefore, the pursuit of high transmittance and whiteness Both the white in the color display and the black in the black display are colorless polarizers. Then, the main dichroic pigment of the polarizing film of Patent Document 2 uses iodine, so after the durability test, especially after the damp heat durability test (e.g., 85°C, 85% relative humidity environment), the color changes greatly. Poor durability.

On the other hand, the dye-based polarizer is excellent in durability, but the wavelength dependence is the same as that of the iodine-based polarizer when the wavelength dependence is different in the parallel position and the orthogonal position. Azo compounds exhibiting dichroism that exhibit the same hue at the parallel position and the orthogonal position hardly exist, and even if they exist, the dichroism (polarization characteristic) is low. According to the type of dichroic azo compounds, white is yellow when displayed in white, and black is blue when displayed in black. Azo compounds with completely different wavelength dependences at the orthogonal and parallel positions are also used. exist. In addition, according to the light and shade of light, the sensibility of human color is different, it is assumed that even if the color correction of the dye-based polarizer is performed, it must be suitable for covering the parallel position from the orthogonal position to control the difference between the light and darkness generated by the polarization. Color correction. The colorless polarizer is in the parallel position and the orthogonal position, and the transmittance is almost constant at each wavelength, and if it is in a state without wavelength dependence, it cannot be achieved. Moreover, in order to obtain a polarizing element with high transmittance and high contrast, a certain transmittance must be satisfied at the parallel position and orthogonal position at the same time. Moreover, the polarization degree (dichromatic ratio) of each wavelength must be high, and For certain. When one type of azo compound is applied to a polarizing element, although the wavelength dependence of the transmittance is different in the orthogonal position and the parallel position, in order to mix two or more azo compounds to achieve a certain transmittance, the system Considering the penetration rate of the parallel position and the penetration rate of the orthogonal position one by one, it is necessary to precisely control the relationship between the two-color ratio of more than two kinds.

On the other hand, even if the penetration rate of the parallel position and the penetration rate of the orthogonal position, and the relationship between the two-color ratio are precisely controlled, so that the penetration rate reaches a certain level in each, it is still impossible to achieve high penetration rate, And high contrast. That is, it is impossible to achieve a colorless polarizer with a high degree of polarization, or a colorless polarizer with a high transmittance. From this point, it is very difficult to obtain a colorless polarizer system with high transmittance and/or high contrast, and it is not possible to achieve it if only the dichroic pigments of the three primary colors of the color are used. In particular, it is extremely difficult to achieve a certain transmittance and high dichroism in parallel positions at the same time. Even if the white color is slightly mixed, it cannot express high-quality white. In addition, the white color in the bright state has high brightness and high sensitivity, so it is particularly important. Therefore, for the polarizing element, when looking for a white display, it displays colorless white like high-quality paper, and when it displays black, it displays colorless black. At the same time, it has a monomer transmittance of more than 35% and a high degree of polarization. element. Even though Patent Document 3 describes a colorless polarizer during white display and black display, it is desired to further improve performance.

Therefore, the object of the present invention is to provide a colorless polarizing element, and a colorless polarizing plate and a liquid crystal display device using the polarizing element. The colorless polarizing element has high transmittance and high degree of polarization, while displaying white and black The two of them are colorless during display, and especially for white display, it is high performance that presents high-quality white.

In order to solve the above-mentioned problems, the inventors of the present invention have conducted intensive research and found that through the preparation of specific azo compounds, it is possible to produce a kind of dichroism that has no wavelength dependence in the parallel position and the orthogonal position. for Colorless polarizing element with higher degree of polarization than prior art. The inventors of the present invention first discovered that the wavelength-independence in the visible light region can be achieved even with a high transmittance, and developed a white that can achieve the quality of high-quality paper, commonly known as paper white. ) Polarizing element with higher degree of polarization. That is, the present invention relates to the following [1] to [12].

式中，Ar₁表示具有取代基之苯基或萘基，Rr₁及Rr₂分別獨立地表示氫原子、低級烷基、低級烷氧基、或具有磺基之低級烷氧基，Xr₁表示可具有取代基之胺基、可具有取代基之苯基胺基、可具有取代基之苯基偶氮基、可具有取代基之苯甲醯基、或可具有取代基之苯甲醯基胺基；

式中，Ab₁表示具有取代基之苯基或萘基，Rb₁至Rb₆分別獨立地表示氫原子、低級烷基、低級烷氧基、或具有磺基之低級烷氧基，Xb₁表示可具有取代基之胺基、可具有取代基之苯基胺基、可具有取代基之苯基偶氮基、可具有取代基之萘並三唑基、可具有取代基之苯甲醯基、或可具有 取代基之苯甲醯基胺基；

式中、Ag₁及Ag₂分別獨立地表示至少具有1個選自由磺基、低級烷基、低級烷氧基、具有磺基之低級烷氧基、羧基、硝基、胺基、及取代胺基所構成之群的取代基之萘基或苯基，Rg₁及Rg₂分別獨立地表示氫原子、低級烷基、低級烷氧基、或具有磺基之低級烷氧基。 [1] A polarizing element comprising: an azo compound represented by formula (1) or a salt thereof, an azo compound represented by formula (2) or a salt thereof, and an azo compound represented by formula (3) or Its salt,

In the formula, Ar ₁ represents a substituted phenyl or naphthyl group, Rr ₁ and Rr ₂ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group, and Xr ₁ represents Amino group that may have a substituent, a phenylamino group that may have a substituent, a phenylazo group that may have a substituent, a benzylamine that may have a substituent, or a benzylamine that may have a substituent base;

In the formula, Ab ₁ represents a substituted phenyl or naphthyl group, Rb ₁ to Rb ₆ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group, and Xb ₁ represents Amino groups that may have substituents, phenylamino groups that may have substituents, phenylazo groups that may have substituents, naphthotriazole groups that may have substituents, benzyl groups that may have substituents, Or a benzylamino group which may have a substituent;

In the formula, Ag ₁ and Ag ₂ each independently represent at least one selected from the group consisting of sulfo group, lower alkyl group, lower alkoxy group, lower alkoxy group with sulfo group, carboxyl group, nitro group, amine group, and substituted amine In the naphthyl group or the phenyl group of the substituent of the group consisting of a group, Rg ₁ and Rg ₂ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group.

[2] The polarizing element as described in [1], which is related to the transmittance obtained when the two polarizing elements are arranged so that the absorption axis directions become parallel to each other. The average of 420nm to 480nm The absolute value of the difference between the transmittance and the average transmittance from 520nm to 590nm is 2.5% or less, and the absolute value of the difference between the average transmittance from 520nm to 590nm and the average transmittance from 600nm to 640nm is 2.0% or less.

[3] The polarizing element as described in [1] or [2], wherein the absolute value of the a* value and the b* value obtained when measuring the transmittance of natural light in accordance with JIS Z 8781-4:2013 is: the aforementioned The single polarizing element is 1 or less, and the two polarizing elements are arranged so that the absorption axis directions of the two polarizing elements are overlapped and arranged so that they are all 2 or less.

[4] The polarizing element according to any one of [1] to [3], wherein the single-cell transmittance of the polarizing element is 35% to 60%, and the two polarizing elements are adjusted to the absorption axis Directions become parallel to each other The average transmittance from 520nm to 590nm is 25% to 55% when the method is overlapped and arranged.

式中，Ab₁、Rb₁至Rb₄、及Xb₁表示與式(2)之者相同者。 [5] The polarizing element according to any one of [1] to [4], wherein the azo compound represented by the aforementioned formula (2) is an azo compound represented by the formula (4),

In the formula, Ab ₁ , Rb ₁ to Rb ₄ , and Xb ₁ represent the same as those of the formula (2).

式中，Ab₁、Rb₂、Rb₄、及Xb₁表示與式(2)之者相同者。 [6] The polarizing element according to any one of [1] to [5], wherein the azo compound represented by the aforementioned formula (2) is an azo compound represented by the formula (5),

In the formula, Ab ₁ , Rb ₂ , Rb ₄ , and Xb ₁ represent the same as those of the formula (2).

[7] The polarizing element according to any one of [1] to [6], which further contains the azo compound represented by formula (6) or a salt thereof.

式中，Ry₁及Ry₂分別獨立地表示磺基、羧基、羥基、低級烷基、或低級烷氧基，n表示1至3之整數。

In the formula, Ry ₁ and Ry ₂ each independently represent a sulfo group, a carboxyl group, a hydroxyl group, a lower alkyl group, or a lower alkoxy group, and n represents an integer of 1 to 3.

[8] The polarizing element according to any one of [1] to [7], wherein the use of The transmittance of the aforementioned two polarizing elements is obtained by superimposing the absorption axis directions orthogonal to each other. The absolute difference between the average transmittance of 420nm to 480nm and the average transmittance of 520nm to 590nm The value is 0.6% or less, and the absolute value of the difference between the average transmittance from 520nm to 590nm and the average transmittance from 600nm to 640nm is 0.6% or less.

[9] The polarizing element according to any one of [1] to [8], wherein the two polarizing elements are arranged in a state in which the absorption axis directions of the two polarizing elements are overlapped so that the directions of their absorption axes are orthogonal to each other, according to JIS Z 8781-4: 2013 The absolute value of a* value and b* value obtained when measuring the transmittance of natural light is 2 or less.

[10] The polarizing element according to any one of [1] to [9], wherein the polarizing element contains a polyvinyl alcohol-based resin film as a base material.

[11] A polarizing plate comprising the polarizing element described in any one of [1] to [10], and a transparent protective layer provided on one or both sides of the polarizing element.

[12] A liquid crystal display device comprising the polarizing element described in any one of [1] to [10] or the polarizing plate described in [11].

The present invention provides a colorless polarizing element, and a colorless polarizing plate and a liquid crystal display device using the polarizing element. The colorless polarizing element has high transmittance and high degree of polarization, and can display both white and black at the same time The medium is colorless, especially when it is displayed in white, it is high performance that presents high-quality white.

<Polarizing element>

The polarizing element of the present invention contains the azo compound represented by formula (1) or its salt, the azo compound represented by formula (2) or its salt, and the azo compound represented by formula (3) or its salt. The polarizing element of the present invention may optionally further contain the azo compound represented by formula (6). Preferably, the polarizing element includes a substrate on which these azo compounds or their salts and the above-mentioned azo compounds or their salts are adsorbed.

A preferable substrate is a film obtained by forming a hydrophilic polymer capable of adsorbing dichroic dyes, especially azo compounds. The hydrophilic polymer system is not particularly limited, and may be, for example, polyvinyl alcohol-based resin, amylose-based resin, starch-based resin, cellulose-based resin, and polyacrylate-based resin. From the viewpoints of the dyeability, processability, and crosslinkability of the dichroic dye, the best hydrophilic polymer is polyvinyl alcohol resin and its derivatives. In order to make the hydrophilic polymer into a film shape, a polarizing element can be produced by containing an azo compound or its salt and subjecting it to alignment treatment such as stretching.

Describe the azo compound represented by formula (1).

In the formula (1), Ar ₁ represents a substituted phenyl group or a substituted naphthyl group.

When Ar ₁ is a phenyl group, it is preferable to have at least one sulfo group or carboxyl group as its substituent. When the phenyl group has two or more substituents, at least one of its substituents is a sulfo group or a carboxyl group. The other substituents are preferably a sulfo group, a carboxyl group, a lower alkyl group, a lower alkoxy group, and a sulfo group. The lower alkoxy group, nitro group, benzyl group, amino group, acetylamino group and lower alkylamino group substituted amino group, more preferably sulfo group, methyl group, ethyl group, methoxy group, Ethoxy group, carboxyl group, nitro group, benzyl group and amino group, particularly preferred ones are sulfo group, methyl group, methoxy group, ethoxy group, benzyl group and carboxyl group. The lower alkoxy group with a sulfo group is preferably a straight-chain alkoxy group, and the substitution position of the sulfo group is preferably at the end of the alkoxy group, more preferably 3-sulfopropoxy and 4-sulfobutoxy Group, but particularly preferred is 3-sulfopropoxy. The number of sulfo groups possessed by the phenyl group is preferably 1 or 2, and the substitution position is not particularly limited, but a combination of only the 4-position, the 2-position and the 4-position, and the 3-position and the 5-position is preferable.

When Ar ₁ is a substituted naphthyl group, it is preferable to have at least one sulfo group as its substituent. When it has two or more substituents, at least one of its substituents is a sulfo group, and the others are substituted The preferable group is a sulfo group, a hydroxyl group, a carboxyl group, and a lower alkoxy group having a sulfo group. The lower alkoxy group with a sulfo group is preferably a straight-chain alkoxy group, and the substitution position of the sulfo group is preferably at the end of the alkoxy group, more preferably 3-sulfopropoxy and 4-sulfobutoxy Group, and particularly preferred is 3-sulfopropoxy. When the number of substituents of the sulfo group is 2, the positions of the sulfo group possessed by the naphthyl group are preferably a combination of positions 4, 8 and 6, 8, and a combination of positions 6, 8 is more preferable. When the number of sulfo groups possessed by the naphthyl group is 3, the substitution position of the sulfo group is the combination of the 1, 3, and 6 positions.

In the specification of the present case, the "lower" of lower alkyl, lower alkoxy, and lower alkylamino refers to those having 1 to 4 carbon atoms, preferably 1 to 3. Moreover, in the description of this case, for the sake of convenience, "substituents" are Contains hydrogen atoms.

Rr ₁ and Rr ₂ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group. Rr ₁ and Rr ₂ are each independently, preferably a hydrogen atom, a lower alkyl group, or a lower alkoxy group, and more preferably a hydrogen atom, a methyl group, or a methoxy group. The lower alkoxy group with a sulfo group is preferably a straight-chain alkoxy group, and the substitution position of the sulfo group is preferably at the end of the alkoxy group, more preferably 3-sulfopropoxy and 4-sulfobutoxy The most preferred one is 3-sulfopropoxy.

Xr ₁ represents an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a benzyl group which may have a substituent, or a benzyl which may have a substituent Amino group. The preferred amino group that may have a substituent has one or two selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, an amino group, and a lower alkylamino group The amino group of the substituent, more preferably has 1 or 2 selected from the group consisting of hydrogen atom, methyl, ethyl, methoxy, ethoxy, amino, and lower alkylamino One of the substituents is the amino group. The preferred phenylamino group which may have a substituent has one or two selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, an amino group, and a lower alkylamino group The phenylamino group of the substituent is more preferably a phenylamine having one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, and an amino group base. The preferred benzyl group which may have a substituent has a benzyl group selected from the group consisting of a hydrogen atom, a hydroxyl group, a sulfo group, an amino group, and a carboxyethylamino group. The preferred benzylamino group which may have a substituent has one benzylamino group selected from the group consisting of a hydrogen atom, a hydroxyl group, an amino group, and a carboxyethylamino group. The preferred phenylazo group that may have a substituent is one having a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 4 carbons, an alkoxy group having 1 to 4 carbons, an amino group, and a carboxyethylamino group 1 to 3 phenylazo groups in the group. Preferably Xr ₁ is a benzylamino group which may have a substituent, and a phenylamino group which may have a substituent, and a more preferable one is a phenylamino group. The position of the substituent is not particularly limited, but when there is one substituent, the p-position is particularly preferred.

The method of obtaining the azo compound represented by the formula (1) includes, for example, the methods described in Japanese Patent Application Publication No. 2003-215338, Japanese Patent Application Publication No. 9-302250, and Japanese Patent Application No. 3881175, but not Limited to this.

Specific examples of the azo compound represented by formula (1) include, for example, CI Direct Red 81, CI Direct Red 117, CI Direct Violet 9 and CI Direct Red 127, as well as Japanese Patent Application Publication No. 2003-215338 and Japanese Patent Application Publication Azo compound described in 9-302250 gazette and patent 3881175 gazette. Further specific examples of the azo compound represented by formula (1) are shown below in the form of free acid.

[Compound Example 2]

[Compound Example 7]

Next, the azo compound represented by formula (2) will be explained.

In formula (2), Ab ₁ represents a substituted phenyl group or naphthyl group. When Ar ₁ is a phenyl group, it is preferable to have at least one sulfo group or carboxyl group as its substituent. When the phenyl group has two or more substituents, at least one of its substituents is a sulfo group or a carboxyl group. The other substituents are preferably a sulfo group, a carboxyl group, a lower alkyl group, a lower alkoxy group, and a sulfo group. The lower alkoxy group, nitro group, benzyl group, amino group, acetylamino group or lower alkylamino group substituted amino group, more preferably sulfo group, methyl group, ethyl group, methoxy group, Ethoxy group, carboxyl group, nitro group, and amino group, particularly preferably sulfo group, methyl group, methoxy group, benzyl group and carboxyl group. The lower alkoxy group with a sulfo group is preferably a straight-chain alkoxy group, and the substitution position of the sulfo group is preferably at the end of the alkoxy group, more preferably 3-sulfopropoxy and 4-sulfobutoxy The most preferred is 3-sulfopropoxy. The number of sulfo groups possessed by the phenyl group is preferably 1 or 2, and the substitution position is not particularly limited, but only 4 positions, a combination of 2 and 4 positions, and a combination of 3 and 5 positions are preferred.

When Ab ₁ is a substituted naphthyl group, preferably it has at least one sulfo group as its substituent. When the naphthyl group has two or more substituents, at least one of the substituents is a sulfo group. Preferred other substituents are sulfo group, hydroxyl group, carboxyl group, and lower alkoxy group having sulfo group. The lower alkoxy group with a sulfo group is preferably a straight-chain alkoxy group, and the substitution position of the sulfo group is preferably at the end of the alkoxy group, more preferably 3-sulfopropoxy and 4-sulfobutoxy The most preferred is 3-sulfopropoxy. When the number of substituents of the sulfo group is 2, the substitution position of the sulfo group in the naphthyl group is preferably the combination of the 4th and 8th positions, the combination of the 6th and 8th positions, and the combination of the 6th and 8th positions is more preferable. When the number of substituents of the sulfo group is 3, the substitution position of the sulfo group in the naphthyl group is preferably a combination of 1, 3, and 6 positions.

Rb ₁ to Rb ₆ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group. Rb ₁ to Rb ₆ are each independently, preferably a hydrogen atom, a methyl group, or a methoxy group. The lower alkoxy group having a sulfo group is preferably a straight-chain alkoxy group. The substitution position of the sulfo group is The alkoxy terminal is preferred, 3-sulfopropoxy and 4-sulfobutoxy are more preferred, and 3-sulfopropoxy is particularly preferred.

Xb ₁ represents an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a naphthotriazole group which may have a substituent, and a benzyl which may have a substituent An acyl group or a benzylamino group which may have a substituent. Preferably Xb ₁ is a benzylamino group which may have a substituent or a phenylamino group which may have a substituent, and a more preferable one is a phenylamino group. The preferred amino group which may have a substituent has any one or two selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, an amino group, and a lower alkylamino group The amino group of each of the substituents preferably has any one or two selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, an amino group, and a lower alkylamino group The amino group of the substituent. The preferred phenylamino group which may have a substituent has one or more selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, an amino group, and a lower alkylamino group The phenylamino group having two substituents, more preferably benzene having one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, and an amino group Amino group. The preferred phenylazo group which may have a substituent is one having a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 4 carbons, an alkoxy group having 1 to 4 carbons, an amino group, and a carboxyethylamine A phenylazo group of 1 to 3 substituents in the group formed by the group. A preferred naphthotriazole group that may have a substituent is a naphthotriazole group having one or two substituents selected from the group consisting of a hydrogen atom, a sulfo group, an amino group, and a carboxyl group. The preferred benzyl group which may have a substituent is a benzyl group having one substituent selected from the group consisting of a hydrogen atom, a hydroxyl group, a sulfo group, and an amino group. The preferred benzylamino group which may have a substituent is a benzylamino group having one substituent selected from the group consisting of a hydrogen atom, a hydroxyl group, an amino group, and a carboxyethylamino group . The position of substitution is not particularly limited, but when there is one substituent, the para position is preferred.

The azo compound represented by formula (2) is preferably the azo compound represented by formula (4) because it can improve the polarization performance of the polarizing element.

In the formula (4), Ab ₁ , Rb ₁ to Rb ₄ , and Xb ₁ represent the same as those described in the related formula (2).

The azo compound represented by the formula (2) is the azo compound represented by the formula (5) because it can further improve the polarization performance of the polarizing element, so it is better.

In the formula (5), Ab ₁ , Rb ₂ , Rb ₄ , and Xb ₁ represent the same as those described in the related formula (2).

The method for obtaining the azo compound represented by the formula (2) may include the methods described in WO2012/108169 and WO2012/108173, but is not limited to these methods.

Specific examples of the azo compound represented by the formula (2) include the azo compounds described in WO2012/108169 and WO2012/108173. Further specific examples of the azo compound represented by formula (2) are shown below in the form of free acid.

[Compound Example 15]

[Compound Example 21]

[Compound Example 32]

[Compound Example 43]

Next, the azo compound represented by formula (3) will be explained.

In formula (3), Ag ₁ and Ag ₂ are each independently, having at least one selected from the group consisting of sulfo group, lower alkyl group, lower alkoxy group, lower alkoxy group having sulfo group, carboxyl group, nitro group, amine group , And the naphthyl group or phenyl group of the substituent in the group consisting of substituted amino groups.

When Ag ₁ and/or Ag ₂ are phenyl groups, it is preferable to have at least one sulfo group or carboxyl group as its substituent. When the phenyl group has two or more substituents, at least one of the substituents is a sulfo group or a carboxyl group. The other substituents are preferably sulfo group, carboxyl group, lower alkyl group, lower alkoxy group, and sulfo group The lower alkoxy group, nitro group, amino group, acetylamino group or lower alkylamino group is substituted for the amino group. The other substituents are preferably sulfo, methyl, ethyl, methoxy, ethyl An oxy group, a carboxy group, a nitro group, or an amino group, particularly preferably a sulfo group, a methyl group, a methoxy group, an ethoxy group, or a carboxy group. The lower alkoxy group with a sulfo group is preferably a straight-chain alkoxy group, and the substitution position of the sulfo group is preferably at the end of the alkoxy group, more preferably 3-sulfopropoxy and 4-sulfobutoxy The most preferred is 3-sulfopropoxy. The number of substituents of the phenyl group is preferably 1 or 2, and the substitution position is not particularly limited, but only the 4-position, the combination of the 2-position and the 4-position, and the combination of the 3-position and the 5-position are preferable.

When Ag ₁ and/or Ag ₂ is a substituted naphthyl group, it is preferable to have at least one sulfo group as its substituent. When the naphthyl group has two or more substituents, at least one of the substituents One is a sulfo group, and the other substituents are preferably a sulfo group, a hydroxyl group, a carboxyl group, or a lower alkoxy group with a sulfo group. The naphthyl group is particularly preferably one having two or more sulfo groups as a substituent. The lower alkoxy group with a sulfo group is preferably a straight-chain alkoxy group, and the substitution position of the sulfo group is preferably at the end of the alkoxy group, more preferably 3-sulfopropoxy and 4-sulfobutoxy Group, but particularly preferred is 3-sulfopropoxy. When the number of sulfo groups possessed by the naphthyl group is 2, the preferred substitution position of the sulfo group is the combination of positions 4 and 8 and the combination of positions 6 and 8, more preferably the combination of positions 6 and 8. When the number of sulfo groups in the naphthyl group is 3, the substitution position of the sulfo group is preferably a combination of 1, 3, and 6 positions.

Rg ₁ and Rg ₂ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group. Preferably, Rg ₁ and Rg ₂ are each independently a hydrogen atom, a lower alkyl group, or a lower alkoxy group, and more preferably are a hydrogen atom, a methyl group, or a methoxy group. Particularly preferred is that at least one of Rg ₁ and Rg ₂ is a methoxy group. The lower alkoxy group with a sulfo group is preferably a straight-chain alkoxy group, and the substitution position of the sulfo group is preferably at the end of the alkoxy group, more preferably 3-sulfopropoxy and 4-sulfobutoxy The most preferred is 3-sulfopropoxy.

The azo compound represented by the formula (3) or its salt can be synthesized by a method described in, for example, WO2012/165223.

Specific examples of the azo compound represented by formula (3) are shown below in the form of free acid.

The polarizing element contains the combination of the azo compound represented by the formula (1) to the formula (3), which has a higher transmittance and higher degree of polarization than the conventional colorless polarizer, but it can achieve a white display as High-quality paper-like white, commonly known as paper white, can realize colorless black when displaying in black, especially clear black with high quality.

In order to improve the performance of the polarizing element, in addition to the azo compound represented by the formula (1) to the formula (3), it is preferable to further contain the azo compound represented by the formula (6).

In the formula, Ry ₁ and Ry ₂ are each independently a sulfo group, a carboxy group, a hydroxyl group, a lower alkyl group, or a lower alkoxy group, preferably a sulfo group or a carboxy group. n represents an integer from 1 to 3. At least one of Ry ₁ and Ry ₂ is preferably a sulfo group or a carboxyl group.

The azo compound represented by formula (6) has an effect on the transmittance from 400 to 500 nm. In polarizing elements, in particular, the transmittance and polarization (dichroism) on the short wavelength side of 400 to 500 nm affect the blue coloration during black display or the yellowing of white color during white display. The azo compound represented by formula (6) does not reduce the transmittance of the short wavelength side of the parallel position of the polarizing element, and can improve the polarization characteristics (dichroism) of 400 to 500 nm, and reduce the yellowness of white display The blue color appears when it is converted and displayed in black. The polarizing element further contains the azo compound represented by formula (6), and the monomer transmittance is in the range of 35% to 60%, showing a more neutral hue. It is now a higher-quality paper-like white color, which can increase the degree of polarization.

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

Specific examples of the azo compound represented by formula (6) are, for example, CI Direct Yellow 4, CI Direct Yellow 12, CI Direct Yellow 72, and CI Direct Orange 39, and those with a stilbene structure described in WO2007/138980. Azo compounds, etc., but are not limited to these.

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

(n表示1或2之整數。)

(n represents an integer of 1 or 2.)

[Compound Example 53]

The azo compounds represented by formula (1) to formula (6) may be in free form or in salt form. The salt may be, for example, alkali metal salts such as lithium salt, sodium salt, and potassium salt; or organic salt such as ammonium salt and alkylamine salt. The preferred salt is sodium salt.

The polarizing element of the present invention contains the azo compound represented by formula (1) to formula (3), and further contains any azo compound represented by formula (6). According to the polarizing element of the present invention, the performance of the chromaticity a* value and b* value, monomer transmittance, and average transmittance in a specific wavelength band can be adjusted to the preferable range described later.

The blending ratio of the above-mentioned azo compound in the polarizing element is adjusted so that the transmittance and the chromaticity become the preferable ranges described later. The performance of the polarizing element depends not only on the mixing ratio of the azo compounds in the polarizing element, but also on the swelling degree, or extension ratio, dyeing time, dyeing temperature, pH during dyeing, and salt of the substrate that adsorbs the azo compound. And other factors. Therefore, the blending ratio of each azo compound can be determined according to the swelling degree of the substrate, the temperature, time, pH during dyeing, the type of salt, the concentration of the salt, and the extension ratio. Such adjustment of the blending ratio can be carried out by those in the technical field to which the invention pertains according to the description described below without repeated tests.

(Penetration rate)

(I) The difference of the average transmittance of the two wavelength bands

The preferred polarizing element of the present invention is the average between specific wavelength bands The difference in transmittance is below the specified value. The average transmittance is the average value of the transmittance in a specific wavelength band. The transmittance is the transmittance after visibility correction obtained according to JIS Z 8722:2009. The transmittance is measured by measuring the sample (such as polarizing element or polarizing plate), measuring the spectral transmittance of each wavelength from 400 to 700nm every 5nm or 10nm, and then calibrating the visibility with a 2 degree field of view (light source C) Out.

The wavelength bands of 420nm to 480nm, 520nm to 590nm, and 600nm to 640nm are the main wavelength bands used in the calculation of the isochromatic function when displaying colors in JIS Z 8781-4:2013. Specifically, in the XYZ and other color functions of JIS Z 8701, the source 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 value of z(λ), which is the maximum value, is set to 100, the respective wavelengths representing values above 20 are the respective wavelength bands of 420 nm to 480 nm, 520 nm to 590 nm, and 600 nm to 640 nm. The preferred one of the polarizing element of the present invention is that the transmittance in each wavelength band is adjusted to a value within a specified range.

The polarizing element of the present invention is measured by measuring the transmittance (hereinafter, also referred to as "parallel bit transmittance") in a state in which two polarizing elements are stacked and arranged so that the absorption axis directions are parallel to each other (in white display), The absolute value of the difference between the average transmittance of 420nm to 480nm and the average transmittance of 520nm to 590nm is preferably 2.5% or less, more preferably 1.8% or less, and even better, 1.5% or less, especially better Is below 1.0%. Furthermore, for 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, and more preferably Those who are less than 1.5%, even better are less than 1.0%. Such a polarizing element can display a white color like high-quality paper in parallel position.

In addition, the transmittance (hereinafter, also referred to as "cross-bit transmittance") measured when two polarizing elements are superimposed and arranged so that the absorption axis directions are orthogonal to each other (during black display), 420nm The absolute value of the difference between the average transmittance to 480nm and the average transmittance of 520nm to 590nm is less than 0.6%, and the absolute value of the difference between the average transmittance of 520nm to 590nm and the average transmittance of 600nm to 640nm The value is preferably 0.6% or less. Such a polarizing element can display colorless black in orthogonal positions. Furthermore, for the orthogonal bit transmittance, the absolute value of the difference between the average transmittance from 420nm to 480nm and the average transmittance from 520nm to 590nm is preferably less than 0.3%, and even better is 0.2% Below, the best ones are below 0.1%. For the orthogonal 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 0.3% or less, and even better is 0.2% or less, especially The best ones are below 0.1%.

Furthermore, the respective average transmittances of the monomer transmittance, parallel transmittance, and orthogonal transmittance in the wavelength bands of 380nm to 420nm, 480nm to 520nm, and 640nm to 780nm are the above wavelength bands. When the average transmittance of 420nm to 480nm, 520nm to 590nm, and 600nm to 640nm is adjusted to the above, it is not easy to be greatly affected by the pigment, but it is better to adjust to some extent. The difference between the average transmittance of the wavelength band from 380nm to 420nm and the average transmittance of 420nm to 480nm is preferably 15% or less. The difference between the average transmittance of 480nm to 520nm and the average transmittance of 420nm to 480nm is 15% or less, average transmittance from 480nm to 520nm, The difference between the average transmittance from 520nm to 590nm is 15% or less, and the difference between the average transmittance from 640nm to 780nm and the average transmittance from 600nm to 640nm is preferably 20% or less.

(II) monomer penetration rate

The preferred polarizing element of the present invention has a monomer transmittance of 35% to 60%. The transmittance of the monomer is the transmittance corrected for visibility based on JIS Z 8722:2009 for one measurement sample (such as a polarizing element or a polarizing plate). The performance of the polarizing plate is to find the higher transmittance, but if the single transmittance is 35% to 60%, even if it is used in a display device, it will display bright without discomfort. If the monomer transmittance exceeds 60%, sometimes the degree of polarization is significantly reduced, which is not good. The higher the transmittance, the more the degree of polarization tends to decrease. Therefore, from the viewpoint of the balance with the degree of polarization, the monomer transmittance is preferably 36% to 55%, and even better is 37% to 55 %.

(III) Average transmittance of specific wavelength band

The polarizing element should preferably have an average transmittance of 25% to 55% in the wavelength band from 520nm to 590nm measured in parallel. When such a polarizing element is installed in a display device, it can be a bright and clear display device with high brightness. The transmittance of the wavelength band from 520nm to 590nm is based on 1 of the main wavelength bands of the isochromatic function used 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 visibility according to the isochromatic 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 better the average transmittance of the wavelength band from 520nm to 590nm measured in parallel position is 27% to 45%, Even better is 28% to 40%. Furthermore, the degree of polarization of the polarizing element at this time is preferably 50% to 100%, more preferably 60% to 100%, and even more preferably 70% to 100%. The higher the degree of polarization, the better, but in the relationship between the degree of polarization and the transmittance, depending on the importance of brightness or the degree of polarization (or contrast), it can be adjusted to a suitable transmittance and degree of polarization.

(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. The object color display method determined in JIS Z 8781-4:2013 is equivalent to the object color display method specified by the International Commission on Illumination (abbreviation: 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, and the absorption axis directions are arranged so that two measurement samples are parallel to each other. The chromaticity a* value and b* value obtained for the state of the sample (when displayed in white) are expressed as a*-p and b*-p. Arrange the two measurement samples so that their absorption axis directions are orthogonal to each other The chromaticity a* value and b* value obtained in the state (during black display) are expressed as a*-c and b*-c.

The preferred polarizing element of the present invention is that the absolute values of a*-s and b*-s are respectively 1.0 or less, and the absolute values of a*-p and b*-p are preferably 2.0 or less. Such a polarizing element can display high-quality white when the monomer is a neutral color. The absolute value of a*-p and b*-p of the polarizing element is preferably 1.5 or less, and even more preferably 1.0 or less. Furthermore, the absolute values of the polarizing element systems a*-c and b*-c are preferably 2.0 or less, and more preferably 1.0 or less. When such a polarizing element is displayed in black, it can display no The color of black.

As long as the absolute value of the chromaticity a* value and b* value is 0.5, humans can perceive the difference in color, and sometimes people perceive a big difference in color. Therefore, in the 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 respectively below 1.0, it is possible to obtain white during white display and almost black during black display Can not confirm other good color polarizers. Specifically, it is possible to achieve colorlessness in parallel positions, that is, white as high-quality paper, and to achieve clear black with a colorless high-level sense in orthogonal positions.

The polarizing element of the present invention has high contrast and high transmittance, and at the same time, it has colorlessness and high degree of polarization in a single body. Furthermore, the polarizing element of the present invention can show white (paper white) like high-quality paper in white display, and can show colorless black in black display, especially clear black with high quality. So far, there is no polarizing element with such high transmittance and colorlessness. The polarizing element of the present invention has higher durability, especially durability to high temperature and high humidity.

In addition, the polarizing element of the present invention absorbs very little light with a wavelength of 700 nm or more, so it has the advantage of less heat generation even if it is irradiated with light such as sunlight. For example, when a liquid crystal display is used outdoors, sunlight illuminates the liquid crystal display, and as a result, it also illuminates the polarizing element. Sunlight also has wavelengths above 700nm, including near-infrared rays that have a heating effect. For example, a polarizing element using an azo compound described in Example 3 of Japanese Patent Publication No. 02-061988, because it absorbs near-infrared light with a wavelength around 700nm, although it generates some heat, the polarizing element of the present invention is near-infrared The line absorbs very little, so even if it is exposed to sunlight outdoors, it will generate less heat. The polarizing element of the present invention is excellent in that it has less heat generation and less deterioration.

Hereinafter, when an azo compound is adsorbed on a substrate made of a polyvinyl alcohol-based resin and produced, as an example, a specific method of producing a polarizing element will be described. In addition, the manufacturing method of the polarizing element of the present invention is not limited to the following manufacturing methods.

(Preparation of Embryo Membrane)

The embryonic membrane system can be produced by making a polyvinyl alcohol-based resin film. The polyvinyl alcohol-based resin system is not particularly limited, and commercially available products can be used, or those synthesized by a known method can also be used. The polyvinyl alcohol-based resin system can be obtained, for example, by saponifying a polyvinyl acetate-based resin. In addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, the polyvinyl acetate-based resin can be exemplified by copolymers of vinyl acetate and other monomers copolymerizable with vinyl acetate. Examples of other single systems 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 resin can also be modified, such as polyvinyl formaldehyde or polyvinyl acetal modified with aldehydes. In addition, the degree of polymerization of polyvinyl alcohol-based resin means the average degree of polymerization of viscosity, which can be obtained by a well-known technique in the technical field, and is usually about 1000 to 10,000, and more preferably, the degree of polymerization is 1500 to 6000. about.

The method for producing the polyvinyl alcohol-based resin film is not particularly limited, and the film can be produced by a known method. At this time, the polyvinyl alcohol resin film It may contain glycerin, ethylene glycol, propylene glycol, low molecular weight polyethylene glycol, etc. as plasticizers. The amount of the plasticizer is preferably 5 to 20% by mass in the total amount of the film, and more preferably 8 to 15% by mass. The film thickness of the embryonic membrane is not particularly limited, but it is, for example, about 5 μm to 150 μm, preferably about 10 μm to 100 μm.

(Swelling step)

Swelling treatment is applied to the embryonic membrane obtained by the above. The better swelling treatment is to immerse the embryonic membrane in a solution at 20 to 50°C for 30 seconds to 10 minutes. The solution is preferably water. The better stretching ratio is adjusted to 1.00 to 1.50 times, preferably 1.10 to 1.35 times. When shortening the manufacturing time of the polarizing element, the swelling treatment for swelling the embryonic membrane may be omitted in the dyeing treatment described later.

(Dyeing step)

In the dyeing step, the embryonic membrane is subjected to swelling treatment to adsorb and impregnate the azo compound in the resulting resin membrane. When the swelling step is omitted, the swelling treatment of the embryonic membrane can be performed simultaneously in the dyeing step. The adsorption and impregnation treatment of the azo compound is the coloring step of the resin film, so it is the coloring step.

As the azo compound, the azo compound represented by the formula (1), the formula (2), and the formula (3) or a mixture of its salt is used, and any azo compound represented by the formula (6) or a salt thereof may be used. In addition, the azo compounds of the dichroic dyes exemplified in "Application of Functional Pigments" (published by CMC Co., Ltd., first edition issued, supervision by Masahiro Irie, pages 98 to 100) can also be used in this case without harm The degree of performance of the polarizing element 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 salts are, for example, alkali metal salts such as lithium salts, sodium salts, and potassium salts; or organic salts such as ammonium salts and alkylamine salts, preferably sodium salts.

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, the resin film is preferably immersed in a dyeing solution, or it may be performed by applying the dyeing solution to the resin film. Each azo compound in the dyeing solution can be adjusted in the range of 0.001 to 10% by mass, for example.

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

In addition to azo compounds, the dyeing solution can also contain dyeing auxiliaries as needed. Examples of the dyeing auxiliary system include sodium carbonate, sodium bicarbonate, sodium chloride, sodium sulfate, anhydrous sodium sulfate, and sodium tripolyphosphate. The content of the dyeing auxiliary can be adjusted at any concentration according to the time and temperature required for the dyeability of the dye, but the content of each is preferably 0.01 to 5 mass% in the dyeing solution, and more preferably 0.1 to 2 mass% good.

(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. The washing step 1 is a step of washing the dyeing solution attached to the surface of the resin film in the dyeing step. By performing the washing step 1, it is possible to suppress the migration of dye in the liquid to be treated next. In the washing step 1, water can generally be used as a washing liquid. The cleaning is preferably performed by immersing in the cleaning liquid, or by applying the cleaning liquid to the resin The membrane is washed. The washing time is not particularly limited, but 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, hydrophilic polymer, polyvinyl alcohol resin in this case) does not dissolve. It is generally washed at 5 to 40°C. However, even if there is no washing step 1, there is no problem in performance, so the washing step can be omitted.

(Steps containing crosslinking agent and/or waterproofing agent)

After the dyeing step or the washing step 1, a step containing a crosslinking agent and/or a waterproofing agent may be performed. The method of containing a cross-linking agent and/or a water-repellent agent in the resin film is preferably immersed in the treatment solution, and the treatment solution can also be coated or coated on the resin film. The treatment solution includes at least one of a crosslinking agent and/or a water repellent, and a solvent. The temperature of the treatment solution in this step is preferably 5 to 70°C, more preferably 5 to 50°C. The processing time in this step is preferably 30 seconds to 6 minutes, more preferably 1 to 5 minutes.

As the crosslinking agent, boron compounds such as boric acid, borax or ammonium borate, polyaldehydes such as glyoxal or glutaraldehyde, polyisocyanate compounds such as biuret type, trimeric isocyanate type or block type, and sulfuric acid can be used. Titanium compounds such as titanyl, etc., but ethylene glycol glycidyl ether, polyamide epichlorohydrin, etc. may also be used. The water repellent system may include, for example, peracidified succinic acid, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerol diglycidyl ether, ammonium chloride or magnesium chloride, etc. However, it is better to use boric acid. The solvent for the crosslinking agent and/or water repellent is preferably water, but it is not limited. The concentration of the cross-linking agent and/or water-repellent agent can be appropriately determined by the manufacturer according to the type. However, if boric acid is used as an example, the concentration in the treatment solution The concentration is preferably 0.1 to 6.0% by mass, and more preferably 1.0 to 4.0% by mass. However, it does not need to contain a cross-linking agent and/or a water-repellent agent. When the time is to be shortened, when the cross-linking treatment or water-repellent treatment is not required, this treatment step can be omitted.

(Extension step)

After the dyeing step, the washing step 1, or the step containing a cross-linking agent and/or a water-repellent agent, an extension step is performed. The stretching step is to uniaxially stretch the resin film. The extension method can be either a wet extension method or a dry extension method. The extension magnification is preferably 3 times or more, more preferably 4 to 8 times, and particularly good 5 to 7 times.

In the dry stretching method, when the stretching heating medium is an air medium, the temperature of the air medium is preferably from room temperature to 180°C to stretch the resin film. In addition, the humidity is preferably in an environment of 20 to 95% RH. The heating method includes, for example, an inter-roll zone stretching method, a roll heating stretching method, a rolling method, and an infrared heating stretching method, but the stretching method is not limited. The extension step can also be performed in one stage, but can also be performed in multiple stages of two or more stages.

In 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 being immersed in a solution containing at least one crosslinking agent and/or water repellent. The cross-linking agent and the water-repellent agent may be the same as those described in the procedure for containing the cross-linking agent and/or the water-repellent agent. The concentration in the solution of the crosslinking agent and/or water repellent 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 40 to 60°C, and more preferably 45 to 58°C. Extension time is usually 30 seconds to 20 Minutes, but 2 to 5 minutes is better. The wet stretching step can be performed by one-stage stretching, but can also be performed by two-stage or more multi-stage stretching.

(Washing step 2)

After the stretching step, the crosslinking agent and/or the precipitation of the waterproofing agent, or foreign matter may sometimes adhere to the surface of the resin film. Therefore, 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, and the resin film can also be cleaned by coating or coating the solution. The washing liquid is preferably water. It can carry out one-stage cleaning treatment, and can also carry out more than two-stage multi-stage treatment. The solution temperature in the washing step is not particularly limited, but it is usually 5 to 50°C, preferably 10 to 40°C.

In addition to the treatment liquid or its solvent used in the treatment step, water, for example, dimethyl sulfide, N-methylpyrrolidone, methanol, ethanol, propanol, isopropanol, glycerin, ethylene glycol, Alcohols such as propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, or trimethylolpropane, amines such as ethylenediamine and diethylenetriamine, etc., but are not limited thereto. The best treatment liquid or its solvent is water. In addition, these treatment liquids or their solvent systems may be used singly, or a mixture of two or more kinds may be used.

(Drying step)

After the stretching step or the washing step 2, the resin film is dried. The drying process can be carried out by natural drying, but in order to further improve the drying efficiency, it can be carried out by roller compression, air knife, or suction roll, etc. to remove moisture on the surface, and/or by air drying. The drying treatment temperature is preferably 20 to 100°C for drying treatment, and 60 to 100°C for drying. The rationale is better. 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 the azo compounds in the dyeing step, the temperature of the dyeing solution, the pH, the salt type, the salt concentration, and the dyeing time, and the extension The stretching ratio in the step is adjusted so that the polarizing element satisfies at least 1 of the following conditions (i) to (v), and it is more appropriate to proceed in a way that satisfies the conditions (vi) and (vii) more. .

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

(ii) Regarding the orthogonal bit transmittance, the absolute value of the difference between the average transmittance of 420nm to 480nm and the average transmittance of 520nm to 590nm is 0.6 or less, the average transmittance of 520nm to 590nm and the difference of 600nm to 640nm The absolute value of the difference in average transmittance is 0.6 or less.

(iii) The monomer penetration rate is 35% to 60%.

(iv) The absolute values of the a* value and the b* value are 1 or less for the polarizing element alone, and 2 or less for the parallel position.

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

(vi) Regarding the parallel position transmittance, the average transmittance from 520nm to 590nm is 25 to 55%.

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

By the above method, a polarizing element containing at least a combination of the azo compound represented by formula (1) to formula (3) can be manufactured. Such a polarizing element has higher transmittance and high degree of polarization than before, but when two polarizing elements are stacked so that the absorption axis direction becomes parallel, they can appear as white as high-quality paper, and The monomer has a neutral color (neutral gray) hue. Furthermore, when the polarizing element is arranged by overlapping two polarizing elements so that the absorption axis direction becomes orthogonal, a colorless black with high-quality appearance is displayed. In addition, the polarizing element has high durability.

<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 transparent protective layer is provided for the purpose of improving the water resistance or handling properties of the polarizing element.

The transparent protective layer is a protective film formed of a transparent material. The protective film is a film with a layer shape 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 form the same layer to set the same function. An example of the plastic constituting the protective film can be, for example, polyester resin, acetate resin, polyether ether resin, polycarbonate resin, polyamide resin, polyimide resin, and polyolefin. Resin and acrylic resin, etc. Plastic resin; Acrylic, urethane, acrylic urethane, epoxy, and silicone resins such as thermosetting resins or ultraviolet curable resins, etc., among them, poly The olefin-based resin system includes, for example, an amorphous polyolefin-based resin and a resin having a polymerization unit of a cyclic polyolefin, such as a norbornene-based monomer or a polycyclic norbornene-based monomer. Generally speaking, it is better to choose a protective film that does not hinder the performance of the polarizing element after the laminated protective film. Such a protective film is triacetyl cellulose (TAC) and norbornene composed of cellulose acetate resin It is especially good. Moreover, as long as the protective film system does not impair the effects of the present invention, it may be treated with hard coating treatment, anti-reflection treatment, anti-adhesion, diffusion, anti-glare, or the like.

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 system constituting the adhesive layer is not particularly limited, but a polyvinyl alcohol-based adhesive is preferred. Examples of the polyvinyl alcohol-based adhesive include Gohsenol NH-26 (manufactured by Nippon Gosei Co., Ltd.) and Exceval RS-2117 (manufactured by Kuraray Co., Ltd.), but are not limited thereto. A crosslinking agent and/or water repellent can be added to the adhesive system. The polyvinyl alcohol-based adhesive is preferably a maleic anhydride-isobutylene copolymer, and an adhesive mixed with a crosslinking agent can be used as needed. Maleic anhydride-isobutylene copolymer system, for example: Isobam # 18 (manufactured by Kuraray), Isobam # 04 (manufactured by Kuraray), Ammonia-modified Isobam # 104 (manufactured by Kuraray), Ammonia-modified Isobam # 110 (manufactured by Kuraray) ), Isobam # 304 (manufactured by Kuraray), Isobam # 310 (manufactured by Kuraray), etc. At this time, a water-soluble multi-epoxy compound can be used in the crosslinking agent. The water-soluble multi-epoxy compound series can be, for example, Dynacol EX-521 (Nagase Chemtech Corporation), Tetrad-C (Mitsui Gas Chemical Corporation), etc. Moreover, well-known adhesives of urethane type, acrylic type, and epoxy type can also be used for adhesives other than polyvinyl alcohol-type resin. Particularly, it is better to use polyvinyl alcohol modified with acetyl acetone. Furthermore, the cross-linking agent is preferably polyaldehyde. For the purpose of improving the adhesive strength of the adhesive or improving the water resistance, additives such as zinc compounds, chlorides, and iodides may be contained individually or at a concentration of about 0.1 to 10% by mass. The additive system of the adhesive is not particularly limited, and the manufacturer can select it appropriately. After bonding the transparent protective layer and the polarizing element with an adhesive, they can be dried or heat-treated at an appropriate temperature to obtain a polarizing plate.

Depending on the circumstances, the polarizing plate is attached to display devices such as liquid crystal, organic electroluminescence (commonly known as OLED or OEL), etc., and thereafter, it can be installed on the surface of the non-exposed protective layer or film to improve the viewing angle And/or various functional layers to improve contrast, layers or films with brightness enhancement properties. Various functional layers are, for example, layers or films that control phase difference. Preferably, the polarizing plate is attached to these films or display devices with an 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 film. The coating method is better to make the layer with these various functions, but the film with the function can also be pasted through an adhesive or adhesive.

The polarizing plate of the present invention is a highly durable polarizing plate. Although it has high transmittance and high degree of polarization, it can realize colorlessness. In particular, it can appear white as high-quality paper when displaying white. And it can show neutral black when displayed in black.

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, computers, clocks, notebook computers, and word processors , LCD TVs, polarizers, polarized glasses, navigators, and indoor and outdoor measuring devices or displays, etc. In particular, the polarizing element or polarizing plate of the present invention can be suitably used 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 display white and neutral black like high-quality paper. Furthermore, the liquid crystal display device is a liquid crystal display device having high durability, high reliability, long-term high contrast, and high color reproducibility.

[Example]

Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited by these.

[Example 1]

The polyvinyl alcohol film (VF-PS manufactured by Kuraray) with a saponification degree of 99% or more and an average degree of polymerization of 2400 is immersed in warm water at 45°C for 2 minutes, and swelling treatment is applied to make the extension ratio 1.30 times. The swelled film was prepared in compound example 1, compound example 22 of 0.130 parts by mass, compound example 46 of 0.400 parts by mass, containing 2000 parts by mass of water, 2.0 parts by mass of sodium tripolyphosphate, 2.0 parts by mass of anhydrous Glauber's salt, and 0.039 parts by mass. , 0.14 parts by mass of Compound Example 50 (CI Direct Orange 39) was immersed in a liquid at 45°C for 20 minutes and 00 seconds to dye the film with an azo compound. The resulting film was heated at 40°C containing 20 g/l of boric acid (manufactured by Societa Chimica Larderello s.p.a.) Soak in the aqueous solution for 1 minute. The resulting film was stretched to 5.0 times, and at the same time, the stretching treatment was performed for 5 minutes in an aqueous solution containing 30.0 g/l of boric acid at 50°C. The stretched film keeps its tensioned state while being treated with water at 25°C for 20 seconds. Thereafter, the resulting film was dried at 70°C for 9 minutes to produce a polarizing element. For this polarizing element, a polyvinyl alcohol adhesive was laminated with an alkali-treated triacetyl cellulose film (manufactured by Fuji Photo Film Co., Ltd., ZRD-60) to prepare a polarizing plate. The obtained polarizing plate maintains the optical properties of the above-mentioned polarizing element, especially monomer transmittance, hue, degree of polarization, etc. This polarizing plate was used as the measurement sample of Example 1.

[Examples 2 to 9]

In the dyeing step, except that the dyeing time was changed to 18 minutes, 10 minutes, 8 minutes, 5 minutes 30 seconds, 3 minutes 30 seconds, 2 minutes 30 seconds, 1 minute 30 seconds, and 40 seconds in Examples 2-9, respectively. Except for the points, the same operation as in Example 1 was performed to obtain a polarizing element, and a polarizing plate was produced.

[Example 10]

Except that the liquid containing the azo compound in the dyeing step used in Example 1 was changed to the compound example 1, which contained 2000 parts by mass of water, 2.0 parts by mass of sodium tripolyphosphate, 2.0 parts by mass of anhydrous Glauber's salt, and 0.040 parts by mass. Except for the liquid of compound example 15, 0.400 parts by mass of compound example 46, and 0.135 parts by mass of compound example 50, the same operation as in Example 1 was performed to obtain a polarizing plate.

[Example 11]

Except that the liquid containing the azo compound in the dyeing step used in Example 1 was changed to contain 2000 parts by mass of water and 2.0 parts by mass of sodium tripolyphosphate Parts, 2.0 parts by mass of anhydrous Glauber's salt, 0.045 parts by mass of compound example 1, 0.090 parts by mass of compound example 43, 0.430 parts by mass of compound example 46, 0.130 parts by mass of compound example 50, and the rest were the same as in Example 1 The polarizing plate is obtained by the same operation.

[Example 12]

Except that the liquid containing the azo compound in the dyeing step used in Example 1 was changed to the compound example 1, which contained 2000 parts by mass of water, 2.0 parts by mass of sodium tripolyphosphate, 2.0 parts by mass of anhydrous Glauber's salt, and 0.037 parts by mass. Except for the liquid of compound example 20 of 0.400 parts by mass, compound example 46 of 0.400 parts by mass, and compound example 50 of 0.145 parts by mass, the same operations as in Example 1 were performed to obtain a polarizing plate.

[Example 13]

Except that the liquid containing the azo compound in the dyeing step used in Example 1 was changed to compound example 1, which contained 2000 parts by mass of water, 2.0 parts by mass of sodium tripolyphosphate, 2.0 parts by mass of anhydrous Glauber's salt, and 0.033 parts by mass. Except for the liquid of compound example 44 of 0.400 parts by mass, compound example 46 of 0.400 parts by mass, and compound example 50 of 0.140 parts by mass, the same operations as in Example 1 were performed to obtain a polarizing plate.

[Example 14]

Except that the liquid containing the azo compound in the dyeing step used in Example 1 was changed to the compound example 1, which contained 2000 parts by mass of water, 2.0 parts by mass of sodium tripolyphosphate, 2.0 parts by mass of anhydrous Glauber's salt, and 0.024 parts by mass. Parts of compound example 29, 0.400 parts by mass of compound example 46, 0.125 parts by mass of compound example 50 except for the liquid, and the rest were the same as in Example 1 The polarizing plate is obtained by the same operation.

[Example 15]

Except that the liquid containing the azo compound in the dyeing step used in Example 1 was changed to the compound example 1, which contained 2000 parts by mass of water, 2.0 parts by mass of sodium tripolyphosphate, 2.0 parts by mass of anhydrous Glauber's salt, and 0.036 parts by mass. Except for the liquid of compound example 35 of 0.420 parts by mass, compound example 46 of 0.420 parts by mass, and compound example 50 of 0.140 parts by mass, the same operations as in Example 1 were performed to obtain a polarizing plate.

[Example 16]

Except that the liquid containing an azo compound in the dyeing step used in Example 1 was changed to a compound example 1, which contained 2000 parts by mass of water, 2.0 parts by mass of sodium tripolyphosphate, 2.0 parts by mass of anhydrous Glauber's salt, and 0.036 parts by mass Except the liquid of compound example 41 of 0.420 parts by mass, compound example 46 of 0.420 parts by mass, and compound example 50 of 0.140 parts by mass, the same operations as in Example 1 were performed to obtain a polarizing plate.

[Example 17]

In the liquid containing the azo compound in the dyeing step used in Example 1, except that 0.036 parts by mass of Compound Example 1 was changed to 0.089 parts by mass of Compound Example 12 (CI Direct Red 81), the rest was the same as in Example 1. The polarizing plate is obtained by the same operation.

[Example 18]

In the liquid containing the azo compound in the dyeing step used in Example 1, except that 0.036 parts by mass of Compound Example 1 was changed to 0.077 parts by mass of Compound Example 11 (C.I. Direct Red 117), the rest was the same as in Example 1. With the same operation, the polarizing element and polarizing plate of the present invention are prepared.

[Example 19]

In the liquid containing the azo compound in the dyeing step used in Example 1, except that 0.036 parts by mass of Compound Example 1 was changed to 0.055 parts by mass of Compound Example 14, the remaining operations were the same as in Example 1 to obtain a polarizing plate .

[Example 20]

In the liquid containing the azo compound in the dyeing step used in Example 1, except that 0.400 parts by mass of compound example 46 was changed to 0.410 parts by mass of compound example 48, the remaining operations were the same as in Example 1 to obtain a polarizing plate .

[Example 21]

In the liquid containing the azo compound in the dyeing step used in Example 1, except that 0.140 parts by mass of compound example 50 was changed to 0.095 parts by mass of compound example 51, the remaining operations were the same as in Example 1 to obtain a polarizing plate .

[Example 22]

In the liquid containing the azo compound in the dyeing step used in Example 1, except that 0.140 parts by mass of Compound Example 50 was changed to 0.135 parts by mass of CI Direct Yellow 28, the remaining operations were the same as in Example 1 to obtain polarized light board.

[Example 23]

In the liquid containing an azo compound in the dyeing step used in Example 1, except that 0.140 parts by mass of Compound Example 50 was changed to 0.110 mass Except for C.I. Direct Orange 72, the same operation as in Example 1 was performed to obtain a polarizing plate.

[Comparative Examples 1 to 6]

According to the method of Example 1 of Patent Document 3, a polarizing element was produced. At this time, the immersion time in the aqueous solution containing the azo compound was changed to 13 minutes, 11 minutes and 30 seconds, 10 minutes, 8 minutes, 6 minutes, and 4 minutes in Comparative Examples 1 to 6, respectively. Using the polarizing element obtained in this way, the same operation as in Example 1 was performed to obtain a polarizing plate.

[Comparative Example 7]

A high-transmittance dye-based polarizing plate SHC-115 made by Polatechno, which has a neutral gray color, was obtained as a measurement sample.

[Comparative Example 8]

The dye-based polarizing plate SHC-128 manufactured by Polatechno, which is a neutral gray with high contrast, was used as a measurement sample.

[Comparative Examples 9 to 14]

According to the formula of Comparative Example 1 in JP 2008-065222, the iodine-based polarizer without azo compound was prepared by arbitrarily changing the iodine-containing time, and the polarizer was obtained by the same operation as in Example 1, as the measurement sample .

[Comparative Example 15]

The iodine-based polarizing plate SKW-18245P made by Polatechno, which showed paper white in the parallel position, was obtained as a measurement sample.

[Comparative Example 16]

According to the Japanese Patent Application Publication No. 11-218611 of the dye-based polarizer The polarizing plate obtained by the method of Example 1 was used as a measurement sample.

[Comparative Example 17]

The polarizing plate was obtained according to the method of Example 3 of Japanese Patent No. 4162334 of the dye-based polarizing plate as a measurement sample.

[Comparative Example 18]

The polarizing plate was obtained according to the method of Example 1 of Patent No. 4360100 of the dye-based polarizing plate as a measurement sample.

[Comparative Example 19]

Except that 0.039 parts by mass of Compound Example 1 is changed to 0.087 parts by mass of CI Direct Red 80, which is an azo compound with a urea-based skeleton in the same color, the transmittance of the orthogonal position is almost unchanged, and the color is adjusted so that the color becomes black. Otherwise, the same operation as in Example 1 was performed to obtain a polarizing plate as a measurement sample.

[Comparative Example 20]

Except that 0.039 parts by mass of Compound Example 1 is changed to 0.080 parts by mass of CI Direct Red 84, which is an azo compound with the same color and has a urea-based skeleton, the transmittance of the orthogonal position is almost unchanged, and the color is adjusted to be black. , And the rest was the same operation as in Example 1 to obtain a polarizing plate as a measurement sample.

[Comparative Example 21]

Except that 0.039 parts by mass of Compound Example 1 is changed to 0.052 parts by mass of CI Direct Red 7, which is an azo compound containing the same color dichroic dianisidine (Dianisidine) skeleton, the transmittance of the orthogonal position is almost unchanged, and Except for the way the color becomes black, the rest is the same as in Example 1. The polarizing plate obtained by the operation was used as the measurement sample.

[Comparative Example 22]

Except that 0.039 parts by mass of Compound Example 1 is changed to 0.061 parts by mass of CI Direct Red 45, which is an azo compound with the same color and dichroism, the transmittance of the orthogonal position is almost unchanged, and the color is designed to be black. , And the rest was the same operation as in Example 1 to obtain a polarizing plate as a measurement sample.

[Comparative Example 23]

Except that 0.130 parts by mass of Compound Example 22 was changed to 0.075 parts by mass of CI Direct Blue 6 of the dianisidine skeleton of the azo compound of the same color, the transmittance of the orthogonal position was almost unchanged, and the design was designed so that its color became black Otherwise, the same operation as in Example 1 was performed to obtain a polarizing plate as a measurement sample.

[Comparative Example 24]

Except that 0.130 parts by mass of Compound Example 22 was changed to 0.085 parts by mass of the azo compound of the same color as CI Direct Blue 15, the transmittance of the orthogonal position was almost unchanged, and the color was designed in such a way that the color became black. The polarizing plate was obtained by the same operation as in Example 1 and used as the measurement sample.

[Comparative Example 25]

Except that 0.130 parts by mass of compound example 22 was changed to 0.105 parts by mass of CI direct blue 71 of the same color as the azo compound, the transmittance of the orthogonal position was almost unchanged, and the color was designed in such a way that the color became black. The polarizing plate was obtained by the same operation as in Example 1 and used as the measurement sample.

[Comparative Example 26]

Except that 0.400 parts by mass of Compound Example 46 was changed to 0.43 parts by mass of CI Direct Blue 199, a direct dye of the same color, the transmittance of the orthogonal position was almost unchanged, and the color was designed in such a way that the color became black. The polarizing plate was obtained by the same operation as 1 and used as the measurement sample.

[Comparative Example 27]

Except that 0.41 parts by mass of CI Direct Blue 218, which is the same as the direct dye of the same color, is used instead of 0.400 parts by mass of Compound Example 46, the transmittance of the orthogonal position is almost unchanged, except that the color becomes black. , And the rest was the same operation as in Example 1 to obtain a polarizing plate as a measurement sample.

[Evaluation]

The evaluation of the measurement samples obtained in Examples 1 to 23 and Comparative Examples 1 to 27 was performed as follows.

(a) Monomer transmittance Ts, parallel position transmittance Tp, and orthogonal position transmittance Tc

Using a spectrophotometer ("U-4100" manufactured by Hitachi, Ltd.), the monomer transmittance Ts, parallel transmittance Tp, and orthogonal transmittance Tc of each measurement sample were measured. Here, the monomer transmittance Ts is to measure the transmittance of each wavelength when measuring one sample. Parallel transmittance Tp is the spectral transmittance of each wavelength measured by stacking two measurement samples so that the absorption axis direction becomes parallel. The cross-position transmittance Tc is the spectral transmittance measured by stacking two polarizing plates so that their absorption axes are orthogonal. The measurement is performed at a wavelength in the range of 400 to 700 nm.

Calculate the average of the parallel bit transmittance Tp and the orthogonal bit transmittance Tc from 420 to 480nm, the average value from 520 to 590nm, and 600 The average value to 640nm is shown in Table 1.

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

The monomer transmittance Ys, the parallel position transmittance Yp, and the orthogonal position transmittance Yc of each measurement sample are respectively determined. The monomer transmittance Ys, the parallel position transmittance Yp, and the orthogonal position transmittance Yc are calculated for the above-mentioned monomer at a specific wavelength interval dλ (here 5nm) in the wavelength region of 400 to 700nm The transmittance Ts, parallel position transmittance Tp, and orthogonal position transmittance Tc are the transmittances corrected for visibility in accordance with JIS Z 8722:2009. Specifically, the above-mentioned monomer transmittance Ts, parallel position transmittance Tp, and orthogonal position transmittance Tc are substituted into the following formulas (I) to (III) and calculated respectively. 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 2-degree visual field isochromatic function. The results are shown in Table 1.

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

Table 2 shows the parallel position transmittance Tp and the orthogonal position transmittance Tc of the measurement samples obtained in Examples 1 to 23 and Comparative Examples 1 to 27, and the average value in each of 520 to 590 nm and The absolute value of the difference between the average value in 420 to 480nm, and the average value in 520 to 590nm and 600 to The absolute value of the difference between the average values in 640nm.

As shown in Table 1 and Table 2, the parallel position transmittance Tp of the measurement samples obtained in Examples 1 to 23 is more than 25% in the average value of 520 to 590 nm, and the average value of 420 to 480 nm is higher than that of 520 to 590 nm. Both the absolute value of the difference between the average value in 520 and the absolute value of the difference between the average value of 520 to 590 nm and the average value of 600 to 640 nm are 1.0%, which shows a very low value. Furthermore, the orthogonal position transmittance Tc of the measurement samples obtained in Examples 1 to 23 is the absolute value of the difference between the average value in 420 to 480 nm and the average value in 520 to 590 nm, and the average value in 520 to 590 nm The absolute value of the difference between the value and the average value in 600 to 640 nm is 0.6% or less, which shows a very low value. On the other hand, the measurement samples of Comparative Examples 7 to 27 are the absolute value of the difference between the average value of the parallel position transmittance Tp and the average value between the above wavelength bands of the orthogonal position transmittance Tc At least any one of the absolute values of the difference shows a high value.

(d) Polarization ρy

For each measurement sample, the degree of polarization ρy was obtained. The degree of polarization ρy is obtained by substituting the parallel transmittance Yp and the orthogonal transmittance Yc in the following formula. The results are shown in Table 3.

ρy={(Yp-Yc)/(Yp+Yc)} ^1/2 ×100

(e) Chromaticity a* value and b* value

For each measurement sample, in accordance with JIS Z 8781-4:2013, when measuring the monomer transmittance Ts, the chromaticity a in each of the parallel position transmittance Tp measurement and the orthogonal position transmittance Tc measurement *Value and b*value. The measurement is performed by using the above-mentioned spectrophotometer, and measuring from the transmission color, reflection color, and outdoor side. The light source is C light source. The results are shown in Table 3. Here, a*-s And b*-s, a*-p and b*-p, and a*-c and b*-c correspond to the monomer penetration rate Ts, the parallel position penetration rate Tp and the orthogonal position penetration rate Tc, respectively Chromaticity a* value and b* value at the time of measurement.

(f) Observation of color

For each measurement sample, superimpose two identical measurement samples on a white light source in parallel and orthogonal positions, and investigate the color observed at this time. The observation system was conducted by 10 observers visually, and the most observed colors are shown in Table 3. In addition, in Table 3, the color of the parallel position refers to the color of the state where two pieces of the same sample are overlapped so that the directions of the absorption axis are parallel to each other (when displaying white), and the color of the orthogonal position refers to the color of the absorption axis The directions are orthogonal to each other and the colors of the state of the same sample of 2 pieces (when displayed in black) are superimposed. Basically, the parallel color of the polarized color system is "white", and the color of the orthogonal position is "black", but in the embodiment, for example, white with a yellow hue shows "yellow", and black with a purple hue shows "purple". .

As shown in the results in Table 3, the measurement samples of Examples 1 to 23 have a monomer transmittance of 35% or more. In addition, the measurement samples of Examples 1 to 23 are that the absolute values of a*-s, b*-s, a*-c, and b*-c are 1.0 or less, and the absolute values of a*-p and b*-p are The value is below 2.0, which shows a very low value. When the measurement samples of Examples 1 to 23 are visually observed, they are displayed in parallel position as white as high-quality paper, and orthogonal position is displayed as high-quality The sense of clear black. On the other hand, in Comparative Examples 7 to 27, at least any one of a*-s, b*-s, a*-p, b*-p, a*-c, and b*-c showed high values to When visually observed, the parallel or orthogonal position is not colorless.

Therefore, it can be seen that although the polarizing element of the present invention has a high transmittance, when the absorption axis of the polarizing element is arranged in parallel, it can appear as white as high-quality paper, and has a neutral color (neutral The hue of gray, even with higher polarization and high transmittance, appears colorless in parallel. Furthermore, it can be seen that when the absorption axis of the polarizing element is arranged orthogonally, it is possible to obtain a polarizing element that displays high-quality colorless black.

Furthermore, it can be seen that in the measurement samples obtained in Examples 1 to 23, the transmittance is almost the same as the average transmittance of each wavelength, and even if the transmittance is high, it has a highly colorless hue, its white color and The degree of black polarization.

(g) Contrast

The contrast ratio was confirmed by calculating the ratio (Yp/Yc) of the parallel position transmittance measured using two identical measurement samples to the orthogonal position transmittance. Comparing Example 1 and Comparative Example 1 with a monomer transmittance of about 37%, the contrast of Example 1 is 3337, the contrast of Comparative Example 1 is 2219, and Example 1 is about 1.5 times that of Comparative Example 1. In addition, when comparing Example 3 with a monomer transmittance of about 39.5% and Comparative Example 3, the contrast of Example 3 is 276, the contrast of Comparative Example 3 is 137, and the contrast of Example 3 is about twice the contrast. From this, it can be seen that the polarizing plate of the present invention is compared with the conventional colorless polarizing plate in Patent Document 3, and its performance is improved.

(h) Durability test

Examples 1 to are used in an environment of 85°C and a relative humidity of 85%RH The measurement samples of 23 and Comparative Examples 9 to 15 were 240 hours. As a result, the degree of polarization of Comparative Examples 9 to 15 is reduced by more than 10%, which is lower than that of b*-c of -10, and the color of the appearance becomes blue. Especially when the two measurement samples are arranged in orthogonal positions, the Obviously blue. Specifically, it was confirmed that in Comparative Example 12, the monomer transmittance was 67.1% and the polarization degree was 30.8%. In Comparative Example 15, the transmission rate was 83.3% and the polarization degree was 5.4%, and the durability was low. In contrast, in the measurement samples of Examples 1 to 23, changes in transmittance and polarization degree or changes in hue were not observed.

From this, it can be seen that the liquid crystal display device using the polarizing element or the polarizing plate of the present invention is a liquid crystal display device having high reliability, long-term high contrast, and high color reproducibility.

Claims (12)

A polarizing element comprising: an azo compound or salt thereof represented by formula (1), an azo compound or salt thereof represented by formula (2), and an azo compound or salt thereof represented by formula (3),

In the formula, Ar ₁ represents a substituted phenyl or naphthyl group, Rr ₁ and Rr ₂ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group, and Xr ₁ represents Amino group that may have a substituent, a phenylamino group that may have a substituent, a phenylazo group that may have a substituent, a benzylamine that may have a substituent, or a benzylamine that may have a substituent base;

In the formula, Ab ₁ represents a substituted phenyl or naphthyl group, Rb ₁ to Rb ₆ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group, and Xb ₁ represents Amino groups that may have substituents, phenylamino groups that may have substituents, phenylazo groups that may have substituents, naphthotriazole groups that may have substituents, benzyl groups that may have substituents, Or a benzylamino group which may have a substituent;

In the formula, Ag ₁ and Ag ₂ each independently represent at least one selected from sulfo group, lower alkyl group, lower alkoxy group, lower alkoxy group having sulfo group, carboxyl group, nitro group, amine group, and substituted amine In the naphthyl group or the phenyl group of the substituent of the group consisting of a group, Rg ₁ and Rg ₂ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group. The polarizing element described in the first item of the patent application is related to the transmittance obtained when the aforementioned two polarizing elements are arranged so that the absorption axis directions become parallel to each other. The average of 420nm to 480nm The absolute value of the difference between the transmittance and the average transmittance from 520nm to 590nm is 2.5% or less, and the absolute value of the difference between the average transmittance from 520nm to 590nm and the average transmittance from 600nm to 640nm is 2.0% or less. The polarizing element described in item 1 or 2 of the scope of patent application, wherein the absolute value of a* value and b* value obtained when measuring the transmittance of natural light according to JIS Z 8781-4:2013 is: the aforementioned polarizing element The monomers are all 1 or less, and the two polarizing elements are arranged so that the absorption axis directions of the two polarizing elements are overlapped and arranged so that they are all 2 or less. The polarizing element described in item 1 or 2 of the scope of patent application, wherein the monomer transmittance of the aforementioned polarizing element is 35% to 60%, so that the two polarizing elements are mutually aligned with their absorption axis directions. The average transmittance from 520nm to 590nm is 25% to 55% when the state is overlapped in parallel. The polarizing element described in item 1 or 2 of the scope of patent application, wherein the azo compound represented by the aforementioned formula (2) is the azo compound represented by the formula (4),

In the formula, Ab ₁ , Rb ₁ to Rb ₄ , and Xb ₁ represent the same as those of the formula (2). The polarizing element described in item 1 or 2 of the scope of patent application, wherein the azo compound represented by the aforementioned formula (2) is the azo compound represented by the formula (5),

In the formula, Ab ₁ , Rb ₂ , Rb ₄ , and Xb ₁ represent the same as those of the formula (2). The polarizing element described in item 1 or 2 of the scope of patent application further contains the azo compound represented by formula (6) or its salt,

In the formula, Ry ₁ and Ry ₂ each independently represent a sulfo group, a carboxyl group, a hydroxyl group, a lower alkyl group, or a lower alkoxy group, and n represents an integer of 1 to 3. The polarizing element described in item 1 or 2 of the scope of patent application, wherein the two polarizing elements are mutually positive with respect to the absorption axis directions of the two polarizing elements. The absolute value of the difference between the average transmittance of 420nm to 480nm and the average transmittance of 520nm to 590nm is 0.6% or less, and the average transmittance of 520nm to 590nm The absolute value of the difference between the transmittance and the average transmittance between 600nm and 640nm is 0.6% or less. The polarizing element described in item 1 or 2 of the scope of the patent application, wherein the two polarizing elements are arranged so that the absorption axis directions of the two polarizing elements are overlapped and arranged so that the directions of their absorption axes are orthogonal to each other, measured in accordance with JIS Z 8781-4:2013 The absolute value of the a* value and b* value obtained when the natural light transmittance is 2 or less. The polarizing element described in claim 1 or 2, wherein the polarizing element contains a polyvinyl alcohol-based resin film as a base material. A polarizing plate is provided with the polarizing element described in any one of items 1 to 10 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 scope of patent application 1 to 10 or the polarizing plate described in the scope of patent application 11.