JP6853010B2 - Achromatic polarizing element, and achromatic polarizing plate and liquid crystal display device using this - Google Patents

Description

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

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

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

In order for the polarizing plate to be achromatic, it is necessary for the transmittance to be almost constant regardless of the wavelength in the parallel position or the orthogonal position, but it has been possible to obtain such a polarizing plate so far. There wasn't. The reason why the hues of white display and black display are different is that the wavelength dependence of the transmittance is not the same in the parallel position and the orthogonal position, and in particular, the transmittance is not constant over the visible light region. Furthermore, the fact that the dichroism is not constant over the visible light region is one of the factors that make it difficult to realize an achromatic polarizing plate.

Taking an iodine-based polarizing plate as an example, iodine-based polarizing plates using polyvinyl alcohol (hereinafter, also referred to as “PVA”) as a base material and iodine as a dichroic dye generally have 480 nm and 600 nm. Has absorption centered on iodine. Absorption of 480nm is polyiodine _{I 3} ^- complex of the PVA, 600 nm absorption of the polyiodine _{I 5} ^- is said to be due to the complex of the PVA. Regarding the degree of polarization (dichroism) at each wavelength, the degree of polarization _{based on the complex of polyiodine I 5} ⁻ and PVA (dichroism) is the degree of polarization based on the complex of polyiodine I ₃ ⁻ and PVA (dichroism). Higher than dichroism). That is, when trying to make the transmittance at the orthogonal position constant at each wavelength, the transmittance at the parallel position is higher at 600 nm than at 480 nm, and a phenomenon that white is colored yellow when white is displayed has occurred. On the contrary, when trying to make the transmittance at the parallel position constant, the transmittance at the orthogonal position is lower at 600 nm than at 480 nm, so that black is colored blue when displayed in black. When white is yellow when displayed in white, it generally gives the impression that deterioration has progressed, which is not preferable. In addition, when a blue color is displayed when displayed in black, it gives an impression that there is no sense of luxury because it is not clear black. Further, in the iodine-based polarizing plate, it is difficult to control the hue mainly in the vicinity of 550 nm, which has high visual sensitivity, because there is no complex based on the wavelength. As described above, since the degree of polarization (dichroism) of each wavelength is not constant, the wavelength dependence of the degree of polarization has occurred. Further, since there are only two dichroic dyes of 480 nm and 600 nm, which are absorbed by the complex of iodine and PVA, the hue cannot be adjusted with the iodine-based polarizing plate composed of iodine and PVA.

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

Further, an achromatic dyeing type polarizing plate has also been developed (for example, Patent Document 3).

Japanese Patent No. 4281261 Japanese Patent No. 3357803 WO2014 / 162635

However, as can be seen from the examples, the polarizing plate of Patent Document 1 has an a * value of -2 to -1 and an a * value of -2 to -1 in the parallel hue obtained from JIS Z 8729 even if the neutral coefficient (Np) is low. Since the b * value is 2.5 to 4.0, it can be seen that the color is yellowish green when displayed in white. In addition, although the a * value of the hue at the orthogonal position is 0 to 1, the b * value is -1.5 to -4.0, so that the black display becomes a polarizing plate showing blue. ing.
Further, the polarizing film of Patent Document 2 is obtained by setting the a value and the b value in the UCS color space measured using only one polarizing film to an absolute value of 2 or less, and two polarizing films are laminated. It was not possible to express achromatic colors at the same time in both the white and black hues. Further, the average value of the simple substance transmittance of the polarizing film of Patent Document 2 was 31.95% in Example 1 and 31.41% in Example 2, showing low values. As described above, since the polarizing film of Patent Document 2 has low transmittance, it does not have sufficient performance in fields where high transmittance and high contrast are required, particularly in fields such as liquid crystal display devices and organic electroluminescence. .. Further, since the polarizing film of Patent Document 2 uses iodine as the main dichroic dye, the color is obtained after the durability test, particularly after the wet heat durability test (for example, an environment of 85 ° C. and a relative humidity of 85%). The change was large and the durability was inferior.

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

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

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

（式中、Ａｒ_１は置換基を有するフェニル基またはナフチル基を示し、Ｒｒ_１およびＲｒ_２は各々独立に、水素原子、低級アルキル基、低級アルコキシ基、またはスルホ基を有する低級アルコキシ基を示し、Ｘｒ_１は置換基を有してもよいアミノ基または置換基を有してもよいフェニルアミノ基を示す。）

（式中、Ａｇ_１は置換基を有するフェニル基またはナフチル基を示し、Ｒｇ_１は水素原子、低級アルキル基、低級アルコキシ基、またはスルホ基を有する低級アルコキシ基を示し、Ｘｇ_１は置換基を有してもよいアミノ基または置換基を有してもよいフェニルアミノ基を示す。）

（式中、Ａｒ_１、Ｒｒ_１およびＲｒ_２は各々独立に、式（１）で定義した通りであり、Ｘｒ_２は置換基を有してもよいアミノ基、置換基を有してもよいフェニルアミノ基、置換基を有してもよいフェニルアゾ基、置換基を有してもよいベンゾイル基、または、置換基を有してもよいベンゾイルアミノ基を示す。）

（式中、Ａｒ_１およびＲｇ_１は各々独立に、式（２）で定義した通りであり、Ｘｇ_２は置換基を有してもよいアミノ基、置換基を有してもよいフェニルアミノ基、置換基を有してもよいフェニルアゾ基、置換基を有してもよいベンゾイル基、または、置換基を有してもよいベンゾイルアミノ基を示す。）

（式中、Ａｂ_１は置換基を有するフェニル基またはナフチル基を示し、Ｒｂ_１からＲｂ_６は各々独立に、水素原子、低級アルキル基、低級アルコキシ基、またはスルホ基を有する低級アルコキシ基を示し、Ｘｂ_１は置換基を有してもよいアミノ基、置換基を有してもよいフェニルアミノ基、置換基を有してもよいフェニルアゾ基、または置換基を有してもよいナフトトリアゾール基、置換基を有してもよいベンゾイル基、または、置換基を有してもよいベンゾイルアミノ基を示す。）；
［２］ 前記偏光素子２枚を吸収軸方向が互いに平行になるように重ねて測定して求められる４２０ｎｍから４８０ｎｍの平均透過率と、５２０ｎｍから５９０ｎｍの平均透過率との差の絶対値が２．５％以下であり、かつ、５２０ｎｍから５９０ｎｍの平均透過率と、６００ｎｍから６４０ｎｍの平均透過率との差の絶対値が２．０％以下である［１］に記載の偏光素子；
［３］ ＪＩＳ Ｚ ８７８１−４：２０１３に従って自然光の透過率測定時に求められるａ＊値およびｂ＊値の絶対値が、
前記偏光素子単体で、ともに１．０以下であり、
前記偏光素子２枚をその吸収軸方向が互いに平行になるように重ねて配置した状態で、ともに２．０以下である［１］または［２］に記載の偏光素子；
［４］ 前記偏光素子の単体透過率が３５％から４５％であり、
前記偏光素子２枚をその吸収軸方向が互いに平行になるように重ねて配置した状態で求められる５２０ｎｍから５９０ｎｍの平均透過率が２５％から３５％である［１］〜［３］のいずれかに記載の偏光素子；
［５］ 前記式（５）で表されるアゾ化合物が、式（６）で表されるアゾ化合物である［４］に記載の偏光素子；

（式中、Ａｂ_１、Ｒｂ_１からＲｂ_４、およびＸｂ_１は式（５）で定義した通りである。）
［６］ 式（７）で表されるアゾ化合物またはその塩をさらに含有する［１］乃至［５］のいずれかに記載の偏光素子

（式中、Ｒｙ_１およびＲｙ_２は各々独立に、スルホ基、カルボキシ基、ヒドロキシ基、低級アルキル基、または低級アルコキシル基を示し、ｎは１〜３の整数を示す。）；
［７］ 式（３）中、Ｘｒ_２は、置換基を有してもよいアミノ基または置換基を有してもよいフェニルアミノ基を示し、
式（４）中、Ｘｇ_２は、置換基を有してもよいアミノ基または置換基を有してもよいフェニルアミノ基を示す、［１］〜［６］のいずれかに記載の偏光素子；
［８］ 前記偏光素子２枚をその吸収軸方向が互いに直交するように重ねて配置した状態で求められる透過率について、
４２０ｎｍから４８０ｎｍの平均透過率と５２０ｎｍから５９０ｎｍの平均透過率との差の絶対値が０．３％以下であり、かつ、５２０ｎｍから５９０ｎｍの平均透過率と６００ｎｍから６４０ｎｍの平均透過率との差の絶対値が０．３％以下である［１］〜［７］のいずれかに記載の偏光素子；
［９］ 前記偏光素子２枚をその吸収軸方向が互いに直交するように重ねて配置した状態で、ＪＩＳ Ｚ ８７８１−４：２０１３に従って自然光の透過率測定時に求められるａ＊値およびｂ＊値の絶対値が２．０以下である［１］〜［８］のいずれかに記載の偏光素子；
［１０］ 前記偏光素子が、ポリビニルアルコール系樹脂フィルムを基材として含む［１］〜［９］のいずれかに記載の偏光素子；
［１１］ ［１］〜［１０］のいずれかに記載の偏光素子と、前記偏光素子の片面または両面に設けられた透明保護層とを備える偏光板；
［１２］ ［１］〜［１０］のいずれかに記載の偏光素子または［１１］に記載の偏光板を備える液晶表示装置。 As a result of diligent studies to solve the above problems, the present inventor has no wavelength dependence in dichroism due to the formulation of a specific azo compound, and is achromatic in each of the parallel and orthogonal positions, and this It has been found that a polarizing element having a higher degree of polarization can be produced. The present inventor has found for the first time that wavelength independence in the visible light region can be achieved even with high transmittance, and is higher than the ability to realize high-quality paper-like white, commonly known as paper white. We have developed a polarizing element with a degree of polarization. That is, the present invention relates to the following [1] to [12].
[1] (A) The azo compound represented by the formula (1) or a salt thereof and the azo compound represented by the formula (2) or a salt thereof are contained or contained.
(B) Contains an azo compound represented by the formula (3) or a salt thereof, an azo compound represented by the formula (4) or a salt thereof, and an azo compound represented by the formula (5) or a salt thereof. Polarizing element

(In the formula, Ar ₁ represents a phenyl group or a naphthyl group having a substituent, and 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. , Xr ₁ represents an amino group which may have a substituent or a phenylamino group which may have a substituent.)

(In the formula, Ag ₁ represents a phenyl group or a naphthyl group having a substituent, Rg ₁ represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group, and Xg ₁ represents a substituent. Indicates an amino group that may have or a phenylamino group that may have a substituent.)

(In the formula, Ar ₁ , Rr ₁ and Rr ₂ are independently as defined in the formula (1), and Xr ₂ may have an amino group and a substituent which may have a substituent. Indicates a phenylamino group, a phenylazo group which may have a substituent, a benzoyl group which may have a substituent, or a benzoylamino group which may have a substituent.)

(In the formula, Ar ₁ and Rg ₁ are independently defined in the formula (2), and Xg ₂ is an amino group which may have a substituent and a phenylamino group which may have a substituent. , A phenylazo group which may have a substituent, a benzoyl group which may have a substituent, or a benzoylamino group which may have a substituent.)

(In the formula, Ab ₁ represents a phenyl group or a naphthyl group having a substituent, and Rb ₁ to Rb ₆ each independently represent a lower alkoxy group having a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a sulfo group. , Xb ₁ is an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, or a naphthotriazole group which may have a substituent. , A benzoyl group which may have a substituent, or a benzoylamino group which may have a substituent.);
[2] The absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm, which is obtained by stacking the two polarizing elements so as to be parallel to each other in the absorption axis direction, is 2 The polarizing element according to [1], wherein the absolute value of the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 600 nm to 640 nm is 2.0% or less, which is 5.5% or less;
[3] The absolute values of the a * value and b * value obtained when measuring the transmittance of natural light according to JIS Z 8781-4: 2013 are
Both of the polarizing elements alone are 1.0 or less.
The polarizing element according to [1] or [2], wherein the two polarizing elements are stacked and arranged so that their absorption axis directions are parallel to each other, and both are 2.0 or less.
[4] The single transmittance of the polarizing element is 35% to 45%.
Any of [1] to [3], which is obtained in a state where the two polarizing elements are stacked so as to be parallel to each other in the absorption axis direction, and the average transmittance at 520 nm to 590 nm is 25% to 35%. The polarizing element described in the above;
[5] The polarizing element according to [4], wherein the azo compound represented by the formula (5) is an azo compound represented by the formula (6);

(In the equation, Ab ₁ , Rb ₁ to Rb ₄ , and Xb ₁ are as defined in equation (5).)
[6] The polarizing device according to any one of [1] to [5], which further contains an azo compound represented by the formula (7) or a salt thereof.

(In the formula, Ry ₁ and Ry ₂ each independently represent a sulfo group, a carboxy group, a hydroxy group, a lower alkyl group, or a lower alkoxyl group, and n represents an integer of 1 to 3);
[7] In the formula (3), Xr ₂ represents an amino group which may have a substituent or a phenylamino group which may have a substituent.
The polarizing element according to any one of [1] to [6], wherein in the formula (4), Xg _{2 represents an amino group which may have a substituent or a phenylamino group which may have a substituent.} ;
[8] Regarding the transmittance obtained in a state where the two polarizing elements are stacked and arranged so that their absorption axis directions are orthogonal to each other.
The absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is 0.3% or less, and the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 600 nm to 640 nm. The polarizing element according to any one of [1] to [7], wherein the absolute value of is 0.3% or less;
[9] The a * value and b * value obtained when measuring the transmittance of natural light according to JIS Z 8781-4: 2013 with the two polarizing elements stacked so that their absorption axis directions are orthogonal to each other. The polarizing element according to any one of [1] to [8] having an absolute value of 2.0 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 including the polarizing element according to any one of [1] to [10] and a transparent protective layer provided on one side or both sides of the polarizing element;
[12] A liquid crystal display device including the polarizing element according to any one of [1] to [10] or the polarizing plate according to [11].

The present invention is a high-performance achromatic polarizing element having high transmittance and high degree of polarization, which is achromatic in both white display and black display, and particularly exhibits high-quality white color when displayed in white, and an achromatic polarizing element thereof. It is possible to provide an achromatic polarizing plate and a liquid crystal display device using the above.

<Polarizing element>
The polarizing element according to the present invention contains an azo compound represented by the formula (1) or a salt thereof and an azo compound represented by the formula (2) or a salt thereof, or is represented by the formula (3). The azo compound or salt thereof, the azo compound represented by the formula (4) or a salt thereof, and the azo compound represented by the formula (5) or a salt thereof are contained. Preferably, the polarizing element includes these azo compounds or salts thereof, and a substrate on which the azo compounds or salts thereof are adsorbed.

The base material is preferably a film obtained by forming a film of a dichroic dye, particularly a hydrophilic polymer capable of adsorbing an azo compound. The hydrophilic polymer is not particularly limited, and examples thereof include polyvinyl alcohol-based resins, amylose-based resins, starch-based resins, cellulosic resins, and polyacrylate-based resins. The hydrophilic polymer is most preferably a polyvinyl alcohol-based resin or a derivative thereof from the viewpoint of dyeability, processability, crosslinkability and the like of the dichroic dye. A polarizing element can be produced by adsorbing an azo compound or a salt thereof on a base material and subjecting it to an orientation treatment such as stretching.

The polarizing element of the present invention is obtained from the azo compound represented by the formula (1) or a salt thereof, and the azo compound represented by the formula (2) or a salt thereof (the azo compound group of the group A), or the formula. Obtained from the azo compound represented by (3) or a salt thereof, the azo compound represented by the formula (4) or a salt thereof, and the azo compound represented by the formula (5) or a salt thereof (azo compound group of group B). ..

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

In formula (1), Ar ₁ represents a phenyl group having a substituent or a naphthyl group having a substituent.
When Ar ₁ is a phenyl group, it preferably has at least one sulfo group or carboxy group as a substituent thereof. When the phenyl group has two or more substituents, at least one of the substituents is a sulfo group or a carboxy group, and the other substituents are a sulfo group, a carboxy group, a lower alkyl group, a lower alkoxy group and a sulfo group. A lower alkoxy group having a group, a nitro group, a benzoyl group, an amino group, an acetylamino group and a lower alkylamino group substituted amino group are preferable, and more preferably a sulfo group, a methyl group, an ethyl group, a methoxy group, an ethoxy group and a carboxy group. It is a group, a nitro group, a benzoyl group and an amino group, and particularly preferably a sulfo group, a methyl group, a methoxy group, an ethoxy group, a benzoyl group and a carboxy group. As the lower alkoxy group having a sulfo group, linear alkoxy is preferable, and the substituent of the sulfo group is preferably an alkoxy group terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably 3. -Sulfopropoxy group. The number of sulfo groups contained in the phenyl group is preferably 1 or 2, and the substitution position is not particularly limited, 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 Ar ₁ is a naphthyl group having a substituent, it is preferable that it has at least one sulfo group as the substituent, and when it has two or more substituents, at least one of the substituents is a sulfo group. As the other substituent, a sulfo group, a hydroxy group, a carboxy group, and a lower alkoxy group having a sulfo group are preferable. As the lower alkoxy group having a sulfo group, linear alkoxy is preferable, and the substituent of the sulfo group is preferably an alkoxy group terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably 3. -Sulfopropoxy group. When the number of sulfo groups is 2, the positions of the sulfo groups on the naphthyl group are preferably a combination of 4 and 8 positions and a combination of 6 and 8 positions, and more preferably a combination of 6 and 8 positions. When the number of sulfo groups contained in the naphthyl group is 3, the combination of 1, 3 and 6 positions is particularly preferable as the substitution position of the sulfo group.

In the specification of the present application, the "lower" of the lower alkyl group, lower alkoxy group, and lower alkylamino group indicates that the number of carbon atoms is 1 to 4, preferably 1 to 3. Further, in the present specification, the "substituent" includes a hydrogen atom for convenience.

Rr ₁ and Rr ₂ each independently represent a lower alkoxy group having a hydrogen atom, a lower alkyl group, a lower alkoxy group, or 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. As the lower alkoxy group having a sulfo group, a linear alkoxy group is preferable, and the substituent of the sulfo group is preferably an alkoxy group terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, but particularly preferably. It is a 3-sulfopropoxy group. As the replacement position, only the 2nd position, the 5th position, the combination of the 2nd and 5th positions, and the combination of the 3rd and 5th positions are preferable.

Xr ₁ is an amino group which may have a substituent, a phenylamino group which may have a substituent, and preferably a phenylamino group which may have a substituent. The amino group which may have a substituent is preferably one or two substituents selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, an amino group and a lower alkylamino group. It has one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, an amino group, and a lower alkylamino group. It is an amino group. The phenylamino group, which may have a substituent, is preferably one or two selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxyl group, a sulfo group, an amino group, and a lower alkylamino group. A phenylamino group having a substituent, more preferably a phenylamino group having one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, and an amino group. .. In Xr ₁ , the position of the substituent is not particularly limited, but it is particularly preferable that one substituent is at the p-position. As a specific example, in the case of a phenylamino group, the substituent is substituted at the p-position with respect to the amino group. It is preferable that there is a group.

Examples of the method for obtaining the azo compound represented by the formula (1) include the methods described in JP-A-2003-215338, JP-A-9-302250, and Japanese Patent No. 3881175. It is not limited to.

Specific examples of the azo compound represented by the formula (1) include, for example, C.I. I. Examples thereof include Direct Violet 9, and azo compounds described in JP-A-2003-215338, JP-A-9-302250, and Japanese Patent No. 3881175. Further specific examples of the azo compound represented by the formula (1) are shown below in the form of a free acid.

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

In formula (2), Ag ₁ represents a phenyl group having a substituent or a naphthyl group having a substituent. When Ag ₁ is a phenyl group, it preferably has at least one sulfo group or carboxy group as a substituent thereof. When the phenyl group has two or more substituents, at least one of the substituents is a sulfo group or a carboxy group, and the other substituents are a sulfo group, a carboxy group, a lower alkyl group, a lower alkoxy group and a sulfo group. It is preferably a lower alkoxy group having a nitro group, an amino group, an acetylamino group, or a lower alkylamino group substituted amino group, and other substituents are more preferably a sulfo group, a methyl group, an ethyl group, or a methoxy group. It is a group, an ethoxy group, a carboxy group, a nitro group, or an amino group, and particularly preferably a sulfo group, a methyl group, a methoxy group, an ethoxy group, or a carboxy group. As the lower alkoxy group having a sulfo group, linear alkoxy is preferable, and the substituent of the sulfo group is preferably an alkoxy group terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably 3-. It is a sulfopropoxy group. The number of substituents contained in 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 is a naphthyl group having a substituent, it is preferable that Ag 1 has at least one sulfo group as the substituent. When the naphthyl group has two or more substituents, at least one of the substituents is a sulfo group, and the other substituents include a sulfo group, a hydroxy group, a carboxy group, or a lower alkoxy group having a sulfo group. preferable. It is particularly preferable that the naphthyl group has two or more sulfo groups as a substituent. As the lower alkoxy group having a sulfo group, linear alkoxy is preferable, and the substituent of the sulfo group is preferably an alkoxy group terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably 3. -Sulfopropoxy group. When the number of sulfo groups contained in the naphthyl group is 2, the substitution position of the sulfo group is preferably a combination of 4 and 8 positions, a combination of 6 and 8 positions, and more preferably a combination of 6 and 8 positions. When the number of sulfo groups contained in the naphthyl group is 3, the substitution position of the sulfo group is preferably a combination of 1, 3 and 6 positions.

Rg ₁ represents a lower alkoxy group having a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a sulfo group. Preferably, Rg ₁ is a hydrogen atom, a lower alkyl group, or a lower alkoxy group, and more preferably a hydrogen atom, a methyl group, or a methoxy group. Particularly preferably, Rg ₁ is preferably a methyl group or a methoxy group. As the lower alkoxy group having a sulfo group, linear alkoxy is preferable, and the substituent of the sulfo group is preferably an alkoxy group terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably 3-. It is a sulfopropoxy group. Rg ₁ substitution position, 5-position only, although only the 6-position are preferred, particularly preferred, may be substituted in the 5-position.

Xg ₁ represents an amino group which may have a substituent or a phenylamino group which may have a substituent, and is more preferably a phenylamino group. The amino group which may have a substituent is preferably an amino having one or two selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, an amino group, and a lower alkylamino group. It is a group. The phenylamino group, which may have a substituent, is preferably one or two selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxyl group, a sulfo group, an amino group, and a lower alkylamino group. A phenylamino group having a substituent, more preferably a phenylamino group having one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, and an amino group. .. The substitution position is not particularly limited, but it is particularly preferable that one of the substituents is at the p-position with respect to the amino group of the phenylamino group.

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

The azo compound represented by the formula (2) or a salt thereof can be synthesized by the methods described in, for example, Japanese Patent Publication No. 64-5623 and Japanese Patent No. 3378296, but the present invention is not limited thereto.

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

The polarizing element contains a combination of the azo compounds represented by the formulas (1) and (2) of the A group, so that the polarizing element has a higher transmittance and a higher degree of polarization than the conventional achromatic polarizing plate. However, it is possible to realize high-quality paper-like white, commonly known as paper white, when displaying white, and to realize achromatic black, especially high-quality clear black, when displaying black.

Further, the azo compound represented by the formula (3) or a salt thereof, the azo compound represented by the formula (4) or a salt thereof, and the azo compound represented by the formula (5) or a salt thereof (azo compound group of group B). The polarizing element obtained by the above method is also preferable because the polarization characteristics are further improved and a highly reliable polarizing element or a polarizing plate can be obtained.

The azo compound represented by the formula (3) will be described.

In formula (3), Ar ₁ has the same meaning as defined in formula (1), and specifically indicates a phenyl group having a substituent or a naphthyl group having a substituent.
When Ar ₁ is a phenyl group, it preferably has at least one sulfo group or carboxy group as a substituent thereof. When the phenyl group has two or more substituents, at least one of the substituents is a sulfo group or a carboxy group, and the other substituents are a sulfo group, a carboxy group, a lower alkyl group, a lower alkoxy group and a sulfo group. A lower alkoxy group having a group, a nitro group, a benzoyl group, an amino group, an acetylamino group and a lower alkylamino group substituted amino group are preferable, and more preferably a sulfo group, a methyl group, an ethyl group, a methoxy group, an ethoxy group and a carboxy group. It is a group, a nitro group, a benzoyl group and an amino group, and particularly preferably a sulfo group, a methyl group, a methoxy group, an ethoxy group, a benzoyl group and a carboxy group. As the lower alkoxy group having a sulfo group, linear alkoxy is preferable, and the substituent of the sulfo group is preferably an alkoxy group terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably 3. -Sulfopropoxy group. The number of sulfo groups contained in the phenyl group is preferably 1 or 2, and the substitution position is not particularly limited, 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 Ar ₁ is a naphthyl group having a substituent, it is preferable that it has at least one sulfo group as the substituent, and when it has two or more substituents, at least one of the substituents is a sulfo group. As the other substituent, a sulfo group, a hydroxy group, a carboxy group, and a lower alkoxy group having a sulfo group are preferable. As the lower alkoxy group having a sulfo group, linear alkoxy is preferable, and the substituent of the sulfo group is preferably an alkoxy group terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably 3. -Sulfopropoxy group. When the number of sulfo groups is 2, the positions of the sulfo groups on the naphthyl group are preferably a combination of 4 and 8 positions and a combination of 6 and 8 positions, and more preferably a combination of 6 and 8 positions. When the number of sulfo groups contained in the naphthyl group is 3, the combination of 1, 3 and 6 positions is particularly preferable as the substitution position of the sulfo group.

In the specification of the present application, the "lower" of the lower alkyl group, lower alkoxy group, and lower alkylamino group indicates that the number of carbon atoms is 1 to 4, preferably 1 to 3. Further, in the present specification, the "substituent" includes a hydrogen atom for convenience.

Rr ₁ and Rr ₂ have the same meaning as defined in the formula (1), and specifically, each of them independently has a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group. Shown. 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. As the lower alkoxy group having a sulfo group, a linear alkoxy group is preferable, and the substituent of the sulfo group is preferably an alkoxy group terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, but particularly preferably. It is a 3-sulfopropoxy group.

Xr ₂ is an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a benzoyl group which may have a substituent, or It indicates a benzoylamino group which may have a substituent, and is preferably a phenylamino group which may have a substituent. The amino group which may have a substituent is preferably one or two substituents selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, an amino group and a lower alkylamino group. It has one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, an amino group, and a lower alkylamino group. It is an amino group. The phenylamino group, which may have a substituent, is preferably one or two selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxyl group, a sulfo group, an amino group, and a lower alkylamino group. A phenylamino group having a substituent, more preferably a phenylamino group having one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, and an amino group. .. The benzoyl group which may have a substituent is preferably a benzoyl group having one selected from the group consisting of a hydrogen atom, a hydroxy group, a sulfo group, an amino group, and a carboxyethylamino group. The benzoylamino group which may have a substituent is preferably a benzoylamino group having one selected from the group consisting of a hydrogen atom, a hydroxy group, an amino group, and a carboxyethylamino group. The phenylazo group which may have a substituent preferably comprises a group consisting of a hydrogen atom, a hydroxy group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an amino group and a carboxyethylamino group. It is a phenylazo group having 1 to 3 selected. Xr ₂ is preferably a benzoylamino group which may have a substituent and a phenylamino group which may have a substituent, and more preferably a phenylamino group. The position of the substituent is not particularly limited, but it is particularly preferable that one substituent is at the p-position. As a specific example, in the case of a phenylamino group, there is a substituent at the p-position with respect to the amino group. Is preferable.

Examples of the method for obtaining the azo compound represented by the formula (3) include the methods described in JP-A-2003-215338, JP-A-9-302250, and Japanese Patent No. 3881175. It is not limited to.

Specific examples of the azo compound represented by the formula (3) include, for example, C.I. I. Direct Red 81, C.I. I. Direct Red 117, C.I. I. Direct Violet 9 and C.I. I. Examples thereof include azo compounds described in Direct Red 127, JP-A-2003-215338, JP-A-9-302250, and Japanese Patent No. 3881175. Further specific examples of the azo compound represented by the formula (3) are shown below in the form of a free acid.

Next, the compound of the formula (4) will be described.

In formula (4), Ag ₁ has the same meaning as defined in formula (2) , and specifically indicates a phenyl group having a substituent or a naphthyl group having a substituent. When Ag ₁ is a phenyl group, it preferably has at least one sulfo group or carboxy group as a substituent thereof. When the phenyl group has two or more substituents, at least one of the substituents is a sulfo group or a carboxy group, and the other substituents are a sulfo group, a carboxy group, a lower alkyl group, a lower alkoxy group and a sulfo group. It is preferably a lower alkoxy group having a nitro group, an amino group, an acetylamino group, or a lower alkylamino group substituted amino group, and other substituents are more preferably a sulfo group, a methyl group, an ethyl group, or a methoxy group. It is a group, an ethoxy group, a carboxy group, a nitro group, or an amino group, and particularly preferably a sulfo group, a methyl group, a methoxy group, an ethoxy group, or a carboxy group. As the lower alkoxy group having a sulfo group, linear alkoxy is preferable, and the substituent of the sulfo group is preferably an alkoxy group terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably 3-. It is a sulfopropoxy group. The number of substituents contained in 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 is a naphthyl group having a substituent, it is preferable that Ag 1 has at least one sulfo group as the substituent. When the naphthyl group has two or more substituents, at least one of the substituents is a sulfo group, and the other substituents include a sulfo group, a hydroxy group, a carboxy group, or a lower alkoxy group having a sulfo group. preferable. It is particularly preferable that the naphthyl group has two or more sulfo groups as a substituent. As the lower alkoxy group having a sulfo group, linear alkoxy is preferable, and the substituent of the sulfo group is preferably an alkoxy group terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably 3. -Sulfopropoxy group. When the number of sulfo groups contained in the naphthyl group is 2, the substitution position of the sulfo group is preferably a combination of 4 and 8 positions, a combination of 6 and 8 positions, and more preferably a combination of 6 and 8 positions. When the number of sulfo groups contained in the naphthyl group is 3, the substitution position of the sulfo group is preferably a combination of 1, 3 and 6 positions.

Rg ₁ has the same meaning as defined in the formula (2) , and specifically indicates a lower alkoxy group having a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a sulfo group. Preferably, Rg ₁ is a hydrogen atom, a lower alkyl group, or a lower alkoxy group, and more preferably a hydrogen atom, a methyl group, or a methoxy group. Particularly preferably, Rg ₁ is preferably a methyl group or a methoxy group. As the lower alkoxy group having a sulfo group, linear alkoxy is preferable, and the substituent of the sulfo group is preferably an alkoxy group terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably 3-. It is a sulfopropoxy group.

Xg ₂ includes an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a benzoyl group which may have a substituent, and a substituent. Indicates a naphthotriazole group which may have a group or a benzoylamino group which may have a substituent. Xg ₂ is preferably a benzoylamino group which may have a substituent or a phenylamino group which may have a substituent, and more preferably a phenylamino group. The amino group which may have a substituent is preferably an amino having one or two selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, an amino group, and a lower alkylamino group. It is a group. The phenylamino group, which may have a substituent, is preferably one or two selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxyl group, a sulfo group, an amino group, and a lower alkylamino group. A phenylamino group having a substituent, more preferably a phenylamino group having one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, and an amino group. .. The substitution position is not particularly limited, but it is particularly preferable that one of the substituents is at the p-position with respect to the amino group of the phenylamino group. The phenylazo group is preferably selected from the group consisting of a hydrogen atom, a hydroxy group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an amino group, a hydroxyl group and a carboxyethylamino group. It is a phenylazo group having three. The benzoyl group which may have a substituent is preferably a benzoyl group having one substituent selected from the group consisting of a hydrogen atom, a hydroxy group, an amino group, and a carboxyethylamino group. The naphthotriazole group which may have a substituent is preferably 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 carboxy group. A preferred substituent is a sulfo group. The benzoylamino group which may have a substituent is preferably a benzoylamino group having one substituent selected from the group consisting of a hydrogen atom, a hydroxy group, an amino group, and a carboxyethylamino group.

In the polarizing element of the present invention, the content of the azo compound represented by the formula (4) or a salt thereof is 0.01 to 5000 parts by mass with respect to 100 parts by mass of the content of the azo compound of the formula (3). It is preferably 0.1 to 3000 parts by mass.

The azo compound represented by the formula (4) or a salt thereof can be synthesized by the methods described in, for example, Japanese Patent Publication No. 64-5623 and Japanese Patent No. 3378296, but the present invention is not limited thereto.

Specific examples of the azo compound represented by the formula (4) are shown below in the form of a free acid.

Next, the azo compound represented by the formula (5) will be described.

In formula (5), Ab ₁ represents a phenyl group or a naphthyl group having a substituent. When Ab ₁ is a phenyl group, it preferably has at least one sulfo group or carboxy group as its substituent. When the phenyl group has two or more substituents, at least one of the substituents is preferably a sulfo group or a carboxy group, and the other substituents are preferably a sulfo group, a carboxy group or a lower alkyl group. , Lower alkoxy group, lower alkoxy group having sulfo group, nitro group, benzoyl group, amino group, acetylamino group or lower alkylamino group substituted amino group, more preferably sulfo group, methyl group, ethyl group, methoxy. It is a group, an ethoxy group, a carboxy group, a nitro group and an amino group, and particularly preferably a sulfo group, a methyl group, a methoxy group, a benzoyl group and a carboxy group. As the lower alkoxy group having a sulfo group, linear alkoxy is preferable, and the substituent of the sulfo group is preferably an alkoxy group terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably 3-. It is a sulfopropoxy group. The number of substituents contained in 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 Ab ₁ is a naphthyl group having a substituent, it is preferable that Ab 1 has at least one sulfo group as the substituent. When the naphthyl group has two or more substituents, at least one of the substituents is a sulfo group, and the other substituents include a sulfo group, a hydroxy group, a carboxy group, and a lower alkoxy group having a sulfo group. preferable. As the lower alkoxy group having a sulfo group, linear alkoxy is preferable, and the substituent of the sulfo group is preferably an alkoxy group terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably 3-. It is a sulfopropoxy group. When the number of substituents of the sulfo group is 2, the substitution position of the sulfo group in the naphthyl group is preferably a combination of 4 and 8 positions or a combination of 6 and 8 positions, and a combination of 6 and 8 positions is more preferable. When the number of sulfo groups 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 lower alkoxy group having a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a sulfo group. Rb ₁ to Rb ₆ are preferably hydrogen atoms, methyl groups, or methoxy groups, each independently. As the lower alkoxy group having a sulfo group, linear alkoxy is preferable, and the substituent of the sulfo group is preferably an alkoxy group terminal, more preferably a 3-sulfopropoxy group and a 4-sulfobutoxy group, and particularly preferably 3-. It is a sulfopropoxy group.

Xb ₁ includes an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, and a naphthotriazole group which may have a substituent. A benzoyl group which may have a substituent or a benzoylamino group which may have a substituent is shown. Xb ₁ is preferably a benzoylamino group which may have a substituent or a phenylamino group which may have a substituent, and more preferably a phenylamino group. The amino group which may have a substituent is preferably any one or 2 selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxyl group, a sulfo group, an amino group, and a lower alkylamino group. An amino group having one substituent, preferably any one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, an amino group, and a lower alkylamino group. It is an amino group having. The phenylamino group, which may have a substituent, is preferably one or two selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxyl group, a sulfo group, an amino group, and a lower alkylamino group. A phenylamino group having a substituent, more preferably a phenylamino group having one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, and an amino group. .. The phenylazo group which may have a substituent is preferably a group consisting of a hydrogen atom, a hydroxy group, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, an amino group, and a carboxyethylamino group. It is a phenylazo group having 1 to 3 substituents selected from. The naphthotriazole group which may have a substituent is preferably 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 carboxy group. A preferred substituent is a sulfo group. The benzoyl group which may have a substituent is preferably a benzoyl group having one substituent selected from the group consisting of a hydrogen atom, a hydroxy group, a sulfo group and an amino group. The benzoylamino group which may have a substituent is preferably a benzoylamino group having one substituent selected from the group consisting of a hydrogen atom, a hydroxy group, an amino group, and a carboxyethylamino group. The position of the substituent is not particularly limited, but it is particularly preferable that one substituent is at the p-position. As a specific example, in the case of a phenylamino group, there is a substituent at the p-position with respect to the amino group. Is preferable.

The azo compound represented by the formula (5) is preferably an azo compound represented by the formula (6) because the polarization performance of the polarizing element can be improved.

式（６）中、Ａｂ_１、Ｒｂ_１からＲｂ_４、およびＸｂ_１は、式（５）で定義したのと同じ意味を有する。

In formula (6), Ab ₁ , Rb ₁ to Rb ₄ , and Xb ₁ have the same meaning as defined in formula (5).

It is more preferable that the azo compound represented by the formula (6) is an azo compound represented by the formula (8) because the polarization performance of the polarizing element can be further improved.

In formula (8), Ab ₁ , Rb ₂ , Rb ₄ , and Xb ₁ have the same meaning as defined in formula (5).

In the polarizing element of the present invention, the content of the azo compound represented by the formula (5) or a salt thereof is 0.01 to 8000 parts by mass with respect to 100 parts by mass of the content of the azo compound of the formula (3). It is preferably 0.1 to 3000 parts by mass.

The azo compound represented by the formula (5) or a salt thereof can be synthesized by the methods described in, for example, WO2012 / 108169 and WO2012 / 108173.

Specific examples of the azo compound represented by the formula (5) include azo compounds described in WO2012 / 108169, WO2012 / 108173, and the like. Further specific examples of the azo compound represented by the formula (5) are shown below in the form of a free acid.

By containing a combination of azo compounds represented by the formulas (3) to (5), the polarizing element has a higher transmittance and a higher degree of polarization than the conventional achromatic polarizing plate, but displays white. Sometimes it is possible to realize high-quality paper-like white, commonly known as paper white, and when displaying black, it is possible to realize achromatic black, especially high-quality clear black.

The polarizing element according to the present invention containing the azo compound represented by the formula (1) or a salt thereof and the azo compound represented by the formula (2) or a salt thereof (the azo compound group of the group A) is represented by the formula (7). By further containing the azo compound represented by) or a salt thereof, it has performances such as chromaticity a * value and b * value in a preferable range described later, single transmittance, and average transmittance in a specific wavelength band. Can be done. Further, the azo compound represented by the formula (3) or a salt thereof, the azo compound represented by the formula (4) or a salt thereof, and the azo compound represented by the formula (5) or a salt thereof (azo compounds of group B). By further containing the azo compound represented by the formula (7) or a salt thereof, the polarizing element containing (group) also contains the chromaticity a * value and b * value in a preferable range, which will be described later, the single transmission rate, and the specificity. It can have performance such as average transmittance in the wavelength band.

In the formula, Ry ₁ and Ry ₂ are independently sulfo groups, carboxy groups, hydroxy groups, lower alkyl groups, or lower alkoxyl groups, preferably sulfo groups or carboxy groups. n represents an integer of 1 to 3.

In the polarizing element of the present invention, the content of the azo compound represented by the formula (7) or a salt thereof is the content of the azo compound (group A) of the formula (1) or the azo compound (group B) of the formula (3). The amount is preferably 0.01 to 300 parts by mass, and more preferably 0.1 to 200 parts by mass with respect to 100 parts by mass.

The azo compound represented by the formula (7) affects the transmittance at 400 to 500 nm. In the polarizing element, in particular, the transmittance and the degree of polarization (dichroism) on the short wavelength side of 400 to 500 nm affect the blue coloration at the time of black display and the white yellowing at the time of white display. The azo compound represented by the formula (7) suppresses a decrease in the transmittance on the short wavelength side of the parallel position of the polarizing element, improves the polarization characteristics (dichroism) of 400 to 500 nm, and displays white. It is possible to further reduce the blue coloration at the time of yellowing and black display. By further containing the azo compound represented by the formula (7), the polarizing element exhibits a more neutral hue in the range of 35 to 45% of the simple substance transmittance, and is a higher quality paper when displayed in white. It is possible to express such a white color and further improve the degree of polarization.

The azo compound represented by the formula (7) or a salt thereof can be synthesized by the method described in, for example, WO2007 / 138980, but commercially available products can also be obtained.

Specific examples of the azo compound represented by the formula (7) include, for example, C.I. I. Direct Yellow 4, C.I. I. Direct Yellow 12, C.I. I. Direct Yellow 72, and C.I. I. There are, but are not limited to, Direct Orange 39 and azo compounds having a stilbene structure described in WO2007 / 138980 and the like.

Further specific examples of the azo compound represented by the formula (7) are given below. Examples of compounds are represented in the form of free acids.

The azo compounds represented by the formulas (1) to (7) may be in the free form or in the salt form. The salt can be, for example, an alkali metal salt such as a lithium salt, a sodium salt, and a potassium salt, or an organic salt such as an ammonium salt or an alkylamine salt. The salt is preferably a sodium salt.

The polarizing element according to the present invention contains an azo compound represented by the formula (1) or a salt thereof and an azo compound represented by the formula (2) or a salt thereof (compound group of group A), or contains a formula thereof. Contains an azo compound represented by (3) or a salt thereof, an azo compound represented by the formula (4) or a salt thereof, and an azo compound represented by the formula (5) or a salt thereof (compound group of group B). However, it further optionally further contains an azo compound represented by the formula (7). Such a polarizing element can have performances such as chromaticity a * value and b * value in a preferable range, a single transmittance, and an average transmittance in a specific wavelength band, which will be described later, and is more than a conventional achromatic polarizing plate. Can also achieve higher performance.

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

(Transmittance)
The transmittance is the transmittance after luminosity factor correction, which is obtained according to JIS Z 8722: 2009. The transmittance is measured by measuring the spectral transmittance of a measurement sample (for example, a polarizing element or a polarizing plate) at intervals of 5 nm or 10 nm for each wavelength of 400 to 700 nm, and measuring this with a two-degree field of view (C light source). It can be obtained by correcting the visual sensitivity.

(I) Difference in average transmittance between two wavelength bands In the polarizing element of the present invention, it is preferable that the difference in average transmittance between specific wavelength bands is a predetermined value or less. The average transmittance is the average value of the transmittance in a specific wavelength band.

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

The polarizing element of the present invention has a transmittance (hereinafter, "parallel") obtained by measuring in a state where two polarizing elements are stacked so as to be parallel to each other in the absorption axis direction (when displayed in bright light or when displayed in white). The absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is preferably 2.5% or less, more preferably 1.8. % Or less, more preferably 1.5% or less, and particularly preferably 1.0% or less. Further, regarding the parallel transmittance, the absolute value of the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 600 nm to 640 nm is preferably 2.0% or less, more preferably 1.5% or less. , More preferably 1.0% or less. Such a polarizing element can display a high-quality paper-like white color in a parallel position.

Further, the transmittance obtained by measuring in a state where two polarizing elements are stacked so as to be orthogonal to each other in the absorption axis direction (when displayed in black or when displayed in dark) (hereinafter, also referred to as “orthogonal transmittance”). The absolute value of the difference between the average transmittance from 420 nm to 480 nm and the average transmittance from 520 nm to 590 nm is 0.3% or less, and the average transmittance from 520 nm to 590 nm and from 600 nm. The absolute value of the difference from the average transmittance at 640 nm is preferably 0.3% or less. Such a polarizing element can display an achromatic black color at an orthogonal position. Further, regarding the orthogonal position transmittance, the absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is more preferably 0.2% or less, still more preferably 0.1% or less. is there. Regarding the orthogonal position transmittance, the absolute value of the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 600 nm to 640 nm is more preferably 0.2% or less, still more preferably 0.1% or less.

Further, the average transmittances of the single transmittance, the parallel transmittance, and the orthogonal transmittance in each of the wavelength bands of 380 nm to 420 nm, 480 nm to 520 nm, and 640 nm to 780 nm are such that the wavelength bands of 420 nm to 480 nm and 520 nm to 590 nm. When the average transmittance in the range of 600 nm to 640 nm is adjusted as described above, it is less affected by the dye, but it is preferably adjusted to some extent. The difference between the average transmittance of the wavelength band 380 nm to 420 nm and the average transmittance of 420 nm to 480 nm is preferably 15% or less, and the difference between the average transmittance of 480 nm to 520 nm and the average transmittance of 420 nm to 480 nm. Is 15% or less, the difference between the average transmittance of 480 nm to 520 nm and the average transmittance of 520 nm to 590 nm is 15% or less, and the difference between the average transmittance of 640 nm to 780 nm and the average transmittance of 600 nm to 640 nm is 20%. The following is preferable.

(II) Single Transmittance The polarizing element according to the present invention preferably has a single transmittance of 35% to 45%. The single transmittance is the transmittance of one measurement sample (for example, a polarizing element or a polarizing plate) corrected to the visual sensitivity according to JIS Z 8722: 2009. The performance of the polarizing plate is required to have a higher transmittance, but if the single transmittance is 35% to 45%, the brightness can be expressed without discomfort even when used in a display device. The higher the transmittance, the lower the degree of polarization. Therefore, from the viewpoint of the balance with the degree of polarization, the single transmittance is more preferably 36% to 41%, more preferably 37% to 40%. is there. If the single transmittance exceeds 45%, the degree of polarization may decrease, but if the bright transmittance of the polarizing element or a specific polarization performance or contrast is required, even if the single transmittance exceeds 45%. Good.

(III) Average Transmittance in a Specific Wavelength Band The polarizing element preferably has an average transmittance of 25% to 35% in the wavelength band of 520 nm to 590 nm measured in a parallel position. When such a polarizing element is provided in a display device, it can be a clear display device that is bright and has high brightness. The transmittance of the wavelength band from 520 nm to 590 nm is one of the main wavelength bands based on the color matching function used in the calculation when showing a color in JIS Z 8781-4: 2013. In particular, each wavelength band from 520 nm to 590 nm is the wavelength band having the highest visual sensitivity based on the color matching function, and the transmittance in this range is close to the transmittance that can be visually confirmed. Therefore, it is very important to adjust the transmittance in the wavelength band from 520 nm to 590 nm. The average transmittance in the wavelength band of 520 nm to 590 nm measured in the parallel position is more preferably 26% to 33%, still more preferably 27% to 31%. Further, the degree of polarization of the polarizing element at this time is preferably 80% to 100%, more preferably 95% to 100%, and further preferably 99% to 100%. The degree of polarization is preferably high, but the transmittance and transmittance are adjusted to be suitable depending on whether brightness is emphasized or degree of polarization (or contrast) is emphasized in the relationship between degree of polarization and transmittance. can do.

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

In the polarizing element according to the present invention, each of the absolute values of a * -s and b * -s is preferably 1.0 or less, and each of the absolute values of a * -p and b * -p is 2. It is preferably 0 or less. Such a polarizing element is a neutral color by itself, and can display high-quality white when displaying white. The absolute values of a * -p and b * -p of the polarizing element are more preferably 1.5 or less, still more preferably 1.0 or less. Further, in the polarizing element, each of the absolute values of a * -c and b * -c is preferably 2.0 or less, and more preferably 1.0 or less. Such a polarizing element can display achromatic black when displaying black.
Even if there is a difference of 0.5 between the absolute values of the chromaticity a * value and the b * value, humans can perceive the difference in color, and some people may feel the difference in color greatly. Therefore, it is very important to control these values in the polarizing element. In particular, when the absolute values of a * -p, b * -p, a * -c, and b * -c are 1.0 or less, respectively, when white and black are displayed, they are displayed in white. A good polarizing plate can be obtained in which other colors can hardly be confirmed in black. Specifically, it is possible to realize achromaticity in the parallel position, that is, a high-quality paper-like white color, and to realize a high-quality clear black color that is achromatic in the orthogonal position.

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

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

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

(Preparation of original film)
The raw film can be produced by forming a polyvinyl alcohol-based resin. The polyvinyl alcohol-based resin is not particularly limited, and a commercially available one may be used, or one synthesized by a known method may be used. The polyvinyl alcohol-based resin can be obtained, for example, by saponifying a polyvinyl acetate-based resin. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids and the like. The degree of saponification of the polyvinyl alcohol-based resin is usually preferably about 85 to 100 mol%, more preferably 95 mol% or more. The polyvinyl alcohol-based resin may be further modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can also be used. The degree of polymerization of the polyvinyl alcohol-based resin means the viscosity average degree of polymerization, which can be determined by a method well known in the art, and is usually preferably about 1,000 to 10,000, more preferably the degree of polymerization 1, It is about 500 to 6,000.

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

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

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

The azo compound comprises a mixture of azo compounds from Group A consisting of compounds of formulas (1) and (2) or salts thereof, or compounds of formulas (3), (4) and (5). A mixture of the azo compound from Group B or a salt thereof can be used, and the azo compound represented by the formula (7) or a salt thereof can be further used. In addition, the azo compound, which is a dichroic dye exemplified in "Application of Functional Dyes" (CMC Publishing Co., Ltd., 1st edition, supervised by Masahiro Irie, pp. 98-100), is used to polarize the present application. The color may be adjusted by using it to the extent that the performance of the element is not impaired. In addition to using these azo compounds in the form of free acids, salts of the compounds may be used. Such salts are alkali metal salts such as, for example, lithium salts, sodium salts, and potassium salts, or organic salts such as ammonium salts and alkylamine salts, preferably sodium salts.

The dyeing step is not particularly limited as long as it is a method of adsorbing and impregnating the dye on the resin film, but it is preferably performed by immersing the resin film in the dyeing solution, and by applying the dyeing solution to the resin film. You can also do it. 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 preferably adjusted to 30 seconds to 20 minutes, more preferably 1 to 10 minutes.

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

(Washing step 1)
After the dyeing step, a washing step (hereinafter, also referred to as “cleaning step 1”) can be performed before entering the next step. The dyeing and cleaning step 1 is a step of cleaning the dyeing solution adhering to the surface of the resin film in the dyeing step. By performing the washing step 1, it is possible to suppress the transfer of the dye into the liquid to be treated next. In the cleaning step 1, water is generally used as the cleaning liquid. The cleaning is preferably performed by immersing in a cleaning liquid, but cleaning can also be performed by applying the cleaning liquid to a resin film. The washing time is not particularly limited, but is preferably 1 to 300 seconds, more preferably 1 to 60 seconds. The temperature of the cleaning liquid in the cleaning step 1 needs to be a temperature at which the material constituting the resin film (for example, a hydrophilic polymer, here, a polyvinyl alcohol-based resin) does not dissolve. Generally, it is washed at 5 to 40 ° C. However, since there is no problem in performance even if the cleaning step 1 is not performed, the cleaning step can be omitted.

(Step of adding a cross-linking agent and / or a water resistant agent)
After the dyeing step or the washing step 1, a step of adding a cross-linking agent and / or a water resistant agent can be performed. The method of impregnating the resin film with a cross-linking agent and / or a water resistant agent is preferably to immerse the resin film in the treatment solution, but the treatment solution may be applied or applied to the resin film. The treatment solution contains at least one cross-linking agent and / or water resistant agent and a solvent. The temperature of the treatment solution in this step is preferably 5 to 70 ° C, more preferably 5 to 50 ° C. The treatment time in this step is preferably 30 seconds to 6 minutes, more preferably 1 to 5 minutes.

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

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

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

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

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

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

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

In the method for producing a polarizing element, the degree of swelling of the base material in the swelling step, the compounding ratio of each azo compound in the dyeing step, the temperature of the dyeing solution, the pH, the type and concentration of salts such as sodium chloride, glazed glass, and sodium tripolyphosphate, The dyeing time and the stretching ratio in the stretching step are preferably adjusted so that the polarizing element satisfies at least one of the following conditions (i) to (v). It is more preferable to adjust so as to further satisfy the conditions.
(I) Regarding the parallel transmittance, the absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is 2.5 or less, and the average transmittance of 520 nm to 590 nm and 600 nm to 640 nm. The absolute value of the difference from the average transmittance is 2.0 or less.
(Ii) Regarding the orthogonal position transmittance, the absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is 0.3 or less, and the average transmittance of 520 nm to 590 nm and the average of 600 nm to 640 nm. The absolute value of the difference from the transmittance is 0.3 or less.
(Iii) The single transmittance is 35% to 45%.
(Iv) Each of the absolute values of the a * value and the b * value is 1.0 or less for the polarizing element alone, and 2.0 or less for both the parallel positions.
(V) Each of the absolute values of the a * value and the b * value measured at the orthogonal position is 2 or less.
(Vi) With respect to the parallel transmittance, the average transmittance from 520 nm to 590 nm is 25 to 35%.
(Vii) The difference between the average transmittance from 380 nm to 420 nm and the average transmittance from 420 nm to 480 nm is 15% or less, and the difference between the average transmittance from 480 nm to 520 nm and the average transmittance from 420 nm to 480 nm is 15% or less, 480 nm. The difference between the average transmittance from 520 nm to 520 nm and the average transmittance from 520 nm to 590 nm is 15% or less, and / or the difference between the average transmittance from 640 nm to 780 nm and the average transmittance from 600 nm to 640 nm is 20% or less.

By the above method, a polarizing element containing at least a combination of azo compounds represented by the formulas (1) to (3) can be produced. Such a polarizing element expresses a high-quality paper-like white color when two polarizing elements are stacked so as to be parallel to each other in the absorption axis direction, while having a higher transmittance and a higher degree of polarization than before. It is a hue that can be produced and has a neutral color (neutral gray) by itself. Further, the polarizing element exhibits a high-quality achromatic black when two polarizing elements are stacked so as to be orthogonal to each other in the absorption axis direction. Further, the polarizing element has high durability against high temperature and high humidity.

<Polarizer>
The polarizing plate according to the present invention includes a polarizing element and a transparent protective layer provided on one side or both sides of the polarizing element. The transparent protective layer is provided for the purpose of improving the water resistance and handleability of the polarizing element.

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

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

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

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

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

The polarizing element or polarizing plate of the present invention is provided with a protective layer or a functional layer and a transparent support such as glass, crystal, or sapphire, if necessary, and is provided with a liquid crystal projector, a calculator, a clock, a notebook computer, a word processor, a liquid crystal television, or the like. It is applied to polarized lenses, polarized glasses, car navigation systems, and indoor and outdoor measuring instruments and indicators. In particular, the polarizing element or polarizing plate of the present invention is suitably used for a liquid crystal display device, for example, a reflective liquid crystal display device, a transflective liquid crystal display device, an organic electroluminescence, or the like. The liquid crystal display device using the polarizing element or the polarizing plate of the present invention can express high-quality paper-like white and neutral black. Further, the liquid crystal display device is a liquid crystal display device having high durability, high reliability, high contrast in the long term, and high color reproducibility.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

<Example A>
In Example A below, a measurement sample was prepared using the compounds of Group A.
[Example A1]
A polyvinyl alcohol film (VF-PS manufactured by Kuraray Co., Ltd.) having an average degree of polymerization of 2400 with a saponification degree of 99% or more was immersed in warm water at 45 ° C. for 2 minutes, and a swelling treatment was applied to adjust the stretching ratio to 1.30 times. 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 the azo compounds exemplified in Compound Example 1-1 obtained according to Example 1 of Patent No. 4033443. 100 parts by mass, 0.200 parts by mass of the azo compound having the structure of Compound Example 2-8 obtained in accordance with Example 1 of Tokusei No. 01-005623, and Kayarus manufactured by Nippon Kayakusha Co., Ltd. having the structure of the formula (7). The swollen film was immersed in a dyeing solution at 45 ° C. containing 0.14 parts by mass of Supra Orange 2GL for 6 minutes and 00 seconds to allow the film to contain an azo compound. The obtained film was immersed in an aqueous solution at 40 ° C. containing 20 g / l of boric acid (manufactured by Societa Chemica Larderello s.pa.) for 1 minute. The film after immersion was stretched 5.0 times in an aqueous solution at 50 ° C. containing 30.0 g / l of boric acid for 5 minutes. The obtained film was washed by immersing it in water at 25 ° C. for 20 seconds while maintaining its tension. The washed film was dried at 70 ° C. for 9 minutes to obtain a polarizing element. An alkali-treated triacetyl cellulose film (ZRD-manufactured by Fuji Photo Film Co., Ltd.) using polyvinyl alcohol (NH-26 manufactured by Japan Vam & Poval Co., Ltd.) dissolved in water at 4% of this polarizing element as an adhesive. 60) was laminated to obtain a polarizing plate. The obtained polarizing plate maintained the optical performance of the polarizing element, particularly the single transmittance, hue, degree of polarization and the like. This polarizing plate was used as the measurement sample of Example A1.

[Example A2]
In Example A1, the polarizing element and the polarizing element are similarly polarized except that 0.100 parts by mass of the azo compound shown in Compound Example 1-1 is changed to 0.120 parts by mass of the azo compound shown in Compound Example 1-4. A plate was prepared and used as a measurement sample.

[Example A3]
In Example A2, the same applies except that 0.140 parts by mass of Kayarus Super Orange 2GL was changed to 0.095 parts by mass of the azo compound shown in Compound Example 7-2 obtained by the formulation of WO2007 / 138980 Example A1. A polarizing element and a polarizing plate were prepared and used as a measurement sample.

[Example A4]
In Example A1, 0.110 parts by mass of C.I. I. A polarizing element and a polarizing plate were prepared in the same manner as in Example A1 except that Direct Orange 72 was contained in the staining solution, and used as a measurement sample.

[Example A5]
In the same manner as in Example A1, the polarizing element and the polarizing element and the polarizing element and the azo compound having the structure of Compound Example 2-8 were replaced with 0.240 parts by mass of the azo compound described in Compound Example 2-12. A polarizing plate was prepared and used as a measurement sample.

[Comparative Example A1]
In Example A1, 0.100 parts by mass of the azo compound shown in Compound Example 1-1 was added to C.I. I. A polarizing element and a polarizing plate were prepared in the same manner except in place of Direct Red 81, and used as a measurement sample.

[Comparative Example A2]
In Example A1, 0.100 parts by mass of the azo compound shown in Compound Example 1-1 was replaced with the azo compound described in Compound Example III-6 of Japanese Patent No. 3661238, which does not have the structure of the formula (1). In the same manner, a polarizing element and a polarizing plate were prepared and used as measurement samples.

[Comparative Example A3]
In Example A1, 0.100 parts by mass of the azo compound shown in Compound Example 2-8 is described in Patent No. 2012/165223A1 Example 1 which does not have the structure of the formula (2), and 0.450 parts by mass of another azo compound. Instead, the polarizing element and the polarizing plate were prepared in the same manner except that the dye in the dyeing step was adjusted so that the degree of polarization was 99.9 or more, and used as a measurement sample.

[Comparative Example A4]
In Example A1, the permeation is almost the same as that of Example A1 in the same manner as in Example A1 of the present application, except that only the aqueous solution (staining solution) containing the azo compound has the same composition as in Example 1 of Patent Document 3. A polarizing element and a polarizing plate were prepared by incorporating an azo compound so as to have a ratio, and the same was used as a measurement sample.

<Example B>
In Example B below, a measurement sample was prepared using the compounds of Group B.
[Example B1]
A polyvinyl alcohol film (VF-PS manufactured by Kuraray Co., Ltd.) having an average degree of polymerization of 2400 with a saponification degree of 99% or more was immersed in warm water at 45 ° C. for 2 minutes, and a swelling treatment was applied to adjust the stretching ratio to 1.30 times. 2000 parts by mass of water, 2.0 parts by mass of sodium tripolyphosphate, 2.0 parts by mass of anhydrous glass, 0.100 parts by mass of Compound Example 3-1 and 0.130 parts by mass of Compound Example 5-8. Example 4-1 with 0.200 parts by mass and C.I. I. The swollen film was immersed in a stain solution containing 0.14 parts by mass of Direct Orange 39 at 45 ° C. for 15:00 seconds to allow the film to contain an azo compound. The obtained film was immersed in an aqueous solution at 40 ° C. containing 20 g / l of boric acid (manufactured by Societa Chemica Larderello s.pa.) for 1 minute. The film after immersion was stretched 5.0 times in an aqueous solution at 50 ° C. containing 30.0 g / l of boric acid for 5 minutes. The obtained film was washed by immersing it in water at 25 ° C. for 20 seconds while maintaining its tension. The washed film was dried at 70 ° C. for 9 minutes to obtain a polarizing element. An alkali-treated triacetyl cellulose film (ZRD-manufactured by Fuji Photo Film Co., Ltd.) using polyvinyl alcohol (NH-26 manufactured by Japan Vam & Poval Co., Ltd.) dissolved in water at 4% of this polarizing element as an adhesive. 60) was laminated to obtain a polarizing plate. The obtained polarizing plate maintained the optical performance of the polarizing element, particularly the single transmittance, hue, degree of polarization and the like. This polarizing plate was used as the measurement sample of Example B1.

[Example B2]
A polarizing plate was produced in the same manner as in Example B1 except that the time for immersing the swollen film in the dyeing solution at 45 ° C. was changed to 13 minutes and 30 seconds instead of 15 minutes and 00 seconds.

[Example B3]
Instead of the staining solution used in Example B1, 2000 parts by mass of water, 2.0 parts by mass of sodium tripolyphosphate, 2.0 parts by mass of anhydrous glass, 0.100 parts by mass of Compound Example 3-1 and compound. The same as in Example B1 except that a cleaning solution containing 0.115 parts by mass of Example 5-29, 0.200 parts by mass of Compound Example 4-1 and 0.135 parts by mass of Compound Example 7-1 was used. A polarizing plate was produced.

[Example B4]
Instead of the staining solution used in Example B1, 2000 parts by mass of water, 2.0 parts by mass of sodium tripolyphosphate, 2.0 parts by mass of anhydrous glass, 0.100 parts by mass of Compound Example 3-1 and compound. The same as in Example B1 except that a cleaning solution containing 0.090 parts by mass of Example 5-6, 0.200 parts by mass of Compound Example 4-1 and 0.130 parts by mass of Compound Example 7-1 was used. A polarizing plate was produced.

[Example B5]
Instead of the staining solution used in Example B1, 2000 parts by mass of water, 2.0 parts by mass of sodium tripolyphosphate, 2.0 parts by mass of anhydrous glass, 0.100 parts by mass of Compound Example 3-1 and compound. The same as in Example B1 except that a cleaning solution containing 0.120 parts by mass of Example 5-30, 0.200 parts by mass of Compound Example 4-1 and 0.145 parts by mass of Compound Example 7-1 was used. A polarizing plate was produced.

[Example B6]
Instead of the staining solution used in Example B1, 2000 parts by mass of water, 2.0 parts by mass of sodium tripolyphosphate, 2.0 parts by mass of anhydrous glass, 0.100 parts by mass of Compound Example 3-1 and compound. The same as in Example B1 except that a cleaning solution containing 0.115 parts by mass of Example 5-15, 0.200 parts by mass of Compound Example 4-1 and 0.140 parts by mass of Compound Example 7-1 was used. A polarizing plate was produced.

[Example B7]
Instead of the staining solution used in Example B1, 2000 parts by mass of water, 2.0 parts by mass of sodium tripolyphosphate, 2.0 parts by mass of anhydrous glass, 0.100 parts by mass of Compound Example 3-1 and compound. The same as in Example B1 except that a cleaning solution containing 0.120 parts by mass of Example 5-21, 0.200 parts by mass of Compound Example 4-1 and 0.140 parts by mass of Compound Example 7-1 was used. A polarizing plate was produced.

[Example B8]
Instead of the staining solution used in Example B1, 2000 parts by mass of water, 2.0 parts by mass of sodium tripolyphosphate, 2.0 parts by mass of anhydrous glass, 0.100 parts by mass of Compound Example 3-1 and compound. The same as in Example B1 except that a cleaning solution containing 0.115 parts by mass of Example 5-27, 0.200 parts by mass of Compound Example 4-1 and 0.140 parts by mass of Compound Example 7-1 was used. A polarizing plate was produced.

[Example B9]
Same as Example B1 except that 0.208 parts by mass of Compound Example 3-12 (CI Direct Red 81) was contained in the staining solution instead of 0.100 parts by mass of Compound Example 3-1. To prepare a polarizing plate.

[Example B10]
Same as Example B1 except that 0.220 parts by mass of Compound Example 3-11 (CI Direct Red 117) was contained in the staining solution instead of 0.100 parts by mass of Compound Example 3-1. To prepare a polarizing plate.

[Example B11]
A polarizing plate was produced in the same manner as in Example B1 except that 0.141 parts by mass of Compound Example 3-14 was contained in the staining solution instead of 0.100 parts by mass of Compound Example 3-1.

[Example B12]
A polarizing plate was produced in the same manner as in Example B1 except that 0.200 parts by mass of Compound Example 4-16 was contained in the staining solution instead of 0.200 parts by mass of Compound Example 4-1.

[Example B13]
A polarizing plate was produced in the same manner as in Example B1 except that 0.180 parts by mass of Compound Example 4-17 was contained in the staining solution instead of 0.200 parts by mass of Compound Example 4-1.

[Example B14]
A polarizing plate was produced in the same manner as in Example B1 except that 0.095 parts by mass of Compound Example 7-2 was contained in the staining solution instead of 0.140 parts by mass of Compound Example 7-1.

[Example B15]
Instead of 0.140 parts by mass of Compound Example 7-1, 0.135 parts by mass of C.I. I. A polarizing plate was produced in the same manner as in Example B1 except that Direct Yellow 28 was contained in the staining solution.

[Example B16]
Instead of 0.140 parts by mass of Compound Example 7-1, 0.110 parts by mass of C.I. I. A polarizing plate was produced in the same manner as in Example B1 except that Direct Orange 72 was contained in the staining solution.

[Comparative Example B1]
In Example B1, the permeation is almost the same as that of Example B1 in the same manner as in Example B1 of the present application, except that only the aqueous solution (staining solution) containing the azo compound has the same composition as in Example 1 of Patent Document 3. A polarizing plate was prepared by adding an azo compound so as to have a ratio.

[Comparative Example B2]
A high-transmittance dye-based polarizing plate SHC-115 manufactured by Polatechno Co., Ltd., which has a neutral gray color, was obtained and used as a measurement sample.

[Comparative Example B3]
A neutral gray, high-contrast dye-based polarizing plate SHC-128 manufactured by Polatechno Co., Ltd. was obtained and used as a measurement sample.

[Comparative Examples B4 to B9]
According to the production method of Comparative Example B1 of JP-A-2008-06522, the iodine content time was 5 minutes and 30 seconds in Comparative Example B4, 4 minutes and 45 seconds in Comparative Example B5, 4 minutes and 15 seconds in Comparative Example B6, and Comparative Example B7. In 3 minutes and 30 seconds, in Comparative Example B8, 4 minutes and 00 seconds, and in Comparative Example B9, 5 minutes and 15 seconds, an iodine-based polarizing plate containing no azo compound was prepared and used as a measurement sample.

[Comparative Example B10]
An iodine-based polarizing plate SKW-18245P manufactured by Polatechno Co., Ltd., which shows a paper white color in a parallel position, was obtained and used as a measurement sample.

[Comparative Example B11]
A polarizing plate was produced as in Example 1 of JP-A-11-218611 regarding a dye-based polarizing plate.

[Comparative Example B12]
A polarizing plate was produced as in Example 3 of Japanese Patent No. 4162334 regarding a dye-based polarizing plate.

[Comparative Example B13]
A polarizing plate was produced as in Example 1 of Japanese Patent No. 4360100 regarding a dye-based polarizing plate.

[Comparative Example B14]
1.95 parts by mass of C.I., which is an azo compound having the same color and a ureido skeleton, instead of 0.100 parts by mass of Compound Example 3-1. I. Using Direct Red 80, a polarizing plate was produced in the same manner as in Example B1 except that the transmittance at the orthogonal position was adjusted to be substantially constant and the color was adjusted to be black.

[Comparative Example B15]
Instead of 0.100 parts by mass of Compound Example 3-1 a 0.133 parts by mass of C.I. I. Using Direct Red 7, a polarizing plate was produced in the same manner as in Example B1 except that the transmittance at the orthogonal position was designed to be substantially constant and the color was black.

[Comparative Example B16]
0.100 parts by mass of Compound Example 3-1 was added to 0.152 parts by mass of C.I. I. Using Direct Red 45, a polarizing plate was produced in the same manner as in Example B1 except that the transmittance at the orthogonal position was designed to be substantially constant and the color was black.

[Comparative Example B17]
Instead of 0.130 parts by mass of Compound Example 5-8, 0.075 parts by mass of C.I. I. A polarizing plate was produced using Direct Blue 6 in the same manner as in Example B1 except that the transmittance at the orthogonal position was designed to be substantially constant and the color was black.

[Comparative Example B18]
Instead of 0.130 parts by mass of Compound Example 5-8, 0.085 parts by mass of C.I. I. A polarizing plate was produced using Direct Blue 15 in the same manner as in Example B1 except that the transmittance at the orthogonal position was designed to be substantially constant and the color was black.

[Comparative Example B19]
Instead of 0.130 parts by mass of Compound Example 5-8, 0.105 parts by mass of C.I. I. A polarizing plate was produced using Direct Blue 71 in the same manner as in Example B1 except that the transmittance at the orthogonal position was designed to be substantially constant and the color was black.

[Comparative Example B20]
Instead of 0.200 parts by mass of Compound Example 4-1 but 0.5 parts by mass of C.I. I. A polarizing plate was produced using Direct Blue 199 in the same manner as in Example B1 except that the transmittance at the orthogonal position was designed to be substantially constant and the color was black.

[Comparative Example B21]
Instead of 0.200 parts by mass of Compound Example 4-1 but 0.48 parts by mass of C.I. I. Using Direct Blue 218, a polarizing plate was produced in the same manner as in Example B1 except that the transmittance at the orthogonal position was designed to be substantially constant and the color was black.

[Evaluation]
The measurement samples obtained in Examples A1 to A6 and Comparative Examples A1 to A4, and Examples B1 to B16 and Comparative Examples B1 to B21 were evaluated as follows.
(A) Single transmittance Ts, parallel transmittance Tp, and orthogonal transmittance Tc
The single-unit transmittance Ts, parallel-position transmittance Tp, and orthogonal-position transmittance Tc of each measurement sample were measured using a spectrophotometer (“U-4100” manufactured by Hitachi, Ltd.). Here, the simple substance transmittance Ts is the transmittance of each wavelength when the measurement sample is measured by one sheet. The parallel transmittance Tp is the spectral transmittance of each wavelength measured by superimposing two measurement samples so that their absorption axis directions are parallel to each other. The orthogonal position transmittance Tc is a spectral transmittance measured by superimposing two polarizing plates so that their absorption axes are orthogonal to each other. Measurements were made over wavelengths of 400-700 nm.
The average values of the parallel-position transmittance Tp and the orthogonal-position transmittance Tc at 420 to 480 nm, the average values at 520 to 590 nm, and the average values at 600 to 640 nm are obtained and shown in Table 1.

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

(C) Contrast Contrast was determined by calculating the ratio (Yp / Yc) of the parallel-position transmittance and the orthogonal-position transmittance measured using two identical measurement samples. The results are shown in Table 1A and Table 1B.

(D) Absolute values of the difference between the average transmittances of the two wavelength bands Tables 2A and 2B show the average values of the parallel-position transmittance Tp and the orthogonal-position transmittance Tc of each measurement sample at 520 to 590 nm and 420. The absolute value of the difference from the average value at ~ 480 nm and the absolute value of the difference between the average value at 520 to 590 nm and the average value at 600 to 640 nm are shown.

As shown in Tables 1A and 2A, the parallel transmittance Tp of the measurement samples of Examples A1 to A6 had an average value of 25% or more at 520 to 590 nm. Further, the parallel transmittance Tp has an absolute value of the difference between the average value at 420 to 480 nm and the average value at 520 to 590 nm of 1.0% or less, and the average value at 520 to 590 nm and 590 to 590. The absolute value of the difference from the average value at 640 nm was 1.0% or less, both of which were very low values. Further, the orthogonal position transmittance Tc has an absolute value of the difference between the average value at 420 to 480 nm and the average value at 520 to 590 nm of 0.05% or less, and the average transmittance at 520 to 590 nm and 600. The absolute value of the difference from the average value at ~ 640 nm was 0.05% or less, both of which were very low values. Therefore, it was shown that the measurement samples obtained in Examples A1 to A4 had almost constant average transmittance at each wavelength.
On the other hand, in the measurement samples of Comparative Examples A1 to A3, the absolute value of the difference between the average values of the parallel transmittance Tp between the wavelength bands and the average of the orthogonal transmittance Tc between the wavelength bands are shown in Table 2. At least one of the absolute values of the value difference showed a high value.

Further, comparing Examples A1 to A6 having a single transmittance of about 38.5% and Comparative Example A4 which is a similar achromatic polarizing plate, the optical characteristics are orthogonal to the parallel transmittance of Example A2. The transmittance ratio (contrast between parallel transmittance and orthogonal transmittance) was 2734, whereas the contrast of Comparative Example A4 was 317. In addition, Example A1 had a contrast of about 8.6 times that of Comparative Example A1. As described above, the contrast of the measurement sample of Example A1 was significantly improved as compared with the achromatic dye-based polarizing plate of Patent Document 3.

Further, as shown in Tables 1B and 2B, the parallel transmittance Tp of the measurement samples of Examples B1 to B16 had an average value of 25% or more at 520 to 590 nm. Further, the parallel transmittance Tp has an absolute value of the difference between the average value at 420 to 480 nm and the average value at 520 to 590 nm of 1.0% or less, and the average value at 520 to 590 nm and 590 to 590. The absolute value of the difference from the average value at 640 nm was 1.0% or less, both of which were very low values. Further, the orthogonal position transmittance Tc has an absolute value of the difference between the average value at 420 to 480 nm and the average value at 520 to 590 nm of 0.05% or less, and the average transmittance at 520 to 590 nm and 600. The absolute value of the difference from the average value at ~ 640 nm was 0.05% or less, both of which were very low values. Therefore, it was shown that the measurement samples obtained in Examples B1 to B16 had almost constant average transmittance at each wavelength.
On the other hand, in the measurement samples of Comparative Examples B2 to B21, the absolute value of the difference between the average values of the parallel transmittance Tp between the wavelength bands and the average of the orthogonal transmittance Tc between the wavelength bands are shown in Table 2. At least one of the absolute values of the value difference showed a high value.

Comparing Example B1 and Comparative Example B1 having a single transmittance of about 37%, the contrast of Example B1 is 11105, the contrast of Comparative Example B1 is 2219, and Example B1 is about 5 of Comparative Example B1. It had double the contrast. As described above, the measurement sample of Example B1 had improved contrast as compared with the achromatic dye-based polarizing plate of Patent Document 3. Comparing Example B6 and Comparative Example B3, which have a single transmittance of about 39%, the contrast of Example B6 is 6226, the contrast of Comparative Example B3 is 1413, and Example B3 is about 4.4 times. Had a contrast of.

(E) Polarization degree ρy
The degree of polarization ρy of each measurement sample was obtained by substituting the parallel transmittance Yp and the orthogonal transmittance Yc into the following equations. The results are shown in Tables 3A and 3B.
ρy = {(Yp-Yc) / (Yp + Yc)} ^1/2 x 100

(F) Luminous a * value and b * value For each measurement sample, according to JIS Z 8781-4: 2013, when measuring the single transmittance Ts, when measuring the parallel transmittance Tp, and when measuring the orthogonal transmittance Tc, respectively. The chromaticity a * value and b * value in the above were measured. For the measurement, the above spectrophotometer was used, and both the transmitted color and the reflected color were incident from the outdoor side and measured. A C light source was used as the light source. The results are shown in Table 3. Here, a * -s and b * -s, a * -p and b * -p, and a * -c and b * -c are the simple substance transmittance Ts, the parallel position transmittance Tp, and the orthogonal position transmittance Tc. Corresponds to the chromaticity a * value and b * value at the time of measurement.

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

As shown in Table 3A, the measurement samples of Examples A1 to A4 have a single transmittance of 35% or more, a high transmittance, and a high degree of polarization of 99% or more. It was found that white in the parallel position and black in the orthogonal position can be sufficiently expressed. Further, in the measurement samples of Examples A1 to A4, the absolute values of each of a * -s, b * -s, a * -p, a * -c and b * -c are 1.0 or less, and b. The absolute value of * -p was 2.0 or less, which was a very low value. The measurement samples of Examples B1 to B16 expressed a high-quality paper-like white color in the parallel position and a high-quality clear black color in the orthogonal position even when visually observed. On the other hand, in Comparative Examples B2 to B21, at least one of a * -s, b * -s, a * -p, b * -p, a * -c and b * -c shows a high value. When visually observed, it was not achromatic in the parallel or orthogonal position.

As shown in Table 3B, the measurement samples of Examples B1 to B16 had a single transmittance of 35% or more. It was found that the measurement samples of Examples B1 to B16 showed a high degree of polarization of 99% or more while having high transmittance, and could sufficiently express white in the parallel position and black in the orthogonal position. .. Further, in the measurement samples of Examples B1 to B16, the absolute values of each of a * -s, b * -s, a * -p, a * -c and b * -c are 1.0 or less, and b. The absolute value of * -p was 2.0 or less, which was a very low value. The measurement samples of Examples B1 to B16 expressed a high-quality paper-like white color in the parallel position and a high-quality clear black color in the orthogonal position even when visually observed. On the other hand, in Comparative Examples B2 to B21, at least one of a * -s, b * -s, a * -p, b * -p, a * -c and b * -c shows a high value. When visually observed, it was not achromatic in the parallel or orthogonal position.

From the above, the polarizing element of the present invention can express a high-quality paper-like white color in a parallel position while maintaining a high single-unit transmittance and a parallel-position transmittance, and is a neutral color (neutral gray) by itself. ) Is shown to be a hue. Further, it can be seen that the polarizing element of the present invention maintains a high transmittance, exhibits achromaticity at a parallel position, and also has a high degree of polarization. Further, it can be seen that the polarizing element of the present invention makes it possible to obtain a polarizing element showing a high-quality achromatic black at an orthogonal position.

(H) Durability test The measurement samples of Examples B1 to B16 and Comparative Examples B4 to B10 were applied to an environment of 85 ° C. and a relative humidity of 85% RH for 240 hours. As a result, no change in transmittance or hue was observed in the measurement samples of Examples B1 to B16. On the other hand, the measurement samples of Comparative Examples B4 to B10 had a degree of polarization reduced by 10% or more, b * -c was lower than -10, and the apparent color changed to blue. When placed at orthogonal positions, the black color was largely blue.
From this, it can be seen that the liquid crystal display device using the polarizing element or the polarizing plate according to the present invention is a liquid crystal display device having high reliability, high contrast in the long term, and high color reproducibility.

Claims (11)

( B) Contains an azo compound represented by the formula (3) or a salt thereof, an azo compound represented by the formula (4) or a salt thereof, and an azo compound represented by the formula (5) or a salt thereof. Polarizing element.

(In the formula, Ar ₁ represents a phenyl group or a naphthyl group having a substituent , and 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. , Xr ₂ is an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a benzoyl group which may have a substituent, or , Indicates a benzoylamino group which may have a substituent.)

(In the formula, Ag ₁ represents a phenyl group or a naphthyl group having a substituent, Rg ₁ represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group , and Xg ₂ is a substituent. Indicates a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a benzoyl group which may have a substituent, or a benzoylamino group which may have a substituent.)

(In the formula, Ab ₁ represents a phenyl group or a naphthyl group having a substituent, and Rb ₁ to Rb ₆ each independently represent a lower alkoxy group having a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a sulfo group. , Xb ₁ is an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, or a naphthotriazole group which may have a substituent. , A benzoyl group which may have a substituent, or a benzoylamino group which may have a substituent.) The absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm obtained by stacking the two polarizing elements so as to be parallel to each other in the absorption axis direction is 2.5%. The polarizing element according to claim 1, wherein the absolute value of the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 600 nm to 640 nm is 2.0% or less. The absolute values of the a * and b * values obtained when measuring the transmittance of natural light according to JIS Z 8781-4: 2013 are
Both of the polarizing elements alone are 1.0 or less.
The polarizing element according to claim 1 or 2, wherein the two polarizing elements are stacked and arranged so that their absorption axis directions are parallel to each other, and both are 2.0 or less. The single transmittance of the polarizing element is 35% to 45%.
The invention according to any one of claims 1 to 3, wherein the average transmittance of 520 nm to 590 nm obtained in a state where the two polarizing elements are stacked so as to be parallel to each other in the absorption axis direction is 25% to 35%. Polarizing element. The polarizing element according to claim 4, wherein the azo compound represented by the formula (5) is an azo compound represented by the formula (6).

(In the equation, Ab ₁ , Rb ₁ to Rb ₄ , and Xb ₁ are as defined in equation (5).) In formula (3), Xr ₂ represents an amino group which may have a substituent or a phenylamino group which may have a substituent.
The polarizing element according to any one of claims 1 to 5 , wherein in the formula (4), Xg ₂ represents a phenylamino group which may have a substituent. Regarding the transmittance required in a state where the two polarizing elements are stacked and arranged so that their absorption axis directions are orthogonal to each other.
The absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is 0.3% or less, and the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 600 nm to 640 nm. The polarizing element according to any one of claims 1 to 6 , wherein the absolute value of is 0.3% or less. With the two polarizing elements stacked so that their absorption axis directions are orthogonal to each other, the absolute values of the a * value and b * value obtained when measuring the transmittance of natural light according to JIS Z 8781-4: 2013 are The polarizing element according to any one of claims 1 to 7 , which is 2.0 or less. The polarizing element according to any one of claims 1 to 8 , wherein the polarizing element includes a polyvinyl alcohol-based resin film as a base material. A polarizing plate including the polarizing element according to any one of claims 1 to 9 and a transparent protective layer provided on one side or both sides of the polarizing element. A liquid crystal display device including the polarizing element according to any one of claims 1 to 9 or the polarizing plate according to claim 10.