JP2018054921A - Polarization element, polarization plate, and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarization element, a polarization plate, and a liquid crystal display device capable of representing achromatic white color when two polarization elements are superposed so as to be in parallel to each other in the direction of an absorption axis, though having high permeability and high contrast, and capable of representing aromatic black color when the polarization elements are superposed so as to be in parallel to each other in the direction of the absorption axis.SOLUTION: A polarization element of the present invention comprises a base material containing two kinds of azo compounds represented by a formula (1) and a formula (2) respectively in the form of free acid or the base material containing salts of the azo compounds. The luminosity correction single permeability of the polarization element is 35 to 45%, and when the absolute value of avalue and bvalue in the Labcolor system is equal to or less than 1 when the base material is measured alone. When the two base materials 2 are superposed so as to be in parallel to each other in the direction of the absorption axis and measured, any of these values is equal to or less than 2, and when the two base materials are superposed so as to be in parallel to each other and measured, any of these values is equal to or less than 2.SELECTED DRAWING: None

Description

  The present invention relates to a polarizing element, a polarizing plate and a liquid crystal display device containing iodine and an azo compound.

  In general, the polarizing element is produced by adsorbing and orienting iodine or dichroic dye, which is a dichroic dye, on a polyvinyl alcohol resin film. A polarizing plate is manufactured by bonding a protective film made of triacetyl cellulose or the like to at least one surface of the polarizing element via an adhesive layer. The polarizing plate is used for a liquid crystal display device or the like. A polarizing element using iodine as a dichroic dye is called an iodine-based polarizing plate. On the other hand, a polarizing element using a dichroic dye as a dichroic dye is called a dye-based polarizing plate. Among these, the dye-based polarizing plate is characterized by excellent heat resistance, wet heat durability and stability, and high color selectivity by blending. On the other hand, however, there is a problem that the transmittance is low, that is, the contrast is low as compared with an iodine polarizing plate having the same degree of polarization. Therefore, it is desired to develop a polarizing element having high durability, various color selectivity, higher transmittance and high polarization characteristics.

  However, even in the case of a dye-based polarizing plate with various color selectivity, when a conventional polarizing plate is used, a white color is obtained with two sheets stacked so that the absorption axis directions are parallel to each other (parallel position). Even when configured as shown, the white actually tended to be yellowish. Further, even when the two layers are stacked so that the absorption axis directions are orthogonal to each other (orthogonal position), black tends to be bluish even if it is configured to show black. Accordingly, there has been a demand for the development of a polarizing element that exhibits achromatic white color in parallel position and achromatic black color in orthogonal position.

  In order to obtain a polarizing element exhibiting an achromatic color, it is necessary that the transmittance does not depend on the wavelength in either the parallel position or the orthogonal position, and the transmittance is constant at each wavelength. The reason why it is yellowish in the parallel position and bluish in the orthogonal position is that the wavelength dependence of the transmittance differs between the parallel position and the orthogonal position, and the transmittance is not constant at each wavelength.

Here, the wavelength dependence in an iodine type polarizing plate is demonstrated. When polyvinyl alcohol (hereinafter referred to as “PVA”) is used as a base material and iodine is used as a dichroic dye, it generally has absorption around 480 nm and 600 nm. It is said that the absorption at 480 nm is due to a complex of polyiodine I ₃ ⁻ and PVA, and the absorption at 600 nm is due to a complex of polyiodine I ₅ ⁻ and PVA. Further, the degree of polarization at 600 nm based on the complex of polyiodine I ₅ ⁻ and PVA is higher than the degree of polarization at 480 nm based on the complex of polyiodine I ₃ ⁻ and PVA. As a result, when the transmittance at each wavelength is made constant in the orthogonal position, the transmittance at 600 nm is higher than the transmittance at 480 nm in the parallel position, and a phenomenon of yellowing in the parallel position has occurred. On the contrary, when the transmittance at each wavelength is made constant in the parallel position, the transmittance at 600 nm is lower than the transmittance at 480 nm in the orthogonal position, and a phenomenon of blue coloring at the orthogonal position has occurred. Furthermore, since there is no absorption based on 550 nm, which has the highest human visibility, there is a problem that color control is difficult. That is, since the degree of polarization (dichroic ratio) of each wavelength is not constant, wavelength dependency has occurred. In addition, not only when iodine is used as the dichroic dye, but also when an azo compound having dichroism is used, wavelength dependence occurs between the parallel position and the orthogonal position. In general, there is no known dye exhibiting the same hue in parallel and orthogonal positions. Among the azo compounds having generally known dichroism, there are also azo compounds having completely different wavelength dependency between the parallel position and the orthogonal position, such as yellow in the parallel position and blue in the orthogonal position. To do. In addition, as can be seen from the fact that it has polarized light, the sensitivity of light and darkness given to people differs between orthogonal and parallel positions, so even if color correction is performed, color correction suitable for human sensitivity is necessary. It was.

  As described above, it is difficult to create a state where the transmittance at each wavelength is constant between the parallel position and the orthogonal position and has no wavelength dependency. Furthermore, in order to obtain a polarizing element with high transmittance and high contrast, the polarization degree (dichroic ratio) of each wavelength must be constant. Even when a polarizing element is manufactured using one type of dichroic dye, it is difficult to control the transmittance at the parallel position and the orthogonal position, and when a polarizing element is manufactured by blending a plurality of dichroic dyes. It is extremely difficult to precisely control the relationship between the transmittance and dichroism in the parallel position and orthogonal position of each dichroic dye. Therefore, it is very difficult to obtain a polarizing element exhibiting an achromatic color, which cannot be achieved by simply applying the three primary colors. Controlling the transmittance of each wavelength at the parallel position and the orthogonal position to be constant is very difficult because the polarization degree of each wavelength must be the same. Therefore, the prior art has not yet produced a polarizing element having a single transmittance of 35% or more, showing achromatic white in a parallel position, and showing achromatic black in an orthogonal position.

  For example, Patent Literature 1 and Patent Literature 2 disclose methods for improving the hue of a polarizing plate. Specifically, Patent Document 1 discloses a polarizing plate in which the absolute value of the neutral coefficient calculated from the parallel hue and the orthogonal hue is in the range of 0 to 3. Further, in Patent Document 2, the spectral transmittance at a wavelength of 410 to 750 nm is within ± 30% of the average value, and the transmission at a wavelength of 410 to 750 nm when two polarizing films are overlapped and the polarization axes are orthogonal to each other. A polarizing film for antiglare glasses having a rate of 2% or less is disclosed. Further, as a solution of the technical problems in Patent Document 1 and Patent Document 2, Patent Document 3 describes the a * value and the b * value of the hue obtained according to JIS Z 8729, the a * value at the time of measuring the single transmittance. The b * value is within 1 as an absolute value, and the a * value and b * value obtained by measuring the two base materials parallel to the absorption axis direction are within 2 as an absolute value. A polarizing element is disclosed in which the a * value and b * value obtained by measuring the two substrates perpendicular to the absorption axis direction are within 2 as absolute values and the single transmittance is 35% or more. Has been.

Japanese Patent No. 4281261 Japanese Patent No. 3357803 International Publication No. 2014/162633

Functional dye application first edition, CMC Publishing, supervised by Masahiro Irie, p. 98-100

  However, according to the example disclosed in Patent Document 1, even if the neutral coefficient is low, the a * value of the parallel hue obtained from JIS Z 8729 is −1.67 to −1.32, and b *. Since the value is 2.66 to 3.51, it can be seen that it is yellowish green in parallel position. In addition, the a * value of the orthogonal hue is 0.49 to 0.69, but the b * value is −3.40 to −1.81, indicating that the orthogonal hue is blue.

  In addition, the polarizing film disclosed in Patent Document 2 is a polarizing film in which the absolute value of color coordinate values a and b in the UCS color space is 2 or less when measured with one polarizing film. The achromatic color in the parallel position and the orthogonal position where the two sheets were stacked was not achieved. Furthermore, according to the Example currently disclosed by patent document 2, the single transmittance of a polarizing film is as low as 31.95% and 31.41%. Therefore, it has not been applicable to fields requiring high transmittance and high contrast, in particular, fields such as liquid crystal display devices and organic electroluminescence.

  Patent Document 3 solves the technical problems in Patent Document 1 and Patent Document 2, but further improvement in performance is required as a polarizing element that exhibits an achromatic color in a parallel position and an orthogonal position.

  Therefore, the present invention has been made in view of the above circumstances, and has an achromatic white color when two polarizing elements are stacked so that their absorption axis directions are parallel to each other while having high transmittance and high contrast. It is an object of the present invention to provide a polarizing element, a polarizing plate, and a liquid crystal display device that can express achromatic black when two polarizing elements are stacked so that the absorption axis directions are orthogonal to each other.

  As a result of intensive studies to solve the above problems, the inventor has a high degree of polarization and a high transmittance, while making the transmittance constant in each of the parallel position and the orthogonal position to eliminate the wavelength dependence, and further to each wavelength. In order to make the degree of polarization (dichroic ratio) between the parallel and orthogonal positions constant, it has been newly found that it can be achieved only by containing iodine and two kinds of specific azo compounds. As a result, a polarizing element that exhibits achromatic color in both parallel and orthogonal positions while having high transmittance and high contrast has been developed.

（式中、Ａｒ_１は置換基を有してもよいフェニル基又は置換基を有してもよいナフチル基を示し、Ｒｒ_１又はＲｒ_２は各々独立に、水素原子、低級アルキル基、低級アルコキシ基又はスルホ基を有する低級アルコキシ基のいずれかを示し、Ｘｒ_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、置換基を有してもよいベンゾイル基又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は置換基を有してもよいフェニル基又は置換基を有してもよいナフチル基を示し、Ｒｂ_１乃至Ｒｂ_６は各々独立に、水素原子、低級アルキル基、低級アルコキシ基又はスルホ基を有する低級アルコキシ基のいずれかを示し、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、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又は置換基を有してもよいベンゾイルアミノ基を示す。）
（２）偏光度が９９％以上であることを特徴とする（１）に記載の偏光素子。
（３）前記偏光素子の吸収軸方向に対して光の振動方向が直交するように絶対偏光光を照射して測定した各波長の透過率を第１透過率、前記偏光素子の吸収軸方向に対して光の振動方向が平行となるように絶対偏光光を照射して測定した各波長の透過率を第２透過率としたとき、５５０ｎｍ〜６００ｎｍにおける第１透過率の平均値と４００ｎｍ〜４６０ｎｍにおける第１透過率の平均値との差が４％以下であり、かつ、６００ｎｍ〜６７０ｎｍにおける第１透過率の平均値と５５０ｎｍ〜６００ｎｍにおける第１透過率の平均値との差が３％以下であり、５５０ｎｍ〜６００ｎｍにおける第２透過率の平均値と４００ｎｍ〜４６０ｎｍにおける第２透過率の平均値との差が１％以下であり、かつ、６００ｎｍ〜６７０ｎｍにおける第２透過率の平均値と５５０ｎｍ〜６００ｎｍにおける第２透過率の平均値との差が１％以下であることを特徴とする、（１）又は（２）に記載の偏光素子。
（４）前記式（１）におけるＸｒ_１が、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又は置換基を有してもよいベンゾイルアミノ基である、（１）から（３）のいずれかに記載の偏光素子。
（５）前記式（２）で表されるアゾ化合物が、式（３）で表されるアゾ化合物であることを特徴とする（１）から（４）のいずれかに記載の偏光素子。

（式中、Ａｂ_１、Ｒｂ_１乃至Ｒｂ_４、及び、Ｘｂ_１は、式（２）に記載されるものと同じものを示す。）
（６）前記基材が、ポリビニルアルコール系樹脂フィルムであることを特徴とする、（１）から（５）のいずれかに記載の偏光素子。
（７）（１）から（６）のいずれかに記載の偏光素子と、前記偏光素子の少なくとも一方の面に形成した透明保護層とを備えることを特徴とする偏光板。
（８）（１）から（６）のいずれかに記載の偏光素子又は（７）に記載の偏光板を有する液晶表示装置。 That is, the gist configuration of the present invention is as follows.
(1) It consists of a substrate containing two kinds of azo compounds represented by formula (1) and formula (2) or their salts in the form of iodine and free acid, and has a visibility corrected single transmittance. 35 to 45%, and the absolute value of the a ^* value and b ^* value in the L ^* a ^* b ^* color system is 1 or less when the base material is measured alone, and the base material When the two sheets were measured with the absorption axis directions being parallel to each other, both were 2 or less, and when the two substrates were measured with the absorption axis directions being perpendicular to each other, both were 2 The polarizing element characterized by the following.

(In the formula, Ar ₁ represents a phenyl group which may have a substituent or a naphthyl group which may have a substituent, and Rr ₁ or Rr ₂ each independently represents a hydrogen atom, a lower alkyl group or a lower alkoxy group. Xr ₁ represents an amino group which may have a substituent, a phenylamino group which may have a substituent, or a phenylazo which may have a substituent A benzoyl group which may have a group, a substituent or a benzoylamino group which may have a substituent.)

(In the formula, Ab ₁ represents a phenyl group which may have a substituent or a naphthyl group which may have a substituent, and Rb _{1 to} Rb ₆ each independently represents a hydrogen atom, a lower alkyl group or a lower alkoxy group. Xb ₁ represents an amino group which may have a substituent, a phenylamino group which may have a substituent, or a phenylazo which may have a substituent A naphthotriazole group optionally having a substituent, a benzoyl group optionally having a substituent, or a benzoylamino group optionally having a substituent.
(2) The polarizing element according to (1), wherein the degree of polarization is 99% or more.
(3) Transmittance of each wavelength measured by irradiating absolute polarized light so that the vibration direction of light is orthogonal to the absorption axis direction of the polarizing element is defined as the first transmittance and the absorption axis direction of the polarizing element. On the other hand, when the transmittance of each wavelength measured by irradiating absolute polarized light so that the vibration direction of light is parallel is the second transmittance, the average value of the first transmittance at 550 nm to 600 nm and 400 nm to 460 nm. The difference between the average value of the first transmittance at 4 nm and below is 4% or less, and the difference between the average value of the first transmittance at 600 nm to 670 nm and the average value of the first transmittance at 550 nm to 600 nm is 3% or less The difference between the average value of the second transmittance at 550 nm to 600 nm and the average value of the second transmittance at 400 nm to 460 nm is 1% or less, and the second transmission at 600 nm to 670 nm. Wherein the difference between the average value of the second transmission rate in the average value and 550nm~600nm is 1% or less, the polarization element according to (1) or (2).
(4) Xr ₁ in the formula (1) is an amino group that may have a substituent, a phenylamino group that may have a substituent, or a benzoylamino group that may have a substituent, The polarizing element according to any one of (1) to (3).
(5) The polarizing element according to any one of (1) to (4), wherein the azo compound represented by the formula (2) is an azo compound represented by the formula (3).

(In the formula, Ab ₁ , Rb _{1 to} Rb ₄ , and Xb ₁ are the same as those described in Formula (2).)
(6) The polarizing element according to any one of (1) to (5), wherein the substrate is a polyvinyl alcohol-based resin film.
(7) A polarizing plate comprising the polarizing element according to any one of (1) to (6) and a transparent protective layer formed on at least one surface of the polarizing element.
(8) A liquid crystal display device having the polarizing element according to any one of (1) to (6) or the polarizing plate according to (7).

  The polarizing element of the present invention can express achromatic white when two polarizing elements are stacked so that the absorption axis directions thereof are parallel to each other, while having high transmittance and high contrast, and the polarizing element 2 When the sheets are stacked so that the absorption axis directions are orthogonal to each other, an achromatic black color can be expressed. Moreover, the polarizing element of this invention can be used for a polarizing plate and a liquid crystal display device.

[Polarizing element]
The polarizing element of the present invention is composed of a base material containing iodine and two kinds of azo compounds represented by the formula (1) and the formula (2) in the form of a free acid or a salt thereof, and corrects visibility. The single transmittance is 35 to 45%, and the absolute value of the a ^* value and b ^* value in the L ^* a ^* b ^* color system is 1 or less when the substrate is measured alone. When two substrates are measured with the absorption axis directions being parallel to each other, both are 2 or less, and when two substrates are measured with the absorption axis directions being orthogonal to each other, both are 2 or less. Hereinafter, the polarizing element of the present invention will be described in detail.

(Base material)
The polarizing element of the present invention is composed of a base material containing iodine and two kinds of azo compounds represented by the formula (1) and the formula (2) in the form of a free acid or salts thereof. The base material is not particularly limited as long as it can contain two kinds of azo compounds represented by formula (1) and formula (2) in the form of iodine and free acid, or salts thereof. For example, the molded object shape | molded from a hydrophilic polymer is mentioned. Examples of the hydrophilic polymer include polyvinyl alcohol resins, amylose resins, starch resins, cellulose resins, polyacrylate resins, and the like. When the dichroic dye is contained in the substrate, a polyvinyl alcohol-based resin is most preferable as the substrate from the viewpoints of processability, dyeability, crosslinkability, and the like. Although the shape of a base material is not specifically limited, It is preferable that it is a film form.

(Iodine)
In the polarizing element of the present invention, when the base material contains iodine and two kinds of specific azo compounds, the transmittance correction single transmittance is 35 to 45%, and a in the L ^* a ^* b ^* color system the absolute value of ^* and b ^* values are, when the substrate was measured alone, either 1 or less, when measured two material groups overlapped so that the absorption axis direction are parallel to each other, either Is also 2 or less, and it can be achieved that both of the two substrates are 2 or less when measured with the absorption axis directions being perpendicular to each other. When iodine is contained in the base material, it is difficult to dissolve in the solvent only with iodine, and it is difficult to impregnate the base material. Therefore, potassium iodide, ammonium iodide, copper iodide, sodium iodide, calcium iodide, cobalt iodide, In general, an iodide such as zinc iodide and a chloride such as sodium chloride, lithium chloride and potassium chloride are contained together with iodine.

(Azo compound)
First, the azo compound represented by the formula (1) will be described.

In formula (1), Ar ₁ represents an optionally substituted phenyl group or naphthyl group, and Rr ₁ or Rr ₂ each independently represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a sulfo group. Xr ₁ represents an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, or a substituent. The benzoyl group which may have or the benzoylamino group which may have a substituent is shown. In the claims and specification of the present application, “may have a substituent” means that a case where no substituent is present is included. For example, “an optionally substituted phenyl group” includes an unsubstituted mere phenyl group and a phenyl group having a substituent. In addition, “lower” in the lower alkyl group and the lower alkoxy group means 1 to 4 carbon atoms, and preferably 1 to 3 carbon atoms.

Ar ₁ represents a phenyl group or naphthyl group which may have a substituent. The phenyl group which may have a substituent is preferably a phenyl group having at least one sulfo group or carboxy group. 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, 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. As other substituents, a sulfo group, a methyl group, an ethyl group, a methoxy group, an ethoxy group, a carboxy group, a nitro group, and an amino group are more preferable, and a sulfo group, a methyl group, a methoxy group, an ethoxy group, and a carboxy group are particularly preferable. It is a group. The lower alkoxy group having a sulfo group is preferably a linear alkoxy group, and the substitution position of the sulfo group is preferably an alkoxy group terminal. Specifically, a 3-sulfopropoxy group and a 4-sulfobutoxy group are preferable, and a 3-sulfopropoxy group is particularly preferable. The phenyl group which may have a substituent preferably has one or two substituents, and the substitution position is not particularly limited, but only the 4-position, a combination of 2-position and 4-position, 3- A combination of a position and a 5-position is preferred.

  The naphthyl group which may have a substituent is preferably a naphthyl group having at least one sulfo group. When the naphthyl group has two or more substituents, at least one of the substituents is a sulfo group, and the other substituents are a lower alkoxy group having a sulfo group, a hydroxy group, a carboxy group, or a sulfo group. Is preferred. The lower alkoxy group having a sulfo group is preferably a linear alkoxy group, and the substitution position of the sulfo group is preferably an alkoxy group terminal. Specifically, a 3-sulfopropoxy group and a 4-sulfobutoxy group are preferable, and a 3-sulfopropoxy group is particularly preferable. When the naphthyl group has two sulfo groups, the 4-position and 8-position, the 6-position and 8-position combination are preferred as the substitution position of the sulfo group, and the 6-position and 8-position combination is particularly preferred. When the naphthyl group has three sulfo groups, the combination of the 1-position, 3-position and 6-position is particularly preferable as the substitution position of the sulfo group.

Xr ₁ is an amino group that may have a substituent, a phenylamino group that may have a substituent, a phenylazo group that may have a substituent, a benzoyl group that may have a substituent, or a substituent. A benzoylamino group which may have The amino group which may have a substituent is an amino having any one or two substituents selected from the group consisting of a lower alkyl group, a lower alkoxy group, a sulfo group, an amino group, and a lower alkylamino group. A group, preferably an amino group having 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. Moreover, the phenylamino group which may have a substituent has an unsubstituted phenylamino group, or any one or two of a methyl group, a methoxy group, a sulfo group, an amino group, and a lower alkylamino group. A phenylamino group is preferred. The phenylazo group which may have a substituent is an unsubstituted phenylazo group, or a phenylazo group having 1 to 3 of any one of a hydroxy group, a lower alkyl group, a lower alkoxy group, an amino group and a carboxyethylamino group. It is preferably a group. The benzoyl group which may have a substituent is preferably an unsubstituted benzoyl group or a benzoyl group having any one of a hydroxyl group, an amino group, a carboxyl group, a sulfo group and a carboxyethylamino group. The benzoylamino group which may have a substituent is preferably an unsubstituted benzoylamino group or a benzoylamino group having any one of a hydroxy group, an amino group and a carboxyethylamino group. More preferably, they are a phenylamino group which may have a substituent and a benzoylamino group which may have a substituent. Particularly preferred is a phenylamino group which may have a substituent. Although the substitution position is not particularly limited, the p-position is particularly preferred when there is one substituent.

Rr ₁ or Rr ₂ each independently represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group. Preferably they are a hydrogen atom, a lower alkyl group, and a lower alkoxy group, More preferably, they are a hydrogen atom, a methyl group, and a methoxy group. The lower alkoxy group having a sulfo group is preferably a linear alkoxy group, and the substitution position of the sulfo group is preferably an alkoxy group terminal. Specifically, a 3-sulfopropoxy group and a 4-sulfobutoxy group are preferable, and a 3-sulfopropoxy group is particularly preferable.

  Specific examples of the azo compound represented by the formula (1) include C.I. I. Direct Red 81, C.I. I. Direct Red 117, C.I. I. Direct Violet 9, C.I. I. Examples thereof include azo compounds described in Direct Red 127, Japanese Patent Application Laid-Open No. 2003-215338, Japanese Patent Application Laid-Open No. 9-302250, Japanese Patent No. 3881175, and the like. More specifically, examples of the azo compound represented by the formula (1) are shown below in the form of a free acid.

[化合物例２]

[化合物例３]

[化合物例４]

[化合物例５]

[化合物例６]

[化合物例７]

[化合物例８]

[化合物例９]

[化合物例１０]

[化合物例１１]

[化合物例１２]

[化合物例１３]

[Compound Example 1]

[Compound Example 2]

[Compound Example 3]

[Compound Example 4]

[Compound Example 5]

[Compound Example 6]

[Compound Example 7]

[Compound Example 8]

[Compound Example 9]

[Compound Example 10]

[Compound Example 11]

[Compound Example 12]

[Compound Example 13]

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

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

In Formula (2), Ab ₁ represents a phenyl group or naphthyl group which may have a substituent, and Rb _{1 to} Rb ₆ each independently represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a sulfo group. Xb ₁ represents an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, or a substituent. The benzoylamino group which may have a benzoyl group which may have or a substituent is shown.

Ab ₁ represents a phenyl group or a naphthyl group which may have a substituent. The phenyl group which may have a substituent is preferably a phenyl group having at least one sulfo group or carboxy group. 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, 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. As other substituents, a sulfo group, a methyl group, an ethyl group, a methoxy group, an ethoxy group, a carboxy group, a nitro group, and an amino group are more preferable, and a sulfo group, a methyl group, a methoxy group, an ethoxy group, and a carboxy group are particularly preferable. It is a group. The lower alkoxy group having a sulfo group is preferably a linear alkoxy group, and the substitution position of the sulfo group is preferably an alkoxy group terminal. Specifically, a 3-sulfopropoxy group and a 4-sulfobutoxy group are preferable, and a 3-sulfopropoxy group is particularly preferable. The phenyl group which may have a substituent preferably has one or two substituents, and the substitution position is not particularly limited, but only the 4-position, a combination of 2-position and 4-position, 3- A combination of a position and a 5-position is preferred.

  The naphthyl group which may have a substituent is preferably a naphthyl group having at least one sulfo group. When the naphthyl group has two or more substituents, at least one of the substituents is a sulfo group, and the other substituents are a lower alkoxy group having a sulfo group, a hydroxy group, a carboxy group, or a sulfo group. Is preferred. The lower alkoxy group having a sulfo group is preferably a linear alkoxy group, and the substitution position of the sulfo group is preferably an alkoxy group terminal. Specifically, a 3-sulfopropoxy group and a 4-sulfobutoxy group are preferable, and a 3-sulfopropoxy group is particularly preferable. When the naphthyl group has two sulfo groups, the 4-position and 8-position, the 6-position and 8-position combination are preferred as the substitution position of the sulfo group, and the 6-position and 8-position combination is particularly preferred. When the naphthyl group has three sulfo groups, the combination of the 1-position, 3-position and 6-position is particularly preferable as the substitution position of the sulfo group.

Xb ₁ represents an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a benzoyl group which may have a substituent, or a substituent. A benzoylamino group which may have A benzoyl group which may have a substituent or a benzoylamino group which may have a substituent is shown. The amino group which may have a substituent is an unsubstituted amino group or an amino group having any one or two of a methyl group, a methoxy group, a sulfo group, an amino group and a lower alkylamino group. It is preferable. Moreover, the phenylamino group which may have a substituent has an unsubstituted phenylamino group, or any one or two of a methyl group, a methoxy group, a sulfo group, an amino group, and a lower alkylamino group. A phenylamino group is preferred. The phenylazo group which may have a substituent is an unsubstituted phenylazo group, or a phenylazo group having 1 to 3 of any one of a hydroxy group, a lower alkyl group, a lower alkoxy group, an amino group and a carboxyethylamino group. It is preferably a group. The benzoyl group which may have a substituent is preferably an unsubstituted benzoyl group or a benzoyl group having any one of a hydroxyl group, an amino group, a carboxyl group, a sulfo group and a carboxyethylamino group. The benzoylamino group which may have a substituent is preferably an unsubstituted benzoylamino group or a benzoylamino group having any one of a hydroxy group, an amino group and a carboxyethylamino group. More preferably, they are a phenylamino group which may have a substituent and a benzoylamino group which may have a substituent. Particularly preferred is a phenylamino group which may have a substituent. Although the substitution position is not particularly limited, the p-position is particularly preferred when there is one substituent.

Rb _{1 to} Rb ₆ each independently represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group. Preferably they are a hydrogen atom, a lower alkyl group, and a lower alkoxy group, More preferably, they are a hydrogen atom, a methyl group, and a methoxy group. The lower alkoxy group having a sulfo group is preferably a linear alkoxy group, and the substitution position of the sulfo group is preferably an alkoxy group terminal. Specifically, a 3-sulfopropoxy group and a 4-sulfobutoxy group are preferable, and a 3-sulfopropoxy group is particularly preferable.

In particular, when the compound represented by the formula (2) is an azo compound represented by the formula (3), the polarizing performance of the polarizing element or polarizing plate of the present invention is further improved. In the formula, Ab ₁ , Rb _{1 to} Rb ₄ , and Xb ₁ are the same as those described in the formula (2).

Moreover, when the compound represented by Formula (2) is an azo compound represented by Formula (4), the polarizing performance of the polarizing element or polarizing plate of the present invention is further improved. In the formula, Ab ₁ , Rb ₂ , Rb ₄ , and Xb ₁ are the same as those described in the formula (2).

  Next, specific examples of the azo compound represented by the formula (2), the formula (3), or the formula (4) will be given. Specific examples include azo compounds described in International Publication Nos. 2012/108169 and 2012/108173. More specifically, examples of the azo compound represented by the formula (2), the formula (3) or the formula (4) are shown below in the form of a free acid.

[化合物例１５]

[化合物例１６]

[化合物例１７]

[化合物例１８]

[化合物例１９]

[化合物例２０]

[化合物例２１]

[化合物例２２]

[化合物例２３]

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[化合物例２７]

[化合物例２８]

[化合物例２９]

[化合物例３０]

[化合物例３１]

[化合物例３２]

[化合物例３３]

[化合物例３４]

[化合物例３５]

[化合物例３６]

[化合物例３７]

[化合物例３８]

[化合物例３９]

[化合物例４０]

[化合物例４１]

[Compound Example 14]

[Compound Example 15]

[Compound Example 16]

[Compound Example 17]

[Compound Example 18]

[Compound Example 19]

[Compound Example 20]

[Compound Example 21]

[Compound Example 22]

[Compound Example 23]

[Compound Example 24]

[Compound Example 25]

[Compound Example 26]

[Compound Example 27]

[Compound Example 28]

[Compound Example 29]

[Compound Example 30]

[Compound Example 31]

[Compound Example 32]

[Compound Example 33]

[Compound Example 34]

[Compound Example 35]

[Compound Example 36]

[Compound Example 37]

[Compound Example 38]

[Compound Example 39]

[Compound Example 40]

[Compound Example 41]

  Examples of the method for obtaining the azo compound represented by the formula (2), the formula (3), or the formula (4) include methods described in International Publication Nos. 2012/108169 and 2012/108173. However, it is not limited to these.

  The polarizing element of the present invention may contain other azo compounds other than the azo compounds represented by the formulas (1) and (2) as color correction to the extent that the performance of the present invention is not impaired. As other azo compounds to be contained, those having high dichroism are particularly preferable. For example, an azo compound such as C.I. I. Direct. Yellow 12, C.I. I. Direct Yellow 28, C.I. I. Direct. Yellow44, C.I. I. Direct. Orange 26, C.I. I. Direct. Orange 39, C.I. I. Direct. Orange 107, C.I. I. Direct. Red2, C.I. I. Direct. Red31, C.I. I. Direct. Red 79, C.I. I. Direct. Red247, C.I. I. Direct. Green 80, C.I. I. Direct. Green 59, and azo compounds described in JP-B No. 64-5623, JP-A No. 3-12606, JP-A No. 2001-33627, JP-A No. 2002-296417, and JP-A No. 60-156759 Etc. In particular, an azo compound having a phenyl J acid in a trisazo structure can be suitably used. In particular, an azo compound described in JP-A-3-12606 is represented by formula (1) in the form of iodine and free acid. And it is suitable to use for a polarizing element with two types of azo compounds each represented by Formula (2), or those salts. Other azo compounds can be used as free acid, alkali metal salt (for example, sodium salt, potassium salt, lithium salt), ammonium salt, or amine salt. However, other azo compounds are not limited to these, and azo compounds having a known dichroism can be used. By including other azo compounds in the form of a free acid, a salt thereof, or a copper complex salt thereof, optical characteristics are particularly improved. Other azo compounds may be used alone or in combination.

(Visibility corrected single transmittance)
The polarizing element of the present invention has a visibility corrected single transmittance of 35 to 45%. If the transmittance correction single transmittance of the polarizing element is 35%, brightness can be expressed even if it is used in a liquid crystal display device. The visibility corrected single transmittance is preferably 38% or more, more preferably 39% or more, and further preferably 40% or more. The upper limit of the visibility corrected single transmittance is 45%. If the single transmittance for correcting the visibility is more than 45%, the degree of polarization is remarkably lowered and the contrast is lowered, which is not suitable.

  The visibility corrected single transmittance is a single transmittance obtained by performing visibility correction with a 2 ° field of view (C light source). Visibility-corrected single transmittance is calculated for each wavelength of 400 to 700 nm for each measurement sample (for example, a polarizing element or polarizing plate), and further, a 2 ° field of view (C light source) ) Can be obtained by correcting the visibility.

(A ^* value and b ^* value)
In the polarizing element of the present invention, the absolute values of the a ^* value and the b ^* value in the L ^* a ^* b ^* color system are both 1 or less when the base material is measured alone, and two base materials Are both 2 or less when measured so that the absorption axis directions are parallel to each other, and both are 2 or less when two substrates are measured so that the absorption axis directions are orthogonal to each other. .

The L ^* a ^* b ^* color system is an object color display method defined by the International Commission on Illumination (abbreviated as CIE). This display method is also adopted in JIS Z 8781-4: 2013. In the present invention, the a ^* value and b ^* value in the L ^* a ^* b ^* color system are calculated according to JIS Z 8781-4: 2013. Hereinafter, the a ^* value and the b ^* value obtained when measured with one polarizing element (single unit) are referred to as “a ^* -s” and “b ^* -s”. In addition, the a ^* value and the b ^* value when two polarizing elements are measured so that the absorption axis directions are parallel to each other are referred to as “a ^* −p” and “b ^* −p”. The a ^* value and b ^* value when two polarizing elements are measured so that the absorption axis directions are orthogonal to each other are referred to as “a ^* −c” and “b ^* −c”.

In the polarizing element of the present invention, absolute values of a ^* -s and b ^* -s are 1 or less, absolute values of a ^* -p and b ^* -p are 2 or less, and a ^* -c and b ^*. The absolute value of -c is 2 or less. Thereby, an achromatic color is shown in the parallel position and the orthogonal position. Preferably, the absolute values of a ^* -p and b ^* -p are 1.5 or less, and the absolute values of a ^* -c and b ^* -c are 1.5 or less. More preferably, the absolute values of a ^* -p and b ^* -p are 1.0 or less, and the absolute values of a ^* -c and b ^* -c are 1.0 or less. It is very important to control a ^* and b ^* , because even if there is only a difference of 0.5 as the absolute values of a ^* and b ^* , one can feel the difference in color. In particular, if the absolute values of a ^* -p, b ^* -p, a ^* -c, and b ^* -c are all 1.0 or less, people are colored in parallel and orthogonal positions. It can not be felt, and it becomes a good polarizing element.

(Degree of polarization)
The polarizing element of the present invention preferably has a degree of polarization of 99% or more. If the degree of polarization of the polarizing element is 99% or more, the polarizing function can be expressed even when used in a liquid crystal display device. The degree of polarization is preferably 99.9% or more, more preferably 99.95% or more.

(First transmittance and second transmittance)
Visibility corrected single transmittance is 35 to 45%, and the absolute value of the a ^* value and b ^* value in the L ^* a ^* b ^* color system is 1 or less when the substrate is measured alone. When the two base materials are measured so that the absorption axis directions are parallel to each other, both are 2 or less, and when the two base materials are measured so that the absorption axis directions are orthogonal to each other, In order to obtain a polarizing element that is 2 or less, it is preferable to control the transmittance of each wavelength.

  Specifically, the transmittance of each wavelength measured by irradiating absolute polarized light so that the vibration direction of the light is orthogonal to the absorption axis direction of the polarizing element is the first transmittance and the absorption axis direction of the polarizing element. When the transmittance of each wavelength measured by irradiating absolute polarized light so that the vibration direction of light is parallel is the second transmittance, the average value of the first transmittance at 550 nm to 600 nm and the wavelength at 400 nm to 460 nm The difference from the average value of the first transmittance is 4% or less, and the difference between the average value of the first transmittance at 600 nm to 670 nm and the average value of the first transmittance at 550 nm to 600 nm is 3% or less. Yes, the difference between the average value of the second transmittance at 550 nm to 600 nm and the average value of the second transmittance at 400 nm to 460 nm is 1% or less, and the second transmittance at 600 nm to 670 nm And the difference between the average value of the second transmission rate in average value and 550nm~600nm is 1% or less. More preferably, the difference between the average value of the first transmittance at 550 nm to 600 nm and the average value of the first transmittance at 400 nm to 460 nm is 3.5% or less, and the first transmittance at 600 nm to 670 nm The difference between the average value and the average value of the first transmittance at 550 nm to 600 nm is 2.5% or less. More preferably, the difference between the average value of the first transmittance at 550 nm to 600 nm and the average value of the first transmittance at 400 nm to 460 nm is 3% or less, and the average value of the absolute parallel transmittance at 600 nm to 670 nm And the average absolute transmissivity at 550 nm to 600 nm is 2% or less. Absolutely polarized light means polarized light that has passed through a polarizing plate having a degree of polarization of approximately 100% when irradiated from a standard light source, and means approximately 100% polarized light. .

[Production method of polarizing element]
Hereinafter, a specific method for manufacturing a polarizing element will be described using a polyvinyl alcohol-based resin film as an example of the substrate. The polarizing element includes, for example, production of a polyvinyl alcohol resin, production of a raw film, swelling treatment, dyeing treatment, first washing treatment, treatment containing a crosslinking agent and / or a water resistance agent, stretching treatment, and second washing treatment. It is manufactured by performing a drying process in order. Note that some of these processes can be omitted.

(Manufacture of polyvinyl alcohol resin)
The manufacturing method of a polyvinyl alcohol-type resin is not specifically limited, A well-known method is employable. The polyvinyl alcohol resin can be obtained, for example, by saponifying a polyvinyl acetate 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 copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The saponification degree of the polyvinyl alcohol resin is usually about 85 to 100 mol%, preferably 95 mol% or more. This polyvinyl alcohol-based resin may be further modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. Moreover, the polymerization degree of a polyvinyl alcohol-type resin means a viscosity average polymerization degree, and can be calculated | required by a well-known method in the said technical field. The degree of polymerization is usually about 1,000 to 10,000, preferably about 1,500 to 6,000.

(Preparation of raw film)
Next, a polyvinyl alcohol-based resin is formed into a raw film. The method for forming the polyvinyl alcohol-based resin into a film is not particularly limited, and a known method can be employed. The raw film may contain glycerin, ethylene glycol, propylene glycol, low molecular weight polyethylene glycol or the like as a plasticizer. The content of the plasticizer is 5 to 20% by weight in the raw film, and preferably 8 to 15% by weight. Although the film thickness of a raw film is not specifically limited, It is preferable that it is about 5 micrometers-150 micrometers, More preferably, it is about 10 micrometers-100 micrometers.

(Swelling treatment)
The raw film thus obtained is then subjected to a swelling treatment. The swelling treatment is performed by immersing the raw film in a solution at 20 to 50 ° C. for 30 seconds to 10 minutes. The solution is preferably an aqueous solution. The draw ratio is preferably adjusted to 1.00 to 1.50 times, more preferably 1.10 to 1.35 times. Since swelling also occurs in a dyeing process, which will be described later, this swelling process may be omitted when the time for producing the polarizing element is shortened.

(Dyeing process)
A dyeing process is performed after the swelling process. The dyeing treatment is a treatment for dyeing the film after the swelling treatment with iodine and an azo compound represented by formula (1) and formula (2) or a salt thereof in the form of a free acid. The dyeing with iodine is performed, for example, by immersing the film after the swelling treatment in a dyeing solution containing iodine and iodide. Although it does not specifically limit as iodide, For example, potassium iodide, ammonium iodide, cobalt iodide, zinc iodide etc. are mentioned. The iodine concentration in the dyeing solution is preferably 0.0001% to 0.5% by weight, more preferably 0.001% to 0.4% by weight, and still more preferably 0.0001% by weight. ~ 8% by weight.

  The dyeing with the azo compounds represented by the formulas (1) and (2) in the form of the free acid or their salts can be performed by, for example, treating the film after swelling treatment with the formulas (1) and (1) in the form of the free acid. (2) It is carried out by immersing in a dyeing solution containing an azo compound represented by each or a salt thereof.

  The solution temperature in the dyeing treatment is preferably 5 to 60 ° C, more preferably 20 to 50 ° C, and particularly preferably 35 to 50 ° C. Although the time to immerse in a solution can be adjusted moderately, 30 seconds-20 minutes are preferable and 1-10 minutes are more preferable. The dyeing solution is preferably an aqueous solution. The dyeing method is preferably a method of immersing in a dyeing solution, but a method of applying the dyeing solution to the film after the swelling treatment can also be adopted. The dyeing solution may contain sodium carbonate, sodium bicarbonate, sodium chloride, sodium sulfate, anhydrous sodium sulfate, sodium tripolyphosphate and the like as a dyeing assistant. The content of the dyeing assistant can be arbitrarily adjusted depending on the time and temperature depending on the dyeability of the dichroic dye, but is preferably 0 to 5% by weight, more preferably 0.1 to 2% by weight.

  The staining with iodine and the staining with the azo compound may be performed at the same time. However, the staining with the azo compound is performed after the staining with the iodine, or the staining with the iodine is performed after the staining with the azo compound. It is preferable from the viewpoint of management and productivity. The azo compound represented by the formula (1) and the formula (2) in the form of a free acid may be used as a free acid or a salt. Examples of the salt include alkali metal salts such as lithium salt, sodium salt, and potassium salt, or ammonium salt and alkylamine salt. Preferably, it is a sodium salt.

(First cleaning process)
After the dyeing process, a cleaning process (hereinafter referred to as “first cleaning process”) can be performed before the next process. The first cleaning process is a process of cleaning the dyeing solution attached to the film surface by the dyeing process. By performing the first cleaning process, it is possible to prevent the dye from being mixed into the solution used in the next process. In the first cleaning process, water is generally used as a cleaning liquid. The washing method is preferably a method of immersing the dyed film in the washing liquid, but a method of applying the washing liquid to the dyed film can also be adopted. 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 first cleaning process needs to be a temperature at which the film after the dyeing process does not dissolve. Generally, it is washed at 5 to 40 ° C. However, the first cleaning process may be omitted because there is no problem in performance without performing the first cleaning process.

(Treatment containing a crosslinking agent and / or a water resistance agent)
After the first cleaning treatment, a treatment containing a crosslinking agent and / or a water resistance-imparting agent can be performed. Examples of the crosslinking agent include boron compounds such as boric acid, borax or ammonium borate, polyvalent aldehydes such as glyoxal or glutaraldehyde, polyisocyanate compounds such as biuret type, isocyanurate type or block type, titanium oxy Examples include titanium compounds such as sulfate, and other examples include ethylene glycol glycidyl ether and polyamide epichlorohydrin. Examples of the water-proofing agent include succinic peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, ammonium chloride, and magnesium chloride. Of these, boric acid is most preferred. Only one type of cross-linking agent or water-proofing agent may be used, or a plurality thereof may be used in combination.

  A method of immersing the film after the first cleaning treatment in a solution containing a cross-linking agent and / or a water-resistant agent is preferable, but a solution containing a cross-linking agent and / or a water-proofing agent is included in the film after the first cleaning treatment. It is also possible to employ a method of applying The solution is preferably an aqueous solution. The content of the crosslinking agent and / or the water resistance-imparting agent in the solution is preferably 0.1 to 6.0% by weight and more preferably 1.0 to 4.0% by weight when boric acid is taken as an example. 5-70 degreeC is preferable and, as for the temperature of a solution, 5-50 degreeC is more preferable. The treatment time is preferably 30 seconds to 6 minutes, and more preferably 1 to 5 minutes. However, it is not essential to contain a cross-linking agent and / or a water-resistant agent. If it is desired to shorten the time, this processing may be omitted when the cross-linking treatment or the water resistance treatment is unnecessary.

(Extension process)
After the treatment for containing a crosslinking agent and / or a water resistance agent is performed, a stretching treatment is performed. The stretching process is a process of stretching the film uniaxially. The stretching method may be either a wet stretching method or a dry stretching method. The draw ratio is 3 times or more, preferably 5 to 7 times.

  In the case of the dry stretching method, when the stretching heating medium is an air medium, the temperature of the air medium is preferably room temperature to 180 ° C. Moreover, it is preferable to process in the atmosphere of humidity 20-95% RH. Examples of the heating method include an inter-roll zone stretching method, a roll heating stretching method, a pressure stretching method, an infrared heating stretching method, and the like, but the stretching method is not limited. The film can be stretched in one stage, but can also be performed by multistage stretching of two or more stages.

  In the case of the wet stretching method, stretching is performed in water, a water-soluble organic solvent, or a mixed solution thereof. The film after the first washing treatment is preferably stretched while being immersed in a solution containing a crosslinking agent and / or a water resistance agent. Examples of the crosslinking agent and waterproofing agent include those described above. The content of the crosslinking agent and / or the water resistance-imparting agent in the solution is preferably 0.5 to 15% by weight and more preferably 2.0 to 8.0% by weight when boric acid is taken as an example. The draw ratio is preferably 2-8 times, more preferably 5-7 times. The temperature of the solution is preferably 40 to 60 ° C, more preferably 45 to 58 ° C. The stretching time is usually 30 seconds to 20 minutes, but 2 to 5 minutes is more preferable. The film can be stretched in one stage, but can also be performed by multistage stretching of two or more stages.

(Second cleaning process)
After performing the stretching treatment, a crosslinking agent and / or a water-resistant agent may be deposited on the film surface or foreign matter may adhere to the film surface. Therefore, a washing treatment for washing the film surface (hereinafter referred to as “second washing treatment”). Can be performed). The cleaning method is preferably a method of immersing the stretched film in a cleaning solution, but a method of applying a cleaning solution to the stretched film can also be employed. The cleaning process can be performed in one stage, and the multi-stage process of two or more stages can be performed. The washing time is preferably 1 second to 5 minutes. Although the temperature of a washing | cleaning liquid is not specifically limited, Usually, 5-50 degreeC, Preferably it is 10-40 degreeC.

  In addition, as a solvent used by the treatment so far, for example, water, dimethyl sulfoxide, N-methylpyrrolidone, methanol, ethanol, propanol, isopropyl alcohol, glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol or Examples thereof include, but are not limited to, alcohols such as trimethylolpropane, and amines such as ethylenediamine or diethylenetriamine. A mixture of one or more of these solvents can also be used. The most preferred solvent is water.

(Drying process)
After the second cleaning process, a drying process for drying the film is performed. The drying process can be performed by natural drying. In order to further increase the drying efficiency, the surface may be compressed using a roll, the moisture on the surface may be removed by an air knife or a water-absorbing roll, or air drying may be performed. The drying temperature is preferably 20 to 100 ° C, more preferably 60 to 100 ° C. The drying time is preferably 30 seconds to 20 minutes, more preferably 5 to 10 minutes.

It consists of a substrate containing two kinds of azo compounds represented by formula (1) and formula (2) in the form of iodine and free acid, respectively, or salts thereof in the above-described manner, and the visibility correction simple substance transmission The rate is 35 to 45%, and the absolute values of the a ^* value and b ^* value in the L ^* a ^* b ^* color system are both 1 or less when the substrate is measured alone. When two sheets are measured so that the absorption axis directions are parallel to each other, both are 2 or less, and when two substrates are measured so that the absorption axis directions are orthogonal to each other, both are 2 or less. A polarizing element can be obtained.

[Polarizer]
The polarizing plate of the present invention includes a polarizing element and a transparent protective layer formed on at least one surface of the polarizing element, that is, one or both surfaces. A transparent protective layer can be provided on at least one surface of the polarizing element by applying a polymer to at least one surface of the polarizing element, followed by drying or heat treatment. In addition, a polymer formed into a film is used as a transparent protective layer, and after the transparent protective layer is bonded to at least one surface of the polarizing element, it is transparent on at least one surface of the polarizing element by drying or heat treatment. A protective layer can be provided.

  The polymer forming the transparent protective layer is preferably a transparent polymer having high mechanical strength and good thermal stability. Examples of such polymers include cyclic polyolefin resins having a cyclic olefin as a monomer, such as cellulose acetate resins such as triacetyl cellulose and diacetyl cellulose, acrylic resins, polyvinyl chloride resins, nylon resins, polyester resins, polyarylate resins, and norbornene. , Polyethylene, polypropylene, cycloolefin polymer resin, polyolefin having a norbornene skeleton or a copolymer thereof, and a resin having an imide group and / or an amide group in the main chain or side chain. The polymer forming the transparent protective layer may be a liquid crystal polymer. The thickness of the transparent protective layer is, for example, about 0.5 μm to 200 μm.

  An adhesive is required to bond the transparent protective layer to at least one surface of the polarizing element. Although it does not specifically limit as an adhesive agent, The adhesive agent which has polyvinyl alcohol as a main component is preferable. Examples of the polyvinyl alcohol-based adhesive include, but are not limited to, Gohsenol NH-26 (manufactured by Nippon Synthetic Chemical Co., Ltd.), EXEVAL RS-2117 (manufactured by Kuraray Co., Ltd.), and the like. A crosslinking agent and / or a waterproofing agent can be mixed in the polyvinyl alcohol-based adhesive. The polyvinyl alcohol-based adhesive may contain a maleic anhydride and isobutylene copolymer or a modified product thereof. Examples of the copolymer of maleic anhydride and isobutylene include isoban # 18 (manufactured by Kuraray Co., Ltd.) and isoban # 04 (manufactured by Kuraray Co., Ltd.). Examples of the ammonia-modified maleic anhydride-isobutylene copolymer include isoban # 104 (manufactured by Kuraray Co., Ltd.), isoban # 110 (manufactured by Kuraray Co., Ltd.), and the imidized maleic anhydride-isobutylene copolymer include isoban # 304 (manufactured by Kuraray Co., Ltd.) and isoban # 310 (manufactured by Kuraray Co., Ltd.). ). As the crosslinking agent, a water-soluble polyfunctional epoxy compound can be used. Examples of the water-soluble polyfunctional epoxy compound include polyglycerol polyglycidyl ether (Denacol EX-521 (manufactured by Nagase Chemtech)), 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane (TETRAD-C). (Mitsubishi Gas Chemical Co., Ltd.)). Also, known adhesives such as urethane adhesives, acrylic adhesives, and epoxy adhesives can be used. Further, for the purpose of improving the adhesive strength of the adhesive or improving the water resistance, additives such as zinc compounds, chlorides, iodides and the like can be simultaneously contained at a concentration of about 0.1 to 10% by weight.

  When the polarizing plate is bonded to a display device such as a liquid crystal or organic electroluminescence, for example, various functional layers for improving the viewing angle and / or contrast, and a layer having brightness enhancement are formed on the surface that will be the non-exposed surface later. Can be provided. In order to bond the polarizing plate to these layers and the display device, an adhesive is preferably used.

  In addition, when the polarizing plate is bonded to a display device such as a liquid crystal or organic electroluminescence, various known functional layers such as an antireflection layer, an antiglare layer, and a hard coat layer are provided on the surface to be an exposed surface later. Can do. A coating method is preferable for producing the layer having various functions, but a film having the function can be bonded through an adhesive or a pressure-sensitive adhesive. Moreover, various functional layers are layers which control a phase difference, for example.

The polarizing plate of the present invention has the same optical characteristics as the polarizing element. That is, the absolute values of the a ^* value and b ^* value in the L ^* a ^* b ^* color system are both 1 or less when the polarizing plate is measured alone, and the two polarizing plates have an absorption axis direction. Both are 2 or less when measured so as to be parallel to each other, and both are 2 or less when measured with two polarizing plates stacked so that the absorption axis directions are orthogonal to each other. Thereby, an achromatic color is shown in the parallel position and the orthogonal position.

[Liquid Crystal Display]
The polarizing element or polarizing plate of the present invention can be used for a liquid crystal display device. The liquid crystal display device using the polarizing element or the polarizing plate of the present invention becomes a liquid crystal display device having high reliability, long-term high contrast, and high color reproducibility.

  The polarizing element or polarizing plate of the present invention is provided with a protective layer or functional layer, a support, etc. as necessary, and includes a liquid crystal projector, a calculator, a watch, a notebook computer, a word processor, a liquid crystal television, a polarizing lens, polarizing glasses, and car navigation. , And indoor and outdoor measuring instruments and displays. In particular, it is effectively used in reflective liquid crystal display devices, transflective liquid crystal display devices, organic electroluminescence, and the like.

  The polarizing plate of the present invention may have a support on at least one surface. Since a support body is bonded together with a polarizing plate, what has a plane part is preferable. Examples of the support include a molded product made of an inorganic material such as glass, quartz, and sapphire, and an organic plastic plate such as acrylic and polycarbonate. Since it is an optical use, the support is preferably a glass molded product. Examples of the glass molded product include a glass plate, a lens, and a prism (for example, a triangular prism and a cubic prism). Examples of the glass material include soda glass and borosilicate glass. A lens attached with a polarizing plate can be used as a condenser lens with a polarizing plate in a liquid crystal projector. Also, a prism attached with a polarizing plate can be used as a polarizing beam splitter with a polarizing plate or a dichroic prism with a polarizing plate in a liquid crystal projector. Further, a polarizing plate may be attached to the liquid crystal cell. The thickness and size of the support are not particularly limited.

  In order to further improve the single transmittance of the polarizing plate provided with glass, it is preferable to provide an antireflection layer on at least one surface of the glass or polarizing plate. For example, after applying a transparent adhesive (pressure-sensitive adhesive) to the flat surface of the support, the polarizing plate of the present invention is applied to the coated surface. Moreover, after apply | coating a transparent adhesive (adhesion) agent to a polarizing plate, you may stick a support body to this application | coating surface. The adhesive (adhesive) agent used here is preferably, for example, an acrylic ester-based one. In addition, when using this polarizing plate as an elliptical polarizing plate, it is normal to stick a retardation layer to a support body, but you may stick a polarizing plate to a support body.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by these.

[Preparation of measurement sample]
Example 1
A polyvinyl alcohol film (VF-PS manufactured by Kuraray Co., Ltd.) having an average polymerization degree of 2400 having a saponification degree of 99% or more was immersed in warm water at 45 ° C. for 2 minutes, and subjected to a swelling treatment so that the draw ratio was 1.30 times. Next, 1500 parts by weight of water, 1.5 parts by weight of sodium tripolyphosphate, 1.5 parts by weight of anhydrous sodium sulfate, 0.07 parts by weight of Compound Example 1 having the structure of formula (1), Compound Example 21 having the structure (2) 0.95 parts by weight was immersed in an aqueous solution adjusted to 45 ° C. for 3 minutes and 30 seconds. Next, boric acid (manufactured by Societa chimica lardrello sp.) 28.6 g / l, iodine (manufactured by Junsei Kagaku) 0.25 g / l, potassium iodide (manufactured by Junsei Kagaku) It was immersed in an aqueous solution containing 17.7 g / l and ammonium iodide (manufactured by Junsei Co., Ltd.) 1.0 g / l at 30 ° C. for 2 minutes. Next, the obtained film was stretched in an aqueous solution containing 30.0 g / l of boric acid for 5 minutes at 50 so that the stretch ratio was 5.0 times. Next, an immersion treatment was performed at 30 ° C. for 20 seconds in an aqueous solution containing 20 g / l of potassium iodide while maintaining the tension state of the obtained film. Next, the obtained film was dried at 70 ° C. for 9 minutes to obtain a polarizing element. A polarizing plate was obtained by laminating an alkali-treated triacetyl cellulose film (ZRD-60 manufactured by Fuji Photo Film Co., Ltd.) with a polyvinyl alcohol adhesive on the obtained polarizing element. The obtained polarizing plate maintained the optical characteristics of the polarizing element. The polarizing plate was used as a measurement sample of Example 1.

(Example 2)
A measurement sample was prepared in the same manner as in Example 1 except that 0.95 part by weight of Compound Example 21 described in Example 1 was changed to 0.76 part by weight of Compound Example 14 having the structure of Formula (2). .

(Example 3)
Except for changing 0.95 parts by weight of Compound Example 21 described in Example 1 to 0.84 parts by weight of the dye shown in (19) of International Publication No. 2012/108169 having the structure of the formula (2) A measurement sample was prepared in the same manner as in Example 1.

Example 4
A measurement sample was prepared in the same manner as in Example 1, except that 0.95 part by weight of Compound Example 21 described in Example 1 was changed to 0.92 part by weight of Compound Example 19 having the structure of Formula (2). .

(Example 5)
Except for changing 0.95 parts by weight of Compound Example 21 described in Example 1 to 1.0 part by weight of the dye having the structure of the formula (2) shown in (44) of International Publication No. 2012/108169. A measurement sample was prepared in the same manner as in Example 1.

(Example 6)
A measurement sample was prepared in the same manner as in Example 1 except that 0.95 part by weight of Compound Example 21 described in Example 1 was changed to 0.90 part by weight of Compound Example 28 having the structure of Formula (2). .

(Example 7)
A measurement sample was prepared in the same manner as in Example 1 except that 0.95 part by weight of Compound Example 21 described in Example 1 was changed to 0.77 part by weight of Compound Example 34 having the structure of Formula (2). .

(Example 8)
Except that 0.95 part by weight of Compound Example 21 described in Example 1 was changed to 0.81 part by weight of the dye shown in (50) of International Publication No. 2012/108173 having the structure of the formula (2) A measurement sample was prepared in the same manner as in Example 1.

Example 9
Compound Example 1 described in Example 1 0.07 part by weight of C.I having the structure of the formula (1) I. A measurement sample was prepared in the same manner as in Example 1 except that 0.88 part by weight of Direct Red 81 was used.

(Example 10)
Compound Example 1 described in Example 1 0.07 part by weight of C.I having the structure of the formula (1) I. A measurement sample was prepared in the same manner as in Example 1 except that the amount was changed to 0.65 parts by weight of Direct Red 117.

(Example 11)
Except that 0.07 part by weight of Compound Example 1 described in Example 1 was changed to 0.60 part by weight of the dye shown in IIIa-6 of Japanese Patent No. 3661238 having the structure of Formula (1). A measurement sample was prepared in the same manner as in Example 1.

(Comparative Example 1)
In accordance with the production method shown in Comparative Example 1 of Japanese Patent Application Laid-Open No. 2008-065222, an iodine-based polarizing element not containing two types of azo compounds represented by the formula (1) and the formula (2) was prepared. A measurement sample was prepared in the same manner as in 1.

(Comparative Example 2)
In accordance with the production method shown in Example 1 of JP-A-11-218611, a dye-based polarizing element containing only two kinds of azo compounds represented by the formula (1) and the formula (2) is prepared. A measurement sample was prepared in the same manner as in 1.

(Comparative Example 3)
According to the production method shown in Example 3 of Japanese Patent No. 4162334, a dye-based polarizing element containing only two kinds of azo compounds represented by formula (1) and formula (2) was prepared. Similarly, a measurement sample was prepared.

(Comparative Example 4)
According to the production method shown in Example 1 of Japanese Patent No. 4360100, a dye-based polarizing element containing only two kinds of azo compounds represented by the formula (1) and the formula (2) was prepared. Similarly, a measurement sample was prepared.

[Evaluation method]
(1) Visibility corrected single transmittance The transmittance of each wavelength when a single measurement sample was measured was defined as the single transmittance Ts. In addition, the transmittance of each wavelength when two measurement samples are measured so as to be parallel to each other in the absorption axis direction is the parallel transmittance Tp, and the two measurement samples are orthogonal to each other in the absorption axis direction. Thus, the transmittance at each wavelength when the measurement was repeated was defined as the orthogonal transmittance Tc.
The single transmittance Ts, the parallel transmittance Tp, and the orthogonal transmittance Tc were measured using a spectrophotometer [“U-4100” manufactured by Hitachi, Ltd.]. Each transmittance was measured at intervals of 5 nm using a halogen lamp as a light source. The visibility correction single transmittance Ys, the visibility correction parallel transmittance Yp, and the visibility correction orthogonal transmittance Yc were calculated by performing the visibility correction based on the C light source 2 ° field of view chromaticity function. Table 1 shows the calculation results of the visibility corrected single transmittance Ys.

(2) Polarization degree The polarization degree ρy was obtained by the following formula (5) from the visibility corrected parallel transmittance Yp and the visibility corrected orthogonal transmittance Yc. Table 1 shows the calculation result of the degree of polarization ρy.
ρy = {(Yp−Yc) / (Yp + Yc)} ^1/2 × 100 Formula (5)

(3) a ^* value, b ^* value L ^* a ^* b ^* The a ^* value and b ^* value in the color system were measured with a spectrophotometer [“U-4100” manufactured by Hitachi, Ltd.]. A halogen lamp was used as the light source. a ^* -s and b ^* -s are a ^* value and b ^* value when measured with one measurement sample. Further, a ^* -p and b ^* -p are a ^* values and b ^* values when two measurement samples are measured so that the absorption axis directions are parallel to each other. Further, a ^* -c and b ^* -c are a ^* values and b * values when two measurement samples are measured so that the absorption axis directions are orthogonal to each other. Table 1 shows the measurement results of a ^* -s and b ^* -s, a ^* -p and b ^* -p, a ^* -c and b ^* -c.

(4) Average transmittance at 410 to 750 nm The average transmittance at a wavelength of 410 to 750 nm was determined for each measurement sample. The average transmittance was calculated by averaging the single transmittance Ts in the wavelength region of 410 to 750 nm. Table 1 shows the calculation results of the average transmittance of 410 to 750 nm.

(5) Color observation The parallel color means a color observed in a state in which two measurement samples are overlapped so that the absorption axis directions are parallel to each other. Further, the orthogonal color means a color observed in a state where two measurement samples are overlapped so that the absorption axis directions are orthogonal to each other. In the L ^* a ^* b ^* color system, the hue is more neutral as the a ^* value and the b ^* value are closer to zero. Generally, when a ^* value is positive, it shows reddish color, when it is negative, it shows green color, when b ^* value is positive, it shows yellowish color, and when it becomes negative, it shows blue color. The parallel color and the orthogonal color are visually evaluated.

(6) 1st transmittance | permeability, 2nd transmittance The transmittance | permeability at the time of irradiation of an absolute polarized light is measured using a spectrophotometer ["H-4100" by Hitachi, Ltd.], and JIS Z 8781-4: 2013. Each optical characteristic (transmittance, degree of polarization, hue, etc.) was calculated based on (C light source 2 ° field of view). In measuring the transmittance, an iodine-type polarizing plate (SKN-18043P manufactured by Polatechno Co., Ltd.) having a visibility correction transmittance of 43% and a polarization degree of 99.99% is installed as an absolute polarizing plate between the light source and the measurement sample. The absolute polarized light can be incident on the measurement sample. The protective layer of SKN-18043P was triacetyl cellulose having no ultraviolet absorbing ability.

  The transmittance of each wavelength measured by irradiating with absolute polarized light is overlapped so that the absorption axis direction of the measurement sample and the absorption axis direction of the absolute polarizing plate are parallel to each other, and the first transmittance Ky is measured. The transmittance at each wavelength measured by irradiating with absolute polarized light so that the absorption axis direction and the absorption axis direction of the absolute polarizing plate are orthogonal to each other was defined as the second transmittance Kz. The average value of the first transmittance at 400 nm to 460 nm and the average value of the second transmittance, the average value of the first transmittance and the average value of the second transmittance at 550 nm to 600 nm, and the average of the first transmittance at 600 nm to 670 nm Table 2 shows the values and the average value of the second transmittance.

  Further, the absolute value of the difference between the average value of Ky at 400 nm to 460 nm and the average value of Ky at 550 nm to 600 nm, the absolute value of the difference between the average value of Kz at 400 nm to 460 nm and the average value of Kz at 550 nm to 600 nm, The absolute value of the difference between the average value of Ky at 550 nm to 600 nm and the average value of Ky at 600 nm to 670 nm nm is calculated, and the absolute value of the difference between the average value of Kz at 550 nm to 600 nm and the average value of Kz at 600 nm to 670 nm is calculated. The results are shown in Table 2.

As shown in Table 1, in the measurement samples (polarizing plates) of Examples 1 to 11, the visibility corrected single transmittance Ys is 35 to 45%, and the absolute values of a ^* -s and b ^* -s are 1 The absolute values of a ^* -p and b ^* -p are 2 or less, and the absolute values of a ^* -c and b ^* -c are 2 or less, indicating white in parallel position and orthogonal It was found to show black color. In addition, also in the polarizing element before producing a polarizing plate, when evaluated similarly to a polarizing plate, the visibility correction | amendment single transmittance Ys is 35 to 45%, and the absolute value of a ^* -s and b ^* -s Was 1 or less, the absolute values of a ^* -p and b ^* -p were 2 or less, and the absolute values of a ^* -c and b ^* -c were 2 or less. That is, even in a polarizing plate obtained by laminating an alkali-treated triacetyl cellulose film (TD-80U manufactured by Fuji Photo Film Co., Ltd.) as a transparent protective layer using a polyvinyl alcohol-based adhesive on the polarizing element, the optical characteristics of the polarizing element It was found that it was maintained. Therefore, the polarizing plate obtained using the polarizing element of the present invention has the same performance as the polarizing element of the present invention.

  Further, as shown in Table 1, in Examples 1 to 11, the average transmittance of 410 nm to 750 nm exceeds 41%, which is described in Example 1 and Example 2 of Japanese Patent No. 3357803. 31 It was found to have a higher transmittance than ˜32% polarizing plate. In addition, when the average transmittance exceeds 40%, the L value also exceeds 70, so that the polarizing element is quite good.

In contrast, Comparative Example 1 does not contain the azo compounds represented by the formulas (1) and (2) or their salts in the form of the free acid, and therefore a ^* -p and b ^* -p The absolute value of was more than 2, and it was found to be yellowish green in parallel position. In Comparative Example 2, since it did not contain iodine, the absolute value of b ^* -p exceeded 2, and it was found to be yellow in parallel position. In Comparative Example 3, since no iodine was contained, the absolute values of a ^* -p and b ^* -p were over 2, and it was found that yellowish green was exhibited in the parallel position. In Comparative Example 4, since no iodine was contained, the absolute value of b ^* -p exceeded 2, and it was found that yellow was exhibited in the parallel position.

  As shown in Table 2, in Examples 1 to 11, the difference between the average value of the first transmittance at 550 nm to 600 nm and the average value of the first transmittance at 400 nm to 460 nm is 4% or less, and 600 nm. The difference between the average value of the first transmittance at ˜670 nm and the average value of the first transmittance at 550 nm to 600 nm is 3% or less, the average value of the second transmittance at 550 nm to 600 nm and the second value at 400 nm to 460 nm. The difference from the average value of the transmittance is 1% or less, and the difference between the average value of the second transmittance at 600 nm to 670 nm and the average value of the second transmittance at 550 nm to 600 nm is 1% or less. A polarizing plate produced using such a polarizing element can express achromatic white in a parallel position and achromatic black in an orthogonal position while having high transmittance. In addition, the liquid crystal display device using the polarizing element or polarizing plate of the present invention has not only high brightness and high contrast, but also high reliability, long-term high contrast, and high color reproducibility. Device.

Claims (8)

It consists of a base material containing iodine and two kinds of azo compounds represented by the formula (1) and the formula (2) in the form of a free acid or a salt thereof,
Visibility correction single transmittance is 35 to 45%,
The absolute value of the a ^* value and b ^* value in the L ^* a ^* b ^* color system is
When the substrate is measured alone, both are 1 or less,
When the two base materials are overlapped and measured so that the absorption axis directions are parallel to each other, both are 2 or less,
A polarizing element characterized in that when the two base materials are overlapped and measured so that the absorption axis directions are perpendicular to each other, both are 2 or less.

(In the formula, Ar ₁ represents a phenyl group which may have a substituent or a naphthyl group which may have a substituent, and Rr ₁ or Rr ₂ each independently represents a hydrogen atom, a lower alkyl group or a lower alkoxy group. Xr ₁ represents an amino group which may have a substituent, a phenylamino group which may have a substituent, or a phenylazo which may have a substituent A benzoyl group which may have a group, a substituent or a benzoylamino group which may have a substituent.)

(In the formula, Ab ₁ represents a phenyl group which may have a substituent or a naphthyl group which may have a substituent, and Rb _{1 to} Rb ₆ each independently represents a hydrogen atom, a lower alkyl group or a lower alkoxy group. Xb ₁ represents an amino group which may have a substituent, a phenylamino group which may have a substituent, or a phenylazo which may have a substituent A naphthotriazole group optionally having a substituent, a benzoyl group optionally having a substituent, or a benzoylamino group optionally having a substituent.   The polarizing element according to claim 1, wherein the polarization degree is 99% or more. The transmittance of each wavelength measured by irradiating absolute polarized light so that the vibration direction of the light is orthogonal to the absorption axis direction of the polarizing element is the first transmittance, and the light with respect to the absorption axis direction of the polarizing element. When the transmittance of each wavelength measured by irradiating absolute polarized light so that the vibration direction of the second is the second transmittance,
The difference between the average value of the first transmittance at 550 nm to 600 nm and the average value of the first transmittance at 400 nm to 460 nm is 4% or less, and the average value of the first transmittance at 600 nm to 670 nm is 550 nm to 600 nm. The difference from the average value of the first transmittance at 3% or less,
The difference between the average value of the second transmittance at 550 nm to 600 nm and the average value of the second transmittance at 400 nm to 460 nm is 1% or less, and the average value of the second transmittance at 600 nm to 670 nm is 550 nm to 600 nm. 3. The polarizing element according to claim 1, wherein a difference from an average value of the second transmittance at 1 is 1% or less. Formula Xr ₁ is in (1), a phenyl amino group or a substituent which may have a substituent is also optionally benzoylamino group, polarization according to any one of claims 1 3 element. The polarizing element according to any one of claims 1 to 4, wherein the azo compound represented by the formula (2) is an azo compound represented by the formula (3).

(In the formula, Ab ₁ , Rb _{1 to} Rb ₄ , and Xb ₁ are the same as those described in Formula (2).)   The polarizing element according to claim 1, wherein the substrate is a polyvinyl alcohol-based resin film.   A polarizing plate comprising: the polarizing element according to claim 1; and a transparent protective layer formed on at least one surface of the polarizing element.   A liquid crystal display device comprising the polarizing element according to claim 1 or the polarizing plate according to claim 7.