JP6788461B2 - Polarizing element, polarizing plate and liquid crystal display device - Google Patents

Description

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

The polarizing element is generally manufactured by adsorbing and orienting iodine or a dichroic dye, which is a dichroic dye, on a polyvinyl alcohol resin film. A polarizing plate is manufactured by laminating a protective film made of triacetyl cellulose or the like on at least one surface of the polarizing element via an adhesive layer. The polarizing plate is used in 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. Of these, dye-based polarizing plates are characterized by being excellent in heat resistance, wet heat durability, and stability, and having high color selectivity depending on the composition. However, on the other hand, there is a problem that the transmittance is low, that is, the contrast is low as compared with the iodine-based polarizing plate having the same degree of polarization. Therefore, it is desired to develop a polarizing element having high durability, various color selectivity, and higher transmittance and high polarization characteristics.

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

In order to obtain a polarizing element exhibiting an achromatic color, it is necessary that the transmittance is not wavelength-dependent in both the parallel position and the orthogonal position, and the transmittance is constant at each wavelength. The reason why it is yellowish at the parallel position and bluish at 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 of the iodine-based polarizing plate will be described. 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 centered on 480 nm and 600 nm. Absorption of 480nm is polyiodine _{I 3} ^- and PVA complexes, the absorption of 600nm polyiodine _{I 5} ^- is said to be due to the complex of the PVA. Further, polyiodine _{I 5} ^- towards the polarization degree in the 600nm based on the complex of the PVA is, polyiodine _{I 3} ^- higher degree of polarization in the 480nm based on the complex of the PVA. As a result, when trying to make the transmittance of each wavelength constant at the orthogonal position, the transmittance at 600 nm becomes higher than the transmittance at 480 nm at the parallel position, and a phenomenon of yellow coloring occurs at the parallel position. On the contrary, when trying to make the transmittance of each wavelength constant in the parallel position, the transmittance at 600 nm becomes lower than the transmittance at 480 nm in the orthogonal position, and a phenomenon of coloring blue in the orthogonal position occurs. Further, there is a problem that it is difficult to control the color because there is no absorption based on 550 nm, which has the highest human visual sensitivity. That is, since the degree of polarization (two-color ratio) of each wavelength is not constant, wavelength dependence has occurred. Not only when iodine is used as the dichroic dye, but also when an azo compound having dichroism is used, wavelength dependence occurs in the parallel position and the orthogonal position. Generally, there are no known dyes that exhibit the same hue in parallel and orthogonal positions. Among the conventional generally known azo compounds having dichroism, there are azo compounds having completely different wavelength dependence between the parallel position and the orthogonal position, such as yellow at the parallel position and blue at 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 a person differs between the orthogonal position and the parallel position. Therefore, even if color correction is performed, it is necessary to perform color correction suitable for the human sensitivity. It was.

As described above, it is difficult to create a state in which the transmittance of each wavelength is constant at 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, the degree of polarization (bicolor 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 plurality of dichroic dyes are blended to manufacture the polarizing element. , It is extremely difficult to precisely control the relationship between the transmittance and the dichroism at the parallel and orthogonal positions of each dichroic dye. Therefore, it is very difficult to obtain a polarizing element that exhibits achromatic color, and it cannot be achieved by simply applying the three primary colors of color. It is very difficult to control the transmittance of each wavelength in the parallel position and the orthogonal position to be constant because the degree of polarization of each wavelength must be the same. Therefore, in the prior art, it has not been possible to manufacture a polarizing element having a single transmittance of 35% or more, showing an achromatic white in a parallel position, and showing an achromatic black in an orthogonal position.

For example, Patent Document 1 and Patent Document 2 disclose a method 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 or more and 3 or less. 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 eyeglasses having a rate of 2% or less is disclosed. Further, as a solution to the technical problems in Patent Document 1 and Patent Document 2, Patent Document 3 states that the a * value and b * value of the hue obtained according to JIS Z 8729 are the a * value at the time of measuring the single transmittance. And the b * value is within 1 as an absolute value, and the a * value and b * value obtained by measuring the two substrates parallel to the absorption axis direction are within 2 as an absolute value. Disclosed is a polarizing element in which the a * value and b * value obtained by measuring the two base materials at right angles to the absorption axis direction are within 2 as absolute values and the single transmittance is 35% or more. Has been done.

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

Application of functional dyes 1st printing edition, CMC Publishing Co., Ltd., supervised by Masahiro Irie, p98-100

However, according to the examples 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 values are 2.66 to 3.51, it can be seen that they are yellowish green in the parallel position. Further, the a * value of the orthogonal hue is 0.49 to 0.69, but the b * value is -3.40 to -1.81, which indicates that the hue is blue at the orthogonal position.

Further, the polarizing film disclosed in Patent Document 2 is a polarizing film in which the absolute values of the color coordinate values a and b in the UCS color space when measured with one polarizing film are 2 or less. It did not achieve achromatic color in the parallel position and the orthogonal position where the two sheets were overlapped. Further, according to the examples disclosed in Patent Document 2, the single transmittance of the polarizing film is as low as 31.95% and 31.41%. Therefore, it has not been applicable to fields where high transmittance and high contrast are required, particularly 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 achromatic color in parallel and orthogonal positions.

Therefore, the present invention has been made in view of the above circumstances, and is achromatic white when two polarizing elements are stacked so that the 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 capable of expressing achromatic black color when two polarizing elements are stacked so that their absorption axis directions are orthogonal to each other.

As a result of diligent studies to solve the above problems, the present inventor has a high degree of polarization and a high transmittance, and at the same time, the transmittance is kept constant at each of the parallel and orthogonal positions to eliminate the wavelength dependence, and further, each wavelength. It was newly found that in order to make the degree of polarization (bicolor ratio) of the parallel position and the orthogonal position constant, it can be achieved only by containing iodine and two kinds of specific azo compounds. As a result, we have developed a polarizing element that has high transmittance and high contrast, but exhibits achromatic colors in both parallel and orthogonal positions.

（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 structure of the present invention is as shown below.
(1) It is composed of a base material containing iodine and two types of azo compounds represented by the formulas (1) and (2) in the form of free acid or salts thereof, and has a luminosity factor correction simple substance transmittance. It is 35 to 45%, and the absolute values of the a ^* value and the b ^* value in the L ^* a ^* b ^* color system are 1 or less when the base material is measured by itself, and the base material is the base material. When two sheets were overlapped and measured so that the absorption axis directions were parallel to each other, both were 2 or less, and when the two substrates were overlapped and measured so that the absorption axis directions were orthogonal to each other, both were 2 or less. A 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 independently represent a hydrogen atom, a lower alkyl group and a lower alkoxy. Indicates either a group or a lower alkoxy group having a sulfo group, Xr ₁ may have an amino group which may have a substituent, a phenylamino group which may have a substituent, or a phenylazo which may have a substituent. Indicates 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 independently represent a hydrogen atom, a lower alkyl group and a lower alkoxy. Indicates either a group or a lower alkoxy group having a sulfo group, where Xb ₁ is an amino group which may have a substituent, a phenylamino group which may have a substituent, or a phenylazo which may have a substituent. Indicates a group, 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 polarizing element according to (1), wherein the degree of polarization is 99% or more.
(3) 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 set to the first transmittance, the absorption axis direction of the polarizing element. On the other hand, when the transmittance of each wavelength measured by irradiating absolutely polarized light so that the vibration directions of the light are parallel is taken as the second transmittance, the average value of the first transmittance at 550 nm to 600 nm and 400 nm to 460 nm. The difference from the average value of the first transmittance in is 4% or less, and the difference between the average value of the first transmittance in 600 nm to 670 nm and the average value of the first transmittance in 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 average value of the second transmittance at 600 nm to 670 nm. The polarizing element according to (1) or (2), wherein the difference from the average value of the second transmittance in 550 nm to 600 nm is 1% or less.
(4) Xr ₁ in the above formula (1) is an amino group which may have a substituent, a phenylamino group which may have a substituent, or a benzoylamino group which 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 indicate the same as those described in the formula (2).)
(6) The polarizing element according to any one of (1) to (5), wherein the base material 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 color when two polarizing elements are stacked so that the absorption axis directions are parallel to each other, while having high transmittance and high contrast, and the polarizing element 2 An achromatic black color can be expressed when the sheets are stacked so that the absorption axis directions are orthogonal to each other. Further, the polarizing element of the present invention can be used for a polarizing plate and a liquid crystal display device.

[Polarizing element]
The polarizing element of the present invention comprises a base material containing iodine and two types of azo compounds represented by the formulas (1) and (2) in the form of free acids or salts thereof, and is used for luminosity factor correction. The simple substance transmittance is 35 to 45%, and the absolute values of the a ^* value and the b ^* value in the L ^* a ^* b ^* color system are 1 or less when the base material is measured by itself. When two base materials were stacked and measured so that the absorption axis directions were parallel to each other, both were 2 or less, and when two base materials were stacked and measured so that the absorption axis directions were orthogonal to each other, both were measured. It is 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 comprises a base material containing iodine and two types of azo compounds represented by the formulas (1) and (2) in the form of free acids or salts thereof. The base material is not particularly limited as long as it can contain iodine and two types of azo compounds represented by the formulas (1) and (2) in the form of free acids or salts thereof. For example, a molded product molded from a hydrophilic polymer can be mentioned. Examples of the hydrophilic polymer include polyvinyl alcohol-based resin, amylose-based resin, starch-based resin, cellulosic-based resin, and polyacrylate-based resin. When the dichroic dye is contained in the base material, a polyvinyl alcohol-based resin is most preferable as the base material from the viewpoint of processability, dyeability, crosslinkability and the like. The shape of the base material is not particularly limited, but it is preferably in the form of a film.

(Iodine)
The polarizing element of the present invention has a luminosity factor correction simple substance transmittance of 35 to 45% by containing iodine and two specific azo compounds in the base material, 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 when two base materials are stacked and measured so that the absorption axis directions are orthogonal to each other, it can be achieved that both are 2 or less. When iodine is contained in the base material, iodine alone is difficult to dissolve in the solvent and impregnate the base material, so potassium iodide, ammonium iodide, copper iodide, sodium iodide, calcium iodide, cobalt iodide, It is common to contain iodide such as zinc iodide and chloride such as sodium iodide, lithium chloride and potassium iodide together with iodine.

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

In formula (1), Ar ₁ represents a phenyl group or a naphthyl group which may have a substituent, and Rr ₁ or Rr ₂ independently contains a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a sulfo group. Indicates any of the lower alkoxy groups having, Xr ₁ contains 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 substituent. Indicates a benzoyl group which may have a benzoyl group or a benzoylamino group which may have a substituent. In the claims and the specification of the present application, "may have a substituent" means that a case without a substituent is also included. For example, the "phenyl group which may have a substituent" includes a simple phenyl group which is not substituted and a phenyl group which has a substituent. The "lower" of the lower alkyl group and the lower alkoxy group means that the number of carbon atoms is 1 to 4, and the number of carbon atoms is preferably 1 to 3.

Ar 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 a 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 and a sulfo group. It is preferably a lower alkoxy group, a nitro group, an amino group, an acetylamino group or a lower alkylamino group substituted amino group having. 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. 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. Specifically, 3-sulfopropoxy groups and 4-sulfobutoxy groups are preferable, and 3-sulfopropoxy groups are 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 four positions, the combination of the 2-position and the 4-position, 3-. A combination of positions and 5-positions is preferable.

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 lower alkoxy groups having a sulfo group, a hydroxy group, a carboxy group and a sulfo group. Is preferable. 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. Specifically, 3-sulfopropoxy groups and 4-sulfobutoxy groups are preferable, and 3-sulfopropoxy groups are particularly preferable. When the naphthyl group has two sulfo groups, the combination of the 4-position and the 8-position, the 6-position and the 8-position is preferable, and the combination of the 6-position and the 8-position is particularly preferable as the substitution position of the sulfo group. When the naphthyl group has three sulfo groups, a combination of 1-position, 3-position, and 6-position is particularly preferable as the substitution position of the sulfo group.

Xr 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, a benzoyl group or a substituent which may have a substituent. Indicates 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. It is 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. Further, the phenylamino group which may have a substituent has any one or two of an unsubstituted phenylamino group, a methyl group, a methoxy group, a sulfo group, an amino group and a lower alkylamino group. It is preferably a phenylamino group. The phenylazo group which may have a substituent is an unsubstituted phenylazo group or a phenylazo having 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 or a carboxyethylamino group. More preferably, it is 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. The substitution position is not particularly limited, but when there is one substituent, the p-position is particularly preferable.

Rr ₁ or Rr ₂ independently represent a lower alkoxy group having a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a sulfo group. It is preferably a hydrogen atom, a lower alkyl group or a lower alkoxy group, and more preferably a hydrogen atom, a methyl group or a methoxy group. 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. Specifically, 3-sulfopropoxy groups and 4-sulfobutoxy groups are preferable, and 3-sulfopropoxy groups are 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, JP-A-2003-215338, JP-A-9-302250, and Japanese Patent No. 3881175. More specifically, an example of the azo compound represented by the formula (1) is 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 the methods described in JP-A-2003-215338, JP-A-9-302250, Patent 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 a naphthyl group which may have a substituent, and Rb _{1 to} Rb ₆ each independently have a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a sulfo group. Indicates any of the lower alkoxy groups having, Xb ₁ contains 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 substituent. Indicates a benzoyl group that may have or a benzoylamino group that may have a substituent.

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 a 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 and a sulfo group. It is preferably a lower alkoxy group, a nitro group, an amino group, an acetylamino group or a lower alkylamino group substituted amino group having. 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. 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. Specifically, 3-sulfopropoxy groups and 4-sulfobutoxy groups are preferable, and 3-sulfopropoxy groups are 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 four positions, the combination of the 2-position and the 4-position, 3-. A combination of positions and 5-positions is preferable.

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 lower alkoxy groups having a sulfo group, a hydroxy group, a carboxy group and a sulfo group. Is preferable. 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. Specifically, 3-sulfopropoxy groups and 4-sulfobutoxy groups are preferable, and 3-sulfopropoxy groups are particularly preferable. When the naphthyl group has two sulfo groups, the combination of the 4-position and the 8-position, the 6-position and the 8-position is preferable, and the combination of the 6-position and the 8-position is particularly preferable as the substitution position of the sulfo group. When the naphthyl group has three sulfo groups, a combination of 1-position, 3-position, and 6-position is particularly preferable as the substitution position of the 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, a benzoyl group or a substituent which may have a substituent. Indicates a benzoylamino group which may have. Indicates a benzoyl group which may have a substituent or a benzoylamino group which may have a substituent. 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. Is preferable. Further, the phenylamino group which may have a substituent has any one or two of an unsubstituted phenylamino group, a methyl group, a methoxy group, a sulfo group, an amino group and a lower alkylamino group. It is preferably a phenylamino group. The phenylazo group which may have a substituent is an unsubstituted phenylazo group or a phenylazo having 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 or a carboxyethylamino group. More preferably, it is 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. The substitution position is not particularly limited, but when there is one substituent, the p-position is particularly preferable.

Rb _{1 to} Rb ₆ independently represent a lower alkoxy group having a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a sulfo group. It is preferably a hydrogen atom, a lower alkyl group or a lower alkoxy group, and more preferably a hydrogen atom, a methyl group or a methoxy group. 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. Specifically, 3-sulfopropoxy groups and 4-sulfobutoxy groups are preferable, and 3-sulfopropoxy groups are particularly preferable.

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

Further, when the compound represented by the formula (2) is an azo compound represented by the formula (4), the polarization performance of the polarizing element or the 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 thereof include azo compounds described in International Publication No. 2012/108169, International Publication No. 2012/108173, and the like. More specifically, an example of the azo compound represented by the formula (2), the formula (3) or the formula (4) is 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]

[化合物例２４]

[化合物例２５]

[化合物例２６]

[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 the methods described in International Publication No. 2012/108169, International Publication No. 2012/108173, and the like. However, it is not limited to these.

The polarizing element of the present invention may contain an azo compound other than the azo compounds represented by the formulas (1) and (2) as a color correction to the extent that the performance of the present invention is not impaired. As the other azo compound to be contained, a compound having high dichroism is particularly preferable. For example, an azo compound as shown in Non-Patent Document 1, C.I. I. Direct. Yellow12, C.I. I. DirectYello 28, C.I. I. Direct. Yellow44, C.I. I. Direct. Orange 26, C.I. I. Direct. Orange39, C.I. I. Direct. Orange 107, C.I. I. Direct. Red2, C.I. I. Direct. Red31, C.I. I. Direct. Red79, C.I. I. Direct. Red247, C.I. I. Direct. Green80, C.I. I. Direct. Green59, and azo compounds described in JP-A-64-5623, JP-A-3-12606, JP-A-2001-33627, JP-A-2002-296417, and JP-A-60-156759. And so on. In particular, an azo compound having phenyl J acid in the trisazo structure can be preferably used, and in particular, the azo compound described in JP-A-3-12606 is expressed in the form of iodine and free acid in the form of formula (1). And two kinds of azo compounds represented by each of the formula (2) or salts thereof are suitable for use in a polarizing element. Other azo compounds can be used as salts of alkali metal salts (for example, sodium salt, potassium salt, lithium salt), ammonium salts, or amines in addition to free acids. However, other azo compounds are not limited to these, and known azo compounds having dichroism can be used. Incorporating other azo compounds in the form of free acids, salts thereof, or copper complex salts thereof improves optical properties in particular. The other azo compounds may be used alone or in combination of two or more.

(Luminosity factor correction single transmittance)
The polarizing element of the present invention has a luminosity factor correction simple substance transmittance of 35 to 45%. If the visual sensitivity correction single transmittance of the polarizing element is 35%, the brightness can be expressed even when used in a liquid crystal display device. The luminosity factor correction single transmittance is preferably 38% or more, more preferably 39% or more, still more preferably 40% or more. The upper limit of the transmittance of the single unit for visual sensitivity correction is 45%. If the transmittance of the single unit for visual sensitivity correction exceeds 45%, the degree of polarization is remarkably lowered and the contrast is lowered, which is unsuitable.

The luminosity factor-corrected single-unit transmittance is a single-unit transmittance with luminosity factor corrected by a 2 ° visual field (C light source). For the luminosity factor correction single transmittance, the single transmittance is calculated every 5 nm or 10 nm for each wavelength of 400 to 700 nm for one measurement sample (for example, a polarizing element or a polarizing plate), and a 2 ° field (C light source) is further obtained. ), It can be obtained by correcting the visual sensitivity.

(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 1 or less when the base material is measured by itself, and two base materials are used. When measured in layers so that the absorption axis directions are parallel to each other, both are 2 or less, and when two base materials are overlapped and measured so that the absorption axis directions are orthogonal to each other, both are 2 or less. ..

The L ^* a ^* b ^* color system is an object color display method specified 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 the 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 substance) are referred to as “a ^* −s” and “b ^* −s”. Further, the a ^* value and the b ^* value when two polarizing elements are overlapped and measured so that the absorption axis directions are parallel to each other are referred to as "a ^* -p" and "b ^* -p". Further, the a ^* value and the b ^* value when two polarizing elements are overlapped and 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, the absolute values of a ^* −s and b ^* −s are 1 or less, the 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. This shows achromatic colors in the parallel and orthogonal positions. 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 a difference of 0.5 as the absolute value of a ^* and b ^* , a person 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, the person is colored in parallel and orthogonal positions. It cannot be felt, and it becomes a good polarizing element.

(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 polarization 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.

(1st transmittance and 2nd transmittance)
Luminosity factor correction single transmittance is 35 to 45%, and the absolute values of a ^* value and b ^* value in the L ^* a ^* b ^* color system are 1 or less when the base material is measured by itself. When two base materials are overlapped and measured so that the absorption axis directions are parallel to each other, both are 2 or less, and when two base materials are overlapped and measured so that the absorption axis directions are orthogonal to each other. In order to obtain a polarizing element having a value of 2 or less, it is preferable to control the transmittance of each wavelength.

Specifically, the transmittance of each wavelength measured by irradiating absolutely 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 absolutely polarized light so that the vibration directions of the light are parallel to each other is defined as the second transmittance, the average value of the first transmittance at 550 nm to 600 nm and the average value 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 average value of the second transmittance at 600 nm to 670 nm and 550 nm. The difference from the average value of the second transmittance at about 600 nm is preferably 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. The difference between the above and the average value of the absolute parallel transmittance at 550 nm to 600 nm is 2% or less. The absolutely polarized light means polarized light that has passed through the polarizing plate when the polarizing plate having a degree of polarization of about 100% is irradiated with light from a standard light source, and means almost 100% polarized light. ..

[Manufacturing method of polarizing element]
Hereinafter, a specific method for manufacturing a polarizing element will be described by taking a polyvinyl alcohol-based resin film as an example as a base material. The polarizing element includes, for example, production of a polyvinyl alcohol-based resin, preparation of a raw film, swelling treatment, dyeing treatment, first cleaning treatment, treatment for containing a cross-linking agent and / or a water resistant agent, stretching treatment, and second cleaning treatment. , Manufactured by performing the drying process in order. Note that some of these processes can be omitted.

(Manufacturing of polyvinyl alcohol resin)
The method for producing the polyvinyl alcohol-based resin is not particularly limited, and a known method can be adopted. 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 a copolymer of vinyl acetate and another monomer copolymerizable therewith. Examples of other monomers copolymerizable 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 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 can also be used. The degree of polymerization of the polyvinyl alcohol-based resin means the degree of viscosity average polymerization, and can be obtained by a method well known in the art. 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 to prepare a raw film. The method for forming the film of the polyvinyl alcohol-based resin is not particularly limited, and a known method can be adopted. 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, preferably 8 to 15% by weight in the raw film. The film thickness of the raw film is not particularly limited, but is preferably about 5 μm to 150 μm, and more preferably about 10 μm to 100 μm.

(Swelling treatment)
The raw film obtained as described above 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 from 1.00 to 1.50 times, more preferably 1.10 to 1.35 times. Since swelling also occurs in the dyeing treatment described later, this swelling treatment may be omitted when the time for producing the polarizing element is shortened.

(Dyeing process)
After the swelling treatment, a dyeing treatment is performed. The dyeing treatment is a treatment of dyeing the film after the swelling treatment with iodine and azo compounds represented by the formulas (1) and (2) in the form of free acid or salts thereof. Dyeing with iodine is performed, for example, by immersing the swelling-treated film in a dyeing solution containing iodine and iodide. The iodide is not particularly limited, and examples thereof include potassium iodide, ammonium iodide, cobalt iodide, and zinc iodide. The concentration of iodine in the dyeing solution is preferably 0.0001% by weight to 0.5% by weight, more preferably 0.001% by weight to 0.4% by weight, still more preferably 0.0001% by weight. ~ 8% by weight.

Further, dyeing with an azo compound represented by the formulas (1) and (2) in the form of a free acid or a salt thereof is performed, for example, by forming the film after the swelling treatment in the form of a free acid in the formula (1) and the formula (1). (2) It is carried out by immersing in a dyeing solution containing the azo compounds represented by each or salts 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. The time of immersion in the solution can be adjusted appropriately, but is preferably 30 seconds to 20 minutes, more preferably 1 to 10 minutes. 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 hydrogencarbonate, sodium chloride, sodium sulfate, anhydrous sodium sulfate, sodium tripolyphosphate and the like as a dyeing aid. The content of the dyeing aid can be arbitrarily adjusted depending on the time and temperature due to the dyeability of the bicolor dye, but is preferably 0 to 5% by weight, more preferably 0.1 to 2% by weight.

Staining with iodine and dyeing with an azo compound may be performed at the same time, but it is better to perform dyeing with an azo compound after dyeing with iodine or dyeing with iodine after dyeing with an azo compound. It is preferable from the viewpoint of management and productivity. The azo compounds represented by the formulas (1) and (2) in the form of free acids may be used as free acids or as salts. Examples of the salt include alkali metal salts such as lithium salt, sodium salt and potassium salt, ammonium salt and alkylamine salt. A sodium salt is preferred.

(1st cleaning process)
After the dyeing treatment, a cleaning treatment (hereinafter, referred to as "first cleaning treatment") can be performed before the next treatment. The first cleaning treatment is a treatment for cleaning the dyeing solution adhering to the film surface in the dyeing treatment. By performing the first cleaning treatment, it is possible to prevent the dye from being mixed in the solution used in the next treatment. In the first cleaning treatment, water is generally used as the cleaning liquid. As the cleaning method, a method of immersing the dyed film in the cleaning liquid is preferable, but a method of applying the cleaning 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 treatment needs to be a temperature at which the film after the dyeing treatment does not melt. Generally, it is washed at 5 to 40 ° C. However, since there is no problem in performance even if the first cleaning process is not performed, this first cleaning process may be omitted.

(Treatment containing a cross-linking agent and / or a water resistant agent)
After the first cleaning treatment, a treatment containing a cross-linking agent and / or a water resistant agent can be performed. Examples of the cross-linking agent include a boron compound such as boric acid, borax or ammonium borate, a polyvalent aldehyde such as glioxal or glutaaldehyde, a polyvalent isocyanate compound such as biuret type, isocyanurate type or block type, and titanium oxy. Examples thereof include titanium compounds such as sulfate, and other examples include ethylene glycol glycidyl ether and polyamide epichlorohydrin. 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 and magnesium chloride. Of these, boric acid is most preferred. Only one type of cross-linking agent and water resistant agent may be used, or a plurality of cross-linking agents and water resistant agents 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 the cross-linking agent and / or a water-resistant agent in the film after the first cleaning treatment. It is also possible to adopt the method of applying. The solution is preferably an aqueous solution. The content of the cross-linking agent and / or the water-resistant agent in the solution is preferably 0.1 to 6.0% by weight, more preferably 1.0 to 4.0% by weight, using boric acid as an example. The temperature of the solution is preferably 5 to 70 ° C, more preferably 5 to 50 ° C. The treatment time is preferably 30 seconds to 6 minutes, more preferably 1 to 5 minutes. However, it is not essential to contain a cross-linking agent and / or a water-resistant agent, and this treatment may be omitted when it is desired to shorten the time or when the cross-linking treatment or the water-resistant treatment is unnecessary.

(Stretching treatment)
After the treatment containing the cross-linking agent and / or the water resistant agent, the stretching treatment is performed. The stretching treatment is a treatment for 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. Further, the treatment is preferably performed in an atmosphere having a humidity of 20 to 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 step, but it can also be stretched in two or more steps.

In the case of the wet stretching method, stretching is performed in water, a water-soluble organic solvent, or a mixed solution thereof. It is preferable to carry out the stretching treatment while immersing the film after the first cleaning treatment in a solution containing a cross-linking agent and / or a water resistant agent. Examples of the cross-linking agent and the water-resistant agent include those mentioned above. The content of the cross-linking agent and / or the water-resistant agent in the solution is preferably 0.5 to 15% by weight, more preferably 2.0 to 8.0% by weight, using boric acid as an example. The draw ratio is preferably 2 to 8 times, more preferably 5 to 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 more preferably 2 to 5 minutes. The film can be stretched in one step, but it can also be stretched in two or more steps.

(Second cleaning process)
After the stretching treatment, a cross-linking agent and / or a water resistant agent may precipitate on the film surface, or foreign matter may adhere to the film surface. Therefore, a cleaning treatment for cleaning the film surface (hereinafter, “second cleaning treatment”” ) Can be done. As the cleaning method, a method of immersing the film after the stretching treatment in the cleaning liquid is preferable, but a method of applying the cleaning liquid to the film after the stretching treatment can also be adopted. The cleaning treatment can be performed in one stage, or the multi-stage treatment in two or more stages can be performed. The washing time is preferably 1 second to 5 minutes. The temperature of the cleaning liquid is not particularly limited, but is usually 5 to 50 ° C, preferably 10 to 40 ° C.

As the solvent used in the treatments up to this point, for example, water, dimethylsulfoxide, N-methylpyrrolidone, methanol, ethanol, propanol, isopropyl alcohol, glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol or Examples thereof include alcohols such as trimethylolpropane and amines such as ethylenediamine or diethylenetriamine, but the present invention is not limited thereto. It is also possible to use a mixture of one or more of these solvents. The most preferred solvent is water.

(Drying process)
After the second cleaning treatment, a drying treatment for drying the film is performed. The drying treatment can be carried out by natural drying. In order to further increase the drying efficiency, compression may be performed using a roll, moisture on the surface may be removed by an air knife, a water absorbing roll, or the like, 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.

By the above method, it is composed of a base material containing iodine and two types of azo compounds represented by the formulas (1) and (2) in the form of free acid or salts thereof, and is transmitted through a single substance for correcting visibility. 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 1 or less when the base material is measured by itself, and the base material is used. When two sheets are overlapped and measured so that the absorption axis directions are parallel to each other, they are both 2 or less, and when two base materials are overlapped and 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 side or both sides. A transparent protective layer can be provided on at least one surface of the polarizing element by applying the polymer to at least one surface of the polarizing element and then drying or heat-treating the polymer. Further, a polymer formed into a film is used as a transparent protective layer, and the transparent protective layer is bonded to at least one surface of the polarizing element and then dried or heat-treated to be transparent to at least one surface of the polarizing element. 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. As such a polymer, for example, a cellulose acetate resin such as triacetyl cellulose or diacetyl cellulose, an acrylic resin, a polyvinyl chloride resin, a nylon resin, a polyester resin, a polyarylate resin, a cyclic polyolefin resin having a cyclic olefin such as norbornene as a monomer is used as a monomer. , Polyolefin, 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 the side chain. Further, 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 attach the transparent protective layer to at least one surface of the polarizing element. The adhesive is not particularly limited, but an adhesive containing polyvinyl alcohol as a main component is preferable. Examples of the polyvinyl alcohol-based adhesive include, but are not limited to, Gosenol NH-26 (manufactured by Nippon Synthetic Chemistry Co., Ltd.) and Excelvar RS-2117 (manufactured by Kuraray Co., Ltd.). A cross-linking agent and / or a water-resistant agent can be mixed with the polyvinyl alcohol-based adhesive. Further, the polyvinyl alcohol-based adhesive may contain a copolymer of maleic anhydride and isobutylene, or a modified product thereof. Examples of the copolymer of maleic anhydride and isobutylene include Isoban # 18 (manufactured by Kuraray) and Isoban # 04 (manufactured by Kuraray), and the ammonia-modified maleic anhydride-isobutylene copolymer includes isoban. Examples thereof include # 104 (manufactured by Kuraray) and Isoban # 110 (manufactured by Kuraray), and examples of the imidized maleic anhydride-isobutylene copolymer include Isoban # 304 (manufactured by Kuraray) and Isoban # 310 (manufactured by Kuraray). ). A water-soluble polyfunctional epoxy compound can be used as the cross-linking agent. Examples of the water-soluble polyfunctional epoxy compound include polyglycerol polyglycidyl ether (Denacol EX-521 (manufactured by Nagase Chemtech)) and 1,3-bis (N, N-diglycidylaminomethyl) cyclohexane (TETRAD-C). (Manufactured by Mitsubishi Gas Chemical Company)). Further, known adhesives such as urethane-based adhesives, acrylic-based adhesives, and epoxy-based adhesives can also 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 and iodides can be simultaneously contained at a concentration of about 0.1 to 10% by weight.

When the polarizing plate is attached to a display device such as a liquid crystal or an organic electroluminescence, various functional layers for improving the viewing angle and / or contrast and a layer having brightness improving property are provided on the surface which will be a non-exposed surface later. Can be provided. It is preferable to use an adhesive to bond the polarizing plate to these layers and display devices.

Further, when the polarizing plate is attached to a display device such as a liquid crystal or an 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 exposed later. Can be done. A coating method is preferable for producing layers having various functionalities, but a film having the functions can also be bonded via an adhesive or an adhesive. Further, the various functional layers are, for example, layers for controlling the phase difference.

The polarizing plate of the present invention has the same optical characteristics as a polarizing element. That is, the absolute values of the a ^* value and the b ^* value in the L ^* a ^* b ^* color system are 1 or less when the polarizing plate is measured by itself, and the absorption axis direction of the two polarizing plates is When they were measured so as to be parallel to each other, they were all 2 or less, and when they were measured so that the absorption axis directions were orthogonal to each other, they were both 2 or less. This shows achromatic colors in the parallel and orthogonal positions.

[Liquid crystal display device]
The polarizing element or polarizing plate of the present invention can be used in a liquid crystal display device. The liquid crystal display device using the polarizing element or the polarizing plate of the present invention is a highly reliable liquid crystal display device having high contrast in the long term and high color reproducibility.

The polarizing element or polarizing plate of the present invention includes a protective layer or a functional layer, a support, and the like, if necessary, and includes a liquid crystal projector, a calculator, a clock, a laptop computer, a word processor, a liquid crystal television, a polarized lens, polarized glasses, and a car navigation system. , And used for indoor and outdoor measuring instruments and indicators. In particular, it is effectively used in a reflective liquid crystal display device, a transflective liquid crystal display device, an organic electroluminescence and the like.

The polarizing plate of the present invention may have a support on at least one surface. Since the support is attached to the polarizing plate, it is preferable that the support has a flat surface portion. Examples of the support include molded products made of inorganic materials such as glass, quartz and sapphire, and organic plastic plates such as acrylic and polycarbonate. Since it is used for optics, the support is preferably a glass molded product. Examples of the glass molded product include a glass plate, a lens, a prism (for example, a triangular prism, a cubic prism) and the like. Examples of the glass material include soda glass and borosilicate glass. A lens having a polarizing plate attached can be used as a condenser lens with a polarizing plate in a liquid crystal projector. Further, a prism to which a polarizing plate is attached 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, the polarizing plate may be attached to the liquid crystal cell. The thickness and size of the support are not particularly limited.

It is preferable that the polarizing plate provided with glass is provided with an antireflection layer on at least one surface of the glass or the polarizing plate in order to further improve the single transmittance. For example, after applying a transparent adhesive (adhesive) to the flat surface of the support, the polarizing plate of the present invention is attached to the coated surface. Further, after applying a transparent adhesive (adhesive) to the polarizing plate, a support may be attached to the coated surface. As the adhesive (adhesive) used here, for example, an acrylic ester-based adhesive is preferable. When this polarizing plate is used as an elliptical polarizing plate, the retardation layer is usually attached to the support, but the polarizing plate may be attached to the support.

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

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

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

(Example 3)
Except that the 0.95 parts by weight of Compound Example 21 described in Example 1 was changed 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 parts by weight of Compound Example 21 described in Example 1 was changed to 0.92 parts by weight of Compound Example 19 having the structure of the formula (2). ..

(Example 5)
Except that the 0.95 parts by weight of Compound Example 21 described in Example 1 was changed to 1.0 part by weight of the dye shown in (44) 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 6)
A measurement sample was prepared in the same manner as in Example 1 except that 0.95 parts by weight of Compound Example 21 described in Example 1 was changed to 0.99 parts by weight of Compound Example 28 having the structure of the formula (2). ..

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

(Example 8)
Except that the 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 0.07 parts by weight according to Example 1 was added to C.I. I. A measurement sample was prepared in the same manner as in Example 1 except that it was changed to 0.88 parts by weight of Direct Red 81.

(Example 10)
Compound Example 1 0.07 parts by weight according to Example 1 was added to C.I. I. A measurement sample was prepared in the same manner as in Example 1 except that it was changed to Direct Red 117 0.65 parts by weight.

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

(Comparative Example 1)
An iodine-based polarizing device containing no two types of azo compounds represented by the formulas (1) and (2) was produced according to the production method shown in Comparative Example 1 of JP-A-2008-06522, and Examples A measurement sample was prepared in the same manner as in 1.

(Comparative Example 2)
According to the production method shown in Example 1 of JP-A-11-218611, a dye-based polarizing element containing only two types of azo compounds represented by the formulas (1) and (2) was produced, and Examples thereof were used. 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 types of azo compounds represented by the formulas (1) and (2) was produced, and the dye-based polarizing element was prepared with the first embodiment. A measurement sample was prepared in the same manner.

(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 types of azo compounds represented by the formulas (1) and (2) was produced, and the dye-based polarizing element was prepared with the first embodiment. A measurement sample was prepared in the same manner.

[Evaluation methods]
(1) Luminosity Factor Correction Single Transmittance The transmittance of each wavelength when the measurement sample was measured with one sheet was defined as the single transmittance Ts. Further, the transmittance of each wavelength when the two measurement samples are overlapped and measured so as to be parallel to each other is defined as the parallel transmittance Tp, and the absorption axis directions of the two measurement samples are orthogonal to each other. The transmittance of each wavelength when the measurements were repeated as described above was defined as the orthogonal position transmittance Tc.
The single transmittance Ts, the parallel position transmittance Tp and the orthogonal position transmittance Tc were measured using a spectrophotometer [“U-4100” manufactured by Hitachi, Ltd.]. A halogen lamp was used as a light source, and each transmittance was measured at 5 nm intervals. The luminosity factor correction single transmittance Ys, the luminosity factor correction parallel position transmittance Yp, and the luminosity factor correction orthogonal position transmittance Yc were calculated by performing the luminosity factor correction based on the C light source 2 ° visual field isochromaticity function. Table 1 shows the calculation results of the luminosity factor correction single transmittance Ys.

(2) Polarization degree The polarization degree ρy was obtained from the luminosity factor correction parallel position transmittance Yp and the luminosity factor correction orthogonal position transmittance Yc by the following equation (5). The calculation results of the degree of polarization ρy are shown in Table 1.
ρy = {(Yp-Yc) / (Yp + Yc)} ^1/2 x 100 Equation (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 ^* value and b ^* value when two measurement samples are overlapped and measured so that the absorption axis directions are parallel to each other. Further, a ^* -c and b ^* -c are a ^* value and b * value when two measurement samples are overlapped and 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 above-mentioned simple substance transmittance Ts in the wavelength region of 410 to 750 nm. Table 1 shows the calculation results of the average transmittance of 41 to 750 nm.

(5) Observation of color The color in the parallel position means the color observed in a state where two measurement samples are overlapped so as to be parallel to each other in the absorption axis direction. Further, the color at the orthogonal position means a color observed in a state where two measurement samples are stacked so that the absorption axis directions are orthogonal to each other. In the L ^* a ^* b ^* color system, the closer each of the a ^* value and b ^* value is to zero, the more neutral the hue is. Generally, a positive a ^* value indicates redness, a negative value indicates greenness, a positive b ^* value indicates yellowness, and a negative value indicates bluishness. The colors in the parallel position and the colors in the orthogonal position are visually evaluated.

(6) First Transmittance, Second Transmittance The transmittance when irradiating absolutely polarized light was measured using a spectrophotometer [“U-4100” manufactured 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). In measuring the transmittance, an iodine-based polarizing plate (SKN-18043P manufactured by Polar Techno Co., Ltd.) having a luminous efficiency correction transmittance of 43% and a polarization degree of 99.99% was installed as an absolute polarizing plate between the light source and the measurement sample. , Absolutely polarized light can be incident on the measurement sample. The protective layer of SKN-18043P was triacetyl cellulose having no ultraviolet absorbing ability.

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

As shown in Table 1, in the measurement samples (polarizing plates) of Examples 1 to 11, the luminosity factor correction single transmittance Ys is 35 to 45%, and the absolute values of a ^* −s and b ^* −s are 1. When 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, white is shown in the parallel position and orthogonal. It was found to show black in place. In addition, when the polarizing element before manufacturing the polarizing plate was also evaluated in the same manner as the polarizing plate, the luminosity factor correction single transmittance Ys was 35 to 45%, and the absolute values of a ^* −s and b ^* −s were obtained. 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 in which a polarizing element is laminated with 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, the optical characteristics of the polarizing element It turned out to maintain. Therefore, the polarizing plate obtained by 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 at 410 nm to 750 nm exceeds 41%, which is described in Examples 1 and 2 of Japanese Patent No. 3357803. It was found to have a higher transmittance than the ~ 32% polarizing plate. Further, when the average transmittance exceeds 40%, the L value also exceeds 70, so that the polarizing element is considerably good.

On the other hand, in Comparative Example 1, since the azo compounds represented by the formulas (1) and (2) or salts thereof are not contained in the form of free acid, a ^* -p and b ^* -p are contained. It was found that the absolute value of was over 2 and it was yellowish green in the parallel position. In Comparative Example 2, since iodine was not contained, the absolute value of b ^* −p exceeded 2, and it was found that the color was yellow in the parallel position. In Comparative Example 3, since iodine was not contained, the absolute values of a ^* -p and b ^* -p exceeded 2, and it was found that they were yellowish green in the parallel position. In Comparative Example 4, since iodine was not contained, the absolute value of b ^* −p exceeded 2, and it was found that the color was yellow 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, and 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 manufactured by using such a polarizing element can express an achromatic white color at a parallel position and an achromatic black color at an orthogonal position while having a high transmittance. Further, the liquid crystal display device using the polarizing element or the polarizing plate of the present invention not only has high brightness and high contrast, but also has high reliability, long-term high contrast, and high color reproducibility. It is a device.

Claims (8)

It consists of a base material containing iodine and two types of azo compounds represented by the formulas (1) and (2) in the form of free acids or salts thereof.
Luminosity factor correction single transmittance is 35 to 45%,
The absolute values of the a ^* and b ^* values in the L ^* a ^* b ^* color system are
When the base material was measured alone, it was 1 or less.
When the two substrates were stacked and measured so that the absorption axis directions were parallel to each other, they were both 2 or less.
A polarizing element characterized in that, when the two substrates are stacked and measured so that the absorption axis directions are orthogonal to each other, the number of the two substrates is 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 independently represent a hydrogen atom, a lower alkyl group and a lower alkoxy. Indicates either a group or a lower alkoxy group having a sulfo group, Xr ₁ may have an amino group which may have a substituent, a phenylamino group which may have a substituent, or a phenylazo which may have a substituent. Indicates 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 independently represent a hydrogen atom, a lower alkyl group and a lower alkoxy. Indicates either a group or a lower alkoxy group having a sulfo group, where Xb ₁ is an amino group which may have a substituent, a phenylamino group which may have a substituent, or a phenylazo which may have a substituent. Indicates a group, 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 polarizing element according to claim 1, wherein the degree of polarization 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 is light with respect to the absorption axis direction of the polarizing element. When the transmittance of each wavelength measured by irradiating absolutely polarized light so that the vibration directions of are parallel to each other is defined as 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 and 550 nm to 600 nm. The difference from the average value of the first transmittance in 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 average value of the second transmittance at 600 nm to 670 nm and 550 nm to 600 nm. The polarizing element according to claim 1 or 2, wherein the difference from the average value of the second transmittance is 1% or less. The polarization according to any one of claims 1 to 3, wherein Xr ₁ in the formula (1) is a phenylamino group which may have a substituent or a benzoylamino group which may have a substituent. 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 indicate the same as those described in the formula (2).) The polarizing element according to any one of claims 1 to 5, wherein the base material is a polyvinyl alcohol-based resin film. A polarizing plate comprising the polarizing element according to any one of claims 1 to 6 and a transparent protective layer formed on at least one surface of the polarizing element. A liquid crystal display device having the polarizing element according to any one of claims 1 to 6 or the polarizing plate according to claim 7.