TWI704187B - Achromatic polarization element, and achromatic polarization plate and liquid crystal display device using the element - Google Patents

Abstract

The purpose of this invention is to provide an achromatic polarization element, and an achromatic polarization plate and a liquid crystal display device using the achromatic polarization element, wherein the achromatic polarization element has high transmittance and high polarization degree, and is achromatic both in white display and black display, to thereby provide high performance to exhibit white color with high quality especially in white display. The means of solution of this invention is to provide a polarization element comprising an azo compound or a salt thereof represented by formula (1), and an azo compound or a salt thereof represented by formula (2).

Description

Achromatic polarizing element, and achromatic polarizing plate and liquid crystal display device using the polarizing element

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

The polarizing element is generally manufactured by adsorbing and aligning the iodine of the dichroic dye or the dichroic dye on the polyvinyl alcohol-based resin film. Here, a polarizing plate obtained by bonding a protective film containing triacetyl cellulose and the like to the polarizing element via an adhesive layer is used in a liquid crystal display device and the like. Polarizers that use iodine as a dichroic pigment are called iodine-based polarizers. On the other hand, polarizers that use dichroic dyes, such as dichroic azo compounds, are called dyes. Department of polarizing plate. Among these, the dye-based polarizing plate has high heat resistance, high humidity and heat durability, and high stability. It also has the characteristics of high color selectivity due to the combination of pigments. On the other hand, it has the same degree of polarization as Compared with iodine-based polarizers, there is a problem of low transmittance and contrast. Therefore, in addition to maintaining high durability and diversified color options, it is hoped that a polarizer with higher transmittance and high polarization characteristics Pieces.

In addition, even if it is a dye-based polarizer with diversified color options, the polarizing elements so far still have a positional relationship in which the absorption axis directions of the two polarizing elements are parallel to each other (hereinafter, also referred to as "parallel position") When the method is overlapped and displayed in white (hereinafter, also referred to as "white display" or "bright display"), there is a problem that the white appears slightly yellowish white. In order to alleviate this white and yellowish problem, even if the polarizing element is made to suppress yellow, the current polarizing plate uses two polarizing elements so that the absorption axis directions are orthogonal to each other (hereinafter, also referred to as "positive" When displaying black (hereinafter, also referred to as "dark display" or "dark display") by overlapping and arranging the way of "intersection"), there is a problem that black appears blue. Therefore, a polarizing plate that shows achromatic white in white display and achromatic black in black display is sought. In particular, when displaying white, it is difficult to obtain a high-quality white polarizer commonly known as paper white.

Since the polarizer is achromatic, it must be in the parallel or orthogonal position. The transmittance does not vary with the wavelength and is approximately a certain value. However, such a polarizer has not yet been obtained. The reason for the difference in hue between white display and black display is that the wavelength dependence of the transmittance in the parallel position and the orthogonal position is different, especially the transmittance covering the visible light region is not constant. Furthermore, the fact that the dichroism covers the visible light area is not certain and it is one of the reasons why it is difficult to realize the achromatic polarizer.

Taking an iodine-based polarizer as an example, an iodine-based polarizer that uses polyvinyl alcohol (hereinafter, also referred to as "PVA") as a base material and iodine as a dichroic dye, generally has 480nm and 600nm Absorption from the center. The absorption at 480 nm is due to the complex of polyiodine I ₃ ^- and PVA, and the absorption at 600 nm is due to the complex of polyiodine I ₅ ^- and PVA. The degree of polarization (dichroism) in each wavelength is based on the degree of polarization (dichroism) of the complex of polyiodine I ₅ ^- and PVA than the degree of polarization of the complex of polyiodine I ₃ ^- and PVA (two Color) is still high. That is, if it is desired to make the transmittance of the orthogonal position constant in each wavelength, the transmittance of the parallel position is higher than 480nm at 600nm, and the phenomenon of white and yellowish coloring occurs when white is displayed. On the contrary, if the transmittance of the parallel position is to be constant, the transmittance of the orthogonal position is lower than that of 480nm due to the 600nm aspect, so the black color is blue when displaying black. When white is displayed in white, when white is yellow, it is hard to say that it is better because it generally gives the impression that deterioration will progress. In addition, when the black is displayed in blue, it is not a clear black, giving an impression of no sense of luxury. In addition, the iodine-based polarizer is mainly near 550nm, where the visual sensitivity is high. There is no complex compound based on this wavelength, so the hue is difficult to control. In this way, since the degree of polarization (dichroism) of each wavelength is not constant, the wavelength dependence of the degree of polarization occurs. In addition, there are only two dichroic pigments of 480nm and 600nm that are absorbed by the complex of iodine and PVA, so iodine-based polarizers containing iodine and PVA cannot adjust the hue.

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

In addition, achromatic dyed polarizers have also been developed (e.g. Such as Patent Document 3).

[Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 4281261

[Patent Document 2] Japanese Patent No. 3357803

[Patent Document 3] WO2014/162635

However, the polarizing plate system of Patent Document 1 shows from the examples that even if the intermediate coefficient (Np) is low, the hue system a* value of the parallel position obtained from JIS Z 8729 is -2 to -1, and b* value It is 2.5 to 4.0, so it appears yellow-green when displayed in white. In addition, the hue a* value of the orthogonal position is 0 to 1, but the b* value is -1.5 to -4.0, so it becomes a polarizing plate with black display and blue.

In addition, the polarizing film of Patent Document 2 is obtained when the a value and b value in the UCS color space measured by using only one polarizing film are set to an absolute value of 2 or less, and the white display when two polarizing films are overlapped and In the two hues when black is displayed, it is not the one that can appear achromatic at the same time. Furthermore, the average value of the monomer transmittance of the polarizing film of Patent Document 2 is 31.95% in Example 1 and 31.41% in Example 2, which shows a low value. As such, the polarizing film system of Patent Document 2 has a low transmittance, so it is not a sufficient performance in the field of seeking high transmittance and high contrast, especially in the fields of liquid crystal display devices and organic electroluminescence. Then, the polarizing film of Patent Document 2 uses iodine as the main dichroic pigment, so after the durability test, it is particularly durable under damp heat. After a performance test (for example, an environment at 85°C and a relative humidity of 85%), the color changes greatly and the durability is poor.

On the other hand, the dye-based polarizer system is excellent in durability, but the wavelength dependence is the same as that of the iodine-based polarizer in the parallel position and the orthogonal position. There are few azo compounds exhibiting dichroism that exhibit the same hue in the parallel position and the orthogonal position, and even if they exist, the dichroism (polarization characteristic) is low. According to the type of dichroic azo compounds, the white is yellow when displayed in white, and the black is blue when displayed in black. In the orthogonal and parallel positions, the wavelength dependence of the azo compounds is also completely different. exist. Also, according to the light and shade of light, the sensibility of human color is different. If the color correction of the dye-based polarizer is performed, it must be suitable to cover the parallel position from the orthogonal position and adjust the light and dark of the light generated by the polarized light. Correction. The achromatic polarizer is in the parallel position and the orthogonal position, and the transmittance is approximately a certain value at each wavelength, and if it is in a state without wavelength dependence, it cannot be achieved. Furthermore, in order to obtain a polarizing element with high transmittance and high contrast, a certain transmittance must be satisfied at the parallel position and orthogonal position at the same time, and the polarization degree (dichromatic ratio) of each wavelength must be high, and For certain. When one type of azo compound is applied to the polarizing element, although the wavelength dependence of the transmittance in the orthogonal position and the parallel position is different, it is necessary to mix two or more azo compounds to achieve a certain transmittance. Considering the penetration rate of each parallel position and the penetration rate of the orthogonal position, the relationship between the two-color ratio of two or more types must be precisely controlled.

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

Therefore, the object of the present invention is to provide an achromatic polarizing element, and an achromatic polarizing plate and a liquid crystal display device using the polarizing element. The achromatic polarizing element has high transmittance and high degree of polarization, while displaying white In both time and black display, it is achromatic, especially in white display with high-quality white performance.

In order to solve the above-mentioned problems, the inventors of the present invention have conducted intensive research and found that by the formulation of specific azo compounds, it is possible to produce dichroism without wavelength dependence, and there is no difference between the parallel position and the orthogonal position. Color polarizing element with higher degree of polarization. The inventors of the present invention first discovered that even a high transmittance can achieve wavelength-independence in the visible light field, and developed a paper-like quality white that can achieve high quality. Paper white polarizing element with higher degree of polarization. That is, the present invention relates to the following [1] to [12].

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

(式中，Ag₁係表示具有取代基之苯基或萘基，Rg₁係表示氫原子、低級烷基、低級烷氧基、或具有磺基之低級烷氧基，Xg₁係表示可具有取代基之胺基、或可具有取代基之苯基胺基。)；

(式中、Ar₁、Rr₁及Rr₂係分別獨立地，如式(1)所定義，Xr₂表示可具有取代基之胺基、可具有取代基之苯基胺基、可具有取代基之苯基偶氮基、可具有取代基之苯甲醯基、或可具有取代基之苯甲醯基胺基。)；

(式中、Ag₁及Rg₁分別獨立地，如式(2)所定義，Xg₂表示具有取代基之胺基、可具有取代基之苯基胺基、可具有取代基之苯基偶氮基、可具有取代基之苯甲醯基、或可具有取代基之苯甲醯基胺基。) [1] A polarizing element comprising: (A) an azo compound represented by formula (1) or a salt thereof, and an azo compound represented by formula (2) or a salt thereof; or, (B) The azo compound represented by formula (3) or its salt, the azo compound represented by formula (4) or its salt, and the azo compound represented by formula (5) or its salt;

(In the formula, Ar ₁ represents a substituted phenyl or naphthyl group, and Rr ₁ and Rr ₂ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group, Xr ₁ represents an amino group which may have a substituent or a phenylamino group which may have a substituent);

(In the formula, Ag ₁ represents a substituted phenyl or naphthyl group, Rg ₁ represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group with a sulfo group, and Xg ₁ represents a Substituent amino group or phenylamino group which may have substituent.);

(In the formula, Ar ₁ , Rr ₁ and Rr ₂ are independently, as defined in formula (1), Xr ₂ represents an amino group that may have a substituent, a phenylamino group that may have a substituent, and a substituent that may have a substituent The phenylazo group, the benzylamino group which may have a substituent, or the benzylamino group which may have a substituent.);

(In the formula, Ag ₁ and Rg ₁ are independently, as defined in formula (2), Xg ₂ represents a substituted amino group, a substituted phenylamino group, and a substituted phenylazo group Group, optionally substituted benzylamino group, or optionally substituted benzylamino group.)

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

(In the formula, Ab ₁ represents a substituted phenyl or naphthyl group, and Rb ₁ to Rb ₆ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group, Xb ₁ represents an amino group which may have a substituent, or a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, or a naphthotriazole group which may have a substituent, which may have a substituent The benzyl group or the benzylamino group which may have a substituent.);

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

[3] The polarizing element according to [1] or [2], wherein the absolute values of the a* value and b* value obtained when measuring the transmittance of natural light in accordance with JIS Z 8781-4:2013 are in the foregoing The individual polarizing elements are all 1.0 or less, and the two polarizing elements are arranged so that the absorption axis directions of the two polarizing elements are overlapped so that the directions of their absorption axes are parallel to each other.

[4] The polarizing element according to any one of [1] to [3], wherein the monomer transmittance of the polarizing element is 35% to 45%, so that the absorption axis direction of the two polarizing elements becomes The average transmittance from 520nm to 590nm is 25% to 35% in the state of overlapping and arranged in parallel.

(式中，Ab₁、Rb₁至Rb₄、及Xb₁係如式(5)所定義。) [5] The polarizing element according to [4], wherein the azo compound represented by the aforementioned formula (5) is an azo compound represented by the formula (6);

(In the formula, Ab ₁ , Rb ₁ to Rb ₄ , and Xb ₁ are as defined in formula (5).)

(式中，Ry₁及Ry₂係分別獨立地表示磺基、羧基、羥基、低級烷基、或低級烷氧基，n係表示1至3之整數。)； [6] The polarizing element according to any one of [1] to [5], which further contains the azo compound represented by formula (7) or a salt thereof;

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

[7] The polarizing element according to any one of [1] to [6], which is in the formula (3), Xr ₂ represents an amino group which may have a substituent or a phenylamino group which may have a substituent, In formula (4), Xg ₂ represents an amino group which may have a substituent or a phenylamino group which may have a substituent;

[8] The polarizing element according to any one of items [1] to [7], which is obtained with respect to a state in which the two polarizing elements are arranged so that their absorption axis directions are mutually orthogonal The absolute value of the difference between the average transmittance of 420nm to 480nm and the average transmittance of 520nm to 590nm is less than 0.3%, and the average transmittance of 520nm to 590nm and the average transmittance of 600nm to 640nm The absolute value of the difference is less than 0.3%;

[9] The polarizing element according to any one of [1] to [8], wherein the two polarizing elements are arranged so that the absorption axis directions of the two polarizing elements are overlapped so as to be orthogonal to each other, according to JIS Z 8781- 4: The absolute value of a* value and b* value obtained when measuring the transmittance of natural light in 2013 is less than 2.0;

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

[11] A polarizing plate comprising the polarizing element described in any one of [1] to [10], and a single-sided or double-sided transparent protective layer provided on the aforementioned polarizing element;

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

The present invention provides an achromatic polarizing element, and an achromatic polarizing plate and a liquid crystal display device using the polarizing element. The achromatic polarizing element has high transmittance and high degree of polarization, and is effective in both white display and black display. The two are achromatic, especially when the white display shows high-quality white performance.

<Polarizing element>

The polarizing element of the present invention contains the azo compound represented by formula (1) or its salt and the azo compound represented by formula (2) or its salt, or contains the azo compound represented by formula (3) or its salt , The azo compound represented by formula (4) or its salt and the azo compound represented by formula (5) or its salt. Preferably, the polarizing element includes these azo compounds or their salts, and a substrate for adsorbing the aforementioned azo compounds or their salts.

The substrate is preferably a film obtained by forming a hydrophilic polymer capable of adsorbing dichroic dyes, especially azo compounds. The hydrophilic polymer system is not particularly limited, but may be, for example, polyvinyl alcohol-based resin, amylose-based resin, starch-based resin, cellulose-based resin, and polyacrylate-based resin. From the viewpoints of the dyeability, processability, and crosslinkability of the dichroic pigment, the most preferred hydrophilic polymer is polyvinyl alcohol resin and its derivatives. It can be extended by the base material adsorbing the azo compound or its salt, etc. Alignment process to produce polarizing element.

The polarizing element of the present invention can be obtained from the azo compound represented by formula (1) or its salt and the azo compound represented by formula (2) or its salt (azo compound group of group A), or by formula ( 3) Derived from the azo compound or its salt, the azo compound or its salt represented by the formula (4), and the azo compound or its salt (the azo compound group of the B group) represented by the formula (5) .

Describe the azo compound represented by formula (1).

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

When Ar ₁ is a phenyl group, it preferably has at least one sulfo group or carboxyl group as its substituent. When the phenyl group has two or more substituents, at least one of its substituents is a sulfo group or a carboxyl group, and the other substituents are preferably sulfo group, carboxyl group, lower alkyl group, lower alkoxy group, lower sulfo group Alkoxy, nitro, benzyl, amino, acetamido and lower alkylamino substituted amino, more preferably sulfo, methyl, ethyl, methoxy, ethoxy, Carboxyl, nitro, benzyl and amino groups, particularly preferably sulfo, methyl, methoxy, ethoxy, benzyl and carboxyl groups. The lower alkoxy group with a sulfo group is preferably a straight-chain alkoxy group, and the substitution position of the sulfo group is preferably at the end of the alkoxy group, more preferably 3-sulfopropoxy and 4-sulfobutyl Oxy, but particularly preferably 3-sulfopropoxy. The number of sulfo groups possessed by the phenyl group is preferably 1 or 2, and the substitution position is not particularly limited, but only the 4-position, the combination of the 2-position and the 4-position, and the combination of the 3-position and the 5-position are preferable. When Ar ₁ is a substituted naphthyl group, it is preferable to have at least one sulfo group as its substituent. When it has two or more substituents, at least one of its substituents is a sulfo group, and other substituents are preferable It is a sulfo group, a hydroxyl group, a carboxyl group, and a lower alkoxy group having a sulfo group. The lower alkoxy group with a sulfo group is preferably a straight-chain alkoxy group, and the substitution position of the sulfo group is preferably at the end of the alkoxy group, more preferably 3-sulfopropoxy and 4-sulfobutoxy , But particularly preferred is 3-sulfopropoxy. When the number of substituents of the sulfo group is 2, the position of the sulfo group on the naphthyl group is preferably a combination of positions 4 and 8, and a combination of positions 6 and 8, and a combination of positions 6 and 8 is more preferable. When the number of sulfo groups possessed by the naphthyl group is 3, the substitution position of the sulfo group is particularly preferably a combination of 1, 3, and 6 positions.

In the specification of this case, the "lower" of the lower alkyl group, lower alkoxy group, and lower alkylamino group means that the carbon number is 1 to 4, preferably 1 to 3. In addition, in the specification of this case, the "substituent" expediently includes a hydrogen atom.

Rr ₁ and Rr ₂ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group. Rr ₁ and Rr ₂ are each independently, preferably a hydrogen atom, a lower alkyl group, or a lower alkoxy group, and more preferably a hydrogen atom, a methyl group, or a methoxy group. The lower alkoxy group with a sulfo group is preferably a straight-chain alkoxy group, and the substitution position of the sulfo group is preferably at the end of the alkoxy group, more preferably 3-sulfopropoxy and 4-sulfobutyl Oxy, but particularly preferably 3-sulfopropoxy. The substitution positions are preferably only 2 positions, only 5 positions, a combination of 2 and 5 positions, and a combination of 3 and 5 positions.

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

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

Specific examples of the azo compound represented by the formula (1) include, for example, CIDirect Violet 9, and Japanese Patent Laid-Open No. 2003-215338, Japanese Patent Laid-Open No. 9-302250, Patent No. 3881175, etc. The azo compound. Further specific examples of the azo compound represented by formula (1) are shown below in the form of free acid.

[Compound Example 1-1]

[Compound Example 1-2]

[Compound Example 1-3]

[Compound Example 1-4]

[Compound Example 1-5]

[Compound Example 1-6]

[Compound Example 1-7]

[Compound Example 1-8]

[Compound Example 1-9]

[Compound Example 1-10]

[Compound Example 1-11]

[Compound Examples 1-12]

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

In the formula (2), Ag ₁ represents a substituted phenyl group or a substituted naphthyl group. When Ag ₁ is a phenyl group, it preferably has at least one sulfo group or carboxyl group as its substituent. When the phenyl group has two or more substituents, at least one of its substituents is a sulfo group or a carboxyl group, and the other substituents are preferably sulfo group, carboxyl group, lower alkyl group, lower alkoxy group, lower sulfo group Alkoxy, nitro, amino, acetylamino or lower alkylamino substituted amino, other substituents are preferably sulfo, methyl, ethyl, methoxy, ethoxy, carboxyl , Nitro, or amine group, particularly preferably sulfo, methyl, methoxy, ethoxy, or carboxy. The lower alkoxy group with a sulfo group is preferably a straight-chain alkoxy group, and the substitution position of the sulfo group is preferably at the end of the alkoxy group, more preferably 3-sulfopropoxy and 4-sulfobutyl An oxy group, particularly preferably a 3-sulfopropoxy group. The number of substituents of the phenyl group is preferably 1 or 2. The substitution position is not particularly limited, but only the 4-position, the combination of the 2-position and the 4-position, and the combination of the 3-position and the 5-position are preferred.

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

Rg ₁ represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group. Preferably, Rg ₁ is a hydrogen atom, a lower alkyl group, or a lower alkoxy group, and more preferably a hydrogen atom, a methyl group, or a methoxy group. Particularly preferred Rg ₁ system may be methyl or methoxy. The lower alkoxy group with a sulfo group is preferably a straight-chain alkoxy group, and the substitution position of the sulfo group is preferably at the end of the alkoxy group, more preferably 3-sulfopropoxy and 4-sulfobutoxy. Preferably it is 3-sulfopropoxy. The substitution position of Rg ₁ is preferably only the 5-position and only the 6-position, and the particularly preferred system may be substituted at the 5-position.

Xg ₁ represents an amino group which may have a substituent or a phenylamino group which may have a substituent, more preferably a phenylamino group. The amino group which may have a substituent preferably has one or two amino groups selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, an amino group, and a lower alkylamino group. The phenylamino group which may have a substituent preferably has one or two substitutions selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, an amino group, and a lower alkylamino group The phenylamino group of the group is more preferably a phenylamino group having one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, and an amino group. The substitution position is not particularly limited, but one of the substituents is particularly preferably at the p-position relative to the amino group of the phenylamino group.

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

The azo compound represented by the formula (2) or its salt can be synthesized by, for example, the methods described in Japanese Patent Publication No. 64-5623 and Patent No. 3378296, but it is not limited to these.

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

[Compound Example 2-1]

[Compound Example 2-2]

[Compound Example 2-3]

[Compound Example 2-4]

[Compound Example 2-5]

[Compound Example 2-6]

[Compound Example 2-7]

[Compound Example 2-8]

[Compound Example 2-9]

[Compound Example 2-10]

[Compound Example 2-11]

[Compound Example 2-12]

The polarizing element is a combination of azo compounds represented by formula (1) and formula (2) containing group A, which has higher transmittance and higher degree of polarization than conventional achromatic polarizers, but white display It can realize high-quality paper-like white, commonly known as paper white, when it is displayed in black, and can realize achromatic black, especially high-grade clear black.

In addition, the azo compound represented by formula (3) or its salt, the azo compound represented by formula (4) or its salt, and the azo compound represented by formula (5) or its salt (group B The polarizing element obtained from the azo compound group) has improved polarization characteristics, and it is preferable to obtain a polarizing element or a polarizing plate with high reliability.

Describe the azo compound represented by formula (3).

In formula (3), Ar ₁ has the same meaning as defined in formula (1), and specifically represents a substituted phenyl group or a substituted naphthyl group.

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

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

In the specification of this case, the "lower" of the lower alkyl group, lower alkoxy group, and lower alkylamino group means that the carbon number is 1 to 4, preferably Shows 1 to 3. In addition, in the specification of this case, the "substituent" expediently includes a hydrogen atom.

Rr ₁ and Rr ₂ have the same meaning as defined in formula (1), and specifically, each independently represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group. Rr ₁ and Rr ₂ are each independently, preferably a hydrogen atom, a lower alkyl group, or a lower alkoxy group, and more preferably a hydrogen atom, a methyl group, or a methoxy group. The lower alkoxy group with a sulfo group is preferably a straight-chain alkoxy group, and the substitution position of the sulfo group is preferably at the end of the alkoxy group, more preferably 3-sulfopropoxy and 4-sulfobutyl An oxy group is particularly preferably 3-sulfopropoxy.

Xr ₂ represents 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 benzyl group that may have a substituent, or a benzene that may have a substituent The methylamino group is preferably a phenylamino group which may have a substituent. The amino group which may have a substituent preferably has one or two substituents selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, an amino group, and a lower alkylamino group An amino group, more preferably an amino group having one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, an amino group, and a lower alkylamino group . The phenylamino group which may have a substituent preferably has one or two substitutions selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, an amino group, and a lower alkylamino group The phenylamino group of the group is more preferably a phenylamino group having one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, and an amino group. The benzyl group which may have a substituent preferably has one benzyl group selected from the group consisting of a hydrogen atom, a hydroxyl group, a sulfo group, an amino group, and a carboxyethylamino group. The benzylamino group which may have a substituent preferably has one benzylamino group selected from the group consisting of a hydrogen atom, a hydroxyl group, an amino group, and a carboxyethylamino group. The phenylazo group which may have a substituent is preferably composed of a hydrogen atom, a hydroxyl group, an alkyl group with a carbon number of 1 to 4, an alkoxy group with a carbon number of 1 to 4, an amino group and a carboxyethylamino group Group of 1 to 3 phenylazo groups. Xr _{2 is} preferably a benzylamino group which may have a substituent and a phenylamino group which may have a substituent, and more preferably a phenylamino group. The position of the substituent is not particularly limited, but it is particularly preferable to have one substituent at the p-position. As a specific example, when the phenylamino group has a substituent at the p-position relative to the amino group, it is preferable.

The method for obtaining the azo compound represented by the formula (3) includes, for example, the methods described in Japanese Patent Laid-Open No. 2003-215338, Japanese Patent Laid-Open No. 9-302250, and Patent No. 3881175, but it is not limited to And so on.

Specific examples of the azo compound represented by the formula (3) include CIDirect Red 81, CIDirect Red 117, CIDirect Violet 9 and CIDirect Red 127, and Japanese Patent Laid-Open No. 2003-215338, Special The azo compound described in Kaihei 9-302250 and Japanese Patent No. 3881175. Further specific examples of the azo compound represented by formula (3) are shown below in the form of free acid.

[Compound Example 3-1]

[Compound Example 3-2]

[Compound Example 3-3]

[Compound Example 3-4]

[Compound Example 3-5]

[Compound Example 3-6]

[Compound Example 3-7]

[Compound Example 3-8]

[Compound Example 3-9]

[Compound Example 3-10]

[Compound Example 3-11]

[Compound Example 3-12]

[Compound Example 3-13]

[Compound Example 3-14]

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

In the formula (4), Ag ₁ has the same meaning as defined in the formula (1), and specifically represents a substituted phenyl group or a substituted naphthyl group. When Ag ₁ is a phenyl group, it is preferable to have at least one sulfo group or carboxy group as its substituent. When the phenyl group has two or more substituents, at least one of its substituents is a sulfo group or a carboxyl group. The other substituents are preferably sulfo group, carboxyl group, lower alkyl group, lower alkoxy group, lower sulfo group Alkoxy, nitro, amino, acetylamino or lower alkylamino substituted amino, other substituents are preferably sulfo, methyl, ethyl, methoxy, ethoxy, carboxyl , Nitro, or amine group, particularly preferably sulfo, methyl, methoxy, ethoxy, or carboxy. The lower alkoxy group with a sulfo group is preferably a straight-chain alkoxy group, and the substitution position of the sulfo group is preferably at the end of the alkoxy group, more preferably 3-sulfopropoxy and 4-sulfobutoxy Group, particularly preferably 3-sulfopropoxy. The number of substituents of the phenyl group is preferably 1 or 2. The substitution position is not particularly limited, but only the 4-position, the combination of the 2-position and the 4-position, and the combination of the 3-position and the 5-position are preferred.

When Ag ₁ is a naphthyl group having a substituent, the substituent preferably has 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 preferably a sulfo group, a hydroxyl group, a carboxyl group, or a lower alkoxy group having a sulfo group. It is particularly preferred that the naphthyl group has two or more sulfo groups as a substituent. The lower alkoxy group with a sulfo group is preferably a straight-chain alkoxy group, and the substitution position of the sulfo group is preferably at the end of the alkoxy group, more preferably 3-sulfopropoxy and 4-sulfobutoxy , Particularly preferred is 3-sulfopropoxy. When the number of sulfo groups possessed by the naphthyl group is 2, the substitution positions of the sulfo groups are preferably a combination of positions 4 and 8, and a combination of positions 6 and 8, and a combination of positions 6 and 8 is more preferable. When the number of sulfo groups of the naphthyl group is 3, the substitution position of the sulfo group is preferably a combination of 1, 3, and 6 positions.

Rg ₁ has the same meaning as defined in formula (1), and specifically represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group. Rg _{1 is} preferably a hydrogen atom, a lower alkyl group, or a lower alkoxy group, and more preferably a hydrogen atom, a methyl group, or a methoxy group. Particularly preferred Rg ₁ may be methyl or methoxy. The lower alkoxy group with a sulfo group is preferably a straight-chain alkoxy group, and the substitution position of the sulfo group is preferably at the end of the alkoxy group, more preferably 3-sulfopropoxy and 4-sulfobutyl An oxy group is particularly preferably 3-sulfopropoxy.

Xg ₂ represents an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a benzyl group which may have a substituent, a naphtho group which may have a substituent A triazole group or a benzylamino group which may have a substituent. Xg _{2 is} preferably a benzoyl group which may have a substituent or a phenylamino group which may have a substituent, and more preferably a phenylamino group which may have a substituent. The amino group which may have a substituent preferably has one or two amino groups selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, an amino group, and a lower alkylamino group. The phenylamino group which may have a substituent preferably has one or two substitutions selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, an amino group, and a lower alkylamino group The phenylamino group of the group is more preferably a phenylamino group having one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, and an amino group. The substitution position system is not particularly limited, but it is particularly preferred that the substituent is one system having a substituent at the p-position relative to the phenylamino group. The phenylazo group preferably has 1 to 1 selected from the group consisting of a hydrogen atom, a hydroxyl group, an alkyl group having 1 to 4 carbons, an alkoxy group having 1 to 4 carbons, an amino group, and a carboxyethylamino group. 3 phenylazo groups. The benzyl group which may have a substituent is preferably a benzyl group having one substituent selected from the group consisting of a hydrogen atom, a hydroxyl group, an amino group, and a carboxyethylamino group. The naphthotriazole group that may have a substituent is preferably a naphthotriazole group having one or two substituents selected from the group consisting of a hydrogen atom, a sulfo group, an amino group, and a carboxyl group. The preferred substituents are Sulfo. The benzylamino group which may have a substituent is preferably a benzylamino group having one substituent selected from the group consisting of a hydrogen atom, a hydroxyl group, an amino group, and a carboxyethylamino group.

In the polarizing element of the present invention, the content of the azo compound represented by formula (4) or its salt is relative to the content of the azo compound of formula (3) 100 parts by mass, with 0.01 to 5000 parts by mass as the comparison Better, more preferably 0.1 to 3000 parts by mass.

The azo compound represented by the formula (4) or its salt can be synthesized by, for example, methods described in Japanese Patent Publication No. 64-5623 and Patent No. 3378296, but it is not limited to these.

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

[Compound Example 4-1]

[Compound Example 4-2]

[Compound Example 4-3]

[Compound Example 4-4]

[Compound Example 4-5]

[Compound Example 4-6]

[Compound Example 4-7]

[Compound Example 4-8]

[Compound Example 4-9]

[Compound Examples 4-10]

[Compound Example 4-11]

[Compound Examples 4-12]

[Compound Example 4-13]

[Compound Example 4-14]

[Compound Examples 4-15]

[Compound Example 4-16]

[Compound Example 4-17]

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

In formula (5), Ab ₁ represents a substituted phenyl group or naphthyl group. When Ab ₁ is a phenyl group, its substituent preferably has at least one sulfo group or carboxyl group. When the phenyl group has two or more substituents, at least one of its substituents is preferably a sulfo group or a carboxy group. Other substituents are preferably sulfo, carboxy, lower alkyl, lower alkoxy, and sulfo The lower alkoxy group, nitro group, benzyl group, amino group, acetamino group or lower alkylamino group substituted amino group, more preferably sulfo, methyl, ethyl, methoxy, ethyl Oxy group, carboxyl group, nitro group, amino group, particularly preferably sulfo group, methyl group, methoxy group, benzyl group, carboxyl group. The lower alkoxy group with a sulfo group is preferably a straight-chain alkoxy group, and the substitution position of the sulfo group is preferably at the end of the alkoxy group, more preferably 3-sulfopropoxy and 4-sulfobutyl An oxy group, particularly preferably a 3-sulfopropoxy group. The number of substituents of the phenyl group is preferably 1 or 2. The substitution position is not particularly limited, but only the combination of the 4-position, the 2-position and the 4-position, and the combination of the 3-position and the 5-position is preferred.

When Ab ₁ is a naphthyl group having a substituent, the substituent preferably has at least one sulfo group. When the naphthyl group has at least two substituents, at least one of the substituents is a sulfo group, and the other substituents are preferably a sulfo group, a hydroxyl group, a carboxyl group, and a lower alkoxy group having a sulfo group. The lower alkoxy group with a sulfo group is preferably a straight-chain alkoxy group, and the substitution position of the sulfo group is preferably at the end of the alkoxy group, more preferably 3-sulfopropoxy and 4-sulfobutyl The oxy group is particularly preferably 3-sulfopropoxy. When the number of substituents of the sulfo group is 2, the substitution position of the sulfo group in the naphthyl group is preferably a combination of positions 4 and 8 or a combination of positions 6 and 8, and a combination of positions 6 and 8 is more preferable. When the number of sulfo groups is 3, the substitution position of the sulfo group in the naphthyl group is preferably a combination of 1, 3, and 6 positions.

Rb ₁ to Rb ₆ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group. Preferably, Rb ₁ to Rb ₆ are each independently a hydrogen atom, a methyl group, or a methoxy group. The lower alkoxy group with a sulfo group is preferably a straight-chain alkoxy group, and the substitution position of the sulfo group is preferably at the end of the alkoxy group, more preferably 3-sulfopropoxy and 4-sulfobutyl An oxy group is particularly preferably 3-sulfopropoxy.

Xb ₁ represents an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a naphthotriazole group which may have a substituent, and a benzene which may have a substituent A formyl group or a benzylamino group which may have a substituent. Xb _{1 is} preferably a benzylamino group which may have a substituent or a phenylamino group which may have a substituent, more preferably a phenylamino group. The amino group which may have a substituent preferably has any one or two substituents selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, an amino group, and a lower alkylamino group The amine group is preferably an amine 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. The phenylamino group which may have a substituent preferably has one or two substitutions selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, an amino group, and a lower alkylamino group The phenylamino group of the phenyl group is more preferably a phenylamino group having one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, and an amino group. The phenylazo group which may have a substituent preferably has a group selected from a hydrogen atom, a hydroxyl group, an alkyl group with a carbon number of 1 to 4, an alkoxy group with a carbon number of 1 to 4, an amino group, and a carboxyethylamino group. Groups of 1 to 3 substituent phenylazo groups. The naphthotriazole group that may have a substituent is preferably a naphthotriazole group having one or two substituents selected from the group consisting of a hydrogen atom, a sulfo group, an amino group, and a carboxyl group, preferably a substituent Department of sulfo. The benzyl group which may have a substituent is preferably a benzyl group having one substituent selected from the group consisting of a hydrogen atom, a hydroxyl group, a sulfo group, and an amino group. The benzylamino group which may have a substituent is preferably a benzylamino group having one substituent selected from the group consisting of a hydrogen atom, a hydroxyl group, an amino group, and a carboxyethylamino group. The position of the substituent is not particularly limited, but it is particularly preferable to have one substituent at the p-position. For a specific example, when the phenylamino group has a substituent at the p-position relative to the amino group, it is preferable.

The azo compound represented by the formula (5) is the azo compound represented by the formula (6), which is preferable because it can further improve the polarization performance of the polarizing element.

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

The azo compound represented by formula (6) is the azo compound represented by formula (8), which is preferred because it can further improve the polarization performance of the polarizing element.

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

In the polarizing element of the present invention, the content of the azo compound represented by formula (5) or its salt is preferably 0.01 to 8000 parts by mass relative to 100 parts by mass of the azo compound represented by formula (3), More preferably, it is 0.1 to 3000 parts by mass.

Specific examples of the azo compound represented by formula (5) can be synthesized by methods described in, for example, WO2012/108169 and WO2012/108173.

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

[Compound Example 5-1]

[Compound Example 5-2]

[Compound Example 5-3]

[Compound Example 5-4]

[Compound Example 5-5]

[Compound Example 5-6]

[Compound Example 5-7]

[Compound Example 5-8]

[Compound Example 5-9]

[Compound Example 5-10]

[Compound Example 5-11]

[Compound Examples 5-12]

[Compound Example 5-13]

[Compound Example 5-14]

[Compound Example 5-15]

[Compound Example 5-16]

[Compound Example 5-17]

[Compound Example 5-18]

[Compound Example 5-19]

[Compound Example 5-20]

[Compound Example 5-21]

[Compound Example 5-22]

[Compound Example 5-23]

[Compound Example 5-24]

[Compound Example 5-25]

[Compound Example 5-26]

[Compound Example 5-27]

[Compound Example 5-28]

[Compound Example 5-29]

[Compound Example 5-30]

The polarizing element contains the combination of the azo compound represented by the formula (3) to the formula (5), which has a higher transmittance and higher degree of polarization than the conventional achromatic polarizer, and can be realized in white display High-quality paper-like white, commonly known as paper white, can achieve achromatic black when displaying in black, especially clear black with high-grade sense.

The polarizing element of the present invention containing the azo compound represented by formula (1) or its salt and the azo compound represented by formula (2) or its salt (azo compound group of group A) is obtained by further containing the formula ( 7) The azo compound or its salt may have properties such as the chromaticity a* value and b* value, the monomer transmittance, and the average transmittance of a specific wavelength band in the preferable range described later. In addition, it contains the azo compound represented by formula (3) or its salt, the azo compound represented by formula (4) or its salt, and the azo compound represented by formula (5) or its salt (group B Nitrogen compound group) The optical element, by further containing the azo compound represented by formula (7) or its salt, can have the chromaticity a* value and b* value, monomer transmittance, and specific wavelength band in the preferable range described later The average penetration rate and other properties of the domain.

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

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

The azo compound represented by formula (7) has an effect on the transmittance from 400 to 500 nm. In the polarizing element, in particular, the transmittance and polarization (dichroism) on the short-wavelength side of 400 to 500 nm have an effect on the coloration of blue in black display or the yellowing of white in white display. The azo compound represented by formula (7) suppresses the decrease in the transmittance of the short wavelength side of the parallel position of the polarizing element, and can improve the polarization characteristics (dichroism) of 400 to 500 nm, and further reduce the yellowness during white display The blue color appears when it is converted and displayed in black. The polarizing element further contains the azo compound represented by the formula (7), and the monomer transmittance is in the range of 35% to 45%, showing a more neutral hue, and a higher quality in white display. The white of the paper can increase the degree of polarization.

The azo compound represented by formula (7) or its salt can be synthesized by the method described in WO2007/138980, etc., but it can also be obtained from a commercially available one.

Specific examples of the azo compound represented by the formula (7) are, for example, CIDirect Yellow 4, CIDirect Yellow 12, CIDirect Yellow 72, and CIDirect Orange 39, and those having a stilbene structure described in WO2007/138980 Azo compounds, etc., but not limited to these

More specific examples of the azo compound represented by formula (7) are given below. In addition, compound examples are shown in the form of free acid.

[Compound Example 7-1]

[Compound Example 7-2]

(n表示1至3的整數)

(n represents an integer from 1 to 3)

[Compound Example 7-3]

[Compound Example 7-4]

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

The polarizing element of the present invention contains the azo compound represented by formula (1) or its salt and the azo compound represented by formula (2) or its salt (compound group of group A), or contains the formula (3) The azo compound or its salt, the azo compound or its salt represented by the formula (4), and the azo compound or its salt represented by the formula (5) (the compound group of group B), and then any formula (7) The azo compound shown. Such a polarizing element can have a better range of chromaticity a* value and b* value, monomer transmittance, and average transmittance in a specific wavelength band, etc., which can achieve achromatic achromaticity than before The polarizing plate has higher performance.

The blending ratio of the above-mentioned azo compound in the polarizing element is appropriately adjusted so that the transmittance and chromaticity of the above-mentioned azo compound are within the preferable range described later. The performance of the polarizing element depends not only on the mixing ratio of the azo compounds in the polarizing element, but also on the swelling degree of the substrate that adsorbs the azo compound, or the extension ratio, dyeing time, dyeing temperature, pH during dyeing, and the influence of salt And other factors. Therefore, the blending ratio of each azo compound can be determined according to the swelling degree of the substrate, the temperature, time, pH during dyeing, the type of salt, the concentration of the salt, and the extension ratio. Such a blending ratio can be adjusted arbitrarily as needed.

(Penetration rate)

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

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

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

The wavelength bands of 420nm to 480nm, 520nm to 590nm, and 600nm to 640nm are based on the main wavelength bands of the color matching function used for calculation in JIS Z 8781-4:2013. Specifically, in the XYZ color matching function of JIS Z 8701, which is the source of JIS Z 8781-4: 2013, x(λ) with 600nm as the maximum value, y(λ) with 550nm as the maximum value, and 455nm When the respective maximum value of Z(λ), which is the maximum, is set to 100, the respective wavelengths representing values above 20 are the respective wavelength bands of 420nm to 480nm, 520nm to 590nm, and 600nm to 640nm.

The polarizing element of the present invention is arranged by superimposing two polarizing elements such that the absorption axis direction becomes parallel (in bright display or white display). The transmittance (hereinafter, also referred to as "parallel penetration" The absolute value of the difference between the average transmittance from 420nm to 480nm and the average transmittance from 520nm to 590nm is preferably 2.5% or less, more preferably 1.8% or less, and still more preferably 1.5% or less, Especially good line below 1.0%. Further, for the parallel bit transmittance, the absolute value of the difference between the average transmittance from 520nm to 590nm and the average transmittance from 600nm to 640nm is 2.0% or less. Better, more preferably less than 1.5%, even more preferably less than 1.0%. Such a polarizing element can display high-quality paper-like white in parallel position.

In addition, the transmittance (hereinafter, also referred to as "orthogonal transmittance") is measured when two polarizing elements are superimposed and arranged so that the absorption axis direction becomes orthogonal (during black display or dark display). Rate”), the absolute value of the difference between the average transmittance of 420nm to 480nm and the average transmittance of 520nm to 590nm is less than 0.3%, and the average transmittance of 520nm to 590nm and the average transmittance of 600nm to 640nm It is preferable that the absolute value of the difference between the rates is 0.3% or less. Such a polarizing element can display achromatic black in orthogonal positions. Furthermore, for the orthogonal bit transmittance, the absolute value of the difference between the average transmittance from 420 nm to 480 nm and the average transmittance from 520 nm to 590 nm is more preferably 0.2% or less, and even more preferably 0.1% or less. For the orthogonal bit transmittance, the absolute value of the difference between the average transmittance from 520nm to 590nm and the average transmittance from 600nm to 640nm is more preferably 0.2% or less, and particularly preferably 0.1% or less.

Furthermore, the respective average transmittances of the monomer transmittance, parallel transmittance, and orthogonal transmittance in the wavelength bands of 380nm to 420nm, 480nm to 520nm, and 640nm to 780nm are the above wavelengths. When the average transmittance in the bands of 420 nm to 480 nm, 520 nm to 590 nm, and 600 nm to 640 nm is adjusted to the above, it is unlikely to be greatly affected by the pigment, but it is better to adjust to a certain degree. The difference between the average transmittance of the wavelength band from 380nm to 420nm and the average transmittance of 420nm to 480nm is preferably 15% or less, the difference between the average transmittance of 480nm to 520nm and the average transmittance of 420nm to 480nm Below 15%, the difference between the average transmittance from 480nm to 520nm and the average transmittance from 520nm to 590nm is 15% Hereinafter, the difference between the average transmittance from 640 nm to 780 nm and the average transmittance from 600 nm to 640 nm is preferably 20% or less.

(II) monomer penetration rate

The polarizing element of the present invention preferably has a monomer transmittance of 35% to 45%. The transmittance of the monomer is the transmittance of one piece of measurement sample (such as a polarizing element or a polarizing plate), which is corrected for visual sensitivity in accordance with JIS Z 8722:2009. The performance of the polarizer is to find the higher transmittance, but if the monomer transmittance is 35% to 45%, even if it is used in a display device, there is no discomfort and the display is bright. The higher the transmittance, the more the degree of polarization tends to decrease. Therefore, from the viewpoint of the balance with the degree of polarization, it is better that the monomer transmittance is 36% to 41%, and even more preferably 37% to 40% . When the transmittance of the monomer exceeds 45%, although the degree of polarization may decrease, the transmittance of the monomer may exceed 45% when the bright transmittance of the polarizing element or the specific polarization performance and contrast is desired.

(III) Average transmittance of specific wavelength band

The polarizing element preferably has an average transmittance of 25% to 35% in the wavelength range of 520nm to 590nm measured in parallel. When such a polarizing element is installed in a display device, it can be a bright and clear display device with high brightness. The transmittance of the wavelength band from 520nm to 590nm is based on one of the main wavelength bands of the color matching function used for calculation in JIS Z 8781-4:2013. In particular, the wavelength bands from 520 nm to 590 nm are the wavelength bands with the highest visual sensitivity based on the color matching function, and the transmittance in this range can be visually confirmed to be close to the transmittance. Therefore, it is very important to adjust the transmittance of the wavelength band from 520nm to 590nm. The average transmittance of the wavelength band from 520nm to 590nm measured in parallel position is preferably 26% To 33%, even better, 27% to 31%. Furthermore, the degree of polarization of the polarizing element at this time is preferably 80% to 100%, more preferably 95% to 100%, and still more preferably 99% to 100%. The higher the degree of polarization, the better. In the relationship between the degree of polarization and the transmittance, depending on the brightness or the degree of polarization (or contrast), it can be adjusted to a suitable transmittance and degree of polarization.

(Chromaticity a* value and b* value)

The chromaticity a* value and b* value are the values obtained when measuring the transmittance of natural light in accordance with JIS Z 8781-4:2013. The object color display method determined in JIS Z 8781-4:2013 is equivalent to the object color display method specified by the International Commission on Illumination (abbreviation: CIE). The measurement of the chromaticity a* value and b* value is performed by irradiating a measurement sample (for example, a polarizing element or a polarizing plate) with natural light. In addition, in the following, the chromaticity a* value and b* value obtained for one piece of the measurement sample are expressed as a*-s and b*-s, and the measurement sample 2 is arranged so that the directions of the absorption axes are parallel to each other The chromaticity a* value and b* value obtained for the state of the sheet (when displayed in white) are expressed as a*-p and b*-p, and the measurement samples are arranged so that the directions of their absorption axes are orthogonal to each other. The chromaticity a* value and b* value obtained in the state (during black display) are expressed as a*-c and b*-c.

In the polarizing element of the present invention, the absolute values of a*-s and b*-s are preferably 1.0 or less, and the absolute values of a*-p and b*-p are 2.0 or less. Such a polarizing element can display high-quality white when the monomer is a neutral color. The absolute values of a*-p and b*-p of the polarizing element are more preferably 1.5 or less, and still more preferably 1.0 or less. Furthermore, the absolute values of the polarizing element systems a*-c and b*-c are preferably 2.0 or less, and more preferably 1.0 or less. When such a polarizing element is displayed in black, it can display achromatic black.

As long as the absolute value of the chromaticity a* value and b* value is 0.5, humans can perceive the difference in color, and sometimes there is a big difference in color perceived by humans. Therefore, in a polarizing element, it is very important to control these values. In particular, when the absolute values of a*-p, b*-p, a*-c, and b*-c are respectively below 1.0, the white display during white display and the black display during black display are approximately Can not confirm other good color polarizers. Specifically, it can realize achromaticity in parallel, that is, white like high-quality paper, and it can realize a clear black with achromatic high-level sense in orthogonal position.

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

In addition, the polarizing element of the present invention absorbs less light with a wavelength of 700 nm or more than the commonly used iodine-based polarizing plate or Patent Document 3, so it has the advantage of less heat generation even if it is irradiated with light such as sunlight. For example, when a liquid crystal display is used outdoors, sunlight irradiates the liquid crystal display, and as a result, the polarizing element is also irradiated. The solar system also has light with a wavelength of 700nm or more, including near-infrared rays that have a heating effect. For example, a polarizing element using the azo compound described in Example 3 of Japanese Patent Publication No. 02-061988 is due to the absorption of near-infrared light near 700nm. Therefore, the polarizing element of the present invention absorbs very little near-infrared light, so it generates less heat even when exposed to sunlight outdoors. Since the polarizing element of the present invention generates less heat, it is excellent in terms of less deterioration.

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

(Preparation of Embryo Membrane)

The embryonic membrane system can be produced by filming a polyvinyl alcohol-based resin. The polyvinyl alcohol-based resin system is not particularly limited, and a commercially available product can be used, or one synthesized by a known method can also be used. The polyvinyl alcohol-based resin system can be obtained, for example, by saponifying a polyvinyl acetate-based resin. In addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, the polyvinyl acetate-based resin can be exemplified by copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other single systems copolymerized with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The degree of saponification of the polyvinyl alcohol resin is usually about 85 to 100 mol%, and more preferably 95 mol% or more. Polyvinyl alcohol-based resins can also be used and then modified, such as polyvinyl formaldehyde or polyvinyl acetal modified with aldehydes. In addition, the degree of polymerization of polyvinyl alcohol-based resin means the average degree of polymerization of viscosity, which can be obtained by a well-known technique in the technical field, and is usually preferably about 1000 to 10,000, and more preferably a degree of polymerization of 1500 to Around 6000.

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

(Swelling step)

Swelling treatment is applied to the embryonic membrane obtained by the above. The swelling treatment is preferably to immerse the embryonic membrane in a solution at 20 to 50°C for 30 seconds to 10 minutes. The solution is preferably water. The stretching magnification is preferably adjusted to 1.00 to 1.50 times, and more preferably to 1.10 to 1.35 times. When the time for manufacturing the polarizing element is shortened, the swelling process may be omitted because the embryonic membrane is also swollen during the dyeing process described later.

(Dyeing step)

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

The azo compound is a mixture of azo compounds or their salts from the A group composed of compounds of formula (1) and formula (2), or, derived from formula (3), formula (4) and formula (5) The azo compound of group B or the mixture of its salt formed by the compound of) may further use any azo compound or its salt represented by formula (7). In addition, the azo compounds of the dichroic dyes exemplified in "Application of Functional Pigments" (published by CMC, the 1st edition, supervised by Masahiro Irie, pages 98 to 100), etc. can also be used in this case without harm Adjust the color of the performance of the polarizing element. These azo compounds are in addition to free acid In addition to the form of use, the salt of the compound can also be used. Such a salt is, for example, an alkali metal salt such as a lithium salt, a sodium salt, and a potassium salt, or an organic salt such as an ammonium salt and an alkylamine salt, and a sodium salt is preferred.

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

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

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

(Washing step 1)

After the dyeing step, a washing step (hereinafter, also referred to as "washing step 1") can be performed before proceeding to the next step. Dyeing step 1 is a step of washing the dyeing solution attached to the surface of the resin film in the dyeing step. By performing the washing step 1, the migration of dye in the liquid to be treated next can be suppressed. In washing step 1, water can generally be used as a washing liquid. Washing system to soak in It is preferable to perform cleaning with a cleaning solution, and cleaning can also be performed by applying a cleaning solution to the resin film. The washing time is not particularly limited, but it is preferably 1 to 300 seconds, more preferably 1 to 60 seconds. The temperature of the cleaning solution in the cleaning step 1 must be a temperature at which the material constituting the resin film (for example, hydrophilic polymer, here is a polyvinyl alcohol resin) does not dissolve. It is generally washed at 5 to 40°C. However, even if there is no cleaning step 1, there is no problem in performance, so the cleaning step can be omitted.

(Steps containing crosslinking agent and/or water resistant agent)

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

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

(Extension step)

After performing the dyeing step, the washing step 1, or the step containing a crosslinking agent and/or a water-resistant agent, an extension step is performed. The stretching step is to uniaxially stretch the resin film. The extension method may be either a wet extension method or a dry extension method. The extension ratio is preferably 3 times or more, more preferably 4 to 8 times, and particularly preferably 5 to 7 times.

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

In the case of the wet stretching method, it is preferable to stretch the resin film in water, a water-soluble organic solvent, or a mixed solution thereof. It is preferable to perform the stretching treatment while being immersed in a solution containing at least one crosslinking agent and/or water resistance agent. The cross-linking agent and water-resistant agent can be the same as those described in the step of containing the cross-linking agent and/or water-resistant agent. The concentration in the solution of the crosslinking agent and/or water resistance agent in the extension step is, for example, 0.5 to 15 mass The amount% is preferable, and 2.0 to 8.0 mass% is more preferable. The extension temperature is preferably 40 to 60°C, more preferably 45 to 58°C. The extension time is usually 30 seconds to 20 minutes, but 2 to 5 minutes is more preferable. The wet stretching step can be performed in one stage, but can also be performed in two or more stages.

(Washing step 2)

After the stretching step, the crosslinking agent and/or water resistance agent may be deposited on the surface of the resin film, or foreign matter may adhere. Therefore, a cleaning step for cleaning the surface of the resin film (hereinafter, also referred to as "cleaning") Step 2”). The washing time is preferably 1 second to 5 minutes. The cleaning method is preferably to immerse the resin film in a cleaning solution, and it is also possible to apply or apply a solution to the resin film for cleaning. The washing liquid is preferably water. It can also be washed in one stage, or in multiple stages of more than two stages. The temperature of the solution in the washing step is not particularly limited, but it is usually 5 to 50°C, preferably 10 to 40°C.

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

(Drying step)

After the stretching step or the washing step 2, the resin film is dried. The drying process can be carried out by natural drying, but in order to improve drying efficiency, It can be carried out by roller compression, air knife, or suction roller to remove moisture from the surface, and/or by air drying. The drying treatment temperature is preferably 20 to 100°C for drying treatment, more preferably 60 to 100°C for drying treatment. The drying treatment time is, for example, 30 seconds to 20 minutes, but preferably 5 to 10 minutes.

In the manufacturing method of the polarizing element, the swelling degree of the substrate in the swelling step, the mixing ratio of the azo compounds in the dyeing step, the temperature and pH of the dyeing solution, the type of salt such as sodium chloride or mirabilite, and sodium tripolyphosphate , The concentration, the dyeing time, and the stretching magnification in the stretching step are adjusted so that the polarizing element satisfies at least one of the following conditions (i) to (v), and then satisfies (vi) and ( The condition of vii) is more suitable.

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

(ii) Regarding the orthogonal bit transmittance, the absolute value of the difference between the average transmittance of 420nm to 480nm and the average transmittance of 520nm to 590nm is 0.3 or less, the average transmittance of 520nm to 590nm and the difference of 600nm to 640nm The absolute value of the difference in average transmittance is 0.3 or less.

(iii) The monomer penetration rate is 35% to 45%.

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

(v) The absolute value of a* value and b* value measured by the orthogonal position is 2 respectively the following.

(vi) Regarding the parallel bit transmittance, the average transmittance from 520nm to 590nm is 25 to 35%.

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

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

<Polarizer>

The polarizing plate of the present invention is provided with a polarizing element, and a transparent protective layer provided on one or both sides of the polarizing element. The transparent protective layer is set for the purpose of improving the water resistance or handling properties of the polarizing element.

The transparent protective layer is a protective film formed of a transparent material. The protective film is a film with a layer shape that can maintain the shape of the polarizing element, and a plastic with excellent transparency, mechanical strength, thermal stability, and moisture shielding properties. Etc. are better. To form the same layer as this, it can also be provided with the same function. An example of the plastic constituting the protective film can be, for example, polyester resin, acetate resin, polyether resin, polycarbonate resin, polyamide resin, polyimide resin, and polyolefin resin. Thermoplastic resins such as resins and acrylic resins, acrylic, urethane, acrylic urethane, epoxy, and silicone are made from thermosetting resins or ultraviolet curable resins. Films, among these, polyolefin resins include, for example, amorphous polyolefin resins and have polymerization units such as norbornene monomers or polycyclic norbornene monomers having cyclic polyolefins. Of resin. Generally speaking, it is better to choose a protective film that does not hinder the performance of the polarizing element after the laminated protective film. Such a protective film is composed of cellulose acetate resin and triacetyl cellulose (TAC) and camphor It is particularly good. Moreover, as long as the protective film system does not impair the effects of the present invention, it may be processed for the purpose of hard coating treatment, anti-reflection treatment, anti-sticking, or diffusion, anti-glare, etc.

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

Depending on the situation, the polarizing plate is attached to display devices such as liquid crystal, organic electroluminescence (commonly known as OLED or OEL), etc., and then, on the surface of the protective layer or film that becomes the non-exposed surface, it can also be installed for viewing Various functional layers with improved angle and/or contrast, and layers or films with brightness enhancement properties. Various functional layers are, for example, layers or films that regulate phase difference. The polarizing plate is preferably attached to these films or display devices with an adhesive.

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

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

The polarizing element or polarizing plate of the present invention is provided with a protective layer or a functional layer and transparent supports such as glass, crystal, sapphire, etc. according to needs, and can be applied to liquid crystal projectors, computers, clocks, notebook computers, and word processors , LCD TVs, polarizers, polarized glasses, car navigators, and indoor and outdoor measuring devices or displays, etc. In particular, the polarizing element or polarizing plate of the present invention can be suitably used in liquid crystal display devices, such as reflective liquid crystal display devices, semi-transmissive liquid crystal display devices, and organic electroluminescence. The liquid crystal display device using the polarizing element or polarizing plate of the present invention can display white and neutral black like high-quality paper. Furthermore, the liquid crystal display device is a liquid crystal display device having high durability, high reliability, long-term high contrast, and high color reproducibility.

[Example]

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

<Example A>

In the following Example A, the compounds of the group A were used to prepare measurement samples.

[Example A1]

The polyvinyl alcohol film (VF-PS manufactured by Kuraray Corporation) with a saponification degree of 99% or more and an average degree of polymerization of 2400 is immersed in warm water at 45°C for 2 minutes, and swelling treatment is applied to increase the stretching ratio to 1.30 times. Containing 2000 parts by mass of water, 2.0 parts by mass of sodium tripolyphosphate, 2.0 parts by mass of anhydrous Glauber's salt, 0.100 parts by mass of the azo compound exemplified in the compound example 1-1 obtained in Example 1 of Japanese Patent No. 4033443, and having a compound according to Japanese Patent No. 01-005623 0.200 parts by mass of the azo compound of the structure of the compound example 2-8 obtained in Example 1, and 0.14 parts by mass of the Kayarus Supra Orange 2GL manufactured by Nippon Kayaku Co., Ltd. having the structure of the formula (7), immersed in a 45°C dyeing solution The swollen film 6 minutes 00 seconds, so that the azo compound is contained in the film. The obtained film was immersed in an aqueous solution containing 20 g/l of boric acid (manufactured by Societa Chimica Larderello s.p.a.) at 40°C for 1 minute. The film after immersion was extended to 5.0 times, and the extension treatment was carried out for 5 minutes in an aqueous solution containing 30.0 g/l of boric acid at 50°C. While maintaining the tensioned state of the resulting film, it was immersed in water at 25°C for 20 seconds for washing. The cleaned film was dried at 70°C for 9 minutes to prepare a polarizing element. For this polarizing element, polyvinyl alcohol (NH-26 manufactured by VAM & POVAL, Japan) was dissolved in water at 4% as an adhesive, and an alkali-treated triacetyl cellulose film (manufactured by Fuji Photo Film Co., Ltd.) was laminated ZRD-60) to prepare a polarizing plate. The obtained polarizing plate maintains the optical properties of the above-mentioned polarizing element, especially monomer transmittance, hue, degree of polarization, etc. This polarizing plate was used as the measurement sample of Example A1.

[Example A2]

Except that in Example A1, 0.100 parts by mass of the azo compound shown in Compound Example 1-1 was changed to 0.120 parts by mass of the azo compound shown in Compound Example 1-4, the rest was done in the same way to produce polarizing elements and polarizers Plate as the measurement sample.

[Example A3]

In Example A2, except that 0.140 parts by mass of Kayarus Supra Orange 2GL was changed to 0.095 parts by mass of the azo compound shown in Example 7-2 of the formula of WO2007/138980 Example A1, the rest was done in the same way. Polarizing element and polarizing plate are used as measurement samples.

[Example A4]

In Example A1, except instead of 0.140 parts by mass of Kayarus Supra Orange 2GL, 0.110 parts by mass of CIDirect Orange 72 was contained in the dyeing solution, the rest was done in the same manner as in Example A1 to produce a polarizing element and a polarizing plate as Measure the sample.

[Example A5]

In Example A1, except that 0.200 parts by mass of the azo compound having the structure of compound example 2-8 was replaced with 0.240 parts by mass of the azo compound described in compound example 2-12, the rest was done in the same way to produce polarizing elements and polarizers Plate as the measurement sample.

[Comparative Example A1]

In Example A1, except that 0.100 parts by mass of the azo compound shown in Compound Example 1-1 was replaced with CIDirect Red 81 which does not have the structure of formula (1), the rest was done in the same way to produce a polarizing element and a polarizing plate , As the measurement sample.

[Comparative Example A2]

In Example A1, except for replacing 0.100 parts by mass of the azo compound shown in Compound Example 1-1 with the azo compound described in Japanese Patent No. 3661238 Compound Example III-6 which does not have the structure of formula (1), The rest is done in the same way, making polarizing elements and polarizing plates as measurement samples.

[Comparative Example A3]

In Example A1, in addition to 0.100 parts by mass of the azo compound shown in Compound Examples 2-8, the other azo compound described in Example 1 of Japanese Patent No. 2012/165223A1, which does not have the structure of formula (2), 0.450 was replaced The mass parts, except that the dye in the dyeing step is adjusted so that the degree of polarization is 99.9 or higher, the others are the same to make polarizing elements and polarizing plates as measurement samples.

[Comparative Example A4]

In Example A1, except that the aqueous solution (dyeing solution) containing only the azo compound was set to have the same composition as in Example 1 of Patent Document 3, the rest was done in the same manner as in Example A1 of this case to become the same as the example. A1 is about the same transmittance method, except that an azo compound is contained to produce a polarizing element and a polarizing plate, the rest is the same as the measurement sample.

<Example B>

In the following Example B, the compound of group B was used to prepare a measurement sample.

[Example B1]

The polyvinyl alcohol film (VF-PS manufactured by Kuraray Corporation) with a saponification degree of 99% or more and an average degree of polymerization of 2400 is immersed in warm water at 45°C for 2 minutes, and swelling treatment is applied to increase the stretching ratio to 1.30 times. In compound example 3-1 containing 2000 parts by mass of water, 2.0 parts by mass of sodium tripolyphosphate, 2.0 parts by mass of anhydrous Glauber's salt, and 0.100 parts by mass, compound example 5-8 of 0.130 parts by mass, compound example 4-1 of 0.200 parts by mass , And 0.14 parts by mass of CIDirect Orange 39 having the structure of formula (7) in a 45°C dyeing solution, immerse the swollen film for 15 minutes and 00 seconds, so that the azo compound is contained in the film. The resulting film is It is immersed in an aqueous solution containing 20 g/l of boric acid (manufactured by Societa Chimica Larderello s.p.a.) at 40°C for 1 minute. The film after immersion was extended to 5.0 times, and the extension treatment was carried out for 5 minutes in an aqueous solution containing 30.0 g/l of boric acid at 50°C. While maintaining the tensioned state of the resulting film, it was immersed in water at 25°C for 20 seconds for washing. The cleaned film was dried at 70°C for 9 minutes to prepare a polarizing element. For this polarizing element, polyvinyl alcohol (NH-26 manufactured by VAM & POVAL, Japan) was dissolved in water at 4% as an adhesive, and an alkali-treated triacetyl cellulose film (manufactured by Fuji Photo Film Co., Ltd.) was laminated , ZRD-60) and made a polarizing plate. The obtained polarizing plate maintains the optical properties of the above-mentioned polarizing element, especially monomer transmittance, hue, degree of polarization, etc. This polarizing plate was used as the measurement sample of Example B1.

[Example B2]

Except that the swelled film was immersed in the 45°C dyeing solution for 15 minutes and 00 seconds instead of 13 minutes and 30 seconds, the rest was done in the same manner as in Example B1 to produce a polarizing plate.

[Example B3]

Except for the use of compound example 3-1 containing 2000 parts by mass of water, 2.0 parts by mass of sodium tripolyphosphate, 2.0 parts by mass of anhydrous Glauber's salt, and 0.100 parts by mass, compound example 5-29 of 0.115 parts by mass, and compound example 4- of 0.200 parts by mass 1. 0.135 parts by mass of the cleaning solution of Compound Example 7-1 was replaced with the dyeing solution used in Example B1, and the rest was the same as Example B1 to produce a polarizing plate.

[Example B4]

Except for using 2000 parts by mass of water, 2.0 parts by mass of sodium tripolyphosphate, The cleaning solution of 2.0 parts by mass of anhydrous Glauber's salt, 0.100 parts by mass of compound example 3-1, 0.090 parts by mass of compound example 5-6, 0.200 parts by mass of compound example 4-1, and 0.130 parts by mass of compound example 7-1, Instead of the point of the dyeing solution used in Example B1, the rest is done in the same way as Example B1 to make the polarizing plate

[Example B5]

Except for the use of compound example 3-1 containing 2000 parts by mass of water, 2.0 parts by mass of sodium tripolyphosphate, 2.0 parts by mass of anhydrous Glauber's salt, and 0.100 parts by mass, compound example 5-30 of 0.120 parts by mass, and compound example 4- of 0.200 parts by mass 1. 0.145 parts by mass of the cleaning solution of Compound Example 7-1, instead of the staining solution used in Example B1, the rest is done in the same manner as in Example B1 to make a polarizing plate

[Example B6]

Except the use of compound example 3-1 containing 2000 parts by mass of water, 2.0 parts by mass of sodium tripolyphosphate, 2.0 parts by mass of anhydrous Glauber's salt, and 0.100 parts by mass, compound example 5-15 of 0.115 parts by mass, and compound example 4- of 0.200 parts by mass 1. 0.140 parts by mass of the cleaning solution of Compound Example 7-1 was replaced with the staining solution used in Example B1, and the rest was the same as in Example B1 to produce a polarizing plate.

[Example B7]

Using compound example 3-1 containing 2000 parts by mass of water, 2.0 parts by mass of sodium tripolyphosphate, 2.0 parts by mass of anhydrous Glauber's salt, and 0.100 parts by mass, compound example 5-21 of 0.120 parts by mass, compound example 4-1 of 0.200 parts by mass , 0.140 parts by mass of the cleaning solution of Compound Example 7-1, instead of the one used in Example B1 Except for the staining solution, the rest is the same as in Example B1 to make the polarizing plate

[Example B8]

Except the use of compound example 3-1 containing 2000 parts by mass of water, 2.0 parts by mass of sodium tripolyphosphate, 2.0 parts by mass of anhydrous Glauber's salt, and 0.100 parts by mass, compound example 5-27 of 0.115 parts by mass, and compound example 4- of 0.200 parts by mass 1. 0.140 parts by mass of the cleaning solution of Compound Example 7-1 was replaced with the staining solution used in Example B1, and the rest was the same as in Example B1 to produce a polarizing plate.

[Example B9]

Except for the point that 0.208 parts by mass of Compound Example 3-12 (C.I. Direct Red 81) was used instead of 0.100 parts by mass of Compound Example 3-1 in the dyeing solution, the remaining steps were the same as in Example B1 to produce a polarizing plate.

[Example B10]

Except that 0.220 parts by mass of Compound Example 3-11 (C.I. Direct Red 117) was contained in the dyeing solution in place of 0.100 parts by mass of Compound Example 3-1, the polarizing plate was produced in the same manner as in Example B1.

[Example B11]

The polarizing plate was produced in the same manner as in Example B1, except that 0.141 parts by mass of Compound Example 3-14 was substituted for 0.100 parts by mass of Compound Example 3-1 in the dyeing solution.

[Example B12]

Except for the point that 0.200 parts by mass of Compound Example 4-16 was substituted for 0.200 parts by mass of Compound Example 4-1 in the dyeing solution, the rest was implemented Example B1 produced a polarizing plate in the same way.

[Example B13]

Except that the compound example 4-17 containing 0.180 parts by mass was substituted for the compound example 4-1 at 0.200 parts by mass in the dyeing solution, the polarizing plate was produced in the same manner as in Example B1.

[Example B14]

Except that the compound example 7-2 containing 0.095 parts by mass was substituted for 0.140 parts by mass of the compound example 7-1 in the dyeing solution, the polarizing plate was produced in the same manner as in Example B1.

[Example B15]

Except for the point that 0.135 parts by mass of C.I. Direct Yellow 28 was substituted for 0.140 parts by mass of Compound Example 7-1 in the dyeing solution, the other steps were the same as in Example B1 to produce a polarizing plate.

[Example B16]

Except that 0.110 parts by mass of C.I. Direct Orange 72 was substituted for 0.140 parts by mass of Compound Example 7-1 in the dyeing solution, the other steps were the same as in Example B1 to produce a polarizing plate.

[Comparative Example B1]

In Example B1, except that the aqueous solution (dyeing solution) containing only the azo compound was set to have the same composition as that of Example 1 of Patent Document 3, the rest was done in the same manner as Example B1 of this case to become the same as the example. B1 is about the same transmittance, and the polarizing plate is made with azo compound.

[Comparative Example B2]

Obtained high penetration of POLATECHNO company system with intermediate gray High-speed dye-based polarizing plate SHC-115 was used as the measurement sample.

[Comparative Example B3]

A dye-based polarizing plate SHC-128 manufactured by POLATECHNO, which has a mid-gray high contrast, was obtained as a measurement sample.

[Comparative Examples B4 to B9]

According to the preparation method of Comparative Example B1 in Japanese Patent Laid-Open No. 2008-065222, the iodine-containing time is 5 minutes and 30 seconds in Comparative Example B4, 4 minutes and 45 seconds in Comparative Example B5, and Comparative Example B6 4 minutes and 15 seconds, 3 minutes and 30 seconds in Comparative Example B7, 4 minutes and 00 seconds in Comparative Example B8, and 5 minutes and 15 seconds in Comparative Example B9 to produce an iodine-based polarizer that does not contain an azo compound Plate as the measurement sample.

[Comparative Example B10]

Obtained the iodine-based polarizing plate SKW-18245P made by POLATECHNO, which showed paper white in the parallel position, as the measurement sample.

[Comparative Example B11]

For example, Example 1 of Japanese Patent Application Laid-Open No. 11-218611 concerning the dye-based polarizing plate, the polarizing plate was produced.

[Comparative Example B12]

For example, in Example 3 of Japanese Patent No. 4162334 concerning the dye-based polarizing plate, a polarizing plate was produced.

[Comparative Example B13]

For example, Example 1 of Japanese Patent No. 4360100 concerning the dye-based polarizing plate, the polarizing plate was produced.

[Comparative Example B14]

Use CIDirect Red 80 of 1.95 parts by mass of an azo compound with the same color and having a urea skeleton instead of 0.100 parts by mass of compound Example 3-1, adjust it so that the transmittance of the orthogonal position is approximately constant and the color is black Except for the above points, the rest was the same as in Example B1 to produce a polarizing plate.

[Comparative Example B15]

Using 0.133 parts by mass of CIDirect Red 7, which is an azo compound with the same color and dichroism, is used instead of 0.100 parts by mass of Compound Example 3-1. The penetration rate at the orthogonal position is approximately constant. Except for the point of designing for the black method, the rest is done in the same manner as in Example B1 to produce a polarizing plate.

[Comparative Example B16]

Use 0.152 parts by mass of CIDirect Red 45, which is an azo compound with the same color and dichroism, instead of 0.100 parts by mass of Compound Example 3-1. The transmittance of the orthogonal position is approximately constant and the color is black. Except for the design point, the rest is the same as in Example B1 to produce a polarizing plate.

[Comparative Example B17]

Using 0.075 parts by mass of CIDirect Blue 6, which is an azo compound with the same color and dichroism, is used instead of 0.130 parts by mass of compounds in Example 5-8. The penetration rate at the orthogonal position is approximately constant. Except for the point of designing for the black method, the rest is done in the same manner as in Example B1 to produce a polarizing plate.

[Comparative Example B18]

Using 0.085 parts by mass of C.I.Direct Blue 15, which is an azo compound with the same color and dichroism, instead of 0.130 parts by mass of Compound Examples 5-8, The transmittance of the orthogonal position is approximately constant, and the color is black, except for the point where the design is done in the same manner as in Example B1 to make a polarizing plate.

[Comparative Example B19]

Use 0.105 parts by mass of CIDirect Blue 71, which is an azo compound with the same color and dichroism, instead of 0.130 parts by mass of Compound Example 5-8. The penetration rate at the orthogonal position is approximately constant and the color is black. Except for the design point, the rest is the same as in Example B1 to produce a polarizing plate.

[Comparative Example B20]

Use 0.5 parts by mass of CIDirect Blue 199, which is a direct dye with the same color and dichroism, instead of 0.200 parts by mass of Compound Example 4-1. The design is designed so that the transmittance of the orthogonal position is approximately constant and the color is black. Except for the above points, the rest was the same as in Example B1 to produce a polarizing plate.

[Comparative Example B21]

Use CIDirect Blue 218 with the same color dichroism and 0.48 parts by mass of the same copper dye, instead of 0.200 parts by mass of Compound Example 4-1, the transmittance of the orthogonal position is approximately constant. Except for the point of designing for the black method, the rest is done in the same manner as in Example B1 to produce a polarizing plate.

[Evaluation]

The evaluation of the measurement samples obtained in the foregoing Examples A1 to A6 and Comparative Examples A1 to A4, and Examples B1 to B16 and Comparative Examples B1 to B21 were performed as follows.

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

Measured using a spectrophotometer ("U-4100" manufactured by Hitachi, Ltd.) The monomer penetration rate Ts, parallel position penetration rate Tp, and orthogonal position penetration rate Tc of each measurement sample. Here, the monomer transmittance Ts is to measure the transmittance of each wavelength when measuring one sample. Parallel transmittance Tp is the spectral transmittance of each wavelength measured by superimposing two measurement samples so that the absorption axis direction becomes parallel. The orthogonal transmittance Tc is the spectral transmittance measured by superimposing two measurement samples so that their absorption axes are orthogonal. The measurement is performed covering the wavelength of 400 to 700 nm.

Calculate the parallel position transmittance Tp and the orthogonal position transmittance Tc respectively, the average value in 420 to 480 nm, the average value in 520 to 590 nm, and the average value in 600 to 640 nm, which are shown in Table 1.

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

The monomer penetration rate Ys, the parallel position penetration rate Yp, and the orthogonal position penetration rate Yc of each measurement sample are respectively determined. The monomer transmittance Ys, the parallel position transmittance Yp, and the orthogonal position transmittance Yc are calculated at a specific wavelength interval d λ (here 5nm) in the wavelength range of 400 to 700nm. The transmittance Ts, the parallel position transmittance Tp, and the orthogonal position transmittance Tc are respectively corrected for the transmittance of the visual sensitivity according to JIS Z 8722:2009. Specifically, the above-mentioned monomer transmittance Ts, parallel position transmittance Tp, and orthogonal position transmittance Tc are substituted into the following formulas (I) to (III) and calculated respectively. In addition, in the following formulas (I) to (III), the P λ system represents the spectral distribution of the standard light (C light source), and the y λ system represents the 2-degree visual field color matching function. The results are shown in Table 1.

(c) Comparison

The ratio (Yp/Yc) of the parallel position penetration rate and the orthogonal position penetration rate measured using two identical measurement samples was calculated, and the comparison was calculated. The results are shown in Table 1A and Table 1B.

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

Table 2A and Table 2B show the parallel position transmittance Tp and orthogonal position transmittance Tc of each test sample, and the difference between the average value in 520 to 590 nm and the average value in 420 to 480 nm. The absolute value of and the absolute value of the difference between the average value in 520 to 590 nm and the average value in 600 to 640 nm.

As shown in Table 1A and Table 2A, the parallel position transmittance Tp of the measurement samples of Examples A1 to A6 has an average value of 25% or more in the range of 520 to 590 nm. Furthermore, the absolute value of the difference between the average value in 420 to 480 nm and the average value in 520 to 590 nm of the parallel bit transmittance Tp is 1.0% or less, and the average value in 520 to 590 nm and the average value in 590 to 640 nm The absolute value of the difference between the values is 1.0% or less, all of which are very low values. In addition, the orthogonal bit transmittance Tc is the absolute value of the difference between the average value in 420 to 480 nm and the average value in 520 to 590 nm, and the absolute value of the difference is less than 0.05%, and the average transmittance in 520 to 590 nm is the same as 600 to 640 nm. The absolute value of the difference between the average value is less than 0.05%, and all of them are very low values. Therefore, the measurement samples obtained in Examples A1 to A4 show that the average transmittance of each wavelength is approximately constant.

On the other hand, the measurement samples of Comparative Examples A1 to A3 are the absolute value of the difference between the average value of the parallel position transmittance Tp and the above wavelength of the orthogonal position transmittance Tc shown in Table 2. At least any one of the absolute values of the difference between the average values between the bands shows a high value.

Moreover, if comparing Examples A1 to A6 with a monomer transmittance of about 38.5% and Comparative Example A4 of the same achromatic polarizer, the optical characteristics are the parallel transmittance and orthogonal transmittance of Example A2 The ratio (comparison of parallel transmittance and orthogonal transmittance) is 2734, and the comparison of Comparative Example A4 is 317. In addition, Example A1 has a comparison of about 8.6 times that of Comparative Example A1. In this way, compared with the measurement sample of Example A1 and the achromatic dye-based polarizer of Patent Document 3, the contrast is greatly improved.

Also, as shown in Table 1B and Table 2B, Examples B1 to The B16 measurement sample has an average value of 25% or more in the parallel position transmittance Tp from 520 to 590 nm. Furthermore, the absolute value of the difference between the average value in 420 to 480 nm and the average value in 520 to 590 nm of the parallel bit transmittance Tp is 1.0% or less, and the average value in 520 to 590 nm and the average value in 590 to 640 nm The absolute value of the difference between the values is 1.0% or less, all of which are very low values. In addition, the orthogonal bit transmittance Tc is the absolute value of the difference between the average value in 420 to 480 nm and the average value in 520 to 590 nm, and the absolute value of the difference is less than 0.05%, and the average transmittance in 520 to 590 nm is the same as 600 to 640 nm. The absolute value of the difference between the average value is less than 0.05%, and all of them are very low values. Therefore, the measurement samples obtained in Examples B1 to B16 show that the average transmittance of each wavelength is approximately constant.

On the other hand, the measurement samples of Comparative Examples B2 to B21 are the absolute value of the difference between the average values of the parallel position transmittance Tp and the above-mentioned wavelength of the orthogonal position transmittance Tc shown in Table 2. At least any one of the absolute values of the difference between the average values between the bands shows a high value.

Moreover, if comparing Example B1 with a monomer penetration rate of about 37% and Comparative Example B1, the comparison of Example B1 is 11105, the comparison of Comparative Example B1 is 2219, and the comparison of Example B1 is about 5 times that of Comparative Example B1. The contrast. In this way, the contrast between the measurement sample of Example B1 and the achromatic dye-based polarizer of Patent Document 3 is greatly improved. In addition, if comparing Example B6 with a monomer penetration rate of about 39% and Comparative Example B3, the contrast of Example B6 is 6226, the contrast of Comparative Example B3 is 1413, and Example B3 has a contrast of about 4.4 times.

(e) Polarization ρ y

Substitute the parallel transmittance Yp and the orthogonal transmittance Yc into the following formula to obtain the polarization degree ρ y of each measurement sample. The results are shown in 3A and Table 3B.

ρ y={(Yp-Yc)/(Yp+Yc)} ^1/2 ×100

(f) Chromaticity a* value and b* value

For each measurement sample, in accordance with JIS Z 8781-4:2013, when measuring the monomer transmittance Ts, the chromaticity a in each of the parallel position transmittance Tp measurement and the orthogonal position transmittance Tc measurement *Value and b*value. The measurement system uses the above-mentioned spectrophotometer, and measures from the transmitted color, reflected color, and outdoor side. The light source is C light source. The results are shown in Table 3. Here, a*-s and b*-s, a*-p and b*-p, and a*-c and b*-c correspond to the monomer transmittance Ts, parallel position transmittance Tp and The chromaticity a* value and b* value when the orthogonal position transmittance Tc is measured.

(g) Observation of color

For each measurement sample, two identical measurement samples were superimposed on a white light source in parallel and orthogonal positions, and the colors observed at the time were investigated. The observation system was performed by 10 observers visually, and the most observed colors are shown in Table 3. In addition, in Table 3, the color system of the parallel position means the color in the state where the same two samples are overlapped so that the direction of the absorption axis becomes parallel to each other (when displaying white), and the color system of the orthogonal position means the color of the absorption axis The directions are orthogonal to each other and the colors of the state of the same two samples (when displayed in black) are superimposed. Basically, the parallel color of the polarized color system is "white", and the color of the orthogonal position is "black". However, in each case, for example, white with a sense of yellow means "yellow", and black with blue and purple means " Blue and purple."

As shown in Table 3A, it can be seen that the measurement samples of Examples A1 to A4 have a monomer transmittance of 35% or more and a high transmittance, but Shows a high degree of polarization of over 99%, and can fully show white in parallel and black in orthogonal. Furthermore, the measurement samples of Examples A1 to A4 are a*-s, b*-s, a*-p, a*-c, and b*-c. The absolute value of each of a*-s, b*-s, a*-c, and b*-c is 1.0 or less, and b*-p is The absolute value is below 2.0, which shows a very low value. When the measurement samples of Examples B1 to B16 were visually observed, they showed white as high-quality paper in the parallel position, and a clear black with high-quality feeling in the orthogonal position. On the other hand, in Comparative Examples B2 to B21, at least any one of a*-s, b*-s, a*-p, b*-p, a*-c, and b*-c showed high values to When visually observed, it is not achromatic in the parallel or orthogonal position.

As shown in Table 3B, it can be seen that the measurement samples of Examples B1 to B16 have a monomer penetration rate of 35% or more. The measurement samples of Examples B1 to B16 have high transmittance, but show a high degree of polarization of over 99%, which can fully show white in parallel and black in orthogonal. Furthermore, the measurement samples of Examples B1 to B16 are a*-s, b*-s, a*-p, a*-c, and b*-c. The absolute value of each of them is 1.0 or less, b*-p The absolute value is below 2.0, which shows a very low value. When the measurement samples of Examples B1 to B16 were visually observed, they showed white as high-quality paper in the parallel position, and a clear black with high-quality feeling in the orthogonal position. On the other hand, in Comparative Examples B2 to B21, at least any one of a*-s, b*-s, a*-p, b*-p, a*-c, and b*-c showed high values to When visually observed, it is not achromatic in the parallel or orthogonal position.

From the above, although the polarizing element of the present invention has high transmittance and maintains the transmittance of parallel position, it can appear white like high-quality paper in parallel position, and has a neutral color (neutral gray) as a monomer. The hue. Moreover, The polarizing element of the present invention maintains a high transmittance, exhibits achromaticity in the parallel position, and it is known that it also has a high degree of polarization. Furthermore, it can be seen that the polarizing element of the present invention can be obtained in the orthogonal position to display achromatic black polarizing element with a sense of high quality.

(h) Durability test

The measurement samples of Examples B1 to B16 and Comparative Examples B4 to B10 were applied in an environment of 85° C. and a relative humidity of 85% RH for 240 hours. As a result, no change in transmittance or hue was observed in the measurement sample systems of Examples B1 to B16. In contrast, the measurement samples of Comparative Examples B4 to B10 have a lower polarization degree of more than 10%, and the b*-c system is lower than -10, and the color seen by the eyes changes to blue, especially when the two measurement samples are positive When the position is crossed, the black is very blue.

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

Claims (12)

A polarizing element containing the azo compound or its salt represented by formula (3), the azo compound or its salt represented by formula (4), and the azo compound or its salt represented by formula (5);

In the formula, Ar ₁ represents a substituted phenyl or naphthyl group, Rr ₁ and Rr ₂ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group with a sulfo group, Xr ₂ represents an amino group which may have a substituent, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a benzyl group which may have a substituent, or a benzyl group which may have a substituent Amino group

In the formula, Ag ₁ represents a substituted phenyl or naphthyl group, Rg ₁ represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group with a sulfo group, and Xg ₂ represents a substituted group. Amino group which may have a substituent, a phenylamino group which may have a substituent, a benzylamino group which may have a substituent, or a benzylamino group which may have a substituent;

In the formula, Ab ₁ represents a substituted phenyl or naphthyl group, Rb ₁ to Rb ₆ each independently represent a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group with a sulfo group, Xb ₁ represents an amino group that may have a substituent, a phenylamino group that may have a substituent, a phenylazo group that may have a substituent, or a naphthotriazole group that may have a substituent, and a benzene that may have a substituent A formyl group or a benzylamino group which may have a substituent. For the polarizing element described in the first item of the scope of patent application, the two aforementioned polarizing elements are superimposed so that the absorption axis directions become parallel to each other, and the average transmittance obtained from 420nm to 480nm is measured, and the average of 520nm to 590nm is measured. The absolute value of the difference in transmittance is 2.5% or less, and the absolute value of the difference between the average transmittance from 520nm to 590nm and the average transmittance from 600nm to 640nm is 2.0% or less. The polarizing element described in item 1 or 2 of the scope of patent application, wherein the absolute value of a* value and b* value obtained when measuring the transmittance of natural light in accordance with JIS Z 8781-4:2013 The individual polarizing elements are all 1.0 or less, and the two polarizing elements are arranged so that the absorption axis directions of the two polarizing elements are overlapped so that the directions of their absorption axes are parallel to each other. The polarizing element described in item 1 or 2 of the scope of patent application, wherein the monomer transmittance of the polarizing element is 35% to 45%, and the two polarizing elements are superimposed so that the directions of their absorption axes become parallel to each other The average transmittance from 520nm to 590nm obtained from the configuration state is 25% to 35%. The polarizing element described in item 4 of the scope of patent application, wherein the azo compound represented by the aforementioned formula (5) is the azo compound represented by the formula (6);

In the formula, Ab ₁ , Rb ₁ to Rb ₄ , and Xb ₁ are as defined in formula (5). The polarizing element described in item 1 or 2 of the scope of patent application further contains the azo compound represented by formula (7) or its salt;

In the formula, Ry ₁ and Ry ₂ each independently represent a sulfo group, a carboxyl group, a hydroxyl group, a lower alkyl group, or a lower alkoxy group, and n represents an integer of 1 to 3. The polarizing element described in item 1 or 2 of the scope of patent application, wherein, in formula (3), Xr ₂ represents an amino group which may have a substituent or a phenylamino group which may have a substituent. In formula (4) , Xg ₂ represents an amino group which may have a substituent or a phenylamino group which may have a substituent. The polarizing element described in item 1 or 2 of the scope of the patent application, wherein the transmittance obtained when the two polarizing elements are arranged so that their absorption axis directions are orthogonal to each other are overlapped, from 420 nm to The absolute value of the difference between the average transmittance of 480nm and the average transmittance of 520nm to 590nm is 0.3% or less, and the absolute value of the difference of the average transmittance of 520nm to 590nm and the average transmittance of 600nm to 640nm 0.3% or less. The polarizing element described in item 1 or 2 of the scope of patent application, wherein the two aforementioned polarizing elements are arranged in a state where the absorption axis directions of the polarizing elements are overlapped so as to be orthogonal to each other, measured in accordance with JIS Z 8781-4:2013 The absolute value of the a* value and b* value obtained when the natural light transmittance is 2.0 or less. The polarizing element described in claim 1 or 2, wherein the polarizing element contains a polyvinyl alcohol-based resin film as a base material. A polarizing plate is provided with the polarizing element described in any one of items 1 to 10 in the scope of patent application, and a single-sided or double-sided transparent protective layer provided on the aforementioned polarizing element. A liquid crystal display device is provided with the polarizing element described in any one of the scope of patent application 1 to 10 or the polarizing plate described in the scope of patent application 11.