Polarizing element, polarizing plate, and display device including the same

Abstract

A polarizing element which contains, in the form of a free acid: an azo compound represented by formula (1) or a salt thereof, or an azo compound represented by formula (2) or a salt thereof; and an azo compound represented by formula (3) or a salt thereof.

Description

[Technical Field]

[0001] The present invention relates to a dye-based polarizing element, a polarizing plate, and a display device including the same. [Background technology]

[0002] Polarizing elements are generally manufactured by adsorbing and orienting a dichroic pigment, such as iodine or a dichroic dye, onto a polyvinyl alcohol-based resin film. A polarizing plate obtained by laminating a protective film, such as triacetyl cellulose, to this polarizing element via an adhesive layer is used in liquid crystal display devices and the like. Polarizing plates manufactured using iodine as the dichroic pigment are called iodine-based polarizing plates, while polarizing plates manufactured using a dichroic dye, such as a dichroic azo compound, as the dichroic pigment are called dye-based polarizing plates. Dye-based polarizing plates are characterized by high heat resistance, high humidity and heat durability, and high stability, as well as high color selectivity due to the dye blend. However, they suffer from lower transmittance and contrast compared to iodine-based polarizing plates with the same polarization degree. Therefore, there is a demand for polarizing elements that maintain high durability, have diverse color selectivity, and exhibit higher transmittance and excellent polarization characteristics.

[0003] Furthermore, even with dye-based polarizing plates that offer diverse color selectivity, conventional polarizing elements have a problem in that when two polarizing elements are stacked so that their absorption axis directions are parallel to each other (hereinafter also referred to as "parallel position") to display white (hereinafter also referred to as "white display" or "bright display"), the white appears yellowish. Furthermore, even with polarizing elements manufactured to suppress this yellowish tint, conventional polarizing plates have a problem in that when two polarizing elements are stacked so that their absorption axis directions are perpendicular to each other (hereinafter also referred to as "orthogonal position") to display black (hereinafter also referred to as "black display" or "dark display"), the black appears blue. Therefore, there has been a demand for a polarizing plate that displays achromatic white when displayed white and black when displayed black. It has been particularly difficult to obtain a polarizing plate that displays high-quality white when displayed white, commonly known as a paper-white polarizing plate. Furthermore, for a polarizing plate to be achromatic, the transmittance for each wavelength in the parallel and perpendicular directions must be approximately constant regardless of the wavelength, but it has not been possible to obtain such a polarizing plate until now.

[0004] The reason for the difference in hue between white and black is that the wavelength dependence of transmittance is not the same in the parallel and perpendicular orientations, and in particular, the transmittance is not constant across the visible light range.Furthermore, the fact that dichroism is not constant across the visible light range is also one of the reasons why it is difficult to realize an achromatic polarizer.

[0005] Taking an iodine-based polarizing plate as an example, an iodine-based polarizing plate made of polyvinyl alcohol (hereinafter also referred to as "PVA") as a base material and using iodine as a dichroic dye generally has absorption in the region centered at 480 nm and 600 nm. The absorption at 480 nm is due to the polyiodine I3 - and PVA complex, the absorption at 600 nm is polyiodine I5 - It is said that this is due to the complex between polyiodine I5 and PVA. The degree of polarization (dichroism) at each wavelength is - The polarization (dichroism) based on the complex of polyiodine I3 with PVA is -The polarization degree (dichroism) is higher than that based on a complex of iodine and PVA. In other words, if the cross-phase transmittance is maintained constant at each wavelength, the parallel-phase transmittance is higher at 600 nm than at 480 nm, resulting in a yellowish coloration of white when displayed in white. Conversely, if the parallel-phase transmittance is maintained constant, the cross-phase transmittance is lower at 600 nm than at 480 nm, resulting in a blueish coloration of black when displayed in black. A yellowish coloration of white when displayed in white is generally undesirable, as it gives the impression of advanced deterioration. Furthermore, if the blue color fades when displayed in black, the black is not clearly black, giving the impression of lacking luxury. Furthermore, with iodine-based polarizers, hue control is difficult due to the lack of complexes based on wavelengths around 550 nm, where luminosity is high. Thus, the inconsistent polarization degree (dichroism) at each wavelength results in wavelength-dependent polarization degree (dichroism). Furthermore, since there are only two dichroic dyes, 480 nm and 600 nm, which are absorbed by the complex of iodine and PVA, it is not possible to adjust the hue with an iodine-based polarizing plate made of iodine and PVA.

[0006] Methods for improving the hue of iodine-based polarizing plates are described in Patent Documents 1 and 2. Patent Document 1 describes a polarizing plate in which the neutral coefficient is calculated and the absolute value is 0 to 3. Patent Document 2 describes a polarizing element in which the transmittance in the range of 410 nm to 750 nm is set to within ±30% of the average value, and the color is adjusted by adding a direct dye, a reactive dye, or an acid dye in addition to iodine. Patent Document 3 also discloses a technology for an achromatic dye-based polarizing plate.

[0007] However, as can be seen from Example 1 of Patent Document 1, even though the neutral coefficient (Np) is low, the parallel-phase hue calculated according to JIS Z 8729 is a* value of -1.67 and b* value of 3.51, indicating a yellowish-green appearance in white. Furthermore, the perpendicular-phase hue is a* value of 0.69, but the b* value is -3.40, resulting in a polarizing plate that appears blue in black. The polarizing element of Patent Document 2 is obtained by setting the a* and b* values ​​in the UCS color space measured using only one polarizing element to an absolute value of 2 or less, and is therefore unable to simultaneously express achromatic colors in both white and black hues when two polarizing elements are stacked. Furthermore, the average single transmittance of the polarizing element of Patent Document 2 was low, at 31.95% in Example 1 and 31.41% in Example 2. As described above, the polarizing element of Patent Document 2 has low transmittance and therefore does not have sufficient performance in fields requiring high transmittance and high contrast, particularly in fields such as liquid crystal display devices and organic electroluminescence. Furthermore, because the polarizing element of Patent Document 2 is made using iodine as the main dichroic dye, it shows a large color change after durability tests, particularly after moist heat durability tests (for example, in an environment of 85°C and 85% relative humidity), and its durability is poor.

[0008] On the other hand, dye-based polarizers have excellent durability, but like iodine-based polarizers, their wavelength dependence differs between the parallel and perpendicular orientations. Dichroic azo compounds that exhibit the same hue in both the parallel and perpendicular orientations are virtually nonexistent, and even if they exist, their dichroism (polarization characteristics) is poor. Some dichroic azo compounds exhibit completely different wavelength dependence in the perpendicular and parallel orientations, such as white appearing yellow when displayed white and black appearing blue when displayed black. Furthermore, because human color sensitivity varies depending on the brightness of light, even if color correction of dye-based polarizers is attempted, color correction appropriate for each brightness and darkness of the light generated by controlling polarization in both the perpendicular and parallel orientations is necessary. Achromatic polarizers can only be achieved if their transmittance is approximately constant at each wavelength in both the parallel and perpendicular orientations and is not wavelength-dependent. Furthermore, to obtain a polarizing element with high transmittance and high contrast, it is necessary to simultaneously satisfy a certain transmittance in both the parallel and perpendicular directions, and also to have a high and constant degree of polarization (dichroic ratio) at each wavelength. Even when one azo compound is used to prepare a polarizing element, the wavelength dependence of the transmittance at each wavelength differs between the perpendicular and parallel directions. However, in order to achieve a constant transmittance at each wavelength by blending two or more azo compounds, it is necessary to take into account the parallel and perpendicular transmittance of each compound and precisely control the relationship between the dichroic ratios of the two or more compounds.

[0009] On the other hand, even if the relationship between the transmittance and the dichroic ratio at each wavelength in the parallel and perpendicular directions could be precisely controlled to maintain a constant transmittance at each wavelength, it has not yet been possible to achieve high transmittance and high contrast. In other words, the higher the transmittance or the polarization degree, the more difficult it becomes to achieve achromatic colors, and an achromatic polarizer with high transmittance or polarization degree has not been achieved. Obtaining an achromatic polarizer with high transmittance and / or high contrast is extremely difficult, and it cannot be achieved simply by applying dichroic dyes of the three primary colors. In particular, simultaneously achieving constant transmittance and high dichroism at each wavelength in the parallel direction is extremely difficult. Even a slight inclusion of color prevents the expression of high-quality white. Furthermore, white in the bright state is particularly important because it has high brightness and high sensitivity. Therefore, there is a need for a polarizing element that displays a high-quality achromatic white like paper when displayed white and achromatic black when displayed black, while also having a single-unit transmittance of 35% or more after luminosity correction and a high polarization degree. Patent Document 3 also describes a polarizing plate that is achromatic in both white and black display, but further improvement in performance is desired. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-169024 [Patent Document 2] Japanese Patent Application Publication No. 10-133016 [Patent Document 3] WO2014 / 162635 publication [Patent Document 4] Japanese Patent Application Laid-Open No. 2006-182846 [Patent Document 5] Japanese Patent Application Laid-Open No. 2007-084803 [Patent Document 6] WO2016 / 186194 publication [Patent Document 7] WO2016 / 186195 publication [Patent Document 8] Japanese Patent Application Publication No. 11-218611 [Patent Document 9] Japanese Patent Application Laid-Open No. 2001-033627 [Patent Document 10] Japanese Patent Application Laid-Open No. 2004-251962 [Patent Document 11] Japanese Patent Application Publication No. 8-291259 [Non-patent literature]

[0011] [Non-Patent Document 1] Dye Chemistry; by Yutaka Hosoda, Gihodo Publishing, 1957, 621 pages [Non-patent document 2] Application of Functional Dyes (CMC Publishing Co., Ltd., 1st edition, supervised by Masahiro Irie, pp. 98-100) Summary of the Invention [Problem to be solved by the invention]

[0012] Therefore, one object of the present invention is to provide a polarizing element or polarizing plate having high transmittance and a high degree of polarization, and another object of the present invention is to provide a high-performance polarizing element or polarizing plate and display device that are achromatic in white display or in both white display and black display, and that exhibit high-quality white in white display in particular. [Means for solving the problem]

[0013] As a result of intensive research into solving the above problems, the present inventors have completed the present invention by using an azo compound represented by formula (1) or an azo compound represented by formula (2) and an azo compound represented by formula (3) in the production of a polarizing element or a polarizing plate.

[0014] That is, the present invention relates to the following [Invention 1] to [Invention 17], but is not limited thereto. [Invention 1] A polarizing element comprising an azo compound represented by the following formula (1) or a salt thereof, or an azo compound represented by the following formula (2) or a salt thereof, in the form of a free acid, and an azo compound represented by the following formula (3) or a salt thereof: [ka] (In formula (1), each Ac1 independently represents a phenyl group or a naphthyl group having at least one substituent selected from a sulfo group and a carboxy group; Rc 11 ~Rc 14 each independently represents a hydrogen atom, a C1-4 alkyl group, a C1-4 alkoxy group, or a C1-4 alkoxy group having a sulfo group. [ka] (In formula (2), Ac2 represents a phenyl group or a naphthyl group having at least one substituent selected from a sulfo group and a carboxy group, and Rc 21 ~Rc 28 each independently represents a hydrogen atom, a C1-4 alkyl group, a C1-4 alkoxy group, or a C1-4 alkoxy group having a sulfo group; Xc2 represents an amino group which may have at least one substituent S2, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a naphthotriazole group which may have a substituent, or a benzoylamino group which may have a substituent; the substituents S2 (when there are multiple substituents, each independently) are selected from a C1-4 alkyl group which may have a further substituent, a C1-4 alkoxy group, a sulfo group, a C1-4 alkylamino group, a hydroxy group, an amino group, a substituted amino group, a carboxy group, and a carboxyethylamino group; and r, p, and q each independently represent 0 or 1. However, except when r, p, and q are all 1, if either p or q is 1 and Ac2 is a naphthyl group, then no hydroxy group is included as a substituent. [ka] (In formula (3), Ra1, Ra2, Ab1, or Ab2 is substituted with either ring a or ring b; one of Ra1 or Ra2 is a hydroxy group, and the other represents a hydrogen atom, a hydroxy group, a C1-4 alkoxy group, or a C1-4 alkoxy group having a sulfo group; one of Ab1 or Ab2 represents a sulfo group, a carboxy group, or an amino group which may have a substituent; and the other represents a hydrogen atom, a sulfo group, a carboxy group, or an amino group which may have a substituent; and Rb1 to Rb6 each independently represent a hydrogen atom, a C1-4 alkyl group, a C1-4 alkoxy group, a sulfo group, or a sulfo group. Xb1 represents an amino group which may have at least one substituent S3, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a naphthotriazole group which may have a substituent, or a benzoylamino group which may have a substituent, and the substituents S3 (when there are multiple S3, each independently) are further selected from a C1-4 alkyl group which may have a substituent, a C1-4 alkoxy group, a sulfo group, an amino group, a C1-4 alkylamino group, a hydroxy group, a carboxy group, and a carboxyethylamino group. [Invention 2] The polarizing element according to invention 1, further comprising an azo compound represented by the following formula (4) or a salt thereof, or an azo compound represented by the following formula (5) or a salt thereof: [ka] (In equation (4), Ay 11 each independently represents a sulfo group, a carboxy group, a hydroxy group, a C1-4 alkyl group, or a C1-4 alkoxy group; Ry 11 ~Ry 14 each independently represents a hydrogen atom, a C1-4 alkyl group, a C1-4 alkoxy group, or a C1-4 alkoxy group having a sulfo group, and f represents an integer of 1 to 3. [ka] (In equation (5), Ay 21 and Ay22 each independently represents a naphthyl group which may have a substituent or a phenyl group which may have a substituent, and Ry 21 , Ry 22 , Ry 27 , and Ry 28 are each independently a hydrogen atom, a C1-4 alkyl group, or a C1-4 alkoxy group, and Ry 23 ~Ry 26 each independently represents a hydrogen atom, a C1-4 alkyl group, a C1-4 alkoxy group, or a C1-4 alkoxy group having a sulfo group, and s and t each independently represent 0 or 1. [Invention 3] 3. The polarizing element according to claim 1, wherein the azo compound represented by formula (3) or a salt thereof is an azo compound represented by formula (6) below or a salt thereof: [ka] (In formula (6), Ra1, Ra2, Ab1, Ab2, Rb1 to Rb6, h, and Xb1 have the same meanings as in formula (3).) [Invention 4] 4. The polarizing element according to any one of inventions 1 to 3, wherein the azo compound represented by formula (3) or a salt thereof is an azo compound represented by formula (7) below or a salt thereof: [ka] (In formula (7), Ra1, Ra2, Ab1, Ab2, Rb1 to Rb6, h, and Xb1 have the same meanings as in formula (3).) [Invention 5] 5. The polarizing element according to any one of items 1 to 4, wherein the azo compound represented by formula (3) or the salt thereof is an azo compound represented by formula (8) below or a salt thereof: [ka] (In formula (8), Ra1, Ab1, Rb1 to Rb6, h, and Xb1 each have the same meaning as in formula (3), and Ra3 represents a hydrogen atom or a hydroxy group.) [Invention 6] 6. The polarizing element according to any one of inventions 1 to 5, wherein the azo compound represented by formula (3) or a salt thereof is an azo compound represented by formula (9) below or a salt thereof: [ka] (In the formula (9), Ra1, Ab1, Rb1 to Rb6, h, and Xb1 each have the same meaning as in the formula (2).) [Invention 7] The polarizing element according to any one of Inventions 1 to 6, wherein, in the transmittance at each wavelength determined by measuring two polarizing elements stacked so that the absorption axis directions of the respective elements are parallel to each other, the difference in absolute value between the average transmittance at 420 nm to 480 nm and the average transmittance at 520 nm to 590 nm is 2.5% or less, and the difference in absolute value between the average transmittance at 520 nm to 590 nm and the average transmittance at 600 nm to 640 nm is 3.0% or less. [Invention 8] The polarizing element according to any one of Inventions 1 to 7, wherein the absolute values ​​of the a* value and b* value of the polarizing element alone, as determined when the transmittance is measured using natural light according to JIS Z 8781-4:2013, are both 1.0 or less. [Invention 9] The polarizing element according to any one of Inventions 1 to 8, wherein when two polarizing elements are stacked so that the absorption axis directions of the respective polarizing elements are parallel to each other, the a* value determined by transmittance measurement using natural light in accordance with JIS Z 8781-4:2013 is -2.0 to 2.0 and the absolute value of the b* value is -2.0 to 3.0. [Invention 10] The polarizing element according to any one of Inventions 1 to 9, wherein the polarizing element has a single transmittance of 35% to 65% after luminosity correction, and when two polarizing elements are stacked and arranged so that the absorption axis directions of the respective polarizing elements are parallel to each other, the average transmittance in the wavelength band of 520 nm to 590 nm is 25% to 50%. [Invention 11] The polarizing element according to any one of Inventions 1 to 10, wherein, when two polarizing elements are stacked so that the absorption axis directions of the respective polarizing elements are perpendicular to each other, the difference between the average transmittance in the range of 420 nm to 480 nm and the average transmittance in the range of 520 nm to 590 nm is 1.0% or less in absolute value, and the difference between the average transmittance in the range of 520 nm to 590 nm and the average transmittance in the range of 600 nm to 640 nm is 1.0% or less in absolute value. [Invention 12] The polarizing element according to any one of Inventions 1 to 11, wherein when two polarizing elements are stacked so that the absorption axis directions of the two polarizing elements are perpendicular to each other, the orthogonal transmittance at each wavelength in the wavelength bands of 420 nm to 480 nm, 520 nm to 590 nm, and 600 nm to 640 nm is 1% or less, or the degree of polarization after luminous efficiency correction is 97% or more. [Invention 13] The polarizing element according to any one of Inventions 1 to 12, wherein when two polarizing elements are stacked so that the absorption axis directions of the respective polarizing elements are perpendicular to each other, the absolute values ​​of the a* value and the b* value when the transmittance is measured using natural light in accordance with JIS Z 8781-4:2013 are both 2.0 or less. [Invention 14] 14. The polarizing element according to any one of claims 1 to 13, comprising a substrate. [Invention 15] 15. The polarizing element according to claim 14, comprising a polyvinyl alcohol-based resin film as a substrate. [Invention 16] 16. A polarizing plate comprising the polarizing element according to any one of Inventions 1 to 15, and a transparent protective layer provided on one or both sides of the polarizing element. [Invention 17] A display device comprising the polarizing element according to any one of Inventions 1 to 15 or the polarizing plate according to Invention 16. [Effects of the Invention]

[0015] The polarizing element or polarizing plate thereof of the present invention has high transmittance and high polarization degree. In another aspect, the polarizing element of the present invention further has the property that the dichroism is wavelength independent in the parallel position or in both the parallel and perpendicular positions, and the transmittance is constant. In another aspect, the polarizing element of the present invention has an achromatic hue in both white display and black display. In another aspect, the polarizing element or polarizing plate thereof of the present invention has high durability. DETAILED DESCRIPTION OF THE INVENTION

[0016] In the present specification and claims, "azo compounds or salts thereof" may be simply referred to as "azo compounds" unless they are clearly in a free form.

[0017] In the claims and specification of the present application, a "substituent" may include a hydrogen atom, and therefore, for convenience, a hydrogen atom is sometimes referred to as a "substituent." "May have a substituent" means that the group may have no substituent. For example, "a phenyl group which may have a substituent" includes both an unsubstituted phenyl group and a phenyl group which has a substituent. Furthermore, unless otherwise specified, the term "lower" in the context of a lower alkyl group, lower alkoxy group, etc., in the present application refers to a group having 1 to 4 carbon atoms (C1-4), preferably 1 to 3 carbon atoms (C1-3).

[0018] Examples of the "C1-4 aliphatic hydrocarbon group" include linear alkyl groups such as a methyl group, an ethyl group, an n-propyl group, and an n-butyl group; branched alkyl groups such as a sec-butyl group and a tert-butyl group; and unsaturated hydrocarbon groups such as a vinyl group.

[0019] Examples of the "C1-4 alkoxy group" include a methoxy group, an ethoxy group, a propoxy group, an n-butoxy group, a sec-butoxy group, and a tert-butoxy group.

[0020] <Polarizing element>

[0021] The polarizing element of the present invention contains an azo compound represented by the above formula (1) or a salt thereof, or an azo compound represented by the formula (2) or a salt thereof, and an azo compound represented by the formula (3) or a salt thereof. The polarizing element of the present invention preferably further contains an azo compound represented by the above formula (4) or an azo compound represented by the formula (5).

[0022] The polarizing element of the present invention preferably includes a substrate, and the azo compound is contained in the substrate. The substrate is preferably a film obtained by forming a hydrophilic polymer capable of adsorbing a dichroic dye, particularly an azo compound. The hydrophilic polymer is not particularly limited, but examples thereof include polyvinyl alcohol-based resins, amylose-based resins, starch-based resins, cellulose-based resins, and polyacrylate-based resins. From the viewpoints of dyeability, processability, and crosslinkability of the dichroic dye, the hydrophilic polymer is most preferably a polyvinyl alcohol-based resin and its derivatives. A polarizing element can be produced by adsorbing an azo compound to the substrate and then applying an orientation treatment such as stretching.

[0023] First, the azo compound represented by the following formula (1) will be described.

[0024] [ka]

[0025] (In formula (1), each Ac1 independently represents a phenyl group or a naphthyl group having at least one substituent selected from a sulfo group and a carboxy group; Rc 11 ~Rc 14 each independently represents a hydrogen atom, a C1-4 alkyl group, a C1-4 alkoxy group, or a C1-4 alkoxy group having a sulfo group.

[0026] In the above formula (1), when Ac1 is a phenyl group, its substituents include sulfo, carboxy, lower alkyl, lower alkoxy, lower alkoxy having a sulfo, nitro, amino, acetylamino, and lower alkylamino-substituted amino groups, and it is preferable that Ac1 has at least one sulfo or carboxy group. When the phenyl group has two or more substituents, at least one of the substituents is sulfo or carboxy, and the other substituents are preferably selected from sulfo, carboxy, lower alkyl, lower alkoxy, lower alkoxy having a sulfo, nitro, amino, acetylamino, and lower alkylamino-substituted amino groups, more preferably sulfo, methyl, ethyl, methoxy, ethoxy, carboxy, nitro, and amino, and particularly preferably sulfo, methyl, methoxy, ethoxy, and carboxy. The lower alkoxy group having a sulfo is preferably a linear alkoxy group, and the substitution position of the sulfo group is preferably the terminal of the alkoxy group. Such a lower alkoxy group having a sulfo group is more preferably a 3-sulfopropoxy group or a 4-sulfobutoxy group, and particularly preferably a 3-sulfopropoxy group. When a phenyl group has a sulfo group as a substituent, the number of sulfo groups is preferably one or two. The substitution position of the sulfo group is not particularly limited, but when there is one sulfo group, the substitution position of the phenyl group is preferably the 4th position, with the azo group being the 1st position. When there are two sulfo groups, a combination of the 2nd and 4th positions on the phenyl group or a combination of the 3rd and 5th positions on the phenyl group is preferred.

[0027] In the above formula (1), when Ac1 is a naphthyl group, its substituents include sulfo, hydroxy, carboxy, and lower alkoxy groups having a sulfo group, and it is preferable that it 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 selected from sulfo, hydroxy, carboxy, and lower alkoxy groups having a sulfo group. The lower alkoxy group having a sulfo group is preferably a linear alkoxy group, and the substitution position of the sulfo group is preferably the terminal of the alkoxy group. Such a lower alkoxy group having a sulfo group is more preferably a 3-sulfopropoxy group or a 4-sulfobutoxy group, and particularly preferably a 3-sulfopropoxy group. When the naphthyl group has two sulfo groups, the substitution positions of the sulfo groups are preferably a combination of the 4th and 8th positions or a combination of the 6th and 8th positions of the naphthyl group, with the azo group being the 2nd position, and a combination of the 6th and 8th positions is more preferable. When the number of sulfo groups substituted on the naphthyl group is three, the substitution positions of the sulfo groups are preferably a combination of the 1st, 3rd and 6th positions, or a combination of the 3rd, 6th and 8th positions.

[0028] In the above formula (1), Rc 11 ~Rc 14 Rc each independently represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group. The lower alkoxy group having a sulfo group is preferably a linear alkoxy group, and the substitution position of the sulfo group is preferably the terminal of the alkoxy group. 11 ~Rc 14 are preferably each independently a hydrogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, a 3-sulfopropoxy group, or a 4-sulfobutoxy group, and particularly preferably a hydrogen atom, a methyl group, a methoxy group, or a 3-sulfopropoxy group. 11 ~Rc 14The substitution position of the phenyl group where Rc is substituted is preferably only the 2-position, only the 5-position, a combination of the 2- and 6-positions, a combination of the 2- and 5-positions, or a combination of the 3- and 5-positions of the phenyl group, and particularly preferably only the 2-position, only the 5-position, or a combination of the 2- and 5-positions. 11 and Rc 12 , Rc 13 and Rc 14 In relation to Rc 11 and Rc 12 or Rc 13 and Rc 14 has one substituent other than a hydrogen atom only at the 2-position or 5-position, and the other is a hydrogen atom.

[0029] Among the azo compounds represented by the above formula (1), the azo compound represented by the following formula (1b) is particularly preferred. By using such an azo compound, the polarization performance of the polarizing element can be further improved.

[0030] [ka] (In the formula, Ac1, Rc 11 ~Rc 14 have the same meaning as in formula (1).

[0031] The azo compound represented by the above formula (1) or the azo compound represented by the formula (1b) can be produced by known diazotization or ureidation methods as described in, for example, Patent Documents 4 to 7, but is not limited thereto.

[0032] Specific examples of the azo compound represented by formula (1) include the following azo compounds in the form of free acids:

[0033] [ka]

[0034] [ka]

[0035] [ka]

[0036] [ka]

[0037] Next, the azo compound represented by formula (2) will be described.

[0038] [ka]

[0039] In formula (2), Ac2 represents a phenyl group or a naphthyl group having at least one substituent selected from a sulfo group and a carboxy group, and Rc 21 ~Rc 28 each independently represents a hydrogen atom, a C1-4 alkyl group, a C1-4 alkoxy group, or a C1-4 alkoxy group having a sulfo group; Xc2 represents an amino group which may have at least one substituent S2, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a naphthotriazole group which may have a substituent, or a benzoylamino group which may have a substituent; the substituents S2 (when there are multiple S2, each independently) are selected from a C1-4 alkyl group, a C1-4 alkoxy group, a sulfo group, a C1-4 alkylamino group, a hydroxy group, an amino group, a substituted amino group, a carboxy group, and a carboxyethylamino group; r, p, and q each independently represent 0 or 1, except when r, p, and q are all 1, and if only one of p and q is 1 and Ac2 is a naphthyl group, then no hydroxy group is included as a substituent.

[0040] In the above formula (2), when Ac2 is a phenyl group having a substituent, the substituent on the phenyl group may be a sulfo group, a carboxy group, a C1-4 alkyl group, a C1-4 alkoxy group, a C1-4 alkoxy group having a sulfo group, a hydroxy group, a nitro group, an amino group, or a substituted amino group (particularly, an acetylamino group or a C1-4 alkylamino group), and it is preferable that the phenyl group has at least one sulfo group or carboxy group. When the phenyl group has two or more substituents, at least one of the substituents is preferably a sulfo group or a carboxy group, and the other substituents are preferably a sulfo group, a carboxy group, a C1-4 alkyl group, a C1-4 alkoxy group, a C1-4 alkoxy group having a sulfo group, a hydroxy group, a nitro group, an amino group, or a substituted amino group (particularly, an acetylamino group or a C1-4 alkylamino group). The other substituents are more preferably a sulfo group, a carboxy group, a methyl group, an ethyl group, a methoxy group, an ethoxy group, a hydroxy group, a nitro group, or an amino group, and particularly preferably a sulfo group, a carboxy group, a methyl group, a methoxy group, or an ethoxy group. Furthermore, the C1-4 alkoxy group having a sulfo group is preferably a linear alkoxy group, and the substitution position of the sulfo group is preferably the terminal of the alkoxy group. The C1-4 alkoxy group having a sulfo group is more preferably a 3-sulfopropoxy group or a 4-sulfobutoxy group, and particularly preferably a 3-sulfopropoxy group. The number of substituents on the phenyl group is preferably 1 or 2, and the positions of the substituents on the phenyl group are not particularly limited, but are preferably only the 4-position, or a combination of the 2- and 4-positions, or a combination of the 3- and 5-positions.

[0041] In the above formula (2), when Ac2 is a naphthyl group having a substituent, the naphthyl group is preferably selected from a sulfo group, a hydroxy group, a carboxy group, or a C1-4 alkoxy group having a sulfo group as a substituent, and preferably has at least one sulfo group. When the naphthyl group has two or more substituents, it is preferable that at least one of the substituents is a sulfo group, and the other substituents are a sulfo group, a hydroxy group, a carboxy group, or a C1-4 alkoxy group having a sulfo group. Furthermore, the C1-4 alkoxy group having a sulfo group is preferably a linear alkoxy group, and the substitution position of the sulfo group is preferably the terminal of the alkoxy group. The C1-4 alkoxy group having a sulfo group is more preferably a 3-sulfopropoxy group or a 4-sulfobutoxy group, and particularly preferably a 3-sulfopropoxy group. When the number of sulfo groups on the naphthyl group is 2, the substitution positions of the sulfo groups are preferably a combination of positions 4 and 8 or a combination of positions 6 and 8, and particularly preferably a combination of positions 6 and 8, assuming that the substitution position of the azo group is position 2. When the number of sulfo groups on the naphthyl group is 3, the substitution positions of the sulfo groups are preferably a combination of positions 1, 3 and 6, or a combination of positions 3, 6 and 8, assuming that the substitution position of the azo group is position 2.

[0042] In the above formula (2), Xc2 represents an amino group which may have at least one substituent S2, a phenylamino group which may have at least one substituent, a phenylazo group which may have at least one substituent, a naphthotriazole group which may have at least one substituent, a benzoyl group which may have at least one substituent, or a benzoylamino group which may have at least one substituent, and preferably includes a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a naphthotriazole group which may have a substituent, a benzoyl group which may have a substituent, or a benzoylamino group which may have a substituent, and particularly preferred Xc2 includes a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, or a benzoylamino group which may have a substituent. The substituent is selected from a lower alkyl group, a lower alkoxy group, a sulfo group, a lower alkylamino group, a hydroxy group, an amino group, a substituted amino group, a carboxy group, and a carboxyethylamino group.

[0043] When Xc2 is an amino group which may have at least one substituent S2, the amino group may be unsubstituted but preferably has one or two substituents selected from a lower alkyl group, a lower alkoxy group, a sulfo group, a carboxy group, an amino group, a substituted amino group, and a lower alkylamino group, and more preferably has one or two substituents selected from a methyl group, a methoxy group, a sulfo group, a carboxy group, an amino group, and a lower alkylamino group.

[0044] When Xc2 is a phenylamino group which may have at least one substituent, the phenylamino group is unsubstituted or preferably has one or two substituents selected from a lower alkyl group, a lower alkoxy group, a sulfo group, an amino group, and a lower alkylamino group, more preferably has one or two substituents selected from a methyl group, a methoxy group, a sulfo group, and an amino group.

[0045] When Xc2 is a phenylazo group which may have at least one substituent, the phenylazo group is unsubstituted or preferably has 1 to 3 substituents selected from a hydroxy group, a lower alkyl group, a lower alkoxy group, an amino group, and a carboxyethylamino group, more preferably has 1 to 3 substituents selected from a methyl group, a methoxy group, a carboxyethylamino group, an amino group, and a hydroxy group.

[0046] When Xc2 is a naphthotriazole group which may have at least one substituent, the naphthotriazole group is unsubstituted or preferably has one or two substituents selected from a sulfo group, an amino group, and a carboxy group, and more preferably has one or two sulfo groups as substituents.

[0047] When Xc2 is a benzoylamino group optionally having at least one of the above-mentioned substituents, the benzoylamino group is unsubstituted or preferably has one substituent selected from a hydroxy group, an amino group, and a carboxyethylamino group, and more preferably has one or two hydroxy groups or amino groups as substituents.

[0048] When Xc2 is a benzoylamino group which may have at least one substituent, the benzoyl moiety is unsubstituted or preferably has one substituent selected from a hydroxy group, an amino group, and a carboxyethylamino group, and more preferably has one or two hydroxy groups or amino groups as substituents.

[0049] The substitution positions of the substituents that the phenylamino group, phenylazo group, and benzoylamino group may have are not particularly limited, but one of the substituents is preferably at the p-position relative to the amino group, azo group, or amide group, respectively. The substitution position of Xc2 is preferably the 6th or 7th position, more preferably the 6th position, when the position of the hydroxy group of the substituting naphthyl group is taken as the 1st position.

[0050] In the above formula (2), Rc 21~Rc 28 Rc each independently represents a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group. 21 ~Rc 28 are each independently preferably a hydrogen atom, a C1-4 alkyl group, a C1-4 alkoxy group, or a linear alkoxy group having a terminal sulfo group, more preferably a hydrogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, a 3-sulfopropoxy group, or a 4-sulfobutoxy group, and particularly preferably a hydrogen atom, a methyl group, a methoxy group, or a 3-sulfopropoxy group.

[0051] In the above formula (2), particularly Rc 27 , Rc 28 are each independently preferably a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group, which allows for high transmittance and a high polarization degree, more preferably a hydrogen atom, a C1-3 alkyl group, or a C1-3 alkoxy group, further preferably a hydrogen atom, a methyl group, an ethyl group, a methoxy group, or an ethoxy group, and particularly preferably a hydrogen atom, a methyl group, or a methoxy group.

[0052] In the above formula (2), r, p, and q each independently represent 0 or 1. To obtain good polarization performance in the polarizing element of the present invention, when one of p and q is 0, it is preferable that the other is 1, and it is more preferable that both p and q are 1. Furthermore, to obtain even better polarization properties, it is preferable that r is 1 and either p or q, or both, are 0. When r, p, and q are all 1, the inclusion property in the substrate, for example, the dyeability of a polyvinyl alcohol film, may be reduced.

[0053] Among the azo compounds represented by the above formula (2), the azo compound represented by the following formula (2b) is preferred: By using such an azo compound, the polarization performance of the polarizing element can be further improved.

[0054] [ka] (In formula (2b), Ac2, Rc 21 ~Rc 28 , Xc2, r, p, and q each have the same meaning as in formula (2).

[0055] Next, specific examples of the azo compound represented by formula (2) are listed below. The following compound examples are represented in the form of free acid.

[0056] [ka]

[0057] [ka]

[0058] [ka]

[0059] [ka]

[0060] [ka]

[0061] [ka]

[0062] [ka]

[0063] [ka]

[0064] [ka]

[0065] [ka]

[0066] [ka]

[0067] [ka]

[0068] [ka]

[0069] [ka]

[0070] [ka]

[0071] Examples of the azo compound whose free acid form is represented by formula (2) and the azo compound represented by formula (2b) include CI Direct Red 117, CI Direct Red 127, and the azo compounds described in JP-A-3-12606, JP-A-8-291259, JP-A-9-302250, JP-A-2002-275381, WO 2005 / 075572, WO 2012 / 108169, and WO 2012 / 108173.

[0072] Examples of methods for synthesizing the azo compound represented by formula (2) and the azo compound represented by formula (2b) include, but are not limited to, methods described in JP-A-3-12606, JP-A-8-291259, JP-A-9-302250, JP-A-2002-275381, WO 2005 / 075572, WO 2012 / 108169, and WO 2012 / 108173.

[0073] Next, the azo compound represented by the following formula (3) will be described.

[0074] [ka]

[0075] (In formula (3), Ra1, Ra2, Ab1, and Ab2 are substituted with either ring a or ring b, one of Ra1 and Ra2 is a hydroxy group, and the other is a hydrogen atom, a hydroxy group, a C1-4 alkoxy group, or a C1-4 alkoxy group having a sulfo group, Ab1 and Ab2 are substituents selected from a hydrogen atom, a sulfo group, a carboxy group, or an optionally substituted amino group, and Ab1 or Ab 2の one of them represents a sulfo group, a carboxy group, or an amino group which may have a substituent; Rb1 to Rb6 each independently represent a hydrogen atom, a C1-4 alkyl group, a C1-4 alkoxy group, a sulfo group, a C1-4 alkoxy group having a sulfo group, or an amino group which may have a substituent; h represents 0 or 1; Xb1 represents an amino group which may have at least one substituent S3, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a naphthotriazole group which may have a substituent, or a benzoylamino group which may have a substituent; and the substituents S3 (when there are multiple S3, each independently) are further selected from the group consisting of a C1-4 alkyl group, a C1-4 alkoxy group, a sulfo group, an amino group, a C1-4 alkylamino group, a hydroxy group, a carboxy group, and a carboxyethylamino group.

[0076] The "amino group which may have a substituent" which Rb1 to Rb6 may have is preferably an unsubstituted amino group or an amino group having one or two substituents (C1-4 alkyl group, acetyl group).

[0077] The amino group which may have a substituent S3 is preferably an unsubstituted amino group or an amino group having one or two C1-4 alkyl groups which may have substituents (hydroxy, methoxy, ethoxy, amino, carboxy, sulfo, or phenyl), more preferably a hydrogen atom or an amino group having one or two methyl groups. The phenylamino group which may have a substituent is preferably a phenylamino group having one or two substituents selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, a carboxy group, an amino group, and a lower alkylamino group, 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, a carboxy group, and an amino group. The phenylazo group which may have a substituent is preferably a phenylazo group having one to three substituents selected from the group consisting of a hydrogen atom, a hydroxy group, a C1-4 alkyl group, a C1-4 alkoxy group, an amino group, a hydroxy group, and a carboxyethylamino group. The optionally substituted benzoylamino group is preferably a benzoylamino group having one substituent selected from the group consisting of a hydrogen atom, a hydroxy group, an amino group, and a carboxyethylamino group. The optionally substituted naphthotriazole group is unsubstituted or preferably has one or two substituents selected from the group consisting of a sulfo group, an amino group, and a carboxy group, more preferably has one or two sulfo groups as substituents.

[0078] The substitution positions of the substituents that the phenylamino group, phenylazo group, and benzoylamino group may have are not particularly limited, but one of the substituents is preferably at the p-position relative to the amino group, azo group, or amide group, respectively. The substitution position of Xb1 is preferably the 6th or 7th position, more preferably the 6th position, when the position of the hydroxy group of the substituting naphthyl group is taken as the 1st position.

[0079] When the azo compound represented by formula (3) above is an azo compound represented by formula (6) below, the transmittance at 550 nm to 700 nm in the parallel position is further improved, and a polarizing element with a high degree of polarization can be provided. An azo compound represented by formula (7) is more preferred, an azo compound represented by formula (8) is even more preferred, an azo compound represented by formula (9) is even more preferred, and an azo compound represented by formula (10) is particularly preferred. In formulas (3) and (6) to (10), when Xb1 is an amino group optionally having at least one substituent S3, it is more preferred that Xb1 be an amino group optionally having at least one substituent different from Ra1, Ra2, Ab1, or Ab2.

[0080] [ka] (In the above formula (6), Ra1, Ra2, Ab1, Ab2, Rb1 to Rb6, h, and Xb1 each have the same meaning as in formula (3).)

[0081] [ka] (In formula (7), Ra1, Ra2, Ab1, Ab2, Rb1 to Rb6, h, and Xb1 have the same meanings as in formula (3).)

[0082] [ka] (In formula (8), Ra1, Ab1, Rb1 to Rb6, h, and Xb1 have the same meanings as in formula (3).)

[0083] [ka] (In formula (9), Ra1, Ab1, Rb1 to Rb6, h, and Xb1 have the same meanings as in formula (3).)

[0084] [ka] (In formula (10), Ab1, Rb1 to Rb6, h, and Xb1 each have the same meaning as in formula (3).)

[0085] The azo compound represented by the above formula (3) can be easily produced by known diazotization and coupling processes according to the production method of a normal azo dye as described in Non-Patent Document 1. The synthesis method will be illustrated using the azo compound represented by formula (6) where h=0 as an example.

[0086] First, an amine represented by formula (A) is diazotized by a known method such as that described in Non-Patent Document 1, and then subjected to primary coupling with an aniline represented by formula (B) below to obtain a monoazoamino compound represented by formula (C) below.

[0087] [ka] (In formulas (A) to (C), Ra1, Ra2, Ab1, Ab2, Rb1, and Rb2 each have the same meaning as in formula (3).)

[0088] Next, this monoazoamino compound (C) is diazotized by a known method such as that described in Non-Patent Document 1, and subjected to secondary coupling with an aniline of the following formula (D) to obtain a disazoamino compound represented by the following formula (E).

[0089] [ka] (In formulas (D) and (E), Ra1, Ra2, Ab1, Ab2, and Rb1 to Rb4 each have the same meaning as in formula (3).)

[0090] The azo compound of formula (3) can be obtained by diazotizing the compound of formula (E) by a known method such as that described in Non-Patent Document 1 and coupling it with a naphthol represented by the following formula (F).

[0091] [ka] (In formula (F), Xb1 has the same meaning as in formula (3).)

[0092] In the above reaction, the diazotization step can be carried out either by the conventional method of mixing a nitrite such as sodium nitrite with an aqueous solution or suspension of the diazo component in a mineral acid such as hydrochloric acid or sulfuric acid, or by the inverse method of adding a nitrite to a neutral or weakly alkaline aqueous solution of the diazo component and then mixing this with a mineral acid. The diazotization temperature is preferably -10 to 40°C. The coupling step with anilines is carried out by mixing each of the above diazo solutions with an acidic aqueous solution such as hydrochloric acid or acetic acid, under acidic conditions at a temperature of -10 to 40°C and a pH of 2 to 7.

[0093] The monoazo compound or disazo compound obtained by coupling can be directly or precipitated by acid precipitation or salting out and filtered, or can be carried to the next step as a solution or suspension. If the monoazo compound or disazo compound obtained by coupling is poorly soluble and in the form of a suspension, it can be filtered and used as a press cake in the next coupling step.

[0094] The coupling reaction between the diazotized disazo compound and the naphthol represented by formula (F) is carried out at a temperature of -10 to 40°C under neutral to alkaline conditions at a pH of 7 to 10. After completion of the reaction, the product is precipitated by salting out and filtered. If purification is required, the salting out can be repeated or an organic solvent can be used to precipitate the product from water. Examples of organic solvents used for purification include water-soluble organic solvents such as alcohols such as methanol and ethanol, and ketones such as acetone.

[0095] The starting material for synthesizing the azo compound represented by formula (3) is a naphthylamine compound corresponding to the substituted naphthyl group represented by formula (A). Examples of naphthylamines of formula (A) include 2-amino-1-hydroxy-naphthalene-6-sulfonic acid, 3-amino-1-hydroxy-naphthalene-6-sulfonic acid, 2-amino-1-hydroxy-naphthalene-3,6-disulfonic acid, 2-amino-8-hydroxy-naphthalene-6-sulfonic acid, 3-amino-8-hydroxy-naphthalene-6-sulfonic acid, 2-amino-8-hydroxy-naphthalene-3,6-disulfonic acid, 2-amino-1,8-dihydroxy-naphthalene-6-sulfonic acid, and 3-amino-1,8-dihydroxy-naphthalene-6 -sulfonic acid, 2-amino-1,8-dihydroxy-naphthalene-3,6-disulfonic acid, 2-amino-1,8-dihydroxy-naphthalene-3-sulfonic acid, 2-amino-1,8-dihydroxy-naphthalene-3,6-disulfonic acid, 2-amino-1-methoxy-8-hydroxy-naphthalene-6-sulfonic acid, 3-amino-1-methoxy-8-hydroxy-naphthalene-6-sulfonic acid, 2-amino-1-methoxy-8-hydroxy-naphthalene-3-sulfonic acid, 2-amino-1-methoxy-8-hydroxy-naphthalene-3,6-disulfonic acid, 2-Amino-1-hydroxy-8-methoxy-naphthalene-6-sulfonic acid, 3-Amino-1-hydroxy-8-methoxy-naphthalene-6-sulfonic acid, 2-Amino-1-hydroxy-8-methoxy-naphthalene-3-sulfonic acid, 3-Amino-1-hydroxy-8-methoxy-naphthalene-6-sulfonic acid, 2-Amino-1-hydroxy-8-methoxy-naphthalene-3,6-disulfonic acid, 2-Amino-1-hydroxy-8-(3-sulfopropoxy)-naphthalene-3-sulfonic acid, 2-Amino-1-hydroxy-8-(4-sulfo butoxy)-naphthalene-3-sulfonic acid, 2-amino-1-(3-sulfopropoxy)-8-hydroxy-naphthalene-3-sulfonic acid, 2-amino-1-(4-sulfobutoxy)-8-hydroxy-naphthalene-3-sulfonic acid, 2-amino-1-hydroxy-8-(3-sulfopropoxy)-naphthalene-6-sulfonic acid, 2-amino-1-hydroxy-8-(4-sulfobutoxy)-naphthalene-6-sulfonic acid, 2-amino-1-(3-sulfopropoxy)-8-hydroxy-naphthalene-3,6-disulfonic acid, 2-amino-1- (4-Sulfobutoxy)-8-hydroxy-naphthalene-3,6-disulfonic acid, 2-amino-1,8-dihydroxy-naphthalene-6-aminomethyl-3-disulfonic acid, etc. are preferred, and more preferred are 2-amino-1,8-dihydroxy-naphthalene-6-sulfonic acid, 2-amino-1,8-dihydroxy-naphthalene-3-sulfonic acid, 2-amino-1,8-dihydroxy-naphthalene-3,6-disulfonic acid, 2-amino-1-methoxy-8-hydroxy-naphthalene-6-sulfonic acid, 2-amino-1-methoxy- Examples of sulfonic acids include, but are not limited to, 8-hydroxy-naphthalene-3,6-disulfonic acid, 2-amino-1-hydroxy-8-methoxy-naphthalene-6-sulfonic acid, 2-amino-1-hydroxy-8-methoxy-naphthalene-3-sulfonic acid, 2-amino-1-hydroxy-8-methoxy-naphthalene-3,6-disulfonic acid, 2-amino-1-hydroxy-8-(3-sulfopropoxy)-naphthalene-3-sulfonic acid, and 2-amino-1-(3-sulfopropoxy)-8-hydroxy-naphthalene-3,6-disulfonic acid.

[0096] Examples of anilines having substituents (Rb1 to Rb6) which are primary and secondary coupling components when h is 0, or primary to tertiary coupling components when h is 1 include aniline, 2-methylaniline, 2-ethylaniline, 2-propylaniline, 2-butylaniline, 3-methylaniline, 3-ethylaniline, 3-propylaniline, 3-butylaniline, 2,5-dimethylaniline, 2,5-diethylaniline, 2-methoxyaniline, 2-ethoxyaniline, 2-propoxyaniline, 2-butoxyaniline, 3-methoxyaniline, 3-ethoxyaniline, 3-propoxyaniline, 3-butoxyaniline, 2-methoxy-5-methylaniline, 2,5-dimethoxyaniline, 3,5-dimethylaniline, 2,6-dimethylaniline, 3,5-Dimethoxyaniline, 3-(2-amino-4-methylphenoxy)propane-1-sulfonic acid, 3-(2-aminophenoxy)propane-1-sulfonic acid, 4-(2-amino-4-methylphenoxy)butane-1-sulfonic acid, 4-(2-aminophenoxy)butane-1-sulfonic acid, 2-(2-amino-4-methylphenoxy)ethane-1-sulfonic acid, 2-(2-aminophenoxy)ethane-1-sulfonic acid, 3-(3-amino- 4-methylphenoxy)propane-1-sulfonic acid, 3-(3-aminophenoxy)propane-1-sulfonic acid, 4-(3-amino-4-methylphenoxy)butane-1-sulfonic acid, 4-(3-aminophenoxy)butane-1-sulfonic acid, 2-(3-amino-4-methylphenoxy)ethane-1-sulfonic acid, 2-(3-aminophenoxy)ethane-1-sulfonic acid, 3-(2-amino-4-methoxyphenoxy)propane-1-sulfonic acid 4-(2-amino-4-methoxyphenoxy)butane-1-sulfonic acid, 2-(2-amino-4-methoxyphenoxy)ethane-1-sulfonic acid, 3-(3-amino-4-methoxyphenoxy)propane-1-sulfonic acid, 4-(3-amino-4-methoxyphenoxy)butane-1-sulfonic acid, 2-(3-amino-4-methoxyphenoxy)ethane-1-sulfonic acid, 3-(2-amino-4-ethoxyphenoxy)propane-1-sulfonic acid Examples of suitable aromatic amines include, but are not limited to, sulfonic acid, 4-(2-amino-4-ethoxyphenoxy)butane-1-sulfonic acid, 2-(2-amino-4-ethoxyphenoxy)ethane-1-sulfonic acid, 3-(3-amino-4-ethoxyphenoxy)propane-1-sulfonic acid, 4-(3-amino-4-ethoxyphenoxy)butane-1-sulfonic acid, and 2-(3-amino-4-ethoxyphenoxy)ethane-1-sulfonic acid. The amino group of these aromatic amines may be protected. Examples of the protecting group include an ω-methanesulfonic group.

[0097] Examples of naphthols having Xb1, which is a tertiary coupling component when h is 0 or a quaternary coupling component when h is 1, include, but are not limited to, 6-amino-3-sulfonic acid-1-naphthol, 6-methylamino-3-sulfonic acid-1-naphthol, 6-phenylamino-3-sulfonic acid-1-naphthol, 6-(4-methoxy-phenylamino)-3-sulfonic acid-1-naphthol, 6-benzoylamino-3-sulfonic acid-1-naphthol, and 6-(4'-aminobenzoyl)amino-3-sulfonic acid-1-naphthol.

[0098] Specific examples of the azo compound represented by formula (3) are listed below. The azo compound is represented in the form of a free acid.

[0099] [ka]

[0100] [ka]

[0101] [ka]

[0102] [ka]

[0103] [ka]

[0104] [ka]

[0105] [ka]

[0106] [ka]

[0107] [ka]

[0108] The polarizing element of the present invention provides a polarizing element or polarizing plate having higher transmittance and a higher degree of polarization than conventional dye-based polarizing plates by combining an azo compound represented by formula (1) or an azo compound represented by formula (2) with an azo compound represented by formula (3). Furthermore, while having higher transmittance and a higher degree of polarization than conventional polarizing plates, it can achieve a high-quality paper-like white color (commonly known as paper white) when displaying white, and can achieve achromatic black, particularly a clear black with a luxurious feel, when displaying black, and can have a higher contrast than conventional dye-based polarizing elements or dye-based polarizing plates.

[0109] The polarizing element of the present invention can obtain a polarizing element or polarizing plate with even higher transmittance and a higher degree of polarization by further including an azo compound represented by formula (4) or an azo compound represented by formula (5) in addition to an azo compound represented by formula (1) or an azo compound represented by formula (2) and an azo compound represented by formula (3). In particular, by including an azo compound represented by formula (4) or formula (5) or a salt thereof, the transmittance of the polarizing element can be further improved in the range of 400 to 500 nm, and a high degree of polarization can be obtained, which is preferable.

[0110] Next, the azo compound represented by formula (4) will be described.

[0111] [ka]

[0112] (In the above formula (4), Ay 11are each independently a hydrogen atom, a sulfo group, a carboxy group, a hydroxy group, a lower alkyl group, or a lower alkoxy group, and Ry 11 ~Ry 14 are each independently a hydrogen atom, a sulfo group, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group, and f is an integer of 1 to 3.

[0113] In the above formula (4), Ay11 is preferably a sulfo group or a carboxy group. Ry11 to Ry14 are preferably a hydrogen atom, a sulfo group, a lower alkyl group or a lower alkoxy group, and more preferably a hydrogen atom, a methyl group or a methoxy group.

[0114] Specific examples of the azo compound represented by formula (4) include, but are not limited to, CI Direct Yellow 4, CI Direct Yellow 12, CI Direct Yellow 72, and CI Direct Orange 39, as well as azo compounds having a stilbene structure described in WO 2007 / 138980 and the like.

[0115] The azo compound represented by formula (4) or a salt thereof can be synthesized by the method described in, for example, WO 2007 / 138980.

[0116] Further specific examples of the azo compound represented by formula (4) are listed below. The compound examples are shown in the form of free acid.

[0117] [ka]

[0118] Next, the azo compound represented by formula (5) will be described.

[0119] [ka]

[0120] (In equation (5), Ay 21 and Ay 22 each independently represents a naphthyl group which may have a substituent, or a phenyl group which may have a substituent; Ry 21 , Ry 22 , Ry 27 , Ry 28 are each independently a hydrogen atom, a C1-4 alkyl group, or a C1-4 alkoxy group, and Ry 23 ~Ry 26 are each independently a hydrogen atom, a C1-4 alkyl group, a C1-4 alkoxy group, or a C1-4 alkoxy group having a sulfo group, and s and t are each independently 0 or 1.

[0121] The substituted phenyl group is preferably a phenyl group having one or more substituents selected from a sulfo group, a carboxy group, a lower alkoxy group having a sulfo group, a lower alkyl group, a lower alkoxy group, a halogen group, a nitro group, an amino group, a lower alkyl-substituted amino group, and a lower alkyl-substituted acylamino phenyl group. When the phenyl group has two or more substituents, it is preferable that at least one of the substituents is a sulfo group, a carboxy group, or a lower alkoxy group having a sulfo group, and the other substituents are a sulfo group, a hydrogen atom, a lower alkyl group, a lower alkoxy group, a lower alkoxy group having a sulfo group, a carboxy group, a chloro group, a bromo group, a nitro group, an amino group, a lower alkyl-substituted amino group, or a lower alkyl-substituted acylamino group, more preferably a sulfo group, a hydrogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, a carboxy group, a sulfoethoxy group, a sulfopropoxy group, a sulfobutoxy group, a chloro group, a nitro group, or an amino group, and particularly preferably a sulfo group, a carboxy group, a hydrogen atom, a methyl group, a methoxy group, a sulfoethoxy group, a sulfopropoxy group, or a sulfobutoxy group. The substitution position is not particularly limited, but is preferably only the 2-position, only the 4-position, a combination of the 2- and 6-positions, a combination of the 2- and 4-positions, or a combination of the 3- and 5-positions, and particularly preferably only the 2-position, only the 4-position, a combination of the 2- and 4-positions, or a combination of the 3- and 5-positions. Note that only the 2-position and only the 4-position indicate that only the 2- or 4-position has one substituent other than a hydrogen atom.

[0122] The substituted phenyl group is preferably represented by the following formula (11).

[0123] [ka]

[0124] In formula (11), Ry 2a and Ry 2b At least one of Ry is a sulfo group, a carboxyl group, or a lower alkoxy group having a sulfo group, and the other is a hydrogen atom, a sulfo group, a carboxy group, a lower alkoxy group having a sulfo group, a lower alkyl group, a lower alkoxy group, a halogen group, a nitro group, an amino group, a lower alkyl-substituted amino group, or a lower alkyl-substituted acylamino group. 2a and Ry 2b One of the groups is a sulfo group or a carboxy group, and the other is a hydrogen atom, a sulfo group, a carboxy group, a methyl group, or a methoxy group.

[0125] The naphthyl group which may have a substituent is preferably a naphthyl group which may have one or more substituents selected from a hydroxy group, a lower alkoxy group having a sulfo group, and a sulfo group.

[0126] The naphthyl group which may have a substituent is preferably a naphthyl group represented by the following formula (12).

[0127] [ka]

[0128] In formula (12), Ry 2c is a hydrogen atom, a hydroxy group, a lower alkoxy group having a sulfo group, or a sulfo group. u is an integer of 1 to 3. The sulfo group may be located on any benzene nucleus of the naphthalene ring. Preferably, Ry 2cis a hydrogen atom, and u is 2. The lower alkoxy group having a sulfo group is preferably a linear alkoxy group, and the substitution position of the sulfo group is preferably the terminal of the alkoxy group. The lower alkoxy group having a sulfo group is more preferably a 3-sulfopropoxy group or a 4-sulfobutoxy group. The positions of the substituents on the naphthyl group are not particularly limited, but in terms of the numbers shown in formula (12), assuming that the substitution position of the azo group in formula (5) is position 2, when there are two substituents, combinations of positions 5 and 7, positions 4 and 8, or positions 6 and 8 are preferred, and when there are three substituents, positions 3, 5 and 7, or positions 3, 6 and 8 are preferred.

[0129] Ry 21 , Ry 22 , Ry 27 , Ry 28 are each independently a hydrogen atom, a lower alkoxy group, or a lower alkyl group, and are preferably a hydrogen atom, a methyl group, an ethyl group, a methoxy group, or an ethoxy group.

[0130] Ry 23 ~Ry 26 are each independently a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfo group, 23 ~Ry 26 are each independently preferably a hydrogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, a 3-sulfopropoxy group, or a 4-sulfobutoxy group, more preferably a hydrogen atom, a methyl group, an ethyl group, a methoxy group, or a 3-sulfopropoxy group. The positions of Ry3 to Ry6 are preferably the 2-position only, the 5-position only, a combination of the 2- and 6-positions, a combination of the 2- and 5-positions, or a combination of the 3- and 5-positions, more preferably the 2-position only, the 5-position only, or a combination of the 2- and 5-positions. Note that the 2-position only and the 5-position only indicate that only the 2- or 5-position has one substituent other than a hydrogen atom.

[0131] The azo compound represented by formula (5) is preferably represented by the following formula (5b).

[0132] [ka] (In formula (5b), Ay 21 , Ay 22 , Ry 21 ~Ry 28 , s, and t each have the same meaning as in formula (5).

[0133] The azo compound represented by the above formula (5) or the azo compound represented by the formula (5b) or a salt thereof can be produced by carrying out diazotization and coupling in accordance with a normal azo dye production method as described in Non-Patent Document 1, and then reacting with a ureidating agent as described in Patent Documents 4 to 7.

[0134] Next, specific examples of the azo compound represented by formula (5) or the azo compound represented by formula (5b) are listed below. Note that the sulfo group, carboxy group and hydroxy group in the formula are represented in the form of free acid.

[0135] [ka]

[0136] [ka]

[0137] [ka]

[0138] [ka]

[0139] [ka]

[0140] [ka]

[0141]

change

[0142]

change

[0143]

change

[0144]

change

[0145]

change

[0146]

change

[0147]

change

[0148]

change

[0149]

change

[0150]

change

[0151] The azo compounds represented by the above formulas (1) to (5) may be in the form of free acids or salts, or may be salts of metal ions or ammonium ions. Examples of metal ions include alkali metal ions such as lithium ion, sodium ion, and potassium ion, and alkaline earth metal ions such as calcium ion and magnesium ion. Examples of ammonium ions include ammonium ion, methylammonium ion, dimethylammonium ion, triethylammonium ion, tetraethylammonium ion, tetra-n-propylammonium ion, tetra-n-butylammonium ion, and triethanolammonium ion. More specifically, for example, in the case of free acids, they represent sulfonic acid (-SO3H), in the case of sodium ions, they represent sodium sulfonate (-SO3Na), and in the case of ammonium ions, they represent ammonium sulfonate (-SO3NH4).

[0152] The polarizing element of the present invention contains an azo compound represented by formula (1) or an azo compound represented by formula (2) and an azo compound represented by formula (3). A polarizing element with high transmittance and high contrast, i.e., a high degree of polarization, can be provided. Optionally, by further containing an azo compound represented by formula (4) or an azo compound represented by formula (5), a polarizing element with even higher transmittance and high contrast, i.e., a high degree of polarization, can be provided.

[0153] The polarizing element of the present invention has excellent polarization performance, such as chromaticity a* and b* values ​​within the preferred ranges described below, single-piece transmittance after luminosity correction, and average transmittance in a specific wavelength band. For example, the polarizing element alone can maintain a constant transmittance at each wavelength. Furthermore, when the absorption axes of two polarizing elements are parallel, the transmittance can be maintained at each wavelength in the parallel position, i.e., an achromatic hue can be obtained. Furthermore, when the absorption axes of two polarizing elements are perpendicular, the transmittance can be maintained at each wavelength in the orthogonal position, i.e., an achromatic hue can be obtained. Therefore, the polarizing element of the present invention not only has high transmittance and high contrast, i.e., a high degree of polarization, but also has an achromatic hue.

[0154] By varying the amount of each azo compound contained in the substrate in the polarizing element of the present invention, the transmittance and chromaticity can be adjusted to fall within the preferred ranges described below. The performance of the polarizing element varies depending not only on the blending ratio of each azo compound in the polarizing element but also on various factors such as the swelling degree of the substrate to which the azo compound is adsorbed, the stretching ratio, the dyeing time, the dyeing temperature, the pH during dyeing, and the influence of salt. Therefore, the blending ratio of each azo compound can be determined depending on the swelling degree of the substrate, the dyeing temperature, the dyeing time, the pH, the type and concentration of salt, and even the stretching ratio.

[0155] (Transmittance after luminosity correction) The luminosity-corrected transmittance refers to the transmittance corrected to the luminosity of the human eye and can be determined in accordance with JIS Z 8722:2009. For a measurement sample (e.g., a polarizing element or polarizing plate), the spectral transmittance of each wavelength is measured in 5-nm or 10-nm increments over a wavelength range of 380 to 780 nm using a C-type light source (2-degree field of view), and the transmittance is corrected to the luminosity in accordance with JIS Z 8722:2009. The luminosity-corrected transmittance includes the luminosity-corrected single transmittance (Ys) when a single measurement sample is used; the luminosity-corrected parallel transmittance (Yp) when two measurement samples are used with their absorption axes parallel; and the luminosity-corrected crossed transmittance (Yc) when two measurement samples are used with their absorption axes perpendicular to each other.

[0156] (difference in average transmittance between two wavelength bands) In the polarizing element of the present invention, the difference in average transmittance between specific wavelength bands is preferably a predetermined value or less, where the average transmittance refers to the average value of the transmittance for each wavelength in the specific wavelength band.

[0157] The wavelength bands of 420nm to 480nm, 520nm to 590nm, and 600nm to 640nm are the main wavelength bands based on the color matching functions used in calculations to indicate colors in JIS Z 8781-4:2013. Specifically, in the XYZ color matching functions of JIS Z 8701, which is the basis of JIS Z 8781-4:2013, when the maximum values ​​of x(λ) with a maximum value at 600nm, y(λ) with a maximum value at 550nm, and z(λ) with a maximum value at 455nm are taken as 100, the wavelength bands of 420nm to 480nm, 520nm to 590nm, and 600nm to 640nm respectively show values ​​of 20 or more. Hereinafter, the average transmittance of each wavelength from ○nm to △nm is referred to as "AT ○-△ " is also called.

[0158] (parallel transmittance) The transmittance measured at each wavelength when two polarizing elements are stacked so that the absorption axis directions are parallel (in bright display or white display) is also referred to as the "parallel transmittance (Tp)" of each wavelength. Regarding the parallel transmittance of each wavelength of the polarizing element of the present invention, the difference in average transmittance between two wavelength bands is AT 420-480 and AT 520-590 The absolute value of the difference between AT and AT is preferably 2.5% or less, more preferably 1.8% or less, even more preferably 1.5% or less, and particularly preferably 1.0% or less. 520-590 and AT 600-640 The absolute value of the difference between the polarizing elements is preferably 3.0% or less, more preferably 2.0% or less, even more preferably 1.5% or less, and particularly preferably 1.0% or less. Such a polarizing element can display high-quality paper-like white in the parallel position.

[0159] (orthogonal transmittance) The transmittance measured at each wavelength when two polarizing elements are stacked so that the absorption axis directions are perpendicular (during black display or dark display) is referred to as the "orthogonal transmittance (Tc)" of each wavelength. Regarding the orthogonal transmittance of each wavelength of the polarizing element of the present invention, the difference in average transmittance between two wavelength bands is AT 420-480 and AT 520-590The absolute difference between the 520-590 and AT 600-640 It is preferable that the difference between the polarizing elements is 1.0% or less in absolute value. Such a polarizing element can display achromatic black in the orthogonal direction. 420-480 and AT 520-590 The absolute value of the difference between AT and AT is preferably 0.6% or less, more preferably 0.3% or less, and even more preferably 0.1% or less. 520-590 and AT 600-640 The absolute value of the difference between is preferably 1.0% or less, more preferably 0.6% or less, even more preferably 0.3% or less, and particularly preferably 0.1%.

[0160] Furthermore, it is preferable that the average transmittances of the single transmittance, parallel transmittance, and crossed transmittance at each wavelength in the wavelength bands 380 nm to 420 nm, 480 nm to 520 nm, and 640 nm to 780 nm, which are different from the above wavelength bands, are also adjusted to some extent. Regarding the single transmittance at each wavelength of the polarizing element of the present invention, the difference in average transmittance between two wavelength bands is AT 380-420 and AT 420-480 It is preferable that the difference between 480-520 and AT 420-480 It is more preferable that the difference between 480-520 and AT 520-590 It is preferable that the difference between 640-780 and AT 600-640 It is more preferable that the difference between them is 20% or less.

[0161] (Single transmittance value after luminosity correction) The polarizing element of the present invention preferably has a single transmittance (Ys) after luminosity correction of 35% to 65%. The single transmittance after luminosity correction is the transmittance of a single measurement sample (e.g., a polarizing element or polarizing plate) corrected for luminosity according to JIS Z 8722:2009. In terms of polarizing plate performance, a single transmittance after luminosity correction of 35% to 65% allows for a natural brightness to be displayed when used in a display device. Since the degree of polarization tends to decrease as the transmittance increases, from the viewpoint of the balance with the degree of polarization, the single transmittance after luminosity correction is preferably 36% to 55%, more preferably 37% to 50%, even more preferably 38% to 48%, and particularly preferably 39% to 45%. If the single transmittance after luminosity correction exceeds 65%, the degree of polarization may decrease. However, if a bright transmittance or specific polarization performance or contrast is desired for the polarizing element, the single transmittance after luminosity correction may exceed 65%.

[0162] (Average transmittance in a specific wavelength band) The polarizing element of the present invention has an average parallel transmittance (Tp) of each wavelength of AT 520-590 is preferably 25% to 50%. When such a polarizing element is installed in a display device, it can produce a bright, clear display device with high luminance. The transmittance in the wavelength band of 520 nm to 590 nm is one of the main wavelength bands based on the color-matching function used in calculations to indicate color in JIS Z 8781-4:2013. In particular, each wavelength band of 520 nm to 590 nm is the wavelength band with the highest luminosity based on the color-matching function, and it is said that the transmittance in this range is close to the transmittance that can be confirmed visually. For this reason, it is very important to adjust the transmittance in the wavelength band of 520 nm to 590 nm. The average transmittance AT of the parallel-angle transmittance of each wavelength is 520-590is more preferably 28% to 45%, and even more preferably 30% to 40%. Furthermore, the degree of polarization of the polarizing element in this case is preferably 80% to 100%, more preferably 90% to 100%, even more preferably 97% to 100%, still more preferably 99% or more, and particularly preferably 99.5% or more. A higher degree of polarization is preferable, but in the relationship between the degree of polarization and transmittance, the transmittance and degree of polarization can be adjusted to an appropriate level depending on whether brightness or the degree of polarization (or contrast) is given priority.

[0163] (chromaticity a* and b* values) The chromaticity a* and b* values ​​are determined by measuring the transmittance of natural light according to JIS Z 8781-4:2013. The object color representation method defined in JIS Z 8781-4:2013 corresponds to that defined by the International Commission on Illumination (CIE). The chromaticity a* and b* values ​​are measured by irradiating a measurement sample (e.g., a polarizing element or polarizing plate) with natural light. In the following, the chromaticity a* and b* values ​​determined for one measurement sample are referred to as a*-s and b*-s, the chromaticity a* and b* values ​​determined for two measurement samples arranged so that their absorption axes are parallel to each other (white display) are referred to as a*-p and b*-p, and the chromaticity a* and b* values ​​determined for two measurement samples arranged so that their absorption axes are perpendicular to each other (black display) are referred to as a*-c and b*-c.

[0164] In the polarizing element of the present invention, the absolute values ​​of chromaticity a*-s and b*-s determined for one measurement sample are preferably 1.0 or less (-1.0≦a*-s≦1.0, -1.0≦b*-s≦1.0). Furthermore, a*-p is preferably -2.0 to 2.0 (-2.0≦a*-p≦2.0), and b*-p is preferably -2.0 to 3.0 (-2.0≦b*-p≦3.0). Such a polarizing element is color-neutral by itself and can display high-quality white when displaying white. More preferably, the absolute values ​​of a*-p and b*-p when two measurement samples are arranged so that their absorption axes are parallel to each other (when displaying white) are each independently 2.0 or less, even more preferably 1.5 or less, and particularly preferably 1.0 or less. Furthermore, when two measurement samples are arranged so that their absorption axes are perpendicular to each other (during black display), the absolute values ​​of chromaticity a*-c and b*-c are preferably 2.0 or less (-2.0≦a*-c≦2.0, -2.0≦b*-c≦2.0), and more preferably 1.0 or less (-1.0≦a*-c≦1.0, -1.0≦b*-c≦1.0). Such a polarizing element can display achromatic black during black display. Even a difference of 0.5 in the absolute values ​​of chromaticity a* and b* values ​​can be perceived by humans as a color difference, and some people may perceive the color difference as significant. For this reason, controlling these values ​​in a polarizing element is extremely important. In particular, when the absolute values ​​of a*-p, b*-p, a*-c, and b*-c are each 1.0 or less, a good polarizing plate can be obtained in which other colors are almost indistinguishable between the white and black colors during white and black display. In the parallel position, it is possible to achieve achromatic white, i.e., a high-quality paper-like white, and in the perpendicular position, it is possible to achieve achromatic, clear, and luxurious black. However, this does not necessarily apply to the hue that gives the black color to the display device; in the absence of light (darkness), the light will appear black even if it has a hue. Therefore, when the degree of polarization is high, i.e., when the perpendicular transmittance is low, the polarizing element can achieve black even if the absolute values ​​of a*-c and b*-c are not each 2.0 or less.As a result of our investigations, we found that when the cross-phase transmittance at each wavelength in the wavelength bands of 420 nm to 480 nm, 520 nm to 590 nm, and 600 nm to 640 nm is 1% or less or the degree of polarization is approximately 97% or more, visually black can be achieved regardless of the absolute values ​​of a*-c and b*-c. A cross-phase transmittance at each wavelength in the wavelength bands of 420 nm to 480 nm, 520 nm to 590 nm, and 600 nm to 640 nm of 0.6% or less or a polarization degree of 98% or more is more preferable because it can achieve a more visually black color. A cross-phase transmittance at each wavelength of 0.3% or less or a polarization degree of 99% or more is particularly preferable.

[0165] From the above, in order to provide an achromatic black hue when two polarizing elements are stacked and arranged so that their absorption axis directions are perpendicular to each other (during black display or dark display), it is preferable to satisfy any one of the following conditions 1) to 3). 1) For the cross-phase transmittance (Tc) of each wavelength, AT 420-480 and AT 520-590 The absolute difference between the 520-590 and AT 600-640 The absolute difference between 2) When the absolute values ​​of chromaticity a*-c and b*-c are 2.0 or less 3) When the cross-phase transmittance (Tc) of each wavelength in the wavelength bands 420nm to 480nm, 520nm to 590nm, and 600nm to 640nm is 1% or less, or the degree of polarization is approximately 97% or more.

[0166] The polarizing element of the present invention has high contrast and high transmittance, while also exhibiting achromaticity and a high degree of polarization by itself. Furthermore, the polarizing element of the present invention can express a high-quality paper-like white color (paper white) when displaying white, and can express an achromatic black color, particularly a clear black color with a luxurious feel, when displaying black. The polarizing element of the present invention also has high durability, particularly durability against high temperatures and high humidity.

[0167] The polarizing element of the present invention has the advantage of having low absorption of light with wavelengths of 700 nm or more compared to iodine-based polarizing plates and the polarizing element described in Patent Document 3, and therefore generates little heat even when exposed to light such as sunlight. For example, when a liquid crystal display is used outdoors, sunlight is irradiated onto the liquid crystal display, and as a result, the polarizing element is also irradiated. Sunlight also contains light with wavelengths of 700 nm or more, and light in the near-infrared region has a heat-generating effect. The polarizing element of the present invention has extremely low absorption of near-infrared light, and therefore generates little heat even when exposed to sunlight outdoors, and therefore is excellent in that it also generates little deterioration.

[0168] <Method for manufacturing polarizing elements> A specific method for producing a polarizing element will be described below, taking as an example a case where an azo compound is adsorbed onto a substrate made of a polyvinyl alcohol resin. However, the method for producing a polarizing element of the present invention is not limited to the following method.

[0169] (Preparing the original film) The raw film can be produced by forming a polyvinyl alcohol resin. The polyvinyl alcohol resin is not particularly limited, and commercially available products or those synthesized by known methods may be used. The polyvinyl alcohol resin can be obtained, for example, by saponifying a polyvinyl acetate resin. Examples of polyvinyl acetate resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. The saponification degree of the polyvinyl alcohol resin is preferably about 85 to 100 mol%, and more preferably 95 mol% or higher. The polyvinyl alcohol resin may be further modified; for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may also be used. The degree of polymerization of the polyvinyl alcohol resin means the viscosity-average degree of polymerization, which can be determined by a method well known in the art, and is usually preferably about 1,000 to 10,000, more preferably about 1,500 to 6,000.

[0170] The method for forming the polyvinyl alcohol resin into a film is not particularly limited, and a known method can be used. In this case, the polyvinyl alcohol resin film may contain a plasticizer such as glycerin, ethylene glycol, propylene glycol, or low-molecular-weight polyethylene glycol. The amount of the plasticizer is preferably 5 to 20 mass % of the total amount of the film, more preferably 8 to 15 mass %. The thickness of the raw film is not particularly limited, but is preferably about 5 μm to 150 μm, and more preferably about 10 μm to 100 μm.

[0171] (Swelling process) The raw film obtained as described above is subjected to a swelling treatment. The swelling treatment is preferably carried out by immersing the raw film in a solution at 20 to 50°C for 30 seconds to 10 minutes. The solution is preferably water. The stretching ratio is preferably adjusted to 1.00 to 1.50 times, more preferably 1.10 to 1.35 times. When shortening the time required to manufacture a polarizing element, the raw film also swells during the dyeing treatment described below, so the swelling treatment can be omitted.

[0172] (dying process) In the dyeing process, an azo compound is adsorbed and impregnated into the resin film obtained by swelling the raw film. If the swelling process is omitted, the swelling process of the raw film can be carried out simultaneously with the dyeing process. The process of adsorbing and impregnating the azo compound is a process of coloring the resin film, so it is called the dyeing process.

[0173] The azo compound used in the dyeing process is a mixture of an azo compound represented by formula (1) or (2) and an azo compound represented by formula (3). Optionally, an azo compound represented by formula (4) or (5) can also be used. Furthermore, azo compounds that are dichroic dyes, such as those exemplified in Non-Patent Document 2, can be used to the extent that the performance of the polarizing element of the present invention is not impaired. These azo compounds can be used in the form of free acid, or salts of the compounds can be used. Examples of such salts include alkali metal salts such as lithium salts, sodium salts, and potassium salts, or organic salts such as ammonium salts and alkylamine salts, with sodium salts being preferred.

[0174] The dyeing step is not particularly limited as long as it is a method for adsorbing and impregnating a dye into a resin film, but for example, it is preferably performed by immersing the resin film in a dyeing solution, or it can also be performed by applying the dyeing solution to the resin film. The concentration of each azo compound in the dyeing solution can be adjusted, for example, within the range of 0.001 to 10 mass %.

[0175] 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 for immersion in the solution can be adjusted appropriately, but is preferably adjusted to 30 seconds to 20 minutes, and more preferably 1 to 10 minutes.

[0176] In addition to the azo compound, the dyeing solution may further contain a dyeing assistant as needed. Examples of dyeing assistants include sodium carbonate, sodium bicarbonate, sodium chloride, sodium sulfate, anhydrous sodium sulfate, and sodium tripolyphosphate. The content of the dyeing assistant can be adjusted to any concentration by adjusting the time and temperature depending on the dyeing properties of the dye, but the content of each assistant in the dyeing solution is preferably 0.001 to 5% by mass, and more preferably 0.01 to 2% by mass.

[0177] (Cleaning process 1) After the dyeing step, a washing step (hereinafter also referred to as "washing step 1") can be performed before the next step. Washing step 1 is a step of washing away the dye solution that has adhered to the surface of the resin film during the dyeing step. By performing washing step 1, it is possible to prevent the dye from migrating into the subsequent treatment liquid. In washing step 1, water is generally used as the washing liquid. The washing method is preferably immersion in the washing liquid, but washing can also be performed by applying the washing liquid to the resin film. The washing time is not particularly limited, but is preferably 1 to 300 seconds, more preferably 1 to 60 seconds. The temperature of the washing liquid in washing step 1 must be a temperature at which the material constituting the resin film (e.g., hydrophilic polymer, in this case, polyvinyl alcohol-based resin) does not dissolve. Washing is generally performed at 5 to 40°C. However, since there is no problem with performance even if washing step 1 is not performed, the washing step can be omitted.

[0178] (Step of adding a crosslinking agent and / or a water-resistant agent) After the dyeing step or washing step 1, a step of incorporating a crosslinking agent and / or a water-resistant agent can be carried out. The method of incorporating a crosslinking agent and / or a water-resistant agent into the resin film is preferably immersion in a treatment solution, but the treatment solution may also be applied or coated onto the resin film. The treatment solution contains at least one crosslinking agent and / or water-resistant agent and a solvent. The temperature of the treatment solution in this step is preferably 5 to 70°C, more preferably 5 to 50°C. The treatment time in this step is preferably 30 seconds to 6 minutes, more preferably 1 to 5 minutes.

[0179] Examples of crosslinking agents that can be used include boron compounds such as boric acid, borax, and ammonium borate; polyaldehydes such as glyoxal and glutaraldehyde; polyisocyanate compounds such as biuret, isocyanurate, and block types; and titanium compounds such as titanium oxysulfate. Other examples include ethylene glycol glycidyl ether and polyamide epichlorohydrin. Examples of water-resistant agents include succinic peroxide, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerin diglycidyl ether, ammonium chloride, and magnesium chloride, with boric acid being preferred. The solvent for the crosslinking agent and / or water-resistant agent is preferably water, but is not limited thereto. The concentration of the crosslinking agent and / or water-resistant agent can be appropriately determined by a person skilled in the art depending on the type, but taking boric acid as an example, the concentration in the treatment solution is preferably 0.1 to 6.0 mass %, more preferably 1.0 to 4.0 mass %. However, if it is not essential to add a crosslinking agent and / or water-resistant agent and it is desired to shorten the treatment time, or if crosslinking treatment or water-resistant treatment is not necessary, this treatment step may be omitted.

[0180] (Stretching process) The stretching step is carried out after the dyeing step, washing step 1, or the step of incorporating a crosslinking agent and / or a water-resistant agent. The stretching step is carried out by uniaxially stretching the resin film. The stretching method may be either a wet stretching method or a dry stretching method. The stretching ratio is preferably 3 times or more, more preferably 4 to 8 times, and particularly preferably 5 to 7 times.

[0181] In the case of wet stretching, 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 immersing the film in a solution containing at least one crosslinking agent and / or water-resistant agent. The crosslinking agent and water-resistant agent can be the same as those described above for the step of incorporating the crosslinking agent and / or water-resistant agent. The concentration of the crosslinking agent and / or water-resistant agent in the solution in the stretching step is, for example, preferably 0.5 to 15% by mass, more preferably 2.0 to 8.0% by mass. The stretching temperature is preferably 40 to 60°C, more preferably 45 to 58°C. The stretching time is usually 30 seconds to 20 minutes, more preferably 2 to 5 minutes. The wet stretching step can be performed in one stage, but can also be performed in two or more stages.

[0182] In the case of dry stretching, when the stretching heating medium is air, the resin film is preferably stretched at a temperature of the air medium ranging from room temperature to 180°C. The humidity in the atmosphere is preferably 20 to 95% RH. Examples of heating methods include inter-roll zone stretching, roll heating stretching, rolling stretching, and infrared heating stretching, but the stretching method is not limited thereto. The stretching process can be performed in one stage, or in two or more stages.

[0183] (Cleaning process 2) After the stretching step, a washing step (hereinafter also referred to as "washing step 2") can be carried out to wash the surface of the resin film, since precipitation of the crosslinking agent and / or water-resistant agent or adhesion of foreign matter may occur on the surface of the resin film. The washing time is preferably 1 second to 5 minutes. The washing method is preferably to immerse the resin film in a washing solution, but washing can also be carried out by applying or coating the solution onto the resin film. Water is preferred as the washing solution. The washing treatment can be carried out in one stage, or in multiple stages of two or more stages. The solution temperature in the washing step is not particularly limited, but is usually 5 to 50°C, preferably 10 to 40°C.

[0184] Examples of the treatment liquid or its solvent used in the treatment steps up to this point include, but are not limited to, water, as well as alcohols such as dimethyl sulfoxide, N-methylpyrrolidone, methanol, ethanol, propanol, isopropyl alcohol, glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. The treatment liquid or its solvent is most preferably water. These treatment liquids or their solvents can be used alone or in combination of two or more.

[0185] (drying process) After the stretching step or washing step 2, the resin film is dried. The drying process can be carried out by natural drying, but to improve drying efficiency, it can be carried out by compressing with a roll, removing surface moisture with an air knife or a water-absorbing roll, and / or by air drying. The drying temperature is preferably 20 to 100°C, more preferably 60 to 100°C. The drying time is usually 30 seconds to 20 minutes, but preferably 5 to 10 minutes.

[0186] In the method for producing a polarizing element, the swelling degree of the substrate in the swelling step, the compounding ratio of each azo compound in the dyeing step, the temperature and pH of the dyeing solution, the type and concentration of salts such as sodium chloride, sodium sulfate, and sodium tripolyphosphate, and the dyeing time, as well as the stretching ratio in the stretching step are preferably adjusted so that the polarizing element of the present invention satisfies at least one of the following conditions (i) to (vi), and more preferably so that conditions (vii) and (viii) are also satisfied. (i) For parallel transmission (Tp), AT 420-480 and AT 520-590 The absolute difference between 520-590 and AT 600-640 The absolute value of the difference is 3.0. (ii) Regarding the cross-phase transmittance (Tc), AT 420-480 and AT 520-590 The absolute value of the difference between 520-590 and AT 600-640 The absolute value of the difference between these is 1.0 or less. (iii) The single transmittance (Ys) after luminosity correction is 35 to 65%. (iv) The absolute values ​​of the chromaticity a* and b* values ​​of the polarizing element alone are both 1.0 or less. (v) In the chromaticity a* and b* values ​​at the parallel position, the a* value is −2.0 to 2.0, and the b* value is −2.0 to 3.0. (vi) The absolute values ​​of the chromaticity a* and b* values ​​in the orthogonal plane are both 2.0 or less. (vii) Regarding parallel transmission (Tp), AT 520-590 is 25-35%. (viii) In the single transmittance (Ts) or cross-phase transmittance (Tc), AT 380-420 and AT 420-480 The difference between 480-520 and AT 420-480 The difference between 480-520 and AT 520-590 and / or AT 640-780 and AT 600-640 The difference is less than 20%.

[0187] By the above method, a polarizing element containing a combination of an azo compound represented by formula (1) or an azo compound represented by formula (2) and an azo compound represented by formula (3), or optionally a combination of an azo compound represented by formula (4) or an azo compound represented by formula (5) can be produced.

[0188] <Polarizing plate> The polarizing plate of the present invention comprises a polarizing element and a transparent protective layer provided on one or both sides of the polarizing element for the purposes of improving the water resistance and handling properties of the polarizing element.

[0189] The transparent protective layer is a protective film formed using a transparent material. The protective film is a film having a layer shape that can maintain the shape of the polarizing element, and is preferably made of a plastic or the like that has excellent transparency, mechanical strength, thermal stability, moisture-blocking properties, etc. Equivalent functions may also be achieved by forming an equivalent layer. Examples of plastics that constitute the protective film include films obtained from thermoplastic resins such as polyester-based resins, acetate-based resins, polyethersulfone-based resins, polycarbonate-based resins, polyamide-based resins, polyimide-based resins, polyolefin-based resins, and acrylic-based resins, as well as thermosetting or UV-curable resins such as acrylic, urethane, acrylic urethane, epoxy, and silicone-based resins. Among these, polyolefin-based resins include amorphous polyolefin-based resins that contain polymerization units of cyclic polyolefins such as norbornene-based monomers or polycyclic norbornene-based monomers. In general, it is preferable to select a protective film that does not impair the performance of the polarizing element after lamination. As such protective films, triacetyl cellulose (TAC) and norbornene, which are made of cellulose acetate-based resins, are particularly preferred. Furthermore, the protective film may be subjected to hard coating treatment, anti-reflection treatment, treatment for preventing sticking, diffusion, anti-glare, etc., as long as the effects of the present invention are not impaired. The thickness of the transparent protective layer is preferably 10 to 200 μm.

[0190] The polarizing plate of the present invention preferably further includes an adhesive layer between the transparent protective layer and the polarizing element for bonding the transparent protective layer to the polarizing element. The adhesive constituting the adhesive layer is not particularly limited. Examples include polyvinyl alcohol-based adhesives, urethane emulsion-based adhesives, acrylic adhesives, and polyester-isocyanate-based adhesives, with polyvinyl alcohol-based adhesives being preferred. Examples of polyvinyl alcohol-based adhesives include, but are not limited to, Gohsenol NH-26 (manufactured by Nippon Synthetic Co., Ltd.) and Exeval RS-2117 (manufactured by Kuraray Co., Ltd.). A crosslinking agent and / or a water-resistant agent may be added to the adhesive. A maleic anhydride-isobutylene copolymer is preferably used as the polyvinyl alcohol-based adhesive, and an adhesive containing a crosslinking agent may be used as needed. Examples of maleic anhydride-isobutylene copolymers include ISOBAM #18 (manufactured by Kuraray Co., Ltd.), ISOBAM #04 (manufactured by Kuraray Co., Ltd.), ammonia-modified ISOBAM #104 (manufactured by Kuraray Co., Ltd.), ammonia-modified ISOBAM #110 (manufactured by Kuraray Co., Ltd.), imidized ISOBAM #304 (manufactured by Kuraray Co., Ltd.), and imidized ISOBAM #310 (manufactured by Kuraray Co., Ltd.). A water-soluble polyfunctional epoxy compound can be used as the crosslinking agent. Examples of water-soluble polyfunctional epoxy compounds include Denacol EX-521 (manufactured by Nagase Chemtec Corporation) and Tetrat-C (manufactured by Mitsui Gas Chemical Co., Ltd.). In addition to polyvinyl alcohol-based resins, known adhesives such as urethane-based, acrylic-based, and epoxy-based adhesives can also be used. It is particularly preferable to use acetoacetyl-modified polyvinyl alcohol, and it is further preferable to use a polyhydric aldehyde as the crosslinking agent. Furthermore, in order to improve the adhesive strength or water resistance of the adhesive, additives such as zinc compounds, chlorides, and iodides may be added singly or together at a concentration of about 0.1 to 10% by mass. The additives to the adhesive are not particularly limited and can be selected appropriately by those skilled in the art. After bonding the transparent protective layer and the polarizing element with the adhesive, a polarizing plate can be obtained by drying or heat treatment at an appropriate temperature.

[0191] When the polarizing element or polarizing plate of the present invention is attached to a display device such as a liquid crystal display or an organic electroluminescence display (commonly known as an OLED or OEL), various functional layers for improving the viewing angle and / or contrast, or layers or films having brightness-enhancing properties may be provided on the surface of the protective layer or film that will later become the unexposed surface. The various functional layers are, for example, layers or films that control retardation. The polarizing plate is preferably attached to these films or display devices with an adhesive. By attaching a retardation plate, the polarizing plate of the present invention can also be used as an elliptical polarizing plate. The polarizing plate is preferably attached to these films or display devices with an adhesive.

[0192] The polarizing element or polarizing plate of the present invention may have various known functional layers on the exposed surface of its transparent protective layer or film, such as an AR layer (antireflection layer), an antiglare layer, a hard coat layer, etc. A coating method is preferred for producing these layers having various functions, but films having these functions can also be attached via an adhesive or pressure-sensitive adhesive.

[0193] Examples of the hard coat layer include protective layers such as acrylic, polysiloxane, and urethane hard coat layers. The anti-reflection layer is expected to further improve the light transmittance of the single panel. The anti-reflection layer can be formed by coating, vapor deposition, or sputtering a material such as silicon dioxide or titanium oxide, or by thinly applying a fluorine-based material.

[0194] The polarizing plate of the present invention has high transmittance and a high degree of polarization, and can further achieve achromaticity while maintaining high transmittance and a high degree of polarization. In particular, it is a highly durable polarizing plate that can express a high-quality paper-like white color when displaying white and a neutral black color when displaying black.

[0195] <Display device> The polarizing element or polarizing plate of the present invention may be provided with a protective layer or functional layer and a transparent support such as glass, quartz, or sapphire, as necessary, and may be used in liquid crystal projectors, calculators, clocks, notebook computers, word processors, liquid crystal televisions, polarized lenses, polarized glasses, car navigation systems, and indoor and outdoor measuring instruments and displays, etc.

[0196] In particular, the polarizing element or polarizing plate of the present invention is suitable for use in liquid crystal display devices, such as reflective liquid crystal display devices and semi-transmissive liquid crystal display devices, as well as in organic electroluminescence devices other than liquid crystal display devices. A liquid crystal display device equipped with the polarizing element or polarizing plate of the present invention can display high-quality paper-like white and neutral black. Furthermore, the liquid crystal display device has high durability and reliability, and exhibits high contrast and high color reproducibility over the long term. [Example]

[0197] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. % in the examples is by weight unless otherwise specified.

[0198] [Synthesis Example 1] (Process 1) 15.0 parts of commercially available N-acetyl-1,4-phenylenediamine was added to 200 parts of water and stirred, followed by the addition of 42 parts of 35% hydrochloric acid and 17.3 parts of 40% sodium nitrite. Diazotization was performed by stirring for 1 hour. Next, 32.0 parts of 1,8-dihydroxynaphthalene-3,6-disulfonic acid was added to 200 parts of water and dissolved in a weak alkaline solution of 25% sodium hydroxide. The previously obtained diazotized solution was added dropwise to this solution while maintaining the pH at 6.5-8.0, and the mixture was stirred to complete the coupling reaction. The resulting reaction solution was then stirred at 90-99°C for 5 hours at a pH of 0.0-0.5 to carry out the hydrolysis reaction. The precipitated solid was then filtered off to obtain 150 parts of a wet cake of the monoazo compound represented by formula (13).

[0199] [ka]

[0200] (Process 2) 150 parts of the resulting wet cake of the monoazo compound represented by formula (13) was added to 300 parts of water and stirred to form a suspension. The pH was adjusted to 9.0 using 25% sodium hydroxide, and 17.3 parts of 40% aqueous sodium nitrite solution was added thereto. The resulting aqueous solution was added dropwise to a mixture of 200 parts of water and 42 parts of 35% hydrochloric acid to prepare a diazo solution. 15.3 parts of 2,5-dimethoxyaniline was added to the resulting diazo solution, and the mixture was stirred for 8 hours while maintaining the pH at 1.5 to 4.0 using 15% aqueous sodium carbonate solution to complete the coupling reaction. The mixture was then salted out with sodium chloride and filtered to obtain 200 parts of a wet cake of the disazo compound represented by formula (14).

[0201] [ka]

[0202] (Step 3) 200 parts of the resulting wet cake of the disazo compound represented by formula (14) was added to 500 parts of water and stirred to form a suspension. The pH was adjusted to 9.0 using 25% sodium hydroxide, and 17.3 parts of 40% aqueous sodium nitrite solution was added thereto. The resulting suspension was added dropwise to a mixture of 100 parts of water and 42 parts of 35% hydrochloric acid to prepare a diazo solution. Meanwhile, 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid were added to 300 parts of water and dissolved in a weakly alkaline solution of 25% sodium hydroxide. The previously obtained diazo solution was added dropwise to this solution while maintaining the pH at 6.5 to 8.0, and the mixture was stirred to complete the coupling reaction. The mixture was then salted out with sodium chloride, filtered, and dried to obtain 8.0 parts of the azo compound represented by Compound Example 3-8.

[0203] [Example 1] A polyvinyl alcohol film (VF-PS#7500 manufactured by Kuraray Co., Ltd.) with a saponification degree of 99% or higher and an average polymerization degree of 2400 was immersed in warm water at 40°C for 3 minutes, subjected to a swelling treatment, and stretched at a stretch ratio of 1.30. The resulting film was immersed for 8 minutes in a dyeing solution adjusted to 45°C and containing 1500 parts by weight of water, 1.5 parts by weight of sodium tripolyphosphate, 1.5 parts by weight of anhydrous sodium sulfate, 0.36 parts by weight of the azo compound of formula (2) described in formula (7) of JP 2002-275381 A, and 0.22 parts by weight of Compound Example 3-8, the azo compound of formula (3) obtained in Synthesis Example 1. The azo compound was then incorporated into the film. The resulting film was then immersed for 1 minute in an aqueous solution containing 20 g / L of boric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) at 40°C. The immersed film was stretched 5.0 times while being stretched in a 50°C aqueous solution containing 30.0 g / L of boric acid for 5 minutes. The resulting film was washed by immersing it in 25°C water for 20 seconds while maintaining its tension. The washed film was dried at 70°C for 9 minutes to obtain a polarizing element. An alkali-treated triacetyl cellulose film (Fujifilm ZRD-60) was laminated to this polarizing element using a 4% solution of polyvinyl alcohol (Nippon Vinyl Poval NH-26) in water as an adhesive to obtain a polarizing plate. The resulting polarizing plate maintained the optical performance of the polarizing element, particularly the single transmittance at each wavelength, the parallel transmittance at each wavelength, the crossed transmittance at each wavelength, the hue, and the degree of polarization. This polarizing plate was used as the measurement sample for Example 1.

[0204] [Synthesis Example 2] 8.0 parts of an azo compound represented by Compound Example 3-10 was obtained in the same manner as in Synthesis Example 1, except that 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid in Step 3 of Synthesis Example 1 was changed to 34.5 parts of 1-hydroxy-6-(4-methoxyphenylamino)-3-naphthalenesulfonic acid.

[0205] [Example 2] The film obtained by the swelling treatment was treated for 8 minutes in a dyeing solution at 45°C containing 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, 0.37 parts by mass of Compound Example 2-102, which is an azo compound of formula (2) obtained by a method similar to the method described in Non-Patent Document 1, 0.26 parts by mass of Compound Example 3-10, which is an azo compound of formula (3) obtained in Synthesis Example 2, and 0.27 parts by mass of Compound Example 4-1, which is an azo compound of formula (4) obtained by a method similar to the method described in WO2007 / 138980. A polarizing plate was produced in the same manner as in Example 1, except that the azo compounds were incorporated.

[0206] [Synthesis Example 3] In the same manner as in Synthesis Example 1, except that 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid in Step 3 of Synthesis Example 1 was changed to 35.8 parts of 1-hydroxy-6-(4-aminobenzoylamino)-3-naphthalenesulfonic acid, 11.0 parts of an azo compound represented by Compound Example 3-31 was obtained.

[0207] [Example 3] The film obtained after the swelling treatment was treated for 8 minutes in a dyeing solution at 45°C containing 1,500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, 0.21 parts by mass of Compound Example 1-13 (azo compound of (28) in WO2016 / 186194) which is an azo compound of formula (1), 0.26 parts by mass of Compound Example 3-31 which is an azo compound of formula (3) obtained in Synthesis Example 3, and 0.25 parts by mass of Compound Example 4-1 which is an azo compound of formula (4) obtained by a method similar to the production method in WO2007 / 138980. A polarizing plate was produced in the same manner as in Example 1 except that the azo compounds were contained.

[0208] [Synthesis Example 4] In the same manner as in Synthesis Example 1, except that 32.0 parts of 1,8-dihydroxynaphthalene-3,6-disulfonic acid in Step 1 of Synthesis Example 1 was changed to 33.4 parts of 1-hydroxy-8-methoxynaphthalene-3,6-disulfonic acid, and 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid in Step 3 of Synthesis Example 1 was changed to 37.5 parts of 1-hydroxy-6-(2,4-dimethoxyphenylamino)-3-naphthalenesulfonic acid, 12.0 parts of an azo compound represented by Compound Example 3-15 was obtained.

[0209] [Example 4] The film obtained by the swelling treatment was treated for 8 minutes in a dyeing solution at 45°C containing 1,500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, 0.21 parts by mass of Compound Example 2-29, which is an azo compound represented by formula (2) obtained by a method similar to the method described in Non-Patent Document 1, 0.28 parts by mass of Compound Example 3-15, which is an azo compound represented by formula (3) obtained in Synthesis Example 4, and 0.25 parts by mass of Compound Example 4-1, which is an azo compound represented by formula (4) obtained by a method similar to the method described in WO2007 / 138980. A polarizing plate was produced in the same manner as in Example 1, except that the azo compounds were incorporated.

[0210] [Synthesis Example 5] In the same manner as in Synthesis Example 1, except that 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid in Step 3 of Synthesis Example 1 was changed to 34.4 parts of the compound represented by the following formula (15), 11.3 parts of an azo compound represented by Compound Example 3-32 was obtained.

[0211] [ka]

[0212] [Example 5] The film obtained after the swelling treatment was treated for 8 minutes with a dyeing solution at 45°C containing 1,500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, 0.18 parts by mass of CI Direct Red 117 (Example Compound 2-6), which is an azo compound of formula (2), 0.30 parts by mass of Example Compound 3-32, which is an azo compound of formula (3) obtained in Synthesis Example 5, and 0.25 parts by mass of Example Compound 4-1, which is an azo compound of formula (4) obtained by a method similar to the production method of WO2007 / 138980. A polarizing plate was produced in the same manner as in Example 1, except that the azo compounds were contained.

[0213] [Example 6] The film obtained after the swelling treatment was treated for 8 minutes in a dyeing solution at 45°C containing 1,500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, 0.27 parts by mass of Compound Example 2-77, which is an azo compound of formula (2) obtained by a method similar to the production method described in JP-A-8-291259, 0.28 parts by mass of Compound Example 3-10, which is an azo compound of formula (3) obtained in Synthesis Example 2, and 0.22 parts by mass of Compound Example 4-2, which is an azo compound of formula (4) (the azo compound described in Synthesis Example 1 of WO2007 / 138980). A polarizing plate was produced in the same manner as in Example 1, except that the azo compounds were added.

[0214] [Synthesis Example 6] 13.5 parts of an azo compound represented by Compound Example 3-7 was obtained in the same manner as in Synthesis Example 1, except that 32.0 parts of 1,8-dihydroxynaphthalene-3,6-disulfonic acid in Step 1 of Synthesis Example 1 was changed to 30.4 parts of 1-hydroxynaphthalene-3,6-disulfonic acid.

[0215] [Example 7] The film obtained after the swelling treatment was treated for 8 minutes in a dyeing solution at 45°C containing 1,500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, 0.23 parts by mass of Compound Example 2-70, which is an azo compound of formula (2) obtained by a method similar to the production method described in JP-A-8-291259, 0.29 parts by mass of Compound Example 3-7, which is an azo compound of formula (3) obtained in Synthesis Example 6, and 0.24 parts by mass of Compound Example 4-2, which is an azo compound of formula (4) (the azo compound described in Synthesis Example 1 in WO2007 / 138980). A polarizing plate was produced in the same manner as in Example 1, except that the azo compounds were added.

[0216] [Synthesis Example 7] (Process 1) 150 parts of the wet cake of the monoazo compound represented by formula (13) from step 1 of Synthesis Example 1 was added to 300 parts of water, stirred, and suspended. The pH was adjusted to 9.0 using 25% sodium hydroxide, and 17.3 parts of a 40% aqueous sodium nitrite solution was added thereto. The resulting aqueous solution was added dropwise to a mixture of 200 parts of water and 42 parts of 35% hydrochloric acid to prepare a diazo solution. 12.1 parts of 2,5-dimethylaniline was added to the resulting diazo solution, and the mixture was stirred for 8 hours while maintaining the pH at 1.5 to 4.0 using a 15% aqueous sodium carbonate solution to complete the coupling reaction. The mixture was then salted out with sodium chloride and filtered to obtain 200 parts of a wet cake of the disazo compound represented by formula (16).

[0217] [ka]

[0218] (Process 2) 150 parts of the resulting wet cake of the monoazo compound represented by formula (16) was added to 300 parts of water, stirred, and suspended. The pH was adjusted to 9.0 using 25% sodium hydroxide, and 17.3 parts of 40% aqueous sodium nitrite solution was added thereto. The resulting aqueous solution was added dropwise to a mixture of 200 parts of water and 42 parts of 35% hydrochloric acid to prepare a diazo solution. 15.3 parts of 2,5-dimethoxyaniline was added to the resulting diazo solution, and the mixture was stirred for 8 hours while maintaining the pH at 1.5 to 4.0 using 15% aqueous sodium carbonate solution to complete the coupling reaction. The mixture was then salted out with sodium chloride and filtered to obtain 200 parts of a wet cake of the trisazo compound represented by formula (17).

[0219] [ka]

[0220] (Step 3) 200 parts of the resulting wet cake of the trisazo compound represented by formula (17) was added to 500 parts of water and stirred to form a suspension. The pH was adjusted to 9.0 using 25% sodium hydroxide, and 17.3 parts of 40% aqueous sodium nitrite solution was added thereto. The resulting suspension was added dropwise to a mixture of 100 parts of water and 42 parts of 35% hydrochloric acid to prepare a diazo solution. Meanwhile, 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid were added to 300 parts of water and dissolved in a weakly alkaline solution of 25% sodium hydroxide. The previously obtained diazo solution was added dropwise to this solution while maintaining the pH at 6.5 to 8.0, and the mixture was stirred to complete the coupling reaction. The mixture was then salted out with sodium chloride, filtered, and dried to obtain 11.0 parts of the azo compound represented by Compound Example 3-42.

[0221] [Example 8] The film obtained after the swelling treatment was treated for 8 minutes in a dyeing solution at 45°C containing 1,500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, 0.21 parts by mass of Compound Example 1-23 (an azo compound of formula (54) in WO2016 / 186194) which is an azo compound of formula (1), 0.35 parts by mass of Compound Example 3-42 obtained in Synthesis Example 7 which is an azo compound of formula (3), and 0.26 parts by mass of Compound Example 4-2 (an azo compound described in Synthesis Example 1 in WO2007 / 138980) which is an azo compound of formula (4). A polarizing plate was produced in the same manner as in Example 1, except that the azo compounds were added.

[0222] [Synthesis Example 8] 6.2 parts of an azo compound represented by Compound Example 3-35 was obtained in the same manner as in Synthesis Example 1, except that 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid in Step 3 of Synthesis Example 1 was changed to 55.1 parts of the compound represented by the following formula (18).

[0223] [ka]

[0224] [Example 9] The film obtained after the swelling treatment was treated for 8 minutes in a dyeing solution at 45°C containing 1,500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, 0.26 parts by mass of Compound Example 2-95, which is an azo compound of formula (2) obtained by a method similar to the production method described in JP-A-8-291259, 0.37 parts by mass of Compound Example 3-35, which is an azo compound of formula (3) obtained in Synthesis Example 8, and 0.25 parts by mass of Compound Example 5-88, which is an azo compound of formula (5) (an azo compound described in WO2019 / 124161, Compound Example 1-B83), to produce a polarizing plate in the same manner as in Example 1, except that the azo compounds were added.

[0225] [Example 10] The film obtained after the swelling treatment was treated for 8 minutes in a dyeing solution at 45°C containing 1,500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, 0.23 parts by mass of Compound Example 2-70, which is an azo compound of formula (2) obtained by a method similar to the production method described in JP-A-8-291259, 0.26 parts by mass of Compound Example 3-8, which is an azo compound of formula (3) obtained in Synthesis Example 1, and 0.25 parts by mass of Compound Example 5-88, which is an azo compound of formula (5) (an azo compound described in WO2019 / 124161, Compound Example 1-B83), to produce a polarizing plate in the same manner as in Example 1, except that the azo compounds were added.

[0226] [Synthesis Example 9] 9.2 parts of an azo compound represented by Compound Example 3-36 was obtained in the same manner as in Synthesis Example 1, except that 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid in Step 3 of Synthesis Example 1 was changed to 25.3 parts of 1-hydroxy-6-methylamino-3-naphthalenesulfonic acid.

[0227] [Example 11] The film obtained after the swelling treatment was treated for 8 minutes in a dyeing solution at 45°C containing 1,500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, 0.25 parts by mass of Compound Example 1-13 (azo compound of formula (28) in WO2016 / 186194), which is an azo compound of formula (1), 0.24 parts by mass of Compound Example 3-36, which is an azo compound of formula (3) obtained in Synthesis Example 9, and 0.22 parts by mass of Compound Example 5-3 (azo compound described in Compound Example 1-A4 in WO2019 / 124161), which is an azo compound of formula (5). A polarizing plate was produced in the same manner as in Example 1, except that the azo compounds were added.

[0228] [Synthesis Example 10] 8.9 parts of an azo compound represented by Compound Example 3-14 was obtained in the same manner as in Synthesis Example 1, except that 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid in Step 3 of Synthesis Example 1 was changed to 37.5 parts of 1-hydroxy-6-(2,4-dimethoxyphenylamino)-3-naphthalenesulfonic acid.

[0229] [Example 12] The film obtained after the swelling treatment was treated for 8 minutes in a dyeing solution at 45°C containing 1,500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, 0.30 parts by mass of Compound Example 2-103, which is an azo compound of formula (2) obtained by a method similar to that described in JP 2002-275381 A, 0.29 parts by mass of Compound Example 3-14, which is an azo compound of formula (3) obtained in Synthesis Example 10, and 0.21 parts by mass of Compound Example 5-84, which is an azo compound of formula (5) (an azo compound described in Compound Example 1-B64 in WO 2019 / 124161). A polarizing plate was produced in the same manner as in Example 1, except that the azo compounds were added.

[0230] [Example 13] The film obtained after the swelling treatment was treated for 8 minutes in a dyeing solution at 45°C containing 1,500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, 0.29 parts by mass of Compound Example 2-59 (Compound Example Formula (17) of WO2012 / 108169), which is an azo compound of Formula (2), 0.29 parts by mass of Compound Example 3-10, which is an azo compound of Formula (3) obtained in Synthesis Example 2, and 0.21 parts by mass of Compound Example 5-84 (an azo compound described in Compound Example 1-B64 of WO2019 / 124161), which is an azo compound of Formula (5). A polarizing plate was produced in the same manner as in Example 1, except that the azo compounds were added.

[0231] [Example 14] The film obtained after the swelling treatment was treated for 8 minutes in a dyeing solution at 45°C containing 1,500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, 0.30 parts by mass of Compound Example 2-103, which is an azo compound of formula (2) obtained by a method similar to that described in JP 2002-275381 A, 0.29 parts by mass of Compound Example 3-14, which is an azo compound of formula (3) obtained in Synthesis Example 10, and 0.20 parts by mass of CI Direct Orange 72, which is the same color component as Compound Example 5-84, an azo compound of formula (5) (an azo compound described in WO 2019 / 124161, Compound Example 1-B64), to produce a polarizing plate in the same manner as in Example 1, except that the azo compounds were added.

[0232] [Example 15] The film obtained after the swelling treatment was treated for 8 minutes in a dyeing solution at 45°C containing 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, 0.22 parts by mass of Compound Example 2-26 (an azo compound represented by formula (4) in WO2005 / 075572) which is an azo compound represented by formula (2), 0.29 parts by mass of Compound Example 3-7 (an azo compound represented by formula (3) obtained in Synthesis Example 6), and 0.30 parts by mass of CI Direct Yellow 12. A polarizing plate was produced in the same manner as in Example 1, except that the azo compound was added.

[0233] [Comparative Example 1] As a general dye-based polarizing plate, a high transmittance dye-based polarizing plate SHC-115 having a neutral gray color manufactured by Polatechno Co., Ltd. was procured and used as a measurement sample.

[0234] Comparative Example 2 As a general dye-based polarizing plate, a neutral gray dye-based polarizing plate SHC-128 manufactured by Polatechno Co., Ltd., which has high contrast, was procured and used as a measurement sample.

[0235] [Comparative Examples 3 to 8] Iodine-based polarizing plates not containing azo compounds were produced in the same manner as in the manufacturing method described in Comparative Example 1 of Patent Document 9, except that the iodine-containing time was changed to 5 minutes 30 seconds in Comparative Example 3, 4 minutes 45 seconds in Comparative Example 4, 4 minutes 15 seconds in Comparative Example 5, 3 minutes 30 seconds in Comparative Example 6, 4 minutes 00 seconds in Comparative Example 7, and 5 minutes 15 seconds in Comparative Example 8, and were used as measurement samples.

[0236] Comparative Example 9 An iodine-based polarizing plate SKW-18245P manufactured by Polatechno Co., Ltd., which exhibits a paper-white color in the parallel position, was procured and used as a measurement sample.

[0237] [Comparative Examples 10 to 11] In Example 1, the aqueous solution (dyeing solution) containing the azo compound had the composition described in Example 1 of Patent Document 3, and the dyeing time was changed to 6 minutes and 5 minutes, respectively. The time for immersing the swollen film in the aqueous solution was adjusted to incorporate the azo compound so that the single transmittance described below would be approximately 41%, and polarizing plates of Comparative Examples 10 and 11 were produced in the same manner.

[0238] [Comparative Example 12] A polarizing plate described in Example 1 of Patent Document 8 relating to a dye-based polarizing plate was prepared.

[0239] [Comparative Example 13] A polarizing plate described in Example 3 of Patent Document 9 relating to a dye-based polarizing plate was prepared.

[0240] [Comparative Example 14] A polarizing plate described in Example 1 of Patent Document 10 relating to a dye-based polarizing plate was prepared.

[0241] [Comparative Example 15] A polarizing plate described in Example 15 (No. 1) of Patent Document 11, which relates to a dye-based polarizing plate, was prepared.

[0242] [Comparative Example 16] A polarizing plate was produced in the same manner as in Example 10, except that in Example 10, CI Direct Red 80, which has dichroism of a similar color, was used instead of the azo compound of Compound Example 2-70, a dye solution was prepared so that the resulting polarizing element would have the same single transmittance, and the azo compound was incorporated into the polarizing element.

[0243] [Comparative Example 17] In Example 10, a polarizing plate was produced in the same manner as in Example 10, except that CI Direct Blue 67, a disazo compound having dichroism of similar colors, was used instead of the azo compound of Compound Example 3-8, a dye solution was prepared so that the resulting polarizing element would have the same single transmittance, and the azo compound was incorporated into the polarizing element.

[0244] [Evaluation method] The measurement samples obtained in Examples 1 to 15 and Comparative Examples 1 to 17 were evaluated as follows. (a) Single transmittance Ts, parallel transmittance Tp, and perpendicular transmittance Tc for each wavelength The single transmittance Ts, parallel transmittance Tp, and crossed transmittance Tc of each wavelength of each measurement sample were measured using a spectrophotometer (Hitachi High-Tech Science U-4100). Here, the single transmittance Ts (%) of each wavelength is the transmittance of each wavelength when a single measurement sample is used. The parallel transmittance Tp (%) of each wavelength is the spectral transmittance of each wavelength measured by overlapping two measurement samples so that their absorption axes are parallel. The crossed transmittance Tc (%) of each wavelength is the spectral transmittance measured by overlapping two measurement samples so that their absorption axes are perpendicular. Measurements were performed over a wavelength range of 380 to 780 nm. (b) Single transmittance Ys after luminosity correction, parallel transmittance Yp after luminosity correction, and perpendicular transmittance Yc after luminosity correction The luminous efficiency-corrected single transmittance Ys (%), luminous efficiency-corrected parallel transmittance Yp (%), and luminous efficiency-corrected crossed transmittance Yc (%) of each measurement sample were determined. The luminous efficiency-corrected single transmittance Ys (%), luminous efficiency-corrected parallel transmittance Yp (%), and luminous efficiency-corrected crossed transmittance Yc (%) are transmittances corrected for luminous efficiency according to JIS Z 8722:2009 for the single transmittance Ts, the parallel transmittance Tp, and the crossed transmittance Tc of each wavelength, which were determined at predetermined wavelength intervals dλ (here, 5 nm) in the wavelength range of 380 to 780 nm. Specifically, the single transmittance Ts, the parallel transmittance Tp, and the crossed transmittance Tc of each wavelength were substituted into the following formulas (I to III) to calculate the values. In the following formulas (I to III), Pλ represents the spectral distribution of standard light (light source C), and yτλ represents the color matching function for a 2-degree visual field. The results are shown in Table 1.

[0245]

number

[0246] (c) Contrast The contrast (CR) was calculated by calculating the ratio (Yp / Yc) between the parallel transmittance Yp after luminosity correction and the perpendicular transmittance Yc after luminosity correction, both measured using two identical measurement samples. The results are shown in Table 1.

[0247] (d) Degree of polarization after luminosity correction ρy The degree of polarization ρy after luminosity correction of each measurement sample was calculated by substituting the luminosity-corrected parallel transmittance Yp and the luminosity-corrected crossed transmittance Yc into the following formula (IV). The results are shown in Tables 1 and 2.

[0248]

number

[0249] [Table 1] [Table 2]

[0250] Comparing Examples 1 to 15 with Comparative Examples 1 and 10 to 17, it can be seen that the polarizing plates of the present invention have high polarization degrees and contrast, and that the single transmittance is about 1 to 2% lower than that of Comparative Example 2 when the polarization degrees and contrast are approximately the same. This shows that the polarizing plates of the present invention improve the performance of dye-based polarizing plates. Note that, as will be described later, Comparative Examples 3 to 9 provide polarizing plates with high contrast and high polarization degrees, but have low durability.

[0251] Next, the average transmittance (AT) of the parallel transmittance Tp and the crossed transmittance Tc obtained by the above measurement in the range of 420 to 480 nm was calculated. 420-480 ), average transmittance at 520-590 nm (AT 520-590 ), and the average transmittance (AT 600-640 ) are shown in Tables 3 and 4.

[0252] [Table 3] [Table 4]

[0253] (e) Absolute value of the difference in the average transmittance of the two wavelength bands The average transmittance (AT) of each sample in the parallel direction at each wavelength, Tp, and the orthogonal transmittance (Tc) at each wavelength from 520 to 590 nm 520-590 ) and the average transmittance (AT 420-480 ) and the average transmittance (AT 520-590 ) and the average transmittance (AT 600-640 The absolute value of the difference between the values ​​was measured. The results are shown in Tables 5 and 6.

[0254] [Table 5] [Table 6]

[0255] From Table 3, the measurement samples of Examples 1 to 15 have the average transmittance (AT 520-590 ) is over 32.15%, which is high. Furthermore, from Tables 3 to 6, the average transmittance (AT 520-590 ) and average transmittance (AT 420-480 ) is less than 3.0, and the average transmittance (AT 520-590 ) and average transmittance (AT 600-640 ) is smaller than 2.5. Furthermore, the measurement samples of Examples 6, 7, 12 and 14 have an average transmittance (AT 520-590 ) and average transmittance (AT 420-480 ) and the average transmittance (AT 520-590 ) and average transmittance (AT 600-640) is within 2%, and it can be seen that the difference between each wavelength band is extremely small. Furthermore, the average transmittance (AT 520-590 ) and average transmittance (AT 420-480 ) and the average transmittance (AT 520-590 ) and average transmittance (AT 600-640 ) is within 1%, and compared with Comparative Examples 1 to 9 and 12 to 17, it can be seen that the polarizing plate of the present invention has no difference between the wavelength bands even at Tc of each wavelength. On the other hand, the measurement samples of Comparative Examples 10 to 11 have a difference between the average transmittance (AT 520-590 ) and average transmittance (AT 420-480 ) is within 2.5% of the average transmittance at Tp (AT 520-590 ) and average transmittance (AT 600-640 ) is within 3.0%, and although the difference in average transmittance at Tc is 1%, the contrast and degree of polarization are low, as shown in Table 2. From the above, it can be seen that the polarizing element of the present invention can realize a polarizing element or polarizing plate that has high transmittance and high degree of polarization, yet is not wavelength dependent at Tp and Tc for each wavelength.

[0256] (f) Chromaticity a* and b* values For each sample, the chromaticity a* and b* values ​​were measured according to JIS Z 8781-4:2013 when measuring the single transmittance Ts at each wavelength, the parallel transmittance Tp at each wavelength, and the crossed transmittance Tc at each wavelength. The above-mentioned spectrophotometer was used for the measurements. Illuminant C was used as the light source. The results are shown in Tables 7 and 8. Here, a*-s and b*-s, a*-p and b*-p, and a*-c and b*-c correspond to the chromaticity a* and b* values ​​when measuring the single transmittance Ts, the parallel transmittance Tp, and the crossed transmittance Tc, respectively.

[0257] (g) Observation of color For each measurement sample, two identical samples were placed on a commercially available mirror as a reflector, one in parallel and one in perpendicular orientation, and the observed colors were investigated. Observations were performed visually by 10 observers, and the most frequently observed colors are shown in Tables 7 and 8. In the tables, the parallel-position color refers to the color when two identical samples are placed on top of each other with their absorption axis directions parallel to each other (white display), and the perpendicular-position color refers to the color when two identical samples are placed on top of each other with their absorption axis directions perpendicular to each other (black display). Basically, the color in the parallel orientation is "white" and the color in the perpendicular orientation is "black." However, in the examples and comparative examples, for example, a yellowish white is referred to as "yellow" and a bluish-purple black is referred to as "blue-purple."

[0258] [Table 7] [Table 8]

[0259] As shown in Tables 7 and 8, the measurement samples of Examples 1 to 15 had a luminosity-corrected single-unit transmittance Ys of 40% or more. Furthermore, the measurement samples of Examples 2, 7, 12, 14, and 15 all had absolute values ​​of chromaticity a*-s and b*-s of 1.0 or less, and absolute values ​​of chromaticity a*-p and b*-p of 2.0 or less. Furthermore, while having high transmittance, they also exhibited a high polarization degree of 97% or more, demonstrating that they could adequately express black and white. On the other hand, in Comparative Examples 1 to 9 and 12 to 17, the absolute values ​​of chromaticity a*-s and b*-s were all greater than 1, and the absolute values ​​of chromaticity a*-p and b*-p were all greater than 3, or at a polarization degree of 97% or less, either chromaticity a*-c or b*-c was greater than 1. This indicates that conventional polarizing elements or polarizing plates cannot adequately express black and white. Furthermore, the measurement samples of Comparative Examples 10 and 11 can adequately express black and white, but as shown in Table 2, the contrast and degree of polarization are low. From the above, it has been shown that the polarizing element of the present invention can realize a polarizing element or polarizing plate that has high transmittance and high polarization degree, and can be designed to be able to fully express achromatic colors, i.e., black and white, in both the parallel and perpendicular directions.

[0260] From the above, it has been shown that the polarizing element of the present invention can express a high-quality paper-like white color in the parallel position while maintaining high single transmittance and parallel transmittance, and has a hue having a high-quality neutral color (achromatic neutral gray) without coloration in the single position. Furthermore, it can be seen that the polarizing element of the present invention maintains a high single transmittance after luminosity correction, expresses achromaticity in the parallel position, and also has a high degree of polarization. Furthermore, it can be seen that the polarizing element of the present invention can produce a polarizing element that exhibits a high-quality achromatic black in the perpendicular position.

[0261] (h) Durability test Durability tests were conducted on the measurement samples of Examples 1 to 17 and Comparative Examples 3 to 9 by placing them in an environment of 85% RH and 85°C for 240 hours. As a result, no changes in transmittance or hue were observed for the measurement samples of Examples 1 to 17. In contrast, the measurement samples of Comparative Examples 3 to 9 showed a decrease in polarization degree of 10% or more, a chromaticity b*-c value below -10, and a noticeable change in apparent color to blue. In particular, when two measurement samples were arranged orthogonally (during black display), the color was significantly bluer. This demonstrates that the polarizing element of the present invention has high durability. [Industrial Applicability]

[0262] The polarizing element or polarizing plate of the present invention can be used in liquid crystal display devices, such as reflective liquid crystal display devices and semi-transmissive liquid crystal display devices, as well as in organic electroluminescence devices other than liquid crystal display devices. A liquid crystal display device equipped with the polarizing element or polarizing plate of the present invention can display high-quality paper-like white and neutral black. Furthermore, the liquid crystal display device can be used as a liquid crystal display device that has high durability and reliability, long-term high contrast, and high color reproducibility.

Claims

1. A polarizing element comprising an azo compound represented by the following formula (1) or a salt thereof, or an azo compound represented by the following formula (2) or a salt thereof, in the form of a free acid, and an azo compound represented by the following formula (3) or a salt thereof: 【Chemistry 1】 (In formula (1), Ac １ Rc each independently represents a phenyl group or a naphthyl group having at least one substituent selected from a sulfo group and a carboxy group; １１ ~Rc １４ each independently represents a hydrogen atom, a C1-4 alkyl group, a C1-4 alkoxy group, or a C1-4 alkoxy group having a sulfo group. 【Chemistry 2】 (In formula (2), Ac ２ represents a phenyl group or a naphthyl group having at least one substituent selected from a sulfo group and a carboxy group; ２１ ~Rc ２８ each independently represents a hydrogen atom, a C1-4 alkyl group, a C1-4 alkoxy group, or a C1-4 alkoxy group having a sulfo group; ２ represents an amino group which may have at least one substituent S2, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a naphthotriazole group which may have a substituent, or a benzoylamino group which may have a substituent, ２ are (each independently when there are a plurality of groups) selected from a C1-4 alkyl group, a C1-4 alkoxy group, a sulfo group, a C1-4 alkylamino group, a hydroxy group, an amino group, a substituted amino group, a carboxy group, and a carboxyethylamino group, which may further have a substituent, and r, p, and q each independently represent 0 or 1. However, except when r, p, and q are all 1, when either p or q is 1 and Ac ２ is a naphthyl group, it does not contain a hydroxy group as a substituent.) 【Transformation 3】 In formula (3), any of the hydrogen atoms in ring a and ring b is substituted with Ra 1 , Ra 2 , Ab 1 or Ab 2 , and １ or Ra ２ one of A and B represents a hydroxy group, and the other represents a hydrogen atom, a hydroxy group, a C1-4 alkoxy group, or a C1-4 alkoxy group having a sulfo group; Ab １ or Ab ２ one of them represents a sulfo group, a carboxy group, or an amino group which may have a substituent, and the other represents a hydrogen atom, a sulfo group, a carboxy group, or an amino group which may have a substituent, and Rb １ ~Rb ６ each independently represents a hydrogen atom, a C1-4 alkyl group, a C1-4 alkoxy group, a sulfo group, a C1-4 alkoxy group having a sulfo group, or an amino group which may have a substituent; h represents 0 or 1; Xb １ is a substituent S ３ and the substituent S ３ (When there are a plurality of groups, each group is independently selected from a C1-4 alkyl group, a C1-4 alkoxy group, a sulfo group, an amino group, a C1-4 alkylamino group, a hydroxy group, a carboxy group, and a carboxyethylamino group, which may further have a substituent.)

2. 2. The polarizing element according to claim 1, further comprising an azo compound represented by the following formula (4) or a salt thereof, or an azo compound represented by the following formula (5) or a salt thereof: 【Chemistry 4】 (In formula (4), Ay １１ each independently represents a sulfo group, a carboxy group, a hydroxy group, a C1-4 alkyl group, or a C1-4 alkoxy group; Ry １１ ~Ry １４ each independently represents a hydrogen atom, a C1-4 alkyl group, a C1-4 alkoxy group, or a C1-4 alkoxy group having a sulfo group, and f represents an integer of 1 to 3. 【Transformation 5】 (In formula (5), Ay ２１ and Ay ２２ each independently represents a naphthyl group which may have a substituent or a phenyl group which may have a substituent, and Ry ２１ , Ry ２２ , Ry ２７ , and Ry ２８ are each independently a hydrogen atom, a C1-4 alkyl group, or a C1-4 alkoxy group, and Ry ２３ ~Ry ２６ each independently represents a hydrogen atom, a C1-4 alkyl group, a C1-4 alkoxy group, or a C1-4 alkoxy group having a sulfo group, and s and t each independently represent 0 or 1.

3. 3. The polarizing element according to claim 1, wherein the azo compound represented by formula (3) or the salt thereof is an azo compound represented by formula (6) below or a salt thereof: 【Transformation 6】 (In formula (6), Ra １ , Ra ２ , Ab １ , Ab ２ , Rb １ ~Rb ６ , h, Xb １ have the same meaning as in formula (3).

4. 4. The polarizing element according to claim 1, wherein the azo compound represented by formula (3) or a salt thereof is an azo compound represented by formula (7) below or a salt thereof: 【Transformation 7】 (In formula (7), Ra １ , Ra ２ , Ab １ , Ab ２ , Rb １ ~Rb ６ , h, Xb １ have the same meaning as in formula (3).

5. 5. The polarizing element according to claim 1, wherein the azo compound represented by formula (3) or a salt thereof is an azo compound represented by formula (8) below or a salt thereof: 【Transformation 8】 (In formula (8), Ra １ , Ab １ , Rb １ ~Rb ６ , h, Xb １ have the same meaning as in formula (3), and Ra ３ represents a hydrogen atom or a hydroxy group.)

6. 6. The polarizing element according to claim 1, wherein the azo compound represented by formula (3) or a salt thereof is an azo compound represented by formula (9) below or a salt thereof: 【Chemistry 9】 (In the formula (9), Ra １ , Ab １ , Rb １ ~Rb ６ , h, Xb １ have the same meaning as in formula (2).

7. The polarizing element according to any one of claims 1 to 6, wherein, in the transmittance at each wavelength determined by measuring two polarizing elements stacked such that the absorption axis directions of the respective elements are parallel to each other, the difference in absolute value between the average transmittance at 420 nm to 480 nm and the average transmittance at 520 nm to 590 nm is 2.5% or less, and the difference in absolute value between the average transmittance at 520 nm to 590 nm and the average transmittance at 600 nm to 640 nm is 3.0% or less.

8. The polarizing element according to any one of claims 1 to 7, wherein the absolute values ​​of the a* value and the b* value of the polarizing element alone, as determined when the transmittance is measured using natural light in accordance with JIS Z 8781-4:2013, are both 1.0 or less.

9. The polarizing element according to any one of claims 1 to 8, wherein the a* value obtained by measuring the transmittance using natural light in accordance with JIS Z 8781-4:2013 when two polarizing elements are stacked and arranged so that the absorption axis directions of the respective polarizing elements are parallel to each other is -2.0 to 2.0, and the absolute value of the b* value is -2.0 to 3.

0.

10. The polarizing element according to any one of claims 1 to 9, wherein the polarizing element has a single transmittance of 35% to 65% after luminosity correction, and when two polarizing elements are stacked and arranged so that the absorption axis directions of the respective polarizing elements are parallel to each other, the average transmittance in the wavelength band of 520 nm to 590 nm is 25% to 50%.

11. The polarizing element according to any one of claims 1 to 10, wherein, when two polarizing elements are stacked and arranged so that the absorption axis directions of the respective polarizing elements are perpendicular to each other, the difference between the average transmittance in the range of 420 nm to 480 nm and the average transmittance in the range of 520 nm to 590 nm is 1.0% or less as an absolute value, and the difference between the average transmittance in the range of 520 nm to 590 nm and the average transmittance in the range of 600 nm to 640 nm is 1.0% or less as an absolute value.

12. The polarizing element according to any one of claims 1 to 11, wherein, when two polarizing elements are stacked and arranged so that the absorption axis directions of the two polarizing elements are perpendicular to each other, the orthogonal transmittance at each wavelength in the wavelength bands of 420 nm to 480 nm, 520 nm to 590 nm, and 600 nm to 640 nm is 1% or less, or the degree of polarization after luminous efficiency correction is 97% or more.

13. The polarizing element according to any one of claims 1 to 12, wherein, when two polarizing elements are stacked so that the absorption axis directions of the respective polarizing elements are perpendicular to each other, the absolute values ​​of the a* value and the b* value when the transmittance is measured using natural light in accordance with JIS Z 8781-4:2013 are both 2.0 or less.

14. The polarizing element according to any one of claims 1 to 13, comprising a substrate.

15. The polarizing element according to claim 14 , comprising a polyvinyl alcohol-based resin film as a substrate.

16. A polarizing plate comprising the polarizing element according to any one of claims 1 to 15 and a transparent protective layer provided on one or both sides of the polarizing element.

17. A display device comprising the polarizing element according to any one of claims 1 to 15 or the polarizing plate according to claim 16.

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