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

Abstract

The polarizing element of the present application contains 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, and an azo compound represented by the following formula (3) or a salt thereof, in the form of a free acid.

Description

Technical Field

[0001] This invention relates to a dye-based polarizing element, a polarizing plate, and a display device (display) equipped with the polarizing plate. Background Technology

[0002] Polarizing elements are generally manufactured by adsorbing and aligning iodine, a dichroic pigment, or a dichroic dye onto a polyvinyl alcohol-based resin film. A polarizing plate, obtained by bonding a protective film made of cellulose triacetate or similar material to this polarizing element through an adhesive layer, can be used in liquid crystal display devices, etc. Polarizing plates made using iodine as a dichroic pigment are called iodine-based polarizing plates; on the other hand, polarizing plates made using dichroic dyes, such as dichroic azo compounds, are called dye-based polarizing plates. Dye-based polarizing plates have properties such as high heat resistance, high damp heat durability, and high stability. Furthermore, the color selectivity obtained by adjusting the pigment is higher. However, compared to iodine-based polarizing plates with the same polarization degree, they still have lower transmittance and contrast. Therefore, in addition to maintaining high durability and diverse color selectivity, polarizing elements with higher transmittance and high polarization characteristics are desired.

[0003] Furthermore, even with dye-based polarizing plates that offer diverse color selectivity, current polarizing elements, when overlapped in a parallel configuration (hereinafter referred to as "parallel position") along their absorption axes to display white (hereinafter referred to as "white display" or "bright display"), exhibit a yellowish tint. Additionally, even with polarizing elements designed to suppress this yellow tint, current polarizing plates, when overlapped in an orthogonal configuration (hereinafter referred to as "orthogonal position") along their absorption axes to display black (hereinafter referred to as "black display" or "dark display"), exhibit a bluish tint. Therefore, a polarizing plate that displays achromatic white when white is displayed and black when black is displayed is sought. Particularly difficult to obtain is a polarizing plate that provides high-quality white when displaying white, commonly referred to as a paper white polarizing plate. Furthermore, in order to make the polarizing plate colorless, the transmittance of each wavelength must be almost constant regardless of the wavelength in the parallel or quadrature positions, but such a polarizing plate has not yet been obtained.

[0004] The reason why the hue of white and black displays differs is due to the different wavelength dependence of transmittance in parallel and orthogonal positions. In particular, transmittance is not constant in the visible light region. Furthermore, the non-constant dichroism in the visible light region is also one of the reasons why it is difficult to achieve colorless polarizers.

[0005] Taking an iodine-based polarizing plate as an example, an iodine-based polarizing plate made with polyvinyl alcohol (hereinafter also referred to as "PVA") as the substrate and iodine as the dichroic pigment generally exhibits absorption in the regions centered at 480nm and 600nm. The absorption at 480nm can be attributed to polyiodine I3. - The absorption at 600 nm in the complex with PVA is attributed to polyiodine I5. - A complex with PVA. Regarding polarization (dichroism) at various wavelengths, based on polyiodine I5... - The polarization (dichroism) of the complex with PVA is higher than that based on polyiodine I3. - The polarization (dichroism) of the PVA complex. Specifically, if the transmittance at the cross-cutting position is to be constant across wavelengths, the transmittance at the parallel position is higher at 600nm compared to 480nm, resulting in white appearing yellowish when displayed. Conversely, if the transmittance at the parallel position is to be constant, the transmittance at the cross-cutting position is lower at 600nm compared to 480nm, resulting in black appearing blueish when displayed. The yellowish appearance of white generally creates the impression of ongoing degradation, making it less than ideal. Furthermore, the blue tint in black, lacking a clear black, creates an impression of low quality. Additionally, in iodine-based polarizers, the hue is difficult to control near 550nm, where visual sensitivity is primarily high, due to the lack of a complex based on its wavelength. Thus, because the polarization (dichroism) is not constant across wavelengths, wavelength dependence of the polarization (dichroism) occurs. In addition, since the pigments produced by the complex of iodine and PVA have only two dichroic absorptions at 480nm and 600nm, the hue cannot be adjusted on an iodine-based polarizing plate composed of iodine and PVA.

[0006] Methods for improving the hue of iodine-based polarizing plates have been described in Patent Document 1 or Patent Document 2. Patent Document 1 describes a polarizing plate with a calculated neutral density coefficient and an absolute value of 0 to 3. Patent Document 2 describes a polarizing element whose transmittance in the 410 nm to 750 nm range is set within ±30% of its average value, and which, in addition to iodine, is colored by adding direct dyes, reactive dyes, or acid dyes. Furthermore, Patent Document 3 discloses a technique for a colorless dyed polarizing plate.

[0007] However, the polarizing plate of Patent Document 1, as can be seen from its embodiment 1, even with a low neutral density coefficient (Np), has an a* value of -1.67 and a b* value of 3.51 in the parallel hues obtained from JIS Z 8729, thus displaying a yellowish-green color when white is shown. Furthermore, although the a* value of the orthogonal hue is 0.69, the b* value is -3.40, resulting in a polarizing plate that displays a blue color when black is shown. The polarizing element of Patent Document 2 is obtained by setting the a* and b* values ​​in the UCS color space, measured using only a single polarizing element, to an absolute value of 2 or less, and cannot simultaneously represent achromatic colors in both white and black hues when two polarizing elements are overlapped. Additionally, the average transmittance of the polarizing element in Patent Document 2 is relatively low, at 31.95% in Embodiment 1 and 31.41% in Embodiment 2. Therefore, the polarizing element in Patent Document 2 has low transmittance, making it insufficient for applications requiring high transmittance and high contrast, particularly in liquid crystal display devices and organic electroluminescent devices. Furthermore, the polarizing element in Patent Document 2 is made using iodine as the primary dichroic pigment, resulting in significant color changes and poor durability after durability testing, especially after damp heat durability testing (e.g., at 85°C and 85% relative humidity).

[0008] On the other hand, while dye-based polarizers exhibit excellent durability, their wavelength dependence differs between parallel and crosshair positions, unlike iodine-based polarizers. Dichroic azo compounds that display the same hue in parallel and crosshair positions are almost nonexistent, and even if they exist, their dichroism (polarizing properties) is low. Depending on the type of dichroic azo compound, there are also compounds that display white as yellow and black as blue, exhibiting completely different wavelength dependencies in crosshair and parallel positions. Furthermore, since human color perception varies with light intensity, even assuming color correction for dye-based polarizers, separate color corrections suitable for controlling the light intensity produced by polarization in both crosshair and parallel positions are necessary. If the non-transmittance is approximately constant across all wavelengths and exhibits no wavelength dependence in both parallel and crosshair positions, an achromatic polarizer cannot be achieved. Furthermore, in order to obtain a polarizing element with high transmittance and high contrast, in addition to meeting certain transmittance requirements at both the parallel and quadrature positions, the polarization degree (dichroism ratio) at each wavelength must be high and constant. When using an azo compound to fabricate a polarizing element, although the wavelength dependence of transmittance at each wavelength differs between the quadrature and parallel positions, in order to achieve a certain transmittance at each wavelength by blending two or more azo compounds, the transmittance at both the parallel and quadrature positions of each compound must be considered, and the relationship between the dichroism ratios of the two or more compounds must be precisely controlled.

[0009] On the other hand, even assuming precise control over the relationship between transmittance and dichroism ratio at each wavelength in parallel and quadrature positions, and setting transmittance constant across all wavelengths, high transmittance and high contrast are still not achievable. In other words, the higher the transmittance or polarization, the more difficult it is to achieve achromaticity, making it impossible to create a colorless polarizer with high transmittance or high polarization. Colorless polarizers with high transmittance and / or high contrast are extremely difficult to obtain, and cannot be achieved simply by using dichroic pigments with the three primary colors. In particular, it is extremely difficult to simultaneously achieve a certain transmittance and high dichroism at each wavelength in parallel positions. Even if white has only a slight tint of other colors, high-quality white cannot be represented. Furthermore, white in its bright state has high brightness and high sensitivity, making it particularly important. Therefore, for polarizing elements, it is required to display a colorless white like high-quality paper when displaying white, a colorless black when displaying black, and to have a single-unit transmittance of 35% or higher after visual sensitivity correction, as well as high polarization. Patent document 3 describes a colorless polarizing plate for both white and black displays, but further performance improvements are desired.

[0010] [Existing Technical Documents]

[0011] [Patent Literature]

[0012] [Patent Document 1] Japanese Patent Application Publication No. 2002-169024

[0013] [Patent Document 2] Japanese Patent Application Publication No. 10-133016

[0014] [Patent Document 3] WO2014 / 162635 Publication No.

[0015] [Patent Document 4] Japanese Patent Application Publication No. 2006-182846

[0016] [Patent Document 5] Japanese Patent Application Publication No. 2007-084803

[0017] [Patent Document 6] WO2016 / 186194 Publication No.

[0018] [Patent Document 7] WO2016 / 186195 Publication No.

[0019] [Patent Document 8] Japanese Patent Application Publication No. 11-218611

[0020] [Patent Document 9] Japanese Patent Application Publication No. 2001-033627

[0021] [Patent Document 10] Japanese Patent Application Publication No. 2004-251962

[0022] [Patent Document 11] Japanese Patent Application Publication No. 8-291259.

[0023] [Non-patent literature]

[0024] [Non-Patent Literature 1] Dye Chemistry; by Toyoda Hosoda, Gihodo Publishing, 1957, p. 621

[0025] [Non-Patent Literature 2] Application of Functional Pigments, CMC (Stock) Publishing, First Printing, supervised by Masahiro Irie, pp. 98-100. Summary of the Invention

[0026] [The problem the invention aims to solve]

[0027] Therefore, one aspect of the present invention aims to provide a polarizing element or polarizing plate thereof having high transmittance and high polarization. Another aspect provides a high-performance polarizing element or polarizing plate and display device that is achromatic when displayed in white, or achromatic when displayed in both white and black modes, and particularly, that displays high-quality white when displayed in white.

[0028] [Methods used to solve problems]

[0029] As a result of the inventors’ efforts to solve the above-mentioned problems, they discovered that the present invention is accomplished by using a polarizing element or polarizing plate containing at least the azo compound shown in formula (1) or the azo compound shown in formula (2) and the azo compound shown in formula (3) in the manufacture.

[0030] That is, this invention relates to, but is not limited to, the following [Invention 1] to [Invention 17].

[0031] [Invention 1]

[0032] A polarizing element comprising, in the form of a free acid, an azo compound or a salt thereof as shown in formula (1), or an azo compound or a salt thereof as shown in formula (2), and an azo compound or a salt thereof as shown in formula (3).

[0033]

[0034] In formula (1), Ac1 independently represents a phenyl or naphthyl group having at least one substituent selected from sulfonic acid and carboxyl groups, and Rc 11 To Rc 14 (Each of the following can be independently represented: hydrogen atom, C1 to 4 alkyl group, C1 to 4 alkoxy group, or C1 to 4 alkoxy group having a sulfonic acid group)

[0035]

[0036] (In formula (2), Ac2 represents a phenyl or naphthyl group having at least one substituent selected from sulfonic acid and carboxyl groups, Rc 21To Rc 28 Each of these groups independently represents a hydrogen atom, a C1 to 4 alkyl group, a C1 to 4 alkoxy group, or a C1 to 4 alkoxy group having a sulfonic acid group. Xc2 represents an amino group that may have at least one substituent S2, a phenylamino group that may have a substituent, a phenylazo group that may have a substituent, a naphthotriazolyl group that may have a substituent, or a benzoylamino group that may have a substituent. Substituent S2 (if there are multiple substituents, each independently) is further selected from C1 to 4 alkyl groups, C1 to 4 alkoxy groups, sulfonic acid groups, C1 to 4 alkylamino groups, hydroxyl groups, amino groups, substituted amino groups, carboxyl groups, and carboxyethylamino groups that may have a substituent. r, p, and q independently represent 0 or 1, but exclude the case where r, p, and q are all 1. In addition, only either p or q is 1, and when Ac2 is a naphthyl group, it does not contain a hydroxyl group as a substituent.

[0037]

[0038] In formula (3), Ra1, Ra2, Ab1, or Ab2 may be substituted on either ring a or ring b; either Ra1 or Ra2 is a hydroxyl group, and the other represents a hydrogen atom, a hydroxyl group, a C1 to C4 alkoxy group, or a C1 to C4 alkoxy group having a sulfonic acid group; either Ab1 or Ab2 represents a sulfonic acid group, a carboxyl group, or an amino group that may have a substituent; the other is a substituent selected from a hydrogen atom, a sulfonic acid group, a carboxyl group, or an amino group that may have a substituent; and Rb1 to Rb6 independently represent a hydrogen atom, a C1 to C4 alkyl group, or a C1 to C4 alkoxy group. The group consists of a sulfonic acid group, a C1 to C4 alkoxy group having a sulfonic acid group, or an amino group that may have a substituent, where h represents 0 or 1, and Xb1 represents an amino group that may have at least one substituent S3, a phenylamino group that may have a substituent, a phenylazo group that may have a substituent, a naphthotriazolyl group that may have a substituent, or a benzoylamino group that may have a substituent, wherein the substituent S3 (if there are multiple substituents, each independently) is further selected from C1 to C4 alkyl groups, C1 to C4 alkoxy groups, sulfonic acid groups, amino groups, C1 to C4 alkylamino groups, hydroxyl groups, carboxyl groups, and carboxyethylamino groups that may have a substituent.

[0039] [Invention 2]

[0040] The polarizing element as described in Invention 1 further comprises an azo compound or a salt thereof as shown in Formula (4) or an azo compound or a salt thereof as shown in Formula (5).

[0041]

[0042] (In equation (4), Ay) 11 Each of the following groups independently represents a sulfonic acid group, a carboxyl group, a hydroxyl group, a C1 to C4 alkyl group, or a C1 to C4 alkoxy group, Ry 11 To Ry 14Each of the following can be independently represented: a hydrogen atom, a C1 to C4 alkyl group, a C1 to C4 alkoxy group, or a C1 to C4 alkoxy group having a sulfonic acid group, where f represents an integer from 1 to 3.

[0043]

[0044] (In equation (5), Ay) 21 and Ay 22 Ry can be independently a naphthyl group that may have substituents or a phenyl group that may have substituents. 21 Ry 22 Ry 27 and Ry 28 Ry is independently composed of a hydrogen atom, a C1 to 4 alkyl group, and a C1 to 4 alkoxy group. 23 To Ry 26 Each of the following is independently represented by a hydrogen atom, a C1 to C4 alkyl group, a C1 to C4 alkoxy group, or a C1 to C4 alkoxy group with a sulfonic acid group, and s and t independently represent 0 or 1 respectively.

[0045] [Invention 3]

[0046] The polarizing element as described in invention 1 or 2, wherein the azo compound or its salt represented by formula (3) above is the azo compound or its salt represented by formula (6) below.

[0047]

[0048] (In equation (6), Ra1, Ra2, Ab1, Ab2, Rb1 to Rb6, h, and Xb1 respectively represent the same meaning as in equation (3))

[0049] [Invention 4]

[0050] The polarizing element as described in any one of inventions 1 to 3, wherein the azo compound or salt thereof represented by the aforementioned formula (3) is the azo compound or salt thereof represented by the following formula (7).

[0051]

[0052] (In equation (7), Ra1, Ra2, Ab1, Ab2, Rb1 to Rb6, h, and Xb1 represent the same meaning as in equation (3).)

[0053] [Invention 5]

[0054] The polarizing element as described in any one of inventions 1 to 4, wherein the azo compound or its salt represented by the aforementioned formula (3) is the azo compound or its salt represented by the following formula (8).

[0055]

[0056] (In formula (8), Ra1, Ab1, Rb1 to Rb6, h, and Xb1 have the same meaning as in formula (3), and Ra3 represents a hydrogen atom or a hydroxyl group.)

[0057] [Invention 6]

[0058] The polarizing element as described in any one of inventions 1 to 5, wherein the azo compound or its salt represented by the aforementioned formula (3) is the azo compound or its salt represented by the following formula (9).

[0059]

[0060] (In the aforementioned equation (9), Ra1, Ab1, Rb1 to Rb6, h, and Xb1 respectively represent the same meaning as in equation (2))

[0061] [Invention 7]

[0062] The polarizing element according to any one of inventions 1 to 6, wherein, in the transmittance of each wavelength obtained by overlapping two polarizing elements in such a way that their respective absorption axis directions are parallel to each other, the absolute value of the difference between the average transmittance of 420nm to 480nm and the average transmittance of 520nm to 590nm is 2.5% or less, and the absolute value of the difference between the average transmittance of 520nm to 590nm and the average transmittance of 600nm to 640nm is 3.0% or less.

[0063] [Invention 8]

[0064] The polarizing element as described in any one of inventions 1 to 7, wherein, according to JIS Z 8781-4:2013, the absolute values ​​of a* and b* in the polarizing element monomer obtained by measuring the transmittance using natural light are both 1.0 or less.

[0065] [Invention 9]

[0066] The polarizing element as described in any one of inventions 1 to 8, wherein, in a state in which two polarizing elements are arranged in an overlapping manner with their respective absorption axis directions parallel to each other, the a* value obtained when measuring the transmittance using natural light according to JIS Z8781-4:2013 is -2.0 to 2.0, and the b* value is -2.0 to 3.0.

[0067] [Invention 10]

[0068] The polarizing element as described in any one of inventions 1 to 9, wherein the transmittance of a single polarizing element after visual sensitivity correction is 35% to 65%, and the average transmittance of the wavelength band 520 nm to 590 nm is 25% to 50% when two polarizing elements are overlapped in such a way that their respective absorption axis directions are parallel to each other.

[0069] [Invention 11]

[0070] The polarizing element according to any one of inventions 1 to 10, wherein, in a state in which two polarizing elements are arranged in an overlapping manner with their respective absorption axis directions orthogonal to each other, the absolute value of the difference between the average transmittance of 420 nm to 480 nm and the average transmittance of 520 nm to 590 nm is 1.0% or less, and the absolute value of the difference between the average transmittance of 520 nm to 590 nm and the average transmittance of 600 nm to 640 nm is 1.0% or less.

[0071] [Invention 12]

[0072] The polarizing element as described in any one of inventions 1 to 11, wherein, in a state in which two polarizing elements are arranged to overlap in a manner in which their respective absorption axis directions are orthogonal to each other, the transverse transmittance of any one of the wavelengths in the wavelength bands of 420nm to 480nm, 520nm to 590nm and 600nm to 640nm is 1% or less, or the polarization after visual sensitivity correction is 97% or more.

[0073] [Invention 13]

[0074] The polarizing element according to any one of inventions 1 to 12, wherein, in a state in which two polarizing elements are arranged in an overlapping manner with their respective absorption axis directions being orthogonal to each other, the absolute values ​​of a* and b* obtained when measuring the transmittance of natural light according to JIS Z8781-4:2013 are both 2.0 or less.

[0075] [Invention 14]

[0076] The polarizing element as described in any one of inventions 1 to 13 comprises a substrate.

[0077] [Invention 15]

[0078] The polarizing element as described in Invention 14 comprises a polyvinyl alcohol-based resin film as a substrate.

[0079] [Invention 16]

[0080] A polarizing plate having a transparent protective layer disposed on one or both sides of the polarizing element described in any one of inventions 1 to 15.

[0081] [Invention 17]

[0082] A display device comprising a polarizing element as described in any one of inventions 1 to 15 or a polarizing plate as described in invention 16.

[0083] [Invention Effects]

[0084] The polarizing element or polarizing plate of the present invention has high transmittance and high polarization. In another embodiment, the polarizing element of the present invention further has the following characteristics: in parallel positions or both parallel and quadrature positions, dichroism is wavelength-independent, and transmittance is constant. In another embodiment, the polarizing element of the present invention has achromatic hue in both white and black displays. In yet another embodiment, the polarizing element or polarizing plate of the present invention has high durability. Detailed Implementation

[0085] In this application specification and claims, except where the free form is explicitly indicated, there are also instances where "azo compound or its salt" is simply referred to as "azo compound".

[0086] In the claims and description of this application, "substituent" may include hydrogen atoms, therefore, for convenience, hydrogen atoms are sometimes described as "substituent". The phrase "may have substituents" also includes cases where no substituents are present. For example, "phenyl that may have substituents" includes unsubstituted phenyl and substituted phenyl. Furthermore, unless otherwise specified, the term "lower" in this application for lower alkyl, lower alkoxy, etc., indicates a carbon number of 1 to 4 (C1 to 4), preferably 1 to 3 (C1 to 3).

[0087] The above-mentioned "C1 to 4 aliphatic hydrocarbon groups" can be exemplified by: straight-chain alkyl groups such as methyl, ethyl, n-propyl, and n-butyl; split-chain alkyl groups such as sec-butyl and tert-butyl; and unsaturated hydrocarbon groups such as vinyl.

[0088] Examples of "C1 to 4 alkoxy groups" mentioned above include: methoxy, ethoxy, propoxy, n-butoxy, sec-butoxy, tert-butoxy, etc.

[0089] <Polarizing element>

[0090] The polarizing element of the present invention comprises an azo compound or a salt thereof as shown in formula (1), or an azo compound or a salt thereof as shown in formula (2), and an azo compound as shown in formula (3). Additionally, it may further comprise an azo compound as shown in formula (4) or an azo compound as shown in formula (5).

[0091] The polarizing element of the present invention preferably comprises a substrate, and the substrate contains the aforementioned azo compound. The substrate is preferably a film obtained by forming a film from a hydrophilic polymer capable of adsorbing dichroic pigments, especially azo compounds. The hydrophilic polymer is not particularly limited, and may include, for example, polyvinyl alcohol resins, amylose resins, starch resins, cellulose resins, and polyacrylate resins. From the viewpoints of dyeability, processability, and crosslinking properties of dichroic pigments, hydrophilic polymers are most preferably polyvinyl alcohol resins and their derivatives. The polarizing element can be manufactured by adsorbing the azo compound onto the substrate and applying alignment treatments such as stretching.

[0092] First, the azo compound represented by the following formula (1) will be explained.

[0093]

[0094] In formula (1), Ac1 independently represents a phenyl or naphthyl group having at least one substituent selected from sulfonic acid and carboxyl groups, and Rc 11 To Rc 14 (Each of the following can be independently represented: hydrogen atom, C1 to 4 alkyl group, C1 to 4 alkoxy group, or C1 to 4 alkoxy group having a sulfonic acid group)

[0095] In formula (1) above, when Ac1 is a phenyl group, its substituents can be listed as: sulfonic acid group, carboxyl group, lower alkyl group, lower alkoxy group, lower alkoxy group having a sulfonic acid group, nitro group, amino group, acetylamino group, and amino group substituted with a lower alkylamino group, preferably having at least one sulfonic acid group or carboxyl group. When the phenyl group has two or more substituents, at least one of its substituents is a sulfonic acid group or carboxyl group, and the other substituents are preferably selected from sulfonic acid group, carboxyl group, lower alkyl group, lower alkoxy group, lower alkoxy group having a sulfonic acid group, nitro group, amino group, acetylamino group, and amino group substituted with a lower alkylamino group, more preferably selected from sulfonic acid group, methyl group, ethyl group, methoxy group, ethoxy group, carboxyl group, nitro group, and amino group, and particularly preferably selected from sulfonic acid group, methyl group, methoxy group, ethoxy group, and carboxyl group. The lower alkoxy group having a sulfonic acid group is preferably a straight-chain alkoxy group, and the substitution position of the sulfonic acid group is preferably at the end of the alkoxy group. The lower alkoxy group having a sulfonic acid group is more preferably 3-sulfonopropoxy or 4-sulfonobutoxy, and particularly preferably 3-sulfonopropoxy. When the phenyl group has a sulfonic acid group as a substituent, it is preferred that there is one or two sulfonic acid groups. There is no particular limitation on the substitution position of the sulfonic acid group, but when there is one sulfonic acid group, it is preferred that the azo group is at position 1 and the phenyl group is at position 4; when there are two sulfonic acid groups, it is preferred that the phenyl group is at positions 2 and 4 or at positions 3 and 5.

[0096] In formula (1) above, when Ac1 is naphthyl, its substituents can include sulfonic acid group, hydroxyl group, carboxyl group, and lower alkoxy group having sulfonic acid group, and it is more preferably to have at least one sulfonic acid group. When naphthyl has two or more substituents, at least one of its substituents is sulfonic acid group, and the other substituents are more preferably selected from sulfonic acid group, hydroxyl group, carboxyl group, and lower alkoxy group having sulfonic acid group. The lower alkoxy group having sulfonic acid group is preferably a straight-chain alkoxy, and the substitution position of the sulfonic acid group is preferably at the end of the alkoxy group. Such a lower alkoxy group having sulfonic acid group is more preferably 3-sulfonylpropoxy or 4-sulfonylbutoxy, and particularly preferably 3-sulfonylpropoxy. When the number of sulfonic acid groups substituted by naphthyl is 2, the position of azo group is taken as the 2 position, and the substitution position of the sulfonic acid group is preferably a combination of the 4 and 8 positions of naphthyl or a combination of the 6 and 8 positions, and the combination of the 6 and 8 positions is more preferably. When the number of sulfonic acid groups substituted by the naphthyl group is 3, the substitution positions of the sulfonic acid groups are preferably a combination of positions 1, 3, and 6; the combination of positions 3, 6, and 8 is preferred.

[0097] In equation (1) above, Rc 11 To Rc 14 Each of these can be independently represented by a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfonic acid group. For lower alkoxy groups having a sulfonic acid group, a straight-chain alkoxy group is preferred; furthermore, the substitution position of the sulfonic acid group is preferred at the end of the alkoxy group. Rc 11 To Rc 14 More preferably, each of the following is independently a hydrogen atom, methyl, ethyl, methoxy, ethoxy, 3-sulfonylpropoxy, or 4-sulfonylbutoxy; particularly preferably, it is a hydrogen atom, methyl, methoxy, or 3-sulfonylpropoxy. Rc 11 To Rc 14 When the substitution position of the substituted phenyl group is taken as the 1-position of the azo group on the urea skeleton side, it is more preferably at only the 2-position, only the 5-position, a combination of 2-position and 6-position, a combination of 2-position and 5-position, or a combination of 3-position and 5-position, and particularly preferably at only the 2-position, only the 5-position, or a combination of 2-position and 5-position. Furthermore, the terms "only the 2-position" and "only the 5-position" refer to the substitution position at Rc. 11 With Rc 12 、Rc 13 With Rc 14 In the relationship, Rc 11 With Rc 12 or Rc 13 With Rc 14 Either of them has a substituent other than a hydrogen atom at the 2 or 5 position, and the other is a hydrogen atom.

[0098] Of the azo compounds shown in formula (1) above, the azo compound shown in formula (1b) below is particularly preferred. By using such an azo compound, the polarization performance of the polarizing element can be further improved.

[0099]

[0100] (where Ac1 and Rc are in the formula) 11 To Rc 14 (These respectively represent the same meaning as equation (1))

[0101] The azo compound shown in formula (1) or formula (1b) above can be manufactured, for example, by means of diazotization or ureidation as disclosed in patent documents 4 to 7, but is not limited to these methods.

[0102] Specific examples of the azo compounds shown in formula (1) can be listed below in the form of free acids.

[0103]

[0104]

[0105]

[0106]

[0107] The following describes the azo compound represented by formula (2).

[0108]

[0109] In formula (2), Ac2 represents a phenyl or naphthyl group having at least one substituent selected from sulfonic acid and carboxyl groups, and Rc 21 To Rc 28 Each of these groups independently represents a hydrogen atom, a C1 to 4 alkyl group, a C1 to 4 alkoxy group, or a C1 to 4 alkoxy group having a sulfonic acid group. Xc2 represents an amino group that may have at least one substituent S2, a phenylamino group that may have a substituent, a phenylazo group that may have a substituent, a naphthotriazolyl group that may have a substituent, or a benzoylamino group that may have a substituent. Substituent S2 (if there are multiple substituents, each independently) is selected from C1 to 4 alkyl groups, C1 to 4 alkoxy groups, sulfonic acid groups, C1 to 4 alkylamino groups, hydroxyl groups, amino groups, substituted amino groups, carboxyl groups, and carboxyethylamino groups. r, p, and q independently represent 0 or 1, but exclude the case where r, p, and q are all 1. In addition, only either p or q is 1. When Ac2 is a naphthyl group, it does not contain a hydroxyl group as a substituent.

[0110] In the above formula (2), when Ac2 is a phenyl group with a substituent, the phenyl group may include sulfonic acid group, carboxyl group, C1 to 4 alkyl group, C1 to 4 alkoxy group, C1 to 4 alkoxy group with sulfonic acid group, hydroxy group, nitro group, amino group, or substituted amino group (especially acetylamino group or C1 to 4 alkylamino group) as substituent, and it is more preferred to have at least one sulfonic acid group or carboxyl group. When the phenyl group has two or more substituents, it is more preferably that at least one of the substituents is a sulfonic acid group or a carboxyl group, and the other substituents are sulfonic acid group, carboxyl group, C1 to 4 alkyl group, C1 to 4 alkoxy group, C1 to 4 alkoxy group having a sulfonic acid group, hydroxyl group, nitro group, amino group, or substituted amino group (especially acetylamino group or C1 to 4 alkylamino group). Other substituents are more preferably sulfonic acid group, carboxyl group, methyl group, ethyl group, methoxy group, ethoxy group, hydroxyl group, nitro group, or amino group, and particularly preferably sulfonic acid group, carboxyl group, methyl group, methoxy group, or ethoxy group. Furthermore, the C1 to 4 alkoxy group having a sulfonic acid group is more preferably a straight-chain alkoxy group, and the substitution position of the sulfonic acid group is more preferably at the alkoxy terminus. The C1 to 4 alkoxy group having a sulfonic acid group is more preferably 3-sulfonylpropoxy or 4-sulfonylbutoxy, and particularly preferably 3-sulfonylpropoxy. The number of substituents on the phenyl group is preferably 1 or 2. The position of the substituents on the phenyl group is not particularly limited, but it is preferred to use only the 4th position, or a combination of the 2nd and 4th positions, or a combination of the 3rd and 5th positions.

[0111] In formula (2) above, when Ac2 is a naphthyl group with a substituent, the naphthyl group has a substituent selected from sulfonic acid group, hydroxyl group, carboxyl group, or C1 to C4 alkoxy group with a sulfonic acid group, and preferably has at least one sulfonic acid group. When the naphthyl group has two or more substituents, it is more preferred that at least one of the substituents is a sulfonic acid group, and the other substituents are sulfonic acid group, hydroxyl group, carboxyl group, or C1 to C4 alkoxy group with a sulfonic acid group. In addition, the C1 to C4 alkoxy group with a sulfonic acid group is preferably a straight-chain alkoxy group, and the substitution position of the sulfonic acid group is preferably at the end of the alkoxy group. The C1 to C4 alkoxy group with a sulfonic acid group is more preferably 3-sulfonylpropoxy or 4-sulfonylbutoxy, and particularly preferably 3-sulfonylpropoxy. When there are 2 sulfonic acid groups on the naphthyl group, the substitution position of the azo group is taken as the 2-position, and the substitution positions of the sulfonic acid groups are preferably a combination of the 4-position and the 8-position or a combination of the 6-position and the 8-position, with the combination of the 6-position and the 8-position being particularly preferred. When there are 3 sulfonic acid groups on the naphthyl group, the substitution position of the azo group is taken as the 2-position, and the substitution positions of the sulfonic acid groups are particularly preferred a combination of the 1-position, the 3-position and the 6-position, or a combination of the 3-position, the 6-position and the 8-position.

[0112] In formula (2) above, Xc2 represents an amino group having at least one substituent S2, a phenylamino group having at least one substituent, a phenylazo group having at least one substituent, a naphthotriazolyl group having at least one substituent, a benzoyl group having at least one substituent, or a benzoylamino group having at least one substituent. More preferably, examples include: a phenylamino group having a substituent, a phenylazo group having a substituent, a naphthotriazolyl group having a substituent, a benzoyl group having a substituent, or a benzoylamino group having a substituent. Particularly preferred examples of Xc2 include a phenylamino group having a substituent, a phenylazo group having a substituent, and a benzoylamino group having a substituent. The substituents are selected from lower alkyl groups, lower alkoxy groups, sulfonic acid groups, lower alkylamino groups, hydroxyl groups, amino groups, substituted amino groups, carboxyl groups, and carboxyethylamino groups.

[0113] When Xc2 is an amino group that may have at least one substituent S2, the amino group may be unsubstituted, preferably having one or two substituents selected from lower alkyl, lower alkoxy, sulfonic acid, carboxyl, amino, substituted amino, and lower alkylamino groups, and more preferably having one or two substituents selected from methyl, methoxy, sulfonic acid, carboxyl, amino, and lower alkylamino groups.

[0114] When Xc2 is a phenylamino group that may have at least one substituent, the phenylamino group may be unsubstituted, or more preferably has one or two substituents selected from lower alkyl, lower alkoxy, sulfonic acid, amino and lower alkylamino groups, more preferably has one or two substituents selected from methyl, methoxy, sulfonic acid and amino groups.

[0115] When Xc2 is a phenyl azo group that may have at least one substituent, the phenyl azo group is unsubstituted, or more preferably has 1 to 3 substituents selected from hydroxyl, lower alkyl, lower alkoxy, amino and carboxyethylamino, more preferably has 1 to 3 substituents selected from methyl, methoxy, carboxyethylamino, amino and hydroxyl.

[0116] When Xc2 is a naphthotriazole group that may have at least one substituent, the naphthotriazole group is unsubstituted, or more preferably has one or two substituents selected from sulfonic acid groups, amino groups and carboxyl groups, and more preferably has one or two sulfonic acid groups as substituents.

[0117] When Xc2 is a benzoylamine group that may have at least one of the above-mentioned substituents, the benzoylamine group is unsubstituted, or more preferably has one substituent selected from hydroxyl, amino and carboxyethylamine, and more preferably has one or two hydroxyl or amino groups as substituents.

[0118] When Xc2 is a benzoylamine group that may have at least one substituent, the benzoyl group is unsubstituted, or more preferably has one substituent selected from hydroxyl, amino and carboxyethylamino, more preferably has one or two hydroxyl or amino groups as substituents.

[0119] The substitution positions of the substituents that may be present in the aforementioned phenylamino, phenylazo, and benzoylamino groups are not particularly limited, but it is more preferably that one of the substituents is at the p-position relative to the respective amino, azo, or amide group of these possible substituents. When the substitution position of Xc2 is taken as the 1-position with the position of the hydroxyl group of the substituted naphthyl group as the 6-position, the 6-position or 7-position is more preferred, and the 6-position is more preferred.

[0120] In the above formula (2), Rc 21 To Rc 28 Each can be independently represented as a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group containing a sulfonic acid group. Rc 21 To Rc 28 The preferred components are, independently, hydrogen atom, C1 to 4 alkyl group, or C1 to 4 alkoxy group, or straight-chain alkoxy group with sulfonic acid group at the end; the preferred components are hydrogen atom, methyl group, ethyl group, methoxy group, ethoxy group, 3-sulfonic acid propoxy group, or 4-sulfonic acid butoxy group; and the preferred components are hydrogen atom, methyl group, methoxy group, or 3-sulfonic acid propoxy group.

[0121] In the above equation (2), especially through Rc 27 、Rc 28 Each of the preferred elements is a hydrogen atom, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group having a sulfonic acid group, which can achieve high transmittance and high polarization. Hydrogen atoms, C1 to C3 alkyl groups, and C1 to C3 alkoxy groups are more preferred, hydrogen atoms, methyl groups, ethyl groups, methoxy groups, and ethoxy groups are even more preferred, and hydrogen atoms, methyl groups, and methoxy groups are particularly preferred.

[0122] In equation (2) above, r, p, or q are each independently 0 or 1. For good polarization performance in the polarizing element of the present invention, it is preferable that either p or q is 0, and more preferably that either p or q is 1. Furthermore, for even better polarization characteristics, it is preferable that r is 1 and either or both p or q are 0. When r, p, and q are all 1, the content of the substrate (e.g., the dyeability of the polyvinyl alcohol film) may decrease.

[0123] Of the azo compounds shown in formula (2) above, the azo compound shown in formula (2b) below is preferred. By using such an azo compound, the polarization property of the polarizing element can be further improved.

[0124]

[0125] (In equation (2b), Ac2 and Rc) 21 To Rc 28 Xc2, r, p and q respectively represent the same meaning as in equation (2).

[0126] Secondly, specific examples of the azo compounds shown in formula (2) are listed below. Additionally, the following examples of compounds are represented in the form of free acids.

[0127]

[0128]

[0129]

[0130]

[0131]

[0132]

[0133]

[0134]

[0135]

[0136]

[0137]

[0138]

[0139]

[0140]

[0141]

[0142] Examples of free acid compounds in the form of azo compounds shown in formula (2) and formula (2b) include: CI Direct Red 117, CI Direct Red 127, Japanese Patent Application Publication No. 3-12606, Japanese Patent Application Publication No. 8-291259, Japanese Patent Application Publication No. 9-302250, Japanese Patent Application Publication No. 2002-275381, International Patent Application Publication No. 2005 / 075572, International Patent Application Publication No. 2012 / 108169, and International Patent Application Publication No. 2012 / 108173.

[0143] Methods for synthesizing the azo compounds shown in formula (2) and formula (2b) can be listed, for example, in Japanese Patent Application Publication No. 3-12606, Japanese Patent Application Publication No. 8-291259, Japanese Patent Application Publication No. 9-302250, Japanese Patent Application Publication No. 2002-275381, International Publication No. 2005 / 075572, International Publication No. 2012 / 108169, and International Publication No. 2012 / 108173, but are not limited to these.

[0144] Next, the azo compound represented by the following formula (3) will be explained.

[0145]

[0146] In formula (3), Ra1, Ra2, Ab1, and Ab2 are substituted on either ring a or ring b, and either Ra1 or Ra2 is a hydroxyl group, the other representing a hydrogen atom, a hydroxyl group, a C1 to C4 alkoxy group, or a C1 to C4 alkoxy group having a sulfonic acid group. Ab1 and Ab2 are selected from hydrogen atoms, sulfonic acid groups, carboxyl groups, or substituents of amino groups that may have substituents, and either Ab1 or Ab2 represents a sulfonic acid group, a carboxyl group, or an amino group that may have substituents. Rb1 to Rb6 independently represent hydrogen atoms, C1 to C4 alkyl groups, C1 to C4 alkoxy groups, and so on. The sulfonic acid group, a C1 to C4 alkoxy group having a sulfonic acid group, or an amino group that may have a substituent, where h represents 0 or 1, and Xb1 represents an amino group that may have at least one substituent S3, a phenylamino group that may have a substituent, a phenylazo group that may have a substituent, a naphthotriazolyl group that may have a substituent, or a benzoylamino group that may have a substituent, wherein the substituent S3 (if there are multiple substituents, they are each independently selected from the group consisting of C1 to C4 alkyl groups, C1 to C4 alkoxy groups, sulfonic acid groups, amino groups, C1 to C4 alkylamino groups, hydroxyl groups, carboxyl groups, and carboxyethylamino groups that may have a substituent)

[0147] Rb1 to Rb6 may have "substituent amino groups", which are more preferably unsubstituted amino groups or amino groups having one or two substituents (alkyl or acetyl groups of C1 to 4).

[0148] The amino group that may have a substituent S3 is preferably an unsubstituted amino group, or an amino group having one or two C1 to C4 alkyl groups that may have substituents (hydroxyl, methoxy, ethoxy, amino, carboxyl, sulfonic acid, phenyl), more preferably an amino group having one or two hydrogen atoms and a methyl group. The phenylamino group that may have a substituent is preferably a phenylamino group having one or two substituents selected from the group consisting of hydrogen atoms, lower alkyl groups, lower alkoxy groups, sulfonic acid groups, carboxyl groups, amino groups, and lower alkylamino groups, more preferably a phenylamino group having one or two substituents selected from the group consisting of hydrogen atoms, methyl, methoxy, sulfonic acid groups, carboxyl groups, and amino groups. The phenylazo group that may have a substituent is preferably a phenylazo group having one to three phenylazo groups selected from the group consisting of hydrogen atoms, hydroxyl groups, C1 to C4 alkyl groups, C1 to C4 alkoxy groups, amino groups, hydroxyl groups, and carboxyethylamino groups. The benzoylamine group that may have substituents is preferably a benzoylamine group having one substituent selected from the group consisting of hydrogen atom, hydroxyl group, amino group, and carboxyethylamino group. The naphthotriazolyl group that may have substituents is an unsubstituted naphthotriazolyl group, or, more preferably, a naphthotriazolyl group having one or two substituents selected from the group consisting of sulfonic acid group, amino group, and carboxyl group, and more preferably having one or two sulfonic acid groups as substituents.

[0149] The substitution positions of the substituents that may be present in the aforementioned phenylamino, phenylazo, and benzoylamino groups are not particularly limited, but it is more preferred that one of the substituents is at the p-position relative to the amino, azo, or amide group, respectively. When the substitution position of Xb1 is taken as the 1-position of the hydroxyl group of the substituted naphthyl group, the 6-position or 7-position is more preferred, and the 6-position is more preferably preferred.

[0150] When the azo compound shown in formula (3) is the azo compound shown in formula (6), a polarizing element with higher transmittance in the 550 nm to 700 nm range at the parallel position can be provided. More preferably, it is the azo compound shown in formula (7), even more preferably, it is the compound shown in formula (8), even more preferably, it is the compound shown in formula (9), and particularly preferably, it is the azo compound shown in formula (10). Furthermore, in formulas (3), (6) to (10), when Xb1 is an amino group that may have at least one substituent S3, it is more preferably an amino group that may have at least one substituent that is different from the aforementioned Ra1, Ra2, Ab1, and Ab2.

[0151]

[0152] (In the above formula (6), Ra1, Ra2, Ab1, Ab2, Rb1 to Rb6, h, and Xb1 respectively represent the same meaning as in formula (3))

[0153]

[0154] (In equation (7), Ra1, Ra2, Ab1, Ab2, Rb1 to Rb6, h, and Xb1 represent the same meaning as in equation (3).)

[0155]

[0156] (In equation (8), Ra1, Ab1, Rb1 to Rb6, h, and Xb1 respectively represent the same meaning as in equation (3))

[0157]

[0158] (In equation (9), Ra1, Ab1, Rb1 to Rb6, h, and Xb1 respectively represent the same meaning as in equation (3))

[0159]

[0160] (In equation (10), Ab1, Rb1 to Rb6, h, and Xb1 represent the same meaning as in equation (3).)

[0161] The azo compound shown in formula (3) above can be easily manufactured by performing a publicly known diazoification and coupling, according to the usual azo dye manufacturing method described in Non-Patent Document 1. Taking the azo compound shown in formula (6) with h = 0 as an example, the synthesis method is illustrated.

[0162] First, the amine represented by formula (A) is diazidelated using a method disclosed in Non-Patent Document 1, and then coupled once with the aniline of formula (B) to obtain the monoazoamine compound represented by formula (C).

[0163]

[0164] (In equations (A) to (C), Ra1, Ra2, Ab1, Ab2, Rb1, and Rb2 represent the same meanings as Ra1, Ra2, Ab1, Ab2, Rb1, and Rb2 in equation (3).)

[0165] Then, the monoazoamine compound (C) is diazolated using a method disclosed in Non-Patent Document 1 and then coupled a second time with an aniline of formula (D) to obtain the diazoamine compound shown in formula (E).

[0166]

[0167] (In equations (D) and (E), Ra1, Ra2, Ab1, Ab2, Rb1 to Rb4 represent the same meanings as Ra1, Ra2, Ab1, Ab2, Rb1 to Rb in equation (3).)

[0168] Formula (E) is diazidelated using a known method as described in Non-Patent Document 1, and coupled with a naphthol as shown in Formula (F) below, thereby obtaining an azo compound of Formula (3).

[0169]

[0170] (In equation (F), Xb1 represents the same meaning as Xb1 in equation (3))

[0171] In the above reaction, the diazotization step is carried out via either the cis or reverse process. The cis process involves mixing sodium nitrite or other nitrites into an aqueous solution or suspension of the diazo component in an inorganic acid such as hydrochloric acid or sulfuric acid. The reverse process involves pre-adding nitrites to a neutral or weakly alkaline aqueous solution of the diazo component and then mixing this solution with the inorganic acid. The diazotization temperature is preferably between -10 and 40°C. Furthermore, the coupling step for anilines is preferably carried out by mixing acidic aqueous solutions such as hydrochloric acid or acetic acid with the aforementioned diazo solutions, and then conducting the reaction under acidic conditions of pH 2 to 7 at a temperature between -10 and 40°C.

[0172] The monoazo and diazo compounds obtained from coupling can be precipitated directly or by acid precipitation or salting out and then filtered out, or they can be directly used in subsequent steps as solutions or suspensions. If the monoazo or diazo compounds obtained from coupling are poorly soluble and form a suspension, they can also be filtered to form a compressed block for use in subsequent coupling steps.

[0173] The coupling reaction of the diazo compound's diazo derivative with the naphthols shown in formula (F) is carried out under neutral to alkaline conditions ranging from pH 7 to 10 at temperatures from -10 to 40°C. After the reaction, the precipitate is obtained by salting out and then filtered. Alternatively, if purification is necessary, repeated salting out or precipitation from water using an organic solvent can be performed. Examples of water-soluble organic solvents used for purification include alcohols such as methanol and ethanol, and ketones such as acetone.

[0174] The starting materials used to synthesize the azo compound shown in formula (3) correspond to the naphthylamine compound with substituted naphthyl groups shown in formula (A).Preferred 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, 3-amino-1,8-dihydroxy-naphthalene-6-sulfonic acid, 2-amino-18-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-1,8-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-sulfonicopropoxy)-naphthalene-3-sulfonic acid, 2-amino-1-hydroxy-8-(4-sulfonicopropoxy)-naphthalene-3-sulfonic acid Butoxy)-naphthalene-3-sulfonic acid, 2-amino-1-(3-sulfonicopropoxy)-8-hydroxy-naphthalene-3-sulfonic acid, 2-amino-1-(4-sulfonicobutoxy)-8-hydroxy-naphthalene-3-sulfonic acid, 2-amino-1-hydroxy-8-(3-sulfonicopropoxy)-naphthalene-6-sulfonic acid, 2-amino-1-hydroxy-8-(4-sulfonicobutoxy)-naphthalene-6-sulfonic acid, 2-amino-1-(3-sulfonicopropoxy)-8-hydroxy-naphthalene-3,6-disulfonic acid, 2-amino-1-(4-sulfonicobutoxy)-8-hydroxy-naphthalene-3,6-disulfonic acid, 2-amino-1,8-dihydroxy-naphthalene-6-aminomethyl-3-disulfonic acid, etc.; more preferably, 2-amino-1,8-di-naphthalene-3,6-disulfonic acid, etc. Hydroxy-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-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-sulfonylpropoxy)-naphthalene-3-sulfonic acid, 2-amino-1-(3-sulfonylpropoxy)-8-hydroxy-naphthalene-3,6-disulfonic acid, but not limited to these.

[0175] Aniline derivatives having substituents (Rb1 to Rb6) belonging to the first or second coupling components when h is 0, or the first to third 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 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 4-(3-amino-4-methylphenoxy)butane-1-sulfonic acid, 4-(3-amino-4-methylphenoxy)butane-1-sulfonic acid, 2-(3-amino-4-methylphenoxy)ethane-1-sulfonic acid, 2-(3-amino-4-methylphenoxy)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)propane-1-sulfonic acid, 4-(3-amino-4-methyl ... Aromatic amines include, but are not limited to, ω-(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, 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. These aromatic amines may have protected amino groups. Examples of protecting groups include, for instance, ω-methane sulfone groups.

[0176] Examples of naphthols of type Xb1 that have a 3-coupling component when h is 0 or a 4-coupling component when h is 1 include, but are not limited to, 6-amino-3-sulfonic-1-naphthol, 6-methylamino-3-sulfonic-1-naphthol, 6-phenylamino-3-sulfonic-1-naphthol, 6-(4-methoxy-phenylamino)-3-sulfonic-1-naphthol, 6-benzoylamino-3-sulfonic-1-naphthol, and 6-(4'-aminobenzoyl)amino-3-sulfonic-1-naphthol.

[0177] Specific examples of azo compounds represented by formula (3) are listed below. Furthermore, azo compounds are represented in the form of free acids.

[0178]

[0179]

[0180]

[0181]

[0182]

[0183]

[0184]

[0185]

[0186] The polarizing element of the present invention can provide a polarizing element or polarizing plate with higher transmittance and higher polarization degree compared to well-known dye-based polarizing plates by combining the azo compound shown in formula (1) or formula (2) and formula (3) above. In addition, it can have higher transmittance and higher polarization degree than well-known polarizing plates, and achieve a high-quality paper white when displaying white, commonly known as paper white, and achieve a colorless black when displaying black, especially a clear black with a high-end feel. Furthermore, it can have higher contrast than conventional dye-based polarizing elements or dye-based polarizing plates.

[0187] The polarizing element of the present invention comprises an azo compound of formula (1), formula (2), and formula (3), and further comprises an azo compound of formula (4) or formula (5), thereby obtaining a polarizing element with higher transmittance and higher polarization. In particular, by comprising an azo compound of formula (4) or formula (5) or a salt thereof, the transmittance of the polarizing element in the 400 to 500 nm range can be further improved, and high polarization can be obtained, which is therefore preferred.

[0188] The following describes the azo compound represented by formula (4).

[0189]

[0190] (In the above formula (4), Ay) 11 Each of the following groups is independently a hydrogen atom, a sulfonic acid group, a carboxyl group, a hydroxyl group, a lower alkyl group, or a lower alkoxy group; Ry 11 To Ry 14 Each of the following is independently represented by a hydrogen atom, a sulfonic acid group, a lower alkyl group, a lower alkoxy group, or a lower alkoxy group containing a sulfonic acid group, where f represents an integer from 1 to 3.

[0191] In equation (4) above, Ay 11 Preferably, a sulfonic acid group or a carboxyl group is used. Ry 11 To Ry 14 The preferred components are hydrogen atoms, sulfonic acid groups, lower alkyl groups, and lower alkoxy groups; more preferably, hydrogen atoms, methyl groups, and methoxy groups.

[0192] Specific examples of the azo compounds shown in formula (4) include: CI Direct Yellow 4, CI Direct Yellow 12, CI Direct Yellow 72, and CI Direct Orange 39, as well as the azo compounds with a stilbene structure described in International Publication No. 2007 / 138980, but are not limited to these.

[0193] The azo compound or its salt shown in formula (4) can be synthesized, for example, by the methods described in International Publication No. 2007 / 138980, etc.

[0194] Further specific examples of the azo compounds represented by formula (4) are given below. Furthermore, the compound examples are represented in the form of free acids.

[0195]

[0196] Secondly, the azo compound shown in formula (5) is explained.

[0197]

[0198] (In equation (5), Ay) 21 and Ay 22 Ry can be independently a naphthyl group that may have substituents or a phenyl group that may have substituents. 21 Ry 22 Ry 27 Ry 28 Ry is independently composed of a hydrogen atom, a C1 to 4 alkyl group, and a C1 to 4 alkoxy group. 23 To Ry 26Each of the following is independently represented by a hydrogen atom, a C1 to C4 alkyl group, a C1 to C4 alkoxy group, or a C1 to C4 alkoxy group with a sulfonic acid group, and s and t independently represent 0 or 1 respectively.

[0199] The phenyl group having a substituent is preferably a phenyl group having one or more substituents selected from sulfonic acid group, carboxyl group, lower alkoxy group having sulfonic acid group, lower alkyl group, lower alkoxy group, halogen group, nitro group, amino group, lower alkyl substituted amino group, and lower alkyl substituted acylamino phenyl group. When a phenyl group has two or more substituents, at least one of the substituents is a sulfonic acid group, a carboxyl group, or a lower alkoxy group having a sulfonic acid group. Other substituents are preferably a sulfonic acid group, a hydrogen atom, a lower alkyl group, a lower alkoxy group, a lower alkoxy group having a sulfonic acid group, a carboxyl 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, they are a sulfonic acid group, a hydrogen atom, a methyl group, an ethyl group, a methoxy group, an ethoxy group, a carboxyl group, a sulfoethoxy group, a sulfopropoxy group, a sulfobutoxy group, a chloro group, a nitro group, or an amino group. Particularly preferred are a sulfonic acid group, a carboxyl group, a hydrogen atom, a methyl group, a methoxy group, a sulfoethoxy group, a sulfopropoxy group, or a sulfobutoxy group. The substitution positions are not particularly limited, but are preferably only at the 2-position, only at the 4-position, a combination of the 2-position and 6-position, a combination of the 2-position and 4-position, or a combination of the 3-position and 5-position. Particularly preferred are only at the 2-position, only at the 4-position, a combination of the 2-position and 4-position, or a combination of the 3-position and 5-position. Furthermore, "only 2-position" and "only 4-position" indicate that there is a substituent other than a hydrogen atom only at the 2-position or 4-position.

[0200] The phenyl group having substituents is preferably as shown in the following formula (11).

[0201]

[0202] In equation (11), Ry 2a and Ry 2b At least one of them is a sulfonic acid group, a carboxyl group, or a lower alkoxy group having a sulfonic acid group, and the other is a hydrogen atom, a sulfonic acid group, a carboxyl group, a lower alkoxy group having a sulfonic acid 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 acyl amino group. Ry is more preferred. 2a and Ry 2b One of them is a sulfonic acid group or a carboxyl group, and the other is a hydrogen atom, a sulfonic acid group, a carboxyl group, a methyl group, or a methoxy group.

[0203] The naphthyl group that may have substituents is preferably selected from one or more naphthyl groups that may have substituents, including hydroxyl, lower alkoxy groups having sulfonic acid groups, and sulfonic acid groups.

[0204] The naphthyl group that may have substituents is preferably the naphthyl group shown in the following formula (12).

[0205]

[0206] In equation (12), Ry 2c It is a hydrogen atom, a hydroxyl group, a lower alkoxy group having a sulfonic acid group, or a sulfonic acid group. u is an integer from 1 to 3. The sulfonic acid group can be located in the benzene ring of any of the naphthalene rings. Ry is more preferred. 2c The hydrogen atom is u = 2. The lower alkoxy group having a sulfonic acid group is preferably a straight-chain alkoxy group, and the substitution position of the sulfonic acid group is preferably at the alkoxy terminus. The lower alkoxy group having a sulfonic acid group is more preferably 3-sulfonopropoxy and 4-sulfonobutoxy. The position of the substituents on the naphthyl group is not particularly limited. If the numbering is as shown in formula (12), the substitution position of the azo group in formula (5) is set to position 2. When there are two substituents, combinations of positions 5 and 7, 4 and 8, or 6 and 8 are preferred. When there are three substituents, combinations of positions 3 and 5 and 7, or 3 and 6 and 8 are preferred.

[0207] Ry 21 Ry 22 Ry 27 Ry 28 Each of the following can be independently a hydrogen atom, a lower alkoxy group, or a lower alkyl group, but is preferably a hydrogen atom, methyl, ethyl, methoxy, or ethoxy group.

[0208] Ry 23 To Ry 26 Each is independently a hydrogen atom, a lower alkyl group, a lower alkoxy group, and a lower alkoxy group with a sulfonic acid group, but Ry 23 To Ry 26 The substituents are preferably hydrogen atoms, methyl, ethyl, methoxy, ethoxy, 3-sulfonylpropoxy, or 4-sulfonylbutoxy, and more preferably hydrogen atoms, methyl, ethyl, methoxy, or 3-sulfonylpropoxy. The positions of Ry3 to Ry6 are preferably only at position 2, only at position 5, a combination of positions 2 and 6, a combination of positions 2 and 5, or a combination of positions 3 and 5, and more preferably only at position 2, only at position 5, or a combination of positions 2 and 5. Furthermore, "only at position 2" and "only at position 5" indicate that there is a substituent other than a hydrogen atom only at position 2 or 5.

[0209] The azo compound shown in formula (5) is more preferably the azo compound shown in formula (5b) below.

[0210]

[0211] (In equation (5b), Ay) 21 Ay 22 Ry 21 To Ry 28 , s or t respectively represent Ay in equation (5) 21 Ay 22 Ry 21To Ry 28 (s or t have the same meaning)

[0212] The azo compound shown in formula (5) or the azo compound shown in formula (5b) or its salts are diazidolated and coupled according to the usual azo dye manufacturing method as described in Non-Patent Document 1, and can be manufactured by reacting with ureating agents as described in Patent Documents 4 to 7.

[0213] Secondly, specific examples of azo compounds represented by formula (5) or formula (5b) are given below. Furthermore, the sulfonic acid group, carboxyl group, and hydroxyl group in the formula are represented in the form of free acids.

[0214]

[0215]

[0216]

[0217]

[0218]

[0219]

[0220]

[0221]

[0222]

[0223]

[0224]

[0225]

[0226]

[0227]

[0228]

[0229]

[0230] The azo compounds shown in formulas (1) to (5) above can be in the form of free acid, salt, or salt of metal ions or ammonium ions. Examples of metal ions include: alkali metal ions such as lithium ions, sodium ions, and potassium ions; and alkaline earth metal ions such as calcium ions and magnesium ions. Examples of ammonium ions include: ammonium ions, methylammonium ions, dimethylammonium ions, triethylammonium ions, tetraethylammonium ions, tetra-n-propylammonium ions, tetra-n-butylammonium ions, triethanolamine ions, etc. More specifically, for example, free acid represents sulfonic acid (-SO3H), sodium ion represents sodium sulfonate (-SO3Na), and ammonium ion represents ammonium sulfonate (-SO3NH4).

[0231] The polarizing element of the present invention comprises an azo compound of formula (1), formula (2), and formula (3). It can provide a polarizing element with high transmittance and high contrast, i.e., high polarization. Furthermore, by arbitrarily further comprising an azo compound of formula (4) or formula (5), an even higher transmittance and high contrast, i.e., high polarization, can be provided.

[0232] The polarizing element of the present invention possesses excellent polarization performance, including chromaticity a* and b* values ​​within a preferred range (described later), individual transmittance after visual sensitivity correction, and average transmittance in a specific wavelength band. For example, the transmittance can be constant in each wavelength of each individual polarizing element. Furthermore, in each wavelength at the parallel position when the absorption axes of the two polarizing elements are parallel, the transmittance can also be constant, that is, it has an achromatic hue. Next, in each wavelength at the orthogonal position when the absorption axes of the two polarizing elements are orthogonal, the transmittance can also be constant, that is, it has an achromatic hue. As a result, the polarizing element of the present invention not only has high transmittance and high contrast (i.e., high polarization), but also possesses an achromatic hue.

[0233] By changing the content of each of the aforementioned azo compounds in the substrate of the polarizing element of the present invention, the transmittance and chromaticity can be adjusted to fall within the preferred range described later. The performance of the polarizing element is affected not only by the ratio of each azo compound in the polarizing element, but also by various factors such as the swelling or elongation of the substrate adsorbing the azo compounds, dyeing time, dyeing temperature, pH during dyeing, and the influence of salt. Therefore, the ratio of each azo compound can be determined according to the swelling of the substrate, the temperature, time, pH, type of salt, salt concentration, and further according to the elongation.

[0234] (Transmittance after visual perception correction)

[0235] The aforementioned transmittance after visual sensitivity correction refers to transmittance corrected to human visual sensitivity, which can be obtained according to JIS Z 8722:2009. For the test sample (e.g., polarizing element or polarizing plate), the spectral transmittance at each wavelength in the wavelength range of 380 to 780 nm can be measured every 5 nm or 10 nm using a C light source (2 degrees field of view), and then corrected to visual sensitivity according to JIS Z 8722:2009. The transmittance after visual sensitivity correction includes: the transmittance of a single test sample after visual sensitivity correction (Ys) when measuring the test sample individually; the transmittance of the parallel position after visual sensitivity correction when using two test samples with their respective absorption axes set to parallel (Yp); and the transmittance of the orthogonal position after visual sensitivity correction when using two test samples with their respective absorption axes set to orthogonal (Yc).

[0236] (The difference in average transmittance across two wavelength bands)

[0237] The polarizing element of the present invention is preferably such that the difference in average transmittance between specific wavelength bands is below a predetermined value. Average transmittance refers to the average transmittance of each wavelength within a specific wavelength band.

[0238] The wavelength bands of 420nm to 480nm, 520nm to 590nm, and 600nm to 640nm are the main wavelength bands used in the calculation of color matching functions in JIS Z 8781-4:2013 when displaying colors. Specifically, in the XYZ color matching function of JIS Z 8701, which forms the basis of JIS Z 8781-4:2013, when the maximum values ​​of x(λ) with 600nm as the maximum value, y(λ) with 550nm as the maximum value, and z(λ) with 455nm as the maximum value are each set to 100, the wavelength bands displaying values ​​of 20 or higher are the wavelength bands of 420nm to 480nm, 520nm to 590nm, and 600nm to 640nm. Hereinafter, the average transmittance of each wavelength from ○nm to △nm is also referred to as "AT". ○-△ ".

[0239] (Parallel bit penetration rate)

[0240] When two polarizing elements are stacked and arranged with their absorption axes parallel (for bright or white display), the transmittance measured at each wavelength is also called the "parallel position transmittance (Tp)" for each wavelength. For the parallel position transmittance of the polarizing element of this invention at each wavelength, the difference in average transmittance between the two wavelength bands is AT. 420-480 With AT 520-590The absolute value of the difference 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. Additionally, AT 520-590 With AT 600-640 The absolute value of the difference 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 the whiteness of high-quality paper in a parallel position.

[0241] (Orthogonal penetration rate)

[0242] When two polarizing elements are overlapped in a configuration where their absorption axes are orthogonal (in black display or dark display), the transmittance measured at each wavelength is called the "cross-polarity transmittance (Tc)" for each wavelength. For the cross-polarity transmittance of the polarizing element of this invention at each wavelength, the difference in average transmittance between the two wavelength bands is AT. 420-480 With AT 520-590 The absolute value of the difference is preferably less than 1.0%, and AT 520-590 With AT 600-640 The absolute value of the difference is preferably below 1.0%. Such a polarizing element can display a colorless black at orthogonal positions. Additionally, AT... 420-480 With AT 520-590 The absolute value of the difference is preferably 0.6% or less, more preferably 0.3% or less, and even more preferably 0.1% or less. Additionally, AT 520-590 With AT 600-640 The absolute value of the difference is preferably 1.0% or less, more preferably 0.6% or less, even more preferably 0.3% or less, and particularly preferably 0.1%.

[0243] Furthermore, for the average transmittance of individual units, parallel position transmittance, and quadrature position transmittance at wavelengths different from the aforementioned wavelength bands (380nm to 420nm, 480nm to 520nm, and 640nm to 780nm), it is preferable to adjust the average transmittance to some extent. For the individual unit transmittance of the polarizing element of the present invention at each wavelength, the difference in average transmittance between the two wavelength bands is preferably AT. 380-420 With AT 420-480 The difference is less than 15%, and AT is preferred. 480-520 With AT 420-480 The difference is less than 15%, and AT is preferred. 480-520 With AT 520-590 The difference is less than 15%, and AT is preferred. 640-780 With AT 600-640 The difference is less than 20%.

[0244] (Value of single-cell transmittance after visual perception correction)

[0245] The polarizing element of the present invention preferably has a transmittance (Ys) of 35% to 65% after visual sensitivity correction. The transmittance after visual sensitivity correction is the transmittance of a test sample (e.g., a polarizing element or polarizing plate) corrected to visual sensitivity according to JIS Z 8722:2009. Regarding the performance of the polarizing plate, as long as the transmittance of the polarizing element after visual sensitivity correction is 35% to 65%, a brightness that does not appear unnatural can be achieved even when used in a display device. Higher transmittance tends to decrease polarization; therefore, from the viewpoint of balancing polarization, the transmittance of the polarizing element after visual sensitivity 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 transmittance of the polarizing element after visual sensitivity correction exceeds 65%, there is a decrease in polarization; however, when a bright transmittance of the polarizing element or specific polarization performance and contrast are required, the transmittance of the polarizing element after visual sensitivity correction can exceed 65%.

[0246] (Average transmittance in a specific wavelength band)

[0247] For the average transmittance of parallel position (Tp) at each wavelength, the polarizing element of the present invention is preferably AT. 520-590 The transmittance is 25% to 50%. When such a polarizing element is installed in a display device, it can be configured as a bright and clear display. The transmittance of the 520nm to 590nm wavelength band is one of the main wavelength bands used in the calculation of color isochromatic functions when displaying colors, as specified in JIS Z 8781-4:2013. In particular, each wavelength band from 520nm to 590nm is the wavelength band with the highest visual sensitivity according to the colorochromatic function, and the transmittance in this range is close to the transmittance that can be visually confirmed. Therefore, it is very important to adjust the transmittance of the 520nm to 590nm wavelength band. The average transmittance AT of the parallel position transmittance of each wavelength... 520-590 More preferably, the polarization is 28% to 45%, and even more preferably, 30% to 40%. Furthermore, the polarization degree of the polarizing element is preferably 80% to 100%, more preferably 90% to 100%, even more preferably 97% to 100%, and still more preferably 99% or more, particularly preferably 99.5% or more. Higher polarization degree is preferred, but in the relationship between polarization degree and transmittance, a suitable transmittance and polarization degree can be adjusted by emphasizing brightness or polarization degree (or contrast).

[0248] (Color a* and b* values)

[0249] The chromaticity a* and b* values ​​are obtained when measuring the transmittance of natural light according to JIS Z 8781-4:2013. The method for displaying the color of objects as defined in JIS Z 8781-4:2013 is equivalent to the method for displaying the color of objects as defined by the International Commission on Illumination (CIE). The chromaticity a* and b* values ​​are determined by irradiating the test sample (e.g., a polarizing element or polarizing plate) with natural light. Furthermore, in the following description, the colorimetric a* and b* values ​​obtained for one test sample are denoted as a*-s and b*-s, the colorimetric a* and b* values ​​obtained for two test samples arranged with their absorption axes parallel to each other (when displayed in white) are denoted as a*-p and b*-p, and the colorimetric a* and b* values ​​obtained for two test samples arranged with their absorption axes orthogonal to each other (when displayed in black) are denoted as a*-c and b*-c.

[0250] In the polarizing element of the present invention, it is preferable that the absolute values ​​of chromaticity a*-s and b*-s obtained for a single test sample are 1.0 or less (-1.0 ≤ a*-s ≤ 1.0, -1.0 ≤ b*-s ≤ 1.0). Furthermore, it is preferable that a*-p is -2.0 to 2.0 (-2.0 ≤ a*-p ≤ 2.0), and b*-p is -2.0 to 3.0 (-2.0 ≤ b*-p ≤ 3.0). Such a polarizing element is a single unit and has a neutral color, and can display a high-quality white when displaying white. More preferably, in a state where two test samples are arranged with their absorption axes parallel to each other (when displaying white), the absolute values ​​of a*-p and b*-p are each independently 2.0 or less, more preferably 1.5 or less, and particularly preferably 1.0 or less. Furthermore, when the two test samples are arranged with their absorption axes orthogonal (for 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 a colorless black when displaying black. Even if the absolute values ​​of chromaticity a* and b* differ by only 0.5, humans can perceive the color difference, and there are cases where the color difference is fully perceived by the individual. Therefore, controlling these values ​​is very important in polarizing elements. In particular, when the absolute values ​​of a*-p, b*-p, a*-c, and b*-c are all 1.0 or less, a good polarizing plate with virtually no other colors can be obtained in both white display (for white display) and black display (for black display). Achromaticity, such as the white of high-quality paper, can be achieved at parallel positions, and a clear, sophisticated black with achromatic feel can be achieved at cross positions. However, the influence of hue on the black of a display device is not limited to this; even in a dark state, hue can be perceived as darkness. Therefore, when the polarization is high, that is, when the cross-position transmittance is low, black can be imparted even if the absolute values ​​of the polarizing elements a*-c and b*-c are not less than 2.0. The applicant's research results show that when the cross-position transmittance is less than 1% or the polarization is about 97% or more in the wavelength bands of 420nm to 480nm, 520nm to 590nm, and 600nm to 640nm, visual black can be imparted regardless of the absolute values ​​of chromaticity a*-c and b*-c. When the cross-transmittance of each wavelength in the wavelength range of 420nm to 480nm, 520nm to 590nm, and 600nm to 640nm is less than 0.6% or more, or the polarization is greater than 98%, it is more preferable because it can give a better visual blackness. It is especially preferable when the cross-transmittance of each wavelength is less than 0.3% or more, or the polarization is greater than 99%.

[0251] Based on the above results, in the state where the two polarizing elements are overlapped in a manner where the absorption axes are orthogonal (when displaying black, or, when displaying dark), in order to give it a colorless black hue, it is more preferable to satisfy any of the following conditions 1) to 3).

[0252] 1) For the orthogonal transmittance (Tc) of each wavelength, AT 420-480 With AT 520-590 The absolute value of the difference is less than 1.0%, and AT 520-590 With AT 600-640 Cases where the absolute value of the difference is less than 1.0%.

[0253] 2) When the absolute values ​​of chromaticity a*-c and b*-c are both below 2.0

[0254] 3) The cross-spot transmittance (Tc) of each wavelength in the wavelength bands of 420nm to 480nm, 520nm to 590nm, and 600nm to 640nm is less than 1% or the polarization is more than approximately 97%.

[0255] The polarizing element of this invention features high contrast and high transmittance, as well as the achromaticity of a single element and high polarization. Furthermore, when displaying white, the polarizing element of this invention can reproduce a high-quality paper-like white (paper white), and when displaying black, it can reproduce an achromatic black, especially a clear black with a sophisticated feel. In addition, the polarizing element of this invention exhibits high durability, particularly against high temperatures and high humidity.

[0256] Compared to iodine-based polarizing plates or the polarizing element described in Patent Document 3, the polarizing element of the present invention absorbs less light with wavelengths above 700 nm, thus having the advantage of minimal heat generation even when exposed to sunlight. For example, when using a liquid crystal display outdoors, the display is exposed to sunlight, and consequently, the polarizing element is also exposed. Sunlight also contains light with wavelengths above 700 nm, and light in the near-infrared region has a heating effect. The polarizing element of the present invention absorbs very little near-infrared radiation, therefore, even when exposed to sunlight outdoors, it generates very little heat, which is excellent in terms of minimal degradation.

[0257] <Method for fabricating polarizing elements>

[0258] The following describes a specific method for manufacturing a polarizing element, using the example of adsorbing azo compounds onto a polyvinyl alcohol-based resin substrate. However, the method for manufacturing the polarizing element of the present invention is not limited to the methods described below.

[0259] (Preparation of the embryonic membrane)

[0260] The preform film can be made by manufacturing a polyvinyl alcohol (PVA) resin film. There are no particular limitations on the PVA resin; commercially available PVA resins or those synthesized by known methods can be used. For example, a PVA resin can be obtained by saponifying a polyvinyl acetate (PVC) resin. Besides PVC, which is a homopolymer of PVC, examples of PVC resins include PVC and copolymers of other monomers that can copolymerize with PVC. Other monomers that can copolymerize with PVC include, for example, unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids. A saponification degree of approximately 85 to 100 mol% is generally preferred for the PVA resin, and more preferably 95 mol% or higher. The PVA resin can be further modified; for example, aldehyde-modified polyvinylformaldehyde or polyvinyl acetal can be used. In addition, the degree of polymerization of polyvinyl alcohol resin refers to the viscosity-average degree of polymerization, which can be obtained by well-known methods in the art. It is usually preferred to be around 1,000 to 10,000, and more preferably around 1,500 to 6,000.

[0261] The method for manufacturing the above-mentioned polyvinyl alcohol-based resin film is not particularly limited, and known methods can be used to prepare the film. In this case, the polyvinyl alcohol-based resin film may contain glycerol, ethylene glycol, propylene glycol, low molecular weight polyethylene glycol, etc., as plasticizers. The amount of plasticizer in the total film weight is preferably 5 to 20% by mass, more preferably 8 to 15% by mass. The film thickness is not particularly limited, but for example, about 5 μm to 150 μm is preferred, and about 10 μm to 100 μm is more preferred.

[0262] (Swelling step)

[0263] The resulting embryonic membrane is subjected to a swelling treatment. The swelling treatment is preferably performed by immersing the embryonic membrane in a solution at 20 to 50°C for 30 seconds to 10 minutes. Water is the preferred solution. The elongation ratio is preferably adjusted to 1.00 to 1.50 times, more preferably to 1.10 to 1.35 times. When shortening the manufacturing time of the polarizing element, the embryonic membrane will also swell during the dyeing process described later, so the swelling treatment can be omitted.

[0264] (Staining steps)

[0265] In the dyeing step, the resin film obtained by swelling the embryo membrane is adsorbed and impregnated with azo compounds. If the swelling step is omitted, the embryo membrane swelling treatment can be performed simultaneously in the dyeing step. The adsorption and impregnation with azo compounds are steps for coloring the resin film, hence they are designated as the dyeing step.

[0266] The azo compound used in the dyeing step is the azo compound shown in formula (1) or the azo compound shown in formula (2), or a mixture of the azo compound shown in formula (3). The azo compound shown in formula (4) or the azo compound shown in formula (5) may also be used. Furthermore, without compromising the performance of the polarizing element of the present invention, azo compounds belonging to dichroic dyes, as illustrated in Non-Patent Document 2, may be used. These azo compounds may be used not only in the form of free acids, but also as salts of the compounds. Examples of such salts include alkali metal salts such as lithium, sodium, and potassium salts; or organic salts such as ammonium or alkylamine salts, with sodium salts being more preferred.

[0267] The dyeing step can be any method of adsorbing and impregnating pigments onto a resin membrane, and is not particularly limited. For example, it is more preferably carried out by impregnating the resin membrane in a dyeing solution, or by coating the resin membrane with the dyeing solution. The azo compounds in the dyeing solution can be adjusted, for example, in the range of 0.001 to 10% by mass.

[0268] 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 immersion time in the solution can be adjusted appropriately, but it is preferably adjusted to 30 seconds to 20 minutes, and more preferably 1 to 10 minutes.

[0269] In addition to azo compounds, the dyeing solution may contain dyeing auxiliaries as needed. Examples of dyeing auxiliaries include sodium carbonate, sodium bicarbonate, sodium chloride, sodium sulfate, anhydrous sodium sulfate, and sodium tripolyphosphate. The content of dyeing auxiliaries can be adjusted at any concentration depending on the dyeing time and temperature, with a preferred content of 0.001 to 5% by mass in the dyeing solution, and a more preferred content of 0.01 to 2% by mass.

[0270] (Washing Step 1)

[0271] A washing step (hereinafter also referred to as "washing step 1") may be performed after the dyeing step and before proceeding to subsequent steps. Washing step 1 is a step of washing away the dyeing solution that adhered to the surface of the resin film during the dyeing step. By performing washing step 1, dye migration in the solution for subsequent treatment can be inhibited. In washing step 1, water is generally used as the washing solution. The washing method is preferably immersion in the washing solution, but washing can also be performed by coating the resin film with the washing solution. The washing time is not particularly limited, but it is preferably 1 to 300 seconds, more preferably 1 to 60 seconds. The temperature of the washing solution in washing step 1 must be such that it does not dissolve the material constituting the resin film (e.g., a hydrophilic polymer, in this case, a polyvinyl alcohol-based resin). Generally, the washing treatment is performed at 5 to 40°C. However, even without washing step 1, the performance will not be affected, so the washing step can be omitted.

[0272] (Steps involving crosslinking agents and / or water-resistant agents)

[0273] Following the dyeing or washing step 1, a step containing a crosslinking agent and / or a water-resistant agent may be performed. The method of containing the crosslinking agent and / or water-resistant agent in the resin film is preferably by immersion in a treatment solution, but the treatment solution may also be coated or applied to 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.

[0274] Crosslinking agents can be, for example, boron compounds such as boric acid, borax, or ammonium borate; polyaldehydes such as glyoxal or glutaraldehyde; polyvalent isocyanate compounds such as urea-type, triisocyanate-type, or block-type; titanium compounds such as titanium oxysulfate, etc., but others such as ethylene glycol glycidyl ether and polyamide epichlorohydrin can also be used. Examples of hydration-resistant agents include: peroxysuccinic acid, ammonium persulfate, calcium perchlorate, benzoin ethyl ether, ethylene glycol diglycidyl ether, glycerol diglycidyl ether, ammonium chloride, or magnesium chloride, etc., with boric acid being preferred. Water is preferred as the solvent for the crosslinking agent and / or hydration-resistant agent, but is not limited thereto. The concentration of the crosslinking agent and / or hydration-resistant agent can be appropriately determined by those skilled in the art according to its type, but when boric acid is used as an example, a concentration of 0.1 to 6.0% by mass in the treatment solution is preferred, and 1.0 to 4.0% by mass is more preferred. However, this treatment step can be omitted in cases where crosslinking agents and / or water-resistant agents are not required and the time is to be shortened, or in cases where crosslinking or water-resistant treatment is not required.

[0275] (Extended steps)

[0276] After the dyeing step, washing step 1, or step containing a crosslinking agent and / or a water-resistant agent, a stretching step is performed. The stretching step is carried out by stretching the resin film uniaxially. The stretching method can be either wet stretching or dry stretching. A stretch ratio of 3 times or more is preferred, more preferably 4 to 8 times, and particularly preferably 5 to 7 times.

[0277] In the case of wet stretching, it is preferable to stretch the resin film in water, a water-soluble organic solvent, or a mixture thereof. It is also preferable to stretch while immersing the film in a solution containing at least one crosslinking agent and / or a water-resistant agent. The same crosslinking agent and water-resistant agent as described above can be used in the step containing the crosslinking agent and / or water-resistant agent. The concentration of the crosslinking agent and / or water-resistant agent in the solution of the stretching step is preferably, for example, 0.5 to 15% by mass, and more preferably 2.0 to 8.0% by mass. The stretching temperature is preferably 40 to 60°C, and more preferably 45 to 58°C. The stretching time is typically 30 seconds to 20 minutes, but more preferably 2 to 5 minutes. The wet stretching step can be performed in one stage or in multiple stages (two or more stages).

[0278] In the case of dry stretching, when the stretching heating medium is air, it is preferable to stretch the resin film at a temperature of room temperature to 180°C. Furthermore, it is preferable to stretch in an environment with a humidity of 20% to 95% RH. Examples of heating methods include, but are not limited to, inter-roll stretching, roll heating stretching, calendering stretching, and infrared heating stretching. The stretching process can be performed in one stage or in multiple stages (two or more stages).

[0279] (Washing step 2)

[0280] After the extension step, crosslinking agents and / or water-resistant agents may precipitate or foreign matter may adhere to the surface of the resin membrane. Therefore, a washing step (hereinafter also referred to as "washing step 2") can be performed to clean the surface of the resin membrane. The washing time is preferably from 1 second to 5 minutes. The washing method is preferably to immerse the resin membrane in the washing solution, but washing can also be performed by coating or applying the solution to the resin membrane. Water is the preferred washing solution. The washing process can be performed in one stage or in multiple stages (two or more stages). The solution temperature for the washing step is not particularly limited, but it is usually from 5 to 50°C, preferably from 10 to 40°C.

[0281] In addition to water, the processing solutions or solvents used in current treatment steps may include, but are not limited to, alcohols such as dimethyl sulfone, N-methylpyrrolidone, methanol, ethanol, propanol, isopropanol, glycerol, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, or trimethylolpropane; and amines such as ethylenediamine and diethylenetriamine. Water is the most preferred processing solution or solvent. Furthermore, one of these processing solutions or solvents may be used alone, or a mixture of two or more may be used.

[0282] (Drying step)

[0283] Following the extension step or washing step 2, a drying step of the resin film is performed. Drying can be carried out naturally, but to improve drying efficiency, it can be performed by compression with rollers, removal of surface moisture using air knives, or water-absorbing rollers, and / or by air-assisted drying. The drying temperature is preferably between 20 and 100°C, more preferably between 60 and 100°C. The drying time is typically between 30 seconds and 20 minutes, preferably between 5 and 10 minutes.

[0284] In the method for manufacturing a polarizing element, the swelling degree of the substrate in the swelling step, the mixing ratio of each azo compound in the dyeing step, the temperature and pH of the dyeing solution, the type or concentration of salts such as sodium chloride or sodium sulfate, sodium tripolyphosphate, and the dyeing time, as well as the stretching ratio in the stretching step, are preferably adjusted in a manner that makes the polarizing element of the present invention satisfy at least one of the following conditions (i) to (vi), and more preferably adjusted in a manner that better satisfies conditions (vii) and (viii).

[0285] (i) Regarding parallel-position transmittance (Tp), AT 420-480 With AT 520-590 The absolute value of the difference is less than 2.5, AT 520-590 With AT 600-640 The absolute value of the difference is 3.0.

[0286] (ii) Regarding the orthogonal transmittance (Tc), AT 420-480 With AT 520-590 The absolute value of the difference is less than 1.0, AT 520-590 With AT 600-640 The absolute value of the difference is less than 1.0.

[0287] (iii) The per-unit transmittance (Ys) after visual sensitivity correction is 35% to 65%.

[0288] (iv) The absolute values ​​of the chromaticity a* and b* values ​​of the polarizing element are both below 1.0.

[0289] (v) In the parallel position, the chromaticity a* value is between -2.0 and 2.0, and the b* value is between -2.0 and 3.0.

[0290] (vi) The absolute values ​​of the chromaticity a* and b* values ​​at the orthogonal positions are both less than 2.

[0291] (vii) For parallel bit transmittance (Tp), AT 520-590 It ranges from 25% to 35%.

[0292] (viii) In either monomeric transmittance (Ts) or orthorhombic transmittance (Tc), AT 380-420With AT 420-480 The difference is less than 15%, AT 480-520 With AT 420-480 The difference is less than 15%, AT 480-520 With AT 520-590 The difference is less than 15%, and / or AT 640-780 With AT 600-640 The difference is less than 20%.

[0293] A polarizing element comprising the azo compound shown in formula (1) or the azo compound shown in formula (2), and a combination of the azo compounds shown in formula (3), or any combination of the azo compound shown in formula (4) or the azo compound shown in formula (5), can be manufactured by the above method.

[0294] <Polarizing plate>

[0295] The polarizing plate of the present invention includes a polarizing element and a transparent protective layer disposed on one or both sides of the polarizing element. The transparent protective layer is provided for purposes such as improving the water resistance or operability of the polarizing element.

[0296] The aforementioned transparent protective layer is a protective film formed using a transparent material. The protective film is a layered film capable of maintaining the shape of the polarizing element, and is preferably made of a plastic with excellent transparency, mechanical strength, thermal stability, and moisture-blocking properties. The same function can be achieved by forming an equivalent layer. Examples of plastics constituting the protective film include thermoplastic resins such as polyester resins, acetate resins, polyethersulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, and acrylic resins; and films obtained from thermosetting or UV-curing resins such as acrylic, ethyl carbamate, ethyl carbamate, epoxy, and polysiloxane resins. Among these, polyolefin resins include amorphous polyolefin resins that have polymer units of cyclic polyolefins such as norcamphene monomers or polycyclic norcamphene monomers. Generally, it is preferable to select a protective film that does not impede the performance of the polarizing element after laminating the protective film. Such a protective film is particularly preferred to be composed of cellulose triacetate (TAC) and norbornene, which are cellulose acetate resins. Alternatively, as long as the effects of the present invention are not compromised, the protective film may also be a protective film that has undergone hard coating or anti-reflective treatment, or treatments for purposes such as anti-sticking, anti-diffusion, or anti-glare. A thickness of 10 to 200 μm for the transparent protective layer is preferred.

[0297] The polarizing plate of the present invention preferably has an adhesive layer between the transparent protective layer and the polarizing element, which provides a means for bonding the transparent protective layer and the polarizing element. The adhesive constituting the adhesive layer is not particularly limited. Examples include polyvinyl alcohol (PVA) adhesives, ethyl carbamate emulsion adhesives, acrylic adhesives, and polyester-isocyanate adhesives, with PVA adhesives being preferred. Examples of PVA adhesives include GOHSENOL NH-26 (manufactured by Nippon Gosei Corporation) and EXCEVAL RS-2117 (manufactured by KURARAY Corporation), but are not limited to these. Crosslinking agents and / or hydration-resistant agents may be added to the adhesive. Maleic anhydride-isobutylene copolymer is preferred as the PVA adhesive, and adhesives mixed with crosslinking agents may be used as needed. Examples of maleic anhydride-isobutylene copolymers include: ISOBAM#18 (manufactured by KURARAY), ISOBAM#04 (manufactured by KURARAY), ammonia-modified ISOBAM#104 (manufactured by KURARAY), ammonia-modified ISOBAM#110 (manufactured by KURARAY), imidized ISOBAM#304 (manufactured by KURARAY), and imidized ISOBAM#310 (manufactured by KURARAY). Water-soluble polyvalent epoxy compounds can be used as crosslinking agents in these cases. Examples of water-soluble polyvalent epoxy compounds include: DENACOL EX-521 (manufactured by NAGASE CHEMTEX) and TETRAD-C (manufactured by Mitsui GAS Chemical Co., Ltd.). Furthermore, adhesives other than polyvinyl alcohol-based resins can also be used, such as ethyl carbamate-based, acrylic-based, and epoxy-based adhesives that are already known. Polyvinyl alcohol modified with acetyl groups is particularly preferred, and polyaldehydes are even more preferred as the crosslinking agent. In addition, to improve the adhesion or water resistance of the adhesive, additives such as zinc compounds, chlorides, and iodides may be added, either alone or simultaneously, at a concentration of approximately 0.1 to 10% by mass. There are no particular limitations on the additives used in the adhesive; those skilled in the art can choose appropriately. 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.

[0298] When the polarizing element or polarizing plate of the present invention is bonded to a display device such as a liquid crystal or organic electroluminescent display (commonly referred to as OLED or OEL), various functional layers for improving viewing angle and / or contrast, as well as brightening layers or films, may be provided on the surface of the protective layer or film that is not exposed thereafter. Examples of functional layers include layers or films for controlling phase difference. The polarizing plate is preferably bonded to these films or display devices using an adhesive. By attaching a phase difference plate, the polarizing plate of the present invention can also be used as an elliptical polarizing plate. The polarizing plate is preferably bonded to these films or display devices using an adhesive.

[0299] The polarizing element or polarizing plate of the present invention may have various known functional layers such as an AR layer (anti-reflective layer), an anti-glare layer, and a hard coating layer on the exposed surface of its transparent protective layer or film. In fabricating layers with these various functionalities, a coating method is preferred, but films with these functions may also be bonded together through an adhesive or bonding agent.

[0300] Examples of hard coatings mentioned above include protective layers such as acrylic-based, polysiloxane-based, and ethyl carbamate-based hard coatings. Furthermore, the AR layer can be used to further improve the light transmittance of the single-panel substrate. The AR layer can be formed by coating, vapor deposition, or sputtering with materials such as silicon dioxide or titanium dioxide. Alternatively, it can be formed by thinly coating with a fluorine-based material.

[0301] The polarizing plate of the present invention has high transmittance and high polarization, and can further be a polarizing plate that has high transmittance and high polarization, and achieves achromaticity. In particular, it can achieve the white of high-quality paper when displaying white, and can represent neutral black when displaying black, and has high durability.

[0302] <Display Device>

[0303] The polarizing element or polarizing plate of the present invention is provided with a protective layer or functional layer and a transparent support such as glass, crystal, or sapphire as needed, and can be applied to LCD projectors, electronic computers, clocks, laptops, word processors, LCD TVs, polarizing lenses, polarizing glasses, navigators, and indoor and outdoor measuring instruments or displays, etc.

[0304] In particular, the polarizing element or polarizing plate of the present invention is used in liquid crystal display devices, such as reflective liquid crystal display devices, transmissive liquid crystal display devices, and other types of liquid crystal display devices, and is more preferably used in organic electroluminescent devices. Liquid crystal display devices manufactured using the polarizing element or polarizing plate of the present invention can display white and neutral black, similar to high-quality paper. Furthermore, this liquid crystal display device exhibits high durability and reliability, long-term high contrast, and high color reproduction.

[0305] [Example]

[0306] The present invention will now be described in more detail by way of examples, but the invention is not limited thereto. Unless otherwise stated, % in the examples refers to mass.

[0307] [Synthesis example 1]

[0308] (Step 1)

[0309] 15.0 parts of N-acetyl-1,4-phenylenediamine, which is available commercially, was added to 200 parts of water and stirred. Then, 42 parts of 35% hydrochloric acid and 17.3 parts of 40% sodium nitrite were added and stirred for 1 hour to carry out diazolation. Next, 32.0 parts of 1,8-dihydroxynaphthalene-3,6-disulfonic acid were added to 200 parts of water and dissolved in a 25% sodium hydroxide aqueous solution to make it weakly alkaline. In this solution, the previously obtained diazo solution was maintained at pH 6.5 to 8.0 and added dropwise while stirring to complete the coupling reaction. Subsequently, the resulting reaction solution was stirred at 90°C to 99°C for 5 hours at pH 0.0 to 0.5 to carry out a hydrolysis reaction. The precipitated solid was filtered to obtain 150 parts of wet bulk of the monoazo compound shown in formula (13).

[0310]

[0311] (Step 2)

[0312] 150 parts of the wet mass of the monoazo compound of formula (13) were added to 300 parts of water and stirred to suspend it. The pH was adjusted to 9.0 using 25% sodium hydroxide, and 17.3 parts of a 40% sodium nitrite aqueous solution were added. 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 were added to the resulting diazo solution, and the pH was maintained at 1.5 to 4.0 using a 15% sodium carbonate aqueous solution. The mixture was stirred for 8 hours to complete the coupling reaction. Subsequently, the mixture was salted out with sodium chloride and then filtered to obtain 200 parts of the wet mass of the diazo compound of formula (14).

[0313]

[0314] (Step 3)

[0315] 200 parts of the wet mass of the diazo compound shown in formula (14) was added to 500 parts of water and stirred to suspend it. The pH was adjusted to 9.0 using 25% sodium hydroxide, and 17.3 parts of a 40% sodium nitrite aqueous solution were added. The resulting suspension was dripped into a mixture of 200 parts of water and 42 parts of 35% hydrochloric acid to prepare a diazo solution. On the other hand, 31.5 parts of 1-hydroxy-6-aniline-3-naphthalenesulfonic acid was added to 300 parts of water and dissolved in a 25% sodium hydroxide aqueous solution to make it weakly alkaline. In this solution, the previously obtained diazo solution was maintained at pH 6.5 to 8.0 and dripped while stirring to complete the coupling reaction. Subsequently, after salting out with sodium chloride, the mixture was filtered and dried to obtain 8.0 parts of the azo compound shown in Examples 3-8.

[0316] [Example 1]

[0317] A polyvinyl alcohol film (VF-PS#7500 manufactured by KURARAY) with a saponification degree of 99% or higher and an average degree of polymerization of 2400 was immersed in warm water at 40°C for 3 minutes, subjected to swelling treatment, and stretched at a stretch ratio of 1.30. The resulting film was immersed in a dyeing solution adjusted to 45°C for 8 minutes, so that the film contained an azo compound. The dyeing solution contained 1500 parts by mass of water, 1.5 parts by mass of sodium tripolyphosphate, 1.5 parts by mass of anhydrous sodium sulfate, 0.36 parts by mass of the azo compound described in formula (7) of Japanese Patent Application Publication No. 2002-275381 belonging to formula (2), and 0.22 parts by mass of compound examples 3-8 of the azo compound of formula (3) obtained in Synthesis Example 1. The resulting film was immersed in an aqueous solution containing 20 g / L of boric acid (manufactured by Fuji Film and Koko Pure Chemical Industries Co., Ltd.) at 40°C for 1 minute. The impregnated film was stretched to 5.0 times its original length and subjected to a stretching treatment for 5 minutes in an aqueous solution containing 30.0 g / L boric acid at 50°C. The resulting film was then kept taut and washed by immersion in water at 25°C for 20 seconds. The washed film was dried at 70°C for 9 minutes to obtain a polarizing element. For this polarizing element, a polarizing plate was obtained by laminating an alkali-treated cellulose triacetate film (ZRD-60, manufactured by Fuji Film Co., Ltd.) using a 4% solution of polyvinyl alcohol (NH-26, manufactured by VAM&POVAL Co., Ltd., Japan) as an adhesive. The obtained polarizing plate maintained the optical properties of the aforementioned polarizing element, particularly monomer transmittance at each wavelength, parallel transmittance at each wavelength, cross-sectional transmittance at each wavelength, hue, and polarization. This polarizing plate was used as the test sample in Example 1.

[0318] [Synthesis example 2]

[0319] Except that the 31.5 parts of 1-hydroxy-6-aniline-3-naphthalenesulfonic acid in step 3 of Synthesis Example 1 were changed to 34.5 parts of 1-hydroxy-6-(4-methoxyphenylamino)-3-naphthalenesulfonic acid, the rest were performed in the same manner as in Synthesis Example 1 to obtain 8.0 parts of the azo compound shown in Compound Examples 3-10.

[0320] [Example 2]

[0321] Except for treating the film obtained by the swelling treatment with a dyeing solution at 45°C for 8 minutes, and containing an azo compound, the polarizing plate was prepared in the same manner as in Example 1. The dyeing solution contained 1500 parts by weight of water, 1.5 parts by weight of sodium tripolyphosphate, 1.5 parts by weight of anhydrous sodium sulfate, 0.37 parts by weight of compound example 2-102 belonging to formula (2) obtained according to the manufacturing method of Non-Patent Document 1, 0.26 parts by weight of compound example 3-10 belonging to formula (3) obtained according to Synthetic Example 2, and 0.27 parts by weight of compound example 4-1 belonging to formula (4) obtained according to the manufacturing method of WO2007 / 138980.

[0322] [Synthesis example 3]

[0323] Except for changing 31.5 parts of 1-hydroxy-6-aniline-3-naphthalenesulfonic acid in step 3 of Synthesis Example 1 to 35.8 parts of 1-hydroxy-6-(4-aminobenzoylamino)-3-naphthalenesulfonic acid, the other steps were performed in the same manner as in Synthesis Example 1 to obtain 11.0 parts of the azo compound shown in Compound Examples 3-31.

[0324] [Example 3]

[0325] Except for applying a swelling treatment and treating the resulting film with a dyeing solution at 45°C for 8 minutes, and containing an azo compound, the polarizing plate was prepared in the same manner as in Example 1. The dyeing solution contained 1500 parts by weight of water, 1.5 parts by weight of sodium tripolyphosphate, 1.5 parts by weight of anhydrous sodium sulfate, 0.26 parts by weight of compound example 1-13 of formula (1) (an azo compound of WO2016 / 186194 (28)), and 0.25 parts by weight of compound example 4-1 of formula (4) of the manufacturing method according to WO2007 / 138980.

[0326] [Synthesis Example 4]

[0327] Except for replacing 32.0 parts of 1,8-dihydroxynaphthalene-3,6-disulfonic acid in step 1 of Synthesis Example 1 with 33.4 parts of 1-hydroxy-8-methoxynaphthalene-3,6-disulfonic acid, and replacing 31.5 parts of 1-hydroxy-6-aniline-3-naphthalenesulfonic acid in step 3 of Synthesis Example 1 with 37.5 parts of 1-hydroxy-6-(2,4-dimethoxyphenylamino)-3-naphthalenesulfonic acid, the other steps were performed in the same manner as in Synthesis Example 1 to obtain 12.0 parts of the azo compound shown in Compound Examples 3-15.

[0328] [Example 4]

[0329] Except for applying a swelling treatment and treating the resulting film with a dyeing solution at 45°C for 8 minutes, and containing an azo compound, the polarizing plate was prepared in the same manner as in Example 1. The dyeing solution contained 1500 parts by weight of water, 1.5 parts by weight of sodium tripolyphosphate, 1.5 parts by weight of anhydrous sodium sulfate, 0.21 parts by weight of compound examples 2-29 belonging to the azo compound described in formula (2) obtained according to the manufacturing method of Non-Patent Document 1, 0.28 parts by weight of compound examples 3-15 belonging to the azo compound of formula (3) obtained in Synthetic Example 4, and 10.25 parts by weight of compound examples 4-1 belonging to the azo compound of formula (4) obtained according to the manufacturing method of WO2007 / 138980.

[0330] [Synthesis example 5]

[0331] Except for replacing 31.5 parts of 1-hydroxy-6-aniline-3-naphthalenesulfonic acid in step 3 of Synthesis Example 1 with 34.4 parts of the compound shown in Formula (15) below, the rest was performed in the same manner as in Synthesis Example 1 to obtain 11.3 parts of the azo compound shown in Compound Examples 3-32.

[0332]

[0333] [Example 5]

[0334] Except for applying a swelling treatment and treating the resulting film with a dyeing solution at 45°C for 8 minutes, and containing an azo compound, the polarizing plate was prepared in the same manner as in Example 1. The dyeing solution contained 1500 parts by weight of water, 1.5 parts by weight of sodium tripolyphosphate, 1.5 parts by weight of anhydrous sodium sulfate, 0.18 parts by weight of CI Direct Red 117 (compound examples 2-6) belonging to formula (2), 0.30 parts by weight of compound examples 3-32 belonging to formula (3) obtained in Synthesis Example 5, and 10.25 parts by weight of compound examples 4-1 belonging to formula (4) obtained according to the manufacturing method of WO2007 / 138980.

[0335] [Example 6]

[0336] Except for applying a swelling treatment and treating the resulting film with a dyeing solution at 45°C for 8 minutes, and containing an azo compound, the polarizing plate was prepared in the same manner as in Example 1. The dyeing solution contained 1500 parts by weight of water, 1.5 parts by weight of sodium tripolyphosphate, 1.5 parts by weight of anhydrous sodium sulfate, 0.27 parts by weight of compound example 2-77 belonging to the azo compound of formula (2) obtained according to the manufacturing method of Japanese Patent Application Publication No. 8-291259, 0.28 parts by weight of compound example 3-10 belonging to the azo compound of formula (3) obtained in Synthesis Example 2, and 0.22 parts by weight of compound example 4-2 belonging to the azo compound of formula (4) (the azo compound described in Synthesis Example 1 of WO2007 / 138980).

[0337] [Synthesis example 6]

[0338] Except for changing 32.0 parts of 1,8-dihydroxynaphthalene-3,6-disulfonic acid in step 1 of Synthesis Example 1 to 30.4 parts of 1-hydroxynaphthalene-3,6-disulfonic acid, the rest of the procedure was performed in the same manner as in Synthesis Example 1 to obtain 13.5 parts of the azo compounds shown in Compounds 3-7.

[0339] [Example 7]

[0340] Except for applying a swelling treatment and treating the resulting film with a dyeing solution at 45°C for 8 minutes, and containing an azo compound, the polarizing plate was prepared in the same manner as in Example 1. The dyeing solution contained 1500 parts by weight of water, 1.5 parts by weight of sodium tripolyphosphate, 1.5 parts by weight of anhydrous sodium sulfate, 0.23 parts by weight of compound example 2-70 belonging to the azo compound of formula (2) obtained according to the manufacturing method of Japanese Patent Application Publication No. 8-291259, 0.29 parts by weight of compound example 3-7 belonging to the azo compound of formula (3) obtained in Synthesis Example 6, and 0.24 parts by weight of compound example 4-2 belonging to the azo compound of formula (4) (the azo compound described in Synthesis Example 1 of WO2007 / 138980).

[0341] [Synthesis Example 7]

[0342] (Step 1)

[0343] 150 parts of the wet bulk of the monoazo compound of formula (13) from step 1 of Synthesis Example 1 were added to 300 parts of water and stirred to suspend it. The pH was adjusted to 9.0 using 25% sodium hydroxide, and 17.3 parts of a 40% sodium nitrite aqueous solution were added. 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-dimethoxyaniline were added to the obtained diazo solution, and the pH was maintained at 1.5 to 4.0 using a 15% sodium carbonate aqueous solution and stirred for 8 hours to complete the coupling reaction. Subsequently, the mixture was salted out with sodium chloride and then filtered to obtain 200 parts of the wet bulk of the diazo compound of formula (16).

[0344]

[0345] (Step 2)

[0346] 150 parts of the wet mass of the monoazo compound of formula (16) were added to 300 parts of water and stirred to suspend it. The pH was adjusted to 9.0 using 25% sodium hydroxide, and 17.3 parts of a 40% sodium nitrite aqueous solution were added. 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 were added to the obtained diazo solution, and the pH was maintained at 1.5 to 4.0 using a 15% sodium carbonate aqueous solution while stirring for 8 hours to complete the coupling reaction. Subsequently, the mixture was salted out with sodium chloride and then filtered to obtain 200 parts of the wet mass of the azo compound of formula (17).

[0347]

[0348] (Step 3)

[0349] 200 parts of the wet mass of the azo compound shown in formula (17) was added to 500 parts of water and stirred to suspend it. The pH was adjusted to 9.0 using 25% sodium hydroxide, and 17.3 parts of a 40% sodium nitrite aqueous solution were added. 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. On the other hand, 31.5 parts of 1-hydroxy-6-aniline-3-naphthalenesulfonic acid were added to 300 parts of water and dissolved in a 25% sodium carbonate aqueous solution to make it weakly alkaline. In this solution, the previously obtained diazo solution was maintained at pH 6.5 to 8.0 and added dropwise while stirring to complete the coupling reaction. Subsequently, after salting out with sodium chloride, the mixture was filtered and dried to obtain 11.0 parts of the azo compound shown in Examples 3-42.

[0350] [Example 8]

[0351] Except for applying a swelling treatment and treating the resulting film with a dyeing solution at 45°C for 8 minutes, and containing an azo compound, the polarizing plate was prepared in the same manner as in Example 1. The dyeing solution contained 1500 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 examples 1-23 belonging to formula (1) (azo compound of formula (54) in WO2016 / 186194), 0.35 parts by mass of compound examples 3-42 obtained from synthesis example 7 of azo compound belonging to formula (3), and 0.26 parts by mass of compound example 4-2 belonging to formula (4) (azo compound described in synthesis example 1 of WO2007 / 138980).

[0352] [Synthesis example 8]

[0353] Except for replacing 31.5 parts of 1-hydroxy-6-aniline-3-naphthalenesulfonic acid in step 3 of Synthesis Example 1 with 55.1 parts of the compound shown in formula (18) below, the rest was performed in the same manner as in Synthesis Example 1 to obtain 6.2 parts of the azo compound shown in Compound Examples 3-35.

[0354]

[0355] [Example 9]

[0356] Except for applying a swelling treatment and treating the resulting film with a dyeing solution at 45°C for 8 minutes, and containing an azo compound, the polarizing plate was prepared in the same manner as in Example 1. The dyeing solution contained 1500 parts by weight of water, 1.5 parts by weight of sodium tripolyphosphate, 1.5 parts by weight of anhydrous sodium sulfate, 0.26 parts by weight of compound example 2-95 belonging to the azo compound of formula (2) obtained according to the manufacturing method of Japanese Patent Application Publication No. 8-291259, 0.37 parts by weight of compound example 3-35 obtained from synthesis example 8 of the azo compound belonging to formula (3), and 0.25 parts by weight of compound example 5-88 belonging to the azo compound of formula (5) (the azo compound described in compound example 1-B83 of WO2019 / 124161).

[0357] [Example 10]

[0358] Except for applying a swelling treatment and treating the resulting film with a dyeing solution at 45°C for 8 minutes, and containing an azo compound, the polarizing plate was prepared in the same manner as in Example 1. The dyeing solution contained 1500 parts by weight of water, 1.5 parts by weight of sodium tripolyphosphate, 1.5 parts by weight of anhydrous sodium sulfate, 0.23 parts by weight of compound example 2-70 belonging to formula (2) obtained according to the manufacturing method of Japanese Patent Application Publication No. 8-291259, 0.26 parts by weight of compound example 3-8 belonging to formula (3) obtained from Synthesis Example 1, and 0.25 parts by weight of compound example 5-88 belonging to formula (5) (the azo compound described in compound example 1-B83 of WO2019 / 124161).

[0359] [Synthesis Example 9]

[0360] Except for replacing 31.5 parts of 1-hydroxy-6-aniline-3-naphthalenesulfonic acid in step 3 of Synthesis Example 1 with 25.3 parts of 1-hydroxy-6-methylamino-3-naphthalenesulfonic acid, the rest of the procedure was performed in the same manner as in Synthesis Example 1 to obtain 9.2 parts of the azo compounds shown in Compound Examples 3-36.

[0361] [Example 11]

[0362] Except for applying a swelling treatment and treating the resulting film with a dyeing solution at 45°C for 8 minutes, and containing an azo compound, the polarizing plate was prepared in the same manner as in Example 1. The dyeing solution contained 1500 parts by weight of water, 1.5 parts by weight of sodium tripolyphosphate, 1.5 parts by weight of anhydrous sodium sulfate, 0.25 parts by weight of compound examples 1-13 of the azo compound belonging to formula (1) (azo compound of formula (28) in WO2016 / 186194), 0.24 parts by weight of compound examples 3-36 of the azo compound belonging to formula (3) obtained in Synthesis Example 9, and 0.22 parts by weight of compound examples 5-3 of the azo compound belonging to formula (5) (azo compound described in compound examples 1-A4 of WO2019 / 124161).

[0363] [Synthesis Example 10]

[0364] Except for changing 31.5 parts of 1-hydroxy-6-aniline-3-naphthalenesulfonic acid in step 3 of Synthesis Example 1 to 37.5 parts of 1-hydroxy-6-(2,4-dimethoxyphenylamino)-3-naphthalenesulfonic acid, the rest of the procedure was performed in the same manner as in Synthesis Example 1 to obtain 8.9 parts of the azo compound shown in Compound Examples 3-14.

[0365] [Example 12]

[0366] Except for applying a swelling treatment and treating the resulting film with a dyeing solution at 45°C for 8 minutes, and containing an azo compound, the polarizing plate was prepared in the same manner as in Example 1. The dyeing solution contained 1500 parts by weight of water, 1.5 parts by weight of sodium tripolyphosphate, 1.5 parts by weight of anhydrous sodium sulfate, 0.30 parts by weight of compound example 2-103 belonging to the azo compound of formula (2) obtained according to the manufacturing method disclosed in Japanese Patent Application Publication No. 2002-275381, 0.29 parts by weight of compound example 3-14 belonging to the azo compound of formula (3) obtained in Synthetic Example 10, and 0.21 parts by weight of compound example 5-84 belonging to the azo compound of formula (5) (the azo compound described in compound example 1-B64 of WO2019 / 124161).

[0367] [Example 13]

[0368] Except for applying a swelling treatment and treating the resulting film with a dyeing solution at 45°C for 8 minutes, and containing an azo compound, the polarizing plate was prepared in the same manner as in Example 1. The dyeing solution contained 1500 parts by weight of water, 1.5 parts by weight of sodium tripolyphosphate, 1.5 parts by weight of anhydrous sodium sulfate, 0.29 parts by weight of compound example 2-59 belonging to formula (2) (compound example of formula (17) of WO2012 / 108169), 0.29 parts by weight of compound example 3-10 belonging to formula (3) of synthesis example 2, and 0.21 parts by weight of compound example 5-84 belonging to formula (5) (compound example 1-B64 of WO2019 / 124161).

[0369] [Example 14]

[0370] Except for the application of swelling treatment and the treatment of the resulting film with a dyeing solution at 45°C for 8 minutes, which contains an azo compound, the polarizing plate was prepared in the same manner as in Example 1. The dyeing solution contained 1500 parts by weight of water, 1.5 parts by weight of sodium tripolyphosphate, 1.5 parts by weight of anhydrous sodium sulfate, 0.30 parts by weight of compound example 2-103 belonging to the azo compound of formula (2) obtained according to the manufacturing method disclosed in Japanese Patent Application Publication No. 2002-275381, 0.29 parts by weight of compound example 3-14 belonging to the azo compound of formula (3) obtained in Synthetic Example 10, and 0.20 parts by weight of CI DirectOrange 72, which has the same color component as the azo compound of formula (5) in compound example 5-84 (the azo compound described in compound example 1-B64 of WO2019 / 124161).

[0371] [Example 15]

[0372] Except for applying a swelling treatment and treating the resulting film with a dyeing solution at 45°C for 8 minutes, which contains an azo compound, the polarizing plate was prepared in the same manner as in Example 1. The dyeing solution contained 1500 parts by weight of water, 1.5 parts by weight of sodium tripolyphosphate, 1.5 parts by weight of anhydrous sodium sulfate, 0.22 parts by weight of compound example 2-26 belonging to formula (2) (azo compound described in formula (4) of WO2005 / 075572), 0.29 parts by weight of compound example 3-7 belonging to formula (3) obtained in Synthesis Example 6, and 0.30 parts by weight of CI Direct Yellow 12.

[0373] [Comparative Example 1]

[0374] A high-transmittance dye-based polarizing plate SHC-115 with neutral gray color, manufactured by POLATECHNO, was obtained as a test sample.

[0375] [Comparative Example 2]

[0376] A POLATECHNO dye-based polarizing plate SHC-128 with high contrast, which is neutral gray as a general dye-based polarizing plate, was obtained and used as the test sample.

[0377] [Comparative Examples 3 to 8]

[0378] According to the manufacturing method described in Comparative Example 1 of Patent Document 9, except that the time containing iodine was changed to 5 minutes and 30 seconds in Comparative Example 3, 4 minutes and 45 seconds in Comparative Example 4, 4 minutes and 15 seconds in Comparative Example 5, 3 minutes and 30 seconds in Comparative Example 6, 4 minutes and 0 seconds in Comparative Example 7, and 5 minutes and 15 seconds in Comparative Example 8, the iodine-based polarizing plate without azo compound was produced in the same way and used as a test sample.

[0379] [Comparative Example 9]

[0380] An iodine-based polarizing plate SKW-18245P manufactured by POLATECHNO, which displays paper white in parallel positions, was obtained and used as the test sample.

[0381] [Comparative Examples 10 and 11]

[0382] In Example 1, except that the aqueous solution containing azo compound (dyeing solution) was set to the composition described in Example 1 of Patent Document 3, and the dyeing time of each was changed to 6 minutes and 5 minutes, the rest were performed in the same way, and the time for immersing the swollen membrane in the aqueous solution was adjusted so that the monomer transmittance Ys described later was about 41%, and polarizing plates of Comparative Example 10 and Comparative Example 11 were produced respectively containing azo compound.

[0383] [Comparative Example 12]

[0384] The polarizing plate described in Example 1 of Patent Document 8, which relates to the manufacture of a dye-based polarizing plate.

[0385] [Comparative Example 13]

[0386] The polarizing plate described in Example 3 of Patent Document 9, which relates to the manufacture of a dye-based polarizing plate.

[0387] [Comparative Example 14]

[0388] The polarizing plate described in Example 1 of Patent Document 10, which relates to the manufacture of a dye-based polarizing plate.

[0389] [Comparative Example 15]

[0390] The polarizing plate described in Example 15 (No. 1) of Patent Document 11, which relates to the manufacture of a dye-based polarizing plate.

[0391] [Comparative Example 16]

[0392] In Example 10, except that CI Direct Red 80, which has dichroism with homochromatic properties, was used to replace the azo compounds of Compound Examples 2-70, the dyeing solution was prepared in such a way that the resulting polarizing element had the same monomer transmittance, and the polarizing element contained an azo compound, the process was the same as in Example 10, and a polarizing plate was made.

[0393] [Comparative Example 17]

[0394] In Example 10, except that the azo compounds of Examples 3-8 were replaced with CI Direct Blue 67, which belongs to the dichroism of azo compounds and has homochromatic properties, the dyeing solution was prepared in such a way that the resulting polarizing element had the same monomer transmittance, and the polarizing element contained azo compound, the same procedure was followed as in Example 10 to prepare a polarizing plate.

[0395] [Evaluation Methodology]

[0396] The assay samples obtained in Examples 1 to 15 and Comparative Examples 1 to 17 were evaluated as follows.

[0397] (a) Single-cell transmittance Ts, parallel-position transmittance Tp, and orthogonal-position transmittance Tc at each wavelength

[0398] The monomer transmittance (Ts), parallel-position transmittance (Tp), and orthogonal-position transmittance (Tc) of each wavelength for each test sample were measured using a spectrophotometer (Hitachi Highech Science, U-4100). Here, the monomer transmittance (Ts) at each wavelength is measured with one test sample. The parallel-position transmittance (Tp) at each wavelength is measured by overlapping two test samples with their absorption axes parallel. The orthogonal-position transmittance (Tc) at each wavelength is measured by overlapping two test samples with their absorption axes orthogonal. Measurements were performed covering the wavelength region from 380 to 780 nm.

[0399] (b) Visual perception corrected single-unit transmittance Ys, visual perception corrected parallel-position transmittance Yp, and visual perception corrected orthogonal-position transmittance Yc

[0400] The visual sensitivity-corrected monomer transmittance Ys (%), visual sensitivity-corrected parallel-position transmittance Yp (%), and visual sensitivity-corrected orthogonal-position transmittance Yc (%) of each test sample were calculated separately. The visual sensitivity-corrected monomer transmittance Ys (%), visual sensitivity-corrected parallel-position transmittance Yp (%), and visual sensitivity-corrected orthogonal-position transmittance Yc (%) are calculated for each wavelength in the wavelength region from 380 to 780 nm at each predetermined wavelength interval dλ (here, 5 nm), with the aforementioned monomer transmittance Ts, parallel-position transmittance Tp, and orthogonal-position transmittance Tc corrected to visual sensitivity transmittance according to JIS Z 8722:2009. Specifically, the monomer transmittance Ts, parallel-position transmittance Tp, and orthogonal-position transmittance Tc for each wavelength were substituted into the following equations (I to III) for calculation. Furthermore, in the following equations (I to III), Pλ represents the spectral distribution of the standard light (C source), and τλ represents the isochromatic function of a 2-degree field of view. The results are presented in Table 1.

[0401]

[0402]

[0403]

[0404] (c) Comparison

[0405] The ratio (Yp / Yc) of the visually corrected parallel transmittance Yp to the visually corrected orthogonal transmittance Yc, measured using two identical test samples, was calculated, and the contrast ratio (CR) was determined accordingly. The results are shown in Table 1.

[0406] (d) Polarization ρy after visual sensitivity correction

[0407] Substitute the visual sensitivity-corrected parallel transmittance Yp and the visual sensitivity-corrected orthogonal transmittance Yc into Equation (IV) below to calculate the visual sensitivity-corrected polarization ρy of each test sample. The results are shown in Tables 1 and 2.

[0408] Py = {(Yp-Yc) / (Yp+Yc)} 1 / 2 ×100 (IV)

[0409] [Table 1]

[0410]

[0411] [Table 2]

[0412]

[0413] Comparing Examples 1 to 15 with Comparative Examples 1 and 10 to 17, it can be seen that the polarizing plate of the present invention has high polarization or contrast. Furthermore, when comparing examples with approximately equal polarization and contrast, the monomer transmittance of Comparative Example 2 is about 1 to 2% lower. Therefore, it can be seen that the polarizing plate of the present invention improves the performance of dye-based polarizing plates. In addition, as described later, while Comparative Examples 3 to 9 yielded polarizing plates with high contrast and high polarization, their durability was low.

[0414] Secondly, the average transmittance (AT) of the parallel site transmittance Tp and the orthogonal site transmittance Tc obtained through the aforementioned measurements at 420 to 480 nm was calculated. 420-480 Average transmittance (AT) in the 520 to 590 nm range 520-590 ), and average transmittance (AT) in the 600 to 640 nm range. 600-640 The symbols are shown in Tables 3 and 4.

[0415] [Table 3]

[0416]

[0417] [Table 4]

[0418]

[0419] (e) The absolute value of the difference in average transmittance between the two wavelength bands

[0420] The display shows the average transmittance (AT) of each sample at each wavelength, including the parallel transmittance Tp and the orthogonal transmittance Tc, from 520 to 590 nm. 520-590 ) and average transmittance (AT) in the range of 420 to 480 nm 420-480 The absolute value of the difference, and the average transmittance (AT) measured in the range of 520 to 590 nm. 520-590) and average transmittance (AT) in the 600 to 640 nm range 600-640 The absolute value of the difference between the two. The results are shown in Tables 5 and 6.

[0421] [Table 5]

[0422]

[0423] [Table 6]

[0424]

[0425] Table 3 shows the average transmittance (AT) of the parallel position transmittance Tp of the samples measured in Examples 1 to 15 at various wavelengths from 520 to 590 nm. 520-590 The percentage was over 32.15%, and high.

[0426] Furthermore, as can be seen from Tables 3 to 6, the average transmittance (AT) in the parallel position transmittance Tp of Examples 3 and 5 to 15 is... 520-590 ) and average penetration (AT) 420-480 The difference between the two values ​​is less than 3.0, and the average transmittance (AT) is less than 3.0. 520-590 ) and average penetration (AT) 600-640 The difference is less than 2.5. Furthermore, it is known that the average transmittance (AT) in the parallel position transmittance Tp of the samples measured in Examples 6, 7, 12, and 14 is less than 2.5. 520-590 ) and average penetration (AT) 420-480 The difference between the two, and the average transmittance (AT) in the parallel position transmittance Tp. 520-590 ) and average penetration (AT) 600-640 The differences between the wavelength bands are all within 2%, and the differences between each wavelength band are significantly small. Furthermore, it can be seen that the average transmittance (AT) in the orthogonal position transmittance Tc of Examples 6, 12, and 14 is within 2%. 520-590 ) and average penetration (AT) 420-480 The difference between the orthogonal penetration Tc and the average penetration (AT) 520-590 ) and average penetration (AT) 600-640 The differences in Tc values ​​were all within 1%, and compared to Comparative Examples 1 to 9 and Comparative Examples 12 to 17, the polarizing plate of the present invention also showed no difference between wavelength bands in Tc at each wavelength. On the other hand, the average transmittance (AT) in the measured sample Tp of Comparative Examples 10 to 11 was... 520-590 ) and average penetration (AT) 420-480 The difference is within 2.5%, and the average penetration rate (AT) in Tp 520-590 ) and average penetration (AT) 600-640The difference in transmittance is within 3.0%, and the difference in average transmittance in Tc is 1%, but as shown in Table 2, the contrast and polarization are low. From the above results, it can be seen that the polarizing element of this application can achieve a polarizing element or polarizing plate with high transmittance and high polarization, and no wavelength dependence in Tp and Tc at each wavelength.

[0427] (f) Colorimetric a* and b* values

[0428] For each test sample, according to JIS Z 8781-4:2013, the chromaticity a* and b* values ​​were determined when measuring the monomer transmittance Ts, the parallel transmittance Tp, and the orthorhombic transmittance Tc at each wavelength. The spectrophotometer described above was used for the measurements. A C light source was used. 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 monomer transmittance Ts, the parallel transmittance Tp, and the orthorhombic transmittance Tc, respectively.

[0429] (g) Observation of color

[0430] For each test sample, two identical test samples were superimposed on a mirror commercially available as a reflector in both parallel and orthogonal positions, and the observed colors were investigated. Observations were conducted visually by 10 observers, and the most frequently observed colors are shown in Tables 7 and 8. Furthermore, in the tables, the color in the parallel position refers to the color when two identical test samples are superimposed with their absorption axes parallel (when displayed as white), and the color in the orthogonal position refers to the color when two identical test samples are superimposed with their absorption axes orthogonal (when displayed as black). Basically, the color in the parallel position of the polarized light is "white," and the color in the orthogonal position is "black." However, in the examples or comparative examples, for example, white with a yellowish tint is represented as "yellow," and black with a bluish-purple tint is represented as "bluish-purple."

[0431] [Table 7]

[0432]

[0433] [Table 8]

[0434]

[0435] As shown in Tables 7 and 8, the visual sensitivity-corrected monomer transmittance Ys of the test samples in Examples 1 to 15 is 40% or higher. Furthermore, the absolute values ​​of chromaticity a*-s and b*-s of the test samples in Examples 2, 7, 12, 14, and 15 are all 1.0 or less, and the absolute values ​​of chromaticity a*-p and b*-p are as low as 2.0 or less. Moreover, the high transmittance and high polarization (over 97%) indicate that white and black can be adequately represented. On the other hand, it is evident that the absolute values ​​of chromaticity a*-s and b*-s in Comparative Examples 1 to 9 and Comparative Examples 12 to 17 are all greater than 1, and the absolute values ​​of chromaticity a*-p and b*-p are all greater than 3. Alternatively, at least one of chromaticity a*-c and b*-c when the polarization is below 97% is greater than 1. Therefore, conventional polarizing elements or polarizing plates cannot adequately represent white and black. In addition, in the test samples of Comparative Examples 10 to 11, white and black colors were well represented, but as shown in Table 2, the contrast and polarization were low.

[0436] The results above show that the polarizing element of the present invention has high transmittance and high polarization, and there is no color in both parallel and orthogonal positions. That is, it can realize a polarizing element or polarizing plate that can fully represent white and black.

[0437] As shown above, the polarizing element of the present invention can maintain high single-cell transmittance and parallel-position transmittance, and can display a high-quality white like paper in the parallel position, and also displays a high-quality neutral color (achromatic neutral gray) with no coloration of the single-cell components. Furthermore, it can be seen that the polarizing element of the present invention, in addition to maintaining high single-cell transmittance after visual sensitivity correction and displaying achromaticity in the parallel position, also possesses high polarization. Furthermore, it can be seen that the polarizing element of the present invention can be used to obtain a high-quality achromatic black displayed in the orthogonal position.

[0438] (h) Durability test

[0439] The test samples of Examples 1 to 17 and Comparative Examples 3 to 9 were placed in an environment of 85°C at 85% relative humidity for 240 hours for durability testing. As a result, no change in transmittance or hue was observed in the test samples of Examples 1 to 17. In contrast, the test samples of Comparative Examples 3 to 9 showed a reduction in polarization of more than 10%, a chromaticity b*-c below -10, and a significant change in appearance to blue. In particular, when two test samples were arranged orthogonally (in black display), the color was a fully developed blue. Therefore, it can be seen that the polarizing element of the present invention has high durability.

[0440] [Industry availability]

[0441] The polarizing element or polarizing plate of the present invention can be used not only in liquid crystal display devices, such as reflective liquid crystal display devices, transmissive liquid crystal display devices, and other liquid crystal display devices, but also in organic electroluminescent devices. A liquid crystal display device equipped with the polarizing element or polarizing plate of the present invention can display high-quality white and neutral black, similar to paper. Furthermore, this liquid crystal display device can be used in liquid crystal display devices with high durability and reliability, long-term high contrast, and high color reproduction.

Claims

1. A polarizing element comprising, in the form of a free acid, an azo compound or a salt thereof as shown in formula (1) or an azo compound or a salt thereof as shown in formula (2), and comprising an azo compound or a salt thereof as shown in formula (3); In formula (1), Ac1 independently represents a phenyl or naphthyl group having at least one substituent selected from sulfonic acid and carboxyl groups, and Rc 11 To Rc 14 Each of the following can be independently represented: a hydrogen atom, a C1 to 4 alkyl group, a C1 to 4 alkoxy group, or a C1 to 4 alkoxy group having a sulfonic acid group; In formula (2), Ac2 represents a phenyl or naphthyl group having at least one substituent selected from sulfonic acid and carboxyl groups, and Rc 21 To Rc 28 Each of these groups independently represents a hydrogen atom, a C1 to 4 alkyl group, a C1 to 4 alkoxy group, or a C1 to 4 alkoxy group having a sulfonic acid group. Xc2 represents an unsubstituted amino group or an amino group having at least one substituent S2, an unsubstituted or substituted phenylamino group, an unsubstituted or substituted phenylazo group, an unsubstituted or substituted naphthoriazolyl group, or an unsubstituted or substituted benzoylamino group. When multiple substituents S2 are present, they are independently selected from unsubstituted or substituted C1 to 4 alkyl groups, C1 to 4 alkoxy groups, sulfonic acid groups, C1 to 4 alkylamino groups, hydroxyl groups, amino groups, substituted amino groups, carboxyl groups, and carboxyethylamino groups. r, p, and q independently represent 0 or 1, but exclude the case where r, p, and q are all 1. In addition, only either p or q is 1, and when Ac2 is a naphthyl group, it does not contain a hydroxyl group as a substituent. In formula (3), Ra1, Ra2, Ab1, or Ab2 is substituted on either ring a or ring b; either Ra1 or Ra2 is a hydroxyl group, and the other represents a hydrogen atom, a hydroxyl group, a C1 to C4 alkoxy group, or a C1 to C4 alkoxy group with a sulfonic acid group; either Ab1 or Ab2 represents a sulfonic acid group, a carboxyl group, or an unsubstituted or substituted amino group, and the other is a substituent selected from a hydrogen atom, a sulfonic acid group, a carboxyl group, or an unsubstituted or substituted amino group; Rb1 to Rb6 independently represent a hydrogen atom, a C1 to C4 alkyl group, a C1 to C4 alkoxy group, a sulfonic acid group, or a sulfonic acid group. The group consists of a C1 to C4 alkoxy group or an unsubstituted or substituted amino group, where h represents 0 or 1, and Xb1 represents an unsubstituted or substituted amino group or having at least one substituent S3, an unsubstituted or substituted phenylamino group, an unsubstituted or substituted phenylazo group, an unsubstituted or substituted naphthoriazolyl group, or an unsubstituted or substituted benzoylamino group. When multiple substituents S3 are present, they are independently selected from unsubstituted or substituted C1 to C4 alkyl groups, C1 to C4 alkoxy groups, sulfonic acid groups, amino groups, C1 to C4 alkylamino groups, hydroxyl groups, carboxyl groups, and carboxyethylamino groups.

2. The polarizing element according to claim 1 further comprises an azo compound or a salt thereof as shown in formula (4), or an azo compound or a salt thereof as shown in formula (5); In equation (4), Ay 11 Each of the following groups independently represents a sulfonic acid group, a carboxyl group, a hydroxyl group, a C1 to C4 alkyl group, or a C1 to C4 alkoxy group, Ry 11 To Ry 14 Each of the following can be independently represented: a hydrogen atom, a C1 to 4 alkyl group, a C1 to 4 alkoxy group, or a C1 to 4 alkoxy group having a sulfonic acid group; f represents an integer from 1 to 3. In equation (5), Ay 21 and Ay 22 Ry is independently an unsubstituted or substituent naphthyl group or an unsubstituted or substituent phenyl group. 21 Ry 22 Ry 27 and Ry 28 Ry is independently composed of a hydrogen atom, a C1 to 4 alkyl group, and a C1 to 4 alkoxy group. 23 To Ry 26 Each of the following is independently represented by a hydrogen atom, a C1 to 4 alkyl group, a C1 to 4 alkoxy group, or a C1 to 4 alkoxy group with a sulfonic acid group, and s and t independently represent 0 or 1, respectively.

3. The polarizing element according to claim 1 or 2, wherein, The azo compound or its salt shown in formula (3) above is the azo compound or its salt shown in formula (6) below; In equation (6), Ra1, Ra2, Ab1, Ab2, Rb1 to Rb6, h, and Xb1 represent the same meaning as in equation (3).

4. The polarizing element according to claim 1 or 2, wherein, The azo compound or its salt represented by formula (3) above is the azo compound or its salt represented by formula (7) below; In equation (7), Ra1, Ra2, Ab1, Ab2, Rb1 to Rb6, h, and Xb1 represent the same meaning as in equation (3).

5. The polarizing element according to claim 1 or 2, wherein, The azo compound or its salt represented by formula (3) above is the azo compound or its salt represented by formula (8) below; In formula (8), Ra1, Ab1, Rb1 to Rb6, h, and Xb1 have the same meaning as in formula (3), and Ra3 represents a hydrogen atom or a hydroxyl group.

6. The polarizing element according to claim 1 or 2, wherein, The azo compound or its salt represented by formula (3) above is the azo compound or its salt represented by formula (9) below; In the aforementioned equation (9), Ra1, Ab1, Rb1 to Rb6, h, and Xb1 represent the same meaning as in equation (2).

7. The polarizing element according to claim 1 or 2, wherein, The transmittance at each wavelength, obtained by overlapping two polarizing elements with their respective absorption axes parallel to each other, is such that the absolute value of the difference 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 absolute value of the difference 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 claim 1 or 2, wherein, According to JIS Z 8781-4:2013, when measuring the transmittance of natural light, the absolute values ​​of a* and b* in a single polarizing element are both below 1.

0.

9. The polarizing element according to claim 1 or 2, wherein, In a configuration where two polarizing elements are overlapped with their respective absorption axes parallel to each other, the a* value obtained when measuring transmittance using natural light, according to JIS Z 8781-4:2013, is -2.0 to 2.0, and the b* value is -2.0 to 3.

0.

10. The polarizing element according to claim 1 or 2, wherein, The transmittance of a single polarizing element after visual sensitivity correction is 35% to 65%, and the average transmittance in the wavelength band of 520 nm to 590 nm is 25% to 50% when two polarizing elements are overlapped in a manner in which their respective absorption axes are parallel to each other.

11. The polarizing element according to claim 1 or 2, wherein, In a configuration where two polarizing elements are overlapped in a manner in which their respective absorption axes are orthogonal to each other, the absolute value of the difference between the average transmittance of 420nm to 480nm and the average transmittance of 520nm to 590nm is 1.0% or less, and the absolute value of the difference between the average transmittance of 520nm to 590nm and the average transmittance of 600nm to 640nm is 1.0% or less.

12. The polarizing element according to claim 1 or 2, wherein, In a configuration in which two polarizing elements are overlapped in a manner in which their respective absorption axes are orthogonal to each other, the transmittance of any one of the orthogonal positions in the wavelength bands of 420nm to 480nm, 520nm to 590nm and 600nm to 640nm is less than 1%, or the polarization after visual sensitivity correction is more than 97%.

13. The polarizing element according to claim 1 or 2, wherein, When two polarizing elements are overlapped in a manner in which their respective absorption axes are orthogonal to each other, according to JIS Z 8781-4:2013, the absolute values ​​of a* and b* obtained when measuring the transmittance using natural light are both 2.0 or less.

14. The polarizing element according to claim 1 or 2, 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 having a transparent protective layer disposed on one or both sides of the polarizing element according to any one of claims 1 to 15.

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

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