Polarizing films, polarizing plates, and liquid crystal display devices containing azo compounds or salts thereof.

Abstract

The present invention pertains to a polarizing film containing an azo compound, represented by formula (1) below, or a salt thereof. (In formula (1): Ra1, Ra2, Ab1, and Ab2 are such that ring a or ring b has been substituted; one of Ra1 and Ra2 represents a hydroxy 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 sulfo group; one of Ab1 and Ab2 represents a sulfo group, a carboxy group, or an amino group that may contain a substituent, and the other is a substituent selected from the group consisting of a hydrogen atom, a sulfo group, a carboxy group, or an amino group that may have a substituent; Rb1 to Rb6 each independently represent a hydrogen atom, a C1 to C4 alkyl group, a C1 to C4 alkoxy group, a sulfo group, a C1 to C4 alkoxy group having a sulfo group, or an amino group that may have a substituent; h represents 0 or 1; Xb1 indicates an amino group that may have at least one substituent S, a phenylamino group that may have a substituent, a phenylazo group that may have a substituent, a naphthotriazole group that may have a substituent, or a benzoylamino group that may have a substituent; and the substituent S is selected from the group consisting of C1 to C4 alkyl groups, C1 to C4 alkoxy groups, sulfo groups, amino groups, C1 to C4 alkylamino groups, hydroxy groups, carboxy groups, and carboxyethylamino groups, and is different from Ra1, Ra2, Ab1, and Ab2.

Description

Technical Field

[0001] The present invention relates to a polarizing film, a polarizing plate, and a liquid crystal display device containing a novel azo compound or a salt thereof.

Background Art

[0002] A polarizing plate having a light transmission / blocking function is a basic component of a display device (display) such as a liquid crystal display (Liquid Crystal Display: LCD) together with a liquid crystal having a light switching function. The application fields of this LCD include small devices such as calculators and watches in the early days, and also include notebook computers, word processors, liquid crystal projectors, liquid crystal TVs, car navigation systems, and indoor and outdoor measuring instruments. In addition, it can be applied to lenses having a polarizing function, and has been applied to sunglasses with improved visibility and polarizing glasses corresponding to 3D TVs in recent years. Since the uses of such polarizing plates are widely spread, the operating conditions are also used under a wide range of conditions from low temperature to high temperature, low humidity to high humidity, and low light amount to high light amount. Therefore, a polarizing plate having high polarizing performance and high durability is required.

[0003] Currently, polarizing plates are manufactured by dyeing or containing iodine or a dichroic dye in a film of polyvinyl alcohol or its derivative, stretching and orienting it, or generating polyene by dehydrochlorination of a polyvinyl chloride film or dehydration of a polyvinyl alcohol-based film and orienting it. These are substances that greatly affect the polarizing characteristics and durability of polarizing plates. The iodine-based polarizing film produced using iodine is excellent in polarizing performance, but is weak against water and heat, and has a problem in its durability when used for a long time under high temperature and high humidity conditions. In order to improve the durability, methods such as treating with formalin or an aqueous solution containing boric acid, or using a polymer film with low moisture permeability as a protective film have been considered, but the effects are not sufficient.

[0004] On the other hand, while dye-based polarizing films made using dyes have superior moisture resistance and heat resistance compared to iodine-based polarizing films, their polarization performance is generally insufficient. Dye-based neutral gray polarizing plates are generally manufactured by combining multiple types of dyes, but the polarization performance of dye-based neutral gray polarizing plates is insufficient, and the development of dichroic dyes with good polarization performance for each color used was necessary.

[0005] Examples of dye-based polarizing films mentioned above include those made using water-soluble azo compounds described in Patent Documents 1 to 3, but they have not yet achieved sufficient polarization characteristics, and further improvements in performance are needed. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 05-053014 [Patent Document 2] Japanese Patent Application Publication No. 05-295282 [Patent Document 3] Japanese Patent Application Publication No. 09-230142 [Patent Document 4] Japanese Patent Application Publication No. 11-218611 [Patent Document 5] Japanese Patent Publication No. 2001-33627 [Patent Document 6] Japanese Patent Publication No. 2009-132794 [Patent Document 7] Japanese Patent Publication No. 2001-240762 [Patent Document 8] Japanese Patent Publication No. 2001-108828 [Patent Document 9] Japanese Patent Application Publication No. 156759 / 1983 [Non-patent literature]

[0007] [Non-Patent Document 1] Dye Chemistry; by Yutaka Hosoda, Gihodo Publishing, 1957, 621 pages. [Non-Patent Document 2] Applications of Functional Dyes (CMC Publishing Co., Ltd., 1st edition, supervised by Masahiro Irie, pp. 98-100) [Overview of the project] [Problems that the invention aims to solve]

[0008] One object of the present invention is to provide a high-performance polarizing film and polarizing plate having excellent polarization performance. Another object of the present invention is to provide a neutral gray polarizing plate with orthogonal color bleeding in the wavelength range of the visible light region. Yet another object of the present invention is to provide a high-performance polarizing plate having excellent polarization performance and durability (heat resistance, moisture resistance, or light resistance). [Means for solving the problem]

[0009] As a result of diligent research to achieve this objective, the inventors have discovered that polarizing films and polarizing plates containing specific azo compounds and their salts possess excellent polarization performance and durability.

[0010] In other words, the present invention relates to, but is not limited to, the following [1] to

[12] . [1] A polarizing film containing an azo compound represented by the following formula (1) or a salt thereof. [ka] (In formula (1), Ra1, Ra2, Ab1, and Ab2 are substituted with either ring a or ring b, and one of Ra1 and Ra2 is a hydroxyl group, while the other is a hydrogen atom, a hydroxyl group) C baserepresents a C1-4 alkoxy group or a C1-4 alkoxy group having a C1-4 alkoxy group or a sulfo group, either Ab1 or Ab2 represents a sulfo group, a carboxy group, or an amino group which may have a substituent, and the other is a substituent selected from the group consisting of a hydrogen atom, a sulfo group, a carboxy group, or an amino group which may have a substituent, Rb1 to Rb6 each independently represent a hydrogen atom, a C1-4 alkyl group, a C1-4 alkoxy group, a sulfo group, a C1-4 alkoxy group having a sulfo group, or an amino group which may have a substituent, h represents 0 or 1, Xb1 represents an amino group which may have at least one substituent S, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a naphthotriazole group which may have a substituent, or a benzoylamino group which may have a substituent, the substituent S (when there are plural, each independently) is further selected from the group consisting of a C1-4 alkyl group which may have a substituent, a C1-4 alkoxy group, a sulfo group, an amino group, a C1-4 alkylamino group, a hydroxy group, a carboxy group, and a carboxyethylamino group, and is different from the Ra1, Ra2, Ab1, and Ab2 mentioned above.) [2] The polarizing film according to the preceding item [1], wherein the azo compound represented by the formula (1) or a salt thereof is an azo compound represented by the following formula (2) or a salt thereof.

Chemical formula

Chemical formula

[10] The polarizing film according to any one of the preceding items [7] to [9], having a neutral gray color.

[11] A polarizing plate comprising a transparent protective film provided on one or both sides of the polarizing film described in any one of the preceding paragraphs [7] to

[10] .

[12] A display device comprising a polarizing film as described in any one of the preceding paragraphs [1] to

[10] or a polarizing plate as described in the preceding paragraph

[11] . [Effects of the Invention]

[0011] The polarizing film and polarizing plate of the present invention have excellent polarization performance. In one embodiment, the polarizing plate having a neutral gray color of the present invention exhibits high-performance achromaticity without color bleeding at orthogonal positions in the wavelength range of the visible light region. In one embodiment, the polarizing film and polarizing plate of the present invention have excellent polarization performance (transmittance, contrast) and durability (moisture resistance, heat resistance, light resistance). [Modes for carrying out the invention]

[0012] In this specification and in the claims, unless it clearly refers to a free form, “azo compound or salt thereof” may also be simply referred to as “azo compound.” In this specification and in the claims, the term "substituent" may include a hydrogen atom, and therefore, for convenience, a hydrogen atom may also be described as a "substituent." "May have a substituent" means that it also includes cases where there is no substituent. For example, "a phenyl group that may have a substituent" includes an unsubstituted, simple phenyl group and a phenyl group with a substituent. Furthermore, unless otherwise specified, "lower" in the lower alkyl group, lower alkoxy group, etc., in this application indicates that the number of carbon atoms is 1 to 4 (C1 to 4), preferably 1 to 3 (C1 to 3).

[0013] <Azo compounds or their salts> The polarizing film of the present invention contains an azo compound represented by the following formula (1) or a salt thereof.

[0014] [ka]

[0015] (In formula (1), Ra1, Ra2, Ab1, and Ab2 are substituted with either ring a or ring b, and one of Ra1 and Ra2 is a hydroxyl group, while the other is a hydrogen atom, a hydroxyl group) C base Alternatively, it represents a C1-4 alkoxy group or a C1-4 alkoxy group having a sulfo group, and either Ab1 or Ab2 represents a sulfo group, a carboxyl group, or an optionally substituted amino group, while the other is a substituent selected from the group consisting of a hydrogen atom, a sulfo group, a carboxyl group, or an optionally substituted amino group, and Rb1-Rb6 each independently represents a hydrogen atom, a C1-4 alkyl group, a C1-4 alkoxy group, a sulfo group, a C1-4 alkoxy group having a sulfo group, or an optionally substituted amino group, and h represents 0 or 1, and Xb1 has a small substituent S The amino group may be absent or present as one, the phenylamino group may be substituted, the phenylazo group may be substituted, the naphthotriazole group may be substituted, or the benzoylamino group may be substituted, and the substituent S (if there are multiple substituents, each independently) is selected from the group consisting of a C1-4 alkyl group, a C1-4 alkoxy group, a sulfo group, an amino group, a C1-4 alkylamino group, a hydroxyl group, a carboxyl group, and a carboxyethylamino group, which may further be substituted, and is different from Ra1, Ra2, Ab1, and Ab2. The amino group which may have substituents that can be selected as Rb1 to Rb6 is preferably an unsubstituted amino group or an amino group having one or two substituents (C1 to C4 alkyl group, acetyl group). The amino group which may have substituents S is preferably an unsubstituted amino group, an amino group having one or two C1-4 alkyl groups which may have substituents (hydroxyl group, methoxy group, ethoxy group, amino group, carboxyl group, sulfo group, phenyl group), and more preferably an amino group having one or two hydrogen atoms and methyl groups. The phenylamino group which may have substituents is preferably a phenylamino group having one or two substituents selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxy group, a sulfo group, a carboxyl group, an amino group, and a lower alkylamino group, and more preferably a phenylamino group having one or two substituents selected from the group consisting of a hydrogen atom, a methyl group, a methoxy group, a sulfo group, a carboxyl group, and an amino group. The phenylazo group which may have substituents is preferably a phenylazo group having one to three substituents selected from the group consisting of a hydrogen atom, a hydroxyl group, a C1-4 alkyl group, a C1-4 alkoxy group, an amino group, a hydroxyl group, and a carboxyethylamino group. The optionally substituted benzoylamino group is preferably a benzoylamino group having one substituent selected from the group consisting of a hydrogen atom, a hydroxyl group, an amino group, and a carboxyethylamino group. The optionally substituted naphthotriazole group is unsubstituted or, preferably, has one or two substituents selected from the group consisting of a sulfo group, an amino group, and a carboxyl group, and more preferably has one or two sulfo groups as substituents. The substitution positions of the substituents that the phenylamino group, phenylazo group, and benzoylamino group may have are not particularly limited, but it is preferable that one of the substituents is at the p position relative to the respective amino group, azo group, or amide group. The substitution position of Xb1 is preferably at the 6th or 7th position, and more preferably at the 6th position, when the position of the hydroxyl group of the substituted naphthyl group is considered to be at the 1st position.

[0016] In formula (1), "C1-4 alkyl group" can be, for example, a linear alkyl group such as a methyl group, ethyl group, n-propyl group, or n-butyl group; a segmented alkyl group such as a sec-butyl group or tert-butyl group; or an unsaturated hydrocarbon group such as a vinyl group.

[0017] Examples of the "C1-4 alkoxy group" in formula (1) include a methoxy group, an ethoxy group, a propoxy group, an n-butoxy group, a sec-butoxy group, a tert-butoxy group, and the like.

[0018] When the azo compound or salt thereof represented by formula (1) is the azo compound or salt thereof represented by formula (2) below, it is preferable because it can provide a polarizing film with higher transmittance and higher polarization. Furthermore, it is preferable because it can further improve transmittance in the parallel position of 550 nm to 700 nm and provide a polarizing film with higher polarization. More preferably, the azo compound or salt thereof represented by formula (1) is the compound or salt thereof represented by formula (3), even more preferably the compound or salt thereof represented by formula (4), even more preferably the compound or salt thereof represented by formula (5), and particularly preferably the azo compound or salt thereof represented by formula (6).

[0019] [ka] (In equation (2), Ra1, Ra2, Ab1, Ab2, Rb1~Rb6, h, and Xb1 have the same meanings as in equation (1).)

[0020] [ka] (In equation (3) above, Ra1, Ra2, Ab1, Ab2, Rb1~Rb6, h, and Xb1 each have the same meaning as in equation (1).)

[0021] [ka] (In equation (4) above, Ra1, Ra2, Ab1, Ab2, Rb1~Rb6, h, and Xb1 each have the same meaning as in equation (1).)

[0022] [ka] (In equation (5) above, Ra1, Ab1, Rb1~Rb6, h, and Xb1 each have the same meaning as in equation (1).)

[0023] [ka] (In equation (6) above, Ra1, Ab1, Rb1~Rb6, h, and Xb1 each have the same meaning as in equation (1).)

[0024] The azo compound represented by formula (1) above, or a salt thereof, can be easily produced by known diazotization and coupling in accordance with the conventional method for producing azo dyes as described in Non-Patent Document 1. The synthesis method is illustrated using the azo compound represented by formula (2) when h=0 as an example.

[0025] First, the amines represented by formula (A) are diazotized by a known method as described in Non-Patent Document 1, and then subjected to primary coupling with the anilines of formula (B) below to obtain the monoazoamino compound represented by formula (C) below.

[0026] [ka] (In equations (A) to (C), Ra1, Ra2, Ab1, Ab2, Rb1, and Rb2 each represent the same meaning as in equation (1).)

[0027] Next, this monoazoamino compound (C) is diazotized by a known method as described in Non-Patent Document 1, and then secondary coupling with an aniline of the following formula (D) to obtain a disazoamino compound represented by the following formula (E).

[0028] [ka] (In equations (D) and (E), Ra1, Ra2, Ab1, Ab2, and Rb1-Rb4 have the same meanings as in equation (1).)

[0029] The azo compound of formula (2) is obtained by diazotizing formula (E) using a known method as described in Non-Patent Document 1 and coupling it with naphthols represented by the following formula (F).

[0030] [ka] (In equation (F), Xb1 has the same meaning as in equation (1).)

[0031] In the above reaction, the diazotization step is carried out either by a forward method, in which a nitrite such as sodium nitrite is mixed with an aqueous solution of the diazo component containing a mineral acid such as hydrochloric acid or sulfuric acid, or by a saponifying solution, or by a reverse method, in which a nitrite is added to a neutral or weakly alkaline aqueous solution of the diazo component, and then this is mixed with the mineral acid. The temperature for diazotization is suitable at -10 to 40°C. Furthermore, the coupling step with anilines is preferably carried out by mixing an acidic aqueous solution such as hydrochloric acid or acetic acid with the above-mentioned diazo solutions, under acidic conditions with a temperature of -10 to 40°C and a pH of 2 to 7.

[0032] The monoazo and disazo compounds obtained by coupling can be used as is, precipitated by acid precipitation or salting out and filtered, or proceeded to the next step as a solution or turbidity. If the monoazo and disazo compounds obtained by coupling are sparingly soluble and form a turbidity, they can be filtered and used as a press cake in the next coupling step.

[0033] The coupling reaction between the diazotized disazo compound and naphthols represented by formula (F) is preferably carried out under neutral to alkaline conditions at a temperature of -10 to 40°C and a pH of 7 to 10. After the reaction is complete, the reaction product is precipitated by salting out and removed by filtration. If further purification is required, the salting out process can be repeated or the product can be precipitated from water using an organic solvent. Examples of organic solvents used for purification include water-soluble organic solvents such as alcohols like methanol and ethanol, and ketones like acetone.

[0034] The starting material for synthesizing the azo compound represented by formula (1) or its salt is a substituted naphthylamine compound represented by formula (A). Examples of naphthylamines of formula (A) include 2-amino-1-hydroxynaphthalene-6-sulfonic acid, 3-amino-1-hydroxynaphthalene-6-sulfonic acid, 2-amino-8-hydroxynaphthalene-6-sulfonic acid, 3-amino-8-hydroxynaphthalene-6-sulfonic acid, 2-amino-1,8-dihydroxynaphthalene-6-sulfonic acid, 3-amino-1,8-dihydroxynaphthalene-6-sulfonic acid, 2-amino-1,8-dihydroxynaphthalene-3-sulfonic acid, 2-amino-1,8-dihydroxynaphthalene-3,6-disulfonic acid, 2-amino-1-methoxy-8-hydroxynaphthalene-6-sulfonic acid, and 3-amino-1-methoxy-8-hydroxyna Examples include, but are not limited to, phthalene-6-sulfonic acid, 2-amino-1-hydroxy-8-methoxynaphthalene-6-sulfonic acid, 3-amino-1-hydroxy-8-methoxynaphthalene-6-sulfonic acid, 2-amino-1-hydroxy-8-(3-sulfopropoxy)naphthalene-3-sulfonic acid, 2-amino-1-hydroxy-8-(4-sulfobutoxy)naphthalene-3-sulfonic acid, 2-amino-1-(3-sulfopropoxy)-8-hydroxynaphthalene-3-sulfonic acid, 2-amino-1-(4-sulfobutoxy)-8-hydroxynaphthalene-3-sulfonic acid, and 2-amino-1,8-dihydroxynaphthalene-6-aminomethyl-3-disulfonic acid. Preferably, it is 2-amino-1,8-dihydroxynaphthalene-6-sulfonic acid, 2-amino-1,8-dihydroxynaphthalene-3-sulfonic acid, 2-amino-1,8-dihydroxynaphthalene-3,6-disulfonic acid, 2-amino-1-methoxy-8-hydroxynaphthalene-6-sulfonic acid, or 2-amino-1-hydroxy-8-methoxynaphthalene-6-sulfonic acid.

[0035] In formula (1), the anilines having substituents (Rb1 to Rb6) that are primary and secondary coupling components when h is 0, or primary to tertiary coupling components when h is 1, are, for example, aniline, 2-methylaniline, 2-ethylaniline, 2-propylaniline, 2-butylaniline, 3-methylaniline, 3-ethylaniline, 3-propylaniline, 3-butylaniline, 2,5-dimethylaniline, 2,5-diethylaniline, 2-methoxyaniline, 2-ethoxyaniline, 2-propoxyaniline, 2-butoxyaniline, 3-methoxyaniline, 3-ethoxyaniline, 3-propoxyaniline, 3-butoxyaniline, 2-methoxy-5-methylaniline, 2,5-dimethoxyaniline, 3,5-dimethylaniline, 2,6-dimethylaniline, 3,5-Dimethoxyaniline, 3-(2-amino-4-methylphenoxy)propane-1-sulfonic acid, 3-(2-aminophenoxy)propane-1-sulfonic acid, 4-(2-amino-4-methylphenoxy)butane-1-sulfonic acid, 4-(2-aminophenoxy)butane-1-sulfonic acid, 2-(2-amino-4-methylphenoxy)ethane-1-sulfonic acid, 2-(2-aminophenoxy)ethane-1-sulfonic acid, 3-(3 -amino-4-methylphenoxy)propane-1-sulfonic acid, 3-(3-aminophenoxy)propane-1-sulfonic acid, 4-(3-amino-4-methylphenoxy)butane-1-sulfonic acid, 4-(3-aminophenoxy)butane-1-sulfonic acid, 2-(3-amino-4-methylphenoxy)ethane-1-sulfonic acid, 2-(3-aminophenoxy)ethane-1-sulfonic acid, 3-(2-amino-4-methoxyphenoxy) Propane-1-sulfonic acid, 4-(2-amino-4-methoxyphenoxy)butane-1-sulfonic acid, 2-(2-amino-4-methoxyphenoxy)ethane-1-sulfonic acid, 3-(3-amino-4-methoxyphenoxy)propane-1-sulfonic acid, 4-(3-amino-4-methoxyphenoxy)butane-1-sulfonic acid, 2-(3-amino-4-methoxyphenoxy)ethane-1-sulfonic acid, 3-(2-amino-4-ethoxy Examples include cyphenoxy)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 the ω-methanesulfone group.

[0036] Examples of naphthols having Xb1, which is the tertiary coupling component when h is 0 or the quaternary coupling component when h is 1 in formula (1), include, but are not limited to, 6-amino-3-sulfonic acid-1-naphthol, 6-methylamino-3-sulfonic acid-1-naphthol, 6-phenylamino-3-sulfonic acid-1-naphthol, 6-(4-methoxy-phenylamino)-3-sulfonic acid-1-naphthol, 6-(3,5-naphthotriazole)-3-sulfonic acid-1-naphthol, 6-benzoylamino-3-sulfonic acid-1-naphthol, and 6-(4′-aminobenzoyl)amino-3-sulfonic acid-1-naphthol.

[0037] Specific examples of azo compounds or salts thereof represented by formula (1) are given below. Note that azo compounds are expressed in the form of free acids.

[0038] [ka]

[0039] [ka]

[0040] [ka]

[0041] [ka]

[0042] [ka]

[0043] [ka]

[0044] [ka]

[0045] [ka]

[0046] [ka]

[0047] The azo compounds represented by formula (1) may be in the form of free acids or salts, or they may be salts 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, and triethanolammonium ions. More specifically, for example, in the case of free acids, it represents sulfonic acid (-SO3H), in the case of sodium ions, it represents sodium sulfonate (-SO3Na), and in the case of ammonium ions, it represents ammonium sulfonate (-SO3NH4).

[0048] <Polarizing film> The polarizing film of the present invention contains an azo compound represented by formula (1) or a salt thereof as a dichroic dye. The polarizing film can be a neutral gray polarizing film or a color polarizing film, and is preferably a neutral gray polarizing film. Here, "neutral gray" means that when two polarizing films are superimposed so that their orientation directions are orthogonal to each other (hereinafter also referred to as "orthogonal position"), there is little light leakage (color leakage) of specific wavelengths in the visible light wavelength range.

[0049] The polarizing film of the present invention contains one or more azo compounds represented by formula (1) or salts thereof as dichroic dyes, and may optionally further contain one or more other organic dyes other than the azo compounds represented by formula (1). The other organic dyes are not particularly limited, but dyes that have absorption characteristics in a wavelength region different from the absorption wavelength region of the azo compound represented by formula (1) or salts thereof, and that have high dichroism are preferred. Other organic dyes include, for example, CI Direct Yellow 12, CI Direct Yellow 28, CI Direct Yellow 44, CI Direct Orange 26, CI Direct Orange 39, CI Direct Orange 71, CI Direct Orange 107, CI Direct Red 2, CI Direct Red 31, CI Direct Red 79, CI Direct Red 81, CI Direct Red 247, CI Direct Green 80, and CI Direct Green 59, as well as the dyes described in Non-Patent Literature 2. However, depending on the purpose, it is preferable to use dyes developed for polarizing plates, such as those described in Patent Literature 4 to 9. These organic dyes are used as free acids, alkali metal salts (e.g., Na salts, K salts, Li salts), ammonium salts, or salts of amines.

[0050] When other organic dyes are used in combination, the types of organic dyes used will differ depending on whether the target polarizing film is a neutral gray polarizing film, a color polarizing film for liquid crystal projectors, or other color polarizing films. The mixing ratio is not particularly limited, but generally, it is preferable to use a total of at least one of the other organic dyes in the range of 0.01 to 100 parts by mass per 1 part by mass of the azo compound of formula (1) or its salt, and more preferably in the range of 0.1 to 10 parts by mass.

[0051] When the target polarizing film is a neutral gray polarizing film, the types and proportions of other organic dyes used in combination are adjusted so that the resulting polarizing film has minimal color leakage in the visible light wavelength range.

[0052] When the target polarizing film is a color polarizing film, the types and proportions of other organic dyes used in combination are adjusted so that the resulting polarizing film has a high single-plate average light transmittance in a specific wavelength range and a low average light transmittance at orthogonal positions. For example, the single-plate average light transmittance is 39% or higher and the average light transmittance at orthogonal positions is 0.4% or lower in a specific wavelength range.

[0053] The polarizing film of the present invention can be produced by incorporating a dichroic dye, which comprises an azo compound represented by formula (1) or a salt thereof, and optionally other dyes, into a polarizing film substrate (also simply referred to as "substrate") in a known manner and oriented it.

[0054] The substrate is preferably a polymer film, and more preferably a film made of polyvinyl alcohol resin or a derivative thereof. Specific examples of the substrate include polyvinyl alcohol resin or polyvinyl alcohol resin modified with olefins such as ethylene and propylene, or unsaturated carboxylic acids such as crotonic acid, acrylic acid, methacrylic acid, and maleic acid. As the substrate, a film made of polyvinyl alcohol resin or a derivative thereof is preferably used from the viewpoint of dye adsorption and orientation. The thickness of the substrate is usually 10 to 100 μm, preferably about 20 to 80 μm.

[0055] When the substrate is a polymer film, a method of dyeing the polymer film is usually employed to incorporate the azo compound of formula (1) or a salt thereof. Dyeing is carried out, for example, as follows: First, a dye bath is prepared by dissolving the azo compound represented by formula (1) or a salt thereof, and optionally other organic dyes, in water. The dye concentration in the dye bath is not particularly limited, but is usually selected from a range of about 0.001 to 10% by mass. Dyeing aids may also be used if necessary; for example, it is preferable to use Glauber's salt at a concentration of about 0.1 to 10% by mass. The polymer film can be immersed in the dye bath prepared in this way for, for example, 1 to 10 minutes to perform dyeing. The dyeing temperature is preferably about 30 to 80°C.

[0056] The orientation of the azo compound represented by formula (1) or its salt is performed by stretching a polymer film dyed with a dichroic dye. The stretching ratio is generally 2 to 9 times, preferably 3 to 8 times, and more preferably 4 to 7 times. Any known method may be used for stretching, such as a wet method or a dry method. Stretching of the polymer film may be performed before dyeing, if necessary. In this case, the orientation of the water-soluble dye is performed at the time of dyeing. The polymer film containing the water-soluble dye and oriented is then subjected to post-treatment such as boric acid treatment by a known method as needed. Such post-treatment is performed to improve the light transmittance and polarization degree of the polarizing film. The conditions for boric acid treatment vary depending on the type of polymer film and dye used, but generally, the boric acid concentration of the boric acid aqueous solution is, for example, 0.1 to 15% by mass, preferably 1 to 10% by mass, the treatment temperature is 30 to 80°C, preferably 40 to 75°C, and the treatment is performed by immersion for 0.5 to 10 minutes. Furthermore, if necessary, a fixation treatment may be carried out in conjunction with an aqueous solution containing a cationic polymer compound.

[0057] Applications of the polarizing film of the present invention include, for example, liquid crystal projectors, calculators, watches, laptop computers, word processors, liquid crystal televisions, car navigation systems, indoor and outdoor measuring instruments and displays, as well as lenses and eyeglasses. The polarizing film made using the dye of the present invention (hereinafter also referred to as "dye-based polarizing film") has high polarization performance comparable to that of a polarizing film made using iodine (hereinafter also referred to as "iodine-based polarizing film"), and also has excellent durability. For this reason, it is particularly suitable for applications requiring high polarization performance and durability, such as various liquid crystal displays for automotive and outdoor displays (for example, for industrial instrument displays and wearable applications), and liquid crystal projectors.

[0058] <Polarizing plate> The polarizing plate of the present invention (hereinafter also referred to as the "dye-based polarizing plate") can be obtained by laminating a transparent protective film to one or both sides of a polarizing film. The polarizing plate of the present invention has excellent polarization performance and durability (moisture resistance, heat resistance, and light resistance). As the material for forming the transparent protective film, a material with excellent optical transparency and mechanical strength is preferred, and examples include cellulose acetate film, acrylic film, fluorine-based film such as tetrafluoroethylene / hexafluoropropylene copolymer, polyester resin, polyolefin resin, or polyamide resin film. The transparent protective film is preferably a triacetylcellulose (TAC) film or a cycloolefin film. The thickness of the protective film is usually preferably 40 to 200 μm.

[0059] An adhesive can be used to bond the polarizing film and the protective film of the present invention. Examples of adhesives that can be used include polyvinyl alcohol-based adhesives, urethane emulsion-based adhesives, acrylic-based adhesives, and polyester-isocyanate-based adhesives, with polyvinyl alcohol-based adhesives being preferred.

[0060] A transparent protective layer may be further provided on the surface of the polarizing plate of the present invention. Examples of the transparent protective layer include acrylic or polysiloxane-based hard coat layers and urethane-based protective layers. Furthermore, in order to further improve the single-sheet light transmittance, it is preferable to provide an anti-reflective layer (AR layer) on top of this transparent protective layer. The AR layer can be formed by vapor deposition or sputtering of a substance such as silicon dioxide or titanium dioxide, or by thinly coating a fluorine-based substance. It is preferable for the dye-based polarizing plate to further include a support. The dye-based polarizing plate can also be used as an elliptical polarizing plate by attaching a phase difference plate to its surface.

[0061] The polarizing plate of the present invention may be either a neutral gray polarizing plate or a color polarizing plate, depending on the application.

[0062] The neutral gray polarizing plate of the present invention has a neutral color, exhibits minimal color leakage in orthogonal positions within the polarization region of the visible light spectrum, has excellent polarization performance, and further suppresses discoloration and degradation of polarization performance even under high temperature and high humidity conditions, resulting in high durability, making it suitable for automotive or outdoor display applications.

[0063] Neutral gray polarizing plates for automotive or outdoor display applications are preferably polarizing plates with an AR layer, which is provided on a polarizing plate composed of the polarizing film and transparent protective film of the present invention, in order to further improve the light transmittance of the polarizing plate alone. More preferably, polarizing plates with an AR layer and support are provided, in which both the AR layer and a support such as a transparent resin are attached. The AR layer can be provided on one or both sides of the polarizing plate. The support is preferably provided on one side of the polarizing plate, and may be provided directly on the polarizing plate, or the polarizing plate with an AR layer (AR layer / polarizing plate / AR layer) may be provided on the support. It is preferable that the polarizing plate with an AR layer and support is provided in the order of AR layer / polarizing plate / AR layer / support. The support is preferably one that has a flat surface for attaching the polarizing plate, and is preferably a transparent substrate because it is for optical applications. Transparent substrates can be broadly classified into inorganic and organic substrates. Inorganic substrates include soda glass, borosilicate glass, quartz substrates, sapphire substrates, and spinel substrates, while organic substrates include acrylic, polycarbonate, polyethylene terephthalate, polyethylene naphthalate, and cycloolefin polymers. Organic substrates are preferred. The thickness and size of the transparent substrate can be any desired size.

[0064] Color polarizing plates offer excellent polarization performance and do not discolor or degrade in polarization performance even under high temperature and high humidity conditions, making them suitable for liquid crystal projectors and display devices such as those used in vehicles and outdoors.

[0065] Color polarizing plates for liquid crystal projectors have brightness and excellent polarization performance, and in the required wavelength range of the polarizing plate (A. When using an ultra-high pressure mercury lamp: 420-500nm for the blue channel, 500-580nm for the green channel, 600-680nm for the red channel; B. When using a three-primary-color LED lamp: 430-450nm for the blue channel, 520-535nm for the green channel, 620-635nm for the red channel), the average light transmittance of a single plate is 39% or more, and the average light transmittance of orthogonal positions is 0.4% or less. More preferably, the average light transmittance of a single plate in the required wavelength range of the polarizing plate is 41% or more, and the average light transmittance of orthogonal positions is 0.3% or less, more preferably 0.2% or less. Even more preferably, the average light transmittance of a single plate in the required wavelength range of the polarizing plate is 42% or more, and the average light transmittance of orthogonal positions is 0.1% or less.

[0066] The average light transmittance of a single plate is the average value of the light transmittance in a specific wavelength range when natural light is incident on a single polarizing plate (hereinafter also simply referred to as "polarizing plate") that does not have an AR layer or a support such as a transparent glass plate. The average light transmittance of orthogonal plates is the average value of the light transmittance in a specific wavelength range when natural light is incident on two polarizing plates that are superimposed so that their orientation directions are orthogonal to each other.

[0067] The polarizing film used in automotive or outdoor display color polarizers may, similar to neutral gray polarizers, be a dye-based polarizer with a protective layer or AR layer and a support as needed. A color polarizer with a support can be obtained, for example, by applying a transparent adhesive to the flat surface of the support and then attaching the dye-based polarizer to this applied surface. Alternatively, a transparent adhesive may be applied to the dye-based polarizer and then the support may be attached to this applied surface. The adhesive is preferably an acrylic ester type. When using this dye-based polarizer as an elliptical polarizer, it is common to attach the phase difference plate side to the support in a stacking order of dye-based polarizer / phase difference plate / support, but it is also possible to attach the polarizer side to the support in a stacking order of phase difference plate / polarizer / support.

[0068] <Display device> The display device of the present invention comprises a polarizing film or polarizing plate of the present invention. Examples of display devices include liquid crystal display devices and organic electronic display devices, and are used for displays in calculators, watches, laptop computers, word processors, liquid crystal televisions, car navigation systems, and indoor and outdoor measuring instruments and displays. In particular, it is suitable for use in various displays that require high polarization performance and durability, such as in-vehicle or outdoor displays (for example, for industrial instrument displays and wearable applications). The dye-based polarizing film or dye-based polarizing plate provided in the display device is preferably neutral gray.

[0069] In liquid crystal display devices, a dye-based polarizer is placed on either the incident side or the output side of the liquid crystal cell, or on both sides. The dye-based polarizer may or may not be in contact with the liquid crystal cell, but from the viewpoint of durability, it is preferable that it is not in contact. When the dye-based polarizer is in contact with the liquid crystal cell on the output side of the liquid crystal cell, the liquid crystal cell can be used as a support for the dye-based polarizer. When the dye-based polarizer is not in contact with the liquid crystal cell, it is preferable to use a dye-based polarizer with a support other than the liquid crystal cell. Furthermore, from the viewpoint of durability, it is preferable to place the dye-based polarizer on both the incident and output sides of the liquid crystal cell, and it is even preferable to place the polarizer surface of the dye-based polarizer on the liquid crystal cell side and the support surface on the light source side. The incident side of the liquid crystal cell is the light source side, and the opposite side is called the output side.

[0070] The liquid crystal cell provided in the liquid crystal display device is preferably an active matrix type, formed by sealing liquid crystal between a transparent substrate on which electrodes and TFTs are formed and a transparent substrate on which counter electrodes are formed. Light emitted from a light source such as a cold cathode lamp or white LED passes through a dye-based polarizing plate, then through the liquid crystal cell, a color filter, and another dye-based polarizing plate, and is projected onto the display screen.

[0071] Liquid crystal display devices are highly reliable because dye-based polarizing plates possess brightness, excellent polarization performance, and lightfastness, making them less susceptible to discoloration or degradation of polarization performance even in high-temperature and high-humidity conditions such as inside cars or outdoors. [Examples]

[0072] The present invention will be described in more detail below with reference to examples, but these are illustrative and do not limit the invention in any way. Unless otherwise specified, percentages and parts in the examples are by mass.

[0073] [Example S1] (Process 1) 15.0 parts of commercially available N-acetyl-1,4-phenylenediamine were 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 the mixture was stirred for 1 hour to diazotize it. 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. To this solution, the previously obtained diazo solution was added dropwise, maintaining the pH at 6.5 to 8.0, and stirred to complete the coupling reaction. Subsequently, the resulting reaction solution was stirred at 90 to 99°C for 5 hours at a pH of 0.5 or lower (e.g., 0.01 to 0.5) to carry out a hydrolysis reaction. The precipitated solid was filtered off to obtain 150 parts of a wet cake of the monoazo compound shown in formula (7).

[0074] [ka]

[0075] (Process 2) 150 parts of the wet cake of the monoazo compound represented by formula (7) were added to 300 parts of water and stirred to suspend the compound. The pH was adjusted to 9.0 using 25% sodium hydroxide, and 17.3 parts of 40% sodium nitrite aqueous solution were added. The resulting aqueous solution was added dropwise to a mixture of 200 parts 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 mixture was stirred for 8 hours while maintaining the pH at 1.5 to 4.0 with 15% sodium carbonate aqueous solution to complete the coupling reaction. After that, the mixture was salted out with sodium chloride and filtered to obtain 200 parts of the wet cake of the disazo compound represented by formula (8).

[0076] [ka]

[0077] (Step 3) 200 parts of the wet cake of the disazo compound represented by the obtained formula (8) were added to 500 parts of water, stirred, and suspended. The pH was adjusted to 9.0 using 25% sodium hydroxide, and 17.3 parts of 40% sodium nitrite aqueous solution were added. The resulting suspension was added dropwise to a mixture of 100 parts water and 42 parts 35% hydrochloric acid to prepare the diazo solution. Next, 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid were added to 300 parts of water and dissolved in 25% sodium hydroxide aqueous solution to make it weakly alkaline. The previously obtained diazo solution was added dropwise to this solution, maintaining the pH at 6.5-8.0, and stirred to complete the coupling reaction. After that, the mixture was salted out with sodium chloride, filtered, and dried to obtain 8.0 parts of the azo compound shown in Compound Example 1-8.

[0078] [Example S2] Except for replacing 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid in step 3 of Example S1 with 34.5 parts of 1-hydroxy-6-(4-methoxyphenylamino)-3-naphthalenesulfonic acid, 8.0 parts of the azo compound shown in Compound Examples 1-10 was obtained in the same manner as in Example S1.

[0079] [Example S3] Except for replacing 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid in step 3 of Example S1 with 37.5 parts of 1-hydroxy-6-(2,4-dimethoxyphenylamino)-3-naphthalenesulfonic acid, 8.9 parts of the azo compound shown in Compound Example 1-14 was obtained in the same manner as in Example S1.

[0080] [Example S4] Except for replacing 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid with 35.8 parts of 1-hydroxy-6-(4-aminobenzoylamino)-3-naphthalenesulfonic acid in step 3 of Example S1, 11.0 parts of the azo compound shown in Compound Example 1-31 was obtained in the same manner as in Example S1.

[0081] [Example S5] (Process 1) In Step 1 of Example S1, 150 parts of a wet cake of the monoazo compound represented by formula (7) were added to 300 parts of water and stirred to suspend the compound. The pH was adjusted to 9.0 using 25% sodium hydroxide, and then 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. 10.7 parts of 3-methylaniline were added to the resulting diazo solution, and the mixture was stirred for 8 hours while maintaining the pH at 1.5 to 4.0 with a 15% sodium carbonate aqueous solution to complete the coupling reaction. After that, the mixture was salted out with sodium chloride and then filtered to obtain 200 parts of a wet cake of the disazo compound represented by formula (9).

[0082] [ka]

[0083] (Process 2) 150 parts of the wet cake of the monoazo compound represented by formula (9) were added to 300 parts of water, stirred, and suspended. The pH was adjusted to 9.0 using 25% sodium hydroxide, and 17.3 parts of 40% 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. 13.7 parts of 2-methoxy-5-methylaniline were added to the resulting diazo solution, and the mixture was stirred for 8 hours while maintaining the pH at 1.5 to 4.0 with 15% sodium carbonate aqueous solution to complete the coupling reaction. After that, the mixture was salted out with sodium chloride and filtered to obtain 200 parts of the wet cake of the trisazo compound represented by formula (10).

[0084] [ka]

[0085] (Step 3) 200 parts of the wet cake of the trisazo compound represented by the obtained formula (10) were added to 500 parts of water, stirred, and suspended. The pH was adjusted to 9.0 using 25% sodium hydroxide, and 17.3 parts of 40% sodium nitrite aqueous solution were added. The resulting suspension was added dropwise to a mixture of 100 parts water and 42 parts of 35% hydrochloric acid to prepare the diazo solution. Next, 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid were added to 300 parts of water and dissolved in 25% sodium hydroxide aqueous solution to make it weakly alkaline. The previously obtained diazo solution was added dropwise to this solution, maintaining the pH at 6.5-8.0, and stirred to complete the coupling reaction. After that, the mixture was salted out with sodium chloride, filtered, and dried to obtain 6.0 parts of the azo compound shown in Compound Example 1-47.

[0086] [Example S6] Except for replacing 10.7 parts of 3-methylaniline in step 1 of Example S5 with 12.1 parts of 2,5-dimethylaniline, and replacing 13.7 parts of 2-methoxy-5-methylaniline in step 2 of Example S5 with 15.3 parts of 2,5-dimethoxyaniline, 11.0 parts of the azo compound shown in Compound Example 1-42 was obtained in the same manner as in Example S5.

[0087] [Example S7] Except for replacing 32.0 parts of 1,8-dihydroxynaphthalene-3,6-disulfonic acid in step 1 of Example S1 with 44.2 parts of 1-hydroxy-3-(3-sulfopropoxy)naphthalene-3,6-disulfonic acid, 12.0 parts of the azo compound shown in Compound Example 1-22 was obtained in the same manner as in Example S1.

[0088] [Example S8] Except for replacing 32.0 parts of 1,8-dihydroxynaphthalene-3,6-disulfonic acid in step 1 of Example S1 with 33.4 parts of 1-hydroxy-8-methoxynaphthalene-3,6-disulfonic acid, and replacing 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid in step 3 of Example S1 with 37.5 parts of 1-hydroxy-6-(2,4-dimethoxyphenylamino)-3-naphthalenesulfonic acid, 12.0 parts of the azo compound shown in Compound Examples 1-15 was obtained in the same manner as in Example S1.

[0089] [Example S9] Except for replacing 32.0 parts of 1,8-dihydroxynaphthalene-3,6-disulfonic acid with 22.4 parts of 1-hydroxy-5-naphthalenesulfonic acid in step 1 of Example S1, 12.5 parts of the azo compound shown in Compound Example 1-38 was obtained in the same manner as in Example S1.

[0090] [Example S10] Except for replacing 32.0 parts of 1,8-dihydroxynaphthalene-3,6-disulfonic acid with 22.4 parts of 1-hydroxy-3-naphthalenesulfonic acid in step 1 of Example S1, 12.5 parts of the azo compound shown in Compound Example 1-18 were obtained in the same manner as in Example S1.

[0091] [Example S11] Except for replacing 32.0 parts of 1,8-dihydroxynaphthalene-3,8-disulfonic acid in step 1 of Example S1 with 30.4 parts of 1-hydroxynaphthalene-3,8-disulfonic acid, 13.5 parts shown in Compound Example 1-19 were obtained in the same manner as in Example S1.

[0092] [Example S12] Except for replacing 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid with 25.3 parts of 1-hydroxy-6-methylamino-3-naphthalenesulfonic acid in step 3 of Example S1, 9.2 parts of the azo compound shown in Compound Example 1-36 were obtained in the same manner as in Example S1.

[0093] [Example S13] Except that 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid in step 3 of Example S1 was replaced with 34.4 parts of the compound shown in formula (11) below, the same procedure as in Example S1 was followed to obtain 11.3 parts of the azo compound shown in Compound Example 1-32.

[0094] [ka]

[0095] [Example S14] Except for replacing 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid in step 3 of Example S1 with 55.1 parts of the compound represented by formula (12) below, the procedure was the same as in Example S1 to obtain 6.2 parts of the azo compound shown in Compound Example 1-35.

[0096] [ka]

[0097] [Example S15] Except for replacing 32.0 parts of 1,8-dihydroxynaphthalene-3,8-disulfonic acid with 30.4 parts of 1-hydroxynaphthalene-3,6-disulfonic acid in step 1 of Example S1, 13.5 parts of the azo compound shown in Compound Examples 1-7 were obtained in the same manner as in Example S1.

[0098] [Example S16] Except for replacing 15.0 parts of N-acetyl-1,4-phenylenediamine in step 1 of Example S1 with 19.4 parts of N-acetyl-2-methyl-5-methoxy-1,4-phenylenediamine, replacing 15.3 parts of 2,5-dimethoxyaniline in step 2 of Example S1 with 12.1 parts of 2,5-dimethylaniline, and replacing 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid in step 3 of Example S1 with 34.5 parts of 1-hydroxy-6-(4-methoxyphenylamino)-3-naphthalenesulfonic acid, 10.0 parts of the azo compound shown in Compound Example 1-48 was obtained in the same manner as in Example S1.

[0099] [Example S17] Except for replacing 15.3 parts of 2,5-dimethoxyaniline in step 2 of Example S1 with 12.1 parts of 2,5-dimethylaniline, and replacing 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid in step 3 of Example S1 with 34.5 parts of 1-hydroxy-6-(4-methoxyphenylamino)-3-naphthalenesulfonic acid, 10.0 parts of the azo compound shown in Compound Example 1-49 was obtained in the same manner as in Example S1.

[0100] [Example S18] Except for replacing 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid with 32.9 parts of 1-hydroxy-6-benzylamino-3-naphthalenesulfonic acid in step 3 of Example S1, 6.0 parts of the azo compound shown in Compound Example 1-34 was obtained in the same manner as in Example S1.

[0101] [Comparative Example S1] (Process 1) 15.0 parts of commercially available N-acetyl-1,4-phenylenediamine were 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 the mixture was stirred for 1 hour to diazotize it. 22.3 parts of 1-amino-7-naphthalenesulfonic acid were added to the resulting diazo solution, and the mixture was stirred for 8 hours while maintaining the pH at 3.5-6.0 with a 15% sodium carbonate aqueous solution to complete the coupling reaction. After that, the mixture was salted out with sodium chloride and filtered to obtain 100 parts of a wet cake of the monoazo compound shown in formula (13).

[0102] [ka]

[0103] (Process 2) 100 parts of the wet cake of the monoazo compound represented by formula (13) were added to 300 parts of water, stirred, and suspended. The pH was adjusted to 9.0 using 25% sodium hydroxide, and 17.3 parts of 40% sodium nitrite aqueous solution were added. The resulting aqueous solution was added dropwise to a mixture of 200 parts water and 42 parts of 35% hydrochloric acid to prepare a diazo solution. Next, 32.0 parts of 1,8-dihydroxynaphthalene-3,6-disulfonic acid were added to 200 parts of water and dissolved in 25% sodium hydroxide aqueous solution to make it weakly alkaline. The previously obtained diazo solution was added dropwise to this solution, maintaining the pH at 6.5 to 8.0, and stirred to complete the coupling reaction. After that, the mixture was salted out with sodium chloride, filtered, and dried to obtain 15.0 parts of the azo compound represented by formula (14).

[0104] [ka]

[0105] [Comparative example S2] The compound example (VI) (formula (15) below) used in Example S1 described in Patent Document 2 was used as the compound for Comparative Example 2.

[0106] [ka]

[0107] [Comparative Example S3] CIDirect Blue 67 (formula (16) below), a dichroic dye having the same color disazo structure as Example S1, was used as the compound for Comparative Example S3.

[0108] [ka]

[0109] (Examples F1-F18 and Comparative Examples F1-F3: Fabrication of polarizing films) A 75 μm thick sheet of polyvinyl alcohol was immersed for 4 minutes in an aqueous solution (dyeing bath) at 45°C, containing 0.03% of the azo compound obtained in Examples S1-S18 and Comparative Examples S1-S3, and 0.1% of Glauber's salt. This film was stretched five times in a 3% boric acid aqueous solution at 50°C, and while maintaining tension, it was washed with water and dried to obtain a polarizing film.

[0110] Table 1 shows the transmittance and polarization of the obtained polarizing films at the maximum absorption wavelength. The transmittance and polarization of the polarizing films at the maximum absorption wavelength were measured using a spectrophotometer (Hitachi U-4100). Single-layer transmittance (Ts) refers to the transmittance at the maximum absorption wavelength obtained by measuring a single polarizing film, parallel transmittance (Tp) refers to the transmittance at the maximum absorption wavelength obtained by measuring two polarizing films in parallel, orthogonal transmittance (Tc) refers to the transmittance at the maximum absorption wavelength obtained by measuring two polarizing films in parallel, polarization (ρ) is the value calculated by equation (I), and contrast (CR) was calculated by dividing the parallel transmittance by the orthogonal transmittance.

[0111] Polarization rate (%)=100×[(Tp-Tc) / (Tp+Tc)] 1 / 2 (I)

[0112] [Table 1]

[0113] As shown in Table 1, the polarizing films prepared using the azo compounds of Examples S1 to S18 all exhibited high polarization rates. Specifically, the polarizing films of Examples F1 to F18 showed a polarization degree of 97% or higher at a single transmittance of approximately 44%, while none of the polarizing films of Comparative Examples F1 to F3 reached a polarization degree of 97%. Furthermore, in terms of contrast, which is one indicator of image quality and shows the difference in brightness between white and black displays, the polarizing films of Examples F1 to F18 had a minimum contrast of 47, while the polarizing films of Comparative Examples F1 to F3 had a maximum contrast of 25, indicating that the polarizing films of the present invention have a contrast that is almost twice as high.

[0114] (Example P1: Fabrication of a neutral gray polarizing plate) A polarizing film was prepared in the same manner as in Example F1, except that an aqueous solution at 45°C containing 0.3% of the compounds from Compound Examples 1-8 obtained in Example S1, 0.15% of CI Direct Red 81, 0.1% of CI Direct Orange 39, and 0.1% of Glauber's salt was used as the dyeing bath. The obtained polarizing film had an average single-plate transmittance of 42% at 430-640 nm and an average transmittance of 0.1% at orthogonal positions, indicating a high degree of polarization. Triacetylcellulose film (TAC film: Fujifilm Corporation: product name TD-80U) was laminated to both sides of this polarizing film via an adhesive of an aqueous polyvinyl alcohol solution, and glass was attached using an adhesive to obtain a dye-based polarizing plate (neutral gray polarizing plate) in which TAC / polarizing film / TAC / glass were laminated in this order.

[0115] The neutral gray polarizer obtained in Example P1 showed no change in the average transmittance of a single sheet even after 500 hours in an environment of 105°C and after 500 hours under conditions of 80°C and 90% relative humidity, demonstrating long-term durability even under high temperature and high humidity conditions. Furthermore, the neutral gray polarizer of Example P1 showed no change in the average transmittance of a single sheet even after 200 hours in a xenon lightfastness test (Suga Test Instruments SX-75) under conditions of 60W and an ambient temperature of 50°C, demonstrating excellent lightfastness against long-term exposure to light. These results indicate that the neutral gray polarizers of Example P1 all possess excellent polarization performance and durability (humidity resistance, heat resistance, and lightfastness), making them high-performance dye-based polarizers. [Industrial applicability]

[0116] The polarizing film or polarizing plate of the present invention can be optionally equipped with a protective layer or functional layer and a transparent support such as glass, quartz, or sapphire, and can be applied to liquid crystal projectors, calculators, watches, laptop computers, word processors, liquid crystal televisions, polarizing lenses, polarizing glasses, car navigation systems, and indoor and outdoor measuring instruments and displays. In particular, the polarizing film or polarizing plate of the present invention can be suitably used in liquid crystal display devices, such as reflective liquid crystal display devices, semi-transparent liquid crystal display devices, and organic electroluminescence devices other than liquid crystal display devices.

Claims

1. A polarizing film containing an azo compound represented by the following formula (2) or a salt thereof. 【Chemistry 1】 (In formula (2), Ra2 is a hydroxy group, Ra1 represents a hydrogen atom, a hydroxy group, a C1-4 alkoxy group, or a C1-4 alkoxy group having a sulfo group, Ab １ and Ab ２ either represents a sulfo group, a carboxy group, or an amino group which may have a substituent, and the other is a substituent selected from the group consisting of a hydrogen atom, a sulfo group, a carboxy group, or an amino group which may have a substituent, Rb １ to Rb ６ each independently represents a hydrogen atom, a C1-4 alkyl group, a C1-4 alkoxy group, a sulfo group, a C1-4 alkoxy group having a sulfo group, or an amino group which may have a substituent, h represents 0 or 1, Xb １ represents an amino group which may have at least one substituent S, a phenylamino group which may have a substituent, a phenylazo group which may have a substituent, a naphthotriazole group which may have a substituent, or a benzoylamino group which may have a substituent, and the substituent S (when there are plural, each independently) is further selected from the group consisting of a C1-4 alkyl group which may have a substituent, a C1-4 alkoxy group, a sulfo group, an amino group, a C1-4 alkylamino group, a hydroxy group, a carboxy group, and a carboxyethylamino group, and Xb1 is different from the above Ra １ , Ra ２ , Ab １ , and Ab ２ .)

2. The polarizing film according to claim 1, wherein the azo compound or salt thereof represented by formula (2) is an azo compound or salt thereof represented by the following formula (4). 【Chemistry 4】 (In the above formula (4), Ra １ Ra ２ Ab １ Ab ２ , Rb １ ~Rb ６ , h, Xb １ Each of these has the same meaning as equation (2).

3. The polarizing film according to claim 1, wherein the azo compound or salt thereof represented by formula (2) is an azo compound or salt thereof represented by the following formula (5). 【Transformation 5】 (In the above formula (5), Ra １ Ab １ , Rb １ ~Rb ６ , h, Xb １ Each of these has the same meaning as equation (2).

4. The polarizing film according to claim 1, wherein the azo compound or salt thereof represented by formula (2) is an azo compound or salt thereof represented by the following formula (6). 【Transformation 6】 (In the above formula (6), Ra １ Ab １ , Rb １ ~Rb ６ , h, Xb １ Each of these has the same meaning as equation (2).

5. In formula (6), Ra １ The polarizing film according to claim 4, wherein is a hydroxyl group.

6. A polarizing film according to any one of claims 1 to 5, comprising a substrate.

7. The polarizing film according to claim 6, wherein the substrate is a film made of polyvinyl alcohol resin or a derivative thereof.

8. A polarizing film according to any one of claims 1 to 7, comprising one or more organic dyes other than the azo compound or salt thereof described in formula (2).

9. A polarizing film according to any one of claims 6 to 8, having a neutral gray color.

10. A polarizing plate comprising a transparent protective film provided on one or both sides of the polarizing film according to any one of claims 6 to 9.

11. A display device comprising a polarizing film according to any one of claims 1 to 9 or a polarizing plate according to claim 10.

Images