Polarizing film, polarizing plate and liquid crystal display device containing azo compound or its salt

Abstract

A polarizing film containing an azo compound or a salt thereof represented by the following formula (1). In formula (1), Ra1, Ra2, Ab1, and Ab2 are substituted at any one of ring a and ring b, any one of Ra1 and Ra2 is a hydroxyl group, and the other represents a hydrogen atom, a hydroxyl group, a C1-4 alkoxy group, or a C1-4 alkoxy group having a sulfonic acid group, any one of Ab1 and Ab2 represents a sulfonic acid group, a carboxyl 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 sulfonic acid group, a carboxyl group, or an amino group which may have a substituent, and Rb1 to Rb6 each independently represent a hydrogen atom, a C1-4 alkyl group, a C1-4 alkoxy group, a sulfonic acid group, wherein 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, and the substituent S is selected from the group consisting of a C1 to 4 alkyl group, a C1 to 4 alkoxy group, a sulfonic acid group, an amino group, a C1 to 4 alkylamino group, a hydroxyl group, a carboxyl group, and a carboxyethylamino group, and is different from the above-mentioned 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] Polarizing plates with light transmission / shading functions, together with liquid crystals with light switching functions, are basic components of display devices (displays) such as liquid crystal displays (LCDs). The application fields of this LCD can also be cited from small machines such as computers and clocks in the early days to notebook computers, word processors, liquid crystal projectors, liquid crystal televisions, car navigation, and indoor and outdoor measuring machines. In addition, it can also be applied to lenses with polarizing functions, and to sunglasses with improved visual recognition and polarized glasses corresponding to 3D televisions in recent years. Since the use of polarizing plates as described above is expanding on a large scale, the conditions of use are also used under a wide range of conditions from low temperature to high temperature, low humidity to high humidity, and low light intensity to high light intensity, so polarizing plates with high polarization performance and high durability are sought.

[0003] At present, polarizing plates are manufactured by the following methods: dyeing or containing iodine or dichroic dyes on a film of polyvinyl alcohol or its derivatives and stretching and orienting it, or generating polyene by dehydrating a polyvinyl chloride film with hydrochloric acid or a polyvinyl alcohol film and orienting it. These substances will greatly affect the polarization characteristics and durability of the polarizing plate. Although the iodine-based polarizing film made with iodine has excellent polarization performance, it has weak resistance to water and heat, and has problems with durability when used for a long time under high temperature and high humidity. In order to improve durability, methods of treating with formalin or an aqueous solution containing boric acid, and methods of using a polymer film with low moisture permeability as a protective film have been considered, but the effect is still insufficient.

[0004] On the other hand, compared with iodine-based polarizing films, dye-based polarizing films made using dyes have excellent moisture resistance and heat resistance, but generally speaking, the polarization performance is insufficient. Dye-based neutral gray polarizing plates are generally manufactured by combining multiple dyes, but the polarization performance of dye-based neutral gray polarizing plates is insufficient, and it is necessary to develop dichroic dyes with good polarization performance in various colors used.

[0005] Examples of the dye-based polarizing film include those produced using water-soluble azo compounds as described in Patent Documents 1 to 3. However, sufficient polarizing properties have not been obtained, and further improvement in performance has been sought.

[0006] [Prior art literature]

[0007] [Patent Document]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 05-053014

[0009] [Patent Document 2] Japanese Patent Application Laid-Open No. 05-295282

[0010] [Patent Document 3] Japanese Patent Application Laid-Open No. 09-230142

[0011] [Patent Document 4] Japanese Patent Application Laid-Open No. 11-218611

[0012] [Patent Document 5] Japanese Patent Application Publication No. 2001-33627

[0013] [Patent Document 6] Japanese Patent Application Publication No. 2009-132794

[0014] [Patent Document 7] Japanese Patent Application Publication No. 2001-240762

[0015] [Patent Document 8] Japanese Patent Application Publication No. 2001-108828

[0016] [Patent document 9] Japanese Patent Application Publication No. 60-156759.

[0017] [Non-patent literature]

[0018] [Non-patent document 1] Dye Chemistry; written by Yutaka Hosoda, published by Gihodo, 1957, page 621

[0019] [Non-patent document 2] Application of functional pigments (published by CMC Co., Ltd., 1st edition, supervised by Masahiro Irie, pages 98 to 100). Summary of the invention

[0020] [Problems to be solved by the invention]

[0021] One object of the present invention is to provide a high-performance polarizing film and polarizing plate with excellent polarizing performance. In addition, another object of the present invention is to provide a neutral gray polarizing plate that leaks color in an orthogonal direction in the wavelength range of the visible light region. In addition, another object of the present invention is to provide a high-performance polarizing plate with excellent polarizing performance and durability (heat resistance, moisture resistance or light resistance).

[0022] [Methods to solve the problem]

[0023] As a result of intensive studies to achieve the above-mentioned object, the inventors of the present application have found that a polarizing film and a polarizing plate containing a specific azo compound and a salt thereof have excellent polarizing performance and durability.

[0024] That is, the present invention relates to the following [1] to

[12] , but is not limited thereto.

[0025] [1] A polarizing film comprising an azo compound represented by the following formula (1) or a salt thereof.

[0026]

[0027] (In formula (1), Ra1, Ra2, Ab1, and Ab2 are substituted on any one of ring a and ring b, any one of Ra1 and Ra2 is a hydroxyl group, and the other represents a hydrogen atom, a hydroxyl group, a C1-4 alkoxy group, or a C1-4 alkoxy group having a sulfonic acid group, any one of Ab1 and Ab2 represents a sulfonic acid group, a carboxyl 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 sulfonic acid group, a carboxyl group, or an amino group which may have a substituent, and Rb1 to Rb6 each independently represent a hydrogen atom, a C1-4 alkyl group, a C1-4 alkoxy group, a sulfonic acid group, a C1-4 alkoxy group, a sulfonic acid group, a C1-4 alkoxy group having a sulfonic acid group 4 or an amine group which may have a substituent, h represents 0 or 1, Xb1 represents an amine group which may have at least one substituent S, a phenylamine group which may have a substituent, a phenylazo group which may have a substituent, a naphthotriazolyl group which may have a substituent, or a benzoylamine group which may have a substituent, and the substituent S (when there are multiple substituents, each independently) is selected from the group consisting of a C1 to 4 alkyl group which may further have a substituent, a C1 to 4 alkoxy group, a sulfonic acid group, an amine group, a C1 to 4 alkylamine group, a hydroxyl group, a carboxyl group and a carboxyethylamine group, and is different from the above-mentioned Ra1, Ra2, Ab1 and Ab2).

[0028] [2] The polarizing film according to the above item [1], wherein the azo compound represented by the above formula (1) or a salt thereof is an azo compound represented by the following formula (2) or a salt thereof.

[0029]

[0030] (In formula (2), Ra1, Ra2, Ab1, Ab2, Rb1 to Rb6, h, and Xb1 respectively represent the same meanings as in formula (1)).

[0031] [3] The polarizing film according to the above item [1] or [2], wherein the azo compound represented by the above formula (1) or a salt thereof is an azo compound represented by the following formula (3) or a salt thereof.

[0032]

[0033] (In the above formula (3), Ra1, Ra2, Ab1, Ab2, Rb1 to Rb6, h, and Xb1 respectively represent the same meanings as in formula (1)).

[0034] [4] The polarizing film according to any one of the above items [1] to [3], wherein the azo compound represented by the formula (1) or a salt thereof is an azo compound represented by the following formula (4) or a salt thereof.

[0035]

[0036] (In the above formula (4), Ra1, Ra2, Ab1, Ab2, Rb1 to Rb6, h, and Xb1 respectively represent the same meanings as in formula (1)).

[0037] [5] The polarizing film according to any one of the above items [1] to [4], wherein the azo compound represented by the formula (1) or a salt thereof is an azo compound represented by the following formula (5) or a salt thereof.

[0038]

[0039] (In the above formula (5), Ra1, Ab1, Rb1 to Rb6, h, and Xb1 respectively represent the same meanings as in formula (1)).

[0040] [6] The polarizing film according to any one of the above items [1] to [5], wherein the azo compound represented by the formula (1) or a salt thereof is an azo compound represented by the following formula (6) or a salt thereof.

[0041]

[0042] (In the above formula (6), Ra1, Ab1, Rb1 to Rb6, h, and Xb1 respectively represent the same meanings as in formula (1)).

[0043] [7] The polarizing film according to any one of the above items [1] to [6], further comprising a substrate.

[0044] [8] The polarizing film according to the above item [7], wherein the substrate is a film made of a polyvinyl alcohol resin or a derivative thereof.

[0045] [9] The polarizing film according to any one of the above items [1] to [8], which contains one or more organic dyes other than the azo compound or a salt thereof represented by any one of the above formulas (1) to (6).

[0046]

[10] The polarizing film as described in any one of the above items [7] to [9], which has a neutral gray color.

[0047]

[11] A polarizing plate comprising a transparent protective film provided on one or both surfaces of the polarizing film according to any one of [7] to

[10] above.

[0048]

[12] A display device comprising the polarizing film as described in any one of the above items [1] to

[10] or the polarizing plate as described in the above item

[11] .

[0049] [Effects of the invention]

[0050] The polarizing film and polarizing plate of the present invention have excellent polarizing performance. In one aspect, the polarizing plate of the present invention with neutral gray presents a high-performance achromatic color with no color leakage in the orthogonal direction in the wavelength range of the visible light region. In one aspect, the polarizing film and polarizing plate of the present invention have excellent polarizing performance (transmittance, contrast) and durability (moisture resistance, heat resistance, light resistance). DETAILED DESCRIPTION

[0051] In the present specification and claims, "azo compound or its salt" may be simply referred to as "azo compound" except when the free form is clearly indicated.

[0052] In this specification and claims, "substituent" may also include hydrogen atoms, so for convenience, hydrogen atoms are sometimes described as "substituents". "May have a substituent" means that it also includes the case of not having a substituent. For example, "phenyl that may have a substituent" includes unsubstituted simple phenyl and phenyl with a substituent. In addition, the "lower" of the lower alkyl, lower alkoxy, etc. of the present application, unless otherwise specified, means that the number of carbon atoms is 1 to 4 (C1 to 4), preferably 1 to 3 (C1 to 3).

[0053] <Azo compound or its salt>

[0054] The polarizing film of the present invention contains an azo compound represented by the following formula (1) or a salt thereof.

[0055]

[0056] (In formula (1), Ra1, Ra2, Ab1, and Ab2 are substituted on any one of ring a and ring b, any one of Ra1 and Ra2 is a hydroxyl group, and the other represents a hydrogen atom, a hydroxyl group, a C1-4 alkoxy group, or a C1-4 alkoxy group having a sulfonic acid group, any one of Ab1 and Ab2 represents a sulfonic acid group, a carboxyl 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 sulfonic acid group, a carboxyl group, or an amino group which may have a substituent, and Rb1 to Rb6 each independently represent a hydrogen atom, a C1-4 alkyl group, a C1-4 alkoxy group, a sulfonic acid group, a C1-4 alkoxy group, a sulfonic acid group, a C1-4 alkoxy group having a sulfonic acid group 4 or an amine group which may have a substituent, h represents 0 or 1, Xb1 represents an amine group which may have at least one substituent S, a phenylamine group which may have a substituent, a phenylazo group which may have a substituent, a naphthotriazolyl group which may have a substituent, or a benzoylamine group which may have a substituent, and the substituent S (when there are multiple substituents, each independently) is selected from the group consisting of a C1 to 4 alkyl group which may further have a substituent, a C1 to 4 alkoxy group, a sulfonic acid group, an amine group, a C1 to 4 alkylamine group, a hydroxyl group, a carboxyl group and a carboxyethylamine group, and is different from the above-mentioned Ra1, Ra2, Ab1 and Ab2).

[0057] An amino group which may have a substituent can be selected as Rb1 to Rb6, and an unsubstituted amino group or an amino group having one or two substituents (C1 to 4 alkyl group, acetyl group) is more preferable.

[0058] The amino group which may have a substituent S is preferably an unsubstituted amino group, an amino group having one or two C1-4 alkyl groups which may have a substituent (hydroxyl group, methoxyl group, ethoxyl group, amino group, carboxyl group, sulfonic acid group, phenyl group), and more preferably a hydrogen atom, or an amino group having one or two methyl groups. The phenylamino group which may have a substituent is preferably a phenylamino group having one or two substituents selected from the group consisting of a hydrogen atom, a lower alkyl group, a lower alkoxyl group, a sulfonic acid 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 methoxyl group, a sulfonic acid group, a carboxyl group, and an amino group. The phenylazo group which may have a substituent is preferably a phenylazo group having 1 to 3 substituents selected from the group consisting of a hydrogen atom, a hydroxyl group, a C1-4 alkyl group, a C1-4 alkoxyl group, an amino group, a hydroxyl group, and a carboxyethylamino group. The benzoylamino group which may have a substituent is preferably a benzoylamino group having a substituent selected from the group consisting of a hydrogen atom, a hydroxyl group, an amino group and a carboxyethylamino group. The naphthotriazolyl group which may have a substituent is unsubstituted, or preferably has one or two substituents selected from the group consisting of a sulfonic acid group, an amino group and a carboxyl group, and more preferably has one or two sulfonic acid groups as substituents. The substitution position of the substituents which may be possessed by the above-mentioned phenylamino group, phenylazo group and benzoylamino group is not particularly limited, and it is more preferably that one of the substituents is ortho to these respective amino groups, azo groups or amide groups. When the hydroxyl position of the substituted naphthyl group is taken as the 1-position, the substitution position of Xb1 is preferably the 6-position or the 7-position, and more preferably the 6-position.

[0059] In formula (1), examples of the "C1 to 4 alkyl group" include linear alkyl groups such as methyl, ethyl, n-propyl and n-butyl, branched alkyl groups such as sec-butyl and tert-butyl, and unsaturated hydrocarbon groups such as vinyl.

[0060] In the formula (1), examples of the "C1 to 4 alkoxy group" include a methoxy group, an ethoxy group, a propoxy group, an n-butoxy group, a sec-butoxy group, and a tert-butoxy group.

[0061] When the azo compound or its salt represented by formula (1) is an azo compound or its salt represented by the following formula (2), a polarizing film with further improved transmittance and high polarization degree can be provided, so it is more preferred. In addition, a polarizing film with further improved transmittance and high polarization degree in the parallel orientation of 550nm to 700nm can be provided, so it is more preferred. The azo compound or its salt represented by formula (1) is more preferably a compound or its salt represented by formula (3), more preferably a compound or its salt represented by formula (4), more preferably a compound or its salt represented by formula (5), and particularly preferably an azo compound or its salt represented by formula (6).

[0062]

[0063] (In formula (2), Ra1, Ra2, Ab1, Ab2, Rb1 to Rb6, h, and Xb1 respectively represent the same meanings as in formula (1)).

[0064]

[0065] (In the above formula (3), Ra1, Ra2, Ab1, Ab2, Rb1 to Rb6, h, and Xb1 respectively represent the same meanings as in formula (1)).

[0066]

[0067] (In the above formula (4), Ra1, Ra2, Ab1, Ab2, Rb1 to Rb6, h, and Xb1 respectively represent the same meanings as in formula (1)).

[0068]

[0069] (In the above formula (5), Ra1, Ab1, Rb1 to Rb6, h, and Xb1 respectively represent the same meanings as in formula (1)).

[0070]

[0071] (In the above formula (6), Ra1, Ab1, Rb1 to Rb6, h, and Xb1 respectively represent the same meanings as in formula (1)).

[0072] The azo compound represented by formula (1) or its salt can be easily produced by well-known diazotization and coupling according to the general azo dye production method described in Non-Patent Document 1. The synthesis method is described by taking the azo compound represented by formula (2) and h=0 as an example.

[0073] First, the amine represented by the formula (A) is diazotized by a known method as described in Non-Patent Document 1, and is coupled once with the aniline represented by the following formula (B) to obtain a monoazoamine compound represented by the following formula (C).

[0074]

[0075] (In formula (A) to formula (C), Ra1, Ra2, Ab1, Ab2, Rb1, and Rb2 respectively represent the same meanings as in formula (1)).

[0076] Next, the monoazoamine compound (C) is diazotized by a known method as described in Non-Patent Document 1, and secondarily coupled with an aniline of the following formula (D) to obtain a disazoamine compound of the following formula (E).

[0077]

[0078] (In formula (D) and formula (E), Ra1, Ra2, Ab1, Ab2, Rb1 to Rb4 respectively have the same meanings as in formula (1)).

[0079] The compound of formula (E) is diazotized by a known method such as described in Non-Patent Document 1, and coupled with a naphthol represented by the following formula (F), thereby obtaining an azo compound of formula (2).

[0080]

[0081] (In formula (F), Xb1 represents the same meaning as in formula (1)).

[0082] In the above reaction, the diazotization step is carried out by the cis method or the reverse method. The so-called cis method is to mix a nitrite such as sodium nitrite with an aqueous solution or suspension of an inorganic acid such as hydrochloric acid or sulfuric acid of the diazo component, and the so-called reverse method is to pre-add a nitrite to a neutral or weakly alkaline aqueous solution of the diazo component and then mix it with an inorganic acid. The diazotization temperature is preferably -10 to 40°C. In addition, 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 liquids, and performing the step under acidic conditions of a temperature of -10 to 40°C and a pH of 2 to 7.

[0083] The monoazo compound or disazo compound obtained by coupling can be directly or precipitated by acid precipitation or salt precipitation and then filtered out, or directly enter the next step in the state of solution or suspension. When the monoazo compound or disazo compound obtained by coupling is poorly soluble and becomes a suspension, it can also be filtered and used as a filter cake in the next coupling step.

[0084] The coupling reaction of the diazo compound of the disazo compound and the naphthols represented by formula (F) is preferably carried out under neutral to alkaline conditions of a temperature of -10 to 40°C and a pH of 7 to 10. After the reaction is completed, the reaction product is precipitated by salting out and filtered out. In addition, if purification is required, it is sufficient to repeat salting out or use an organic solvent to precipitate it from water. Examples of the organic solvent used for purification include water-soluble organic solvents such as alcohols such as methanol and ethanol, and ketones such as acetone.

[0085] The starting material for synthesizing the azo compound represented by the above formula (1) or its salt is a substituted naphthylamine compound represented by the formula (A). Examples of the naphthylamines of the formula (A) include 2-amino-1-hydroxy-naphthalene-6-sulfonic acid, 3-amino-1-hydroxy-naphthalene-6-sulfonic acid, 2-amino-8-hydroxy-naphthalene-6-sulfonic acid, 3-amino-8-hydroxy-naphthalene-6-sulfonic acid, 2-amino-1,8-dihydroxy-naphthalene-6-sulfonic acid, 3-amino-1,8-dihydroxy-naphthalene-6-sulfonic acid, 2-amino-1,8-dihydroxy-naphthalene-3-sulfonic acid, 2-amino-1,8-dihydroxy-naphthalene-3,6-disulfonic acid, 2-amino-1-methoxy-8-hydroxy-naphthalene-6-sulfonic acid, 3-amino-1-methoxy-8-hydroxy-naphthalene -6-sulfonic 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-(3-sulfonic acid propoxy)-naphthalene-3-sulfonic acid, 2-amino-1-hydroxy-8-(4-sulfonic acid butoxy)-naphthalene-3-sulfonic acid, 2-amino-1-(3-sulfonic acid propoxy)-8-hydroxy-naphthalene-3-sulfonic acid, 2-amino-1-(4-sulfonic acid butoxy)-8-hydroxy-naphthalene-3-sulfonic acid, 2-amino-1,8-dihydroxy-naphthalene-6-aminomethyl-3-disulfonic acid, etc., but are not limited thereto. More preferred are 2-amino-1,8-dihydroxy-naphthalene-6-sulfonic acid, 2-amino-1,8-dihydroxy-naphthalene-3-sulfonic acid, 2-amino-1,8-dihydroxy-naphthalene-3,6-disulfonic acid, 2-amino-1-methoxy-8-hydroxy-naphthalene-6-sulfonic acid, and 2-amino-1-hydroxy-8-methoxy-naphthalene-6-sulfonic acid.

[0086] In the above formula (1), the anilines having substituents (Rb1 to Rb6) as the primary or secondary coupling components when h is 0 or the primary to tertiary coupling components when h is 1 include, 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. amine, 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, 1-sulfonic acid, 4-(3-amino-4-methoxyphenoxy) butane-1-sulfonic acid, 2-(3-amino-4-methoxyphenoxy) ethane-1-sulfonic acid, 3-(2-amino-4-ethoxyphenoxy) propane-1-sulfonic acid, 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, 2-(3-amino-4-ethoxyphenoxy) ethane-1-sulfonic acid, etc. The amine groups of these aromatic amines may also be protected. As a protecting group, for example, ω-methanesulfonic acid group may be mentioned.

[0087] In the above formula (1), the naphthols having Xb1 as the tertiary coupling component when h is 0 or the quaternary coupling component when h is 1 include, for example, 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, 6-(4′-aminobenzoyl)amino-3-sulfonic acid-1-naphthol, etc., but are not limited to these.

[0088] Specific examples of the azo compound represented by the above formula (1) or a salt thereof are listed below. In addition, the azo compound is represented in the form of a free acid.

[0089] [Compound Example 1-1]

[0090]

[0091] [Compound Example 1-2]

[0092]

[0093] [Compound Examples 1-3]

[0094]

[0095] [Compound Examples 1-4]

[0096]

[0097] [Compound Example 1-5]

[0098]

[0099] [Compound Example 1-6]

[0100]

[0101] [Compound Example 1-7]

[0102]

[0103] [Compound Example 1-8]

[0104]

[0105] [Compound Example 1-9]

[0106]

[0107] [Compound Example 1-10]

[0108]

[0109] [Compound Example 1-11]

[0110]

[0111] [Compound Example 1-12]

[0112]

[0113] [Compound Example 1-13]

[0114]

[0115] [Compound Example 1-14]

[0116]

[0117] [Compound Example 1-15]

[0118]

[0119] [Compound Example 1-16]

[0120]

[0121] [Compound Example 1-17]

[0122]

[0123] [Compound Example 1-18]

[0124]

[0125] [Compound Example 1-19]

[0126]

[0127] [Compound Example 1-20]

[0128]

[0129] [Compound Example 1-21]

[0130]

[0131]

[0132] [Compound Example 1-24]

[0133]

[0134] [Compound Example 1-25]

[0135]

[0136]

[0137] [Compound Example 1-28]

[0138]

[0139] [Compound Example 1-29]

[0140]

[0141] [Compound Example 1-30]

[0142]

[0143] [Compound Example 1-31]

[0144]

[0145] [Compound Example 1-32]

[0146]

[0147] [Compound Example 1-33]

[0148]

[0149] [Compound Example 1-34]

[0150]

[0151] [Compound Example 1-35]

[0152]

[0153] [Compound Example 1-36]

[0154]

[0155] [Compound Example 1-37]

[0156]

[0157] [Compound Example 1-38]

[0158]

[0159] [Compound Example 1-39]

[0160]

[0161] [Compound Example 1-40]

[0162]

[0163] [Compound Example 1-41]

[0164]

[0165]

[0166] [Compound Example 1-44]

[0167]

[0168] [Compound Example 1-45]

[0169]

[0170] [Compound Example 1-47]

[0171]

[0172] [Compound Example 1-48]

[0173]

[0174] [Compound Example 1-49]

[0175]

[0176] [Compound Example 1-50]

[0177]

[0178] The azo compound shown in formula (1) may be in the form of a free acid or a salt, but may also be a salt of a metal ion or an ammonium ion. 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 a free acid, sulfonic acid (-SO3H) is represented, in the case of a sodium ion, sodium sulfonate (-SO3Na) is represented, and in the case of an ammonium ion, ammonium sulfonate (-SO3NH4) is represented.

[0179] <Polarizing film>

[0180] The polarizing film of the present invention contains an azo compound or a salt thereof represented by formula (1) as a dichroic dye. The polarizing film is a neutral gray polarizing film and a color polarizing film, preferably a neutral gray polarizing film. Here, "neutral gray" means that when two polarizing films are overlapped in a manner in which their orientation directions are orthogonal to each other (hereinafter also referred to as "orthogonal orientation"), there is little light leakage (color leakage) of a specific wavelength in the wavelength range of the visible light region.

[0181] The polarizing film of the present invention comprises azo compounds or their salts shown in formula (1) alone or in combination of more than one as a dichroic dye, and may further contain other organic dyes other than the azo compounds shown in formula (1) as required. Other organic dyes are not particularly limited, and preferably have absorption characteristics in a wavelength region different from the absorption wavelength region of the azo compounds or their salts shown in formula (1) and have higher dichroicity. As other organic dyes, 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 and dyes described in non-patent document 2 can be cited as representative examples, but it is more preferably used for the purpose of using dyes developed for polarizing plates as described in patent documents 4 to 9. These organic dyes are used in the form of free acids, alkali metal salts (eg, Na salts, K salts, Li salts), ammonium salts, or amine salts.

[0182] When other organic dyes are used in combination, the type of organic dyes to be blended varies depending on the target polarizing film, such as a neutral gray polarizing film, a color polarizing film for a liquid crystal projector, or other color polarizing films. The blending ratio is not particularly limited, but generally, it is preferred to use at least one other organic dye in a total amount within a range of 0.01 to 100 parts by mass, and more preferably within a range of 0.1 to 10 parts by mass, relative to 1 part by mass of the azo compound of formula (1) or its salt.

[0183] When the target polarizing film is a neutral gray polarizing film, the type and blending ratio of other organic dyes used in combination are adjusted to reduce color leakage of the obtained polarizing film in the wavelength range of the visible light region.

[0184] When the target polarizing film is a color polarizing film, the types and blending ratios of other organic dyes used in combination are adjusted so that the resulting polarizing film has a high single-plate average transmittance in a specific wavelength region and a lower average transmittance in an orthogonal direction, for example, a single-plate average transmittance of more than 39% and an average transmittance in an orthogonal direction of less than 0.4% in a specific wavelength region.

[0185] The polarizing film of the present invention can be produced by incorporating a dichroic dye comprising the azo compound represented by formula (1) or a salt thereof and other dyes as required into a polarizing film substrate (also simply referred to as "substrate") and orienting the same by a known method.

[0186] The substrate is preferably a polymer film, more preferably a film composed of a polyvinyl alcohol resin or a derivative thereof. Specific examples of the substrate include polyvinyl alcohol resin or a film modified with an olefin such as ethylene or propylene or an unsaturated carboxylic acid such as crotonic acid, acrylic acid, methacrylic acid, and maleic acid. As the substrate, from the viewpoint of the adsorption and orientation of the dye, a film composed of a polyvinyl alcohol resin or a derivative thereof is preferably used. The thickness of the substrate is usually 10 to 100 μm, more preferably about 20 to 80 μm.

[0187] When the substrate is a polymer film, in order to make it contain the azo compound or its salt of formula (1), a method of dyeing the polymer film is usually adopted. For example, dyeing is carried out in the following manner. First, the azo compound or its salt represented by formula (1) and other organic dyes as required are dissolved in water to prepare a dye bath. The dye concentration in the dye bath is not particularly limited, but is usually selected from the range of about 0.001 to 10% by mass. In addition, dyeing auxiliaries can also be used as required, for example, it is appropriate 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 for dyeing. The dyeing temperature is preferably about 30 to 80°C.

[0188] The orientation of the azo compound or its salt represented by formula (1) is carried out 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. As a stretching method, any well-known method such as a wet method or a dry method can also be used. The stretching of the polymer film can also be carried out before dyeing as appropriate. In this case, the orientation of the water-soluble dye is carried out at the time of dyeing. The polymer film containing the water-soluble dye and oriented is subjected to post-treatment such as boric acid treatment by a well-known method as required. This post-treatment is carried out to improve the transmittance and polarization degree of the polarizing film. The conditions of the boric acid treatment vary depending on the type of polymer film used or the type of dye used, but generally the boric acid concentration of the boric acid aqueous solution is, for example, in the range of 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 immersion is carried out for 0.5 to 10 minutes. If necessary, a fixing treatment may be performed with an aqueous solution containing a cationic polymer compound.

[0189] As the use of the polarizing film of the present invention, for example, liquid crystal projectors, computers, clocks, laptop computers, word processors, liquid crystal televisions, car navigation, indoor and outdoor measuring machines or displays, lenses or glasses, etc. The polarizing film made using the dye of the present invention (hereinafter also referred to as "dye-based polarizing film") has a high polarizing performance comparable to that of a polarizing film made using iodine (hereinafter also referred to as "iodine-based polarizing film"), and the durability is also excellent. Therefore, it is particularly suitable for uses that require high polarizing performance and durability, such as various liquid crystal displays and liquid crystal projectors such as vehicle-mounted and outdoor display uses (for example, industrial instrument display uses or wearable uses).

[0190] <Polarizing plate>

[0191] The polarizing plate of the present invention (hereinafter also referred to as "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, light resistance). As a material for forming the transparent protective film, it is more preferred to use a material with excellent optical transparency and mechanical strength, for example: cellulose acetate film, acrylic film, tetrafluoroethylene / hexafluoropropylene copolymer and other fluorine-based films, films composed of polyester resins, polyolefin resins or polyamide resins, etc. The transparent protective film is more preferably a triacetyl cellulose (TAC) film or a cycloolefin film. The thickness of the protective film is usually more preferably 40 to 200 μm.

[0192] In order to bond the polarizing film of the present invention to the protective film, an adhesive may be used. Examples of the adhesive that can be used include polyvinyl alcohol adhesives, urethane emulsion adhesives, acrylic adhesives, and polyester-isocyanate adhesives, and polyvinyl alcohol adhesives are preferred.

[0193] A transparent protective layer may also be further provided on the surface of the polarizing plate of the present invention. As a transparent protective layer, for example, an acrylic or polysiloxane hard coating or a urethane protective layer may be cited. In addition, in order to further improve the light transmittance of the single plate, it is more preferred to provide an anti-reflection layer (AR layer) on this transparent protective layer. The AR layer may be formed, for example, by evaporating or sputtering materials such as silicon dioxide and titanium oxide, and may be formed by thinly coating a fluorine-based material. The dye-based polarizing plate is preferably further provided with a support. The dye-based polarizing plate may also be used as an elliptically polarizing plate by attaching a phase difference plate to the surface.

[0194] The polarizing plate of the present invention may be either a neutral gray polarizing plate or a color polarizing plate depending on the application.

[0195] The neutral gray polarizing plate of the present invention has a neutral color, has little color leakage in the orthogonal direction in the polarization area of ​​the visible light region, and has excellent polarization performance. Even under high temperature and high humidity conditions, discoloration or reduction in polarization performance can be suppressed, and the durability is high. Therefore, it is suitable for use in vehicles or outdoor displays.

[0196] The neutral gray polarizing plate for vehicle use or outdoor display is preferably a polarizing plate with an AR layer attached by arranging an AR layer on the polarizing plate composed of the polarizing film of the present invention and a transparent protective film, which is used to further improve the light transmittance of the single body, and more preferably a polarizing plate with an AR layer and a support body attached to both the AR layer and a support body such as a transparent resin. The AR layer can be provided on one side or both sides of the polarizing plate. The support body is preferably provided on one side of the polarizing plate, and can be directly provided on the polarizing plate, or a polarizing plate with an AR layer attached on the support body (AR layer / polarizing plate / AR layer). The polarizing plate with an AR layer and a support body is preferably provided with an AR layer / polarizing plate / AR layer / support body in sequence. The support body is preferably one having a planar portion for attaching a polarizing plate. In addition, since it is for optical purposes, it is preferably a transparent substrate. As transparent substrates, there are generally inorganic substrates and organic substrates, and examples thereof include inorganic substrates such as soda glass, borosilicate glass, crystal substrates, sapphire substrates, and spinel substrates, and organic substrates such as acrylic, polycarbonate, polyethylene terephthalate, polyethylene naphthalate, and cycloolefin polymers, preferably organic substrates. The thickness or size of the transparent substrate can be a desired size.

[0197] Color polarizing plates have excellent polarization properties and will not change color or reduce polarization properties even under high temperature and high humidity conditions. Therefore, they are suitable for display devices such as liquid crystal projectors, in-vehicle displays, and outdoor displays.

[0198] The color polarizing plate for liquid crystal projector has brightness and excellent polarization performance. The average light transmittance of the single plate in the necessary wavelength region of the polarizing plate (A. When using an ultra-high pressure mercury lamp, the blue channel uses 420 to 500nm, the green channel uses 500 to 580nm, and the red channel uses 600 to 680nm; B. When using a three-primary color LED lamp, the peak wavelength is 430 to 450nm for the blue channel, 520 to 535nm for the green channel, and 620 to 635nm for the red channel) is 39% or more, and the average light transmittance in the orthogonal direction is 0.4% or less. More preferably, the average light transmittance of the single plate in the necessary wavelength region of the polarizing plate is 41% or more, and the average light transmittance in the orthogonal direction is 0.3% or less, and more preferably, it is 0.2% or less. More preferably, the average light transmittance of the single plate in the necessary wavelength region of the polarizing plate is 42% or more, and the average light transmittance in the orthogonal direction is 0.1% or less.

[0199] In addition, the single plate average light transmittance is the average value of the light transmittance in a specific wavelength region when natural light is incident on a single polarizing plate (hereinafter also referred to as a "polarizing plate") without a support such as an AR layer and a transparent glass plate. The average light transmittance in the orthogonal direction is the average value of the light transmittance in a specific wavelength region when natural light is incident on two polarizing plates in a state where their orientation directions are orthogonal to each other.

[0200] The polarizing film used in the color polarizing plate for vehicle-mounted or outdoor display is the same as the neutral gray polarizing plate. A protective layer or AR layer and a support body, etc. may also be provided on the dye-based polarizing plate as required. The color polarizing plate with a support body can be obtained, for example, by applying a transparent adhesive (adhesive) agent to the plane portion of the support body, and then attaching the dye-based polarizing plate to the coated surface. Alternatively, a transparent adhesive (adhesive) agent may be applied to the dye-based polarizing plate, and then the support body is attached to the coated surface. The adhesive (adhesive) agent is preferably, for example, an acrylate-based one. In addition, when the dye-based polarizing plate is used as an elliptical polarizing plate, it is usually the case that the phase difference plate side is attached to the support body and the stacking of the dye-based polarizing plate / phase difference plate / support body is formed in sequence, but the polarizing plate side may also be attached to the support body and the stacking of the phase difference plate / polarizing plate / support body is formed in sequence.

[0201] <Display device>

[0202] The display device of the present invention is provided with the polarizing film or polarizing plate of the present invention. As the display device, a liquid crystal display device or an organic electronic display device can be cited, such as a display device used for computers, clocks, notebook computers, word processors, liquid crystal televisions, car navigation, and indoor and outdoor measuring machines or displays, etc., and is particularly suitable for various display bodies that require high polarization performance and durability, such as vehicle-mounted or outdoor display (for example, industrial instrument display use or wearable use). The dye-based polarizing film or dye-based polarizing plate provided by the display device is preferably neutral gray.

[0203] In a liquid crystal display device, a dye-based polarizing plate is arranged on either or both sides of the incident side or the emission side of the liquid crystal cell. The dye-based polarizing plate may or may not be in contact with the liquid crystal cell, but from the viewpoint of durability, it is more preferably not in contact. On the emission side of the liquid crystal cell, when the dye-based polarizing plate is in contact with the liquid crystal cell, the liquid crystal cell can be used as a support for the dye-based polarizing plate. When the dye-based polarizing plate is not in contact with the liquid crystal cell, it is more preferred to use a dye-based polarizing plate provided with a support other than the liquid crystal cell. In addition, from the viewpoint of durability, it is more preferred to arrange the dye-based polarizing plate on both sides of the incident side and the emission side of the liquid crystal cell, and it is more preferred to arrange the polarizing plate surface of the dye-based polarizing plate on the liquid crystal cell side and the support surface on the light source side. In addition, the incident side of the liquid crystal cell is the light source side, and the opposite side is referred to as the emission side.

[0204] The liquid crystal cell of the liquid crystal display device is, for example, an active matrix type, preferably one formed by sealing liquid crystal between a transparent substrate formed with electrodes and TFTs and a transparent substrate formed with a counter electrode. Light emitted from a light source such as a cold cathode tube lamp or a white LED passes through a dye-based polarizing plate, then passes through the liquid crystal cell, a color filter, and then passes through the dye-based polarizing plate to be projected onto a display screen.

[0205] In liquid crystal display devices, dye-based polarizing plates have brightness and excellent polarization performance as well as polarization and light resistance. Therefore, even in high temperature and high humidity conditions such as in a car or outdoors, they are less likely to discolor or degrade in polarization performance, and have high reliability.

[0206] [Example]

[0207] The present invention will be further described in detail below by way of examples, which are provided for illustration only and are not intended to limit the present invention. % and parts in the examples are by mass unless otherwise specified.

[0208] [Example S1]

[0209] (Step 1)

[0210] 15.0 parts of N-acetyl-1,4-phenylenediamine, which is available as a commercial product, is added to 200 parts of water, stirred, and then 42 parts of 35% hydrochloric acid and 17.3 parts of 40% sodium nitrite are added and stirred for 1 hour to perform diazotization. Next, 32.0 parts of 1,8-dihydroxynaphthalene-3,6-disulfonic acid are added to 200 parts of water and dissolved in a 25% sodium hydroxide aqueous solution to become weakly alkaline. The previously obtained diazo liquid is kept at pH 6.5 to 8.0 and dripped into this liquid, and stirred to complete the coupling reaction. Next, the obtained reaction liquid is stirred at 90 to 99° C. for 5 hours at a pH of less than 0.5 (e.g., 0.01 to 0.5) to perform a hydrolysis reaction, and the deposited solid is filtered to obtain 150 parts of a wet cake of the monoazo compound represented by formula (7).

[0211]

[0212] (Step 2)

[0213] 150 parts of the wet cake of the monoazo compound represented by the obtained formula (7) are added to 300 parts of water, stirred to suspend it, and 25% sodium hydroxide is used to make it pH 9.0, and 17.3 parts of a 40% sodium nitrite aqueous solution are added thereto. The obtained aqueous solution is dripped into a mixed solution of 200 parts of water and 42 parts of 35% hydrochloric acid to prepare a diazo solution. 15.3 parts of 2,5-dimethoxyaniline are added to the obtained diazo solution, and the pH is maintained at 1.5 to 4.0 with a 15% sodium carbonate aqueous solution, and stirred for 8 hours to complete the coupling reaction. Thereafter, it is salted out with sodium chloride and filtered to obtain 200 parts of a wet cake of the disazo compound represented by the formula (8).

[0214]

[0215] (Step 3)

[0216] 200 parts of the wet cake of the obtained disazo compound represented by formula (8) are added to 500 parts of water, stirred to suspend it, and 25% sodium hydroxide is used to adjust the pH to 9.0, and 17.3 parts of a 40% sodium nitrite aqueous solution are added thereto. The obtained suspension is dripped into a mixed solution of 100 parts of water and 42 parts of 35% hydrochloric acid to prepare a diazo liquid. Next, 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid are added to 300 parts of water and dissolved in a 25% sodium hydroxide aqueous solution to become weakly alkaline. The previously obtained diazo liquid is maintained at a pH of 6.5 to 8.0 and dripped into this liquid, and stirred to complete the coupling reaction. Thereafter, it is salted out with sodium chloride, filtered, and dried, thereby obtaining 8.0 parts of the azo compound shown in compound example 1-8.

[0217] [Example S2]

[0218] 8.0 parts of the azo compound shown in Compound Example 1-10 was obtained in the same manner as in Example S1 except that 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid in Step 3 of Example S1 was replaced with 34.5 parts of 1-hydroxy-6-(4-methoxyphenylamino)-3-naphthalenesulfonic acid.

[0219] [Example S3]

[0220] 8.9 parts of the azo compound shown in Compound Example 1-14 was obtained in the same manner as in Example S1 except that 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid in Step 3 of Example S1 was replaced with 37.5 parts of 1-hydroxy-6-(2,4-dimethoxyphenylamino)-3-naphthalenesulfonic acid.

[0221] [Example S4]

[0222] 11.0 parts of the azo compound shown in Compound Example 1-31 was obtained in the same manner as in Example S1 except that 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid in Step 3 of Example S1 was replaced by 35.8 parts of 1-hydroxy-6-(4-aminobenzoylamino)-3-naphthalenesulfonic acid.

[0223] [Example S5]

[0224] (Step 1)

[0225] 150 parts of the wet cake of the monoazo compound represented by formula (7) in step 1 of Example S1 are added to 300 parts of water, stirred to suspend it, and 25% sodium hydroxide is used to adjust the pH to 9.0, and 17.3 parts of a 40% sodium nitrite aqueous solution are added thereto. The resulting aqueous solution is dropped into a mixed solution of 200 parts of water and 42 parts of 35% hydrochloric acid to prepare a diazo solution. 10.7 parts of 3-methylaniline are added to the resulting diazo solution, and the pH is maintained at 1.5 to 4.0 with a 15% sodium carbonate aqueous solution, and stirred for 8 hours to complete the coupling reaction. Thereafter, it is salted out with sodium chloride and filtered to obtain 200 parts of a wet cake of the disazo compound represented by formula (9).

[0226]

[0227] (Step 2)

[0228] 150 parts of the wet cake of the monoazo compound represented by the obtained formula (9) are added to 300 parts of water, stirred to suspend it, and 25% sodium hydroxide is used to adjust the pH to 9.0, and 17.3 parts of a 40% sodium nitrite aqueous solution are added thereto. The obtained aqueous solution is dripped into a mixed solution 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 are added to the obtained diazo solution, and the pH is maintained at 1.5 to 4.0 with a 15% sodium carbonate aqueous solution, and stirred for 8 hours to complete the coupling reaction. Thereafter, it is salted out with sodium chloride and filtered to obtain 200 parts of a wet cake of the trisazo compound represented by the formula (10).

[0229]

[0230] (Step 3)

[0231] 200 parts of the wet cake of the triazo compound represented by the obtained formula (10) are added to 500 parts of water, stirred to suspend it, and 25% sodium hydroxide is used to make it pH 9.0, and 17.3 parts of 40% sodium nitrite aqueous solution are added thereto. The obtained suspension is dripped into a mixed solution of 100 parts of water and 42 parts of 35% hydrochloric acid to prepare a diazo liquid. Next, 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid are added to 300 parts of water and dissolved in a 25% sodium hydroxide aqueous solution to become weakly alkaline. The previously obtained diazo liquid is maintained at pH 6.5 to 8.0 and dripped into this liquid, and stirred to complete the coupling reaction. Thereafter, it is salted out with sodium chloride, filtered, and dried, thereby obtaining 6.0 parts of the azo compound shown in compound example 1-47.

[0232] [Example S6]

[0233] 11.0 parts of the azo compound shown in Compound Example 1-42 was obtained in the same manner as in Example S5, except that 10.7 parts of 3-methylaniline in Step 1 of Example S5 was replaced by 12.1 parts of 2,5-dimethylaniline, and 13.7 parts of 2-methoxy-5-methylaniline in Step 2 of Example S5 was replaced by 15.3 parts of 2,5-dimethoxyaniline.

[0234] [Example S7]

[0235] 12.0 parts of the azo compound shown in Compound Example 1-22 was obtained in the same manner as in Example S1 except that 32.0 parts of 1,8-dihydroxynaphthalene-3,6-disulfonic acid in Step 1 of Example S1 was replaced with 44.2 parts of 1-hydroxy-3-(3-sulfopropoxy)naphthalene-3,6-disulfonic acid.

[0236] [Example S8]

[0237] 12.0 parts of the azo compound shown in Compound Example 1-15 was obtained in the same manner as in Example S1, except that 32.0 parts of 1,8-dihydroxynaphthalene-3,6-disulfonic acid in Step 1 of Example S1 was replaced by 33.4 parts of 1-hydroxy-8-methoxynaphthalene-3,6-disulfonic acid, and 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid in Step 3 of Example S1 was replaced by 37.5 parts of 1-hydroxy-6-(2,4-dimethoxyphenylamino)-3-naphthalenesulfonic acid.

[0238] [Example S9]

[0239] 12.5 parts of the azo compound shown in Compound Example 1-38 was obtained in the same manner as in Example S1 except that 32.0 parts of 1,8-dihydroxynaphthalene-3,6-disulfonic acid in Step 1 of Example S1 was replaced with 22.4 parts of 1-hydroxy-5-naphthalenesulfonic acid.

[0240] [Example S10]

[0241] 12.5 parts of the azo compound shown in Compound Example 1-18 was obtained in the same manner as in Example S1 except that 32.0 parts of 1,8-dihydroxynaphthalene-3,6-disulfonic acid in Step 1 of Example S1 was replaced with 22.4 parts of 1-hydroxy-3-naphthalenesulfonic acid.

[0242] [Example S11]

[0243] 13.5 parts of Compound Example 1-19 were obtained in the same manner as in Example S1 except that 32.0 parts of 1,8-dihydroxynaphthalene-3,8-disulfonic acid in Step 1 of Example S1 was replaced with 30.4 parts of 1-hydroxynaphthalene-3,8-disulfonic acid.

[0244] [Example S12]

[0245] 9.2 parts of the azo compound shown in Compound Example 1-36 was obtained in the same manner as in Example S1 except that 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid in Step 3 of Example S1 was replaced with 25.3 parts of 1-hydroxy-6-methylamino-3-naphthalenesulfonic acid.

[0246] [Example S13]

[0247] 11.3 parts of the azo compound represented by Compound Example 1-32 was obtained in the same manner as in Example S1 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 represented by the following formula (11).

[0248]

[0249] [Example S14]

[0250] 6.2 parts of the azo compound represented by Compound Example 1-35 was obtained in the same manner as in Example S1 except that 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid in Step 3 of Example S1 was replaced with 55.1 parts of the compound represented by the following formula (12).

[0251]

[0252] [Example S15]

[0253] 13.5 parts of the azo compound shown in Compound Example 1-7 was obtained in the same manner as in Example S1 except that 32.0 parts of 1,8-dihydroxynaphthalene-3,8-disulfonic acid in Step 1 of Example S1 was replaced with 30.4 parts of 1-hydroxynaphthalene-3,6-disulfonic acid.

[0254] [Example S16]

[0255] 10.0 parts of the azo compound shown in Compound Example 1-48 was obtained in the same manner as in Example S1, except that 15.0 parts of N-acetyl-1,4-phenylenediamine in Step 1 of Example S1 was replaced by 19.4 parts of N-acetyl-2-methyl-5-methoxy-1,4-phenylenediamine, 15.3 parts of 2,5-dimethoxyaniline in Step 2 of Example S1 was replaced by 12.1 parts of 2,5-dimethylaniline, and 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid in Step 3 of Example S1 was replaced by 34.5 parts of 1-hydroxy-6-(4-methoxyphenylamino)-3-naphthalenesulfonic acid.

[0256] [Example S17]

[0257] 10.0 parts of the azo compound shown in Compound Example 1-49 was obtained in the same manner as in Example S1, except that 15.3 parts of 2,5-dimethoxyaniline in Step 2 of Example S1 was replaced by 12.1 parts of 2,5-dimethylaniline, and 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid in Step 3 of Example S1 was replaced by 34.5 parts of 1-hydroxy-6-(4-methoxyphenylamino)-3-naphthalenesulfonic acid.

[0258] [Example S18]

[0259] 6.0 parts of the azo compound shown in Compound Example 1-34 was obtained in the same manner as in Example S1 except that 31.5 parts of 1-hydroxy-6-anilino-3-naphthalenesulfonic acid in Step 3 of Example S1 was replaced with 32.9 parts of 1-hydroxy-6-benzylamino-3-naphthalenesulfonic acid.

[0260] [Comparative Example S1]

[0261] (Step 1)

[0262] 15.0 parts of N-acetyl-1,4-phenylenediamine, which is available as a commercial product, is added to 200 parts of water, and after stirring, 42 parts of 35% hydrochloric acid and 17.3 parts of 40% sodium nitrite are added, and stirred for 1 hour to perform diazotization. 22.3 parts of 1-amino-7-naphthalenesulfonic acid are added to the obtained diazo liquid, and the pH is maintained at 3.5-6.0 with a 15% sodium carbonate aqueous solution, and stirred for 8 hours to complete the coupling reaction. Thereafter, it is salted out with sodium chloride and filtered to obtain 100 parts of a wet cake of the monoazo compound represented by formula (13).

[0263]

[0264] (Step 2)

[0265] 100 parts of the wet cake of the monoazo compound represented by the obtained formula (13) are added to 300 parts of water, stirred to suspend it, and 25% sodium hydroxide is used to make it pH 9.0, and 17.3 parts of a 40% sodium nitrite aqueous solution are added thereto. The obtained aqueous solution is dripped into a mixed solution of 200 parts of water and 42 parts of 35% hydrochloric acid to prepare a diazo liquid. Next, 32.0 parts of 1,8-dihydroxynaphthalene-3,6-disulfonic acid are added to 200 parts of water and dissolved in a 25% sodium hydroxide aqueous solution to become weakly alkaline. The previously obtained diazo liquid is maintained at pH 6.5 to 8.0 and dripped into this liquid, and stirred to complete the coupling reaction. Thereafter, it is salted out with sodium chloride, filtered, and dried, thereby obtaining 15.0 parts of the azo compound represented by the formula (14).

[0266]

[0267] [Comparative Example S2]

[0268] As the compound of Comparative Example 2, Compound Example (VI) (the following formula (15)) used in Example S1 described in Patent Document 2 was used.

[0269]

[0270] [Comparative Example S3]

[0271] CI Direct Blue 67 (the following formula (16)), a dichroic dye having a disazo structure and having the same color as that of Example S1, was used as the compound of Comparative Example S3.

[0272]

[0273] (Examples F1 to F18 and Comparative Examples F1 to F3: Preparation of Polarizing Film)

[0274] Polyvinyl alcohol having a thickness of 75 μm was immersed in a 45° C. aqueous solution (dye bath) having a concentration of 0.03% of each azo compound and 0.1% of sodium sulfate obtained in Examples S1 to S18 and Comparative Examples S1 to S3 for 4 minutes. The film was stretched 5 times in a 3% boric acid aqueous solution at 50° C., and washed and dried directly while being stretched to obtain a polarizing film.

[0275] The transmittance and polarization rate of the obtained polarizing film at the maximum absorption wavelength are shown in Table 1. The transmittance and polarization rate of the polarizing film at the maximum absorption wavelength are measured using a spectrophotometer (U-4100 manufactured by Hitachi, Ltd.). The single transmittance (Ts) represents the transmittance of the maximum absorption wavelength obtained by measuring the polarizing film alone, the parallel transmittance (Tp) represents the transmittance of the maximum absorption wavelength obtained by measuring two polarizing films in parallel, the orthogonal transmittance (Tc) represents the transmittance of the maximum absorption wavelength obtained by measuring two polarizing films in parallel, the polarization rate (ρ) is the value calculated by formula (I), and the contrast (CR) is calculated by dividing the parallel transmittance by the orthogonal transmittance.

[0276] Polarization ratio (%) = 100 × [(Tp-Tc) / (Tp+Tc)] 1 / 2 (I)

[0277] [Table 1]

[0278]

[0279] As shown in Table 1, the polarizing films made using the azo compounds of Examples S1 to S18 all have high polarization rates. Specifically, the polarizing films of Examples F1 to F18 exhibit a polarization rate of more than 97% at a single body transmittance of about 44%, while the polarizing films of Comparative Examples F1 to F3 cannot obtain a polarization rate of 97%. In addition, as an indicator of image quality, in the comparison of the brightness difference between white display and black display, the polarizing films of Examples F1 to F18 are still 47 even if they are lower, while the polarizing films of Comparative Examples F1 to F3 are only 25 at most, which shows that the polarizing film of the present invention has a high contrast ratio of almost twice as high.

[0280] (Example P1: Preparation of Neutral Gray Polarizing Plate)

[0281] A polarizing film was prepared in the same manner as in Example F1 except that a 45°C aqueous solution of the compound of Example S1 obtained in Example S1 with a concentration of 0.3%, 0.15% CI Direct Red 81, 0.1% CI Direct Orange 39, and 0.1% Glauber's salt was used as a dye bath. The obtained polarizing film had a single-plate average transmittance of 42% in the range of 430 to 640 nm and an average transmittance of 0.1% in the orthogonal direction, and had a high degree of polarization. A triacetyl cellulose film (TAC film: manufactured by Fujifilm, trade name TD-80U) was laminated on both sides of the polarizing film via an adhesive of a polyvinyl alcohol aqueous solution, and glass was attached using a pressure-sensitive adhesive to obtain a dye-based polarizing plate (neutral gray polarizing plate) in which TAC / polarizing film / TAC / glass were laminated in sequence.

[0282] The neutral gray polarizing plate obtained in Example P1 has no change in the average transmittance of a single plate after 500 hours in an environment of 105°C and after 500 hours under conditions of 90% relative humidity and 80°C, and exhibits long-term durability under high temperature and high humidity conditions. In addition, in a xenon lamp light resistance test (SX-75 manufactured by Suga Test Instruments), the average transmittance of the neutral gray polarizing plate of Example P1 has no change even after 200 hours under conditions of 60W and an ambient temperature of 50°C, and has excellent light resistance to long-term exposure to light. These results show that the neutral gray polarizing plates of Example P1 are all high-performance dye-based polarizing plates with excellent polarization performance and durability (moisture resistance, heat resistance, and light resistance).

[0283] [Industrial Applicability]

[0284] The polarizing film or polarizing plate of the present invention is provided with a protective layer or a functional layer and a transparent support such as glass, crystal, sapphire, etc. as required, and is suitable for liquid crystal projectors, computers, clocks, notebook computers, word processors, liquid crystal televisions, polarizing lenses, polarizing glasses, car navigation, and indoor and outdoor measuring machines or displays, etc. In particular, the polarizing film or polarizing plate of the present invention is suitable for use in organic electroluminescence, etc., in addition to liquid crystal display devices, such as reflective liquid crystal display devices, semi-transmissive liquid crystal display devices, and liquid crystal display devices.

Claims

1. A polarizing film comprising an azo compound represented by the following formula (2) or a salt thereof; In formula (2), Ra2 is a hydroxyl group, Ra1 is a hydrogen atom, a hydroxyl group, a C1-4 alkoxy group or a C1-4 alkoxy group having a sulfonic acid group, either Ab1 or Ab2 represents a sulfonic acid group, a carboxyl 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 sulfonic acid group, a carboxyl 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 sulfonic acid group, a C1-4 alkoxy group having a sulfonic acid group or an amino group which may have a substituent, h represents 0 or 1, and Xb1 represents an amino group which may have a substituent. An amino group having 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, wherein the substituent S is one substituent or a plurality of substituents which may be independently selected and is selected from the group consisting of a C1 to 4 alkyl group which may further have a substituent, a C1 to 4 alkoxy group, a sulfonic acid group, an amino group, a C1 to 4 alkylamino group, a hydroxyl group, a carboxyl group, and a carboxyethylamino group, and is different from the above-mentioned Ra1, Ra2, Ab1, and Ab2.

2. The polarizing film according to claim 1, wherein The azo compound or its salt represented by the above formula (2) is an azo compound or its salt represented by the following formula (4); In the above formula (4), Ra1, Ra2, Ab1, Ab2, Rb1 to Rb6, h, and Xb1 respectively represent the same meanings as in formula (2).

3. The polarizing film according to claim 1, wherein The azo compound or its salt represented by the above formula (2) is an azo compound or its salt represented by the following formula (5); In the above formula (5), Ra1, Ab1, Rb1 to Rb6, h, and Xb1 respectively represent the same meanings as in formula (2).

4. The polarizing film according to claim 1, wherein The azo compound or its salt represented by the above formula (2) is an azo compound or its salt represented by the following formula (6); In the above formula (6), Ra1, Ab1, Rb1 to Rb6, h, and Xb1 respectively represent the same meanings as in formula (2).

5. The polarizing film according to claim 4, wherein: In the above formula (6), Ra1 is a hydroxyl group. The polarizing film according to claim 1 , 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 . The polarizing film according to claim 1 , comprising one or more organic dyes other than the azo compound or the salt thereof represented by any one of formulas (2) and (4) to (6). 9 . The polarizing film according to claim 6 , which has a neutral gray color. The polarizing film according to claim 8 , which has a neutral gray color. 11 . A polarizing plate comprising a transparent protective film provided on one or both surfaces of the polarizing film according to claim 6 . 12 . A display device comprising the polarizing film according to claim 1 or the polarizing plate according to claim 11 .

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