JP2022167782A - Polarizing plate - Google Patents

Abstract

To provide a polarizing plate which offers improved durability of a polarizer and a retardation layer.SOLUTION: A polarizing plate is provided, comprising a polarizer containing a dichroic azo dye, a cured product layer of a polyvinyl alcohol-based resin composition, and a retardation layer containing a cured product of a polymerizable liquid crystal compound, directly laminated on top of each other in the described order.SELECTED DRAWING: Figure 1

Description

The present invention relates to a polarizing plate, and also relates to an image display device including this polarizing plate.

2. Description of the Related Art Conventionally, in an image display device, a method has been adopted in which an optical layered body having antireflection performance is arranged on the viewing side of an image display panel to suppress deterioration in visibility due to reflection of extraneous light. A circularly polarizing plate including a polarizer and a retardation layer is known as an optical laminate having antireflection performance.

When the image display device is used in a harsh environment, there is a problem that the optical properties of the polarizer tend to deteriorate. JP-A-2013-105036 describes that a polarizer having excellent durability can be obtained by increasing the boric acid content in the polarizer.

JP 2013-105036 A

In addition, the optical properties of the retardation layer tend to deteriorate under harsh environments. An object of the present invention is to provide a polarizing plate in which the durability of both the polarizer and the retardation layer is improved, and an image display device having the same.

The present invention provides a polarizing plate and an image display device exemplified below.
[1] A polarizing plate in which a polarizer containing a dichroic azo dye, a cured product layer of a polyvinyl alcohol-based resin composition, and a retardation layer containing a cured product of a polymerizable liquid crystal compound are laminated in this order in contact with each other. .
[2] The polarizing plate according to [1], wherein the polyvinyl alcohol-based resin composition contains acetoacetyl group-modified polyvinyl alcohol.
[3] The polarizing plate according to [1] or [2], wherein the polyvinyl alcohol resin contained in the polyvinyl alcohol resin composition has a saponification degree of 85 mol % or more and 100 mol % or less.
[4] The polarizing plate according to any one of [1] to [3], wherein the polyvinyl alcohol resin contained in the polyvinyl alcohol resin composition has a polymerization degree of 1000 or more and 5000 or less.
[5] Any one of [1] to [4], wherein the polyvinyl alcohol-based resin composition does not contain an aldehyde compound, or contains 8.0 parts by mass or less of an aldehyde compound with respect to 100 parts by mass of the polyvinyl alcohol-based resin. The polarizing plate described in .
[6] The polarizing plate according to any one of [1] to [5], wherein the retardation layer includes a quarter-wave plate layer.
[7] An image display device comprising the polarizing plate according to any one of [1] to [6].

ADVANTAGE OF THE INVENTION According to this invention, the durability of both a polarizer and a retardation layer improved, and the image display apparatus provided with the polarizing plate and the same can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional drawing which shows typically an example of the polarizing plate of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. In all the drawings below, the scale of each component is adjusted appropriately to facilitate understanding, and the scale of each component shown in the drawings does not necessarily match the scale of the actual component.

<Polarizing plate>
A polarizing plate according to the present invention will be described with reference to FIG. The polarizing plate 100 according to the present invention includes a polarizer 10 containing a dichroic azo dye, a cured product layer of a polyvinyl alcohol-based resin composition (also referred to herein as a “first cured product layer”) 20, A retardation layer 40 containing a cured product of a polymerizable liquid crystal compound is laminated in contact with this order. The polarizing plate 100 is, for example, a circularly polarizing plate including a linear polarizer and a retardation layer. In this specification, circularly polarizing plates include elliptically polarizing plates. A circularly polarizing plate can have an antireflection function in an image display device.

The dichroic azo dye contained in the polarizer has high linearity and is suitable for making a polarizer with excellent polarizing performance. properties can be degraded. Especially in a high-temperature environment, this diffusion is remarkable, and there is a problem that the polarizer is easily deteriorated. A polarizer containing a dichroic azo dye and a first cured layer, which is a cured layer of a polyvinyl alcohol resin composition, are in contact with each other. ) can be suppressed, and the durability of the polarizer can be improved. The polarizing plate according to the present invention exhibits a change of less than 1.0 in the degree of polarization of the polarizing plate even when placed in a high-temperature environment of, for example, 85°C.

On the other hand, a retardation layer containing a cured product of a polymerizable liquid crystal compound has a problem that the monomer easily diffuses in an environment such as high temperature and high humidity, and the retardation layer easily deteriorates. By laminating the retardation layer containing the cured product of the polymerizable liquid crystal compound and the first cured product layer in contact with each other, the diffusion of the monomer can be suppressed, and the durability of the retardation layer can be improved. . When the retardation layer is attached to the polarizer or the first cured product layer with the pressure-sensitive adhesive layer, it is difficult to suppress the diffusion of the monomer from the retardation layer. Even when the polarizing plate according to the present invention is placed in a high-temperature and high-humidity environment with a temperature of 65° C. and a relative humidity of 90%, the amount of change in the retardation value at a wavelength of 550 nm of the quarter-wave plate is 2. less than 0.5 nm.

The polarizing plate may have, for example, a square shape in a plan view, preferably a square shape having long sides and short sides, more preferably a rectangle. Each layer constituting the polarizing plate may have rounded corners, notched edges, or perforated edges.

A polarizing plate can be used, for example, in an image display device or the like. The image display device is not particularly limited, and examples thereof include organic electroluminescence (organic EL) display devices, inorganic electroluminescence (inorganic EL) display devices, liquid crystal display devices, and electroluminescence display devices.

[Polarizer]
The polarizer may be a stretched film to which a dichroic azo dye is adsorbed, or a cured product of a composition containing a polymerizable liquid crystal compound and a dichroic azo dye.

As a stretched film to which a dichroic azo dye is adsorbed, for example, a polyvinyl alcohol (hereinafter sometimes abbreviated as "PVA") resin film is dyed with a dichroic dye containing a dichroic azo dye, and a uniaxial film is obtained. A polarizer obtained by stretching can be used.

A polyvinyl alcohol-based resin is obtained by saponifying a polyvinyl acetate-based resin. Polyvinyl acetate-based resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith. Other monomers copolymerizable with vinyl acetate include, for example, unsaturated carboxylic acid-based compounds, olefin-based compounds, vinyl ether-based compounds, unsaturated sulfone-based compounds, and (meth)acrylamide-based compounds having an ammonium group. .

The degree of saponification of the polyvinyl alcohol resin is generally about 85 mol % or more and 100 mol % or less, preferably 98 mol % or more. The polyvinyl alcohol-based resin may be modified, and aldehyde-modified polyvinyl formal, polyvinyl acetal, and the like can also be used. The average degree of polymerization of the polyvinyl alcohol resin is usually 1000 or more and 10000 or less, preferably 1500 or more and 5000 or less. The average degree of polymerization of the polyvinyl alcohol-based resin can be determined according to JIS K 6726 (1994). If the average degree of polymerization is less than 1,000, it is difficult to obtain desirable polarizing performance, and if it exceeds 10,000, film workability may be poor.

As another method for producing a linear polarizing plate containing a polyvinyl alcohol resin film, first, a base film is prepared, a solution of a resin such as a polyvinyl alcohol resin is applied on the base film, and drying is performed to remove the solvent. and forming a resin layer on the substrate film. A primer layer can be formed in advance on the surface of the substrate film on which the resin layer is to be formed. Examples of the material for the primer layer include a resin obtained by cross-linking a hydrophilic resin used for a linear polarizer.

Examples of base films include cyclopolyolefin resin films; cellulose acetate resin films containing resins such as triacetyl cellulose and diacetyl cellulose; polyester resin films containing resins such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; Examples of thermoplastic resin films known in the art include polycarbonate resin films; (meth)acrylic resin films; polypropylene resin films. The thickness of the base film is usually 100 μm or less, preferably 80 μm or less, more preferably 60 μm or less, even more preferably 40 μm or less, and even more preferably 30 μm or less, from the viewpoint of thinning. , and is usually 5 μm or more, preferably 10 μm or more.

A hard coat layer may be formed on the thermoplastic resin film. The hard coat layer may be formed on one side of the thermoplastic resin film, or may be formed on both sides. By providing a hard coat layer, a thermoplastic resin film having improved hardness and scratch resistance can be obtained.

Next, the amount of solvent such as moisture in the resin layer is adjusted as necessary, then the base film and the resin layer are uniaxially stretched, and then the resin layer is dyed with a dichroic dye to remove the dichroic dye. It is adsorbed and oriented on the resin layer. If necessary, the resin layer on which the dichroic dye is adsorbed and oriented is treated with an aqueous boric acid solution, and a washing step is performed to wash off the aqueous boric acid solution. As a result, a polarizer, which is a resin layer in which the dichroic dye is adsorbed and oriented, is manufactured. A known method can be adopted for each step.

The uniaxial stretching of the substrate film and the resin layer may be performed before dyeing, during dyeing, or during boric acid treatment after dyeing. Stretching may be performed. The base film and the resin layer may be uniaxially stretched in the MD direction (film transport direction). In this case, they may be uniaxially stretched between rolls with different peripheral speeds, or uniaxially stretched using hot rolls. You may Moreover, the base film and the resin layer may be uniaxially stretched in the TD direction (the direction perpendicular to the film transport direction), in which case a so-called tenter method can be used. The stretching of the substrate film and the resin layer may be dry stretching performed in the atmosphere, or wet stretching performed with the resin layer swollen with a solvent. In order to exhibit the performance of the polarizer, the draw ratio is 4 times or more, preferably 5 times or more, and particularly preferably 5.5 times or more. Although there is no particular upper limit for the draw ratio, it is preferably 8 times or less from the viewpoint of suppressing breakage and the like.

The polarizer produced by the above method may be used as a linear polarizer with the substrate film peeled off or together with the substrate film. According to the above method, the base film can be peeled off, so that the thickness of the linear polarizer can be reduced.

The thickness of the polarizer containing the polyvinyl alcohol resin film is, for example, 2 μm or more and 40 μm or less. The thickness of the polarizer may be 5 μm or more, 20 μm or less, 15 μm or less, or even 10 μm or less.

The polarizer is formed, for example, by applying a composition containing a polymerizable liquid crystal compound and a dichroic azo dye onto an alignment film formed on a substrate film, and polymerizing and curing the polymerizable liquid crystal compound. can also A polarizer may be formed by coating a composition containing a polymerizable liquid crystal compound and a dichroic azo dye on a substrate film to form a coating film, and stretching the coating film together with the substrate film. good. The material and thickness of the base film may be the same as the material and thickness of the thermoplastic resin film described above. The polarizer may be used as a linear polarizer without peeling and removing the base film, or may be used as a linear polarizer by peeling and removing the base film from the polarizer.

A polymerizable liquid crystal compound is a compound having a polymerizable reactive group and exhibiting liquid crystallinity. The polymerizable reactive group is a group that participates in a polymerization reaction, and is preferably a photopolymerizable reactive group. A photopolymerizable reactive group refers to a group that can participate in a polymerization reaction by an active radical generated from a photopolymerization initiator, an acid, or the like. Photopolymerizable functional groups include vinyl group, vinyloxy group, 1-chlorovinyl group, isopropenyl group, 4-vinylphenyl group, acryloyloxy group, methacryloyloxy group, oxiranyl group and oxetanyl group. Among them, an acryloyloxy group, a methacryloyloxy group, a vinyloxy group, an oxiranyl group and an oxetanyl group are preferred, and an acryloyloxy group is more preferred. The type of polymerizable liquid crystal compound is not particularly limited, and rod-like liquid crystal compounds, discotic liquid crystal compounds, and mixtures thereof can be used. The liquid crystallinity of the polymerizable liquid crystal compound may be either thermotropic liquid crystal or lyotropic liquid crystal, and the phase order structure may be nematic liquid crystal or smectic liquid crystal.

A composition containing a polymerizable liquid crystal compound and a dichroic dye, and a method for producing a polarizer using this composition are disclosed in JP-A-2013-37353, JP-A-2013-33249, and JP-A-2017-83843. Examples include those described in the publications. The composition for forming the polarizer contains additives such as a solvent, a polymerization initiator, a cross-linking agent, a leveling agent, an antioxidant, a plasticizer, and a sensitizer, in addition to the polymerizable liquid crystal compound and the dichroic dye. may further include Each of these components may be used alone or in combination of two or more.

The polymerization initiator is a compound capable of initiating the polymerization reaction of the polymerizable liquid crystal compound, and from the viewpoint of being able to initiate the polymerization reaction under lower temperature conditions, a photopolymerization initiator is preferable. Specifically, photopolymerization initiators capable of generating active radicals or acids by the action of light may be mentioned, and among these, photopolymerization initiators capable of generating radicals by the action of light are preferred. The content of the polymerization initiator is preferably 1 part by mass or more and 10 parts by mass or less, more preferably 3 parts by mass or more and 8 parts by mass or less with respect to 100 parts by weight of the total amount of the polymerizable liquid crystal compound. Within this range, the reaction of the polymerizable group proceeds sufficiently, and the alignment state of the liquid crystal compound is easily stabilized.

The thickness of the polarizer produced by the above method is usually 10 μm or less, preferably 0.5 μm or more and 8 μm or less, and more preferably 1 μm or more and 5 μm or less.

The polarizer may be laminated with the first cured material layer while having the alignment film. As the alignment film, a photo-alignment film is preferable from the viewpoints of the accuracy and quality of the alignment angle, and the water resistance and flexibility of the polarizing plate. The thickness of the alignment film is preferably 10 nm or more and 5000 nm, more preferably 1000 nm or less, may be 500 nm or less, or may be 300 nm or less.

(Dichroic azo dye)
Dichroic azo dyes include monoazo dyes, bisazo dyes, trisazo dyes, tetrakis azo dyes and stilbene azo dyes, and bisazo dyes and trisazo dyes are preferred. For example, compounds represented by formula (I) (hereinafter, Also referred to as "compound (I)").
K ¹ (-N=N-K ² ) _p -N=N-K ³ (I)
[In formula (I), K ¹ and K ³ are each independently a phenyl group optionally having a substituent, a naphthyl group optionally having a substituent, or a represents a good monovalent heterocyclic group. K ² is a p-phenylene group optionally having substituents, a naphthalene-1,4-diyl group optionally having substituents or a divalent heterocyclic ring optionally having substituents represents a group. p represents an integer of 1 to 4; When p is an integer of ² or more, multiple K2 may be the same or different. -N=N-bonds may be replaced with -C=C-, -COO-, -NHCO- and -N=CH-bonds within the range of absorption in the visible region. ]

Examples of monovalent heterocyclic groups include groups obtained by removing one hydrogen atom from heterocyclic compounds such as quinoline, thiazole, benzothiazole, thienothiazole, imidazole, benzimidazole, oxazole, and benzoxazole. The divalent heterocyclic group includes a group obtained by removing two hydrogen atoms from the above heterocyclic compound.

As a substituent optionally possessed by a phenyl group, a naphthyl group and a monovalent heterocyclic group for K ¹ and K ³ , and a p-phenylene group, a naphthalene-1,4-diyl group and a divalent heterocyclic group for K ² is an alkyl group having 1 to 4 carbon atoms; an alkoxy group having 1 to 4 carbon atoms such as a methoxy group, an ethoxy group and a butoxy group; a fluorinated alkyl group having 1 to 4 carbon atoms such as a trifluoromethyl group; a cyano group; Nitro group; halogen atom; amino group, diethylamino group, substituted or unsubstituted amino group such as pyrrolidino group (substituted amino group is an amino group having one or two alkyl groups having 1 to 6 carbon atoms, or two It means an amino group in which substituted alkyl groups are bonded together to form an alkanediyl group having 2 to 8 carbon atoms, and an unsubstituted amino group is —NH ₂ .).

［式（Ｉ－１）～（Ｉ－８）中、
Ｂ１～Ｂ３０は、互いに独立して、水素原子、炭素数１～６のアルキル基、炭素数１～４のアルコキシ基、シアノ基、ニトロ基、置換又は無置換のアミノ基（置換アミノ基及び無置換アミノ基の定義は前記のとおり）、塩素原子又はトリフルオロメチル基を表わす。
ｎ１～ｎ４は、互いに独立に０～３の整数を表わす。
ｎ１が２以上である場合、複数のＢ^２は互いに同一でも異なっていてもよく、
ｎ２が２以上である場合、複数のＢ^６は互いに同一でも異なっていてもよく、
ｎ３が２以上である場合、複数のＢ^９は互いに同一でも異なっていてもよく、
ｎ４が２以上である場合、複数のＢ^１４は互いに同一でも異なっていてもよい。］ Among compounds (I), compounds represented by any one of the following formulas (I-1) to (I-8) are preferred.

[In the formulas (I-1) to (I-8),
B1 to B30 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a cyano group, a nitro group, a substituted or unsubstituted amino group (substituted amino group and unsubstituted The definition of the substituted amino group is as described above), represents a chlorine atom or a trifluoromethyl group.
n1 to n4 each independently represents an integer of 0 to 3;
When n1 is ² or more, the plurality of B2 may be the same or different,
When n2 is 2 or more, the plurality of ^B6 may be the same or different,
When n3 is ² or more, multiple B9 may be the same or different,
When n4 is 2 or more, the plurality of ^B14 may be the same or different. ]

The weight average molecular weight of the dichroic azo dye is usually 300 or more and 2000 or less, preferably 400 or more and 1000 or less. When the weight average molecular weight of the dichroic azo dye is equal to or less than the above upper limit, the dichroic azo dye tends to move and diffuse out of the polarizer. Even in such a case, a polarizing plate having a configuration in which a polarizer containing a dichroic azo dye and a first cured product layer, which is a cured product layer of a polyvinyl alcohol resin composition, are in contact with each other in this order is a dichroic The diffusion (especially thermal diffusion) of the polar azo dye can be suppressed, and the durability of the polarizer can be improved.

When the polarizer contains a polymerizable liquid crystal compound, the content of the dichroic azo dye is, for example, 0.1 parts by mass or more and 50 parts by mass or less, preferably 0.1 part by mass or more, relative to 100 parts by mass of the polymerizable liquid crystal compound. It is 1 part by mass or more and 20 parts by mass or less, more preferably 0.1 part by mass or more and 12 parts by mass or less. When the content of the dichroic dye is within this range, the alignment of the polymerizable liquid crystal compound is less likely to be disturbed, and a polarizer having a high degree of alignment order can be obtained.

[First cured layer]
The first cured layer is a cured layer of a polyvinyl alcohol-based resin composition. The first cured product layer, which is a cured product layer of a polyvinyl alcohol-based resin composition, can prevent diffusion of the dichroic azo dye from the polarizer. The first cured layer, which is a cured layer of a polyvinyl alcohol-based resin composition, protects the surface of the polarizer and has excellent heat resistance. The first cured material layer can prevent diffusion of unpolymerized monomers from the retardation layer. The first cured product layer usually has adhesiveness to the polarizer and the retardation layer.

The polyvinyl alcohol resin contained in the polyvinyl alcohol resin composition includes partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, methylol group-modified polyvinyl alcohol, amino group-modified polyvinyl alcohol, A modified polyvinyl alcohol-based resin such as modified polyvinyl alcohol may also be included. The polyvinyl alcohol-based resin contained in the polyvinyl alcohol-based resin composition preferably contains acetoacetyl group-modified polyvinyl alcohol from the viewpoint of suppressing deterioration of the polarizer. A commercially available polyvinyl alcohol-based resin may be used as the polyvinyl alcohol-based resin contained in the polyvinyl alcohol-based resin composition. Commercially available products include, for example, partially saponified polyvinyl alcohol “PVA-403” sold by Kuraray Co., Ltd., carboxyl group-modified partially saponified polyvinyl alcohol “KL-506” and “KL-318”, Mitsubishi Examples include acetoacetyl group-modified partially saponified polyvinyl alcohol “Z-100”, “Z-200” and “Z-300” sold by Chemical Co., Ltd.

The degree of saponification of the polyvinyl alcohol resin contained in the polyvinyl alcohol resin composition is usually about 85 mol% or more and 100 mol% or less, preferably 90 mol% or more, and may be 95 mol% or more. , 98 mol % or more.

The average degree of polymerization of the polyvinyl alcohol-based resin contained in the polyvinyl alcohol-based resin composition is usually 1000 or more and 5000 or less, preferably 3000 or less, may be 2000 or less, or may be 1500 or less. When the average degree of polymerization is within this range, the deterioration of the polarizer can be suppressed satisfactorily.

The content of the polyvinyl alcohol-based resin contained in the polyvinyl alcohol-based resin composition is preferably 85% by mass or more, more preferably 90% by mass or more, more preferably 90% by mass or more, based on the mass of the solid content of the polyvinyl alcohol-based resin composition. is 95% by mass or more. All the solid content of the polyvinyl alcohol-based resin composition may be polyvinyl alcohol-based resin (that is, 100% by mass). The solid content of the polyvinyl alcohol-based resin composition means the total amount of components excluding the solvent from the polyvinyl alcohol-based resin composition when the polyvinyl alcohol-based resin composition contains a solvent.

It is preferable that the polyvinyl alcohol-based resin composition contains a solvent because the coatability and handleability when producing a cured product of the polyvinyl alcohol-based resin composition are improved. Examples of the solvent in the ribyl alcohol resin composition include water or a mixed solvent of water and a hydrophilic organic solvent (for example, an alcohol solvent, an ether solvent, an ester solvent, etc.). When the polyvinyl alcohol-based resin composition contains a solvent, the solid content is preferably 1% by mass or more and 30% by mass or less, more preferably 2% by mass or more and 10% by mass or less.

The polyvinyl alcohol-based resin composition may contain additives such as stabilizers, antioxidants, antistatic agents, UV absorbers, surface conditioners and cross-linking agents, if necessary. An additive can be used individually or in combination of 2 or more types. The content of the additive is preferably about 0.1% by mass or more and 10% by mass or less relative to the mass of the solid content of the polyvinyl alcohol resin composition.

Examples of cross-linking agents include amine compounds, aldehyde compounds, methylol compounds, water-soluble epoxy resins, isocyanate compounds, polyvalent metal salts and the like. When a polyvinyl alcohol-based resin is used as an adhesive component, aldehyde compounds such as glyoxal, methylol compounds such as methylol melamine, water-soluble epoxy resins, and the like can be used as cross-linking agents. The water-soluble epoxy resin is, for example, a polyamide epoxy resin obtained by reacting epichlorohydrin with a polyamide polyamine which is a reaction product of a polyalkylene polyamine such as diethylenetriamine and triethylenetetramine and a dicarboxylic acid such as adipic acid. can be done. An example of a commercially available water-soluble epoxy resin is "Sumireze Resin (registered trademark) 650 (30)" sold by Taoka Chemical Co., Ltd. The polyvinyl alcohol-based resin composition may not contain a cross-linking agent. From the viewpoint of suppressing deterioration of the polarizer, the polyvinyl alcohol-based resin composition preferably has an aldehyde compound content of 8.0 parts by mass or less, more preferably 5 parts by mass with respect to 100 parts by mass of the polyvinyl alcohol-based resin. .0 parts by mass or less, and may not contain an aldehyde compound.

The polyvinyl alcohol-based resin composition can be prepared by dissolving the polyvinyl alcohol-based resin and, if necessary, additives and the like in a solvent. A first cured layer, which is a cured layer of the polyvinyl alcohol resin composition, can be obtained by coating the polyvinyl alcohol resin composition on one surface of the polarizer and removing the solvent by drying.

The thickness of the first cured product layer is preferably 0.1 μm or more and 10 μm or less, more preferably 0.3 μm or more and 2 μm or less. When the thickness of the first cured product layer is within the above range, the diffusion of the dichroic dye from the polarizer can be effectively suppressed and the thickness of the polarizing plate can be reduced.

[Retardation layer]
The retardation layer may be one layer or two or more layers. The retardation layer may have a substrate film for supporting the retardation layer, an adhesive layer for laminating a plurality of retardation layers, and the like. The retardation layer may further include an alignment film. The retardation layer preferably includes a quarter-wave plate layer, and may further include at least one of a half-wave plate layer and a positive C layer. When the retardation layer includes a half-wave plate layer, a half-wave plate layer and a quarter-wave plate layer are laminated in order from the linear polarizer side. When the retardation layer includes a positive C layer, a quarter wavelength plate layer and a positive C layer may be laminated in order from the linear polarizer side, and a positive C layer and a quarter wavelength in order from the linear polarizer side Board layers may be laminated. The thickness of the retardation layer is, for example, 0.1 μm or more and 10 μm or less, preferably 0.5 μm or more and 8 μm or less, and more preferably 1 μm or more and 6 μm or less.

The retardation layer contains a cured product of a polymerizable liquid crystal compound. The retardation layer can be formed by coating a base film with a composition containing a polymerizable liquid crystal compound and curing the composition. An alignment film may be formed between the substrate film and the coating layer. The material and thickness of the base film may be the same as the material and thickness of the thermoplastic resin film. The retardation layer may be incorporated into the polarizing plate in a form having an alignment film and a base film. It is preferable that the surface of the retardation layer facing the polarizer is a layer containing a cured polymerizable liquid crystal compound. The surface of the retardation layer facing the polarizer may be the surface of the layer exhibiting retardation, or may be an alignment film.

The retardation layer may include a layer formed from a resin film in addition to the layer containing the cured product of the polymerizable liquid crystal compound. The resin film may be the thermoplastic resin film described above.

A liquid crystal layer exhibiting a retardation can be formed using a known liquid crystal compound. The type of liquid crystal compound contained in the composition containing a polymerizable liquid crystal compound is not particularly limited, and rod-like liquid crystal compounds, discotic liquid crystal compounds, and mixtures thereof can be used. A composition containing a polymerizable liquid crystal compound may contain a polymer liquid crystal compound. As the liquid crystal compound, for example, JP-A-11-513019, JP-A-2005-289980, JP-A-2007-108732, JP-A-2010-244038, JP-A-2010-31223, JP-A-2010 -270108, JP-A-2011-6360, JP-A-2011-207765, JP-A-2016-81035, International Publication No. 2017/043438 and the liquid crystal compounds described in JP-A-2011-207765 mentioned.

A composition containing a polymerizable liquid crystal compound may contain, in addition to the liquid crystal compound, a polymerization initiator, a polymerizable monomer, a surfactant, a solvent, an adhesion improver, a plasticizer, an alignment agent, and the like. Examples of the method for applying the composition containing the polymerizable liquid crystal compound include known methods such as a die coating method. As a method for curing a composition containing a polymerizable liquid crystal compound, a known method such as irradiating with an active energy ray (for example, ultraviolet rays) can be used.

A polarizing plate in which a polarizer and a retardation layer are arranged such that the absorption axis of the polarizer and the slow axis of the retardation layer form a predetermined angle have an antireflection function, that is, function as a circular polarizer. can. When the retardation layer includes a quarter-wave plate layer, the angle between the absorption axis of the polarizer and the slow axis of the quarter-wave plate layer can be 45°±10°. The retardation layer may have normal wavelength dispersion or reverse wavelength dispersion. The quarter-wave plate layer preferably has reverse wavelength dispersion.

The alignment film has an alignment regulating force for aligning the polymerizable liquid crystal compound contained in the liquid crystal layer exhibiting the retardation formed on these alignment films in a desired direction. Examples of the alignment film include an alignment polymer film formed of an alignment polymer, a photo-alignment polymer film formed of a photo-alignment polymer, and a groove alignment film having an uneven pattern or a plurality of grooves on the film surface. can be done. The thickness of the alignment film is usually 0.01 μm or more and 10 μm or less, preferably 0.01 μm or more and 5 μm or less.

The oriented polymer film can be formed by coating a substrate film with a composition in which an oriented polymer is dissolved in a solvent, removing the solvent, and performing a rubbing treatment as necessary. The orientation regulating force can be arbitrarily adjusted by the surface state of the oriented polymer and rubbing conditions.

A photo-alignable polymer film can be formed by applying a composition containing a polymer having a photoreactive group or a monomer and a solvent to a substrate film and irradiating polarized light. In this case, the orientation regulating force can be arbitrarily adjusted by the polarized light irradiation conditions for the photo-orientable polymer.

The groove alignment film can be formed, for example, by exposing the surface of a photosensitive polyimide film through an exposure mask having pattern-shaped slits and developing the film to form an uneven pattern. A method of forming an uncured film of an energy ray-curable resin, transferring this film to a substrate film and curing it, forming an uncured layer of an active energy ray-curable resin on a substrate film, and applying Alternatively, it can be formed by a method of forming unevenness by pressing a roll-shaped master plate having unevenness and hardening it.

<Method for manufacturing polarizing plate>
A method for manufacturing the polarizing plate is not particularly limited. In one embodiment of the method for producing a polarizing plate, a polyvinyl alcohol-based resin composition is applied to the surface of a polarizer, a retardation layer is laminated thereon, and then the polyvinyl alcohol-based resin composition is cured to obtain a first cured product. It has a step of forming a layer.

<Image display device>
An image display device includes an image display panel and the polarizing plate described above. In the image display device, the polarizing plate can be arranged, for example, on the front surface (viewing side) of the image display panel. The image display panel is not particularly limited, and examples thereof include a liquid crystal display panel, an organic electroluminescence (organic EL) display panel, an inorganic electroluminescence (inorganic EL) display panel, a plasma display panel, and a field emission display panel. An image display device may be configured by arranging a circularly polarizing plate on the viewing side of the organic EL display device.

The image display device according to the present invention can be used as mobile devices such as smartphones and tablets, televisions, digital photo frames, electronic signboards, measuring instruments and gauges, office equipment, medical equipment, computing equipment, and the like. The image display device according to the present invention has excellent durability even when used in a harsh environment.

EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. In this example, a polarizing plate was produced using the following polarizer, first cured product layer and retardation layer.

<Preparation of laminate of Example 1>
[Preparation of polarizer with base film]
A roll-shaped release polyethylene terephthalate (PET) film with a film width of 800 mm (“FF-50” manufactured by Unitika Ltd., single-sided release-treated PET film, supporting substrate thickness: 50 μm) was used as the base film. A 3% by mass aqueous solution of the water-soluble polymer (1) was continuously applied to this release-treated surface using a slot die coater and dried at 100° C. for 2 minutes to obtain a transparent resin consisting of a film of the water-soluble polymer (1) with a thickness of 1 μm. Layer A (diffusion prevention layer A) was formed.

Water-soluble polymer (1) consisted of the following structural units.

Water-soluble polymer (1) was synthesized as follows. In 400 g of dimethyl sulfoxide, 20 g of polyvinyl alcohol (manufactured by Wako Pure Chemical Industries, Ltd.) having a molecular weight of 1000, 0.55 mg of N,N-dimethyl-4-aminopyridine as a nucleophile, and 4.6 g of triethylamine are dissolved and stirred. The temperature was raised to 60° C. while heating. Thereafter, a solution of 10.5 g of methacrylic anhydride dissolved in 50 g of dimethyl sulfoxide was added dropwise over 1 hour, followed by heating and stirring at 60° C. for 14 hours. After cooling the reaction solution to room temperature, 481 g of methanol was added and stirred to prepare a solution in which the ratio (mass) of the reaction solution and methanol was 1:1. 1500 mL of acetone was gradually added to this solution to crystallize the water-soluble polymer (1) by a crystallization method. The resulting solution containing white crystals was filtered, washed with acetone, and dried in vacuum to obtain 20.2 g of water-soluble polymer (1).

After performing a plasma treatment on the surface of the transparent resin layer A, a composition for forming a photo-alignment film was applied to a width of 600 mm in the central portion of the film using a slot die coater. The solvent was removed by transporting the coating film through a ventilation drying oven set at 100° C. for 2 minutes. After that, polarized UV light directed at 45° with respect to the longitudinal direction of the film was irradiated so as to have an intensity of 20 mJ/cm ² (313 nm standard) to impart an alignment regulating force to form a photo-alignment film. .

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・溶剤：ｏ－キシレン ９８部 The composition for forming a photo-alignment film was obtained by mixing the following solvent described in JP-A-2013-033249 and a photo-aligning polymer, and stirring the mixture at 80° C. for 1 hour.
・Photo-alignable polymer:

2 parts Solvent: o-xylene 98 parts

On the photo-alignment film, the composition for forming a polarizer was applied in a width range of 600 mm in the central portion of the film using a slot die coater. The coating film was conveyed in a ventilation drying oven set at 110° C. for 2 minutes to remove the solvent. Thereafter, a high-pressure mercury lamp was used to irradiate ultraviolet light at 1000 mJ/cm ² (365 nm standard) to cure the polymerizable liquid crystal compound contained in the polarizer-forming composition, thereby forming a polarizer. The resulting polarizer with a base film had a structure in which a transparent resin layer A (diffusion prevention layer A), a photo-alignment film and a polarizer were laminated in this order on one side of the base film.

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・二色性アゾ色素：

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・重合開始剤：
２－ジメチルアミノ－２－ベンジル－１－（４－モルホリノフェニル）ブタン－１－オン（イルガキュア３６９；チバ・スペシャルティ・ケミカルズ社製） ６部
・レベリング剤：
ポリアクリレート化合物（ＢＹＫ－３６１Ｎ；ＢＹＫ－Ｃｈｅｍｉｅ社製） １．２部
・溶剤：ｏ－キシレン ２５０部 A polarizer-forming composition was obtained by mixing the following polymerizable liquid crystal compound, dichroic azo dye, polymerization initiator, leveling agent and solvent, and stirring the mixture at 80° C. for 1 hour. As the dichroic dye, an azo dye described in Examples of JP-A-2013-101328 was used.
・Polymerizable liquid crystal compound:

75 copies

25 parts Dichroic azo dye:

2.5 parts

2.5 parts

2.5 parts Polymerization initiator:
2-dimethylamino-2-benzyl-1-(4-morpholinophenyl)butan-1-one (Irgacure 369; manufactured by Ciba Specialty Chemicals) 6 parts Leveling agent:
Polyacrylate compound (BYK-361N; manufactured by BYK-Chemie) 1.2 parts Solvent: o-xylene 250 parts

A small piece of 5 cm square was cut out from the obtained laminate roll, the base film was peeled off, and the cross section was observed with a scanning transmission electron microscope (field emission scanning electron microscope "S-5500", manufactured by Hitachi, Ltd.). , having a structure of anti-diffusion layer A (1 μm)/polarizer layer (2 μm). The thickness of the photo-alignment film was about 50 nm.

[Preparation of Retardation Layer]
The surface opposite to the release-treated surface of a roll-shaped release polyethylene terephthalate (PET) film with a film width of 800 mm (“FF-50” manufactured by Unitika Ltd., single-sided release-treated PET film, support substrate thickness: 50 μm) After corona treatment, the composition for forming a photo-alignment film was applied using a slot die coater. After drying the coating film at 120° C. for 2 minutes, it was cooled to room temperature. A photo-alignment film was formed by irradiating polarized ultraviolet light at 100 mJ/cm ² (313 nm standard) so that the direction of the alignment regulating force formed an angle of 0° with respect to the transport direction (long direction) of the long film.

A composition for forming a retardation layer was applied onto the photo-alignment film using a slot die coater. After the coating film was dried by heating at 120° C. for 2 minutes, it was cooled to room temperature. A long film having a retardation layer was obtained by irradiating the coated film with ultraviolet light at an exposure amount of 1000 mJ/cm ² (365 nm standard) using an ultraviolet light irradiation device. The resulting film (retardation film) had a structure in which a photo-alignment layer and a retardation layer were laminated in this order on one side of a release PET film (FF-50).

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・重合開始剤：２－ジメチルアミノ－２－ベンジル－１－（４－モルホリノフェニル）ブタン－１－オン（イルガキュア（登録商標）３６９；ＢＡＳＦジャパン社製） ８部
・レベリング剤：ポリアクリレート化合物（ＢＹＫ－３６１Ｎ；ＢＹＫ－Ｃｈｅｍｉｅ社製） ０．１部
・その他の添加剤：ＬＡＬＯＭＥＲ ＬＲ９０００（ＢＡＳＦジャパン社製） ６．７部
・溶剤：シクロペンタノン ５４６部
・溶剤：Ｎ－メチルピロリドン ３６４部 A composition for forming a retardation layer was obtained by mixing the following polymerizable liquid crystal compound, polymerization initiator, leveling agent, additive and solvent, and stirring the mixture at 80° C. for 1 hour.
・Polymerizable liquid crystal compound:

100 copies

33 parts Polymerization initiator: 2-dimethylamino-2-benzyl-1-(4-morpholinophenyl) butan-1-one (Irgacure (registered trademark) 369; manufactured by BASF Japan) 8 parts Leveling agent: Polyacrylate Compound (BYK-361N; manufactured by BYK-Chemie) 0.1 parts Other additives: LALOMER LR9000 (manufactured by BASF Japan) 6.7 parts Solvent: Cyclopentanone 546 parts Solvent: N-methylpyrrolidone 364 Department

A film piece (4 cm x 4 cm) was cut out from the obtained retardation film at an arbitrary location, and the thickness of the photo-alignment film and the retardation layer was measured using a laser microscope (LEXT3000, manufactured by Olympus). The thickness of the photo-alignment film was 50 nm, the thickness of the retardation layer was 2.1 μm, and it was confirmed that a very thin retardation film was obtained.

[Lamination of Polarizer and Retardation Layer]
The polarizer-side surface of the prepared polarizer with a base film was subjected to corona treatment, and the polyvinyl alcohol-based resin composition was applied by a bar coating method (at a speed of 30 mm/sec) so that the film thickness after curing was 1.0 μm. applied. The corona treatment conditions were an output of 800 W, a treatment speed of 10 m/min, and one treatment. As the polyvinyl alcohol-based resin composition, a composition obtained by preparing acetoacetyl-modified polyvinyl alcohol (trade name “Z-200”, Mitsubishi Chemical Corporation) with pure water was used. Details of Z-200 are shown in Table 1.

Corona treatment was performed on the surface of the retardation layer. The corona treatment conditions were an output of 800 W, a treatment speed of 10 m/min, and one treatment. The corona-treated surface of the retardation layer was laminated on the polyvinyl alcohol-based resin composition applied to the surface of the polarizer. This laminate was heated at 100° C. for 2 minutes and then held in the air at a temperature range of 40° C. to 50° C. for 12 hours to form a first cured product layer. As described above, the polarizing plate of Example 1 is obtained, in which the polarizer containing the dichroic azo dye, the first cured product layer, and the retardation layer containing the cured product of the polymerizable liquid crystal compound are laminated in this order in contact with each other. rice field.

<Production of laminate of Comparative Example 1>
As Comparative Example 1, a laminate having no first cured product layer and having a polarizer and a retardation layer bonded together via an adhesive layer was prepared. First, a pressure-sensitive adhesive sheet was prepared in which an acrylic pressure-sensitive adhesive layer having a thickness of 5 μm was provided between a light release film and a heavy release film as the pressure-sensitive adhesive layer. The polarizer side of the polarizer with the base film described in Example 1 was bonded to the surface of the pressure-sensitive adhesive sheet from which the lightly releasable film was removed. Before lamination, the polarizer surface was subjected to corona treatment once at an output of 800 W and a processing speed of 10 m/min, and the pressure-sensitive adhesive layer surface was subjected to corona treatment three times at an output of 280 W and a processing speed of 10 m/min. The retardation layer described in Example 1 was laminated to the surface of the pressure-sensitive adhesive sheet from which the heavy release sheet was removed. Before lamination, the surface of the retardation layer was subjected to corona treatment once at an output of 800 W and a processing speed of 10 m/min, and the surface of the pressure-sensitive adhesive layer was subjected to corona treatment three times at an output of 280 W and a processing speed of 10 m/min. Thus, a laminate of Comparative Example 1 was obtained. The method is the same as in Example 1, except as noted.

<Production of laminate of Comparative Example 2>
As Comparative Example 2, a laminate was prepared in which a polarizer and a retardation layer were laminated via a first cured material layer and an adhesive layer. As a specific procedure, first, the polyvinyl alcohol-based resin composition is applied to the polarizer-side surface of the polarizer with the base film prepared in Example 1, dried at 100 ° C. for 2 minutes, and the first cured product. A layered polarizer was obtained. By the same method as in Comparative Example 1, the polarizer with the first cured product layer and the retardation layer were bonded via the pressure-sensitive adhesive layer to obtain a laminate of Comparative Example 2.

<Durability Evaluation of Polarizer and Retardation Layer>
An acrylic pressure-sensitive adhesive sheet (with a separate film) having a thickness of 15 μm was attached to the retardation layer side of the laminates of Examples and Comparative Examples. This laminate was cut into a size of 30 mm × 30 mm, the separate film was peeled off, and it was laminated to non-alkali glass manufactured by Corning (trade name: Eagle XG, 40 mm × 40 mm × thickness 0.7 mm). Autoclaving was carried out at °C. After the autoclave treatment, the base film (FF-50) on the polarizer side was peeled off to obtain a sample.

[Measurement of degree of polarization]
Each sample was left for 168 hours in an oven set to a high temperature (85° C. dry) condition. The visibility correction polarization degree (Py1) (%) before being put in the oven and the visibility correction polarization degree (Py2) (%) left in the oven for 168 hours were measured with a spectrophotometer (V-7100 manufactured by JASCO Corporation). ΔPy, which is the amount of change, was calculated based on the following formula. Py1 and Py2 were measured by irradiating measurement light from the polarizer side of each sample, transmitting the sample, and emitting light from the retardation layer side.
ΔPy=|Py2−Py1|
ΔPy was evaluated based on the following criteria.
A: The amount of change in the degree of polarization ΔPy is less than 0.5 B: The amount of change in the degree of polarization ΔPy is 0.5 or more and less than 1.0 C: The amount of change in the degree of polarization ΔPy is 1.0 or more

[Measurement of phase difference value]
Samples for testing were prepared in the same manner as above. Each sample was left for 168 hours in an oven set to high temperature and high humidity conditions (temperature of 65° C., relative humidity of 90% RH). The in-plane retardation value (Re1) (nm) at a wavelength of 550 nm before being placed in the oven and the in-plane retardation value (Re2) (nm) at a wavelength of 550 nm after being left in the oven for 168 hours were measured using a phase difference measurement apparatus KOBRA. -WPR (manufactured by Oji Keisokuki Co., Ltd.) was used to calculate ΔRe, which is the amount of change, based on the following formula. Note that Re1 and Re2 were measured by irradiating measurement light from the non-alkali glass side (retardation layer side) of each sample, transmitting the sample, and emitting light from the polarizer side.
ΔRe=|Re2−Re1|
ΔRe was evaluated based on the following criteria.
A: The amount of change ΔRe in the phase difference value is less than 0.5 B: The amount of change ΔRe in the phase difference value is 0.5 or more and less than 2.5 C: The amount of change ΔRe in the phase difference value is 2.5 or more

A polarizing plate in which a polarizer, a first cured layer and a retardation layer are laminated in contact with each other in this order, and the first cured layer is a cured layer of a polyvinyl alcohol-based resin composition, ΔPy at a temperature of 85 ° C. It is thought that the dye diffusion of the polarizer is suppressed at high temperatures. In addition, such a polarizing plate has a small ΔRe at a temperature of 65° C. and a relative humidity of 90% RH, and it is considered that the monomer diffusion of the retardation layer is suppressed under high temperature and high humidity conditions.

100 polarizing plate, 10 polarizer, 20 first cured material layer, 40 retardation layer.

Claims (7)

A polarizing plate in which a polarizer containing a dichroic azo dye, a cured product layer of a polyvinyl alcohol-based resin composition, and a retardation layer containing a cured product of a polymerizable liquid crystal compound are laminated in this order in contact with each other. The polarizing plate according to claim 1, wherein the polyvinyl alcohol-based resin composition contains acetoacetyl group-modified polyvinyl alcohol. The polarizing plate according to claim 1 or 2, wherein the polyvinyl alcohol resin contained in the polyvinyl alcohol resin composition has a saponification degree of 85 mol% or more and 100 mol% or less. The polarizing plate according to any one of claims 1 to 3, wherein the polyvinyl alcohol resin contained in the polyvinyl alcohol resin composition has a polymerization degree of 1000 or more and 5000 or less. The polyvinyl alcohol-based resin composition according to any one of claims 1 to 4, which does not contain an aldehyde compound or contains 8.0 parts by mass or less of an aldehyde compound with respect to 100 parts by mass of the polyvinyl alcohol-based resin. Polarizer. The polarizing plate according to any one of claims 1 to 5, wherein the retardation layer includes a quarter-wave plate layer. An image display device comprising the polarizing plate according to any one of claims 1 to 6.

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