CN114910989A

CN114910989A - Polarizing plate

Info

Publication number: CN114910989A
Application number: CN202210111779.9A
Authority: CN
Inventors: 加藤慎也; 出崎光
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2021-02-08
Filing date: 2022-01-29
Publication date: 2022-08-16
Also published as: KR20220114492A; TW202241704A; JP2022120975A

Abstract

The invention aims to obtain a polarizing plate with improved durability of a polarizer and a phase difference layer. The present invention provides a polarizing plate, which is laminated with a polarizing plate containing a dichroic azo dye, a first cured layer, a second cured layer and a phase difference layer containing a cured product of a polymerizable liquid crystal compound in order of contact, wherein the first cured layer is a cured layer of a polyvinyl alcohol resin composition, and the second cured layer is a cured layer of a cationic polymerizable composition.

Description

Polarizing plate

Technical Field

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

Background

Conventionally, in an image display device, a method of suppressing a decrease in visibility due to reflection of external light by disposing an optical layered body having antireflection performance on a visible side of an image display panel has been employed. As an optical laminate having antireflection performance, a circularly polarizing plate including a polarizing plate and a retardation layer is known.

When an image display device is used under severe environments, for example, environments such as immersion in warm water, there is a problem that the optical characteristics of the polarizing plate are liable to be lowered. Jp 2013-105036 a describes that a polarizing plate having excellent durability can be obtained by increasing the boric acid content in the polarizing plate.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2013-105036

Disclosure of Invention

Problems to be solved by the invention

In addition, the optical characteristics of the retardation layer are also liable to be degraded under severe environments. The invention aims to provide a polarizing plate with improved durability of a polarizer and a phase difference layer and an image display device with the polarizing plate.

Means for solving the problems

The present invention provides a polarizing plate and an image display device exemplified below.

[1] A polarizing plate comprising a dichroic azo dye, a first cured layer, a second cured layer, and a phase difference layer comprising a cured product of a polymerizable liquid crystal compound, which are laminated in contact with each other in this order,

the first cured product layer is a cured product layer of a polyvinyl alcohol resin composition,

the second cured product layer is a cured product layer of a cationically polymerizable composition.

[2] The polarizing plate according to [1], wherein the polyvinyl alcohol resin composition comprises an acetoacetyl-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 a polymerization degree of the polyvinyl alcohol resin contained in the polyvinyl alcohol resin composition is 1000 or more and 5000 or less.

[5] The polarizing plate according to any one of [1] to [4], wherein the polyvinyl alcohol resin composition contains no aldehyde compound or 8.0 parts by mass or less of an aldehyde compound per 100 parts by mass of the polyvinyl alcohol resin.

[6] The polarizing plate according to any one of [1] to [5], wherein the cationically polymerizable composition contains an oxetane compound.

[7] The polarizing plate according to [6], wherein the cationically polymerizable composition further comprises an epoxy compound.

[8] The polarizing plate according to [7], wherein the oxetane compound is contained in the cationically polymerizable composition in an amount of 10 to 2000 parts by mass based on 100 parts by mass of the epoxy compound.

[9] The polarizing plate according to any one of [1] to [8], wherein the cationically polymerizable composition further comprises a photosensitizer.

[10] The polarizing plate according to any one of [1] to [9], wherein the phase difference layer comprises an 1/4-wavelength plate layer.

[11] An image display device comprising the polarizing plate according to any one of [1] to [10 ].

Effects of the invention

According to the present invention, a polarizing plate having improved durability of a polarizing plate and a retardation layer, and an image display device including the polarizing plate can be provided.

Drawings

Fig. 1 is a schematic cross-sectional view schematically showing an example of the polarizing plate of the present invention.

Description of the reference numerals

100 polarizer plate, 10 polarizer, 20 first cured layer, 30 second cured layer, 40 phase difference layer.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the embodiments below. In all the drawings below, the proportion of each component shown in the drawings is not necessarily equal to the proportion of the actual component, and the components are appropriately scaled for easy understanding.

< polarizing plate >

The polarizing plate of the present invention is explained while referring to fig. 1. The polarizing plate 100 of the present invention includes a polarizer 10 including a dichroic azo dye, a first cured material layer 20, a second cured material layer 30, and a phase difference layer 40 including a cured product of a polymerizable liquid crystal compound, which are laminated in contact with each other in this order. The polarizing plate 100 is, for example, a circular polarizing plate including a linear polarizer and a retardation layer. In this specification, the circularly polarizing plate includes an elliptically polarizing plate. The circularly polarizing plate may have an anti-reflection function in the image display device.

The dichroic azo dye contained in the polarizing plate is suitable for producing a polarizing plate having excellent polarizing performance because of its high linearity, but even if a very small amount of the dye diffuses out of the polarizing plate, the optical characteristics of the polarizing plate may be degraded. In particular, this diffusion is significant in a high-temperature environment, and there is a problem that the polarizing plate is likely to deteriorate. The polarizing plate having a configuration in which a polarizing plate containing a dichroic azo dye, a first cured layer as a cured layer of a polyvinyl alcohol resin composition, and a second cured layer as a cured layer of a cationically polymerizable composition are brought into contact in this order can suppress diffusion (particularly thermal diffusion) of the dichroic azo dye, and can improve the durability of the polarizing plate. The polarizing plate of the present invention has a polarization degree variation of less than 1.0 even when placed in a high temperature environment at a temperature of 85 ℃.

On the other hand, a retardation layer comprising a cured product of a polymerizable liquid crystal compound has a problem that a monomer is easily diffused and the retardation layer is easily deteriorated under an environment such as high temperature and high humidity. By laminating a retardation layer containing a cured product of a polymerizable liquid crystal compound in contact with a second cured product layer, diffusion of monomers can be suppressed, and the durability of the retardation layer can be improved. The polarizing plate of the present invention has a retardation value change amount of less than 2.5nm at a wavelength of 550nm in an 1/4-wavelength plate even when placed in a high-temperature and high-humidity environment having a temperature of 65 ℃ and a relative humidity of 90%.

The optical laminate may have a square shape in a plan view, for example, preferably has a square shape having long sides and short sides, and more preferably has a rectangular shape. Each layer forming the optical laminate may be subjected to R processing on the corners, notching the ends, or drilling.

The optical laminate can be used for, for example, an image display device. The image display device is not particularly limited, and examples thereof include an organic electroluminescence (organic EL) display device, an inorganic electroluminescence (inorganic EL) display device, a liquid crystal display device, and an electroluminescence display device.

[ polarizing plate ]

The polarizing plate may be a stretched film having a dichroic azo dye adsorbed thereon, or a cured product of a composition containing a polymerizable liquid crystal compound and a dichroic azo dye.

As the stretched film having a dichroic azo dye adsorbed thereon, for example, a polarizing plate obtained by dyeing a polyvinyl alcohol (hereinafter, may be abbreviated as "PVA") based resin film with a dichroic dye containing a dichroic azo dye and uniaxially stretching the resin film can be used.

The polyvinyl alcohol resin can be obtained by saponifying a polyvinyl acetate resin. As the polyvinyl acetate-based resin, polyvinyl acetate which is a homopolymer of vinyl acetate may be used, and a copolymer of vinyl acetate and another monomer copolymerizable therewith may be used. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acid compounds, olefin compounds, vinyl ether compounds, unsaturated sulfone compounds, and (meth) acrylamide compounds having an ammonium group.

The saponification degree of the polyvinyl alcohol resin is usually about 85 mol% or more and 100 mol% or less, and preferably 98 mol% or more. The polyvinyl alcohol resin may be modified, and polyvinyl formal, polyvinyl acetal, or the like modified with aldehydes may be used. The polyvinyl alcohol resin has an average polymerization degree of 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 resin can be determined in accordance with JIS K6726 (1994). If the average polymerization degree is less than 1000, it is difficult to obtain preferable polarization performance, and if it exceeds 10000, film processability may be poor.

As another method for producing a linear polarizing plate comprising a polyvinyl alcohol resin film, there is a method comprising the steps of preparing a base film, coating a solution of a resin such as a polyvinyl alcohol resin on the base film, and drying the coating to remove the solvent to form a resin layer on the base film. A primer layer may be formed in advance on the resin layer-forming surface of the substrate film. Examples of the material of the primer layer include resins obtained by crosslinking hydrophilic resins used for linear polarizers.

Examples of the substrate film include a polycycloolefin resin film; 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; a polycarbonate-based resin film; a (meth) acrylic resin film; a thermoplastic resin film known in the art, such as a polypropylene resin film. The thickness of the base film is usually 100 μm or less, preferably 80 μm or less, more preferably 60 μm or less, still more preferably 40 μm or less, even more preferably 30 μm or less, and usually 5 μm or more, preferably 10 μm or more, from the viewpoint of reduction in thickness.

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

Then, if necessary, the amount of solvent such as water in the resin layer is adjusted, and then the base film and the resin layer are uniaxially stretched, and then the resin layer is dyed with a dichroic dye to adsorb and orient the dichroic dye in the resin layer. If necessary, the resin layer having the dichroic dye adsorbed and oriented is treated with an aqueous boric acid solution, and a washing step of washing away the aqueous boric acid solution is performed. In this way, a resin layer in which a dichroic dye is adsorbed and oriented, that is, a polarizing plate is manufactured. In each step, a known method can be used.

The uniaxial stretching of the base film and the resin layer may be performed before dyeing, during boric acid treatment after dyeing, or in each of these plural stages. The base film and the resin layer may be uniaxially stretched in the MD direction (film transport direction), and in this case, the base film and the resin layer may be uniaxially stretched between rolls having different peripheral speeds, or may be uniaxially stretched using a heat roll. The substrate film and the resin layer may be uniaxially stretched in the TD direction (direction perpendicular to the film transport direction), and in this case, a so-called tenter method may be used. The stretching of the base film and the resin layer may be dry stretching in which the stretching is performed in the atmosphere, or wet stretching in which the stretching is performed in a state where the resin layer is swollen with a solvent. The stretching ratio is 4 times or more, preferably 5 times or more, and particularly preferably 5.5 times or more in order to exhibit the performance of the polarizing plate. The upper limit of the stretch ratio is not particularly limited, but is preferably 8 times or less from the viewpoint of suppressing breakage or the like.

The polarizing plate produced by the above method can be used as a linear polarizing plate after peeling off the base film or together with the base film. According to the above method, since the substrate film can be peeled, the linear polarizing plate can be thinned.

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

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

The polymerizable liquid crystal compound has a polymerizable reactive group and exhibits liquid crystallinity. The polymerizable reactive group is a group participating in polymerization reaction, and is preferably a photopolymerizable reactive group. The photopolymerizable reactive group means a group capable of participating in a polymerization reaction by an active radical generated from a photopolymerization initiator, an acid, or the like. Examples of the photopolymerizable functional group include a vinyl group, a vinyloxy group, a 1-chloroethenyl group, an isopropenyl group, a 4-vinylphenyl group, an acryloyloxy group, a methacryloyloxy group, an epoxyethyl group, an oxetanyl group and the like. Among them, acryloyloxy, methacryloyloxy, vinyloxy, epoxyethyl and oxetanyl groups are preferable, and acryloyloxy group is more preferable. The type of the polymerizable liquid crystal compound is not particularly limited, and a rod-like liquid crystal compound, a discotic liquid crystal compound, and a mixture thereof can be used. The liquid crystallinity of the polymerizable liquid crystal compound may be a thermotropic liquid crystal or a lyotropic liquid crystal, and the phase-ordered structure may be a nematic liquid crystal or a smectic liquid crystal.

Examples of the composition containing a polymerizable liquid crystal compound and a dichroic dye and the method for producing a polarizing plate using the composition include the methods described in japanese patent application laid-open nos. 2013-37353, 2013-33249, and 2017-83843. The composition for forming a polarizing plate may further include additives such as a solvent, a polymerization initiator, a crosslinking agent, a leveling agent, an antioxidant, a plasticizer, and a sensitizer in addition to the polymerizable liquid crystal compound and the dichroic dye. These components may be used alone in 1 kind, or 2 or more kinds may be used in combination.

The polymerization initiator is a compound capable of initiating the polymerization reaction of the polymerizable liquid crystal compound, and is preferably a photopolymerization initiator from the viewpoint of being capable of initiating the polymerization reaction under a lower temperature condition. Specifically, there may be mentioned photopolymerization initiators capable of generating active radicals or acids by the action of light, and among them, 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, and more preferably 3 parts by mass or more and 8 parts by mass or less, relative to 100 parts by weight of the total amount of the polymerizable liquid crystal compound. When the amount is 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 polarizing plate 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 polarizing plate may be laminated with the first cured product layer while having the alignment film. As the alignment film, a photo-alignment film is preferable from the viewpoints of accuracy and quality of an alignment angle, water resistance and flexibility of a polarizing plate, and the like. The thickness of the alignment film is preferably 10nm or more and 5000nm or less, more preferably 1000nm or less, and may be 500nm or less, and may be 300nm or less.

(dichroic azo dye)

Examples of the dichroic azo dye include monoazo dye, disazo dye, trisazo dye, tetraazo dye, and stilbene azo dye, and the disazo dye and the trisazo dye are preferable, and for example, a compound represented by formula (I) (hereinafter also referred to as "compound (I)") can be mentioned.

K ¹ (-N＝N-K ² ) _p -N＝N-K ³ (I)

[ in the formula (I), K ¹ And K ³ Independently of one another, represents an optionally substituted phenyl group, an optionally substituted naphthyl group or an optionally substituted 1-valent heterocyclic group. K is ² Represents an optionally substituted p-phenylene group, an optionally substituted naphthalene-1, 4-diyl group or an optionally substituted 2-valent heterocyclic group. p represents an integer of 1 to 4. When p is an integer of 2 or more, a plurality of K ² May be the same or different from each other. The — N ═ N-bond may be replaced by — C ═ C-, -COO-, -NHCO-, -N ═ CH-bond in the range showing absorption in the visible region.]

Examples of the heterocyclic group having a valence of 1 include groups obtained by removing 1 hydrogen atom from a heterocyclic compound such as quinoline, thiazole, benzothiazole, thienothiazole, imidazole, benzimidazole, oxazole and benzoxazole. Examples of the 2-valent heterocyclic group include those obtained by removing 2 hydrogen atoms from the above-mentioned heterocyclic compounds.

As K ¹ And K ³ Phenyl, naphthyl and heterocyclic group having a valence of 1 in (1), and K ² InExamples of the substituent optionally having the p-phenylene group, the naphthalene-1, 4-diyl group and the 2-valent heterocyclic group include an alkyl group having 1 to 4 carbon atoms; alkoxy groups having 1 to 4 carbon atoms such as methoxy, ethoxy, butoxy and the like; a C1-4 fluoroalkyl group such as a trifluoromethyl group; a cyano group; a nitro group; a halogen atom; a substituted or unsubstituted amino group such as an amino group, a diethylamino group, or a pyrrolidinyl group (the substituted amino group means an amino group having 1 or 2 alkyl groups having 1 to 6 carbon atoms or an amino group in which 2 substituted alkyl groups are bonded to each other to form an alkanediyl group having 2 to 8 carbon atoms; the unsubstituted amino group is-NH ₂ . ) And the like.

Among the compounds (I), preferred are compounds represented by any of the following formulae (I-1) to (I-8).

[ solution 1]

[ formulae (I-1) to (I-8),

B ¹ ～B ³⁰ independently represents 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 (the definitions of the substituted amino group and the unsubstituted amino group are as described above), 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, a plurality of B ² May be the same as, or different from,

when n2 is 2 or more, a plurality of B ⁶ May be the same as, or different from,

when n3 is 2 or more, a plurality of B ⁹ May be the same as, or different from,

when n4 is 2 or more, a plurality of B ¹⁴ May be the same as or different from each other.]

The weight average molecular weight of the dichroic azo dye is usually 300 or more and 2000 or less, and preferably 400 or more and 1000 or less. When the weight average molecular weight of the dichroic azo dye is not more than the upper limit value, the dichroic azo dye is likely to move and diffuse out of the polarizing plate. In this case, the polarizing plate having a configuration in which the polarizing plate containing the dichroic azo dye and the first cured product layer as the cured product layer of the polyvinyl alcohol resin composition are sequentially brought into contact with each other can suppress diffusion (particularly thermal diffusion) of the dichroic azo dye, and can improve the durability of the polarizing plate.

When the polarizing plate has a polymerizable liquid crystal compound, the content of the dichroic azo dye is, for example, 0.1 part by mass or more and 50 parts by mass or less, preferably 0.1 part by mass or more and 20 parts by mass or less, and more preferably 0.1 part by mass or more and 12 parts by mass or less with respect to 100 parts by mass of the polymerizable liquid crystal compound. 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 polarizing plate having a high degree of alignment order can be obtained.

[ first cured product layer ]

The first cured product layer is a cured product layer of a polyvinyl alcohol resin composition. The first cured product layer as the cured product layer of the polyvinyl alcohol resin composition can prevent the diffusion of the dichroic azo dye from the polarizing plate. The first cured product layer as the cured product layer of the polyvinyl alcohol resin composition protects the surface of the polarizing plate and is excellent in heat resistance. The first cured product layer generally has adhesiveness to the polarizing plate.

The polyvinyl alcohol resin contained in the polyvinyl alcohol resin composition may contain, in addition to partially saponified polyvinyl alcohol and completely saponified polyvinyl alcohol, modified polyvinyl alcohol resins such as carboxyl-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, hydroxymethyl-modified polyvinyl alcohol, and amino-modified polyvinyl alcohol. The polyvinyl alcohol resin contained in the polyvinyl alcohol resin composition preferably contains acetoacetyl-modified polyvinyl alcohol from the viewpoint of suppressing deterioration of the polarizing plate. The polyvinyl alcohol resin contained in the polyvinyl alcohol resin composition may be a commercially available polyvinyl alcohol resin. Examples of commercially available products include "PVA-403" as partially saponified polyvinyl alcohol sold by Kuraray, "KL-506" and "KL-318" as carboxyl group-modified partially saponified polyvinyl alcohol, and "Z-100", "Z-200" and "Z-300" as acetoacetyl group-modified partially saponified polyvinyl alcohol sold by Mitsubishi chemical corporation.

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

The polyvinyl alcohol resin contained in the polyvinyl alcohol resin composition has an average polymerization degree of usually 1000 or more and 5000 or less, preferably 1500 or more and 3000 or less, and may be 2000 or less, and may be 1500 or less. When the average polymerization degree is in this range, deterioration of the polarizing plate can be favorably suppressed.

The content of the polyvinyl alcohol resin contained in the polyvinyl alcohol resin composition is preferably 85 mass% or more, more preferably 90 mass% or more, and still more preferably 95 mass% or more, based on the mass of the solid content of the polyvinyl alcohol resin composition. The solid content of the polyvinyl alcohol resin composition may be all the polyvinyl alcohol resin (i.e., 100 mass%). The solid content of the polyvinyl alcohol resin composition refers to the total amount of components obtained by removing the solvent from the polyvinyl alcohol resin composition when the solvent is contained in the polyvinyl alcohol resin composition.

The polyvinyl alcohol resin composition preferably contains a solvent from the viewpoint of good coatability and workability in producing a cured product of the polyvinyl alcohol resin composition. Examples of the solvent in the polyvinyl alcohol resin composition include water and a miscible solvent of water and a hydrophilic organic solvent (for example, an alcohol solvent, an ether solvent, an ester solvent, and the like). When the polyvinyl alcohol resin composition contains a solvent, the solid content thereof is preferably 1 mass% or more and 30 mass% or less, and more preferably 2 mass% or more and 10 mass% or less.

The polyvinyl alcohol resin composition may contain additives such as a stabilizer, an antioxidant, an antistatic agent, an ultraviolet absorber, a surface conditioner, and a crosslinking agent, if necessary. The additives may be used singly or in combination of 2 or more. The content of the additive is preferably about 0.1 mass% to 10 mass% based on the mass of the solid content of the polyvinyl alcohol resin composition.

Examples of the crosslinking agent include amine compounds, aldehyde compounds, methylol compounds, water-soluble epoxy resins, isocyanate compounds, polyvalent metal salts, and the like. When a polyvinyl alcohol resin is used as the adhesive component, an aldehyde compound typified by glyoxal, a methylol compound typified by methylolmelamine, a water-soluble epoxy resin, or the like can be used as a crosslinking agent. The water-soluble epoxy resin may be, 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 or triethylenetetramine and a dicarboxylic acid such as adipic acid. Examples of commercially available products of water-soluble epoxy resins include "Sumirez Resin (registered trademark) 650 (30)", which is sold by Tiokang chemical industries, Ltd.

The polyvinyl alcohol resin composition may not contain a crosslinking agent. From the viewpoint of suppressing deterioration of the polarizing plate, the content of the aldehyde compound is preferably 8.0 parts by mass or less, more preferably 5.0 parts by mass or less, per 100 parts by mass of the polyvinyl alcohol resin, and the polyvinyl alcohol resin composition may not contain the aldehyde compound.

The polyvinyl alcohol resin composition can be prepared by dissolving a polyvinyl alcohol resin and additives used as needed in a solvent. The first cured product layer, which is a cured product layer of the polyvinyl alcohol resin composition, can be obtained by applying the polyvinyl alcohol resin composition to one surface of the polarizing plate and drying and removing the solvent.

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

[ phase difference layer ]

The retardation layer may be 1 layer or 2 or more layers. The retardation layer may include a base film for supporting the retardation layer, an adhesive layer for bonding a plurality of retardation layers, and the like. The retardation layer may further include an alignment film. The retardation layer preferably includes an 1/4 wavelength plate layer, and may further include at least either a 1/2 wavelength plate layer or a positive C layer. When the retardation layer includes an 1/2 wavelength plate layer, a 1/2 wavelength plate layer and a 1/4 wavelength plate layer are stacked in this order from the linear polarizer side. When the retardation layer includes the positive C layer, the 1/4-wavelength plate layer and the positive C layer may be stacked in this order from the linear polarizer side, or the positive C layer and the 1/4-wavelength plate layer may be stacked in this order from the linear polarizer side. The thickness of the retardation layer is, for example, 0.1 to 10 μm, preferably 0.5 to 8 μm, and more preferably 1 to 6 μm.

The retardation layer contains a cured product of a polymerizable liquid crystal compound. The retardation layer can be formed by applying a composition containing a polymerizable liquid crystal compound to a substrate film 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 those of the thermoplastic resin film. The retardation layer may be incorporated in the polarizing plate in a form having an alignment film and a base film. The surface of the retardation layer facing the polarizer is preferably a layer containing a cured product of a polymerizable liquid crystal compound. The surface of the retardation layer facing the polarizer may be the surface of a layer exhibiting a retardation, or may be an alignment film.

The retardation layer may further include a layer formed of a resin film in addition to the layer including a cured product of the polymerizable liquid crystal compound. The resin film may be the above-mentioned thermoplastic resin film.

The liquid crystal layer exhibiting a retardation can be formed using a known liquid crystal compound. The type of the liquid crystal compound contained in the composition containing a polymerizable liquid crystal compound is not particularly limited, and a rod-like liquid crystal compound, a discotic liquid crystal compound, and a mixture thereof can be used. The composition containing a polymerizable liquid crystal compound may contain a polymeric liquid crystal compound. Examples of the liquid crystal compound include those described in Japanese patent application laid-open Nos. 11-513019, 2005-289980, 2007-108732, 2010-244038, 2010-31223, 2010-270108, 2011-6360, 2011-207765, 2016-81035, 2017/043438 and 2011-207765.

The 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 improving agent, a plasticizer, an alignment agent, and the like. As a method for applying the composition containing the polymerizable liquid crystal compound, a known method such as a die coating method can be mentioned. Examples of the method for curing the composition containing the polymerizable liquid crystal compound include known methods such as irradiation with active energy rays (e.g., ultraviolet rays).

A polarizing plate in which a polarizing plate and a retardation layer are disposed so that the absorption axis of the polarizing plate and the slow axis of the retardation layer form a predetermined angle has an antireflection function, and can function as a circular polarizing plate. In the case where the phase difference layer includes an 1/4-wavelength plate layer, the angle of the absorption axis of the polarizer with the slow axis of the 1/4-wavelength plate layer may be 45 ° ± 10 °. The retardation layer may have a positive wavelength dispersion property or a negative wavelength dispersion property. The 1/4 wavelength slab preferably has reverse wavelength dispersion.

The alignment film has an alignment regulating force for aligning the liquid crystal in a desired direction in the polymerizable liquid crystal compound contained in the liquid crystal layer exhibiting a retardation formed on the alignment film. 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 a concave-convex pattern and a plurality of grooves (grooves) on the film surface. The thickness of the alignment film is usually 0.01 μm or more and 10 μm or less, and preferably 0.01 μm or more and 5 μm or less.

The alignment polymer film can be formed by applying a composition in which an alignment polymer is dissolved in a solvent to a base material film, removing the solvent, and, if necessary, subjecting the base material film to a rubbing treatment. The orientation restriction force can be arbitrarily adjusted by the surface state of the orientation polymer and the rubbing condition.

The photo-alignment polymer film may be formed by applying a composition including a polymer or monomer having a photoreactive group and a solvent to a substrate film and irradiating polarized light. In this case, the alignment regulating force can be arbitrarily adjusted by using the polarized light irradiation condition of the photo-alignment polymer.

The groove alignment film can be formed, for example, by a method of forming a concave-convex pattern by exposing and developing a surface of a photosensitive polyimide film through an exposure mask having a slit with a pattern shape; a method of forming an uncured film of an active energy ray-curable resin on a plate-like master having grooves on the surface thereof, transferring the film to a base film, and curing the film; a method of forming an uncured layer of an active energy ray-curable resin on a base film, bonding a roll-shaped master having irregularities to the layer to form irregularities, and then curing the resulting laminate.

[ second cured product layer ]

The second cured product layer is a cured product layer of a cationically polymerizable composition. The second cured product layer generally has adhesion to the first cured product layer and adhesion to the phase difference layer. The second cured layer 30 may attach the adjacent first cured layer 20 to the phase difference layer 40. The second cured product layer as the cured product layer of the cationically polymerizable composition can prevent diffusion of the unpolymerized monomer from the phase difference layer.

The second cured product layer, which is a cured product layer of the cationically polymerizable composition, protects the surface of the retardation layer and is also excellent in water resistance. When the retardation layer is bonded to the polarizing plate or the first cured product layer via the adhesive layer or the radical polymerizable second cured product layer, it is difficult to suppress diffusion of the monomer from the retardation layer. Since the hydrophobic cationically polymerizable resin can protect the polyvinyl alcohol resin having excellent blocking properties between the dichroic dye and the unpolymerized monomer, the durability of the polarizer can be further improved and a polarizing plate with a reduced thickness can be obtained by laminating a second cured product layer, which is a cured product layer of the cationically polymerizable composition, in contact with the first cured product layer, which is a cured product layer of the polyvinyl alcohol resin composition.

The cationically polymerizable compound contained in the cationically polymerizable composition is a compound or oligomer which advances a cationic polymerization reaction by irradiation with or heating of active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays and is cured, and examples thereof include epoxy compounds, oxetane compounds, and vinyl compounds. These polymerizable compounds may be used alone, or 2 or more kinds may be used in combination. The cationically polymerizable composition may contain a radically polymerizable compound as a polymerizable compound in addition to the cationically polymerizable compound. The radical polymerizable compound is a compound capable of initiating a polymerization reaction by a radical species generated from, for example, a photo radical polymerization initiator by irradiation with light.

The content of the cationically polymerizable compound contained in the cationically polymerizable composition is preferably 80 parts by mass or more and 100 parts by mass or less, more preferably 90 parts by mass or more and 99.5 parts by mass or less, and still more preferably 95 parts by mass or more and 99 parts by mass or less, based on 100 parts by mass of the total mass of the cationically polymerizable composition. When the content of the cationically polymerizable compound is within this range, the second cured product layer having excellent water resistance and excellent effect of preventing the dichroic dye from diffusing to the outside of the polarizing plate can be obtained.

The cationically polymerizable composition preferably contains a polymerizable compound having a cyclic ether structure as the polymerizable compound. Examples of the cyclic ether structure include an oxirane ring, an oxetane ring, a tetrahydrofuran ring, and a tetrahydropyran ring. Among them, from the viewpoint of suppressing diffusion of the monomer from the retardation layer and water resistance, the polymerizable compound preferably contains a cyclic ether structure having 2 to 4 carbon atoms, and more preferably contains an oxetane compound.

The oxetane compound is a compound having 1 or more oxetanyl groups (oxetane rings) in the molecule, and may be any of an aliphatic compound, an alicyclic compound, or an aromatic compound. Examples of the oxetane compound having 1 oxetanyl group include 3-ethyl-3-hydroxymethyloxetane, 2-ethylhexyloxetane, 3-ethyl-3- (phenoxymethyl) oxetane, 3- (cyclohexyloxy) methyl-3-ethyloxetane and the like. Examples of oxetane compounds having 2 or more oxetanyl groups include 1, 4-bis [ (3-ethyloxetan-3-yl) methoxy } methyl ] benzene (also referred to as "xylylene dioxirane" ]), bis (3-ethyl-3-oxetanylmethyl) ether, and the like. These oxetane compounds may be used alone, or 2 or more kinds thereof may be used in combination. The oxetane compound may be used as a main component of the cationically polymerizable compound, or may be used in combination with an epoxy compound.

The oxetane compound preferably contains an oxetane compound having 2 or more oxetanyl groups in the molecule. By including such an oxetane compound, a cured product having a high crosslinking density and a high density can be obtained, and diffusion of a dichroic dye from a polarizing plate can be effectively suppressed in combination with the first cured layer, thereby obtaining a polarizing plate in which change in optical properties with time is unlikely to occur.

The content of the oxetane compound may be, for example, 10 parts by mass or more, preferably 30 parts by mass or more, more preferably 40 parts by mass or more, further preferably 45 parts by mass or more, and particularly preferably 50 parts by mass or more, based on 100 parts by mass of the total amount of all polymerizable compounds contained in the cationically polymerizable composition. When the content of the oxetane compound is not less than the lower limit, the second cured material layer having further excellent heat resistance and moist heat resistance is obtained, and therefore, the water resistance, heat resistance and moist heat resistance of the polarizing plate can be effectively improved in combination with the first cured material layer. Thus, a polarizing plate in which change in optical performance with time is less likely to occur can be obtained. The content of the oxetane compound is preferably 90 parts by mass or less, more preferably 85 parts by mass or less, and further preferably 80 parts by mass or less, based on 100 parts by mass of the total amount of all polymerizable compounds contained in the cationically polymerizable composition. The content of the oxetane compound may be a combination of the above lower limit and upper limit, and is preferably 30 parts by mass or more and 90 parts by mass or less, more preferably 40 parts by mass or more and 85 parts by mass or less, based on 100 parts by mass of the total amount of all polymerizable compounds contained in the cationically polymerizable composition. The content of the oxetane compound is, for example, 25 parts by mass or more, preferably 35 parts by mass or more, more preferably 40 parts by mass or more, for example, 100 parts by mass or less, preferably 90 parts by mass or less, more preferably 85 parts by mass or less, relative to 100 parts by mass of the total amount of the cationically polymerizable composition.

The cationically polymerizable composition preferably contains an oxetane compound as a polymerizable compound and an epoxy compound as a polymerizable compound. The epoxy compound is a compound having 1 or more, preferably 2 or more, epoxy groups in the molecule. The cationically polymerizable composition preferably contains the oxetane compound in an amount of 10 parts by mass or more and 2000 parts by mass or less, more preferably 30 parts by mass or more and 1000 parts by mass or less, and further preferably 30 parts by mass or more and 500 parts by mass or less, based on 100 parts by mass of the epoxy compound.

The epoxy compound may be used alone in 1 kind, or may be used in combination in 2 or more kinds. Examples of the epoxy compound include alicyclic epoxy compounds, aromatic epoxy compounds, hydrogenated epoxy compounds, and aliphatic epoxy compounds. Among them, from the viewpoint of weather resistance, curing speed, and adhesion, the epoxy compound preferably contains an alicyclic epoxy compound or an aliphatic epoxy compound, and more preferably contains an alicyclic epoxy compound.

The alicyclic epoxy compound is a compound having 1 or more epoxy groups bonded to the alicyclic ring in the molecule, and preferably 2 or more epoxy groups bonded to the alicyclic ring in the molecule. The "epoxy group bonded to an alicyclic ring" refers to a bridged oxygen atom-O-in the structure represented by the following formula (II). In the formula (II), m is an integer of 2 to 5.

[ solution 2]

(CH) in the above formula (II) is removed ₂ ) _m The compound in which 1 or more hydrogen atoms are bonded to other chemical structures may be an alicyclic epoxy compound. (CH) ₂ ) _m 1 or more hydrogen atoms in (b) may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group.

From the viewpoint of increasing the glass transition temperature of the cured product, an alicyclic epoxy compound having an epoxycyclopentane structure [ m is 3 in the formula (II) ] and an epoxycyclohexane structure [ m is 4 in the formula (II) ] is preferred, and an alicyclic diepoxy compound represented by the following formula (IIA) is more preferred. The glass transition temperature of the second cured product layer of a cationically polymerizable composition containing an alicyclic diepoxy compound represented by the following formula (IIA) is increased, and the diffusion of a pigment at high temperatures can be suppressed.

[ solution 3]

In the formula (IIA), R ¹ And R ² Each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and may have an alicyclic structure when the number of carbon atoms in the alkyl group is 3 or more. The alkyl group having 1 to 6 carbon atoms may be a straight-chain or branched alkyl group, and examples of the alkyl group having an alicyclic structure include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, and the like.

In the formula (IIA), X represents an oxygen atom, an alkanediyl group having 1 to 6 carbon atoms or a group represented by any one of the following formulae (IIa) to (IId). Examples of the alkanediyl group having 1 to 6 carbon atoms include a methylene group, an ethylene group, and a propane-1, 2-diyl group.

[ solution 4]

When X in formula (IIA) is a group represented by any of formulae (IIa) to (IId), Y in each formula ¹ ～Y ⁴ Each independently an alkanediyl group having 1 to 20 carbon atoms, and when the alkanediyl group has 3 or more carbon atoms, it may have an alicyclic structure. a and b each independently represent an integer of 0 to 20.

Examples of the alicyclic epoxy compound include the following compounds a to M. The chemical formulae a to M shown in the following paragraphs are chemical formulae corresponding to the compounds a to M, respectively.

A: 3, 4-epoxycyclohexanecarboxylic acid 3, 4-epoxycyclohexylmethyl ester,

B: 3, 4-epoxy-6-methylcyclohexanecarboxylic acid 3, 4-epoxy-6-methylcyclohexylmethyl ester,

C: ethylene bis (3, 4-epoxycyclohexanecarboxylate),

D: bis (3, 4-epoxycyclohexylmethyl) adipate,

E: bis (3, 4-epoxy-6-methylcyclohexylmethyl) adipate,

F: diethylene glycol bis (3, 4-epoxycyclohexylmethyl ether),

G: ethylene glycol bis (3, 4-epoxycyclohexylmethyl ether),

H: 2, 3, 14, 15-diepoxy-7, 11, 18, 21-tetraoxatrispiro [5.2.2.5.2.2] heneicosane,

I: 3- (3, 4-epoxycyclohexyl) -8, 9-epoxy-1, 5-dioxaspiro [5.5] undecane,

J: 4-vinylcyclohexene dioxide,

K: a limonene dioxide,

L: bis (2, 3-epoxycyclopentyl) ether,

M: dicyclopentadiene dioxide.

[ solution 5]

[ solution 6]

H：

I：

J：

K：

L：

M：

The alicyclic epoxy compound is preferably 3, 4-epoxycyclohexylmethyl 3, 4-epoxycyclohexanecarboxylate from the viewpoint of easy availability. Further, from the viewpoint of effectively suppressing the diffusion of the dye, a1, 2-epoxy-4- (2-epoxyethyl) cyclohexane adduct of 2, 2-bis (hydroxymethyl) -1-butanol is preferable.

The alicyclic epoxy compound may be used alone in 1 kind or in combination of two or more kinds.

The content of the alicyclic epoxy compound is preferably 1 part by mass or more and 80 parts by mass or less, more preferably 3 parts by mass or more and 70 parts by mass or less, and further preferably 3 parts by mass or more and 60 parts by mass or less, relative to 100 parts by mass of the total amount of all polymerizable compounds contained in the cationically polymerizable composition. When the content of the alicyclic epoxy compound is in this range, curing by irradiation with active energy rays such as ultraviolet rays can be rapidly advanced, and a cured product layer (second cured product layer) having excellent heat resistance and moist heat resistance and sufficient hardness can be formed.

The aliphatic epoxy compound is a compound having at least 1 epoxy ring bonded to an aliphatic carbon atom in the molecule, and preferably has 2 or more epoxy rings in the molecule. The aliphatic epoxy compound has at least 1 oxirane ring (3-membered cyclic ether) bonded to, for example, an aliphatic carbon atom in the molecule, and preferably has 2 or more. Examples of the aliphatic epoxy compound include monofunctional epoxy compounds such as butyl glycidyl ether and 2-ethylhexyl glycidyl ether; 2-functional epoxy compounds such as 1, 4-butanediol diglycidyl ether, 1, 6-hexanediol diglycidyl ether, and neopentyl glycol diglycidyl ether; epoxy compounds having 3 or more functional groups such as trimethylolpropane triglycidyl ether and pentaerythritol tetraglycidyl ether; 4-vinylcyclohexene dioxide, limonene dioxide, and the like, epoxy compounds having 1 epoxy group directly bonded to an alicyclic ring and an oxirane ring bonded to an aliphatic carbon atom, and the like.

From the viewpoint of obtaining a cationically polymerizable composition having a low viscosity and being easy to coat, a 2-functional epoxy compound (also referred to as "aliphatic diepoxy compound") having 2 oxirane rings bonded to aliphatic carbon atoms in the molecule, represented by the following formula (III), is preferable.

[ solution 7]

In the formula (III), Z represents an alkylene group having 1 to 9 carbon atoms, an alkylidene group having 3 or 4 carbon atoms, a 2-valent alicyclic hydrocarbon group, or a group represented by the formula-C _m H _2m -Z ¹ -C _n H _2n -a group having a valence of 2 as indicated. -Z ¹ -represents-O-, -CO-O-, -O-CO-, -SO ₂ -, -SO-or CO-, and m and n each independently represent an integer of 1 or more. Wherein the sum of m and n is 9 or less.

The alicyclic hydrocarbon group having a valence of 2 may be, for example, an alicyclic hydrocarbon group having a valence of 2 and having 4 to 8 carbon atoms, and examples thereof include a residue having a valence of 2 represented by the following formula (IIIA).

[ solution 8]

Specific examples of the compound represented by the formula (III) include diglycidyl ethers of alkanediols; diglycidyl ether of an oligoalkylene glycol having a repetition number of about 4; diglycidyl ethers of alicyclic diols, and the like.

Examples of the diol (diol) capable of forming the aliphatic diepoxy compound represented by the formula (III) include ethylene glycol, propylene glycol, 1, 3-propanediol, 2-methyl-1, 3-propanediol, 2-butyl-2-ethyl-1, 3-propanediol, 1, 4-butanediol, neopentyl glycol, 3-methyl-2, 4-pentanediol, 1, 5-pentanediol, 3-methyl-1, 5-pentanediol, 2-methyl-2, 4-pentanediol, 2, 4-diethyl-1, 5-pentanediol, 1, 6-hexanediol, 1, 7-heptanediol, 3, 5-heptanediol, 1, 8-octanediol, 2-methyl-1, alkanediols such as 8-octanediol and 1, 9-nonanediol; oligo alkylene glycols such as diethylene glycol, triethylene glycol, tetraethylene glycol, and dipropylene glycol; alicyclic diols such as cyclohexanediol and cyclohexanedimethanol, and the like.

From the viewpoint of obtaining a cationically polymerizable composition having a low viscosity and being easy to coat, the aliphatic epoxy compound preferably contains 1, 4-butanediol diglycidyl ether, 1, 6-hexanediol diglycidyl ether, and neopentyl glycol diglycidyl ether. From the viewpoint of maintaining optical properties, 1, 6-hexanediol diglycidyl ether and pentaerythritol polyglycidyl ether are preferable. As the aliphatic epoxy compound, 1 kind of aliphatic epoxy compound may be used alone, or a plurality of different aliphatic epoxy compounds may be used in combination.

When the cationically polymerizable composition contains an aliphatic epoxy compound, the content of the aliphatic epoxy compound may be, for example, 1 part by mass or more and 90 parts by mass or less, preferably 1 part by mass or more and 40 parts by mass or less, more preferably 3 parts by mass or more and 30 parts by mass or less, further preferably 5 parts by mass or more and 20 parts by mass or less, and particularly preferably 7 parts by mass or more and 15 parts by mass or less, relative to 100 parts by mass of the total amount of all polymerizable compounds contained in the cationically polymerizable composition. When the content of the aliphatic epoxy compound is in this range, a cationically polymerizable composition having a low viscosity and being easy to coat can be obtained.

The aromatic epoxy compound is a compound having an aromatic ring and an epoxy group in a molecule. Specific examples thereof include bisphenol type epoxy compounds such as diglycidyl ether of bisphenol a, diglycidyl ether of bisphenol F, and diglycidyl ether of bisphenol S, and oligomers thereof; phenol novolac type epoxy resins such as phenol novolac epoxy resin, cresol novolac epoxy resin, hydroxybenzaldehyde phenol novolac epoxy resin, and the like; polyfunctional epoxy compounds such as glycidyl ethers of 2, 2 ', 4, 4' -tetrahydroxydiphenylmethane and glycidyl ethers of 2, 2 ', 4, 4' -tetrahydroxybenzophenone; and a polyfunctional epoxy resin such as epoxidized polyvinylphenol.

From the viewpoint of reducing the viscosity of the cationically polymerizable composition, the aromatic epoxy compound preferably contains at least 1 kind of epoxide selected from the group consisting of glycidyl ethers of phenols, glycidyl etherates of aromatic compounds having 2 or more alcoholic hydroxyl groups, glycidyl etherates of polyphenols, glycidyl esters of benzoic acids, glycidyl esters of polybasic acids, styrene oxide and divinylbenzene. The aromatic epoxy compound is preferably a compound having an epoxy equivalent of 80 to 500, from the viewpoint of improving curability of the cationically polymerizable composition. As the aromatic epoxy compound, 1 kind of aromatic epoxy compound may be used alone, or a plurality of kinds thereof may be used in combination.

As the aromatic epoxy compound, commercially available products can be used, and examples thereof include DENACOL EX-121, DENACOL EX-141, DENACOL EX-142, DENACOL EX-145, DENACOL EX-146, DENACOL EX-147, DENACOL EX-201, DENACOL EX-203, DENACOL EX-711, DENACOL EX-721, ONCOAT EX-1020, ONCOAT EX-1030, ONCOAT EX-1040, ONCOAT EX-1050, ONCOAT EX-1051, ONCOAT EX-1010, ONCOAT EX-1011, and ONCOAT 1012 (manufactured by Nagase CHEX. Ltd.); OGSOL PG-100, OGSOL EG-200, OGSOL EG-210, OGSOL EG-250 (manufactured by Osaka Gas Chemical Co. Ltd.); HP4032, HP4032D, HP4700 (see above, DIC co.ltd. products); ESN-475V (manufactured by Nissian iron-on-gold chemical Co., Ltd.); EPIKOTE YX8800, jER828EL (manufactured by Mitsubishi chemical Co., Ltd.); MARPROOF G-0105SA and MARPROOF G-0130SP (manufactured by Nichikoku corporation); EPICLON N-665, EPICLON HP-7200 (DIC Co. Ltd.); EOCN-1020, EOCN-102S, EOCN-103S, EOCN-104S, XD-1000, NC-3000, EPPN-501H, EPPN-501HY, EPPN-502H, NC-7000L (manufactured by Nippon chemical Co., Ltd.); ADEKA GLYCIROL ED-501, ADEKA GLYCIROL ED-502, ADEKA GLYCIROL ED-509, ADEKA GLYCIROL ED-529, ADEKA RESIN EP-4000, ADEKA RESIN EP-4005, ADEKA RESIN EP-4100, ADEKA RESIN EP-4901 (manufactured by ADEKA Co. Ltd.); TECHMORE VG-3101L, EPOX-MKR710, EPOX-MKR151 (manufactured by Printech Co. Ltd., supra), and the like.

When the cationically polymerizable composition contains the aromatic epoxy compound, the cationically polymerizable composition becomes a hydrophobic resin, and a cured product layer (second cured product layer) obtained therefrom also becomes hydrophobic. Therefore, the penetration of moisture from the outside can be prevented under high temperature and high humidity, and the movement of the dichroic dye contained in the polarizing plate can be effectively suppressed.

The content of the aromatic epoxy compound is preferably 1 part by mass or more and 70 parts by mass or less, more preferably 5 parts by mass or more and 60 parts by mass or less, further preferably 7 parts by mass or more and 55 parts by mass or less, and particularly preferably 10 parts by mass or more and 50 parts by mass or less, based on 100 parts by mass of the total amount of all polymerizable compounds contained in the cationic polymerizable composition. When the content of the aromatic epoxy compound is in this range, the hydrophobicity of the second cured product layer can be increased, and the diffusion of the dichroic dye out of the polarizing plate under high-temperature and high-humidity conditions can be more effectively suppressed.

The hydrogenated epoxy compound is a glycidyl ether of a polyhydric alcohol having an alicyclic ring, and can be a compound obtained by subjecting an aromatic polyhydric alcohol to a hydrogenation reaction selectively with respect to an aromatic ring under pressure in the presence of a catalyst, and glycidyl-etherifying a nuclear hydrogenated polyhydric compound thus obtained. Specific examples of the aromatic polyol include bisphenol compounds such as bisphenol a, bisphenol F and bisphenol S; novolac resins such as phenol novolac resin, cresol novolac resin, hydroxybenzaldehyde phenol novolac resin, and the like; and polyfunctional compounds such as tetrahydroxydiphenylmethane, tetrahydroxybenzophenone, and polyvinyl phenol. Glycidyl ethers can be prepared by hydrogenating the aromatic ring of an aromatic polyol and reacting epichlorohydrin with the resultant alicyclic polyol. Preferred examples of the hydrogenated epoxy compound include hydrogenated diglycidyl ethers of bisphenol A.

The cationically polymerizable composition may further contain other curable compounds than those described above. Specific examples of the other curable compound include other cationically polymerizable compounds other than the above compounds, such as lactone compounds, cyclic acetal compounds, cyclic thioether compounds, and spiro orthoester compounds.

The cationically polymerizable composition preferably contains a polymerization initiator for initiating polymerization. The polymerization initiator may be a photopolymerization initiator or a thermal polymerization initiator. For example, when the cationically polymerizable composition contains an oxetane compound, an epoxy compound, or the like as a polymerizable compound, a photo-cationic polymerization initiator is preferably used as a polymerization initiator.

The photo cation polymerization initiator is a substance that generates a cation species or lewis acid by irradiation of active energy rays such as visible rays, ultraviolet rays, X-rays, or electron beams, and initiates a polymerization reaction of a cation polymerizable compound. The photo cation polymerization initiator exerts a catalytic action by light, and therefore, even when it is mixed into a polymerizable compound, it is excellent in storage stability and handling properties. Examples of the compound that generates a cationic species or a lewis acid by irradiation with an active energy ray include an onium salt such as an aromatic iodonium salt or an aromatic sulfonium salt, an aromatic diazonium salt, and an iron-arene complex.

The aromatic iodonium salt is a compound having a diaryliodonium cation, and the cation is typically a diphenyliodonium cation.

The aromatic sulfonium salt is a compound having a triarylsulfonium cation, and examples of the cation generally include a triphenylsulfonium cation, a 4, 4' -bis (diphenylsulfonium) diphenylsulfide cation, and the like. The aromatic diazonium salt is a compound having a diazonium cation, and the cation is generally a benzenediazonium cation. The iron-arene complexes are typically cyclopentadienyl iron (II) arene cation complexes.

The above cation is paired with an anion (anion) to form a photocationic polymerization initiator. Examples of the anion forming the photo cation polymerization initiator include a specific phosphorus anion [ (Rf) _n PF _6-n ] ^- Hexafluorophosphate radical anion PF ₆ ^- Hexafluoroantimonate anion SbF ₆ ^- Pentafluoro-hydroxyl antimonate anion SbF ₅ (OH) ^- Hexafluoroarsenate anion AsF ₆ ^- Tetrafluoroborate anion BF ₄ ^- Tetrakis (pentafluorophenyl) borate anion B (C) ₆ F ₅ ) ₄ ^- And the like. Among them, the photo cation polymerization initiator is preferably a special phosphorus anion [ (Rf) from the viewpoints of curability of the polymerizable compound and safety of the obtained second cured product layer _n PF _6-n ] ^- Hexafluorophosphate radical anion PF ₆ ^- 。

The photo cation polymerization initiator may be used alone in 1 kind, or may be used in combination of two or more kinds. Among them, the aromatic sulfonium salt is preferable because it has ultraviolet absorption characteristics even in the wavelength region of about 300nm, and thus can provide a cured product having excellent curability and good mechanical strength and adhesive strength.

The content of the polymerization initiator in the cationically polymerizable composition is usually 0.5 part by mass or more and 10 parts by mass or less, preferably 6 parts by mass or less, and more preferably 3 parts by mass or less, based on 100 parts by mass of the polymerizable compound. When the content of the polymerization initiator is within this range, the polymerizable compound can be sufficiently cured, and a cured product layer formed from the obtained cured product can be provided with high mechanical strength and adhesive strength.

The cationically polymerizable composition may contain, if necessary, additives generally used in curable compositions. Examples of such additives include ion traps, antioxidants, chain transfer agents, polymerization accelerators (e.g., polyhydric alcohols), sensitizers, sensitization aids, light stabilizers, tackifiers, thermoplastic resins, fillers, flow control agents, plasticizers, defoaming agents, leveling agents, silane coupling agents, pigments, antistatic agents, and ultraviolet absorbers.

Examples of the sensitizer include photosensitizers. The photosensitizer is a compound which exhibits a maximum absorption at a wavelength longer than the maximum absorption wavelength exhibited by the photo cation polymerization initiator, and promotes the polymerization initiation reaction with the photo cation polymerization initiator. In addition, the photosensitizing assistant is a compound that further promotes the action of the photosensitizer. By blending a photosensitizer and a photosensitizing assistant, a cured layer having desired properties can be formed even when the polarizing plate includes a film having low UV transmittance.

The photosensitizer is preferably a compound that shows maximum absorption, for example, for light of a wavelength longer than 380 nm. Examples of the photosensitizer include anthracene compounds described below.

9, 10-dimethoxy anthracene,

9, 10-diethoxyanthracene,

9, 10-dipropoxyanthracene,

9, 10-diisopropoxylanthracene,

9, 10-dibutoxyanthracene,

9, 10-dipentyloxy anthracene,

9, 10-dihexyloxyanthracene,

9, 10-bis (2-methoxyethoxy) anthracene,

9, 10-bis (2-ethoxyethoxy) anthracene,

9, 10-bis (2-butoxyethoxy) anthracene,

9, 10-bis (3-butoxypropoxy) anthracene,

2-methyl-or 2-ethyl-9, 10-dimethoxyanthracene,

2-methyl-or 2-ethyl-9, 10-diethoxyanthracene,

2-methyl-or 2-ethyl-9, 10-dipropoxyanthracene,

2-methyl-or 2-ethyl-9, 10-diisopropoxylanthracene,

2-methyl-or 2-ethyl-9, 10-dibutoxyanthracene,

2-methyl-or 2-ethyl-9, 10-dipentyloxy anthracene,

2-methyl-or 2-ethyl-9, 10-dihexyloxyanthracene.

The leveling agent is an additive having a function of adjusting the fluidity of the curable composition to make a coating film obtained by applying the composition more flat, and examples thereof include silicone-based, polyacrylate-based, and perfluoroalkyl-based leveling agents such as silane coupling agents. Commercially available leveling agents can also be used.

The content of the leveling agent is preferably 0.01 part by mass or more and 5 parts by mass or less, and more preferably 0.05 part by mass or more and 3 parts by mass or less, with respect to 100 parts by mass of the polymerizable compound.

When the content of the leveling agent is within this range, the second cured product layer tends to become smoother.

The thickness of the second cured product layer is preferably 0.1 μm or more and 10 μm or less, and more preferably 0.2 μm or more and 2 μm or less. When the thickness of the second cured material layer is within this range, the retardation layer can be further protected and the dichroic dye can be prevented from diffusing from the polarizer, and the polarizing plate can be made thinner.

The second cured material layer can be formed by applying an uncured second cured material layer forming composition to the surface of the first cured material layer 20 or the surface of the retardation layer 40 provided in contact with the polarizing plate 10, or by dropping an uncured second cured material layer forming composition between the first cured material layer 20 and the retardation layer 40, overlapping the polarizing plate 10 provided with the first cured material layer 20 and the retardation layer 40 with the uncured second cured material layer forming composition interposed therebetween, pressing and bonding the polarizing plate 10 and the retardation layer 40 from above and below using a bonding roller or the like, for example, and then curing the second cured material layer forming composition. Curing can be carried out by curing by irradiation with an active energy ray (in the case of an active energy ray-curable composition) or curing by heating (in the case of a thermosetting composition). The active energy ray may be irradiated from the polarizing plate 10 side or from the retardation layer 40 side.

For coating the uncured second cured product layer-forming composition, various coating methods such as a doctor blade, a wire bar, a die coater, a comma type blade coater, and a gravure coater can be used. Further, a method of casting an adhesive between bonded layers may be employed.

The irradiation conditions of the active energy ray may be any suitable conditions as long as the active energy ray-curable composition can be cured. For example, the acceleration voltage for electron beam irradiation is preferably 5kV to 300kV, and more preferably 10kV to 250 kV. If the acceleration voltage is less than 5kV, the electron beam may not reach the active energy ray-curable composition, resulting in insufficient curing, and if the acceleration voltage is more than 300kV, the penetration force through the sample becomes too strong, and the electron beam is repelled, possibly damaging the film or the polarizing plate. The irradiation dose is 5 to 100kGy, and more preferably 10 to 75 kGy. When the irradiation dose is less than 5kGy, the active energy ray-curable composition is insufficiently cured, and when it exceeds 100kGy, the retardation layer is damaged, the mechanical strength is reduced, yellowing occurs, and desired optical characteristics cannot be obtained.

The electron beam irradiation is usually carried out in an inert gas, but may be carried out in the atmosphere under a condition of introducing a small amount of oxygen, if necessary.

The ultraviolet-curable composition is not particularly limited, as long as the irradiation intensity of the active energy ray-curable composition is determined according to the composition, but is preferably 10 to 1000mJ/cm ² . If the light irradiation intensity is less than 10mJ/cm ² The reaction time is too long, and if the reaction time is more than 1000mJ/cm ² The composition may be generated by heat emitted from a light source or heat generated during polymerization of the adhesiveYellowing of the constituent material (1). The irradiation intensity is preferably an intensity in a wavelength region of a wavelength of 400nm or less, and more preferably an intensity in a wavelength region of 280 to 320 nm. The irradiation is performed 1 or more times at such light irradiation intensity, and the cumulative light amount is preferably set to 10mJ/cm ² The above is preferably set to 100 to 1000mJ/cm ² . If the cumulative amount of light irradiated to the composition is less than 10mJ/cm ² The generation of active species from the polymerization initiator is insufficient, and the curing of the composition becomes insufficient. On the other hand, if the integrated quantity of light is more than 1000mJ/cm ² The irradiation time becomes very long, which is disadvantageous in productivity improvement. In this case, the required integrated light amount in which wavelength region (UVA (320 to 390nm), UVB (280 to 320nm), etc.) is required differs depending on the type of film used, the combination of compositions, and the like.

The light source used for the polymerization and curing of the composition by irradiation with active energy rays in the present invention is not particularly limited, and examples thereof include a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a xenon lamp, a halogen lamp, a carbon arc lamp, a tungsten lamp, a gallium lamp, an excimer laser, an LED light source emitting light having a wavelength range of 380 to 440nm, a chemical lamp, a black light, a microwave-excited mercury lamp, and a metal halide lamp. From the viewpoint of stability of energy and simplicity of the device, an ultraviolet light source having an emission distribution at a wavelength of 400nm or less is preferable.

In the case of using the active energy ray-curable composition, the heat treatment may be performed simultaneously with the irradiation with the active energy ray or after the irradiation with the active energy ray. Before forming the coating layer of the composition, one or both of the surfaces to be bonded may be subjected to an easy adhesion treatment such as saponification treatment, corona discharge treatment, plasma treatment, flame treatment, undercoating treatment, or anchor coating treatment.

The glass transition temperature of the second cured product layer is, for example, 0 ℃ or higher, and may be 20 ℃ or higher or 50 ℃ or higher. The glass transition temperature of the second cured product layer is, for example, 150 ℃.

The glass transition temperature of the second cured product layer can be calculated by the following procedure. A second cured product layer was formed between 2 stretched films of a cyclic polyolefin resin having a thickness of 25 μm. A vessel containing the measurement sample was placed in a differential scanning calorimeter (DS, TA Instruments co. ltd.) and the temperature was decreased from 20 ℃ to-60 ℃ while purging nitrogen gas, and the temperature was maintained at-60 ℃ for 1 minute, then increased from-60 ℃ to 150 ℃ at a rate of 10 ℃/minute, and immediately decreased to 20 ℃ after reaching 150 ℃. Thereafter, the glass transition temperature at the midpoint specified in JIS K7121 and 1987, "method for measuring the transition temperature of plastics", was determined from the DSC curve at the time of raising the temperature from-60 ℃ to 150 ℃ and was used as the glass transition temperature of the second cured product layer.

From the viewpoint of improving the durability of the polarizing plate, the storage modulus of the second cured product layer at 30 ℃ is preferably 100MPa or more, more preferably 1000MPa or more, further preferably 1500MPa or more, and particularly preferably 2000MPa or more. On the other hand, if the storage modulus of the second cured material layer is too large, the adhesive cured layer may become too hard, and the processability of the polarizing plate may be reduced. Therefore, the storage modulus at 30 ℃ of the cured adhesive layer is preferably 10000MPa or less, more preferably 8000MPa or less, and still more preferably 5000MPa or less.

The storage modulus of the second cured product layer at a temperature of 80 ℃ is, for example, 10MPa or more or 20MPa or more, preferably 100MPa or more or 1000MPa or more. The storage modulus of the second cured product layer at a temperature of 80 ℃ is preferably 5000MPa or less, more preferably 4000MPa or less, and still more preferably 3500MPa or less.

The storage modulus of the second cured product layer can be calculated by the following procedure. A second cured product layer was formed between 2 sheets of cyclic polyolefin resin films having a thickness of 50 μm. The resultant was cut into a size of 5mm × 30mm, and the one cyclic polyolefin resin film was peeled off to obtain a second cured product layer with a resin film. The second cured product layer with the resin film was held at intervals of 2cm by a jig using a dynamic viscoelasticity measuring apparatus "DVA-220" manufactured by the IT measurement control (アイティー , japan) such that the long side thereof was the stretching direction, and the storage modulus at each temperature was determined by raising the temperature with the stretching and shrinking frequency set to 10Hz and the temperature raising rate set to 10 ℃/min.

< method for producing optical laminate >

The method for producing the optical laminate is not particularly limited. One embodiment includes: a step of applying a polyvinyl alcohol resin composition to the surface of the polarizing plate and curing the composition to form a first cured product layer; and a step of laminating the first cured product layer formed on the surface of the polarizing plate and the phase difference layer with the cationic polymerizable composition interposed therebetween, and curing the cationic polymerizable composition to form a second cured product layer.

< image display device >

The image display device includes an image display panel and the polarizing plate described above. In the image display device, the polarizing plate may be disposed on the front surface (visible side) of the image display panel, for example. 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 type display panel. The circularly polarizing plate may be disposed on the viewing side of the organic EL display device to form an image display device.

The image display device of the present invention can be used as mobile devices such as smart phones and tablet computers, televisions, digital photo frames, electronic billboards, measuring instruments, office equipment, medical equipment, electronic computer equipment, and the like. The image display device of the present invention has excellent durability even when used in a severe environment.

Examples

The present invention will be described in more detail 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 polarizing plate, the first cured material layer, the second cured material layer, and the phase difference layer given below.

< preparation of laminate in example 1 >

[ production of polarizing plate with substrate film ]

A film having a hard coat layer on one surface of a polyethylene terephthalate (PET) film having a thickness of 38 μm was used as a substrate film. The surface of the substrate film on the hard coat layer side was subjected to corona treatment, and thereafter, a photo-alignment film was formed. The composition for forming a polarizing plate, which is obtained by mixing a polymerizable liquid crystal compound, a dichroic azo dye, a polymerization initiator, a leveling agent, and a solvent, is applied to the photo-alignment film, dried, and then irradiated with UV to form a polarizing plate. Then, a surface protective film is laminated on the base film side.

[ formation of the first cured product layer ]

The polarizing plate side surface of the manufactured polarizing plate with the substrate film was subjected to corona treatment. The surface of the polarizer-side surface after the corona treatment was coated with a polyvinyl alcohol resin composition by a bar coating method (speed 30 mm/sec) so that the cured film thickness became 1.0. mu.m. The conditions of the corona treatment were 800W of output, 10 m/min of treatment speed and 1 time. As the polyvinyl alcohol resin composition, a composition obtained by preparing acetoacetyl-modified polyvinyl alcohol (trade name "Z-220", Mitsubishi chemical corporation) from pure water was used. The details of Z-220 are shown in Table 1. The coating layer of the polyvinyl alcohol resin composition was dried at 100 ℃ for 2 minutes to obtain a polarizing plate having a first cured product layer.

[ preparation of retardation layer ]

A laminate of the 1 st protective film/alignment film/1/4 wavelength plate layer/adhesive layer/positive C layer/alignment film/2 nd protective film was prepared as a retardation layer. The 1/4 wavelength plate layer and the positive C layer are each a layer obtained by applying a composition containing a polymerizable liquid crystal compound onto an alignment film, drying, UV-irradiating the composition, and curing the composition. The 1 st protective film is a PET film with a thickness of 100 μm, and the 2 nd protective film is a PET film with a thickness of 38 μm.

[ lamination of polarizing plate with first cured product layer and retardation layer ]

The polarizing plate with the first cured product layer was peeled off from the first cured product layer-side surface of the polarizing plate and the 1 st protective film of the retardation layer, and the exposed surface was subjected to corona treatment. The conditions of the corona treatment were 800W of output, 10 m/min of treatment speed and 1 time. The two-layered product was bonded using a laminator while applying an ultraviolet-curable cationic polymerizable composition between the surface of the corona-treated first cured product and the surface of the phase difference layer.

The thickness of the second cured layer was 1.5 μm. The lamination conditions were at a speed of 2.5 m/min. Using an ultraviolet irradiation apparatus at UVB400mJ/cm ² The ultraviolet rays were irradiated 1 time. The lamp used was an "H-tube" manufactured by Fusion UV Systems. The environment during the ultraviolet irradiation was 23 ℃ and 55% RH relative to the relative humidity. By the above operation, the polarizing plate of example 1 in which the polarizing plate including the dichroic azo dye, the first cured material layer, the second cured material layer, and the retardation layer including the cured product of the polymerizable liquid crystal compound were laminated in contact with each other in this order was obtained.

(preparation of cationically polymerizable composition)

The components shown in table 2 below were mixed in the mixing ratios (unit is part by mass) shown in table 2, and then defoamed to prepare a cationic polymerizable composition. The cationic polymerization initiator (B-1) was blended as a 50% propylene carbonate solution, and the amount of solid components thereof is shown in table 2. The glass transition temperature and the storage modulus were measured according to the above-mentioned description of [ second cured product layer ].

< production of laminates according to examples 2 to 7 >

A polarizing plate of example 2 was produced in the same manner as in example 1, except that the polyvinyl alcohol resin composition used for the first cured product layer was changed to "Z-200" as a product name shown in table 1. Polarizing plates of examples 3 to 6 were produced in the same manner as in example 2, except that glyoxal was further added to the polyvinyl alcohol resin composition in the blending amount shown in table 3. A polarizing plate of example 7 was produced in the same manner as in example 1, except that the polyvinyl alcohol resin composition used for the first cured product layer was changed to the one having the product name "PVA 117" shown in table 1.

[ TABLE 1]

[ TABLE 2]

Compound (I)	Content (wt.)
		A-1	32.5
A-2	7.5
		A-3	60
B-1	2.25
		C-1	2
Glass transition temperature	140
		Storage modulus (MPa) at a temperature of 30 DEG C	2300
Storage modulus (MPa) at a temperature of 80 DEG C	1400

The compounds in table 2 are shown below.

(cationically polymerizable Compound (A))

A-1: 3, 4-epoxycyclohexanecarboxylic acid 3 ', 4' -epoxycyclohexylmethyl ester (trade name: CEL2021P, manufactured by Daicel K.K.)

A-2: 1, 2-epoxy-4- (2-epoxyethyl) cyclohexane adduct of 2, 2-bis (hydroxymethyl) -1-butanol (trade name: EHPE3150, manufactured by Daicel K.K.)

A-3: 3-Ethyl-3 { [ (3-ethyloxetan-3-yl) methoxy ] methyl } oxetane (trade name: OXT-221, manufactured by Toyo Seisaku-sho Co., Ltd.)

(cationic polymerization initiator (B))

B-1: "CPI-100P", manufactured by San-Apro Co., Ltd., 50% by mass solution

(photosensitive auxiliary (C))

C-1: 1, 4-diethoxynaphthalenes

< production of laminate of comparative example 1 >

As comparative example 1, a laminate was prepared by the following procedure, in which the first cured material layer and the second cured material layer were not provided, and the polarizing plate and the retardation layer were bonded via the adhesive layer.

First, a pressure-sensitive adhesive sheet was prepared in which an acrylic pressure-sensitive adhesive layer having a thickness of 5 μm was provided as a pressure-sensitive adhesive layer between a light-releasable film and a heavy-releasable film. The polarizing plate side of the polarizing plate with a substrate film described in example 1 was bonded to the exposed surface of the pressure-sensitive adhesive sheet from which the light-peelable film was peeled. Before the lamination, 1 corona treatment was performed on the surface of the polarizing plate at an output of 800W and a processing speed of 10 m/min, and 3 corona treatments were performed on the surface of the adhesive layer at an output of 280W and a processing speed of 10 m/min. The exposed surface of the retardation layer described in example 1 from which the 1 st protective film was peeled and the exposed surface of the adhesive sheet from which the heavy release sheet was peeled were bonded to each other. Before the lamination, 1 corona treatment was performed on the surface of the retardation layer at an output of 800W and a processing speed of 10 m/min, and 3 corona treatments were performed on the surface of the pressure-sensitive adhesive layer at an output of 280W 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 for the contents specifically described.

< production of laminate of comparative example 2 >

As comparative example 2, a laminate was prepared in which the polarizing plate with the first cured product layer was bonded to the retardation layer via an adhesive layer without using the second cured product layer. The laminate of comparative example 2 was obtained in the same manner as in the production method of the laminate of comparative example 1, except that the polarizing plate with the first cured product layer of example 2 was used as the polarizing plate. That is, the pressure-sensitive adhesive layer was laminated on the first cured product layer side of the polarizing plate with the first cured product layer described in example 1, and the 1/4 wavelength plate layer side of the retardation layer described in example 1 was further laminated on the side opposite to the first cured product layer of the pressure-sensitive adhesive layer.

Production of laminate of < comparative example 3 >

As comparative example 3, a laminate was obtained in which the polarizing plate with the first cured product layer and the retardation layer were bonded via the second cured product layer and the adhesive layer. First, the polarizing plate with the first cured product layer of example 2 was prepared.

The first cured product layer side of the polarizing plate with the first cured product layer was subjected to corona treatment, and the two-layered laminate was bonded using a laminator while applying a cationic polymerizable composition between the corona-treated surface and the cycloolefin film that was not subjected to corona treatment. After the composition was cured by ultraviolet irradiation to form a second cured product layer, the cycloolefin film was peeled off. Then, the second cured product layer side of the polarizing plate was bonded to the exposed surface of the pressure-sensitive adhesive sheet of comparative example 1 from which the light-peelable film was peeled. Then, the exposed surface of the retardation layer described in example 1 from which the 1 st protective film was peeled and the exposed surface of the adhesive sheet from which the heavy release sheet was peeled were bonded to each other. The laminate of comparative example 3 was obtained by the above procedure. The method other than the method specifically described is the same as in example 1 or comparative example 1.

< evaluation of durability of polarizing plate and retardation layer >

Samples were prepared in which the 2 nd protective film was peeled from the laminates of examples and comparative examples and bonded to an acrylic pressure-sensitive adhesive sheet (with a release film) having a thickness of 15 μm. The laminate was cut into a size of 30mm × 30mm, and adhered to alkali-free glass (trade name: Eagle XG, 40mm × 40mm × thickness 0.7mm) manufactured by Corning using an acrylic pressure-sensitive adhesive layer exposed by peeling off a release film, and subjected to autoclave treatment at a temperature of 50 ℃.

[ measurement of degree of polarization ]

Each sample was placed in an oven set to high temperature (85 ℃ dry) conditions for 168 hours. The visibility correction polarization degree before the oven was put (Py1) (%) and the visibility correction polarization degree after the oven was left for 168 hours (Py2) (%) were measured by a spectrophotometer (V-7100 by japan spectro-photometer), and the change amount, i.e., Δ Py, was calculated based on the following equation.

ΔPy＝|Py2-Py1|

Δ Py was evaluated based on the following criteria.

A: the variation delta Py of the polarization degree is less than 0.5

B: the change amount of polarization degree delta Py is more than 0.5 and less than 1.0

C: the change amount of polarization degree DeltaPy is 1.0 or more

[ measurement of phase difference value ]

Using the same method as above, a test sample was prepared. Each sample was placed in an oven set to high-temperature and high-humidity conditions (temperature 65 ℃ C., relative humidity 90% RH) for 168 hours. The in-plane retardation value (Re1) (nm) at a wavelength of 550nm before charging into the oven and the in-plane retardation value (Re2) (nm) at a wavelength of 550nm after leaving the oven for 168 hours were measured by a retardation measuring device KOBRA-WPR (manufactured by Okinson instruments Co., Ltd.), and the change amount, namely, Δ Re was calculated based on the following formula.

ΔRe＝|Re2-Re1|

Δ Re was evaluated based on the following criteria.

A: the variation amount Delta Re of the phase difference value is less than 0.5

B: the variation amount Delta Re of the retardation value is 0.5 or more and less than 2.5

C: the variation amount Delta Re of the retardation value is 2.5 or more

[ Warm Water immersion test ]

A sample in which a polarizing plate was laminated on an alkali-free glass was prepared in the same manner as above. The sample was cut into a size of 50mm × 20mm in a strip shape with the absorption axis of the polarizing plate as the long side, and the dimension in the long side direction was accurately measured. One short side of the sample was held by a holder, and the sample was immersed in a water bath at 60 ℃ for 3 minutes at about 8 points in the longitudinal direction. Thereafter, the sample was taken out from the water tank, and water was wiped off. The polarizer of the polarizing plate shrinks due to immersion in warm water. The degree of shrinkage of the polarizing plate was measured as the distance from the end of the sample (end of the glass) to the end of the shrunk polarizing plate at the center of the short side of the sample. The obtained measurement values were evaluated according to the following criteria.

A: the distance from the end of the sample to the end of the polarizing plate is 3mm or less

B: the distance from the end of the sample to the end of the polarizer was more than 3mm

[ TABLE 3]

In a polarizing plate in which a polarizing plate is laminated in contact with a first cured material layer, a second cured material layer, and a retardation layer in this order, the first cured material layer being a cured material layer of a polyvinyl alcohol resin composition, and the second cured material layer being a cured material layer of a cationically polymerizable composition, Δ Py at a temperature of 85 ℃ is small, and it is considered that diffusion of a coloring matter of the polarizing plate at a high temperature is suppressed. In such a polarizing plate, Δ Re at 65 ℃ and 90% RH is small, and it is considered that monomer diffusion in the retardation layer under high temperature and high humidity is suppressed. It is also found that when the polyvinyl alcohol resin composition contains acetoacetyl-modified polyvinyl alcohol, the water resistance is also improved.

Claims

1. A polarizing plate comprising a dichroic azo dye, a first cured layer, a second cured layer, and a phase difference layer comprising a cured product of a polymerizable liquid crystal compound, which are laminated in contact with each other in this order,

2. The polarizing plate of claim 1,

the polyvinyl alcohol resin composition contains acetoacetyl-modified polyvinyl alcohol.

3. The polarizing plate according to claim 1 or 2,

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 claims 1 to 3,

the polymerization degree of the polyvinyl alcohol resin contained in the polyvinyl alcohol resin composition is 1000 or more and 5000 or less.

5. The polarizing plate according to any one of claims 1 to 4,

the polyvinyl alcohol resin composition contains no aldehyde compound, or contains 8.0 parts by mass or less of an aldehyde compound per 100 parts by mass of the polyvinyl alcohol resin.

6. The polarizing plate according to any one of claims 1 to 5,

the cationically polymerizable composition comprises an oxetane compound.

7. The polarizing plate of claim 6,

the cationically polymerizable composition also comprises an epoxy compound.

8. The polarizing plate of claim 7,

the cationic polymerizable composition contains the oxetane compound in an amount of 10 parts by mass or more and 2000 parts by mass or less with respect to 100 parts by mass of the epoxy compound.

9. The polarizing plate according to any one of claims 1 to 8,

the cationically polymerizable composition also comprises a photosensitizer.

10. The polarizing plate according to any one of claims 1 to 9,

the phase difference layer comprises an 1/4 wavelength plate layer.

11. An image display device comprising the polarizing plate according to any one of claims 1 to 10.