CN111527427A

CN111527427A - Polarizing plate

Info

Publication number: CN111527427A
Application number: CN201880084205.9A
Authority: CN
Inventors: 白石贵志; 中村大地
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2017-12-28
Filing date: 2018-12-25
Publication date: 2020-08-11
Anticipated expiration: 2038-12-25
Also published as: WO2019131624A1; TWI822718B; CN111527427B; TW201934699A; JP2023174657A; JP2019120950A; KR20200103699A

Abstract

The present invention relates to a polarizing plate (100) comprising a polarizing plate (11), a 1 st adhesive layer (12), a retardation layer (14), and a 2 nd adhesive layer (13) in this order, wherein the storage elastic modulus of the 1 st adhesive layer (12) is represented by E₁(Pa) and the thickness of the 1 st pressure-sensitive adhesive layer (12) is T₁The storage elastic modulus of the 2 nd adhesive layer (13) is E₂(Pa) and the thickness of the 2 nd pressure-sensitive adhesive layer (13) is T₂(. mu.m), satisfies Log (E)₁/T₁)+Log(E₂/T₂)≥6.4。

Description

Polarizing plate

Technical Field

The present invention relates to a polarizing plate.

Background

In recent years, image display devices typified by liquid crystal display devices and organic electroluminescent display devices (hereinafter, also referred to as organic EL devices) have been rapidly spreading. Polarizing plates provided with a polarizing plate and a phase difference layer are widely used in image display devices.

Recently, due to the increasing tendency of organic EL, thinning of polarizing plates is also required with the enhancement of the demand for thinning of image display devices. In addition, in view of flexible applications, studies have been made on using a polymerizable liquid crystal compound having higher toughness as a raw material of a retardation layer based on a conventional retardation film (for example, see patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2017-54093

Disclosure of Invention

Problems to be solved by the invention

On the other hand, when the thinning of the polarizing plate is attempted, there is a problem that the durability of the polarizing plate becomes insufficient. In particular, when a polarizing plate is exposed to a high-temperature and high-humidity environment, a defect that wrinkles are generated in the polarizing plate may occur.

The wrinkles of the polarizing plate distort an image of an image display device typified by an organic EL. Therefore, there is a problem that the wrinkles of the polarizing plate significantly impair the visibility of the image display device. With the progress of waterproof technology for mobile phones and the like, there are more and more people who use mobile phones and the like in bathrooms, saunas and the like in high-temperature and high-humidity environments. Accordingly, there is an increasing demand for polarizing plates having durability in high-temperature, high-humidity environments.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a polarizing plate having high durability, which can suppress the occurrence of wrinkles in the polarizing plate even in a high-temperature and high-humidity environment.

Means for solving the problems

As a result of intensive studies, the present inventors have found that the following polarizing plates can solve the above problems.

That is, the present invention has the following configuration.

[1] A polarizing plate comprising a polarizing plate, a 1 st adhesive layer, a retardation layer, and a 2 nd adhesive layer in this order,

the storage elastic modulus of the 1 st pressure-sensitive adhesive layer is represented by E₁(Pa), and the thickness of the 1 st pressure-sensitive adhesive layer is T₁(μm) and the storage elastic modulus of the 2 nd pressure-sensitive adhesive layer is E₂(Pa), and the thickness of the 2 nd pressure-sensitive adhesive layer is T₂(. mu.m), satisfies Log (E)₁/T₁)+Log(E₂/T₂)≥6.4。

[2] The polarizing plate according to [1], wherein the puncture strength of the phase difference layer is 100gf or less.

[3] The polarizing plate according to [1] or [2], wherein either one of the following (1) and (2) is satisfied.

(1) Log (E) above₁/T₁) Is 3.1 or more.

(2) Log (E) above₂/T₂) Is 3.0 or more.

[4] The polarizing plate according to any one of [1] to [3], wherein at least one of the 1 st adhesive layer and the 2 nd adhesive layer has a storage elastic modulus of 20,000Pa or more.

[5] The polarizing plate according to any one of [1] to [4], wherein a thickness of at least one of the 1 st adhesive layer and the 2 nd adhesive layer is 40 μm or less.

[6] The polarizing plate according to any one of [1] to [5], wherein the retardation layer includes at least a 1 st retardation layer and a 2 nd retardation layer.

[7] The polarizing plate according to [6], wherein the retardation layer is a laminate in which at least a 1 st retardation layer and a 2 nd retardation layer are laminated via an adhesive layer.

[8] The polarizing plate according to [7], wherein the laminate has a puncture strength of 100gf or less.

Effects of the invention

According to the present invention, a polarizing plate having high durability can be provided, which can suppress the occurrence of wrinkles in the polarizing plate even in a high-temperature and high-humidity environment.

Drawings

Fig. 1 is a schematic cross-sectional view showing an example of the structure of a polarizing plate according to embodiment 1.

Fig. 2 is a schematic cross-sectional view showing a structure of a polarizing plate including 2 retardation layers according to embodiment 2.

Fig. 3 is a schematic cross-sectional view showing a structure of a polarizing plate including 3 retardation layers according to embodiment 2.

Detailed Description

Hereinafter, a specific embodiment of the polarizing plate of the present invention will be described in detail. The present invention is not limited to the following embodiments, and various modifications can be made without departing from the scope of the present invention.

[ embodiment 1]

< polarizing plate >

In the present specification, the term "polarizing plate" refers to an optical film including a polarizer and a retardation layer. The polarizing plate according to embodiment 1 includes a polarizing plate, a 1 st adhesive layer, a retardation layer, and a 2 nd adhesive layer in this order.

Fig. 1 is a schematic cross-sectional view showing an example of the structure of a polarizing plate according to embodiment 1. As shown in fig. 1, a polarizing plate 100 includes a polarizer 11, a 1 st adhesive layer 12, a retardation layer 14, and a 2 nd adhesive layer 13 stacked in this order.

Here, the retardation layer 14 is, for example, a layer that imparts a retardation of λ/2, a layer that imparts a retardation of λ/4, a positive C layer, and a layer obtained by laminating a combination of these layers. Examples of the laminate obtained by the combination include a laminate of a layer having a retardation of λ/2 and a layer having a retardation of λ/4, a laminate of a layer having a retardation of λ/4 and a positive C layer, and the like.

In the present specification, the term "layer for imparting a retardation of λ/2" refers to a retardation layer for converting the polarization direction of linearly polarized light of a specific wavelength by 90 °. In the present specification, the "layer for imparting a retardation of λ/4" refers to a retardation layer for converting linearly polarized light of a specific wavelength into circularly polarized light (or converting circularly polarized light into linearly polarized light). When the retardation layer 14 is a layer that imparts a retardation of λ/4, the polarizing plate 100 including the polarizer 11 and the retardation layer 14 functions as a circular polarizing plate. In the present specification, the "positive C layer" means a layer satisfying a relationship of Nz > Nx ≧ Ny where Nx is a refractive index in the slow axis direction in a plane, Ny is a refractive index in the fast axis direction in the plane, and Nz is a refractive index in the thickness direction. The difference between the value of Nx and the value of Ny is preferably within 0.5%, more preferably within 0.3% of the value of Ny. If the ratio is within 0.5%, Nx ═ Ny can be regarded as being substantial.

When the polarizing plate having the above-described structure is stored in a high-temperature and high-humidity environment, wrinkles may be generated in the polarizing plate. The inventors have conducted studies and, as a result, have confirmed that the retardation layer of the polarizing plate, which was wrinkled after being stored in a high-temperature and high-humidity environment, was deformed. Such phenomena suggest: in a high-temperature and high-humidity environment, stress that deforms the retardation layer acts. The stress for deforming the retardation layer is considered to have a large influence on the adhesive in contact with the retardation layer.

As a result of further studies, the inventors have found that wrinkles can be suppressed after the polarizing plate is stored in a high-temperature and high-humidity environment by controlling the composition of the pressure-sensitive adhesive layer in contact with the retardation layer in the polarizing plate having the above-described configuration. That is, the following idea was obtained, and the invention was completed: in the polarizing plate having the above-described configuration, stress applied to the retardation layer can be suppressed by controlling the configuration of the adhesive in contact with the retardation layer.

Hereinafter, each layer constituting the polarizing plate 100 of the present embodiment will be described in detail.

< polarizing plate >

The polarizing plate 100 of the present embodiment includes a polarizer 11. In the present specification, the "polarizing plate" refers to an optical film having the following properties: when unpolarized light is incident, linearly polarized light having a vibration plane perpendicular to the absorption axis is transmitted.

As the polarizing plate, any suitable polarizing plate can be used. For example, the resin film forming the polarizing plate may be a single-layer resin film or a laminate of two or more layers. The polarizing plate may be a cured film obtained by aligning a dichroic dye in a polymerizable liquid crystal compound and polymerizing the polymerizable liquid crystal compound.

Specific examples of the polarizing plate made of a single-layer resin film include: a product obtained by subjecting a hydrophilic polymer film such as a polyvinyl alcohol (hereinafter, may be abbreviated as PVA) film, a partially formalized PVA film, or an ethylene-vinyl acetate copolymer partially saponified film to a dyeing treatment with a dichroic material such as iodine or a dichroic dye, and a stretching treatment; and polyene-based oriented films such as dehydrated products of PVA and dehydrochlorinated products of polyvinyl chloride. From the viewpoint of excellent optical properties, a polarizing plate obtained by dyeing a PVA-based film with iodine and uniaxially stretching the film is preferably used.

The polyvinyl alcohol resin as a raw material of the PVA-based film can be produced by saponifying a polyvinyl acetate resin. The polyvinyl acetate-based resin may be a copolymer of vinyl acetate and another monomer copolymerizable with vinyl acetate, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

The saponification degree of the polyvinyl alcohol resin is usually about 85 to 100 mol%, and preferably 98 mol% or more. The polyvinyl alcohol resin may be modified, and for example, polyvinyl formal, polyvinyl acetal, or the like modified with aldehydes may be used. The polymerization degree of the polyvinyl alcohol resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000.

A film obtained by forming such a polyvinyl alcohol resin into a film can be used as a PVA film. The method for forming the polyvinyl alcohol resin film is not particularly limited, and the film can be formed by a known method. The PVA film has a film thickness of, for example, about 10 to 100 μm, preferably about 10 to 50 μm.

The thickness of the polarizing plate is preferably 2 μm or more, more preferably 3 μm or more, and further preferably 5 μm or more. The thickness of the polarizing plate is preferably 30 μm or less, more preferably 20 μm or less, and still more preferably 15 μm or less. The upper limit value and the lower limit value may be arbitrarily combined.

When the thickness of the polarizing plate is reduced, iodine at the end of the polarizing plate is easily released in a high-temperature and high-humidity environment. Therefore, the thickness of the polarizing plate is preferably 5 μm or more. When the thickness of the polarizing plate is large, breakage of the polarizing plate is likely to occur in the heat exchange test. Therefore, the thickness of the polarizing plate is preferably 15 μm or less.

In the present specification, "thickness of a layer" refers to a dimension in the lamination direction of the layers in the polarizing plate. Examples of the "layer" in the present embodiment include a polarizing plate, an adhesive layer, a retardation layer, and a protective film. The thickness of the layer can be obtained by measuring an arbitrary point of the layer using a white light interference type noncontact film thickness meter or a contact type film thickness meter, and calculating the average value thereof. When a noncontact film thickness meter is used, the film thickness can be measured accurately without contacting the object to be measured, and even if the object to be measured is a layer that is a part of the laminate, the film thickness of the object can be measured without peeling off each layer.

In the case where a protective film described later is laminated on one surface or both surfaces of the polarizing plate, the thickness of the polarizing plate does not include the thickness of the protective film.

The polarizing plate may have a protective film laminated on one or both surfaces thereof via an adhesive layer or an adhesive layer, which will be described later. As the protective film that can be laminated on one surface or both surfaces of the polarizing plate, for example, a film formed of a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, stretchability, and the like can be used. Specific examples of such thermoplastic resins include: cellulose resins such as triacetyl cellulose; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polyether sulfone resin; polysulfone resin; a polycarbonate resin; polyamide resins such as nylon and aromatic polyamide; a polyimide resin; polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymers; a cyclic polyolefin resin having a ring system and a norbornene structure (also referred to as norbornene-based resin); a (meth) acrylic resin; a polyarylate resin; a polystyrene resin; a polyvinyl alcohol resin; and mixtures thereof.

When protective films are laminated on both surfaces of the polarizing plate, the resin compositions of the two protective films may be the same or different.

In order to improve adhesion to a polarizing plate containing a PVA-based resin and a dichroic material, a film made of a thermoplastic resin may be subjected to a surface treatment (e.g., corona treatment) or may be formed with a thin layer such as a primer layer (also referred to as an undercoat layer).

The moisture permeability of the protective film at 40 ℃ and 90% RH is preferably 1-1500 g/m²24 hr. When the moisture permeability of the protective film is more than 1500g/m²In 24hr, wrinkles may easily occur in the polarizing plate including the protective film in a high-temperature and high-humidity environment. The lower the moisture permeability of the protective film, the more remarkable the wrinkle preventing effect of the polarizing plate comprising the protective film, and the more preferable the moisture permeability at 40 ℃ and 90% RH is 1000g/m²24hr or less, more preferably 100g/m²24hr or less. The moisture permeability may be measured according to JIS Z0208: 1976 and making determination.

The thickness of the protective film is preferably 3 μm or more, and more preferably 5 μm or more. The thickness of the protective film is preferably 50 μm or less, and more preferably 30 μm or less. The upper limit value and the lower limit value may be arbitrarily combined.

When one or both surfaces of the polarizer have a protective film, the polarizer can be sufficiently reinforced, and thus various durability of the polarizing plate is improved.

< 1 st adhesive layer >

The polarizing plate and the retardation layer are laminated via the 1 st adhesive layer.

In the present specification, the "pressure-sensitive adhesive" refers to a substance that is soft and rubbery and exhibits adhesiveness by attaching itself to an adherend such as the polarizing plate or the protective film. The active energy ray-curable adhesive described later can be adjusted in adhesive strength by irradiation with an energy ray.

As the adhesive constituting the 1 st adhesive layer, conventionally known adhesives having excellent optical transparency can be used without particular limitation, and for example, adhesives having a base polymer such as acrylic, urethane, silicone, or polyvinyl ether can be used. Further, an active energy ray-curable adhesive, a thermosetting adhesive, or the like may be used. Among them, an acrylic resin excellent in transparency, adhesive force, removability (hereinafter, also referred to as recyclability), weather resistance, heat resistance and the like is preferable as the adhesive of the base polymer. In the present embodiment, the 1 st adhesive layer is preferably composed of a reaction product of an adhesive composition containing a (meth) acrylic resin (1), a crosslinking agent (2), and a silane compound (3).

[ (meth) acrylic resin (1) ]

In the present embodiment, the (meth) acrylic resin (1) included in the adhesive composition constituting the 1 st adhesive layer is preferably a polymer (hereinafter, also referred to as a "(meth) acrylate polymer") containing, as a main component, (for example, containing 50 mass% or more of a structural unit derived from an alkyl (meth) acrylate represented by the following formula (I) (hereinafter, also referred to as a "structural unit (I)")).

In the present specification, "derived from" means that a chemical structure is changed due to polymerization of a compound such as an alkyl (meth) acrylate.

[ chemical formula 1]

In the formula (I), R¹⁰Represents a hydrogen atom or a methyl group, R²⁰Represents an alkyl group having 1 to 20 carbon atoms, the alkyl group may have any of a straight chain, branched or cyclic structure, and a hydrogen atom of the alkyl group may be substituted with an alkoxy group having 1 to 10 carbon atoms.

In the present specification, "(meth) acrylic acid" means either acrylic acid or methacrylic acid. The same applies to "(meth)" such as (meth) acrylate.

Examples of the (meth) acrylic acid ester represented by the formula (I) include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, isohexyl (meth) acrylate, n-heptyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-nonyl and isononyl (meth) acrylates, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-dodecyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, stearyl (meth) acrylate, t-butyl (meth) acrylate, and the like. Specific examples of the alkoxyalkyl acrylate include 2-methoxyethyl (meth) acrylate and ethoxymethyl (meth) acrylate. Among them, n-butyl (meth) acrylate or 2-ethylhexyl (meth) acrylate is preferably contained, and n-butyl (meth) acrylate is particularly preferably contained.

The (meth) acrylate polymer may contain a structural unit derived from another monomer other than the structural unit (I). The number of the structural units derived from other monomers may be 1, or 2 or more. Examples of the other monomers that the (meth) acrylate polymer may contain include a monomer having a polar functional group, a monomer having an aromatic group, and an acrylamide monomer.

Examples of the monomer having a polar functional group include (meth) acrylates having a polar functional group. Examples of the polar functional group include a hydroxyl group, a carboxyl group, a substituted amino group, and an unsubstituted amino group. Examples of the polar functional group include a heterocyclic group such as an epoxy group.

The content of the structural unit derived from the monomer having a polar functional group in the (meth) acrylate polymer is preferably 20 parts by mass or less, more preferably 0.1 part by mass or more and 20 parts by mass or less, further preferably 0.1 part by mass or more and 10 parts by mass or less, and particularly preferably 0.5 part by mass or more and 10 parts by mass or less, relative to 100 parts by mass of the total structural units of the (meth) acrylate polymer.

The monomer having an aromatic group has 1 (meth) acryloyl group and 1 or more aromatic rings (e.g., benzene ring, naphthalene ring, etc.) in the molecule, and examples thereof include (meth) acrylates having a phenyl group, a phenoxyethyl group, or a benzyl group. By including these structural units, the white leakage phenomenon of the polarizing plate occurring in a high-temperature, high-humidity environment can be suppressed.

The content of the structural unit derived from the aromatic group-having monomer in the (meth) acrylate polymer is preferably 50 parts by mass or less, more preferably 4 parts by mass or more and 50 parts by mass or less, and still more preferably 4 parts by mass or more and 25 parts by mass or less, relative to 100 parts by mass of the total structural units of the (meth) acrylate polymer.

Examples of the acrylamide monomer include N- (methoxymethyl) acrylamide, N- (ethoxymethyl) acrylamide, N- (propoxymethyl) acrylamide, N- (butoxymethyl) acrylamide, and N- (2-methylpropyloxymethyl) acrylamide. By including these structural units, bleeding of additives such as an antistatic agent described later can be suppressed.

Further, the structural unit derived from another monomer other than the structural unit (I) may include a structural unit derived from a styrene monomer, a structural unit derived from a vinyl monomer, a structural unit derived from a monomer having a plurality of (meth) acryloyl groups in the molecule, and the like.

The weight average molecular weight (hereinafter also simply referred to as "Mw") of the (meth) acrylic resin (1) is preferably 50 to 250 ten thousand. When the weight average molecular weight is 50 ten thousand or more, the durability of the 1 st adhesive layer in a high-temperature, high-humidity environment can be improved. When the weight average molecular weight is 250 ten thousand or less, the workability when coating the coating liquid containing the adhesive composition becomes good. The molecular weight distribution (Mw/Mn) represented by the ratio of the weight average molecular weight (Mw) to the number average molecular weight (hereinafter also simply referred to as "Mn") is usually 2 to 10. In the present specification, "weight average molecular weight" and "number average molecular weight" are polystyrene equivalent values measured by a Gel Permeation Chromatography (GPC) method.

When the (meth) acrylic resin (1) is dissolved in ethyl acetate to form a 20 mass% solution, the viscosity at 25 ℃ is preferably 20 pas or less, and more preferably 0.1 to 15 pas. When the viscosity of the (meth) acrylic resin (1) at 25 ℃ is in the above range, it contributes to improvement of durability and recyclability of the polarizing plate including the 1 st adhesive layer formed of the above resin. The above viscosity can be measured by using a brookfield viscometer.

From the viewpoint of achieving both the adhesion and the durability, the glass transition temperature of the (meth) acrylic resin (1) is preferably from-60 ℃ to-10 ℃. The glass transition temperature can be measured by a Differential Scanning Calorimeter (DSC).

The (meth) acrylic resin (1) may contain 2 or more kinds of (meth) acrylate polymers. Examples of such a (meth) acrylate polymer include a (meth) acrylate polymer having a relatively low molecular weight, which contains the structural unit (I) derived from a (meth) acrylate as a main component and has a weight average molecular weight of 5 to 30 ten thousand.

[ crosslinking agent (2) ]

The adhesive composition forming the 1 st adhesive layer preferably contains a crosslinking agent (2). The crosslinking agent (2) includes a commonly used crosslinking agent (for example, an isocyanate compound, an epoxy compound, an aziridine compound, a metal chelate compound, a peroxide, etc.), and particularly, an isocyanate compound is preferable from the viewpoints of pot life of the adhesive composition, crosslinking speed, durability of the polarizing plate, and the like.

The isocyanate compound is preferably a compound having at least 2 isocyanate groups (-NCO) in the molecule, and examples thereof include aliphatic isocyanate compounds (e.g., hexamethylene diisocyanate), alicyclic isocyanate compounds (e.g., isophorone diisocyanate), hydrogenated xylylene diisocyanate, hydrogenated diphenylmethane diisocyanate, and aromatic isocyanate compounds (e.g., toluene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, and triphenylmethane triisocyanate). The crosslinking agent (2) may be an adduct (adduct) of the isocyanate compound with a polyol compound [ for example, an adduct with glycerin, trimethylolpropane, or the like ]; an isocyanurate compound; a biuret type compound; and urethane prepolymer type isocyanate compounds and other derivatives that undergo addition reaction with polyether polyols, polyester polyols, acrylic polyols, polybutadiene polyols, polyisoprene polyols, and the like. The crosslinking agent (2) may be used singly or in combination of 2 or more. Among them, toluene diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, and polyol compounds thereof or isocyanurate compounds thereof are preferable from the viewpoint of durability.

The proportion of the crosslinking agent (2) may be, for example, 0.01 to 10 parts by mass, preferably 0.1 to 3 parts by mass, and more preferably 0.1 to 1 part by mass, relative to 100 parts by mass of the acrylic resin (1). When the proportion of the crosslinking agent (2) is not more than the above upper limit, it is advantageous to improve durability, and when the proportion of the crosslinking agent (2) is not less than the above lower limit, it is advantageous to suppress generation of gas and improve recyclability.

[ silane Compound (3) ]

The adhesive composition may contain the silane compound (3). By containing the silane compound (3), the adhesion between the 1 st adhesive layer and the layer laminated on the 1 st adhesive layer can be improved. It is also possible to use 2 or more silane compounds (3).

Examples of the silane compound (3) include vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylethoxydimethylsilane, 2- (3, 4-epoxycyclohexyl) ethyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane, 3-chloropropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane and 3-mercaptopropyltrimethoxysilane.

Further, the silane compound (3) may contain an oligomer derived from the above silane compound (3).

The content of the silane compound (3) in the adhesive composition is usually 0.01 to 10 parts by weight, preferably 0.03 to 5 parts by weight, more preferably 0.05 to 2 parts by weight, and still more preferably 0.1 to 1 part by weight, based on 100 parts by weight of the (meth) acrylic resin (1). When the content of the silane compound (3) is 0.01 part by mass or more, the adhesion of the 1 st pressure-sensitive adhesive layer to the adherend is easily improved. When the content is 10 parts by weight or less, bleeding of the silane compound (3) from the 1 st adhesive layer can be suppressed.

[ other Components (4) ]

The adhesive composition forming the 1 st adhesive layer may contain an additive such as an ultraviolet absorber, an antistatic agent, a solvent, a crosslinking catalyst, a tackifier resin (tackifier), a plasticizer, or 2 or more of them alone. In addition, it is also useful to prepare a harder pressure-sensitive adhesive layer by mixing an ultraviolet-curable compound into the pressure-sensitive adhesive composition and then irradiating ultraviolet rays to cure the pressure-sensitive adhesive layer 1.

The thickness of the 1 st adhesive layer is preferably 3 μm or more, more preferably 5 μm or more. The thickness of the 1 st adhesive layer is preferably 40 μm or less, and more preferably 30 μm or less. The upper limit value and the lower limit value may be arbitrarily combined.

When the thickness of the 1 st pressure-sensitive adhesive layer is not less than the lower limit value, the polarizing plate and the retardation layer can be sufficiently bonded. When the thickness of the 1 st pressure-sensitive adhesive layer is equal to or less than the upper limit value, the retardation layer is less likely to be displaced, and the effect of suppressing the occurrence of wrinkles in the polarizing plate due to deformation of the retardation layer is enhanced.

In the production of the laminate of the present embodiment, when the polarizing plate and the retardation layer are bonded via the 1 st pressure-sensitive adhesive under a strong pressure, the thickness of the 1 st pressure-sensitive adhesive layer may be reduced as compared with the case of bonding under a weak pressure. This is because the 1 st adhesive layer has elasticity, but if left for a while after the polarizing plate and the phase difference layer are bonded, the thickness of the 1 st adhesive layer returns to its original value. Therefore, when the polarizing plate and the retardation layer are bonded with a strong pressure via the 1 st adhesive, a certain value can be obtained by measuring the thickness of the 1 st adhesive layer after leaving for 5 minutes, for example.

The storage elastic modulus of the 1 st adhesive layer is preferably 20,000Pa or more, more preferably 25,000Pa or more, and further preferably 50,000Pa or more. Further, the storage elastic modulus of the 1 st adhesive layer is preferably 150,000Pa or less. The upper limit value and the lower limit value may be arbitrarily combined.

The "storage elastic modulus" is an index showing the hardness of the adhesive layer. When the storage elastic modulus of the 1 st adhesive layer is not less than the lower limit value, the 1 st adhesive layer has sufficient hardness, and therefore, the polarizer and the retardation layer are less likely to be misaligned with each other, and the effect of suppressing the occurrence of wrinkles in the polarizing plate due to deformation of the retardation layer is improved. When the storage elastic modulus of the 1 st adhesive layer is not more than the upper limit value, bubbles are less likely to be generated between the adhesive layer and the retardation layer when the adhesive layer and the retardation layer are bonded, deformation of the retardation layer due to generation of bubbles is suppressed, and the effect of suppressing generation of wrinkles of the polarizing plate is improved.

In the present specification, the "storage elastic modulus of the 1 st adhesive layer" can be measured by a commercially available viscoelasticity measuring apparatus. As the viscoelasticity measuring apparatus, for example, MCR300 manufactured by Physica corporation can be used as shown in examples described later. "storage elastic modulus of the 1 st adhesive layer" is a value measured at 25 ℃ in accordance with JIS K7244-6.

The storage elastic modulus of the 1 st adhesive layer was set to E₁(Pa), the thickness of the 1 st adhesive layer is T₁At (. mu.m), Log (E)₁/T₁) Usually 3.1 or more, preferably 3.3 or more, more preferably 3.5 or more, and further preferably 3.8 or more. Furthermore, the above Log (E)₁/T₁) Preferably 5.0 or less. The upper limit value and the lower limit value may be arbitrarily combined.

When the above Log (E)₁/T₁) When the thickness is not less than the lower limit, the thickness of the 1 st pressure-sensitive adhesive layer and the storage elastic modulus are balanced, and the polarizing plate are usedThe retardation layer is firmly attached. Therefore, the effect of suppressing the occurrence of wrinkles in the polarizing plate due to the deformation of the retardation layer is improved.

When the above Log (E)₁/T₁) When the pressure-sensitive adhesive layer is not more than the upper limit, bubbles are less likely to be generated between the pressure-sensitive adhesive layer and the retardation layer when the pressure-sensitive adhesive layer and the retardation layer are bonded to each other, and the effect of suppressing the occurrence of wrinkles in the polarizing plate is improved by suppressing the deformation of the retardation layer due to the generation of bubbles.

< 2 nd adhesive layer >

The 2 nd adhesive layer is laminated on the surface of the retardation layer opposite to the surface contacting the 1 st adhesive layer. The polarizing plate is laminated on, for example, a display panel or the like via the 2 nd adhesive layer.

As the adhesive constituting the 2 nd adhesive layer used for laminating the retardation layer and, for example, the display panel, a conventionally known adhesive having excellent optical transparency can be used without particular limitation. As the adhesive constituting the 2 nd adhesive layer, the same adhesive as the adhesive exemplified as the adhesive constituting the 1 st adhesive layer can be used. The storage elastic modulus and the thickness of the 1 st adhesive layer and the 2 nd adhesive layer may be the same or different.

In addition, an active energy ray-curable adhesive may be used as the adhesive of the 2 nd adhesive layer. The "active energy ray-curable adhesive" has a property of being cured by irradiation with an energy ray such as ultraviolet ray or electron beam. The active energy ray-curable adhesive is an adhesive having the following properties: since it has adhesiveness before irradiation with an energy ray, it can be adhered to an adherend such as a film, and the adhesive force can be adjusted by curing by irradiation with an active energy ray. In the present embodiment, the adhesive used for the 2 nd adhesive layer is preferably an active energy ray-curable adhesive, and particularly preferably an ultraviolet-curable adhesive.

The active energy ray-curable adhesive generally contains an acrylic adhesive and an active energy ray-polymerizable compound as main components. Usually, a crosslinking agent is further compounded, and if necessary, a photopolymerization initiator, a photosensitizer and the like may be compounded.

When the phase difference layer is bonded to, for example, a display panel using an active energy ray-curable adhesive, the phase difference layer is first laminated on the display panel via the active energy ray-curable adhesive. Next, the pressure-sensitive adhesive layer containing the active energy ray-curable pressure-sensitive adhesive is cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. Ultraviolet rays are preferable as the active energy rays, and as the light source in this case, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, a metal halide lamp, or the like can be used.

The thickness of the 2 nd adhesive layer is preferably 3 μm or more, and more preferably 5 μm or more. The thickness of the 2 nd adhesive layer is preferably 40 μm or less, and more preferably 30 μm or less. The upper limit value and the lower limit value may be arbitrarily combined.

When the thickness of the 2 nd pressure-sensitive adhesive layer is equal to or more than the above lower limit value, the retardation layer can be sufficiently bonded to, for example, a display panel or the like. When the thickness of the 2 nd adhesive layer is equal to or less than the upper limit value, the retardation layer laminated through the 2 nd adhesive layer is less likely to be displaced from, for example, a display panel. Therefore, the retardation layer can be firmly fixed, and the polarizing plate and the retardation layer are less likely to be misaligned. As a result, the effect of suppressing the occurrence of wrinkles of the polarizing plate accompanying the deformation of the retardation layer is improved.

In the case where the phase difference layer is bonded to, for example, a display panel via the 2 nd adhesive under a strong pressure in the production of the laminate of the present embodiment, the thickness of the 2 nd adhesive layer may be reduced as compared with the case where the phase difference layer is bonded under a weak pressure. This is because the 2 nd adhesive layer has elasticity, but if left for a while after the phase difference layer is bonded to, for example, a display panel or the like, the thickness of the 2 nd adhesive layer returns to its original value. Therefore, when the phase difference layer is bonded to, for example, a display panel or the like via the 2 nd adhesive with a strong pressure, a certain value can be obtained by measuring the thickness of the 2 nd adhesive layer after leaving for 5 minutes, for example.

The storage elastic modulus of the 2 nd adhesive layer is preferably 20,000Pa or more, more preferably 25,000Pa or more, and further preferably 50,000Pa or more. Further, the storage elastic modulus of the 2 nd adhesive layer is preferably 150,000Pa or less. The upper limit value and the lower limit value may be arbitrarily combined.

As described above, the storage elastic modulus is an index showing the hardness of the adhesive layer. When the thickness of the 2 nd adhesive layer is equal to or greater than the lower limit value, the 2 nd adhesive layer has sufficient hardness, and therefore, misalignment between the retardation layer and, for example, a display panel is less likely to occur, and the retardation layer can be firmly fixed, and as a result, the polarizer and the retardation layer become less likely to be misaligned, and the effect of suppressing the occurrence of wrinkles in the polarizing plate accompanying deformation of the retardation layer is enhanced. When the storage elastic modulus of the 2 nd pressure-sensitive adhesive layer is not more than the above upper limit, the adhesiveness to an adherend substrate and the impact resistance are improved. Specifically, when the pressure-sensitive adhesive layer and the retardation layer are bonded to each other, bubbles are less likely to be generated between the pressure-sensitive adhesive layer and the retardation layer, and the effect of suppressing the occurrence of wrinkles in the polarizing plate is improved by suppressing the deformation of the retardation layer due to the generation of bubbles. When the 2 nd adhesive is an active energy ray-curable adhesive, the storage elastic modulus can be measured after curing the 2 nd adhesive to a target hardness by irradiation with an energy ray.

In the present specification, the measurement of "storage elastic modulus of the 2 nd adhesive layer" may be performed in the same manner as the measurement of "storage elastic modulus of the 1 st adhesive layer" described above.

The storage elastic modulus of the 2 nd adhesive layer was set to E₂(Pa) and the thickness of the 2 nd adhesive layer is T₂At (. mu.m), Log (E)₂/T₂) Preferably 3.0 or more, more preferably 3.3 or more, and further preferably 3.5 or more. Furthermore, the above Log (E)₂/T₂) Usually 7.0 or less, preferably 5.0 or less. The upper limit value and the lower limit value may be arbitrarily combined.

When the above Log (E)₂/T₂) When the thickness is not less than the lower limit, the thickness and the storage elastic modulus of the 2 nd adhesive layer can be made flatThe retardation layer is less likely to be displaced from, for example, a display panel, and can be firmly fixed. Therefore, the polarizer and the retardation layer are less likely to be misaligned, and the effect of suppressing the occurrence of wrinkles in the polarizing plate due to deformation of the retardation layer is improved.

When the above Log (E)₂/T₂) When the pressure-sensitive adhesive layer is not more than the upper limit, bubbles are less likely to be generated between the pressure-sensitive adhesive layer and the retardation layer when the pressure-sensitive adhesive layer and the retardation layer are bonded to each other, and the effect of suppressing the occurrence of wrinkles in the polarizing plate is improved by suppressing the deformation of the retardation layer due to the generation of bubbles.

In the present embodiment, Log (E)₁/T₁)+Log(E₂/T₂) The value of (b) is 6.4 or more, preferably 6.8 or more, and more preferably 7.0 or more.

When Log (E)₁/T₁)+Log(E₂/T₂) When the value of (d) is equal to or greater than the lower limit value, the polarizing plate and the retardation layer, and the retardation layer and, for example, the display panel can be firmly bonded to each other, and as a result, the effect of suppressing the occurrence of wrinkles in the polarizing plate due to deformation of the retardation layer is improved.

Furthermore, Log (E)₁/T₁)+Log(E₂/T₂) Preferably 9.0 or less, and may be 8.0 or less.

When Log (E)₁/T₁)+Log(E₂/T₂) When the value of (b) is within the above range, bubbles are less likely to be generated between the pressure-sensitive adhesive layer and the retardation layer when the pressure-sensitive adhesive layer and the retardation layer are bonded to each other, and the effect of suppressing the generation of wrinkles in the polarizing plate is improved by suppressing the deformation of the retardation layer due to the generation of bubbles.

The above upper and lower limits may be arbitrarily combined.

In the present embodiment, it is preferable to satisfy either of the following (1) and (2), and more preferably, it satisfies either of the following (1-1) and (2-1). Further preferably, both (1) and (2) below are satisfied, and more preferably both (1-1) and (2-1) below are satisfied.

(1)Log(E₁/T₁) Is 3.1 or more.

(2)Log(E₂/T₂) Is 3.0 or more.

(1-1)Log(E₁/T₁) Is 3.8 or more.

(2-1)Log(E₂/T₂) Is 3.5 or more.

The water vapor permeability of the 1 st adhesive layer and the 2 nd adhesive layer at a temperature of 40 ℃ and a humidity of 90% is preferably 1,000 to 10,000g/m²24h, can also be 2,000 to 9,000g/m²24 h. The water vapor permeability can be measured by a Lyssy water vapor permeameter L80 series manufactured by Systech ILLINOIS. When the water vapor permeability of the pressure-sensitive adhesive layer is high, the pressure-sensitive adhesive is strongly affected by a high-temperature and high-humidity environment, and thus wrinkles of the polarizing plate are likely to occur due to deformation of the phase difference layer. When it is difficult to measure the water vapor permeability with the adhesive alone, the water vapor permeability can be calculated from the ratio to the substrate having high moisture permeability by bonding the adhesive to the substrate having high moisture permeability.

< retardation layer >

The retardation layer 14 has a layer composed of a liquid crystal material (also referred to as a liquid crystal composition) containing a liquid crystal compound. Specifically, the layer made of a liquid crystal material containing a liquid crystal compound refers to a layer obtained by curing a liquid crystal compound. In the present specification, a layer to which a retardation of λ/2 is given, a layer to which a retardation of λ/4 is given, a positive C layer, and the like may be collectively referred to as a retardation layer. The retardation layer may further include a transparent substrate and an alignment layer, which will be described later.

The layer obtained by curing the liquid crystal compound is formed on, for example, an alignment layer provided on a transparent substrate. The "transparent substrate" refers to a substrate having transparency to the extent that light, particularly visible light, can be transmitted. In the present specification, "transparency" refers to a property of having a transmittance of 80% or more with respect to light in a visible light region having a wavelength of 380 to 780 nm.

The transparent substrate may be a substrate formed in a long strip shape and having a function of supporting the alignment layer. The transparent substrate can function as a releasable support for supporting a phase difference layer for transfer. Further, the surface preferably has a sufficient adhesive force to enable peeling.

Examples of the transparent substrate include a glass substrate and a plastic substrate, and a plastic substrate is preferable. Examples of the plastic constituting the plastic substrate include polyolefins such as polyethylene, polypropylene, and norbornene polymers, and cycloolefin resins; polyvinyl alcohol; polyethylene terephthalate; polymethacrylates; a polyacrylate; cellulose esters such as triacetyl cellulose, diacetyl cellulose, and cellulose acetate propionate; polyethylene naphthalate; a polycarbonate; polysulfones; polyether sulfone; a polyether ketone; polyphenylene sulfide and polyphenylene oxide. Among them, cellulose esters, cycloolefin resins, polyethylene terephthalate, and polymethacrylates are particularly preferable from the viewpoint of being easily available on the market and having excellent transparency. The transparent substrate may be a single layer containing these materials, or a laminate of 2 or more kinds of these materials may be formed. In the case of forming a multilayer body, layers having the same composition may be stacked.

The thickness of the transparent substrate is not particularly limited, and is preferably in the range of, for example, 20 μm or more and 200 μm or less. When the thickness of the transparent substrate is 20 μm or more, strength can be imparted. On the other hand, when the thickness is 200 μm or less, increase of processing chips and abrasion of the cutting blade can be suppressed when the transparent base material is cut into a single transparent base material.

The transparent substrate may be subjected to various anti-blocking treatments. The anti-blocking treatment includes an easy adhesion treatment, a treatment of kneading a filler or the like, and an embossing (knurling treatment). By applying such an anti-blocking treatment to the transparent substrate, sticking, i.e., blocking, of the substrates to each other when the transparent substrate is rolled up can be effectively prevented, and the optical film can be produced with high productivity.

The layer obtained by curing the liquid crystal compound is formed on the transparent substrate via the alignment layer. That is, the retardation layer is formed by laminating a transparent substrate and an alignment layer in this order, and a layer obtained by curing a liquid crystal compound is laminated on the alignment layer.

The alignment layer is not limited to a vertical alignment layer, and may be an alignment layer in which the molecular axis of the liquid crystal compound is aligned horizontally, or an alignment layer in which the molecular axis of the liquid crystal compound is aligned obliquely. The alignment film preferably has solvent resistance that is not dissolved by application of a coating liquid containing a liquid crystal compound described later and heat resistance to heat treatment for removing the solvent and aligning the liquid crystal compound. Examples of the alignment film include an alignment film containing an alignment polymer, a photo-alignment film, and a groove alignment film in which a concave-convex pattern and a plurality of grooves are formed on the surface to perform alignment. The thickness of the alignment film is usually in the range of 10nm to 10000nm, preferably 10nm to 1000nm, more preferably 500nm or less, and still more preferably 10nm to 200 nm.

The resin used for the alignment layer is not particularly limited as long as it is a resin used as a material of a known alignment film, and a cured product obtained by curing a conventionally known monofunctional or polyfunctional (meth) acrylate monomer with a polymerization initiator can be used. Specifically, examples of the (meth) acrylate monomer include 2-ethylhexyl acrylate, cyclohexyl acrylate, diethylene glycol mono-2-ethylhexyl ether acrylate, diethylene glycol monophenyl ether acrylate, tetraethylene glycol monophenyl ether acrylate, trimethylolpropane triacrylate, lauryl acrylate, lauryl methacrylate, isobornyl acrylate, isobornyl methacrylate, 2-phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, 2-hydroxypropyl acrylate, benzyl acrylate, tetrahydrofurfuryl methacrylate, 2-hydroxyethyl methacrylate, benzyl methacrylate, cyclohexyl methacrylate, methacrylic acid, and urethane acrylate. The resin used for the alignment layer may be a cured product obtained by curing 1 of these, or a cured product obtained by curing a mixture of 2 or more types.

The type of the liquid crystal compound used in this embodiment is not limited. Depending on the shape, they can be classified into rod-like types (rod-like liquid crystal compounds) and discotic types (discotic liquid crystal compounds ). Further, there are a low molecular type and a high molecular type, respectively. The polymer generally refers to a polymer having a polymerization degree of 100 or more (polymer physical/phase transition kinetics, native well, 2 p., rock book store, 1992).

In this embodiment, any liquid crystal compound can be used. It is possible to use 2 or more rod-like liquid crystal compounds, 2 or more discotic liquid crystal compounds, or a mixture of a rod-like liquid crystal compound and a discotic liquid crystal compound.

As the rod-like liquid crystal compound, liquid crystal compounds described in claim 1 of Japanese patent application laid-open No. 11-513019, paragraphs [0026] to [0098] of Japanese patent laid-open No. 2005-289980, and the like can be suitably used. As the discotic liquid crystal compound, liquid crystal compounds described in paragraphs [0020] to [0067] of Japanese patent laid-open No. 2007-108732, and paragraphs [0013] to [0108] of Japanese patent laid-open No. 2010-244038 can be suitably used.

The layer obtained by curing the liquid crystal compound is more preferably formed using a rod-like liquid crystal compound having a polymerizable group or a discotic liquid crystal compound having a polymerizable group. This makes it possible to reduce temperature and humidity changes in the optical characteristics.

The liquid crystal compound may be used in combination of 2 or more. In this case, it is preferable that at least 1 species has 2 or more polymerizable groups in the molecule. That is, the layer obtained by curing the liquid crystal compound is preferably a layer formed by fixing the liquid crystal compound by polymerization of a rod-like liquid crystal compound having a polymerizable group or a discotic liquid crystal compound having a polymerizable group. In this case, after the layer is formed, it is no longer necessary to exhibit liquid crystallinity.

When the rod-like liquid crystal compound or the discotic liquid crystal compound has a polymerizable group, the type of the polymerizable group is not particularly limited. The polymerizable group is preferably a functional group capable of undergoing an addition polymerization reaction, such as a polymerizable ethylenically unsaturated group or a cyclopolymerizable group. More specifically, examples of the polymerizable group include a (meth) acryloyl group, a vinyl group, a styryl group, and an allyl group. Among them, (meth) acryloyl groups are preferable. Note that the (meth) acryloyl group is a concept including both a methacryloyl group and an acryloyl group.

As described later, the layer obtained by curing the liquid crystal compound can be formed by applying a coating liquid containing the liquid crystal compound to, for example, an alignment layer. The coating liquid may contain components other than the liquid crystal compound. For example, the coating liquid may contain a polymerization initiator. As the polymerization initiator to be used, for example, a thermal polymerization initiator, a photopolymerization initiator can be selected depending on the form of the polymerization reaction. Examples of the photopolymerization initiator include α -carbonyl compounds, acyloin ethers, α -hydrocarbyl-substituted aromatic acyloin compounds, polynuclear quinone compounds, combinations of triarylimidazole dimers and p-aminophenyl ketones, and the like. The amount of the polymerization initiator to be used is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on the total solid content in the coating liquid.

The coating liquid may contain a polymerizable monomer from the viewpoint of uniformity of the coating film and strength of the film. Examples of the polymerizable monomer include a radically polymerizable or cationically polymerizable compound. Among them, polyfunctional radical polymerizable monomers are preferable.

As the polymerizable monomer, a polymerizable monomer copolymerizable with the liquid crystal compound having a polymerizable group (hereinafter, also referred to as a polymerizable liquid crystal compound) is preferable. Specific examples of the polymerizable monomer include polymerizable monomers described in paragraphs [0018] to [0020] in Japanese patent laid-open publication No. 2002-296423. The amount of the polymerizable monomer is preferably 1 to 50% by mass, more preferably 2 to 30% by mass, based on the total mass of the liquid crystal compound.

The coating liquid may contain a surfactant from the viewpoint of uniformity of the coating film and strength of the film. Examples of the surfactant include conventionally known compounds. Among them, fluorine compounds are particularly preferable. Specific examples of the surfactant include compounds described in paragraphs [0028] to [0056] in Japanese patent application laid-open No. 2001-330725 and compounds described in paragraphs [0069] to [0126] in Japanese patent application laid-open No. 2003-295212.

The coating liquid may contain a solvent, and an organic solvent is preferably used. Examples of the organic solvent include amides (e.g., N-dimethylformamide), sulfoxides (e.g., dimethyl sulfoxide), heterocyclic compounds (e.g., pyridine), hydrocarbons (e.g., benzene and hexane), alkyl halides (e.g., chloroform and dichloromethane), esters (e.g., methyl acetate, ethyl acetate and butyl acetate), ketones (e.g., acetone and methyl ethyl ketone), and ethers (e.g., tetrahydrofuran and 1, 2-dimethoxyethane). Among them, alkyl halides and ketones are preferable. The coating liquid may be used in combination with 2 or more kinds of organic solvents.

The coating liquid may contain a vertical alignment promoter such as a polarizing plate interface side vertical alignment agent or an air interface side vertical alignment agent; and various alignment agents such as a horizontal alignment promoter such as a horizontal alignment agent on the polarizing plate interface side and a horizontal alignment agent on the air interface side. The coating liquid may contain an adhesion improving agent, a plasticizer, a polymer, and the like in addition to the above components.

The thickness of the retardation layer in this embodiment is preferably 0.5 μm or more. The thickness of the retardation layer is preferably 10 μm or less, and more preferably 5 μm or less. The upper limit value and the lower limit value may be arbitrarily combined.

When the thickness of the retardation layer is not less than the lower limit, sufficient durability can be obtained. When the thickness of the retardation layer is not more than the above upper limit value, it can contribute to thinning of the polarizing plate.

The thickness of the retardation layer can be adjusted so that the in-plane retardation value and the thickness-direction retardation value required for the layer giving a retardation of λ/4, the layer giving a retardation of λ/2, or the positive C layer can be obtained.

In the present embodiment, the puncture strength of the retardation layer is not particularly limited. When a retardation layer having a weak puncture strength is used, wrinkles are likely to occur in the polarizing plate in a high-temperature and high-humidity environment. According to the present embodiment, the occurrence of wrinkles can be suppressed even in a polarizing plate including a retardation layer having a weak puncture strength.

In the present invention, when the polarizing plate includes a laminate including a plurality of retardation layers, the puncture strength of the laminate is used as the puncture strength of the retardation layers. When the laminate includes an adhesive layer and an alignment layer for bonding the retardation layers to each other, the puncture strength of the laminate including these layers is used.

The puncture strength of the retardation layer may be 100gf or less, 95gf or less, 90gf or less, or 80gf or less. The puncture strength of the retardation layer may be 10gf or more, 30gf or more, or 50gf or more.

When the retardation layer included in the polarizing plate is 1 layer, such a retardation layer having a puncture strength can be obtained by, for example, reducing the thickness of the layer constituting the retardation layer.

When the retardation layer included in the polarizing plate is a laminate of a plurality of retardation layers, the retardation layer having such a puncture strength can be obtained by, for example, the type and thickness of the adhesive and the thickness of the retardation layer.

The puncture strength is a strength at which the phase difference layer is vertically punctured by the puncture jig and the phase difference layer is cracked. The puncture strength can be measured by a compression tester equipped with a load cell, for example. Examples of the compression tester include a portable compression tester "KES-G5" manufactured by KATO TECH corporation and a small bench tester "EZ Test (registered trademark)" manufactured by shimadzu corporation.

The phase difference layer was sandwiched between 2 sample stages each having a circular hole having a diameter of 15mm or less through which a puncture jig can pass. The puncture jig is a cylindrical rod and includes a puncture needle, and the tip of the puncture needle that is in contact with the phase difference layer is spherical or hemispherical. The diameter of the spherical or hemispherical portion of the tip is 1mm phi. Further, the curvature thereof was 0.5R. The puncture speed of the compression tester was 0.0033 cm/sec. The puncture strength of the test piece of 12 retardation layers was measured, and the average value thereof was determined as the puncture strength.

The moisture permeability ratio of the retardation layer at 40 ℃ and 90% RH is preferably in the range of 0.5 to 1.0. The moisture permeability ratio is a value calculated by the following method. Since the retardation layer alone has a low thickness and low mechanical properties, it is difficult to measure the moisture permeability. Therefore, the retardation layer was bonded to a substrate having high moisture permeability with an adhesive, and the moisture permeability was measured. The moisture permeability can be measured by the same method as that for the moisture permeability of the protective film. The moisture permeability ratio is calculated from the ratio of the measured moisture permeability to the moisture permeability of the substrate.

The lower the moisture permeability ratio, the more effective the suppression of wrinkles in a high-temperature and high-humidity environment.

In the present specification, "the total thickness of the polarizing plate" refers to the dimension in the lamination direction of the polarizing plate. That is, the "total thickness of the polarizing plate of embodiment 1" refers to the total thickness of the polarizer, the thickness of the 1 st adhesive layer, the thickness of the retardation layer, the thickness of the 2 nd adhesive layer, and the thickness of all the optical film layers, the adhesive layers, and the adhesive layers included in the polarizing plate. The components that do not ultimately remain in the display device are not included in the total thickness of the polarizing plate. Examples of the member that does not remain in the display device at the end include a surface protective film laminated on the surface of the polarizing plate opposite to the display panel, and a separator laminated on the 2 nd adhesive layer. These layers are peeled off during the manufacturing process of the display device and do not finally remain in the display device.

The total thickness of the polarizing plate can be obtained by measuring the thickness at any 5 points of the polarizing plate with a micrometer, for example, and calculating the average value.

The total thickness of the polarizing plate may be obtained by measuring the thickness of the polarizer, the thickness of the 1 st adhesive layer, the thickness of the retardation layer, the thickness of the 2 nd adhesive layer, and the thicknesses of all the optical film layers, adhesive layers, and adhesive layers included in the polarizing plate, respectively, and summing the values.

The thickness of the polarizer, the thickness of the 1 st adhesive layer, the thickness of the retardation layer, the thickness of the 2 nd adhesive layer, and the thicknesses of all the optical film layers, adhesive layers, and adhesive layers included in the polarizing plate can be measured by the methods described in the present specification.

The total thickness of the polarizing plate in embodiment 1 is preferably 30 μm or more. The total thickness of the polarizing plate is preferably 500 μm or less, more preferably 300 μm or less, and still more preferably 100 μm or less. The upper limit value and the lower limit value may be arbitrarily combined.

When the total thickness of the polarizing plate is not more than the above upper limit value, it may contribute to thinning of the polarizing plate. When the total thickness of the polarizing plate is not less than the lower limit value, the strength of the polarizing plate is improved.

[2 nd embodiment ]

The polarizing plate of embodiment 2 includes at least 2 retardation layers. The number of retardation layers included in the polarizing plate of embodiment 2 is not particularly limited, and examples thereof include 2 layers and 3 layers.

The polarizing plate according to embodiment 2 including 2 retardation layers is a polarizing plate including a polarizer, a 1 st adhesive layer, a 1 st retardation layer, a 1 st adhesive layer, a 2 nd retardation layer, and a 2 nd adhesive layer in this order.

Fig. 2 is a schematic cross-sectional view showing a structure of a polarizing plate according to embodiment 2 including 2 retardation layers. As shown in fig. 2, the polarizing plate 101 includes a polarizer 11, a 1 st adhesive layer 12, a 1 st retardation layer 15, a 1 st adhesive layer 17, a 2 nd retardation layer 16, and a 2 nd adhesive layer 13 stacked in this order.

The polarizing plate according to embodiment 2 including 3 retardation layers is a polarizing plate including a polarizer, a 1 st adhesive layer, a 1 st retardation layer, a 1 st adhesive layer, a 2 nd retardation layer, a 2 nd adhesive layer, a 3 rd retardation layer, and a 2 nd adhesive layer in this order.

Fig. 3 is a schematic cross-sectional view showing a structure of a polarizing plate according to embodiment 2 including 3 retardation layers. As shown in fig. 3, a polarizing plate 102 includes a polarizer 11, a 1 st adhesive layer 12, a 1 st retardation layer 15, a 1 st adhesive layer 17, a 2 nd retardation layer 16, a 2 nd adhesive layer 18, a 3 rd retardation layer 19, and a 2 nd adhesive layer 13 stacked in this order.

The same reference numerals are attached to the constituent elements (the polarizing plate 11, the 1 st adhesive layer 12, and the 2 nd adhesive layer 13) in the same manner as in embodiment 1, and the description thereof is omitted.

< laminate comprising multiple retardation layers >

When the polarizing plate includes 2 retardation layers, the 1 st retardation layer 15 and the 2 nd retardation layer 16 are laminated via the 1 st adhesive layer 17.

When the polarizing plate includes 3 retardation layers, the 1 st retardation layer 15 and the 2 nd retardation layer 16 are laminated via the 1 st adhesive layer 17, and the 2 nd retardation layer 16 and the 3 rd retardation layer 19 are laminated via the 2 nd adhesive layer 18.

The 1 st retardation layer 15, the 2 nd retardation layer 16, and the 3 rd retardation layer 19 are retardation layers, and each may be, for example, a layer giving a retardation of λ/2, a layer giving a retardation of λ/4, or a positive C layer.

In the case where the polarizing plate includes 2 retardation layers as in 1 mode of the present embodiment, it is preferable that either one of the 1 st retardation layer 15 and the 2 nd retardation layer 16 functions as a layer for imparting a retardation of λ/4 and the other functions as a layer for imparting a retardation of λ/2; alternatively, one of the 1 st retardation layer 15 and the 2 nd retardation layer 16 functions as a layer for imparting a retardation of λ/4, and the other functions as a positive C layer.

When the polarizing plate includes 3 retardation layers, it is preferable that any one of the 1 st retardation layer 15, the 2 nd retardation layer 16, and the 3 rd retardation layer 19 functions as a layer for imparting a retardation of λ/4, and the other two layers function as a positive C layer.

The thicknesses and constituent materials of the 1 st retardation layer 15, the 2 nd retardation layer 16, and the 3 rd retardation layer 19 can be adjusted so as to obtain the in-plane retardation value and the thickness direction retardation value necessary for the layer giving a retardation of λ/4, the layer giving a retardation of λ/2, or the positive C layer.

In the polarizing plate including 2 retardation layers, when the 1 st retardation layer 15 functions as a layer for imparting a retardation of λ/2 and the 2 nd retardation layer 16 functions as a layer for imparting a retardation of λ/4, the thickness of the 1 st retardation layer 15 is, for example, 1 μm or more and 10 μm or less, and the thickness of the 2 nd retardation layer 16 is, for example, 1 μm or more and 10 μm or less. In the polarizing plate including 2 retardation layers, when the 1 st retardation layer 15 functions as a layer for imparting a retardation of λ/4 and the 2 nd retardation layer 16 functions as a positive C layer, the thickness of the 1 st retardation layer 15 is, for example, 1 μm or more and 10 μm or less, and the thickness of the 2 nd retardation layer 16 is, for example, 1 μm or more and 10 μm or less.

The transparent substrate, alignment layer, and liquid crystal compound of each of the 1 st retardation layer, the 2 nd retardation layer, and the 3 rd retardation layer can be the same as those exemplified in embodiment 1. The composition of the 1 st retardation layer, the 2 nd retardation layer and the 3 rd retardation layer may be the same or different. The thicknesses of the 1 st retardation layer, the 2 nd retardation layer, and the 3 rd retardation layer can be obtained by the method for measuring the thickness of the layer described in embodiment 1.

The 1 st retardation layer, the 2 nd retardation layer, and the 3 rd retardation layer each have the same configuration as the retardation layer of embodiment 1, and a transparent substrate, an alignment layer, and a retardation layer are sequentially stacked. The transparent substrate and the alignment layer may be peeled off.

When the polarizing plate includes 2 retardation layers, the 1 st retardation layer and the 2 nd retardation layer are laminated via the 1 st adhesive layer. That is, the laminate including 2 retardation layers may be a laminate in which a 1 st retardation layer, a 1 st adhesive layer, and a 2 nd retardation layer are sequentially laminated.

When the polarizing plate includes 3 retardation layers, for example, the 1 st retardation layer and the 2 nd retardation layer are laminated via the 1 st adhesive layer, and the 2 nd retardation layer and the 3 rd retardation layer are laminated via the 2 nd adhesive layer. That is, the laminate including 3 retardation layers may be a laminate in which a 1 st retardation layer, a 1 st adhesive layer, a 2 nd retardation layer, a 2 nd adhesive layer, and a 3 rd retardation layer are sequentially laminated.

In the present specification, the "adhesive layer" refers to an adhesive layer or an adhesive layer. As the pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer described above can be suitably used. In the present embodiment, an adhesive layer is preferably used as the adhesive layer from the viewpoint of preventing generation of wrinkles. The "adhesive agent" constituting the adhesive layer is a substance which can be applied to a substrate in a liquid state when applied to the substrate and exhibits adhesiveness by curing (i.e., exhibits no adhesiveness until curing).

< adhesive layer >

Examples of the adhesive for bonding the 1 st retardation layer and the 2 nd retardation layer, and the 2 nd retardation layer and the 3 rd retardation layer include an aqueous adhesive and an active energy ray-curable adhesive. Examples of the aqueous adhesive include an adhesive in which a polyvinyl alcohol resin is dissolved or dispersed in water. Examples of the active energy ray-curable adhesive include adhesives containing a curable compound that is cured by irradiation with an active energy ray such as ultraviolet light, visible light, electron beam, or X-ray. In many cases, the storage elastic modulus of the cured active energy ray-curable adhesive is higher than that of the aqueous adhesive. When the storage elastic modulus of the adhesive layer between the retardation layers is high, the misalignment between the retardation layers is less likely to occur, and therefore, an active energy ray-curable adhesive is preferably used.

As the active energy ray-curable adhesive, one or both of a cationically polymerizable curable compound and a radically polymerizable curable compound is preferably used in order to exhibit good adhesiveness. The active energy ray-curable adhesive may further contain either or both of a cationic polymerization initiator and a radical polymerization initiator for initiating a curing reaction of the curable compound.

Examples of the cationically polymerizable curable compound include an epoxy compound (a compound having 1 or 2 or more epoxy groups in a molecule), an oxetane compound (a compound having 1 or 2 or more oxetane rings in a molecule), and a combination thereof.

Examples of the radically polymerizable curable compound include a (meth) acrylic compound (a compound having 1 or 2 or more (meth) acryloyloxy groups in the molecule), another vinyl compound having a radically polymerizable double bond, and a combination thereof.

The active energy ray-curable adhesive may contain additives such as a cationic polymerization accelerator, an ion scavenger, an antioxidant, a chain transfer agent, a thickener, a thermoplastic resin, a filler, a flow control agent, a plasticizer, an antifoaming agent, an antistatic agent, a leveling agent, and a solvent, if necessary.

When the 1 st retardation layer and the 2 nd retardation layer, and the 2 nd retardation layer and the 3 rd retardation layer are bonded to each other with an adhesive, the adhesive is first applied to the bonding surface of either one of the 1 st retardation layer and the 2 nd retardation layer or the bonding surface of both, and the bonding surface of either one of the 2 nd retardation layer and the 3 rd retardation layer or the bonding surface of both.

As a method for applying the adhesive to the joint surface, a general coating technique using a die coater, a comma coater, a reverse roll coater, a gravure coater, a bar coater, a wire bar coater, a knife coater, an air knife coater, or the like can be used.

The drying method in the case of using the water-based adhesive is not particularly limited, and for example, a method of drying using a hot air dryer or an infrared dryer can be employed.

When an active energy ray-curable adhesive is used, the active energy ray-curable adhesive is cured by irradiation with an active energy ray such as ultraviolet ray, visible light, electron beam, or X-ray. Ultraviolet rays are preferable as the active energy rays, and as the light source in this case, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high-pressure mercury lamp, a chemical lamp, a black light lamp, a microwave-excited mercury lamp, a metal halide lamp, or the like can be used.

The thickness of the adhesive layer is preferably 10 μm or less, and more preferably 5 μm or less.

When the thickness of the adhesive layer is not more than the above upper limit, floating and peeling are less likely to occur between the 1 st retardation layer and the 2 nd retardation layer, and between the 2 nd retardation layer and the 3 rd retardation layer.

The "total thickness of the polarizing plate of embodiment 2" is a thickness obtained by adding the thickness of the polarizer, the thickness of the 1 st adhesive layer, the thickness of the 1 st retardation layer, the thickness of the 1 st adhesive layer, the thickness of the 2 nd retardation layer, the thickness of the 2 nd adhesive layer, and the thickness of all the optical film layers (the 3 rd retardation layer and the like), the adhesive layer, and the adhesive layer (the 2 nd adhesive layer and the like) included in the polarizing plate. As described above, the components that do not ultimately remain in the display device are not included in the total thickness of the polarizing plate.

The total thickness of the polarizing plate of the present embodiment can be obtained by, for example, measuring the thickness at arbitrary 5 points of the polarizing plate with a micrometer and calculating the average value of the measured values.

The total thickness of the polarizing plate may be obtained by measuring the thickness of the polarizer, the thickness of the 1 st pressure-sensitive adhesive layer, the thickness of the 1 st retardation layer, the thickness of the adhesive layer, the thickness of the 2 nd retardation layer, the thickness of the 2 nd pressure-sensitive adhesive layer, and the thicknesses of all the optical film layers, pressure-sensitive adhesive layers, and adhesive layers included in the polarizing plate, respectively, and adding the measured values to one another.

The thickness of the polarizer, the thickness of the 1 st adhesive layer, the thickness of the 1 st retardation layer, the thickness of the adhesive layer, the thickness of the 2 nd retardation layer, the thickness of the 2 nd adhesive layer, and the thicknesses of all the optical film layers, adhesive layers, and adhesive layers included in the polarizing plate can be measured by the methods described in the present specification.

The total thickness of the polarizing plate of embodiment 2 is preferably 500 μm or less, and more preferably 300 μm or less. The total thickness of the polarizing plate of embodiment 2 is preferably 30 μm or more.

Method for producing polarizing plate

An example of the method for producing the polarizing plate of the present invention will be described below.

[ method for producing polarizing plate ]

The polarizing plate is generally manufactured through the following processes: the method for producing a polyvinyl alcohol film includes a step of uniaxially stretching a PVA-based film, a step of dyeing the PVA-based film with a dichroic dye to adsorb the dichroic dye, a step of treating the PVA-based film adsorbed with the dichroic dye with an aqueous boric acid solution and crosslinking the same, and a step of washing the same with water after the crosslinking treatment with an aqueous boric acid solution (hereinafter, also referred to as boric acid treatment).

The uniaxial stretching of the PVA-based film may be performed before, simultaneously with, or after the dyeing with the dichroic dye. In the case where the uniaxial stretching is performed after dyeing, the uniaxial stretching may be performed before or during the boric acid treatment. Of course, uniaxial stretching may also be performed in multiple stages as shown here. The uniaxial stretching may be a method of performing uniaxial stretching in the film conveying direction between rollers having different peripheral speeds, a method of performing uniaxial stretching in the film conveying direction using a heat roller, a method of performing stretching in the width direction using a tenter, or the like. The uniaxial stretching may be performed by dry stretching in which stretching is performed in the air, or may be performed by wet stretching in which stretching is performed in a state where the PVA-based film is swollen with a solvent such as water. The draw ratio is usually about 3 to 8 times.

The dyeing of the PVA-based film with the dichroic dye can be performed, for example, by a method of immersing the PVA-based film in an aqueous solution containing the dichroic dye. As the dichroic dye, specifically, iodine or a dichroic organic dye can be used. The PVA-based film is preferably subjected to a treatment of swelling by immersing in water before dyeing.

When iodine is used as the dichroic dye, a method of immersing the PVA-based film in an aqueous solution containing iodine and potassium iodide to dye the film is generally employed. The content of iodine in the aqueous solution is usually about 0.01 to 1 part by mass per 100 parts by mass of water, and the content of potassium iodide is usually about 0.5 to 20 parts by mass per 100 parts by mass of water. The temperature of the aqueous solution used for dyeing is usually about 20 to 40 ℃. The immersion time (dyeing time) in the aqueous solution is usually about 20 to 1,800 seconds.

On the other hand, when a dichroic organic dye is used as the dichroic dye, a method of dyeing by immersing a PVA-based film in an aqueous solution containing a water-soluble dichroic organic dye is generally employed. The content of the dichroic organic dye in the aqueous solution is usually about 0.0001 to 10 parts by mass, preferably about 0.001 to 1 part by mass per 100 parts by mass of water. The aqueous dye solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant. The temperature of the dichroic organic dye aqueous solution used for dyeing is usually about 20 to 80 ℃. The immersion time (dyeing time) in the aqueous solution is usually about 10 to 1,800 seconds.

The boric acid treatment after dyeing with the dichroic dye can be performed by a method of immersing the dyed PVA-based film in an aqueous solution containing boric acid. The boric acid content of the aqueous solution containing boric acid is usually about 2 to 15 parts by mass, preferably 5 to 12 parts by mass, per 100 parts by mass of water. When iodine is used as the dichroic dye, the aqueous solution containing boric acid preferably contains potassium iodide. The content of potassium iodide in the aqueous solution containing boric acid is usually about 0.1 to 15 parts by mass, preferably 5 to 12 parts by mass, per 100 parts by mass of water. The immersion time in the aqueous solution containing boric acid is usually about 60 to 1,200 seconds, preferably 150 to 600 seconds, and more preferably 200 to 400 seconds. The temperature of the aqueous solution containing boric acid is usually 50 ℃ or higher, preferably 50 to 85 ℃, and more preferably 60 to 80 ℃.

The PVA film after the boric acid treatment is usually subjected to a water washing treatment. The water washing treatment can be performed by, for example, immersing the PVA-based film subjected to the boric acid treatment in water. The temperature of water in the water washing treatment is usually about 5 to 40 ℃. The dipping time is usually about 1 to 120 seconds.

After washing with water, drying treatment was performed to obtain a polarizing plate. The drying treatment may be performed using a hot air dryer or a far infrared heater. The temperature of the drying treatment is usually about 30 to 100 ℃, preferably 50 to 80 ℃. The drying time is usually about 60 to 600 seconds, preferably 120 to 600 seconds. The moisture content in the polarizing plate is reduced to a practical level by the drying treatment. The water content is usually about 5 to 20 mass%, preferably 8 to 15 mass%, based on the total mass of the polarizing plate. When the moisture content is 5 mass% or more, the polarizing plate has sufficient flexibility, and therefore, occurrence of damage or breakage after drying can be suppressed. Further, when the moisture percentage is 20 mass% or less, the polarizing plate has sufficient thermal stability.

As described above, a polarizing plate in which a dichroic dye is adsorbed and oriented in a PVA film can be manufactured.

In addition, the polarizing plate obtained in the above may further have a protective film bonded to one or both surfaces thereof via the adhesive.

[ methods for producing adhesive layer 1 and adhesive layer 2]

As described above, the 1 st adhesive layer and the 2 nd adhesive layer are preferably formed of an adhesive having an acrylic resin as a base polymer.

The (meth) acrylic resin (1) can be usually produced by a known polymerization method such as a solution polymerization method, a bulk polymerization method, a suspension polymerization method, or an emulsion polymerization method. In the production of the (meth) acrylic resin (1), polymerization is usually carried out in the presence of a polymerization initiator. The amount of the polymerization initiator used is usually 0.001 to 5 parts by mass based on 100 parts by mass of the total of all monomers constituting the (meth) acrylic resin (1). The (meth) acrylic resin (1) can also be produced by a method of polymerization using an active energy ray such as ultraviolet ray.

Examples of the polymerization initiator include thermal polymerization initiators and photopolymerization initiators. Examples of the photopolymerization initiator include 4- (2-hydroxyethoxy) phenyl (2-hydroxy-2-propyl) ketone. Examples of the thermal polymerization initiator include azo compounds such as 2, 2 ' -azobisisobutyronitrile, 2 ' -azobis (2-methylbutyronitrile), 1 ' -azobis (cyclohexane-1-carbonitrile), 2 ' -azobis (2, 4-dimethylvaleronitrile), 2 ' -azobis (2, 4-dimethyl-4-methoxyvaleronitrile), dimethyl 2, 2 ' -azobis (2-methylpropionate), and 2, 2 ' -azobis (2-hydroxymethylpropionitrile); organic peroxides such as lauryl peroxide, t-butyl hydroperoxide, benzoyl peroxide, t-butyl peroxybenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, dipropyl peroxydicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxypivalate, and (3, 5, 5-trimethylhexanoyl) peroxide; inorganic peroxides such as potassium persulfate, ammonium persulfate, and hydrogen peroxide. Further, a redox initiator using a peroxide and a reducing agent in combination can be used as the polymerization initiator.

The (meth) acrylic resin (1) is preferably produced by a solution polymerization method. Specifically, a desired monomer is mixed with an organic solvent, and a thermal polymerization initiator is added to the resulting solution under a nitrogen atmosphere. The resulting mixture is stirred at about 40 to 90 ℃, preferably about 60 to 80 ℃ for about 3 to 10 hours, whereby a (meth) acrylate polymer can be obtained. In order to control the polymerization reaction, the monomer, the thermal polymerization initiator, or both may be continuously or intermittently added to the reaction system during the polymerization reaction, or may be added in a state of being dissolved in an organic solvent. Examples of the organic solvent include aromatic hydrocarbon solvents such as toluene and xylene; ester solvents such as ethyl acetate and butyl acetate; aliphatic alcohol solvents such as propanol and isopropanol; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone.

The (meth) acrylic resin (1) thus obtained, the crosslinking agent (2), the silane compound (3), and, if necessary, an organic solvent may be mixed to obtain a coating solution of the adhesive composition. As the organic solvent, the same organic solvent as the solution used in the above-mentioned liquid phase polymerization can be used. The pressure-sensitive adhesive layer can be formed by applying the coating solution to an adherend and drying the coating solution. The adhesive layer may be formed on the separator by applying the coating solution to the separator and drying the coating solution.

As a method for applying the coating solution of the adhesive composition to an adherend or a separator, a general coating technique using a die coater, a comma wheel coater, a reverse roll coater, a gravure coater, a bar coater, a wire bar coater, a blade coater, an air blade coater, or the like can be used.

The separator is preferably composed of a plastic film and a release layer. Examples of the plastic film include polyester films such as polyethylene terephthalate films, polybutylene terephthalate films, and polyethylene naphthalate films; polyolefin films such as polypropylene films.

The release layer may be formed of, for example, a release layer-forming composition, and the main component (resin) constituting the release layer-forming composition is not particularly limited, and examples thereof include silicone resin, alkyd resin, acrylic resin, and long-chain alkyl resin.

The respective storage elastic moduli of the 1 st adhesive layer and the 2 nd adhesive layer may be adjusted by the kind of the adhesive composition.

The respective thicknesses of the 1 st adhesive layer and the 2 nd adhesive layer may be adjusted by the application conditions of the solution containing the adhesive composition. In order to make the thickness of the adhesive layer thin, it is effective to make the coating thickness small.

[ method for producing retardation layer ]

As described above, the retardation layer may have a layer obtained by curing a liquid crystal compound, and may further have a transparent substrate and an alignment layer.

The alignment layer is a layer containing the resin as described above, and is formed by applying a composition for an alignment layer containing a monomer for forming the resin to a transparent base material, drying the composition, and then performing a predetermined curing treatment. The alignment layer is composed of the cured product thus formed.

The solvent (diluting solvent) used in the composition for an alignment layer is not particularly limited as long as it can dissolve the alignment material to a desired concentration, and examples thereof include hydrocarbon solvents such as benzene and hexane; ketone solvents such as Methyl Ethyl Ketone (MEK), methyl isobutyl ketone (MIBK), and Cyclohexanone (CHN); ether solvents such as tetrahydrofuran, 1, 2-dimethoxyethane and propylene glycol monoethyl ether; halogenated alkyl solvents such as chloroform and methylene chloride; ester solvents such as methyl acetate, ethyl acetate, butyl acetate, and propylene glycol monomethyl ether acetate; amide solvents such as N, N-dimethylformamide; sulfoxide solvents such as dimethyl sulfoxide; a cyclohexanone-based solvent such as cyclohexane; alcohol solvents such as methanol, ethanol, and isopropanol. The solvent may be 1 kind or a mixed solvent of 2 or more kinds.

As a method for applying the composition for an alignment layer to a transparent substrate, a general coating technique using a die coater, a comma coater, a reverse roll coater, a gravure coater, a bar coater, a wire bar coater, a knife coater, an air knife coater, or the like can be used.

The layer obtained by curing the liquid crystal compound can be formed by applying a coating liquid containing a polymerizable liquid crystal compound to the alignment layer, drying the coating liquid, and then performing a predetermined curing treatment. The retardation layer is composed of the cured product thus formed.

The content of the polymerizable liquid crystal compound relative to the total mass of the coating liquid containing the polymerizable liquid crystal compound is not particularly limited, and may be in the range of 5 to 40 mass%. The content of the polymerizable liquid crystal compound can be adjusted when the viscosity or the like is to be adjusted according to the coating method of coating the alignment layer. The polymerizable liquid crystal compounds may be used alone in 1 kind or in combination of 2 or more kinds.

The coating liquid containing the polymerizable liquid crystal compound is usually dissolved in the solvent (diluting solvent) described above, and is preferably a solvent inactive to the polymerization reaction of the polymerizable liquid crystal compound.

As a method of applying the coating liquid containing the polymerizable liquid crystal compound, a known method such as a wire bar coating method, an extrusion coating method, a direct gravure coating method, a reverse gravure coating method, a die coating method, or the like can be used.

The retardation layer is obtained by polymerizing a polymerizable liquid crystal compound contained in a film formed on the alignment layer. The polymerization method can be selected according to the kind of the polymerizable group of the polymerizable liquid crystal compound. If the polymerizable group is a photopolymerizable group, polymerization can be carried out by a photopolymerization method. Further, if the polymerizable group is a thermopolymerizable group, polymerization can be carried out by a thermopolymerization method. Among the methods for producing the retardation layer according to the present embodiment, a photopolymerization method is preferable. The photopolymerization method does not necessarily require heating the transparent substrate to a high temperature, and therefore a transparent substrate having low heat resistance can be used. The photopolymerization method is performed by irradiating a film containing a liquid crystal composition containing a polymerizable liquid crystal compound with visible light or ultraviolet light. From the viewpoint of easy handling, ultraviolet rays are preferred.

[ method for producing a laminate comprising a plurality of retardation layers ]

A method for manufacturing a laminate including 2 retardation layers will be described as an example of a method for manufacturing a laminate including a plurality of retardation layers according to embodiment 2. The 1 st retardation layer and the 2 nd retardation layer are laminated via the 1 st adhesive layer.

When the 1 st retardation layer and the 2 nd retardation layer are laminated via the 1 st adhesive layer, the aqueous adhesive, or the active energy ray-curable adhesive described above is applied to either one or both of the 1 st retardation layer and the 2 nd retardation layer, and the 1 st retardation layer and the 2 nd retardation layer are bonded to each other.

When an aqueous adhesive is used, the adhesive may be cured by the above-described drying method to obtain a laminate including 2 retardation layers. On the other hand, when an active energy ray-curable adhesive is used, a laminate including a plurality of retardation layers can be obtained by irradiating the adhesive with an energy ray typified by ultraviolet rays.

The laminate including a plurality of retardation layers may be a laminate in which a transparent substrate, an alignment layer, a 1 st retardation layer, a 1 st adhesive layer, a 2 nd retardation layer, an alignment layer, and a transparent substrate are sequentially laminated. The transparent substrate and the alignment layer may be peeled off before the retardation layer is bonded to the polarizing plate.

In addition, a laminate including 3 retardation layers can be obtained by further laminating a 2 nd retardation layer and a 3 rd retardation layer via a 2 nd adhesive layer, in the same manner as in the case of laminating the 1 st retardation layer and the 2 nd retardation layer via a 1 st adhesive layer described above.

[ method for manufacturing polarizing plate according to embodiment 1]

An example of a method for manufacturing the polarizing plate 100 according to embodiment 1 in which the retardation layer is 1 layer will be described below. The polarizing plate, the adhesive layer, and the retardation layer used in the present embodiment may be the polarizing plate, the adhesive layer, and the retardation layer manufactured by the above-described methods.

As the adhesive, the adhesive composition described above or an adhesive layer formed on the separator may be used. The following description will be given, as an example, of a case where the adhesive formed on the separator is used as the 1 st adhesive layer and the 2 nd adhesive layer.

The polarizing plate 11 is laminated with the 1 st adhesive layer 12. Specifically, the polarizing plate 11 and the 1 st adhesive layer 12 can be laminated by bonding the surface of the 1 st adhesive layer 12 opposite to the surface on which the separator is laminated to one surface of the polarizing plate 11.

Next, the 1 st adhesive layer 12 and the retardation layer 14 are laminated.

The retardation layer 14 is bonded to the surface of the 1 st pressure-sensitive adhesive layer 12 from which the separator is peeled off and exposed, whereby the 1 st pressure-sensitive adhesive layer 12 and the retardation layer 14 can be laminated. The surface of the retardation layer 14 that contacts the 1 st pressure-sensitive adhesive layer 12 is a surface of the alignment layer exposed by peeling the transparent substrate or a surface of the retardation layer exposed by peeling the transparent substrate and the alignment layer.

Next, the phase difference layer 14 and the 2 nd adhesive layer 13 are laminated.

The 2 nd adhesive layer 13 is bonded to the phase difference layer 14 on the surface opposite to the surface on which the separator is laminated, whereby the phase difference layer 14 and the 2 nd adhesive layer 13 can be laminated. The surface of the retardation layer 14 that contacts the 2 nd adhesive layer 13 is the surface of the retardation layer 14 that is opposite to the surface that contacts the 1 st adhesive layer 12.

The polarizing plate 100 of embodiment 1 thus obtained can be laminated on a display panel or the like via the 2 nd adhesive layer 13.

[ method for producing polarizing plate according to embodiment 2]

An example of a method for manufacturing the polarizing plate 101 and the polarizing plate 102 according to embodiment 2 including at least 2 retardation layers will be described below. The polarizing plate, the adhesive layer, and the retardation layer used in the present embodiment may be the polarizing plate, the adhesive layer, and the retardation layer manufactured by the above-described methods.

As the pressure-sensitive adhesive layer, the pressure-sensitive adhesive composition described above or a pressure-sensitive adhesive layer formed on the separator can be used. Hereinafter, a case where the pressure-sensitive adhesive layer formed on the separator is used as the 1 st pressure-sensitive adhesive layer and the 2 nd pressure-sensitive adhesive layer will be described as an example.

The polarizing plate 11 is laminated with the 1 st adhesive layer 12. Specifically, the polarizing plate 11 and the 1 st adhesive layer 12 can be laminated by bonding the 1 st adhesive layer 12 to one surface of the polarizing plate 11 on the surface opposite to the surface on which the separator is laminated.

Next, the 1 st pressure-sensitive adhesive layer 12 is laminated with a laminate including a plurality of retardation layers (hereinafter, this laminate may be referred to as a "laminate of retardation layers").

The laminated body of the retardation layer is bonded to the surface of the 1 st pressure-sensitive adhesive layer 12 from which the separator is peeled off and exposed, whereby the 1 st pressure-sensitive adhesive layer 12 and the laminated body of the retardation layer can be laminated. The surface of the laminate of the retardation layer contacting the 1 st pressure-sensitive adhesive layer 12 is a surface exposed by peeling off any one of the transparent substrates located at both ends of the laminate of the retardation layer, or a surface exposed by peeling off any one of the transparent substrates located at both ends of the laminate of the retardation layer and the alignment layer.

Next, the laminated body of the phase difference layer and the 2 nd adhesive layer 13 were laminated.

The 2 nd pressure-sensitive adhesive layer 13 and the 2 nd pressure-sensitive adhesive layer 13 can be laminated by bonding the surface of the 2 nd pressure-sensitive adhesive layer 13 opposite to the surface on which the separator is laminated to the above-described laminated body of the retardation layer. The surface of the laminate of the retardation layer in contact with the 2 nd pressure-sensitive adhesive layer 13 is the surface located on the opposite side of the surface of the laminate of the retardation layer in contact with the 1 st pressure-sensitive adhesive layer 12, and is the surface of the alignment layer exposed by peeling the transparent substrate or the surface of the retardation layer exposed by peeling the transparent substrate and the alignment layer.

The polarizing plate 101 of embodiment 2 thus obtained can be laminated on a display panel or the like via the 2 nd pressure-sensitive adhesive layer 13.

According to the polarizing plate configured as described above, the occurrence of wrinkles in the polarizing plate due to deformation of the phase difference layer can be suppressed even in a high-temperature and high-humidity environment.

< use >

The polarizing plate can be used in various display devices. The display device refers to a device having a display element, and includes a light-emitting element or a light-emitting device as a light-emitting source. Examples of the display device include a liquid crystal display device, an organic EL display device, an inorganic electroluminescence (hereinafter also referred to as an inorganic EL) display device, an electron emission display device (for example, a field emission display device (also referred to as an FED) or a surface field emission display device (also referred to as an SED)), electronic paper (a display device using an electronic ink or an electrophoretic element), a plasma display device, a projection display device (for example, a grating light valve (also referred to as a GLV) display device, a display device having a digital micromirror device (also referred to as a DMD)), a piezoelectric ceramic display, and the like.

The liquid crystal display device includes any of a transmissive liquid crystal display device, a semi-transmissive liquid crystal display device, and the like. These display devices may be display devices that display two-dimensional images or may be stereoscopic display devices that display three-dimensional images.

The polarizing plate can be used particularly effectively in an organic EL display device or an inorganic EL display device.

Examples

The present invention will be described in further detail below with reference to examples, but the present invention is not limited to these examples. Various measurements and evaluations were carried out in the following manner.

[ measurement of weight average molecular weight (Mw) ]

The weight average molecular weight (Mw) of the (meth) acrylic resin for forming the pressure-sensitive adhesive layer is a weight average molecular weight in terms of polystyrene measured under the following conditions using Gel Permeation Chromatography (GPC).

[ measurement conditions ]

GPC measurement apparatus: HLC-8020 available from Tosoh corporation

GPC column (passage in the following order): tosoh corporation

TSK guard column HXL-H

TSK gel GMHXL(×2)

TSK gel G2000HXL

Determination of the solvent: tetrahydrofuran (THF)

Measurement temperature: 40 deg.C

[ measurement of storage elastic modulus of adhesive ]

The storage elastic modulus of the adhesive layer was measured by the following method.

A plurality of adhesive layers were laminated so as to have a thickness of 0.2 mm. A cylindrical body having a diameter of 8mm was punched out of the obtained adhesive layer, and this was used as a sample for measurement of the storage elastic modulus G'.

The storage elastic modulus (Pa) of the above sample was measured by a torsional shear method under the following conditions in accordance with JIS K7244-6 using a viscoelasticity measuring apparatus (MCR 300, manufactured by Physica).

[ measurement conditions ]

Normal force F_N：1N

Strain γ: 1 percent of

Frequency: 1Hz

Temperature: 25 deg.C

[ measurement of thickness of adhesive layer ]

The thickness of the adhesive layer was measured by using a digital micrometer MH-15M manufactured by Nikon K.K.

[ measurement of puncture Strength ]

The puncture test was carried out using a portable compression tester "KES-G5 needle penetration force measurement method" manufactured by Kato-tech corporation fitted with a needle having a spherical tip (tip diameter of 1 mm. phi., 0.5R), under the measurement conditions of a puncture speed of 0.0033 cm/sec at a temperature of 23. + -. 3 ℃. The puncture test was performed on 12 test pieces, and the puncture strength measured by the puncture test was set as the average value thereof.

[ measurement of moisture permeability ratio ]

The moisture permeability ratio of the retardation layer was measured in the following manner.

The adhesive composition A described later was applied to a substrate using a bar coater to form an adhesive composition layer having a thickness of 2 to 3 μm, thereby obtaining a laminate for evaluating moisture permeability of the substrate. As the substrate, a triacetyl cellulose film manufactured by Konica Minolta K.K. was used.

A retardation layer was further laminated on the pressure-sensitive adhesive composition layer of the laminate for moisture permeability evaluation of the substrate to obtain a laminate for moisture permeability evaluation of a retardation layer.

The moisture permeability of the obtained laminate for evaluation was measured in accordance with JIS Z0208: 1976 method for testing moisture permeability of moisture-proof packaging Material (cup method), measured at 40 ℃ and 90% RH humidity.

The thickness of the triacetyl cellulose film used was 20 μm. The triacetyl cellulose film obtained in the same manner as above had a moisture permeability of 1200g/m²·24h。

The laminate for evaluating the moisture permeability of the substrate had a moisture permeability of 1000g/m²·24h。

The moisture permeability of the laminate for moisture permeability evaluation of the retardation layer was measured, and the moisture permeability ratio was calculated by dividing the moisture permeability of the laminate for moisture permeability evaluation of the substrate.

[ measurement of Water vapor Transmission amount ]

The water vapor permeability of the pressure-sensitive adhesive layer was measured using a water vapor permeability measuring instrument (manufactured by Lyssy corporation, model name "Lyssy-L80-5000") under conditions of a temperature of 40 ℃ and a humidity of 90% RH.

[ production of adhesive agent ]

The adhesive is produced by the following method.

[ production of Binders A to D ]

95.0 parts by mass of n-butyl acrylate, 4.0 parts by mass of acrylic acid, 1.0 part by mass of 2-hydroxyethyl acrylate, 200 parts by mass of ethyl acetate, and 0.08 part by mass of 2, 2-azobisisobutyronitrile were charged into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube, and the air in the reaction vessel was replaced with nitrogen. The reaction solution was heated to 60 ℃ under nitrogen atmosphere with stirring, reacted for 6 hours, and then cooled to room temperature. The weight average molecular weight of a part of the obtained solution was measured, and as a result, the formation of 180 ten thousand (meth) acrylate polymers was confirmed.

100 parts by mass (value in terms of solid content; the same applies hereinafter) of the (meth) acrylate polymer obtained in the above step, 1.5 parts by mass of trimethylolpropane-modified tolylene diisocyanate (product name "Coronate (registered trademark) L", manufactured by Tosoh corporation) as an isocyanate-based crosslinking agent, 0.30 parts by mass of 3-glycidoxypropyltrimethoxysilane (product name "KBM 403", manufactured by shin-Etsu chemical Co., Ltd.) as a silane coupling agent, 7.5 parts by mass of ethoxylated isocyanuric acid trimethacrylate (product name "A-9300", manufactured by Xinzhou chemical Co., Ltd.) as an ultraviolet curable compound, and 0.5 parts by mass of 2-methyl-1- (4-methylthiophenyl) -2-morpholinopropane-1-one (product name: Irgacure (registered trademark) 907, manufactured by BASF) as a photopolymerization initiator were mixed together, the mixture was sufficiently stirred and diluted with ethyl acetate, thereby obtaining a coating solution of the adhesive composition.

The coating solution was applied to a release-treated surface (release layer surface) of a separator (SP-PLR 382190, manufactured by Lintec corporation) with a thickness of 5 μm (adhesive A), 15 μm (adhesive B), 20 μm (adhesive C), or 25 μm (adhesive D) after drying by an applicator, and then dried for 1 minute at 100, and another separator (SP-PLR 381031, manufactured by Lintec corporation) was bonded to the surface of the adhesive layer opposite to the surface to which the separator was bonded. Using an ultraviolet irradiation apparatus with a conveyor belt (manufactured by Fusion UV Systems, D Bulb as a lamp)]Irradiating with ultraviolet ray (irradiation intensity 500 mW/cm) through a release sheet²Cumulative light amount 500mJ/cm²) To obtain an adhesive layer with spacers attached to both sides.

The storage elastic modulus G' of the adhesives A to D was 125,000Pa at 25 ℃.

The water vapor transmission rates of the adhesive A, the adhesive B, the adhesive C and the adhesive D are 7600g/m respectively²·24h、5500g/m²·24h、5000g/m²·24h、4200g/m²·24h。

[ production of adhesive E, F ]

A reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device and a nitrogen inlet tube was charged with 97.0 parts by mass of n-butyl acrylate, 3.0 parts by mass of 2-hydroxyethyl acrylate, 200 parts by mass of ethyl acetate and 0.08 part by mass of 2, 2-azobisisobutyronitrile, and the air in the reaction vessel was replaced with nitrogen gas. The reaction solution was heated to 60 ℃ under nitrogen atmosphere with stirring, reacted for 6 hours, and then cooled to room temperature. The weight average molecular weight of a part of the obtained solution was measured, and as a result, the formation of 180 ten thousand (meth) acrylate polymers was confirmed.

100 parts by mass (value in terms of solid content; the same applies hereinafter) of the (meth) acrylate polymer obtained in the above step, 1.0 part by mass of trimethylolpropane-modified xylylene diisocyanate (trade name "Takenate (registered trademark) D-110N", manufactured by Mitsui chemical Co., Ltd.) as an isocyanate-based crosslinking agent, and 0.30 part by mass of 3-glycidoxypropyltrimethoxysilane (trade name "KBM 403", manufactured by shin-Etsu chemical Co., Ltd.) as a silane coupling agent were mixed, sufficiently stirred, and diluted with ethyl acetate to obtain a coating solution of the adhesive composition.

The coating solution was applied to a release-treated surface (release layer surface) of a separator (SP-PLR 382190, manufactured by Lintec corporation) with a thickness of 15 μm (adhesive E) or 20 μm (adhesive F) after drying by an applicator, and then dried for 1 minute at 100 deg.C, and another separator (SP-PLR 381031, manufactured by Lintec corporation) was bonded to the surface of the adhesive layer opposite to the surface to which the separator was bonded, to obtain an adhesive layer having separators on both surfaces.

The storage elastic modulus G' of the adhesive E, F was 45,200Pa at 25 ℃.

The water vapor transmission rate of the adhesive E, F is 8200g/m²·24h、4400g/m²·24h。

[ production of Binders G to K ]

97.0 parts by mass of n-butyl acrylate, 1.0 part by mass of acrylic acid, 0.5 part by mass of 2-hydroxyethyl acrylate, 200 parts by mass of ethyl acetate, and 0.08 part by mass of 2, 2-azobisisobutyronitrile were charged into a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen introduction tube, and the air in the reaction vessel was replaced with nitrogen. The reaction solution was heated to 60 ℃ under nitrogen atmosphere with stirring, reacted for 6 hours, and then cooled to room temperature. The weight average molecular weight of a part of the obtained solution was measured, and as a result, the formation of 180 ten thousand (meth) acrylate polymers was confirmed.

100 parts by mass (value in terms of solid content; the same applies hereinafter) of the (meth) acrylate polymer obtained in the above step, 0.30 part by mass of trimethylolpropane-modified tolylene diisocyanate (trade name "Coronate (registered trademark) L", manufactured by tokyo co., ltd.) as an isocyanate-based crosslinking agent, and 0.30 part by mass of 3-glycidoxypropyltrimethoxysilane (trade name "KBM 403", manufactured by shin-Etsu chemical Co., Ltd.) as a silane coupling agent were mixed, sufficiently stirred, and diluted with ethyl acetate to obtain a coating solution of the pressure-sensitive adhesive composition.

The coating solution was applied to a release-treated surface (release layer surface) of a separator (SP-PLR 382190, manufactured by Lintec corporation) with a thickness of 6 μm (adhesive H), 10 μm (adhesive I), 20 μm (adhesive J), 15 μm (adhesive G), or 25 μm (adhesive K) after drying, and then dried at 100 ℃ for 1 minute, and another separator (SP-PLR 381031, manufactured by Lintec corporation) was bonded to the surface of the adhesive layer opposite to the surface to which the separator was bonded, thereby obtaining an adhesive layer having separators on both surfaces.

The storage elastic modulus G' of the adhesives G to K was 25500Pa at 25 ℃.

The water vapor transmission rates of the adhesive G, the adhesive H, the adhesive I, the adhesive J and the adhesive K were 6300G/m²·24h、8200g/m²·24h、6800g/m²·24h、4700g/m²·24h、3600g/m²·24h。

The thicknesses and storage elastic moduli at 25 ℃ of the prepared adhesives a to K are shown in table 1.

[ Table 1]

[ production of polarizing plate (1) ]

A polyvinyl alcohol film having an average polymerization degree of about 2400 and a saponification degree of 99.9 mol% or more and a thickness of 30 μm was immersed in pure water at 30 ℃ and then immersed in an aqueous solution at 30 ℃ having a mass ratio of iodine, potassium iodide and water of 0.02: 2: 100 to carry out iodine dyeing (hereinafter, also referred to as an iodine dyeing step). The polyvinyl alcohol film having undergone the iodine dyeing step was immersed in an aqueous solution of potassium iodide, boric acid and water at 56.5 ℃ in a mass ratio of 12: 5: 100 to carry out a boric acid treatment (hereinafter, also referred to as boric acid treatment step). The polyvinyl alcohol film subjected to the boric acid treatment step was washed with pure water at 8 ℃ and dried at 65 ℃ to obtain a polarizing plate (thickness after stretching: 12 μm) in which iodine was adsorbed and oriented in polyvinyl alcohol. In this case, stretching is performed in the iodine dyeing step and the boric acid treatment step. The total draw ratio of the drawing was 5.3 times.

A saponified triacetyl cellulose film (KC 4UYTAC manufactured by Konica Minolta K.K., 40 μm thick) was bonded to each of both sides of the obtained polarizing plate with a nip roll via an aqueous adhesive. The resulting laminate was dried at 60 ℃ for 2 minutes while maintaining the tension of 430N/m, to obtain a polarizing plate (1) having triacetyl cellulose films as protective films on both sides. The aqueous adhesive was prepared by adding 3 parts of carboxyl-modified polyvinyl alcohol (Kuraray Poval KL318, manufactured by Kuraray corporation) and 1.5 parts of water-soluble polyamide-epoxy Resin (an aqueous solution having a solid content of 30% of Sumirez Resin 650, manufactured by takaki chemical corporation) to 100 parts of water.

The optical properties of the obtained polarizing plate (1) were measured using a spectrophotometer (V7100, manufactured by japan spectrographic corporation). The obtained polarizing plate (1) had a visual sensitivity-modified single-component transmittance of 42.1%, a visual sensitivity-modified polarization degree of 99.996%, a single-component hue a of-1.1, and a single-component hue b of 3.7.

[ production of retardation layer 1]

A layer imparting a retardation of lambda/4, which comprises a layer obtained by curing a nematic liquid crystal compound, an alignment film and a transparent substrate, is prepared as a 1 st retardation layer. The total thickness of the layer obtained by curing the nematic liquid crystal compound and the alignment film was 2 μm. The moisture permeability ratio of the 1 st retardation layer was 0.48.

[ production of retardation layer 2]

Using a polyethylene terephthalate substrate having a thickness of 38 μm as a transparent substrate, a composition for a vertical alignment layer was applied to one surface of the substrate so as to have a film thickness of 3 μm, and the substrate was irradiated with 20mJ/cm²Polarizing ultraviolet rays to produce an alignment layer. As the composition for a vertical alignment layer, a mixture of 2-phenoxyethyl acrylate, tetrahydrofurfuryl acrylate, dipentaerythritol triacrylate and bis (2-vinyloxyethyl) ether in a ratio of 1: 4: 5, to which LUCIRIN (registered trademark) TPO as a polymerization initiator was added in a ratio of 4%, was used.

Next, a liquid crystal composition containing a photopolymerizable nematic liquid crystal compound (RMM 28B, manufactured by Merck) was applied on the alignment layer formed by the die coater. In the liquid crystal composition, a mixed solvent in which Methyl Ethyl Ketone (MEK), methyl isobutyl ketone (MIBK), and Cyclohexanone (CHN) having a boiling point of 155 ℃ are mixed at a mass ratio (MEK: MIBK: CHN) of 35: 30: 35 is used as a solvent. Then, a liquid crystal composition prepared so that the solid content is 1 to 1.5g is applied to the alignment layer in an amount of 4 to 5g (wet).

After the liquid crystal composition was applied to the alignment layer, the liquid crystal composition was dried at 75 ℃ for 120 seconds. Then, the liquid crystal compound is polymerized by irradiation with Ultraviolet (UV) rays to obtain a positive C layer including a layer obtained by curing a photopolymerizable nematic liquid crystal compound, an alignment layer, and a transparent substrate. The total thickness of the layer obtained by curing the photopolymerizable nematic liquid crystal compound and the alignment layer was 4 μm. Further, the moisture permeability ratio of the 2 nd retardation layer was 0.60.

[ production of a layered product (1) of retardation layer ]

The 2 sheets of the 1 st retardation layer were bonded with an ultraviolet-curable adhesive so that the respective retardation layer surfaces (the surfaces opposite to the transparent base material) became bonding surfaces. Subsequently, the ultraviolet-curable adhesive is cured by irradiation with ultraviolet rays. In this manner, a laminated body of retardation layers having 2 sheets of the 1 st retardation layer (hereinafter, this laminated body is referred to as "laminated body of retardation layers (1)") was produced. The thickness of the laminated body (1) of the retardation layer was 5 μm. The moisture permeability ratio of the laminated body (1) of the retardation layer was 0.24.

[ production of a laminated body (2) of retardation layers ]

The 1 st retardation layer and the 2 nd retardation layer were bonded to each other with an ultraviolet-curable adhesive so that the retardation layer surfaces (the surfaces opposite to the transparent base material) became bonding surfaces. Subsequently, the ultraviolet-curable adhesive is cured by irradiation with ultraviolet rays. In this manner, a laminated body of retardation layers having the 1 st retardation layer and the 2 nd retardation layer (hereinafter, this laminated body is referred to as "laminated body of retardation layers (2)") was produced. The thickness of the laminated body (2) of the retardation layer was 8 μm. The transparent base material was peeled from each of both surfaces of the retardation layer laminate (2), and then the puncture strength of the retardation layer laminate (2) was measured. The puncture strength of the laminated body (2) of the retardation layer was 70 gf.

[ production of a laminated body (3) of retardation layers ]

The laminated body (1) of the retardation layer and the 2 nd retardation layer were bonded to each other with an ultraviolet-curable adhesive so that the retardation layer surface (the surface opposite to the transparent base material) became a bonding surface. Subsequently, the ultraviolet-curable adhesive is cured by irradiation with ultraviolet rays. In this manner, a laminated body of retardation layers having 2 sheets of the 1 st retardation layer and the 2 nd retardation layer (hereinafter, this laminated body is referred to as "laminated body of retardation layers (3)") was produced. The thickness of the laminated body (3) of the retardation layer was 10 μm. The transparent base material was peeled from each of both surfaces of the phase difference layer laminate (3), and then the puncture strength of the phase difference layer laminate (3) was measured. The puncture strength of the laminated body (3) of the retardation layer was 85 gf.

[ example 1]

The adhesive B was transferred as a 1 st adhesive layer to one surface of the polarizing plate (1). The separator laminated on the adhesive B was peeled off, and laminated on the surface of the transparent substrate on the 1 st retardation layer side of the laminate (2) of the retardation layers. An adhesive F is laminated on the surface of the laminated body (2) of the phase difference layer opposite to the surface on which the polarizing plate is laminated as a 2 nd adhesive layer. In this manner, a polarizing plate was produced which successively included a protective film, a polarizing plate (1), a protective film, a 1 st adhesive layer, a 1 st retardation layer, an adhesive layer, a 2 nd retardation layer, and a 2 nd adhesive layer.

Examples 2 to 20 and comparative examples 1 to 2

Polarizing plates were produced in the same manner as in example 1, except that the adhesives shown in tables 2 and 3 were used as the 1 st adhesive and the 2 nd adhesive.

Examples 21 to 40 and comparative examples 3 to 4

Polarizing plates were produced in the same manner as in examples 2 to 20 and comparative examples 1 to 2, except that a laminated body (3) of a retardation layer was used instead of the laminated body (2) of a retardation layer. The 1 st pressure-sensitive adhesive layer is laminated on the surface of the laminate (3) of the retardation layers from which the transparent substrate on the 1 st retardation layer side is peeled, and the 2 nd pressure-sensitive adhesive layer is laminated on the surface of the laminate (3) of the retardation layers from which the transparent substrate on the 2 nd retardation layer side is peeled.

< evaluation of polarizing plate under high temperature and high humidity Environment >

The polarizing plate prepared as described above was peeled off from the separator of the 2 nd pressure-sensitive adhesive layer, and was bonded to an alkali-free glass plate ("Eagle-XG" manufactured by Corning corporation) to prepare an evaluation sample. The above evaluation sample was subjected to a pressure treatment in an autoclave at a temperature of 50 ℃ and a pressure of 5MPa for 20 minutes, and then allowed to stand in an atmosphere at a temperature of 23 ℃ and a relative humidity of 60% for one day. Thereafter, the mixture was left at 65 ℃ and 90% humidity. The appearance of the sample was visually confirmed after 336 hours, 504 hours, 672 hours, and 840 hours from the time when the evaluation sample was placed in an environment at 65 ℃ and 90% humidity.

In tables 2 to 5, the sample in which wrinkles were not generated in the polarizing plate at 840 hours, the sample in which wrinkles were generated in the polarizing plate at 672 hours, the sample in which wrinkles were generated in the polarizing plate at 504 hours, the sample in which wrinkles were generated in the polarizing plate at 336 hours, were marked as "a", the sample in which wrinkles were generated in the polarizing plate at 840 hours, and the sample in which wrinkles were generated in the polarizing plate at 336 hours, respectively. In tables 2 to 5, Log (E)₁/T₁) Denotes the storage elastic modulus E of the 1 st adhesive layer₁Divided by the thickness T₁And taking the value of the common logarithm, Log (E)₂/T₂) The storage elastic modulus E of the 2 nd adhesive layer₂Divided by the thickness T₂And takes the value of the common logarithm.

[ Table 2]

[ Table 3]

[ Table 4]

[ Table 5]

Log (E) as shown in tables 2 to 5₁/T₁) And Log (E)₂/T₂) The polarizing plate of the example having the sum of (1) and (2) of 6.4 or more was exposed to a high-temperature, high-humidity environment of 65 ℃ and 90% humidity for 336 hours, and no wrinkles were observed in the polarizing plate.

From the above results, it is shown that the present invention is useful.

Industrial applicability

The polarizing plate of the present invention is not wrinkled even in a high-temperature and high-humidity environment, and therefore, can be applied to an image display device that may be used in a high-temperature and high-humidity environment, and is industrially useful.

Description of the reference numerals

11: a polarizing plate; 12: 1, a first adhesive layer; 13: a 2 nd adhesive layer; 14: a phase difference layer; 15: a 1 st phase difference layer; 16: a 2 nd phase difference layer; 17: 1, a first adhesive layer; 18: a 2 nd adhesive layer; 19: a 3 rd phase difference layer; 100: a polarizing plate; 101: a polarizing plate; 102: a polarizing plate.

Claims

1. A polarizing plate comprising a polarizing plate, a 1 st adhesive layer, a retardation layer, and a 2 nd adhesive layer in this order,

setting the storage elastic modulus of the 1 st adhesive layer to E₁The thickness of the 1 st adhesive layer is T₁The storage elastic modulus of the 2 nd adhesive layer is set to E₂The thickness of the 2 nd adhesive layer is set as T₂When, Log (E) is satisfied₁/T₁)+Log(E₂/T₂) Not less than 6.4, said E₁、E₂Has the unit of Pa, T₁、T₂In μm.

2. The polarizing plate according to claim 1, wherein the puncture strength of the phase difference layer is 100gf or less.

3. The polarizing plate according to claim 1 or 2, wherein any one of the following (1) and (2) is satisfied:

(1) the Log (E)₁/T₁) Is more than 3.1;

(2) the Log (E)₂/T₂) Is 3.0 or more.

4. The polarizing plate according to any one of claims 1 to 3, wherein at least one of the 1 st adhesive layer and the 2 nd adhesive layer has a storage elastic modulus of 20,000Pa or more.

5. The polarizing plate of any one of claims 1 to 4, wherein at least one of the 1 st adhesive layer and the 2 nd adhesive layer has a thickness of 40 μm or less.

6. The polarizing plate according to any one of claims 1 to 5, wherein the phase difference layer comprises at least a 1 st phase difference layer and a 2 nd phase difference layer.

7. The polarizing plate according to claim 6, wherein the retardation layer is a laminate in which at least a 1 st retardation layer and a 2 nd retardation layer are laminated via an adhesive layer.

8. The polarizing plate according to claim 7, wherein the laminate has a puncture strength of 100gf or less.