TWI863355B - Polarizing plate and display device using the same - Google Patents

Abstract

Provided are a polarizing plate and a display device using the same. The polarizing plate is a thin film with high curvature and has durability in a high temperature and high humidity environment. The polarizing plate is a polarizing plate having a protective film A attached to one side of a polarizer and a protective film B attached to the other side. The polarizing plate is characterized in that the moisture permeability TA of the protective film A and the moisture permeability TB of the protective film B at 40°C and 90%RH simultaneously satisfy the following conditions (1) and (2), the protective film A has a hard coating layer, the hard coating layer is a cured film containing a composition of a (meth)acrylate compound containing an alicyclic structure and a photopolymerization initiator, and the content ratio of the (meth)acrylate compound containing an alicyclic structure in the composition is 20 mass % or more of the total solid content, and the thickness of the protective film A is less than 50 μm. 240g/m ² /day＞TA＞70g/m ² /day・・・(1) 70g/m ² /day≧TB・・・(2)

Description

Polarizing plate and display device using the same

The present invention relates to a polarizing plate and a display device using the same.

Polarizing plates used in display devices mainly use polyvinyl alcohol (PVA). PVA has very poor water resistance, so protective films are attached to both sides. In the past, protective films for polarizing plates used hard-coated films with a moisture permeability of about 300 to 1000 g/ ^m2 /day, which were laminated on triacetyl cellulose (TAC) films. However, under the harsh conditions of high temperature and high humidity, there is a problem that PVA cannot be prevented from absorbing water and causing deterioration.

Therefore, the development of protective films using cycloolefin polymer (COP) or polyethylene terephthalate (PET) instead of TAC has been carried out, and the moisture permeability of the protective film can be reduced to about 5 to 100 g/m ² /day. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Application Publication No. 2021-144076

[Problems to be solved by the invention]

In recent years, polarizing plates with durability under extremely high temperature and humidity have been required for automotive applications. In high temperature and humidity environments, when the water vapor barrier property of the protective film is too high, even if there is no moisture intrusion from the outside, there are cases where moisture generated by the adhesive used when bonding the substrate or protective film stays in the polarizing plate and causes deterioration.

In addition, as the size of in-vehicle displays increases, their applications also expand, and there are cases where displays are used not only on flat surfaces but also on curved surfaces. Based on this background, polarizing plates are required to be thinner and more flexible.

Therefore, the purpose of the present invention is to provide a polarizing plate and a display device using the same, wherein the polarizing plate is a thin film and highly curved, and has durability in a high temperature and high humidity environment. [Means for solving the problem]

The polarizing plate of the present invention is a polarizing plate having a protective film A attached to one side of a polarizer and a protective film B attached to the other side. The polarizing plate is characterized in that: the moisture permeability TA of the protective film A and the moisture permeability TB of the protective film B at 40°C and 90%RH simultaneously satisfy the following conditions (1) and (2); the protective film A has a hard coating layer, which is a cured film of a composition containing a (meth)acrylate compound (A), a (meth)acrylate compound containing an alicyclic structure (B), and a photopolymerization initiator (C); the content ratio of the (meth)acrylate compound (B) in the composition is 20 mass % or more of the total solid content; and the thickness of the protective film A is less than 50 μm. 240g/m ² /day＞TA＞70g/m ² /day・・・(1) 70g/m ² /day≧TB・・・(2)

Furthermore, the display device of the present invention is equipped with the above-mentioned polarizing plate. [Effects of the invention]

According to the present invention, a polarizing plate and a display device using the same can be provided. The polarizing plate is a thin film with high curvature and has durability in a high temperature and high humidity environment.

[Form used to implement the invention]

The polarizing plate 10 includes a polarizer 1, a protective film A attached to one side of the polarizer 1, and a protective film B attached to the other side of the polarizer 1. The polarizer 1 is formed by allowing a polyvinyl alcohol (PVA) film to adsorb iodine or a dye and align it. Since the PVA constituting the polarizer 1 has poor strength and water resistance, the protective films A and B are attached to both sides of the polarizer 1.

The protective film A is a hard coating film having a hard coating layer 3 laminated on one surface of a TAC film 2. The hard coating layer 3 covers the soft TAC film 2 and imparts hardness to the functional layer of the protective film A.

The hard coating layer 3 can be formed by applying a composition containing a (meth)acrylate compound having an alicyclic structure and a photopolymerization initiator on one side of the TAC film 2, drying the composition, and curing the coating by ultraviolet irradiation. In this specification, "(meth)acrylate" is a general term for both acrylate and methacrylate, and "(meth)acryl" is a general term for both acryl and methacryl.

The (meth)acrylate containing an alicyclic structure improves the hydrophobicity of the hard coating layer 3, imparts water vapor barrier properties to the protective film A, and improves the bending resistance of the hard coating layer 3. The (meth)acrylate containing an alicyclic structure is not particularly limited, but for example, one or more (meth)acrylates having a cyclopentane structure, a dicyclopentane structure, a cyclohexane structure, a cyclodecane structure, a tricyclodecane structure, an isoborneol structure, and an adamantane structure can be used.

Specific examples of the (meth)acrylate containing an alicyclic structure include cyclohexyl (meth)acrylate, cyclohexanedimethanol mono(meth)acrylate, 4-tert-butylcyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexyl (meth)acrylate, 3,3,5-trimethylcyclohexanol (meth)acrylate, dicyclopentyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentyl (meth)acrylate, and dicyclopentenyl (meth)acrylate. Monofunctional (meth)acrylates such as pentylene ester, 2-dicyclopentenyloxyethyl (meth)acrylate, dicyclopentenyloxyethyl methacrylate, bornyl (meth)acrylate, isobornyl (meth)acrylate, tricyclodecyl (meth)acrylate, tricyclodecane dimethanol mono(meth)acrylate, and adamantyl (meth)acrylate, or cyclohexanedimethanol di(meth)acrylate, dicyclopentyl di(meth)acrylate, dicyclopentyl alkenyl di(meth)acrylate, dicyclopentadienyl di(meth)acrylate, bornyl di(meth)acrylate, isobornyl di(meth)acrylate, tricyclodecyl di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, adamantane di(meth)acrylate, adamantane dimethanol di(meth)acrylate, adamantane diethanol di(meth)acrylate, dihydroxymethyl dicyclopentane di(meth)acrylate, Polyfunctional (meth)acrylates such as norbornane dihydroxymethyl di(meth)acrylate, cyclohexanedimethanol tri(meth)acrylate, adamantyl tri(meth)acrylate, adamantrimethanol tri(meth)acrylate, norbornane trihydroxymethyl tri(meth)acrylate, tricyclodecane trimethanol tri(meth)acrylate, and perhydro-1,4,5,8-dimethylnaphthalene-2,3,7-(oxymethyl)tri(meth)acrylate. These (meth)acrylates may be used alone or as a mixture of one or more.

The blending ratio of the (meth)acrylate containing an alicyclic structure is preferably set to 20% by mass or more of the total solid content of the hard coat layer forming composition. When the blending ratio of the (meth)acrylate containing an alicyclic structure is 20% by mass or more of the total solid content, the moisture permeability of the protective film A can be within the range described below, and the bending resistance of the hard coat layer 3 can be improved. The upper limit of the blending ratio of the (meth)acrylate containing an alicyclic structure is not particularly limited, but it is 99% by mass or less of the total solid content due to the addition of a photopolymerization initiator.

In addition to the (meth)acrylate containing an alicyclic structure, other active energy ray-curable compounds may be used. As the active energy ray-curable compound, for example, a monofunctional, difunctional, or trifunctional or higher-functional (meth)acrylate monomer may be used.

Examples of the monofunctional (meth)acrylate compound include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, glycidyl (meth)acrylate, acrylamide, N-vinyl pyrrolidone, tetrahydrofurfuryl acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isoborneol (meth)acrylate, and 1,2-dimethylformamide. )Isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, cetyl (meth)acrylate, octadecyl (meth)acrylate, benzyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, ethyl carbitol (meth)acrylate, phosphoric acid (meth)acrylate, ethylene oxide modified phosphoric acid (meth)acrylate, phenoxy (meth)acrylate, ethylene oxide modified phenoxy (meth)acrylate, propylene oxide modified phenyl (meth)acrylate esters, phenol (meth) acrylate, ethylene oxide modified nonylphenol (meth) acrylate, propylene oxide modified nonylphenol (meth) acrylate, methoxydiethylene glycol (meth) acrylate, methoxypolybutylene glycol (meth) acrylate, methoxypropylene glycol (meth) acrylate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, 2-(meth)acryloyloxyethyl hydrophthalate, 2-(meth)acryloyloxy The invention also includes 2-(meth)acryloxypropyl hexahydrophthalate, 2-(meth)acryloxypropyl tetrahydrophthalate, dimethylaminoethyl (meth)acrylate, trifluoroethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropropyl (meth)acrylate, adamantane derivative mono(meth)acrylate such as adamantane acrylate having a monovalent mono(meth)acrylate derived from 2-adamantane or adamantanediol, and the like.

Examples of bifunctional (meth)acrylates include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, hexanediol di(meth)acrylate, nonanediol di(meth)acrylate, ethoxylated hexanediol di(meth)acrylate, propoxylated hexanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethoxylated neopentyl glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, hydroxytrimethylol neopentyl glycol di(meth)acrylate, and the like.

Examples of trifunctional or higher (meth)acrylates include tri(meth)acrylates such as trihydroxymethylpropane tri(meth)acrylate, ethoxylated tri(meth)acrylate, propoxylated tri(meth)acrylate, tri(meth)acrylates such as tris(hydroxyethyl)isocyanurate tri(meth)acrylate, and glycerol tri(meth)acrylate, and tri(meth)acrylates such as pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, and ditrihydroxymethylpropane tri(meth)acrylate. Acid ester compounds, or trifunctional or higher polyfunctional (meth)acrylate compounds such as pentaerythritol tetra(meth)acrylate, ditrihydroxymethylpropane tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, ditrihydroxymethylpropane penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and ditrihydroxymethylpropane hexa(meth)acrylate, or polyfunctional (meth)acrylate compounds in which a part of these (meth)acrylates is substituted with alkyl or ε-caprolactone, etc.

Furthermore, urethane (meth)acrylates may be used as the polyfunctional monomer. Examples of urethane (meth)acrylates include those obtained by reacting a product obtained by reacting an isocyanate monomer or prepolymer with a polyester polyol and reacting a (meth)acrylate monomer having a hydroxyl group.

Examples of urethane (meth)acrylates include pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol triacrylate toluene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate toluene diisocyanate urethane prepolymer, pentaerythritol triacrylate isophorone diisocyanate urethane prepolymer, and dipentaerythritol pentaacrylate isophorone diisocyanate urethane prepolymer.

The above-mentioned multifunctional monomer may be used alone or in combination of two or more. The above-mentioned multifunctional monomer may be a monomer in the composition or a partially polymerized oligomer.

As the polymerization initiator, a polymerization initiator that generates free radicals by ultraviolet irradiation can be used. As the polymerization initiator, a free radical polymerization initiator such as acetophenone, benzophenone, thiothione, benzoin, benzoin methyl ether, acylphosphine oxide, etc. can be used. As the polymerization initiator, for example, diphenyl (2,4,6-trimethylbenzyl) phosphine oxide, bis (2,4,6-trimethylbenzyl) phenyl phosphine oxide, 2,2-diethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-phenylacetophenone, biphenyl acyl, benzoin, benzoin methyl ether, benzoin ethyl ether, p-chlorobenzophenone, p-methoxybenzophenone, Michler's ketone, acetophenone, 2-chlorothiothione, etc. can be used. Among these, one type may be used alone or two or more types may be used in combination.

A solvent may be added to the hard coating layer forming composition as needed. As the solvent, one or a mixture of two or more of the following can be used: alcohols such as methanol, ethanol, 1-propanol, 2-propanol, butanol, isopropanol, and isobutanol; ketones such as acetone, methyl ethyl ketone, cyclohexanone, and methyl isobutyl ketone; ketone alcohols such as diacetone alcohol; aromatic hydrocarbons such as benzene, toluene, and xylene; glycols such as ethylene glycol, propylene glycol, and hexylene glycol; glycol ethers such as ethyl cellulose, butyl cellulose, ethyl carbitol, butyl carbitol, diethyl cellulose, diethyl carbitol, and propylene glycol monomethyl ether; esters such as dimethyl carbonate, methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, butyl acetate, and amyl acetate; ethers such as dimethyl ether and diethyl ether; N-methylpyrrolidone; and dimethylformamide.

Furthermore, various additives such as antistatic agents, defoaming agents, antioxidants, ultraviolet absorbers, infrared absorbers, colorants, light stabilizers, polymerization inhibitors, photosensitizers, antifouling agents, leveling agents, oil repellents, water repellents, fingerprint adhesion inhibitors, etc. may be added to the hard coat layer forming composition as needed.

The method for applying the hard coating layer forming composition is not particularly limited, and for example, the hard coating layer can be applied using a rotary coater, a roll coater, a reverse roll coater, a gravure coater, a micro gravure coater, a knife coater, a rod coater, a wire rod coater, a die coater, a dip coater, a spray coater, an applicator, or the like.

The thickness (total thickness) of the protective film A is preferably less than 50 μm. When the polarizing plate 10 is bent with the hard coating layer 3 on the outside, stress is concentrated on the surface of the hard coating layer 3. When the thickness of the protective film A is greater than 50 μm, cracks are more likely to occur in the hard coating layer 3 when the polarizing plate 10 is bent.

In addition, the pencil hardness of the protective film A (hard coating film) is preferably 3H or more. When the pencil hardness of the protective film A is 3H or more, the surface hardness of the polarizing plate is good and the durability is improved.

The thickness of the TAC film 2 and the hard coating layer 3 used for the protective film A are not particularly limited as long as the layer thickness of the protective film A is 50 μm, but as an example, the thickness of the TAC film 2 is 25 to 40 μm and the thickness of the hard coating layer 3 is 5 to 10 μm.

The protective film B is a low moisture permeable film made of any one of cycloolefin polymer (COP), polyethylene terephthalate (PET) and polymethyl methacrylate (PMMA). The protective film B is attached to the polarizing lens 1 through a UV-curable adhesive, for example. The thickness of the protective film B is not particularly limited, but is preferably 10 to 100 μm.

Furthermore, in the display device, the protective film B is disposed on the display panel side, and the hard coating layer of the protective film A is disposed on the visual recognition side (the side opposite to the display panel).

The TAC film of the protective film A is bonded to the PVA film of the polarizing lens 1 using a water paste (PVA aqueous solution) as an adhesive. In addition, in order to ensure the adhesion between the TAC film and the PVA film, the protective film A is subjected to a saponification treatment before bonding. Since a water paste is used in bonding the protective film A to the polarizing lens 1, moisture may be contained in the adhesive layer and the TAC film even after the drying step. When both the protective films A and B are formed of films with low moisture permeability, although the intrusion of moisture from the outside is suppressed, in an extremely high temperature environment such as in a car in summer, the moisture contained in the adhesive and/or the TAC film continues to remain in the polarizing plate 10, thereby causing the polarizing lens 1 to deteriorate. Therefore, in the polarizing plate 10 of the present embodiment, by setting a difference between the moisture permeability of the protective film A and the moisture permeability of the protective film B, and setting the moisture permeabilities of the protective film A and the protective film B to specific ranges, the deterioration of the polarizing lens 1 caused by moisture from the adhesive and/or TAC film is suppressed.

Specifically, if the moisture permeabilities of protective films A and B at 40°C and 90%RH are denoted as TA and TB, respectively, then TA and TB satisfy the following conditions (1) and (2) simultaneously. In addition, the moisture permeabilities TA and TB are values measured according to the moisture permeability test method (cup method) for moisture-proof packaging materials specified in JIS Z 0208:1976. 240g/ ^m2 /day＞TA＞70g/ ^m2 /day・・・(1) 70g/ ^m2 /day≧TB・・・(2)

The polarizing plate 10 of this embodiment satisfies the above-mentioned conditions (1) and (2), thereby suppressing the intrusion of moisture from the outside into the interior of the polarizing plate, and at the same time, when exposed to a high temperature environment of, for example, 85°C, the moisture generated by the adhesive used for bonding the protective film A and the polarizer 1 and/or the TAC film of the protective film A can be discharged to the outside.

As described above, the polarizing plate 10 of the present embodiment has a protective film A and a protective film B that can satisfy the above-mentioned conditions (1) and (2). With this structure, the protective film B disposed on the display panel side almost blocks the entry and exit of moisture. On the other hand, the protective film A disposed on the visual recognition side can suppress the intrusion of moisture from the outside into the interior of the polarizing plate 10, while releasing the moisture generated inside the polarizing plate 10 in an extremely high temperature environment. Therefore, in the polarizing plate 10 of the present embodiment, when used in a high temperature environment, since the moisture generated inside the polarizing plate 10 does not stay, the deterioration of the polarizer is suppressed, and the optical performance of the polarizing plate 10 can be maintained for a longer period of time.

Furthermore, since the thickness of the protective film A is less than 50 μm, the polarizing plate 10 can be made thinner, and at the same time, when the polarizing plate 10 is bent, cracks in the hard coating layer 3 can be suppressed, thereby improving the bending resistance.

Therefore, according to this embodiment, a polarizing plate 10 can be provided, which is a thin film and has high curvature, and at the same time has durability in a high temperature and high humidity environment.

The polarizing plate 10 of this embodiment can be combined with an image display panel such as a liquid crystal panel or an organic EL panel to form an image display device. The image display device can have a touch panel. Since the polarizing plate 10 of this embodiment has high flexibility and durability in a high temperature and high humidity environment, it can be suitably used as an image display device provided on a curved surface in a car. [Example]

Hereinafter, examples for specifically implementing the present invention will be described.

A hard coat layer forming composition containing a polymerizable material, a hydrophobic material, a photopolymerization initiator and a solvent in the proportions shown in Table 1 is prepared. The proportion of dihydrocyclopentadiethyl acrylate in the total solid content of the hard coat layer forming composition is as follows. ・Composition 1: 18% ・Composition 2: 45% ・Composition 3: 90% ・Composition 4: 9% ・Composition 5: 0%

The prepared hard coating layer forming composition was applied to a 40 μm thick TAC film (trade name: TJ25, manufactured by Fuji Film Co., Ltd.) using a wire bar coater so that the film thickness after curing became the value listed in Table 2. After drying the coating film by heating in an oven at 60°C for 1 minute, the coating film was cured by irradiating ultraviolet rays in a UV curing device in a nitrogen atmosphere (oxygen concentration 500 ppm or less) so that the accumulated light amount became 100 mJ/cm ² to prepare a protective film A (hard coating film). In addition, a 26 μm thick COP film was used as a protective film B.

[Table 1] Polymeric materials Hydrophobic materials Photopolymerization initiator Solvent 1 Solvent 2 Material Name Blending amount (weight) Material Name Blending amount (weight) Material Name Blending amount (weight) Material Name Blending amount (weight) Material Name Blending amount (weight) Composition 1 Pentaerythritol triacrylate 36.0 Cyclopentaethyl dihydrogen acrylate 9.0 Irgacure 184 (1-Hydroxycyclohexylphenyl ketone) 5.0 Dimethyl carbonate 32.5 Methyl isobutyl ketone 17.5 Composition 2 22.5 22.5 Composition 3 0 45.0 Composition 4 40.5 4.5 Composition 5 45.0 0 Composition 6 22.5 Colloidal Silica 22.5

The TAC film surface of the protective film A and the polarizer were bonded together using a water paste and dried, and then the protective film B was bonded to the polarizer using a UV curable adhesive. The UV curable adhesive was cured by irradiating with UV rays to obtain a polarizing plate.

(Moisture permeability) According to the moisture permeability test method (cup method) for moisture-proof packaging materials specified in JIS Z 0208:1976, the moisture permeability TA of the protective film A and the moisture permeability TB of the protective film B before being attached to the polarizing filter are measured at 40°C and 90RH%.

(Bending resistance) The protective film A is cut into samples of 3cm×10cm in size, and then wound on a steel bar (mandrel) of a specific diameter with the hardened film on the outside. The minimum diameter of the steel bar without cracks on the surface is used as the evaluation value of bending resistance.

(Pencil hardness) Using a pencil (uni, 3H manufactured by Mitsubishi Pencil Co., Ltd.) and a Clemens scratch tester (HA-301 manufactured by Tester Industry Co., Ltd.), a scratch test was performed on the hard coating surface of the protective film A under the conditions of a load of 500g and a scratching speed of 0.5mm/sec. The scratch test was performed on 5 samples, and samples with more than 2 scratches on the hard coating surface were evaluated as NG, and the rest were evaluated as OK.

(Polarization degree of polarizing plate after high temperature and high humidity durability test) The polarizing plates of each embodiment and each comparative example were placed in a constant temperature chamber at 85°C and 85%RH, and the polarization degree was measured 240 hours and 500 hours after the placement. The polarization degree was calculated by correcting the visual sensitivity of the 2-degree field (C light source) of JIS Z 8701 for the value measured by an absorptiophotometer with an integrating sphere ("V7100" manufactured by JASCO Corporation).

Table 2 shows the properties of the protective films A and B of each embodiment and each comparative example and the measured values of the polarization degree of the polarizing plate (initial value, before and after the high temperature and high humidity durability test).

[Table 2] Protective Film A Features Protective Film B Characteristics Polarizing plate characteristics Composition Total thickness [µm] Substrate thickness [µm] HC layer composition HC layer thickness [µm] Moisture permeability TA [g・m ² /day] Bending resistance (axle diameter) [mm] Pencil hardness Composition Moisture permeability TB [g・m ² /day] Polarization degree[%] Early days After 240 hours of operation After 500 hours of operation Embodiment 1 HC laminated TAC film 32 25 Composition 1 7 232 ϕ2 OK COP Film 5 99.510 99.489 99.446 Embodiment 2 47 40 Composition 1 7 204 ϕ2 OK 99.500 99.464 Embodiment 3 49 40 Composition 1 9 165 ϕ2 OK 99.496 99.474 Embodiment 4 32 25 Composition 2 7 202 ϕ2 OK 99.488 99.466 Embodiment 5 47 40 Composition 2 7 166 ϕ2 OK 99.502 99.476 Embodiment 6 32 25 Composition 3 7 151 ϕ2 OK 99.504 99.491 Embodiment 7 47 40 Composition 3 7 124 ϕ2 OK 99.494 99.481 Comparison Example 1 50 40 Composition 1 10 148 φ3 OK 99.492 99.489 Comparison Example 2 32 25 Composition 4 7 251 ϕ2 OK 99.462 93.300 or less Comparison Example 3 35 25 Composition 4 10 233 φ3 OK 99.484 99.404 Comparison Example 4 47 40 Composition 4 7 196 φ3 OK 99.500 99.485 Comparison Example 5 49 40 Composition 4 9 177 φ3 OK 99.507 99.482 Comparative Example 6 50 40 Composition 4 10 159 ϕ4 OK 99.489 99.466 Comparison Example 7 32 25 Composition 5 7 292 ϕ2 OK 99.434 93.300 or less Comparative Example 8 47 40 Composition 5 7 270 φ3 OK 99.466 93.300 or less Comparative Example 9 50 40 Composition 5 10 250 ϕ4 OK 99.468 93.300 or less Comparative Example 10 32 25 Composition 6 7 238 ϕ4 OK 99.477 99.411 Comparative Example 11 47 40 Composition 6 7 210 φ5 OK 99.481 99.432 Comparative Example 12 PMMA film 40 60 - - 40 ϕ1 NG 99.407 93.300 or less Comparative Example 13 COP Film 26 26 - - 5 ϕ1 NG 99.396 93.300 or less

The polarizing plates of Examples 1 to 7 show high polarization values even after being placed in a constant temperature chamber at 85°C and 85%RH for 500 hours because the moisture permeability TA of the protective film A and the moisture permeability TB of the protective film B satisfy the above-mentioned conditions (1) and (2). In addition, since the layer thickness of the protective film A is less than 50 μm, no cracks occur on the surface of the hard coating layer even when it is wound on a mandrel with a diameter of 2 mm, and the bending resistance is excellent. In addition, since the protective film A has a hard coating layer, the surface hardness is also superior to that of Comparative Examples 12 and 13 which do not have a hard coating layer.

In contrast, in Comparative Example 1, since the layer thickness of the protective film A is 50 μm, cracks occur on the surface of the hard coating layer when it is wound around a mandrel with a diameter of 2 mm, and the bending resistance of the protective film A is worse than that of the embodiment.

The polarizing plate of Comparative Example 2 cannot fully suppress the intrusion of moisture from the outside due to the high moisture permeability TA of the protective film A. After being placed in a constant temperature chamber at 85°C and 85%RH for 500 hours, the polarization degree is lower than that of the embodiment.

The polarizing plates of Comparative Examples 3 to 6 have insufficient bending resistance due to the small amount of constituent units derived from (meth)acrylate having an alicyclic structure in the hard coating layer of the protective film A. The bending resistance of the protective film A is inferior to that of the examples. Moreover, the protective film A of Comparative Example 2, which has a hard coating layer formed with the same composition as that of Comparative Examples 3 to 6, exhibits the same bending resistance as that of the examples. This is considered to be because the thickness of the protective film A of Comparative Example 2 is relatively thin, which suppresses stress concentration on the surface of the hard coating layer.

The polarizing plates of Comparative Examples 7 to 9 cannot fully inhibit the intrusion of moisture from the outside due to the high moisture permeability TA of the protective film A, and the polarization degree after being placed in a constant temperature chamber at 85°C and 85%RH for 500 hours is lower than that of the examples. In addition, the polarizing plates of Comparative Examples 8 and 9 do not fully exhibit the bending resistance because the hard coating layer of the protective film A does not contain a constituent unit derived from (meth)acrylate having an alicyclic structure, and the bending resistance of the protective film A is worse than that of the examples. Furthermore, the protective film A of Comparative Example 7 having a hard coating layer formed with the same composition as Comparative Examples 8 and 9 exhibits the same bending resistance as that of the embodiment. This is considered to be because the layer thickness of the protective film A of Comparative Example 7 is relatively thin, which suppresses stress concentration on the surface of the hard coating layer.

The polarizing plates of Comparative Examples 10 and 11 do not have sufficient bending resistance because the hard coating layer of the protective film A does not contain a constituent unit derived from (meth)acrylate having an alicyclic structure. The bending resistance of the protective film A is inferior to that of the embodiment.

The polarizing plates of Comparative Examples 12 and 13 were placed in a constant temperature chamber at 85°C and 85%RH for 500 hours, and the polarization degree was lower than that of the example. This is believed to be because the moisture permeability TA of the protective film A is too low, so when exposed to high temperature and high humidity, the moisture contained in the protective film A and/or the adhesive (water paste) continues to remain in the polarizing plate, resulting in the degradation of the polarizer. In addition, since the protective film A of Comparative Examples 12 and 13 is not provided with a hard coating layer, the surface hardness is worse than that of the example. [Possibility of industrial use]

The present invention can be used as a polarizing plate for a display device, and is particularly suitable as a polarizing plate for a display device used in a high temperature environment such as for vehicle-mounted use.

1: Polarizer 2: TAC film 3: Hard coating 10: Polarizer A: Protective film A B: Protective film B

FIG. 1 is a cross-sectional view showing a schematic structure of a polarizing plate of an embodiment.

1: Polarized filter

2:TAC film

3: Hard coating

10: Polarizing plate

A: Protective film A

B: Protective film B

Claims (5)

A polarizing plate having a protective film A attached to one side of a polarizing lens and a protective film B attached to the other side, wherein: The moisture permeability TA of the protective film A and the moisture permeability TB of the protective film B at 90% RH satisfy the following conditions (1) and (2) at the same time; the protective film A has a hard coating layer, the hard coating layer is formed by a cured film of a composition containing a photopolymerizable compound and a photopolymerization initiator, the photopolymerizable compound contains a (meth)acrylate compound containing an alicyclic structure, and the content ratio of the (meth)acrylate compound containing an alicyclic structure in the composition is 20 mass % or more of the photopolymerizable compound, the thickness of the protective film A is less than 50 μm, the (meth)acrylate compound containing an alicyclic structure is a monofunctional acrylate compound, 240 g/m ² /day>TA>70 g/m ² /day‧‧‧(1) 70 g/m ² /day≧TB‧‧‧(2). As in the polarizing plate of claim 1, the protective film A is a hard coating film in which the hard coating layer is laminated on one surface of a triacetyl cellulose film. As in claim 2, the polarizing plate, wherein the pencil hardness of the hard coating film is 3H or above. As in claim 1, the polarizing plate, wherein the protective film B is a film made of any one of cycloolefin polymer, polyethylene terephthalate and polymethyl methacrylate. A display device comprising a polarizing plate as described in any one of claims 1 to 4.