Polarizer and display device using the same

Abstract

To provide a polarizer with durability even in high temperature and humidity environments, and a display device using the same.SOLUTION: The polarizer includes: a protective film A applied over one side of a polarizing element; and a protective film B applied over the other side thereof. The protective film A is a hard coat film in which a hard coat layer is formed over one side of a transparent substrate. 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 satisfy the following conditions (1) and (2) simultaneously. Defining the peak intensity at 1782-1683 cm-1 measured by the ATR method using a germanium prism is P1, and the peak intensity between 1427 and 1374 cm-1 is P2, the polarizer satisfies the following condition (3). 240 g / m2 / day>TA>70 g / m2 / day...(1), 70 g / m2 / day≥TB...(2), and 0.060≤P2 / P1≤0.150...(3).SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a polarizing plate and a display device using the same. [Background technology]

[0002] Polyvinyl alcohol (PVA) is mainly used for polarizing plates used in display devices. Since PVA has extremely poor water resistance, protective films are attached to both sides of the PVA. Conventionally, the protective film for polarizing plates has been a triacetyl cellulose (TAC) film with a hard coat layer laminated thereon, with a moisture permeability of 300 to 1000 g / m 2 / day has been used, but under harsh conditions of high temperature and humidity, the PVA cannot completely prevent water absorption, causing degradation.

[0003] Therefore, instead of TAC, protective films using cycloolefin polymer (COP) or polyethylene terephthalate (PET) have been developed, and the moisture permeability of the protective films is 5 to 100 g / m 2 / day. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2021-144076 A Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, polarizing plates that are durable under extremely high temperature and humidity conditions are required for in-vehicle applications, etc. In high-temperature and humid environments, if the water vapor barrier property of a protective film is too high, moisture will not penetrate from the outside, but there have been cases where moisture generated from the substrate or the adhesive used to attach the protective film remains in the polarizing plate and causes degradation.

[0006] Therefore, an object of the present invention is to provide a polarizing plate having durability in a high-temperature and high-humidity environment, and a display device using the same. [Means for solving the problem]

[0007] The polarizing plate according to the present invention is a polarizing plate in which a protective film A is bonded to one surface of a polarizer and a protective film B is bonded to the other surface of the polarizer, the protective film A being a hard coat film having a hard coat layer formed on one surface of a transparent substrate, 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), and have a moisture permeability of 1782 to 1683 cm as measured by the ATR method using a germanium prism. -1 The peak intensity of P1 is 1427-1374 cm -1 When the peak intensity is P2, the following condition (3) is satisfied. 240g / m 2 / day>TA>70g / m 2 / day ···(1) 70g / m 2 / day≧TB (2) 0.060≦P2 / P1≦0.150 (3)

[0008] A display device according to the present invention includes the above polarizing plate. Effect of the Invention

[0009] According to the present invention, it is possible to provide a polarizing plate having durability in a high-temperature and high-humidity environment and a display device using the same. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view showing a schematic configuration of a polarizing plate according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] FIG. 1 is a cross-sectional view showing a schematic configuration of a polarizing plate according to an embodiment of the present invention.

[0012] 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 adsorbing iodine or a dye to a polyvinyl alcohol (PVA) film and orienting it. Since the PVA constituting the polarizer 1 is poor in strength and water resistance, protective films A and B are attached to both sides of the polarizer 1.

[0013] The protective film A is a hard coat film in which a hard coat layer 3 is formed on one surface of a transparent substrate 2. The hard coat layer 3 is a functional layer that covers the flexible transparent substrate 2 and imparts hardness and water vapor barrier properties to the protective film A. As the transparent substrate 2, a triacetyl cellulose (TAC) film having excellent transparency can be suitably used.

[0014] The protective film A can be formed by applying a composition for forming a hard coat layer, which contains an active energy ray-curable compound, a hydrophobic material, a photopolymerization initiator, and a solvent, to one side of the transparent substrate 2, drying the composition, and curing the coating by irradiating with ultraviolet light.

[0015] As the active energy ray curable compound, for example, a monofunctional, bifunctional, trifunctional or higher functional (meth)acrylate monomer can be used. In this specification, "(meth)acrylate" is a general term for both acrylate and methacrylate, and "(meth)acryloyl" is a general term for both acryloyl and methacryloyl.

[0016] Examples of monofunctional (meth)acrylate compounds include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, glycidyl (meth)acrylate, acryloylmorpholine, N-vinylpyrrolidone, tetrahydrofurfuryl acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isobornyl (meth)acrylate. acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, benzyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, ethyl carbitol (meth)acrylate, phosphate (meth)acrylate, ethylene oxide modified phosphate (meth)acrylate, phenoxy (meth)acrylate, ethylene oxide modified phenoxy (meth)acrylate, propylene oxide Side-modified phenoxy (meth)acrylate, b-phenol (meth)acrylate, ethylene oxide-modified nonylphenol (meth)acrylate, propylene oxide-modified nonylphenol (meth)acrylate, methoxydiethylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, methoxypropylene glycol (meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, ) acryloyloxyethyl hydrogen phthalate, 2-(meth)acryloyloxypropyl hydrogen phthalate, 2-(meth)acryloyloxypropyl hexahydrohydrogen phthalate, 2-(meth)acryloyloxypropyl tetrahydrohydrogen phthalate, dimethylaminoethyl (meth)acrylate, trifluoroethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropropyl (meth)acrylate, 2-adamantane,Examples of the mono(meth)acrylate include adamantane derivative mono(meth)acrylates such as adamantyl acrylate having a monovalent mono(meth)acrylate derived from an adamantanediol.

[0017] 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, di(meth)acrylates such as di(meth)acrylate, ethoxylated neopentyl glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, and hydroxypivalic acid neopentyl glycol di(meth)acrylate.

[0018] Examples of trifunctional or higher (meth)acrylates include tri(meth)acrylates such as trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, tris(2-hydroxyethyl)isocyanurate tri(meth)acrylate, and glycerin tri(meth)acrylate, trifunctional (meth)acrylate compounds such as pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, and ditrimethylolpropane tri(meth)acrylate. Examples of the polyfunctional (meth)acrylate compound include trifunctional or higher polyfunctional (meth)acrylate compounds such as pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, ditrimethylolpropane penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and ditrimethylolpropane hexa(meth)acrylate, as well as polyfunctional (meth)acrylate compounds in which a portion of these (meth)acrylates is substituted with an alkyl group or ε-caprolactone.

[0019] In addition, as the polyfunctional monomer, a urethane (meth)acrylate can also be used. Examples of the urethane (meth)acrylate include those obtained by reacting a polyester polyol with an isocyanate monomer or a prepolymer, and then reacting the resulting product with a (meth)acrylate monomer having a hydroxyl group.

[0020] 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, dipentaerythritol pentaacrylate isophorone diisocyanate urethane prepolymer, and the like.

[0021] The above-mentioned polyfunctional monomers may be used alone or in combination of two or more. In addition, the above-mentioned polyfunctional monomers may be monomers in the composition, or may be partially polymerized oligomers.

[0022] The hydrophobic material is a component for imparting hydrophobicity to the hard coat layer 3 and adjusting the moisture permeability of the protective film A. As the hydrophobic material contained in the hard coat layer 3, a cycloolefin polymer or a (meth)acrylate containing an alicyclic structure can be used.

[0023] As the (meth)acrylate containing an alicyclic structure, for example, a (meth)acrylate having one or more of a cyclopentane structure, a dicyclopentane structure, a cyclohexane structure, a cyclodecane structure, a tricyclodecane structure, an isobornyl structure, and an adamantane structure can be used.

[0024] Specific examples of (meth)acrylates 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, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentadienyl (meth)acrylate. monofunctional (meth)acrylates such as cyclohexanedimethanol di(meth)acrylate, dicyclopentanyl di(meth)acrylate, dicyclopentanyloxyethyl methacrylate, bornyl (meth)acrylate, isobornyl (meth)acrylate, tricyclodecanyl (meth)acrylate, tricyclodecane dimethanol mono(meth)acrylate, and adamantyl (meth)acrylate; Thenyl di(meth)acrylate, dicyclopentadienyl di(meth)acrylate, bornyl di(meth)acrylate, isobornyl di(meth)acrylate, tricyclodecanyl di(meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, adamantyl di(meth)acrylate, adamantane dimethanol di(meth)acrylate, adamantane diethanol di(meth)acrylate, dimethylol dicyclopentane di(meth)acrylate, norborna Examples of the polyfunctional (meth)acrylate include polyfunctional (meth)acrylates such as norbornane trimethylol tri(meth)acrylate, tricyclodecane trimethanol tri(meth)acrylate, perhydro-1,4,5,8-dimethanonaphthalene-2,3,7-(oxymethyl)tri(meth)acrylate, etc. These (meth)acrylates may be used alone or in combination of two or more.

[0025] As the photopolymerization initiator, radical polymerization initiators such as acetophenone, benzophenone, thioxanthone, benzoin, benzoin methyl ether, and acylphosphine oxide can be used. As the polymerization initiator, for example, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 2,2-diethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-phenylacetophenone, dibenzoyl, benzoin, benzoin methyl ether, benzoin ethyl ether, p-chlorobenzophenone, p-methoxybenzophenone, Michler's ketone, acetophenone, and 2-chlorothioxanthone can be used. One of these may be used alone, or two or more may be used in combination.

[0026] As the solvent, one or more of the following can be used in combination: alcohols such as methanol, ethanol, 1-propanol, 2-propanol, butanol, isopropyl alcohol, 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 cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, diethyl cellosolve, 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.

[0027] In addition, various additives such as an antistatic agent, an antifoaming agent, an antioxidant, an ultraviolet absorber, an infrared absorber, a colorant, a light stabilizer, a polymerization inhibitor, a photosensitizer, an antifouling agent, a leveling agent, an oil repellent, a water repellent, and a fingerprint prevention agent may be added to the composition for forming a hard coat layer as necessary.

[0028] The method for applying the composition for forming a hard coat layer is not particularly limited, and for example, the composition can be applied using a spin coater, a roll coater, a reverse roll coater, a gravure coater, a microgravure coater, a knife coater, a bar coater, a wire bar coater, a die coater, a dip coater, a spray coater, an applicator, or the like.

[0029] The coating thickness of the composition for forming a hard coat layer (film thickness of the coating film) is preferably 10 μm or less, more preferably 8 μm or less. If the coating thickness of the composition for forming a hard coat layer exceeds 10 μm, curling is likely to occur due to shrinkage during curing, which is not preferable.

[0030] The protective film A (hard coat film) preferably has a pencil hardness of at least 3H. When the protective film A has a pencil hardness of at least 3H, the polarizing plate has excellent surface hardness and improved durability.

[0031] 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 polarizer 1 via, for example, an ultraviolet-curable adhesive. The thickness of the protective film B is not particularly limited, but is preferably 10 to 100 μm.

[0032] In the display device, protective film B is disposed on the display panel side, and hard coat layer 3 of protective film A is disposed on the viewing side (the side opposite to the display panel).

[0033] The transparent substrate 2 of the protective film A is bonded to the PVA film of the polarizer 1 using a water-based adhesive (aqueous PVA solution). In order to ensure adhesion between the transparent substrate 2 and the PVA film, the protective film A is subjected to a saponification treatment before bonding. Since a water-based adhesive is used to bond the protective film A to the polarizer 1, moisture may be contained in the adhesive layer and the TAC film even after a drying process. When both the protective films A and B are made of a film with low moisture permeability, the intrusion of moisture from the outside is suppressed, but in an extremely high-temperature environment such as the inside of a car in summer, moisture contained in the adhesive and / or the transparent substrate 2 continues to remain in the polarizing plate 10, causing deterioration of the polarizer 1.

[0034] Therefore, in the polarizing plate 10 of this embodiment, a difference is provided between the moisture permeability of protective film A and the moisture permeability of protective film B, and the moisture permeability of protective film A and protective film B are each set to a specific range, thereby suppressing deterioration of the polarizer 1 due to moisture derived from the adhesive and / or TAC film.

[0035] Specifically, assuming that the moisture permeabilities of protective films A and B at 40°C and 90% RH are TA and TB, respectively, TA and TB simultaneously satisfy the following conditions (1) and (2). Note that both the moisture permeabilities TA and TB are values ​​measured in accordance with the moisture permeability test method (cup method) for moisture-proof packaging materials specified in JIS Z 0208:1976. 240g / m 2 / day>TA>70g / m 2 / day ···(1) 70g / m 2 / day≧TB (2)

[0036] The polarizing plate 10 of this embodiment simultaneously satisfies the above conditions (1) and (2), thereby suppressing the intrusion of moisture from the outside into the polarizing plate, while at the same time enabling moisture generated from the adhesive used to bond the protective film A and the polarizer 1 and / or the transparent substrate 2 of the protective film A to be expelled to the outside when exposed to a high-temperature environment, for example, at 85°C.

[0037] In addition, in the hard coat layer 3, a wavelength of 1782 to 1683 cm was measured using a germanium prism by the ATR method. -1 The peak intensity (peak height) of P1 is 1427-1374 cm -1 When the peak intensity is P2, P2 / P1 is defined as the degree of hardening. -1 The peak corresponds to the stretching vibration peak of the C=O bond constituting the (meth)acryloyl group of the (meth)acrylate compound, and is in the range of 1427 to 1374 cm -1 The strength corresponds to the peak of the stretching vibration of the C=C bond of the (meth)acryloyl group of the (meth)acrylate compound. When the value of the degree of curing P2 / P1 of the hard coat layer 3 decreases, the pencil hardness increases, and when the value of the degree of curing P2 / P1 increases, the pencil hardness decreases. In addition, when the value of the degree of curing P2 / P1 decreases, the moisture permeability decreases, and when the value of the degree of curing P2 / P1 increases, the moisture permeability tends to increase. Therefore, there is a range of the degree of curing P2 / P1 that can achieve both pencil hardness and moisture permeability, and specifically, it is preferable that the degree of curing P2 / P1 satisfies the following condition (3). 0.060≦P2 / P1≦0.150 (3)

[0038] If the degree of curing P2 / P1 is less than 0.060, the moisture permeability of protective film A becomes too low, which may make it impossible to satisfy the above condition (1), and in this case, moisture generated from the transparent substrate 2 of protective film A cannot be discharged to the outside. If the degree of curing P2 / P1 exceeds 0.150, the pencil hardness of protective film A deteriorates. In addition, the moisture permeability becomes too high, which may make it impossible to satisfy the above condition (1), and in this case, it becomes difficult to suppress the intrusion of moisture from the outside into the polarizing plate.

[0039] As described above, the polarizing plate 10 according to this embodiment includes protective film A and protective film B that satisfy the above conditions (1) to (3). With this configuration, protective film B arranged on the display panel side almost completely blocks the ingress and egress of moisture. Meanwhile, protective film A arranged on the viewing side allows the release of moisture generated inside the polarizing plate 10 in an extremely high-temperature environment while suppressing the ingress of moisture into the polarizing plate 10 from the outside. Therefore, in the polarizing plate 10 according to this embodiment, when used in a high-temperature environment, moisture generated inside the polarizing plate 10 does not remain, thereby suppressing deterioration of the polarizer and enabling the optical performance of the polarizing plate 10 to be maintained for a longer period of time.

[0040] Furthermore, by having the degree of curing of the hard coat layer 3 of the protective film A satisfy the above condition (3), it is possible to impart high pencil hardness while controlling the moisture permeability of the protective film A within a preferred range. As a result, the low moisture permeability and surface hardness of the protective film A can be maintained for a long period of time, and the durability of the polarizing plate can be improved.

[0041] Therefore, according to this embodiment, it is possible to provide a polarizing plate 10 that has excellent durability in a high-temperature and high-humidity environment.

[0042] The polarizing plate 10 according to the present embodiment can be used to configure an image display device in combination with an image display panel such as a liquid crystal panel or an organic EL panel. The image display device may include a touch panel. The polarizing plate 10 according to the present embodiment has excellent durability in a high-temperature and high-humidity environment, and therefore can be suitably used as an image display device to be installed in an environment such as the inside of a vehicle where temperatures and humidity are extremely high. EXAMPLES

[0043] Examples of the present invention will now be described in detail.

[0044] A composition for forming a hard coat layer was prepared containing a main material (polymerizable material), a hydrophobic material, a photopolymerization initiator, and a solvent in the ratio shown in Table 1. Note that Irgacure (registered trademark) 184 shown in Table 1 is 1-hydroxycyclohexyl phenyl ketone.

[0045] The prepared composition for forming a hard coat layer was applied to a 40 μm-thick TAC film (product name: TJ40, manufactured by Fujifilm Corporation) using a wire bar coater to a coating thickness as shown in Table 2. The coating film was dried by heating in an oven at 60° C. for 1 minute, and then cured by irradiating ultraviolet rays in a nitrogen atmosphere (oxygen concentration 500 ppm or less) in a UV curing device to produce protective films A (hard coat films) according to Examples 1 to 6 and Comparative Examples 1 to 7. In Comparative Examples 6 and 7, a polymethyl methacrylate (PMMA) film having a thickness of 60 μm and a cycloolefin polymer (COP) film having a thickness of 26 μm were used as protective film A. A COP film having a thickness of 26 μm was also used as protective film B.

[0046] [Table 1]

[0047] The TAC film surface of the protective film A was attached to the polarizer using water paste and dried, and then the protective film B was attached to the polarizer using a UV-curable adhesive, and the UV-curable adhesive was cured by irradiating with UV rays to obtain a polarizing plate. In Comparative Example 5, the protective film A was used as the protective film B.

[0048] (moisture permeability) The moisture permeability TA of protective film A and the moisture permeability TB of protective film B before being laminated to the polarizer were measured under conditions of 40°C and 90 RH% in accordance with the moisture permeability test method for moisture-proof packaging materials (cup method) specified in JIS Z 0208:1976.

[0049] (hardening degree) The hard coat layer of protective film A was subjected to FT-IR analysis by the ATR method. -1 Peak height P1, 1427-1374 cm -1 The peak height P2 of the cured product was measured, and the degree of cure P2 / P1 was calculated. In this experiment, an FT / IR-610 infrared spectrometer manufactured by JASCO Corporation was used, and a germanium prism was used as the prism.

[0050] (Pencil hardness) A scratch test was performed on the hard coat layer surface of protective film A using a pencil (uni, 3H, manufactured by Mitsubishi Pencil Co., Ltd.) and a Clemens scratch tester (HA-301, manufactured by Tester Sangyo Co., Ltd.) under conditions of a load of 500 g and a scratch speed of 0.5 mm / sec. The scratch test was performed on five samples, and samples in which scratches were found on the hard coat layer surface of two or more samples were rated as NG, and all other samples were rated as OK.

[0051] (Polarization degree of polarizing plate after high temperature and high humidity durability test) The polarizing plates according to each of the Examples and Comparative Examples were placed in a thermostatic 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 performing luminosity correction using a 2-degree visual field (C light source) according to JIS Z 8701 for a value measured using an absorptiometer with an integrating sphere (V7100, manufactured by JASCO Corporation).

[0052] Table 2 shows the characteristics of the protective films A and B according to each of the examples and comparative examples, 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).

[0053] [Table 2]

[0054] In the polarizing plates according to Examples 1 to 6, the moisture permeability TA of protective film A and the moisture permeability TB of protective film B satisfy the above conditions (1) and (2), and further, the degree of hardness of the hard coat layer of protective film A satisfies the above condition (3). Therefore, even after being placed in a thermostatic chamber at 85°C and 85% RH for 500 hours, the polarizing plates showed high polarization degrees and good surface hardness.

[0055] In contrast, in Comparative Example 1, the degree of curing P2 / P1 exceeded the range of condition (3), and the pencil hardness of the surface of Protective Film A decreased, so that the surface hardness also decreased.

[0056] In Comparative Example 2, the moisture permeability TA of the protective film A was below the range of condition (1), and the moisture permeability TA of the protective film A was low. As a result, moisture continued to remain in the polarizing plate, and the polarization degree after being placed in a thermostatic chamber at 85°C and 85% RH for 500 hours was lower than that of the examples.

[0057] In Comparative Example 3, the moisture permeability TA of the protective film A exceeded the range of condition (1), and the moisture permeability TA of the protective film A increased. As a result, the intrusion of moisture from the outside could not be sufficiently suppressed, and the polarization degree after being placed in a thermostatic chamber at 85°C and 85% RH for 500 hours was worse than that of the Examples. In addition, the degree of curing P2 / P1 exceeded the range of condition (3), and therefore the pencil hardness of the surface of the protective film A decreased, and the surface hardness also decreased.

[0058] In Comparative Example 4, since the degree of curing P2 / P1 was below the range of condition (3), the pencil hardness of the surface of the protective film A was sufficient, but the moisture permeability TA of the protective film A was below the range of condition (1). As a result, moisture continued to remain in the polarizing plate, and the polarization degree after being placed in a thermostatic chamber at 85°C and 85% RH for 500 hours was lower than that of the Examples.

[0059] In Comparative Example 5, the moisture permeability TB of the protective film A exceeded the range of condition (2), and the moisture permeability TB of the protective film B was high. As a result, the intrusion of moisture from the outside could not be sufficiently suppressed, and the polarization degree after being placed in a thermostatic chamber at 85°C and 85% RH for 500 hours was lower than that of the Examples.

[0060] In Comparative Examples 6 and 7, a PMMA film and a COP film with extremely low moisture permeability TA were used as the protective film A, respectively, but the polarization degree deteriorated after being placed in a thermostatic chamber at 85°C and 85% RH for 500 hours. This is thought to be because the moisture permeability TA of the protective film A was too low, and when exposed to high temperature and high humidity, the moisture contained in the protective film A and / or the adhesive (water glue) continued to remain in the polarizing plate, causing deterioration of the polarizer. In addition, the protective films A in Comparative Examples 6 and 7 did not have a hard coat layer, and therefore had inferior surface hardness compared to the Examples. [Industrial Applicability]

[0061] The present invention can be used as a polarizing plate for use in a display device, and is particularly suitable as a polarizing plate for a display device used in a high-temperature environment, such as for in-vehicle use. [Explanation of symbols]

[0062] A Protective Film A B. Protective film B 1 Polarizer 2 Transparent base material 3 Hard coat layer 10 Polarizing plate

Claims

1. A polarizing plate in which a protective film A is bonded to one surface of a polarizer and a protective film B is bonded to the other surface of the polarizer, The protective film A is a hard coat film having a hard coat layer formed on one surface of a transparent substrate, 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), 1782-1683 cm measured using a germanium prism by the ATR method －１ The peak intensity of P1 is 1427 to 1374 cm －１ A polarizing plate which satisfies the following condition (3), wherein P2 is a peak intensity of the polarizing plate. 240g / m ２ / day>TA>70g / m ２ / day ・・・(1) 70g / m ２ / day≧TB ・・・(2) 0.060≦P2 / P1≦0.150 ... (3)

2. The polarizing plate according to claim 1 , wherein the transparent substrate is a triacetyl cellulose film.

3. 2. The polarizing plate according to claim 1, wherein the protective film A has a pencil hardness of 3H or more.

4. 2. The polarizing plate according to claim 1, wherein the protective film B is a film made of one of a cycloolefin polymer, polyethylene terephthalate, and polymethyl methacrylate.

5. A display device comprising the polarizing plate according to any one of claims 1 to 4.

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