Polarizing plate and image display device comprising the same

Abstract

The present invention provides a polarizing plate and an image display device including the same, the polarizing plate including a polarizing sheet and a surface treatment film laminated on one surface of the polarizing sheet, wherein the surface treatment film includes a (meth)acrylic film as a base film, and the polarizing plate satisfies a certain mathematical formula. The polarizing plate according to the present invention can improve light leakage by controlling the bending property of a large panel without reverse curling.

Description

TECHNICAL FIELD

[0001] The present application relates to a polarizing plate and an image display device including the same, and more particularly, to a polarizing plate capable of improving light leakage by controlling the bending property of a large panel without reverse curling and an image display device including the same. BACKGROUND

[0002] Liquid crystal display devices (LCDs) are used for various purposes, such as notebook computers, mobile phones, and liquid crystal televisions, etc. The LCDs generally include a liquid crystal cell including liquid crystals, a polarizing plate, and an adhesive layer or a bonding agent layer for joining them.

[0003] In addition, the polarizing plate for a liquid crystal display is generally a polarizing sheet (also referred to as a "polarizing film") in which an iodine-based compound or a dichroic dye is adsorbed and aligned on a polyvinyl alcohol (PVA) resin film arranged in a predetermined direction. The polarizing plate has a multi-layer structure in which a protective film of a triacetyl cellulose (TAC) is laminated on at least one surface of the polarizing sheet through an adhesive layer.

[0004] Korean Patent Publication No. 10-2013-0137161 discloses a polarizing plate including an optical laminate having a hard coating layer on one side of a triacetyl cellulose substrate and a polarizing element.

[0005] However, the problem of the polarizing plate is that light leakage occurs due to a large amount of warping of the panel when a large panel is applied.

[0006] Therefore, it is necessary to develop a polarizing plate capable of improving light leakage by controlling the bending property of a large panel.

[0007] In addition, there is a need to develop a scheme for suppressing reverse curling of the polarizing plate to prevent the generation of air bubbles in the panel joining process. SUMMARY

[0008] Problems to be Solved

[0009] An object of the present application is to provide a polarizing plate capable of improving light leakage by controlling the bending property of a large panel without reverse curling.

[0010] Another object of the present application is to provide an image display device including the polarizing plate.

[0011] Method for Solving the Problem

[0012] On the other hand, the present application provides a polarizing plate including a polarizing sheet and a surface treatment film laminated on one surface of the polarizing sheet,

[0013] The surface treatment film includes a (meth)acrylic film as a base film, and

[0014] The polarizing plate satisfies the following mathematical formula 1.

[0015] [mathematical formula 1]

[0016] 70 ≤ a x b / c ≤ 300

[0017] In the mathematical formula,

[0018] a is the thickness of the base film (μm),

[0019] b is the tensile strength of the polarizing plate (Mpa),

[0020] c is the moisture permeability of the surface treatment film (g / m 2 / 24hr).

[0021] In one embodiment of the present application, the surface treatment film can include a base film on which a surface treatment layer is formed on at least one surface thereof.

[0022] In one embodiment of the present application, the thickness of the base film can be 60 μm or more.

[0023] The tensile strength of the polarizing plate according to one embodiment of the present application can be 90 Mpa to 150 Mpa.

[0024] In one embodiment of the present application, the moisture permeability of the surface treatment film can be 70 g / m 2 / 24hr or less.

[0025] In one embodiment of the present application, the thickness of the polarizing sheet can be 5 μm to 30 μm.

[0026] In one embodiment of the present application, the surface treatment layer can be a hard coat layer or an anti-glare coat layer.

[0027] The polarizing plate according to one embodiment of the present application can further include a retardation layer laminated on the other surface of the polarizing sheet.

[0028] In one embodiment of the present application, the retardation layer can have a planar direction retardation (R0) of 0 to 10 nm at a wavelength of 550 nm.

[0029] In the polarizing plate according to one embodiment of the present application, an adhesive layer can be further laminated on the opposite surface of the surface opposite to the polarizing sheet.

[0030] In the polarizing plate according to one embodiment of the present application, a peelable protective film can be further laminated on the opposite surface of the surface opposite to the polarizing sheet.

[0031] In the polarizing plate according to the embodiment of the present application, a release film can be further laminated on the opposite surface of the surface of the adhesive layer opposite to the phase difference layer.

[0032] In another aspect, the present application provides an image display device including the polarizing plate.

[0033] Effects of the Invention

[0034] The polarizing plate of the present application includes a (meth)acrylic film as a base film of a surface treatment film, and by satisfying a specific mathematical formula, light leakage can be improved by controlling the bending property even when a large-sized panel without reverse curling is applied. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figures 1 to 3 is a schematic cross-sectional view of a polarizing plate according to an embodiment of the present application. DETAILED DESCRIPTION

[0036] Hereinafter, the present application will be described in more detail.

[0037] The present application relates to a polarizing plate including a polarizing sheet and a surface treatment film laminated on one surface of the polarizing sheet,

[0038] The surface treatment film includes a (meth)acrylic film as a base film, and

[0039] The polarizing plate satisfies the following mathematical formula 1.

[0040] [mathematical formula 1]

[0041] 70 ≤ a x b / c ≤ 300

[0042] In the mathematical formula,

[0043] a is the thickness of the base film (μm),

[0044] b is the tensile strength of the polarizing plate (Mpa),

[0045] c is the moisture permeability of the surface treatment film (g / m 2 / 24hr).

[0046] Figure 1 is a structural cross-sectional view of a polarizing plate according to an embodiment of the present application.

[0047] Referring to Figure 1 , the polarizing plate according to an embodiment of the present application includes a polarizing sheet 110 and a surface treatment film 120 laminated on one surface of the polarizing sheet.

[0048] The surface treatment film 120 can include a base film 121 having a surface treatment layer 122 formed on at least one surface thereof.

[0049] The polarizing plate according to one embodiment of the present application includes a (meth)acrylic film as a base film of the surface treatment film, and by satisfying the mathematical formula 1, thereby improving light leakage by controlling the bending characteristics of a large panel without reverse curling. Accordingly, the polarizing plate according to one embodiment of the present application can be advantageously applied to an LCD or the like for a large television.

[0050] As described above, the polarizing plate according to one embodiment of the present application satisfies the following mathematical formula 1.

[0051] [mathematical formula 1]

[0052] 70 < a x b / c < 300

[0053] In the mathematical formula, a is the thickness of the base film (μm),

[0054] a is the thickness of the base film (μm),

[0055] b is the tensile strength of the polarizing plate (Mpa),

[0056] c is the moisture permeability of the surface treatment film (g / m 2 / 24hr).

[0057] In the polarizing plate according to one embodiment of the present application, if the value of a x b / c is less than 70, the amount of warping can increase when the panel is applied and light leakage can occur, and if the value is greater than 300, the polarizing plate can be reverse-curling and bubbles can be generated when the panel is bonded.

[0058] The surface treatment film uses a (meth)acrylic film as a base film.

[0059] The thickness of the base film can be 60 μm or more, and preferably 60 μm to 100 μm. If the thickness of the base film is less than 60 μm, it can be difficult to control the bending characteristics of a large panel, and if it exceeds 100 μm, the polarizing plate can be reverse-curling, the transparency can be reduced, or the weight of the polarizing plate can be increased.

[0060] The tensile strength of the polarizing plate according to one embodiment of the present application can be 85 Mpa to 150 Mpa.

[0061] The tensile strength is a force representing the strength of a material, and refers to a value obtained by dividing the maximum tensile load until the material is broken by the cross-sectional area of the material. The tensile strength can be obtained by measuring the polarizing plate according to the method described in the experimental example described later.

[0062] In one embodiment of the present application, if the tensile strength of the polarizing plate is less than 85 MPa, the shrinkage expansion rate of the polarizing plate can increase, so the amount of flexure can increase, and if it exceeds 150 MPa, the tensile strength is very high and the balance with the lower plate is broken, so the warpage can increase.

[0063] In one embodiment of the present application, the moisture permeability of the surface treatment film can be 70 g / m 2 / 24 hr or less.

[0064] The moisture permeability of the surface treatment film is a value measured using a moisture permeation cup for the surface treatment film according to the method described in the Experimental Example below.

[0065] When the moisture permeability of the surface treatment film exceeds 70 g / m 2 / 24 hr, it can be difficult to control the bending characteristics of a large panel.

[0066] Hereinafter, each component of the polarizing plate 100 will be described in detail.

[0067] In one embodiment of the present application, the polarizing sheet 110 is an optical film for converting incident natural light into a desired single polarized state (linearly polarized state), and is not particularly limited as long as it can perform the ordinary polarizing function in the art.

[0068] For example, the polarizing sheet 110 specifically includes a film in which a dichroic substance such as iodine or a dichromatic dye is adsorbed on a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formaldehyde-treated polyvinyl alcohol-based film, or an ethylene / vinyl acetate copolymer-based partially saponified film, and is uniaxially stretched, and a dehydrated product of a polyvinyl alcohol-based film, a dechlorinated product of a polyvinyl chloride-based film, and the like. Among them, from the viewpoint of high polarizing dichroism, a polarizing sheet in which a dichroic substance such as iodine is adsorbed on a polyvinyl alcohol-based film and is uniaxially stretched is particularly preferred.

[0069] The thickness of the polarizing sheet 110 is in the range of 5 μm to 30 μm, and is preferably 15 to 25 μm. If the thickness of the polarizing sheet 110 is less than 5 μm, the manufacturing process of the polarizing plate can be difficult to control, and the polarizing sheet can be broken or the axial uniformity of the polarizing sheet can be reduced, and if the thickness exceeds 30 μm, the shrinkage rate of the polarizing sheet after leaving heat or moisture resistance can increase, so the amount of warpage can increase.

[0070] A polarizing sheet prepared by adsorbing iodine on a polyvinyl alcohol-based film and performing uniaxial stretching, for example, can be manufactured by coloring a polyvinyl alcohol-based film by immersing the film in an aqueous iodine solution and stretching the film to 3 to 7 times the original length. The aqueous solution can include boric acid, zinc sulfate, zinc chloride, or the like as needed, or the polyvinyl alcohol-based film can be immersed in an aqueous solution of potassium iodide or the like. In addition, the polyvinyl alcohol-based film can be washed by immersion in water as needed before coloring. Washing of the polyvinyl alcohol-based film can not only remove contaminants or a release agent from the surface of the film, but also prevent unevenness such as uneven coloring by swelling the polyvinyl alcohol-based film. Stretching of the film can be performed after coloring the film with iodine, during coloring of the film, or before coloring the film with iodine. Stretching can be performed in an aqueous solution of boric acid or potassium iodide or in an aqueous solution.

[0071] Examples of commercially available polarizing sheets include VF-PS7500, VF-PE6000, VF-PE5000, VF-PE4500, VF-PE3000, VF-PE2000 (Kuraray), M-7500 (Nippon Gosei), and the like.

[0072] As the base film 121 of the surface-treated film 120, a (meth)acrylic film is used as described above.

[0073] The (meth)acrylic film includes, for example, poly(methyl) methacrylate, poly(ethyl) methacrylate, or the like, and in particular, poly(methyl) methacrylate is preferable in view of controlling the amount of warpage.

[0074] In one embodiment of the present application, the surface-treated layer 122 can be formed by applying an appropriate surface treatment coating composition to the base film 121 and curing it. The surface-treated layer 122 can be a hard coat layer or an antiglare coat layer, or the like.

[0075] For example, the surface treatment coating composition can be a composition for forming an antiglare layer or a hard coat layer composition, and can include a light-transmissive resin, light-transmissive particles, a photopolymerization initiator, and a solvent.

[0076] The light-transmissive resin is a photocurable resin, and the photocurable resin can include a photocurable (meth)acrylate oligomer and / or a monomer. As the photocurable (meth)acrylate oligomer, an epoxy (meth)acrylate, a urethane (meth)acrylate, or the like is generally used, and a urethane (meth)acrylate is preferable. A generally used monomer can be used without limitation, and a monomer having an unsaturated group such as a (meth)acryloyl group, a vinyl group, a styryl group, an allyl group, or the like in the molecule is preferable as a photocurable functional group, and a monomer having a (meth)acryloyl group is preferable.

[0077] The light-transmissive particles are used in the art and can be used without particular limitation, as long as they are particles capable of imparting surface treatment properties. The light-transmissive particles can be, for example, silica particles, silicone particles, melamine-based resin particles, acrylic resin particles, styrene-based resin particles, acrylic-styrene-based resin particles, polycarbonate-based resin particles, polyvinyl-based resin particles, chlorovinyl-based resin particles, and the like. Each of the above exemplified light-transmissive particles can be used alone or in combination of two or more. The average particle diameter of the translucent particles is preferably 1 to 10 μm. When the average particle diameter of the light-transmissive particles is less than 1 μm, it is difficult to form unevenness on the surface of the surface treatment layer 122, and the surface treatment properties are reduced, and when the average particle diameter is more than 10 μm, the surface of the surface treatment layer 122 is roughened, and there is a disadvantage in that the visibility is deteriorated.

[0078] As the photopolymerization initiator, those used in the art can be used without limitation. Specifically, as the photopolymerization initiator, at least one selected from the group consisting of 2-methyl-l-[4-(methylthio)phenyl]-2-morpholinopropanone, benzophenone benzyl dimethyl ketal, 2-hydroxy-2-methyl-l-phenyl-l-ketone, 4-hydroxycyclohexyl phenyl ketone, dimethoxy-2-phenylphenylethanone, anthraquinone, fluorene, triphenylamine, carbazole, 3-methylacetophenone, 4-acetophenone, 4,4-dimethoxyacetophenone, 4,4-diaminobenzophenone, 1-hydroxycyclohexyl phenyl ketone, and benzophenone can be used.

[0079] As the solvent, those known in the art can be used without limitation. For example, as the solvent, it is preferable to use: alcohol-based (methanol, ethanol, isopropanol, butanol, methyl cellulose, ethyl cellosolve, 1-methoxy-2-propanol, propylene glycol monomethyl ether, and the like), ketone-based (methyl ethyl ketone, butanone, methyl isobutyl ketone, diethyl ketone, diacetyl, cyclohexanone, and the like), hexane-based (hexane, heptane, octane, and the like), benzene-based (benzene, toluene, xylene, and the like). Each of the above exemplified solvents can be used alone or in combination of two or more.

[0080] In addition to the above components, the surface treatment coating composition includes components generally used in the art, such as an antioxidant, an ultraviolet absorber, a light stabilizer, a heat resistance polymerization inhibitor, a leveling agent, a surfactant, a lubricant, a stain preventing agent, and the like.

[0081] The surface treatment layer 122 can be formed by applying the surface treatment coating composition to one surface of the base film 121, drying it, and then UV-curing.

[0082] The coating process of the coating composition for surface treatment can be performed using a known method such as die coater, air knife, reverse roll, spraying, doctor blade, casting, gravure printing, microgravure printing, spin coating, and the like, as appropriate.

[0083] After the surface treatment coating composition is applied to the surface, the volatile matter is evaporated and dried at a temperature of 30 to 150°C for 10 seconds to 1 hour (more specifically, 30 seconds to 30 minutes), and then cured by irradiation with UV light. The amount of irradiation with UV light can be specifically about 0.01 to 10 J / cm 2 and more specifically 0.1 to 2 J / cm 2 In this case, the thickness of the surface treatment layer formed can be specifically 1 to 30 μm, and more specifically 1.5 to 10 μm.

[0084] The polarizing plate 110 can be joined to the surface treatment film 120 on one surface with an adhesive layer (not shown) interposed therebetween.

[0085] The adhesive layer can be formed of a water-based adhesive in which an adhesive component is dissolved or dispersed in water, a composition that is cured by receiving irradiation of active energy rays (hereinafter can be referred to as an active energy ray-curable adhesive), or the like.

[0086] As the water-based adhesive, components include polyvinyl alcohol-based resins or polyurethane resins, and in order to improve adhesion, a composition containing a crosslinking agent such as an isocyanate-based compound, an epoxy compound, or a curable compound, or the like can be cited.

[0087] When the main component of the adhesive is a polyvinyl alcohol-based resin, the polyvinyl alcohol-based resin includes partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, carboxyl-modified polyvinyl alcohol, acetyl acetyl-modified polyvinyl alcohol, methylol-modified polyvinyl alcohol, amino-modified polyvinyl alcohol, and the like. The concentration of the polyvinyl alcohol-based resin in the adhesive, based on 100 parts by weight of water, is usually 1 to 10 parts by weight, and preferably 1 to 5 parts by weight.

[0088] In order to improve adhesion, the adhesive containing a polyvinyl alcohol-based resin aqueous solution can also contain a curable compound such as a polyvalent aldehyde, a water-soluble epoxy resin, a melamine-based compound, a zirconium oxide-based compound, or a zinc compound, or the like.

[0089] As the water-soluble epoxy resin, for example, a water-soluble polyamide epoxy resin obtained by reacting a polyamide polyamine obtained by reacting a polyalkylene polyamine such as diethylenetriamine or triethylenetetramine with a dicarboxylic acid such as adipic acid with epichlorohydrin can be used. Examples of commercially available polyamide epoxy resins include "Sumirez Resin 650" and "Sumirez Resin 675" (Sumika Chemtex Corporation) and "WS-525" (Nippon PMC Corporation), and the like. The content of the water-soluble epoxy resin, based on 100 parts by weight of the polyvinyl alcohol-based resin, is usually 1 to 100 parts by weight, and preferably 1 to 50 parts by weight.

[0090] When the main component of the adhesive is a polyurethane resin, a polyester-based ionomer type polyurethane resin is preferably used as the polyurethane resin. The polyester-based ionomer type polyurethane resin is a polyurethane resin having a polyester skeleton in which an ionic component (hydrophilic component) is introduced. The ionomer type polyurethane resin is emulsified in water to form an emulsion even without using an emulsifier. The water-based adhesive containing the polyester-based ionomer type polyurethane resin preferably contains a water-soluble epoxy compound as a cross-linking agent.

[0091] When the polarizing sheet 110 and the surface treatment film 120 are bonded using a water-based adhesive, the water-based adhesive is injected between the polarizing sheet 110 and the surface treatment film 120, and sufficient adhesion can be provided to both by performing a thermal cross-linking reaction while drying and evaporating water.

[0092] The active energy ray-curable adhesive is cured by irradiation of an active energy ray. Examples of the active energy ray-curable adhesive include: a cationic polymerization active energy ray-curable adhesive containing an epoxy compound and a cationic polymerization initiator; a free radical polymerization active energy ray-curable adhesive containing an acrylic curing component and a free radical polymerization initiator; an active energy ray-curable adhesive containing a cationic polymerization curing component such as an epoxy compound and a free radical polymerization curing component such as an acrylic compound, and further containing a cationic polymerization initiator and a free radical polymerization initiator; and an electron beam-curable active energy ray-curable adhesive cured by irradiation of an electron beam, and the like. The electron beam-curable active energy ray-curable adhesive does not contain an initiator.

[0093] Among them, a cationic polymerization active energy ray-curable adhesive containing an epoxy compound and a cationic polymerization initiator is preferable. The active energy ray-curable adhesive is preferably substantially free of a solvent.

[0094] As the cationic polymerization epoxy compound, a substance that is itself liquid at room temperature, has moderate fluidity even in the absence of a solvent, and provides a suitable cured adhesive strength is selected. In addition, by selecting a cationic polymerization initiator suitable for the epoxy compound, the active energy ray-curable adhesive obtained can omit a drying device that is usually required in the bonding process. In addition, by irradiating an appropriate active energy dose, the curing speed can be accelerated, and thus the yield can be improved.

[0095] Examples of the epoxy compound include: a glycidyl ether product of an aromatic compound or a chain compound having a hydroxyl group; a glycidyl amine compound of a compound having an amino group; an epoxy compound of a chain compound having a C-C double bond; an alicyclic epoxy compound in which a glycidyl oxy group or an epoxy ethyl group is bonded to a saturated carbocyclic ring directly or through an alkylene group, or an epoxy group is bonded to a saturated carbocyclic ring directly. The epoxy compound can also be used in combination with other various kinds. Among them, from the aspect of excellent cationic polymerizability, an alicyclic epoxy compound is preferred.

[0096] The thickness of the adhesive layer can be appropriately determined depending on the type of the resin used as the adhesive, the adhesive strength, the environment in which the adhesive is used, and the like. The thickness of the adhesive layer is preferably from 0.01 μm to 50 μm, more preferably from 0.05 μm to 20 μm, and further preferably from 0.1 μm to 10 μm.

[0097] In the polarizing plate according to one embodiment of the present application, as shown in Figure 2 a phase difference layer 130 can be further laminated on the other surface of the polarizing sheet 110.

[0098] The phase difference layer 130 can be, for example, a stretched or unstretched polymer film, or a liquid crystal layer obtained by curing a reactive liquid crystal compound.

[0099] For example, when the phase difference layer 130 is manufactured from a liquid crystal layer, a reactive liquid crystal compound (RM) which is a liquid crystal compound having optical anisotropy and having cross-linkability by light or heat can be used.

[0100] The phase difference layer 130 can have a single layer structure or a multi-layer structure in which two or more layers are laminated. For example, the phase difference layer 130 can have a laminated structure of a positive C-plate layer, a combination of a positive C-plate layer and a negative B-plate layer, a combination of a positive uniaxial phase difference film and a positive C-plate layer, a combination of a negative biaxial phase difference film and a positive C-plate layer, and the like. At this time, each layer constituting the phase difference layer can be attached to each other by an adhesive or can be laminated to each other by direct coating.

[0101] The phase difference layer 130 can have a planar direction phase difference R0 of 0 to 10 nm at a wavelength of 550 nm. When the planar direction phase difference R0 of the phase difference layer at a wavelength of 550 nm is within the above range, a wide viewing angle and a color gamut can be improved.

[0102] The polarizing sheet 110 and the phase difference layer 130 can be joined using an adhesive.

[0103] The adhesive can be formed using various adhesives or adhesives known in the art, and the type thereof is not particularly limited.

[0104] For example, as the adhesive, for example, a rubber-based adhesive, an acrylic adhesive, a silicone-based adhesive, a urethane-based adhesive, a polyvinyl alcohol-based adhesive, a polyvinylpyrrolidone adhesive, a polyacrylamide adhesive, a cellulose adhesive, a vinyl alkyl ether adhesive, or the like can be used.

[0105] Further, the adhesive can be, for example, a photocurable adhesive, and the type thereof is not particularly limited.

[0106] The photocurable adhesive is cross-linked and cured by receiving active energy rays such as ultraviolet rays (UV), electron beams (EB), or the like to exhibit strong adhesion, and can be composed of a reactive oligomer, a reactive monomer, a photopolymerization initiator, or the like.

[0107] The reactive oligomer is an important component that determines the performance of the adhesive, forms a polymer bond by photopolymerization, and forms a cured film. Examples of the usable reactive oligomer include a polyester-based resin, a polyether-based resin, a polyurethane-based resin, an epoxy-based resin, a polyacrylic-based resin, and a silicone-based resin, or the like.

[0108] The reactive monomer is used as a cross-linking agent and a diluent for the above-described reactive oligomer, and affects the adhesion performance. Examples of the usable reactive monomer include a monofunctional monomer, a polyfunctional monomer, an epoxy-based monomer, a vinyl ether, a cyclic ether, or the like.

[0109] The photopolymerization initiator is used to initiate photopolymerization by generating radicals or cations by absorbing light energy, and can be used by selecting a suitable substance according to the photopolymerization resin.

[0110] As shown in FIG. 1, the adhesive layer 140 can be further laminated on the opposite surface of the surface of the phase difference layer 130 opposite to the polarizing plate 110. The adhesive layer 140 can be used to attach the polarizing plate 100 to an OLED panel or a touch panel. Figure 3 The adhesive layer 140 can be formed using various adhesives known in the art, and the type thereof is not particularly limited.

[0111] For example, as the adhesive, for example, a rubber-based adhesive, an acrylic adhesive, a silicone-based adhesive, a urethane-based adhesive, a polyvinyl alcohol-based adhesive, a polyvinylpyrrolidone adhesive, a polyacrylamide adhesive, a cellulose adhesive, a vinyl alkyl ether adhesive, or the like can be used.

[0112]

[0113] ​The thickness of the adhesive layer 140 is preferably 5 to 30 μm, but is preferably thinly coated within a range not impairing processability and durability, and is more preferably 10 to 25 μm. If the thickness of the adhesive layer 140 is less than 5 μm, defects can be recognized due to failure to fill in dents and damage in the panel, and if the thickness exceeds 30 μm, it can be difficult to achieve thinning of the polarizing plate.

[0114] In the polarizing plate according to one embodiment of the present application, a peelable protective film (not shown) can be further laminated on the opposite surface of the surface treatment film 120 opposite the polarizing sheet 110.

[0115] The peelable protective film includes a substrate and an adhesive layer formed on one surface of the substrate. The adhesive layer is attached to the surface treatment film 120, and when the polarizing plate is attached to a cover window, the adhesive layer is peeled from the surface treatment film 120, so that the protective film can be easily removed. As a material for the adhesive layer, the above-illustrated adhesive can be used.

[0116] As the substrate of the peelable protective film, for example, a polyester film such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, or the like; or a polyolefin film such as polypropylene, polyethylene, or the like can be cited.

[0117] The thickness of the peelable protective film can be 10 to 150 μm, and is preferably 25 to 130 μm. If the thickness of the peelable protective film is less than 10 μm, peeling of the protective film can not be easy, and if it exceeds 150 μm, adhesiveness to the surface treatment film 120 can be reduced.

[0118] Further, in the polarizing plate according to one embodiment of the present application, a peel-off film (not shown) can be further laminated on the opposite surface of the surface of the adhesive layer 140 opposite the phase difference layer.

[0119] The peel-off film is removed when the polarizing plate is attached to an OLED panel or a touch panel, or the like.

[0120] As the substrate of the peel-off film, for example, a polyester film such as polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, or the like; or a polyolefin film such as polypropylene, polyethylene, or the like can be cited.

[0121] The substrate surface of the peel-off film which is in contact with the adhesive layer 140 can be subjected to a mold release treatment. The mold release treatment can use a mold release agent such as a silicone-based mold release agent, a fluorine-based mold release agent, a long-chain alkyl graft polymer-based mold release agent, or the like, or a method of surface treatment by plasma treatment, or the like.

[0122] The thickness of the release film can be 10 to 150 μm, preferably 25 to 130 μm. When the thickness of the release film is less than 10 μm, peeling of the release film can not be easy, and when the thickness exceeds 150 μm, adhesion to the adhesive layer 140 can be reduced.

[0123] The total thickness of the polarizing plate according to one embodiment of the present application can be 130 to 220 μm, preferably 145 to 160 μm. At this time, the total thickness of the polarizing plate is the thickness excluding the thickness of the peelable protective film and the release film.

[0124] One embodiment of the present application relates to an image display device including the polarizing plate 100.

[0125] The image display device according to the embodiment of the present application can be applied not only to a general liquid crystal display device, but also to various image display devices such as an organic EL display device, a plasma display device, a field emission display device, and the like.

[0126] The image display device can include a configuration known in the art in addition to the polarizing plate.

[0127] Hereinafter, the present application will be described in more detail through examples and experimental examples. These examples and experimental examples are only for illustrating the present application, and it is obvious to those skilled in the art that the scope of the present application is not limited thereto.

[0128] Preparation Example 1: Preparation of an antiglare layer forming composition

[0129] An antiglare layer forming composition was prepared by mixing 14 wt% of a urethane acrylate (Miwon Corp., SC2153), 15 wt% of pentaerythritol triacrylate (Miwon Corp., M340), 1 wt% of light-transmitting particles (acrylic-styrene copolymer, refractive index 1.525, average particle diameter 2 μm), 67 wt% of ethyl acetate as a solvent, 2.5 wt% of a photoinitiator (Ciba Corp., I-184), and 0.5 wt% of a leveling agent (BYK Chemie Corp., BYK3550) using a stirrer and filtering using a PP filter.

[0130] Preparation Example 2: Preparation of a polarizing sheet

[0131] A transparent, unstretched polyvinyl alcohol film having a saponification degree of 99.9% or more and a thickness of 75 μm was controlled for moisture so that the moisture content was 4%. Thereafter, after first stretching by a heating roll stretching method at 120°C at a stretching ratio of 4.5 times, it was immersed in water (deionized water) at 50°C for 1 minute to swell. Then, it was immersed in an aqueous dyeing solution containing 5.0 mmol / L iodine and 4% by weight of potassium iodide at 30°C for 1 minute to perform dyeing. At this time, the stretching was 0.9 times and 1.1 times in the swelling and dyeing steps, respectively. Then, it was immersed in an aqueous crosslinking solution containing 10% by weight of potassium iodide and 7% by weight of boric acid at 70°C for 3 minutes to perform crosslinking. The stretching was 1.2 times in the crosslinking step. After completion of the crosslinking, the polyvinyl alcohol film was dried in an oven at 70°C for 4 minutes to produce a polarizing plate.

[0132] Preparation Examples 1 to 3 and Preparation Comparative Examples 1 to 6: Preparation of surface treatment film

[0133] After the antiglare layer-forming composition of Preparation Example 1 was applied on a base film to a thickness of 23 μm, the solvent was dried at 80°C for 2 minutes. The film was dried by UV irradiation at a cumulative light amount of 400 mJ / cm 2 to produce an antiglare film as a surface treatment film. As the base film, the films described in Table 1 below were used.

[0134] Examples 1 to 3 and Comparative Examples 1 to 6: Preparation of polarizing plate

[0135] A polarizing plate was produced in the same structure as in the Examples of Figure 1 by the following method.

[0136] The polarizing plate produced in Preparation Example 2 was bonded to the base film of the surface treatment film produced in the Preparation Examples and the Preparation Comparative Examples using an acrylic UV-curable adhesive. Thereafter, a polarizing plate was produced by irradiating UV at a cumulative light amount of 400 mJ / cm 2 .

[0137] Experimental Examples:

[0138] The physical properties of the surface treatment films produced in the Preparation Examples and the Preparation Comparative Examples and the polarizing plates produced in the Examples and the Comparative Examples were measured by the following methods, and the results are shown in Table 1 below.

[0139] (1) Moisture permeability of surface treatment film

[0140] The amount of water vapor (g, amount of change in weight of sample) through 1 m 2 area of each sample in an environment at 40°C and 90% relative humidity was measured according to the JIS Z 0208 moisture permeability test (cup method) of the surface treatment film produced in the Production Examples and the Production Comparative Examples.

[0141] (2) Tensile strength of the polarizing plate

[0142] The polarizing plates of the examples and the comparative examples were cut in the MD direction to have a long side of 5 mm in width, and the distance between the measurement points was set to 50 mm. Using a tensile strength measuring instrument (UTM autograph, Shimadzu Corporation, Model No. AG-X 1KN), the samples were measured at a measurement speed of 4 mm / min until the samples were broken, and the maximum value was evaluated as the tensile strength.

[0143] (3) Amount of flexure

[0144] The polarizing plates of the examples and the comparative examples were respectively laminated on both sides of a 320 mm x 180 mm x 0.7 mm glass, and then left to stand under a humidity resistance condition (60°C, relative humidity 90%) for 100 hours. At the time of lamination of the polarizing plate, an acrylic adhesive (Lintec Corporation) having a thickness of 15 μm was used as the adhesive layer.

[0145] The amount of warpage of the left sample was measured using Premium-600C manufactured by Inteck IMS Corporation.

[0146] (4) Curling of the polarizing plate

[0147] The polarizing plates of the examples and the comparative examples were cut in the MD direction to have a size of 700 x 300 mm, and left to stand on a flat plate, and the maximum height from the reference surface was measured.

[0148] At this time, the convex surface of the polarizing plate was brought into contact with the reference surface, and then the average of the heights from the reference surface to the four corners was measured, whereby the curling value could be obtained, and in the case of positive curling, the (+) value was used, and in the case of reverse curling, the (-) value was used. When the convex surface of the polarizing plate was brought into contact with the reference surface, the positive curling was the case where the surface treatment film was located above the polarizing sheet, and the reverse curling was the case where the surface treatment film was located below the polarizing sheet.

[0149]

Table 1

[0150]

[0151] PMMA: polymethyl methacrylate

[0152] TAC: triacetyl cellulose

[0153] a: base film thickness (μm)

[0154] b: tensile strength of the polarizing plate (Mpa)

[0155] c: moisture permeability of the surface treatment film (g / m 2 / 24hr)

[0156] As shown in Table 1, according to the present application, the polarizing plates of Examples 1 to 3 of the present application, which satisfy 70≤a×b / c≤300, have positive curling and a small amount of warpage, i.e., less than 1.3 mm, when the glass is applied.

[0157] On the other hand, the polarizing plates of Comparative Examples 1, 3 to 6, which have a value of a×b / c less than 70, have increased warpage, and the polarizing plate of Comparative Example 2, which has a value of a×b / c greater than 300, exhibits reverse curling.

[0158] Therefore, it can be seen that the polarizing plates of Examples 1 to 3 can improve light leakage by controlling the bending properties of large panels without reverse curling, as compared to the polarizing plates of Comparative Examples 1 to 6.

[0159] Since the above detailed description has been made for specific parts of the present application, it is apparent to those skilled in the art to which the present application pertains that the specific techniques are merely preferred embodiments, and the scope of the present application is not limited thereto. Those skilled in the art will be able to make various applications and modifications within the scope of the present application based on the above description.

[0160] Therefore, the substantial scope of the present application will be defined by the appended claims and their equivalents.

[0161] BRIEF DESCRIPTION OF DRAWINGS

[0162] 110: Polarizing sheet

[0163] 120: Surface treatment film

[0164] 121: Base film

[0165] 122: Surface treatment layer

[0166] 130: Phase difference layer

[0167] 140: Adhesive layer

Claims

1. A polarizing plate comprising a polarizer and a surface treatment film laminated on only one surface of the polarizer. in, The surface-treated film comprises a base film on at least one surface having a surface-treated layer formed thereon, and includes a (meth)acrylate film as the base film, the base film having a thickness of 60 μm to 100 μm, and the surface-treated film having a moisture permeability of 70 g / m³. 2 For periods of 24 hours or less, the tensile strength of the polarizing plate is 85 MPa to 150 MPa, and The polarizing plate satisfies the following mathematical formula 1: [Mathematical Expression 1] 70 ≤ a×b / c ≤ 300 In the mathematical expression, a is the thickness of the base film (μm). b represents the tensile strength (MPa) of the polarizing plate. c is the moisture permeability of the surface treatment film (g / m³). 2 / 24hr).

2. The polarizing plate according to claim 1, wherein, The thickness of the polarizer is 5 μm to 30 μm.

3. The polarizing plate according to claim 1, wherein, The surface treatment layer is a hard coating or an anti-glare coating.

4. The polarizing plate according to claim 1, wherein, Also includes: A phase retardation layer laminated on another surface of the polarizer.

5. The polarizing plate according to claim 4, wherein, The phase difference layer has a planar phase difference (R0) of 0 to 10 nm at a wavelength of 550 nm.

6. The polarizing plate according to claim 4, wherein, An adhesive layer is further laminated on the opposite side of the phase difference layer to the side opposite the polarizer.

7. The polarizing plate according to claim 1, wherein, A peelable protective film is further laminated on the opposite side of the surface-treated film to the side opposite the polarizer.

8. The polarizing plate according to claim 6, wherein, A release film is further laminated on the opposite side of the adhesive layer to the side opposite the phase difference layer.

9. An image display device comprising a polarizing plate according to any one of claims 1 to 7.

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