KR20220064654A - Polarizing Plate and Display Device Comprising the Same - Google Patents

Abstract

The present invention relates to a polarizing plate and an image display apparatus including the same, wherein the polarizing plate comprises a polarizer and a surface treated film stacked on one surface of the polarizer, and the surface treated film includes a (meta) acrylic film as a base film and satisfies a certain expression. The polarizing plate according to the present invention controls bending characteristics of a large panel without reverse curling to improve light leakage.

Description

Polarizing plate and image display device including same {Polarizing Plate and Display Device Comprising the Same}

The present invention 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 characteristics of a large panel without reverse curling, and to an image display device including the same.

Liquid crystal display device (LCD) is used for various purposes such as laptops, mobile phones, and liquid crystal TVs, and is generally used as a liquid crystal cell containing liquid crystal and a polarizing plate, and an adhesive layer or adhesive layer for bonding them. is composed

In addition, the polarizing plate used in the liquid crystal display is generally a polarizer in which an iodine-based compound or a dichroic dye is adsorbed and aligned on a polyvinyl alcohol (PVA) resin film arranged in a certain direction (also referred to as a 'polarizing film') Including, at least one surface of the polarizer has a multilayer structure in which a polarizer protective film represented by a triacetyl cellulose film (TAC) is laminated through an adhesive.

Korean Patent Laid-Open No. 10-2013-0137161 discloses a polarizing plate having an optical laminate having a hard coat layer on one side of a triacetyl cellulose substrate and a polarizing element.

However, when the polarizing plate is applied to a large panel, there is a problem in that light leakage occurs due to the large amount of bending of the panel.

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

In addition, there is a need to develop a method for suppressing the reverse curling of the polarizing plate so as to prevent the generation of air bubbles during panel bonding.

Republic of Korea Patent Publication No. 10-2013-0137161

One object of the present invention is to provide a polarizing plate capable of improving light leakage by controlling the bending characteristics of a large panel without reverse curling.

Another object of the present invention is to provide an image display device including the polarizing plate.

On the other hand, the present invention is a polarizing plate comprising a polarizer and a surface treatment film laminated on one surface of the polarizer,

The surface treatment film includes a (meth)acrylic film as a base film,

A polarizing plate satisfying Equation 1 below is provided.

[Equation 1]

70 ≤ a×b/c ≤ 300

In the above formula,

a is the thickness (㎛) of the base film,

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

c is the moisture permeability (g/m 2 /24hr) of the surface-treated film.

In one embodiment of the present invention, the surface treatment film may include a base film having a surface treatment layer formed on at least one surface.

In one embodiment of the present invention, the thickness of the base film may be 60㎛ or more.

The polarizing plate according to an embodiment of the present invention may have a tensile strength of 90Mpa to 150Mpa.

In one embodiment of the present invention, the moisture permeability of the surface-treated film may be 70 g/m 2 /24hr or less.

In one embodiment of the present invention, the thickness of the polarizer may be 5㎛ to 30㎛.

In one embodiment of the present invention, the surface treatment layer may be a hard coating layer or an anti-glare coating layer.

The polarizing plate according to an embodiment of the present invention may further include a retardation layer laminated on the other surface of the polarizer.

In an embodiment of the present invention, the retardation layer may have a plane-direction retardation (R ₀ ) of 0 to 10 nm at a wavelength of 550 nm.

In the polarizing plate according to an embodiment of the present invention, an adhesive layer may be further laminated on a surface opposite to the surface of the retardation layer opposite to the polarizer.

In the polarizing plate according to an embodiment of the present invention, a peelable protective film may be further laminated on the opposite surface of the surface-treated film opposite to the polarizer.

In the polarizing plate according to an embodiment of the present invention, a release film may be further laminated on the opposite surface of the surface opposite to the retardation layer of the pressure-sensitive adhesive layer.

On the other hand, the present invention provides an image display device including the polarizing plate.

The polarizing plate according to the present invention includes a (meth)acrylic film as a base film of the surface-treated film, and by satisfying a specific equation, it is possible to improve light leakage by controlling bending characteristics even when applying a large panel without reverse curling phenomenon.

1 to 3 are schematic cross-sectional views of a polarizing plate according to an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail.

The present invention is a polarizing plate comprising a polarizer and a surface-treated film laminated on one surface of the polarizer,

The surface treatment film includes a (meth)acrylic film as a base film,

It relates to a polarizing plate satisfying Equation 1 below.

[Equation 1]

70 ≤ a×b/c ≤ 300

In the above formula,

a is the thickness (㎛) of the base film,

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

c is the moisture permeability (g/m 2 /24hr) of the surface-treated film.

1 is a structural cross-sectional view of a polarizing plate according to an embodiment of the present invention.

Referring to FIG. 1 , a polarizing plate according to an embodiment of the present invention includes a polarizer 110 and a surface treatment film 120 laminated on one surface of the polarizer.

The surface treatment film 120 may include a base film 121 having a surface treatment layer 122 formed on at least one surface thereof.

The polarizing plate according to an embodiment of the present invention includes a (meth)acrylic film as a base film of the surface-treated film, and by satisfying Equation 1 above, controls the bending characteristics of a large panel without reverse curling to improve light leakage can do. Accordingly, the polarizing plate according to an embodiment of the present invention can be advantageously applied to LCDs for large TVs, and the like.

The polarizing plate according to an embodiment of the present invention satisfies the following Equation 1 as described above.

[Equation 1]

70 ≤ a×b/c ≤ 300

In the above formula,

a is the thickness (㎛) of the base film,

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

c is the moisture permeability (g/m 2 /24hr) of the surface-treated film.

In the polarizing plate according to an embodiment of the present invention, if the a×b/c value is less than 70, the amount of warpage may increase when the panel is applied and light leakage may occur. can

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

The thickness of the base film may be 60 μm or more, preferably 60 μm to 100 μm. If the thickness of the base film is less than 60 μm, it may be difficult to control the bending characteristics of the large panel, and if it exceeds 100 μm, the polarizing plate may be reverse curled, transparency may be reduced, or the weight of the polarizing plate may increase.

The polarizing plate according to an embodiment of the present invention may have a tensile strength of 85 Mpa to 150 Mpa.

The tensile strength is a force representing the strength of the 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 Experimental Examples to be described later.

In one embodiment of the present invention, if the tensile strength of the polarizing plate is less than 85Mpa, the amount of deflection may increase due to an increase in the shrinkage expansion rate of the polarizing plate, and if it exceeds 150Mpa, the tensile strength is very high, the balance with the lower plate is broken, and the bending may rather rise there is.

In one embodiment of the present invention, the moisture permeability of the surface-treated film may be 70 g/m 2 /24hr or less.

The moisture permeability of the surface-treated film is a value measured by using a moisture-permeable cup according to the method described in Experimental Examples to be described later for the surface-treated film.

When the moisture permeability of the surface-treated film exceeds 70 g/m 2 /24hr, it may be difficult to control the bending characteristics of the large panel.

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

In one embodiment of the present invention, the polarizer 110 is an optical film that serves to change incident natural light into a desired single polarization state (linear polarization state), and is particularly limited as long as it can perform a polarization function in general in the field don't do it

For example, the polarizer 110 is specifically iodine or dichroic on a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, or an ethylene/vinyl acetate copolymer-based partially saponified film. a film prepared by adsorbing a dichroic substance such as a sex dye and uniaxially stretching the film; and polyene-based oriented films such as dehydrated polyvinyl alcohol-based films or dechlorinated polyvinyl chloride-based films. Among them, a polarizer produced by adsorbing a dichroic substance such as iodine to a polyvinyl alcohol-based film and uniaxially stretching the film is particularly preferable from the viewpoint of high polarization dichroism.

The thickness of the polarizer 110 is in the range of 5 μm to 30 μm, preferably 15 to 25 μm. If the thickness of the polarizer 110 is less than 5 μm, it is difficult to control the polarizing plate manufacturing process, and breakage of the polarizer may occur or the axial uniformity of the polarizer may decrease. This may increase the amount of warpage.

A polarizer prepared by adsorbing iodine on a polyvinyl alcohol-based film and uniaxially stretching the film is, for example, immersed in an aqueous iodine solution for coloring a polyvinyl alcohol-based film, and the film is 3 to 7 times the original length. It can be produced by stretching. The aqueous solution may contain boric acid, zinc sulfate, zinc chloride, etc., or the polyvinyl alcohol-based film may be immersed in an aqueous solution such as potassium iodide, if necessary. In addition, the polyvinyl alcohol-based film may be immersed in water and washed before coloring, if necessary. The cleaning of the polyvinyl alcohol-based film not only removes contaminants from the film surface or washes off the anti-blocking agent, but also prevents non-uniformities such as uneven coloring by swelling the polyvinyl alcohol-based film. Stretching of the film may be performed after coloring the film with iodine, during coloring of the film, or before coloring the film with iodine. Stretching may be carried out in an aqueous solution of boric acid or potassium iodide, or in an aqueous solution.

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

As the base film 121 of the surface treatment film 120, a (meth)acrylic film is used as described above.

Examples of the (meth)acrylic film include polymethyl (meth) acrylate and polyethyl (meth) acrylate, and in particular, polymethyl methacrylate is preferable in view of controlling the amount of warpage.

In one embodiment of the present invention, the surface treatment layer 122 may be formed by applying an appropriate surface treatment coating composition on the base film 121 and curing it. The surface treatment layer 122 may be a hard coating layer or an anti-glare coating layer.

For example, the surface treatment coating composition may be a composition for forming an anti-glare layer or a hard coating composition, and may include a light-transmitting resin, light-transmitting particles, a photopolymerization initiator, and a solvent.

The light-transmitting resin is a photo-curable resin, and the photo-curable resin may include a photo-curable (meth)acrylate oligomer and/or monomer. As the photocurable (meth)acrylate oligomer, epoxy (meth)acrylate, urethane (meth)acrylate, etc. are commonly used, and urethane (meth)acrylate is preferable. Monomers that are commonly used may be used without limitation, and monomers having unsaturated groups such as (meth)acryloyl, vinyl, styryl, and allyl groups in the molecule as a photocurable functional group are preferable, and among them, (meth)acryl A monomer having a royl group is preferred.

The light-transmitting particles are used in the art and may be used without particular limitation as long as they are particles capable of imparting surface treatment properties. Examples of the light-transmitting particles include silica particles, silicone resin particles, melamine-based resin particles, acrylic resin particles, styrene-based resin particles, acrylic-styrene-based resin particles, polycarbonate-based resin particles, polyethylene-based resin particles, and vinyl chloride-based resins. particles and the like can be used. Each of the light-transmitting particles exemplified above may be used alone or in combination of two or more. It is preferable that the average particle diameter of the translucent particle is 1-10 micrometers. When the average particle diameter of the light-transmitting particles is less than 1 μm, it is difficult to form irregularities on the surface of the surface treatment layer 122, so that the surface treatment property is lowered. It has the disadvantage of poor visibility.

As the photopolymerization initiator, those used in the art may be used without limitation. Specifically, as the photopolymerization initiator, 2-methyl-1-[4-(methylthio)phenyl]2-morpholinepropanone-1, diphenylketone benzyldimethylketal, 2-hydroxy-2-methyl-1-phenyl -1-one, 4-hydroxycyclophenyl ketone, dimethoxy-2-phenylacetophenone, anthraquinone, fluorene, triphenylamine, carbazole, 3-methylacetophenone, 4-chloroacetophenone, 4, At least one selected from the group consisting of 4-dimethoxyacetophenone, 4,4-diaminobenzophenone, 1-hydroxycyclohexylphenylketone and benzophenone may be used.

The solvent may be used without limitation as long as it is known as a solvent in the art. For example, the solvent is alcohol-based (methanol, ethanol, isopropanol, butanol, methyl cellulose, ethyl sol sorb, 1-methoxy-2-propanol, propylene glycol monomethyl ether, etc.), ketone-based (methyl ethyl ketone, methyl Butyl ketone, methyl isobutyl ketone, diethyl ketone, dipropyl ketone, cyclohexanone, etc.), hexane-based (hexane, heptane, octane, etc.), benzene-based (benzene, toluene, xylene, etc.) can be preferably used. there is. Each of the solvents exemplified above may be used alone or in combination of two or more.

In addition to the above components, the surface treatment coating composition includes components commonly used in the art, for example, antioxidants, UV absorbers, light stabilizers, thermal polymerization inhibitors, leveling agents, surfactants, lubricants, and antifouling agents. It may additionally include an agent and the like.

The surface treatment layer 122 may be formed by applying a surface treatment coating composition to one surface of the base film 121 , drying it, and then UV curing.

The surface treatment coating composition can be coated by appropriately using known methods such as die coater, air knife, reverse roll, spray, blade, casting, gravure, micro gravure, spin coating, and the like.

After the surface treatment coating composition is applied, the volatiles are evaporated to dryness at a temperature of 30 to 150° C. for 10 seconds to 1 hour, more specifically, for 30 seconds to 30 minutes, and then cured by irradiation with UV light. make it The irradiation amount of UV light may be specifically about 0.01 to 10J/cm 2 , and more specifically 0.1 to 2 J/cm 2 . In this case, the thickness of the surface treatment layer to be formed may be specifically 1 to 30㎛, more specifically 1.5 to 10㎛.

The polarizer 110 may be bonded to the surface treatment film 120 with an adhesive layer interposed therebetween.

The adhesive layer may be formed from a water-based adhesive in which an adhesive component is dissolved or dispersed in water, a composition cured by receiving active energy ray irradiation (hereinafter, may be referred to as an active energy ray-curable adhesive), and the like.

Examples of the water-based adhesive include a composition containing a polyvinyl alcohol-based resin or a urethane resin as a main component, and a crosslinking agent or curable compound such as an isocyanate-based compound or an epoxy compound to improve adhesion.

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 group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, and methylol group-modified polyvinyl alcohol. and modified polyvinyl alcohol-based resins such as amino group-modified polyvinyl alcohol. An aqueous solution of a polyvinyl alcohol-based resin is an adhesive, and the concentration of the polyvinyl alcohol-based resin in the adhesive is usually 1 to 10 parts by weight, preferably 1 to 5 parts by weight, based on 100 parts by weight of water.

The adhesive containing an aqueous solution of a polyvinyl alcohol-based resin may contain a curable compound such as a polyhydric aldehyde, a water-soluble epoxy resin, a melamine-based compound, a zirconia-based compound, and a zinc compound to improve adhesion.

As the water-soluble epoxy resin, a water-soluble polyamide epoxy obtained by reacting epichlorohydrin with a polyamide polyamine obtained by reaction of a polyalkylene polyamine such as diethylenetriamine or triethylenetetraamine with a dicarboxylic acid such as adipic acid and resin. Examples of commercially available polyamide epoxy resins include "Sumirez Resin 650" and "Sumirez Resin 675" (Sumika Chemtex Co., Ltd.) and "WS-525" (Nippon PMC Co., Ltd.). Content of a water-soluble epoxy resin is 1-100 weight part normally with respect to 100 weight part of polyvinyl alcohol-type resin, Preferably it is 1-50 weight part.

When the main component of the adhesive is a urethane resin, the urethane resin is preferably a polyester-based ionomer-type urethane resin. The polyester-based ionomer type urethane resin is a urethane resin having a polyester skeleton, and an ionic component (hydrophilic component) is introduced thereinto. Even if an ionomer type urethane resin does not use an emulsifier, it emulsifies in water and becomes an emulsion. The aqueous adhesive containing the polyester-based ionomer-type urethane resin preferably contains a water-soluble epoxy compound as a crosslinking agent.

When the polarizer 110 and the surface treatment film 120 are adhered with a water-based adhesive, the water-based adhesive is injected between the polarizer 110 and the surface treatment film 120, dried to evaporate water, and a thermal crosslinking reaction is performed. By advancing, sufficient adhesiveness can be provided to both.

An active energy ray hardening-type adhesive agent receives and hardens active energy ray irradiation. Examples of the active energy ray-curable adhesive include a cationically polymerizable active energy ray-curable adhesive containing an epoxy compound and a cationic polymerization initiator, a radically polymerizable active energy ray-curable adhesive containing an acrylic curing component and a radical polymerization initiator, and a cationic polymerizable epoxy compound. An active energy ray-curable adhesive comprising both a curing component and a radically polymerizable curing component such as an acrylic compound, and further comprising a cationic polymerization initiator and a radical polymerization initiator, and an electron beam curing type active energy ray-curable adhesive that is cured by irradiation with an electron beam, etc. can be heard The electron beam curing type active energy ray curing type adhesive does not contain an initiator.

Especially, the cationically polymerizable active energy ray hardening-type adhesive agent containing an epoxy compound and a cationic polymerization initiator is preferable. It is preferable that an active energy ray hardening-type adhesive agent does not contain a solvent substantially.

As an epoxy compound capable of cationic polymerization, it is a liquid at room temperature itself, has adequate fluidity even in the absence of a solvent, and imparts appropriate cured adhesive strength. Obtained by selecting a cationic polymerization initiator suitable for the epoxy compound According to an active energy ray hardening-type adhesive agent, the drying installation normally required in an adhesion|attachment process can be abbreviate|omitted. In addition, by irradiating an appropriate active energy dose, the curing rate can be accelerated, and the production rate can be improved.

As the epoxy compound, glycidyl ether compound of an aromatic compound or chain compound having a hydroxyl group, glycidyl amination compound of a compound having an amino group, epoxide compound of a chain compound having a C-C double bond, directly or via an alkylene on a saturated carbocyclic ring and an alicyclic epoxy compound in which a glycidyloxy group or an epoxyethyl group is bonded or an epoxy group is directly bonded to a saturated carbocyclic ring. An epoxy compound can also use other multiple types together. Especially, an alicyclic epoxy compound is preferable at the point excellent in cationic polymerizability.

The thickness of the adhesive layer may be appropriately determined according to the type of resin serving as the adhesive, adhesive strength, environment in which the adhesive is used, and the like. The adhesive layer preferably has a thickness of 0.01 μm to 50 μm, more preferably 0.05 μm to 20 μm, and still more preferably 0.1 μm to 10 μm.

In the polarizing plate according to an embodiment of the present invention, as shown in FIG. 2 , a retardation layer 130 may be further laminated on the other surface of the polarizer 110 .

The retardation layer 130 may be, for example, a stretched or unstretched polymer film, or a liquid crystal layer obtained by curing a reactive liquid crystal compound.

For example, when the retardation layer 130 is made of a liquid crystal layer, a reactive liquid crystal compound (RM), which is a liquid crystal compound having optical anisotropy and crosslinking by light or heat, may be used.

The retardation layer 130 may have a single layer structure or a multilayer structure in which two or more layers are stacked. For example, the retardation layer 130 may have 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 retardation film and a positive C plate layer, and a negative biaxiality It may have a laminated structure such as a combination of a retardation film and a positive C-plate layer. At this time, each layer constituting the retardation layer may be attached to each other via an adhesive agent or may be laminated on each other by direct coating.

The retardation layer 130 may have a plane-direction retardation (R ₀ ) of 0 to 10 nm at a wavelength of 550 nm. When the plane direction retardation (R ₀ ) of the retardation layer at a wavelength of 550 nm is within the above range, a wide viewing angle and color gamut may be improved.

The polarizer 110 and the retardation layer 130 may be bonded using an adhesive.

The pressure-sensitive adhesive may be formed using various pressure-sensitive adhesives or adhesives well known in the art, and the type is not particularly limited.

For example, as the adhesive, a rubber-based adhesive, an acrylic adhesive, a silicone-based adhesive, a urethane-based adhesive, a polyvinyl alcohol-based adhesive, a polyvinylpyrrolidone-based adhesive, a polyacrylamide-based adhesive, a cellulose-based adhesive, a vinyl alkyl ether-based adhesive, etc. for example.

In addition, the adhesive may be a photocurable adhesive, and the type thereof is not particularly limited.

The photocurable adhesive is crosslinked and cured by receiving active energy rays such as ultraviolet (Ultraviolet, UV), electron beam (EB), etc.

The reactive oligomer is an important component that determines the properties of the adhesive, and forms a polymer bond by photopolymerization to form a cured film. Examples of the usable reactive oligomer include polyester-based resins, polyether-based resins, polyurethane-based resins, epoxy-based resins, polyacrylic-based resins, and silicone-based resins.

The reactive monomer serves as a crosslinking agent and a diluent of the above-described reactive oligomer, and affects adhesive properties. Examples of the usable reactive monomer include monofunctional monomers, polyfunctional monomers, epoxy-based monomers, vinyl ethers, and cyclic ethers.

The photopolymerization initiator serves to initiate photopolymerization by absorbing light energy to generate radicals or cations, and may be used by selecting a suitable one according to the photopolymerization resin.

As shown in FIG. 3 , the pressure-sensitive adhesive layer 140 may be further laminated on the opposite surface of the surface opposite to the polarizer of the retardation layer 130 . The pressure-sensitive adhesive layer 140 may serve to attach the polarizing plate 100 to an OLED panel or a touch panel.

The pressure-sensitive adhesive layer 140 may be formed using various pressure-sensitive adhesives well known in the art, and the type thereof is not particularly limited.

For example, as the adhesive, a rubber-based adhesive, an acrylic adhesive, a silicone-based adhesive, a urethane-based adhesive, a polyvinyl alcohol-based adhesive, a polyvinylpyrrolidone-based adhesive, a polyacrylamide-based adhesive, a cellulose-based adhesive, a vinyl alkyl ether-based adhesive, etc. for example.

The thickness of the pressure-sensitive adhesive layer 140 is preferably 5 to 30 μm, but is preferably applied thinly in a range that does not impair workability and durability characteristics, and more preferably 10 to 25 μm. If the thickness of the pressure-sensitive adhesive layer 140 is less than 5 μm, pits and damage in the panel cannot be filled, so defects may be recognized.

In the polarizing plate according to an embodiment of the present invention, a peelable protective film (not shown) may be further laminated on the opposite surface of the surface-treated film 120 opposite to the polarizer.

The peelable protective film includes a substrate and an adhesive layer formed on one surface of the substrate. The pressure-sensitive adhesive layer is attached to the surface-treated film 120 , and when the polarizing plate is attached to the cover window, the pressure-sensitive adhesive layer is peeled off from the surface-treated film 120 so that the protective film can be easily removed. As a material of the pressure-sensitive adhesive layer, the above-mentioned pressure-sensitive adhesive may be used.

Examples of the base material of the peelable protective film include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; Or polyolefin films, such as polypropylene and polyethylene, etc. are mentioned.

The peelable protective film may have a thickness of 10 to 150 μm, preferably 25 to 130 μm. If the thickness of the peelable protective film is less than 10 μm, peeling of the protective film may not be easy, and if it exceeds 150 μm, adhesion with the polarizer having a protective layer may be reduced.

In addition, in the polarizing plate according to the exemplary embodiment of the present invention, a release film (not shown) may be further laminated on the opposite side of the side opposite to the retardation layer of the pressure-sensitive adhesive layer 140 .

The release film is removed when the polarizing plate is attached to an OLED panel or a touch panel or the like.

Examples of the base material for the release film include polyester films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; Or polyolefin films, such as polypropylene and polyethylene, etc. are mentioned.

The surface of the base material of the release film in contact with the pressure-sensitive adhesive layer 140 may be subjected to a release treatment. For the release treatment, a release agent such as a silicone-based release agent, a fluorine-based release agent, or a long-chain alkyl graft polymer-based release agent, or a method of surface treatment by plasma treatment may be used.

The release film may have a thickness of 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 may not be easy, and when it exceeds 150 μm, adhesion with the pressure-sensitive adhesive layer 140 may be reduced.

The total thickness of the polarizing plate according to an embodiment of the present invention may be 130 to 220㎛, preferably 145 to 160㎛. At this time, the total thickness of a polarizing plate is the thickness except the thickness of a peelable protective film and a peeling film.

One embodiment of the present invention relates to an image display device including the polarizing plate (100).

An image display device according to an embodiment of the present invention is applicable to various image display devices such as an organic EL display device, a plasma display device, and a field emission display device, as well as a general liquid crystal display device.

The image display device may further include a configuration known in the art in addition to the polarizing plate.

Hereinafter, the present invention will be described in more detail by way of Examples and Experimental Examples. These Examples and Experimental Examples are only for illustrating the present invention, and it is apparent to those skilled in the art that the scope of the present invention is not limited thereto.

Preparation Example 1: Preparation of a composition for forming an anti-glare layer

14 wt% urethane acrylate (Miwon Corp., SC2153), 15 wt% pentaerythritol triacrylate (Miwon Corp., M340), 1 wt% light-transmitting particles (acrylic-styrene copolymer, refractive index 1.525, average particle diameter 2㎛), 67 As a wt% solvent, ethyl acetate, 2.5 wt% photoinitiator (Cibasa, I-184) and 0.5 wt% leveling agent (BYK Chemis, BYK3550) were blended using a stirrer, filtered using a PP material filter, and the anti-glare layer A composition for forming was prepared.

Preparation Example 2: Preparation of polarizer

A transparent, 75 μm-thick, unstretched polyvinyl alcohol film having a saponification degree of 99.9% or more was controlled with humidity so that the moisture content was 4%. Thereafter, after the first stretching at a draw ratio of 4.5 times by the heating roll stretching method at 120° C., it was immersed in water (deionized water) at 50° C. for 1 minute to swell. Then, the dye was immersed in an aqueous solution for dyeing at 30° C. containing 5.0 mmol/L of iodine and 4 wt% of potassium iodide for 1 minute. At this time, it was stretched 0.9 times and 1.1 times, respectively, in the swelling and dyeing steps. Then, it was crosslinked by immersion in an aqueous solution for crosslinking at 70° C. containing 10% by weight of potassium iodide and 7% by weight of boric acid for 3 minutes. In the crosslinking step, it was stretched 1.2 times. After the crosslinking was completed, the polyvinyl alcohol film was dried in an oven at 70° C. for 4 minutes to prepare a polarizer.

Preparation Examples 1 to 3 and Preparation Comparative Examples 1 to 6: Preparation of surface-treated films

After coating the composition for forming an anti-glare layer of Preparation Example 1 to a thickness of 23 μm on a substrate film, the solvent was dried at 80° C. for 2 minutes. The dried film was irradiated with UV at an accumulated light amount of 400 mJ/cm ² to prepare an anti-glare film as a surface treatment film. As the base film, the films shown in Table 1 below were used.

Examples 1 to 3 and Comparative Examples 1 to 6: Preparation of a polarizing plate

A polarizing plate was manufactured in the same structure as in the embodiment of FIG. 1 according to the following method.

The polarizer prepared in Preparation Example 2 was bonded to the base film of the surface-treated film prepared in Preparation Example and Preparation Comparative Example using an acrylic UV-curable adhesive. Thereafter, a polarizing plate was manufactured by irradiating UV with an accumulated light amount of 400 mJ/cm ² .

Experimental example:

The physical properties of the surface-treated films prepared in Preparation Examples and Preparation Comparative Examples and the polarizing plates prepared in Examples and Comparative Examples were measured by the following method, and the results are shown in Table 1 below.

(1) Moisture permeability of the surface-treated film

According to JIS Z 0208 moisture permeability test (cup method) for the surface-treated films prepared in Manufacturing Examples and Manufacturing Comparative Examples, the amount of water vapor that passes through each sample of 1 m ² in an environment of 40° C. and 90% relative humidity for 24 hours (g, the amount of change in weight of the sample) was measured.

(2) Tensile strength of polarizing plate

The polarizing plates of Examples and Comparative Examples were cut to a width of 5 mm with the long side in the MD direction so that the gage point distance was set to 50 mm. Using a tensile strength measuring device (UTM autograph, Shimadzu Corporation, Model No. AG-X 1KN), it was measured until the sample broke at a measuring speed of 4 mm/min, and the maximum value was taken to evaluate the tensile strength.

(3) Deflection amount

The polarizing plates of Examples and Comparative Examples were respectively laminated on both sides of a glass of 320 mm × 180 mm × 0.7 mm, and then left for 100 hours under moist heat-resistant conditions (60° C., relative humidity 90%). When laminating the polarizing plate, an acrylic pressure-sensitive adhesive (Lintec) having a thickness of 15 μm was used as the pressure-sensitive adhesive layer.

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

(4) polarizer curl

The polarizing plates of Examples and Comparative Examples were cut to a size of 700 × 300 mm with the long side in the MD direction, placed on a flat plate, and the maximum height from the reference plane was measured.

At this time, the curl value can be obtained by placing the convex side of the polarizing plate in contact with the reference surface and then measuring the average of the heights from the reference surface to the four corners. When the convex surface of the polarizing plate is placed in contact with the reference plane, the forward curl is when the surface-treated film is positioned above the polarizer, and the reverse curl is when the surface-treated film is positioned below the polarizer.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Base film type PMMA PMMA PMMA PMMA PMMA TAC TAC TAC TAC Thickness of the base film (㎛, a) 100 80 60 50 110 25 80 60 40 Tensile strength of polarizing plate (Mpa, b) 110 98 87 85 121 201 250 232 250 Moisture permeability of surface treated film (g/m ² /24hr, c) 41 53 68 81 35 510 320 353 501 Polarizer bending amount (mm) 0.72 0.93 1.21 1.3 0.6 1.39 1.43 1.65 1.79 Polarizer curl (mm) 5mm 5mm 6mm 7mm -2mm 5mm 4mm 8mm 6mm a×b/c 268 148 77 52 380 10 63 39 20

PMMA: polymethyl methacrylate

TAC: triacetyl cellulose

a: the thickness of the base film (㎛)

b: Tensile strength of polarizing plate (Mpa)

c: moisture permeability of the surface-treated film (g/m2/24hr)

As shown in Table 1, in the polarizing plates of Examples 1 to 3 satisfying 70 ≤ a × b/c ≤ 300 according to the present invention, the polarizing plate forms a junction, and the amount of warpage when glass is applied was less than 1.3 mm.

On the other hand, the polarizing plates of Comparative Examples 1 and 3 to 6 having an a×b/c value of less than 70 showed an increase in warpage, and the polarizing plate of Comparative Example 2 having an a×b/c value of more than 300 showed reverse curl.

Accordingly, it was found that the polarizing plates of Examples 1 to 3 could improve light leakage by controlling the bending characteristics of large panels without reverse curling compared to the polarizing plates of Comparative Examples 1 to 6.

As the specific part of the present invention has been described in detail above, for those of ordinary skill in the art to which the present invention pertains, it is clear that these specific techniques are only preferred embodiments, and the scope of the present invention is not limited thereto. Do. Those of ordinary skill in the art to which the present invention pertains will be able to make various applications and modifications within the scope of the present invention based on the above contents.

Accordingly, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

110: polarizer 120: surface treatment film
121: base film 122: surface treatment layer
130: retardation layer 140: adhesive layer

Claims (13)

A polarizing plate comprising a polarizer and a surface-treated film laminated on one surface of the polarizer,
The surface treatment film includes a (meth)acrylic film as a base film,
A polarizing plate satisfying Equation 1 below:
[Equation 1]
70 ≤ a×b/c ≤ 300
In the above formula,
a is the thickness (㎛) of the base film,
b is the tensile strength (Mpa) of the polarizing plate,
c is the moisture permeability (g/m 2 /24hr) of the surface-treated film. The polarizing plate according to claim 1, wherein the surface-treated film includes a base film having a surface-treated layer formed on at least one surface thereof. According to claim 1, wherein the thickness of the base film is 60㎛ or more polarizing plate. The polarizing plate according to claim 1, wherein the tensile strength is 85 Mpa to 150 Mpa. The polarizing plate according to claim 1, wherein the surface-treated film has a moisture permeability of 70 g/m 2 /24hr or less. The polarizing plate of claim 1, wherein the polarizer has a thickness of 5 μm to 30 μm. The polarizing plate according to claim 2, wherein the surface treatment layer is a hard coating layer or an anti-glare coating layer. The polarizing plate according to claim 1, further comprising a retardation layer laminated on the other surface of the polarizer. The polarizing plate of claim 8, wherein the retardation layer has an in-plane retardation (R ₀ ) of 0 to 10 nm at a wavelength of 550 nm. The polarizing plate according to claim 8, wherein a pressure-sensitive adhesive layer is further laminated on a surface opposite to the surface opposite to the polarizer of the retardation layer. The polarizing plate according to claim 1, wherein a peelable protective film is further laminated on an opposite surface of the surface-treated film opposite to the polarizer. The polarizing plate according to claim 10, wherein a release film is further laminated on a surface opposite to the surface opposite to the retardation layer of the pressure-sensitive adhesive layer. An image display device comprising the polarizing plate according to any one of claims 1 to 11.

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