KR20170001026A - Polarizing plate and liquid crystal display device comprising thereof - Google Patents

Abstract

The present invention relates to a polarizing plate and a liquid crystal display device including the same, and more particularly, to a polarizing plate with a structure where a prism sheet, a first adhesive layer, a protection film, a diffusion adhesive layer, a polarizer, and a second adhesive layer are successively laminated, and a liquid crystal display device including the same. The polarizing plate with the structure improves visibility of the liquid crystal display device by suppressing a moire fringe generation phenomenon caused in the prism sheet and preventing the degradation of brightness and the degree of polarization and implements slimness.

Description

TECHNICAL FIELD [0001] The present invention relates to a polarizing plate and a liquid crystal display having the polarizing plate.

The present invention relates to a polarizing plate capable of suppressing occurrence of a moire pattern generated by a prism sheet and realizing excellent visibility when introduced into a liquid crystal display, and a slim liquid crystal display equipped with the polarizing plate.

Liquid crystal displays (LCDs) are used in various fields because they can be manufactured with low power consumption and thinner in a planar manner, and the market share of the flat panel displays is the highest.

In general, a liquid crystal display device (LCD) includes a liquid crystal panel including a liquid crystal cell including a liquid crystal, a polarizing plate stacked on both sides of the liquid crystal cell, and a backlight unit for providing light to the liquid crystal panel .

The backlight unit is intended to make the light of the light source uniform, and to increase the efficiency of utilization of the luminance and light, which is a core part that is indispensable for an LCD which is a non-luminous display that can not emit light by itself.

Specifically, the backlight unit converts the fluorescent light such as a line into a flat light by maintaining the same brightness to every corner of the LCD. Such a backlight unit is divided into a direct type and an edge type according to the manner in which the light emission source is disposed. The backlight unit is divided into a reflection plate, a backlight light source, a light guide plate, a light diffusion member (diffusion plate, diffusion sheet) .

The direct type backlight unit has a point light source structure in which a light source is disposed so as to face the front of the device directly below the liquid crystal panel, and the light emitted from the light source is reflected and diffused by the reflection plate and the diffusion plate. Such a direct-type backlight unit has advantages such as high luminance and light weight, but has a disadvantage in that it is difficult to form a thin film, and light with a strong directivity enters the user's field of view directly, thereby causing glare and fatigue.

The edge type backlight unit is a planar light source structure in which light emitted from one side or both sides of a liquid crystal panel is incident on the side of the panel and diffused and scattered over the entire area by a reflection plate and a light guide plate. Such an edge type backlight unit is advantageous in that it is lighter in weight than the direct type, but is easy to adjust the luminance and direction of light directing, is advantageous for thinning, and has a long service life.

Specifically, the edge type backlight unit in the LCD enters the light guide plate with light emitted from the light source, and propagates while repeating total reflection on the light exit surface (liquid crystal cell side surface) and the back surface of the light guide plate. A part of the light propagating in the light guide plate is emitted from the light exit surface of the light guide plate by the light scattering body formed on the back surface of the light guide plate or the like. The light emitted from the light exit surface of the light guide plate is diffused and condensed by various optical sheets such as a diffusion sheet, a prism sheet, and a brightness enhancement film, and then enters a liquid crystal display panel having polarizing plates disposed on both sides of the liquid crystal cell. The liquid crystal molecules of the liquid crystal layer of the liquid crystal cell are driven for each pixel, and an image is displayed by controlling transmission and absorption of incident light.

The prism sheet used in the above-described backlight unit is used to compensate for a decrease in luminance of light passing through the diffusion sheet or the diffusion plate. Generally, it is fitted into the casing of the apparatus and is formed close to the exit surface of the light guide plate.

In a liquid crystal display device using such a backlight unit, the light guide plate may be rubbed by the prism sheet under installation or in a practical use environment, and scratches may occur in the light guide plate. In order to solve such a problem, a technique of integrating the prism sheet with the light source side polarizing plate has been proposed. However, the liquid crystal display device using the polarizing plate in which such a prism sheet is integrated has a problem that the front luminance is insufficient and dark.

In addition, the prism sheet is used to improve the brightness by refracting and condensing light passing through the diffusion sheet or the diffusion plate, but generates a moire fringe which is an interference phenomenon due to the regular structure of the prism sheet. The generated moire pattern causes the display quality such as the visibility of the liquid crystal display device to deteriorate.

In order to solve such a problem, it has been proposed to form a light diffusion layer on a prism sheet. However, when a light-diffusing layer having strong light-diffusing property enough to overcome moiré is used, there arises a problem that the luminance of the liquid crystal display device is lowered.

Japanese Patent Laid-Open Publication No. 2011-123476 discloses a polarizing plate in which a pressure sensitive adhesive exhibiting light diffusing properties is laminated on one side of a polarizing film and a sheet member having a prismatic shape is laminated on the other side.

Further, WO 2009/108003 discloses a technique for minimizing the occurrence of moire patterns by properly matching the arrangement of the optical sheets matched with the liquid crystal panel of the liquid crystal display device so that some of them are parallel and some of them are not parallel .

Although these patents limit the generation of moire patterns, the polarization and brightness of the liquid crystal display device are not only degraded but also their effects are not sufficient.

Japanese Laid-Open Patent Publication No. 2011-123476 International Publication (WO) No. 2009/108003

As a result of various studies in order to suppress the occurrence of moire patterns caused by the prism sheet and the liquid crystal panel, the present applicant has found that a polarizer, a protective film and a prism sheet are provided, and an adhesive such as PVA It has been confirmed that the above problem can be solved by using a diffusion adhesive layer for adhesion between the protective film and the prism sheet and by keeping the air gap ratio of the prism sheet at a certain level or more. Thereby completing the invention.

Accordingly, it is an object of the present invention to provide a polarizing plate in which a diffusing adhesive layer and a diffusion adhesive layer are formed instead of a separate diffusion sheet and the generation of moire fringes due to the prism sheet is suppressed through adjustment of the air gap ratio and brightness and durability are improved .

It is still another object of the present invention to provide a liquid crystal display device provided with the polarizing plate.

In order to achieve the above object, the present invention provides a polarizing plate characterized in that a prism sheet, a first pressure-sensitive adhesive layer, a protective film, an adhesive layer, a polarizer and a second pressure-sensitive adhesive layer are laminated in this order, to provide.

And the haze value of the diffusion adhesive layer is in the range of 30 to 99%.

Wherein the diffusion adhesive layer includes particles having an average particle diameter in the range of 0.1 to 10 mu m.

The thickness of the diffusion adhesive layer is in the range of 0.5 to 20 mu m.

And the airgap ratio represented by the following formula (1) on the bonding surface of the prism sheet and the first pressure-sensitive adhesive layer is 50% or more.

[Equation 1]

(In the above formula (1), H and h are as described in the specification)

In addition, the polarizing plate is further characterized in that the first pressure sensitive adhesive layer is a diffusion pressure sensitive adhesive layer.

And the haze value of the diffusion pressure-sensitive adhesive layer is in the range of 30 to 99%.

Wherein the diffusion adhesive layer includes particles having an average particle diameter in the range of 0.1 to 20 mu m.

Further, the thickness of the diffusion pressure-sensitive adhesive layer is in the range of 5 to 50 mu m.

The polarizing plate may further include an adhesive layer and a protective film between the polarizer and the second pressure sensitive adhesive layer.

In addition, the present invention provides a liquid crystal display device having the polarizing plate.

The polarizing plate according to the present invention can solve the occurrence of moire patterns caused by the prism sheet by using a diffusion adhesive layer for bonding the polarizing plate and the protective film constituting the polarizing plate without using a separate diffusion sheet for preventing moiré. In addition, by adjusting the air gap ratio between the prism sheet and the pressure-sensitive adhesive layer bonded thereto to a certain level and providing a diffusion adhesive layer instead of the conventional pressure-sensitive adhesive, the problem of moire pattern generation and the resulting polarization degree and luminance degradation are further improved.

The polarizing plate can be made slimmer when introduced into a liquid crystal display device, and optical quality can be improved, so that an image having excellent visibility compared to a conventional polarizing plate can be realized.

1 is a cross-sectional view illustrating a polarizing plate according to a first embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a prism sheet and a first pressure-sensitive adhesive layer of a polarizing plate according to the present invention, wherein (a) shows a state before bonding, and (b) shows a state after bonding.
1 is a cross-sectional view illustrating a polarizing plate according to a second embodiment of the present invention.
4 is a graph showing luminance distributions of Comparative Example 1 and Examples 1 to 3 of the present invention.
5 is a graph showing luminance distributions of Comparative Examples 1 and 11 to 13 of the present invention.

Disclosed is a polarizing plate which suppresses occurrence of a moire pattern and improves display quality of a liquid crystal display device.

Among the elements constituting the backlight unit, the prism sheet functions to refract and condense the widely radiated light emitted from the diffusion sheet or the diffusion plate to increase the brightness. However, due to the combination of the regular sectional shape of the prism sheet and the periodic structure of the liquid crystal cell, a moire pattern having another period is generated. Such a moire pattern is periodically bright and dark in the liquid crystal panel, thereby deteriorating the quality such as the degree of polarization and brightness of the liquid crystal display device.

Accordingly, the present invention solves the above-mentioned problem by providing a diffusion adhesive layer between the protective film and the polarizer.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to the drawings. However, the drawings attached hereto are only illustrative of the present invention, and the present invention is not limited to the drawings. Also, for ease of explanation, some of the elements may be exaggerated in the drawings, or may be omitted or omitted.

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

1, a polarizing plate 100 according to the present invention includes a prism sheet 101, a first pressure-sensitive adhesive layer 103, a protective film 105, a diffusion adhesive layer 107, a polarizer 109, 2 pressure-sensitive adhesive layer 111 are sequentially laminated. At this time, the second pressure sensitive adhesive layer 111 is bonded to the liquid crystal cell (not shown) upon introduction into the display device.

In particular, the polarizing plate 100 of the present invention has a diffusion adhesive layer 107 so that not only the polarizer 109 and the protective film 105 are sufficiently bonded but also has light diffusibility. The diffusion adhesive layer 107 serves to alleviate the moiré pattern caused by interference between the regular shape derived from the cross section of the prism sheet and the regular shape derived from the matrix structure of the color filter of the liquid crystal cell. Specifically, due to the light diffusion function of the diffusion adhesive layer 107, the regularity derived from the surface shape of the prism sheet is relaxed by the diffusion, and interference with the regular shape derived from the matrix structure or the like of the color filter of the liquid crystal cell Is suppressed to a large extent, the occurrence of the moire pattern is suppressed, and thus an image with excellent display quality can be obtained.

The diffusion adhesive layer 107 is an adhesive layer in which particles capable of scattering and diffusing light are dispersed. As long as the particles are mixed and dispersed in the adhesive resin so as to have a uniform and high light diffusing property, various materials such as organic particles and inorganic particles can be used, and the present invention is not particularly limited thereto.

For example, the organic particles may be particles composed of a polystyrene type resin, a polyolefin type resin such as polyethylene or polypropylene, or a polymer compound such as acrylic resin. Further, it may be a particle composed of a copolymer formed by copolymerizing two or more kinds of monomers selected from ethylene, propylene, styrene, methyl methacrylate, benzoguanamine, formaldehyde, melamine, butadiene and the like. Examples of the inorganic particles include particles of silica, calcium carbonate, aluminum hydroxide, titanium dioxide and the like.

These particles are preferably colorless or white.

In addition, the shape of the particles may be various shapes and is not particularly limited in the present invention. Preferably, spheres are suitable. The average particle diameter of the particles is in the range of 0.1 to 10 mu m, and is preferably in the range of 0.5 to 5 mu m. If the average particle diameter of the particles is less than the above-mentioned range, the light diffusing function is not exhibited. On the contrary, if the average particle diameter exceeds the above-mentioned range, the display quality can be lowered when applied to a liquid crystal display device.

The content of such particles is not particularly limited and can be adjusted according to the average particle diameter of the particles and the thickness of the diffusion adhesive layer 107. For example, it is 0.01 to 100 parts by weight, preferably 1 to 50 parts by weight, per 100 parts by weight of the adhesive agent to be dispersed.

In addition, since the particles are in powder form, when they are added directly to an adhesive resin described later, the dispersion stability is lowered and the particles are not uniformly distributed in the adhesive resin. Therefore, it is preferable that the particles are completely dispersed in a solvent and then added to the adhesive. Therefore, the type of the solvent for dispersing the particles is not particularly limited. For example, the same solvent as that used in the production of the adhesive resin can be used, and as an acetate, benzene or ketone solvent excellent in dispersibility and solvent resistance to organic particles, ethyl acetate, toluene, xylene, methyl Ethyl ketone or the like may be used.

The adhesive used for the diffusion adhesive layer 107 is for bonding the protective film 105 and the polarizer 109 and is not particularly limited as long as it has excellent adhesive force and optical transparency and does not change with time. Adhesive is used.

The photo-curable adhesive is crosslinked and cured by receiving an active energy ray such as ultraviolet (UV), electron beam (EB) or the like and exhibits a strong adhesive force, and is composed of a reactive oligomer, a reactive monomer, a photopolymerization initiator and an additive.

The reactive oligomer is an important component for determining the properties of the adhesive, and forms a cured coating by forming a polymer bond by a photopolymerization reaction. Examples of the reactive oligomer that can be used include a polyester resin, a polyether resin, a polyurethane resin, an epoxy resin, a polyacrylic resin, and a silicone resin.

The reactive monomer serves as a crosslinking agent and a diluent for the reactive oligomer described above, and affects the adhesion property. Examples of the reactive monomer that can be used include monofunctional monomers, polyfunctional monomers, epoxy-based monomers, vinyl ethers, and cyclic ethers.

The photopolymerization initiator absorbs light energy to generate radicals or cations to initiate photopolymerization, and is selected and used in accordance with the photopolymerization resin. Examples of the photo radical polymerization initiator include benzoin ethers, amines, acetophenones, thioxanthones, and benzophenones. Photocatalytic polymerization initiators include diazonium salts, iodonium salts, sulfonium salts, Metal nosecane compounds and the like.

A photo-sensitizer, a thickener, a polymerization inhibitor and the like may be used as additives in the above-mentioned composition according to the use.

The photo-curing adhesive containing the above-mentioned components may be directly produced or may be a commercially available adhesive. Commercially available products include, for example, KR-70T and KR-15P (hereinafter referred to as ADEKA).

The composition for forming a diffusion adhesive layer containing the particles and the photo-curing adhesive described above is cured by applying the composition to a polarizer and / or a protective film, bonding the films to each other, and then irradiating with active energy rays.

The composition may be applied by a known method. For example, a softening method, a Meyer bar coating method, a gravure coating method, a comma coater method, a doctor blade method, a die coating method, a dip coater method, . For example, the adhesive composition described above is applied to the surface while the object to be coated is moved in a vertical direction, a horizontal direction, or an inclined direction therebetween. After the application of the adhesive, the members to be joined together are overlapped and joined together by one or a plurality of rolls or the like to perform bonding.

The joining using a roll can be carried out by, for example, applying the adhesive, spreading it uniformly on a roll or the like, applying the adhesive, spreading it between the roll and the roll, and expanding it. In the case of the former, metal or rubber can be used as the material of the roll. When the latter plurality of rolls are used, they may be the same material or different materials.

After the bonding, the diffusion adhesive layer 107 is cured using an active energy ray. The light source of the active energy ray to be used at this time is not particularly limited, but it is preferable to generate ultraviolet rays having a light emission distribution with a wavelength of 400 nm or less. Specifically, low energy mercury lamps, medium pressure mercury lamps, high pressure mercury lamps, A black light lamp, a microwave excited mercury lamp, a metal halide lamp, and the like are preferably used. In addition, it is preferable that the curing is performed under a condition that the original function of the polarizing plate such as the polarizing degree, the transmittance and the hue of the polarizer, and the transparency of the prism sheet and the protective film are not deteriorated.

The light irradiation intensity of the active energy ray is determined according to the composition of the diffusion adhesive of the present invention and is not particularly limited. In general, it is preferable that the light irradiation intensity in the wavelength region effective for activating the photopolymerization initiator is 0.1 to 6000 mW / cm ² . When the ratio falls within the above range, the reaction time does not become too long, and changes such as yellowing or deterioration due to heat radiated from the light source or heat generation during photo-curing are less likely to occur. The light irradiation time is controlled by the composition of the above-mentioned diffusion adhesive and is not particularly limited. Generally, it is preferable that the integrated amount of light to be displayed as the product of the light irradiation intensity and the light irradiation time is set to 10 to 10,000 mJ / m ² . When the amount is in the above range, active radicals such as radicals or cations are sufficiently generated from the photopolymerization initiator, so that a reliable photo-curing reaction proceeds, and the light irradiation time does not become too long, so that good productivity can be maintained.

The diffusion adhesive layer 107 formed through the above-described composition and method has a haze value in the range of 30 to 99%, preferably in the range of 40 to 97%. Here, the haze value is the degree of fog which appears when light passes through the sample, and the sample in the present invention refers to the diffusion adhesive layer 107. The haze value refers to the ratio of the diffuse transmittance (T _d ) divided by the total transmittance (T _t ). Here, the diffusion transmitted light (T _d ) is the amount of scattered light among the light transmitted through the sample, and the total transmitted light (T _t ) is the amount of all light transmitted through the sample. On the other hand, the parallel transmitted light (T _p ) can be represented by a value obtained by subtracting the diffused transmitted light (T _d ) from the total transmitted light (T _t ) by the amount of transmitted light without causing scattering among the transmitted light.

In the present invention, when the haze value of the diffusion adhesive layer 107 is less than the above range, the light diffusion is reduced and a moire pattern is generated. On the other hand, when the haze value exceeds the above range, the scattering angle becomes large and the luminance is lowered.

The thickness of the diffusion adhesive layer 107 is in the range of 0.5 to 20 mu m, preferably in the range of 1 to 10 mu m. If the thickness is less than the above range, the adhesive property is insufficient and it is difficult to impart the light diffusion performance. On the contrary, when the thickness exceeds the above range, defective appearance of the polarizing plate may occur.

The prism sheet 101 of the present invention is constituted by arranging unit prisms in parallel on one surface of a sheet, thereby intentionally changing the direction of incident light and improving the brightness.

Any suitable configuration can be employed for the unit prism within the range in which the effect of the present invention can be obtained. The unit prisms may have a triangular cross section in a cross section parallel to the arrangement direction and parallel to the thickness direction, and may have other shapes (for example, one or both of the triangular slopes have different inclination angles Or a shape having a plurality of flat surfaces). The triangular shape may be a shape that is asymmetric with respect to a straight line orthogonal to the sheet surface beyond the apex of the unit prism (for example, a diagonal triangle) or a shape symmetrical with respect to the straight line (for example, an isosceles triangle). In addition, the apex of the unit prism may be a chamfered curved surface, or a tip end may be cut so as to be a flat surface so as to have a trapezoidal shape. The unit prism may be appropriately selected according to the purpose, but is preferably triangular.

When the unit prism of the prism sheet 101 is in a triangular shape, the apex angle of the unit prism is in the range of 60 to 120 degrees, preferably 85 to 95 degrees, for condensing the light incident on the prism. Further, the height of the unit prism (linear distance along the vertical direction between the bottom surface and the vertex angle of the unit prism) is in the range of 10 to 200 mu m, preferably in the range of 15 to 100 mu m, for ease of handling of the prism sheet. In addition, the unit prism pitch interval (the shortest distance between the ridges of adjacent unit prisms) is in the range of 5 to 300 mu m, preferably in the range of 10 to 100 mu m, to fill the aforementioned apex angle and height.

The unit prisms existing on the surface of the prism sheet 101 may include unit prisms having a plurality of vertex angles, pitch intervals, or heights corresponding to the above ranges. In addition, the unit prisms of the prism sheet 101 of the present invention may be continuously arranged without gaps or may be arranged at regular intervals, and the unit prisms may be equally applied to a plurality of unit prisms.

As the material of the prism sheet 101, various known materials can be used. For example, polyolefin resins such as polyethylene and polypropylene, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, cyclic olefin resins such as polyvinyl chloride resins, polycarbonate resins and norbornene resins, poly Butadiene-styrene copolymer, acrylonitrile-styrene copolymer and the like, such as acrylic resin such as urethane resin and methyl methacrylate resin, polystyrene resin, methyl methacrylate-styrene copolymer, acrylonitrile-butadiene- A cellulose-based film such as polyacetyl cellulose, triacetylcellulose, etc. may be used. Among them, polyolefin resins, acrylic resins, polycarbonate resins, polyester resins, polystyrene resins, methyl methacrylate-styrene copolymers, acrylonitrile-butadiene-styrene Based copolymer, an acrylonitrile-based copolymer, and an acrylonitrile-styrene-based copolymer. If necessary, additives such as an ultraviolet absorber, an antioxidant and a plasticizer may be contained.

The prism sheet 101 can be formed by a known method such as a photopolymer process, a mold extrusion process, a press molding process, an injection molding process, a roll transfer process, a laser ablation process, a mechanical cutting process, a mechanical grinding process, Each of these methods may be used alone or in combination of two or more methods.

The thickness of the prism sheet 101 is not particularly limited, but is preferably in the range of 20 to 200 mu m, more preferably in the range of 30 to 100 mu m, for thinning the polarizing plate. The thickness of the prism sheet 101 at this time means the shortest distance from the flat surface (the surface opposite to the surface on which the unit prisms are formed) constituting one surface of the prism sheet 101 to the top of the unit prism.

The first pressure sensitive adhesive layer 103 of the present invention is a layer for bonding the prism sheet 101 and the protective film 105, and a known pressure sensitive adhesive may be used. For example, an acrylic pressure sensitive adhesive, a urethane pressure sensitive adhesive, . Among them, an acrylic pressure-sensitive adhesive is preferable from the viewpoints of transparency, adhesive strength, reliability, reworkability and the like.

For example, the first pressure sensitive adhesive layer 103 may include an acrylic pressure sensitive adhesive resin, a crosslinking agent, and a silane coupling agent.

As the acrylic pressure sensitive adhesive resin, the acrylic pressure sensitive adhesive resin is an acrylic copolymer, and a copolymer of a (meth) acrylate monomer having an alkyl group of 1 to 14 carbon atoms and a monomer having a crosslinkable functional group can be used. Here, (meth) acrylate means both "acrylate" and "methacrylate".

Specific examples of the (meth) acrylate monomer having 1 to 14 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, (Meth) acrylate, isobutyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth) acrylate, n-decyl (meth) acrylate, n-decyl (meth) acrylate, isononyl Acrylate, n-tetradecyl (meth) acrylate, pentafluorooctyl acrylate, and 6- (1-naphthyloxy) -1-hexyl acrylate. These may be used singly or in combination of two or more kinds. Can be used.

The (meth) acrylate monomer having 1 to 14 carbon atoms is preferably contained in an amount of 50 to 99% by weight based on the total monomer content (100% by weight) used in the production of the acrylic copolymer.

The monomer having a crosslinking functional group reacts with a crosslinking agent to give a cohesive force or a cohesive strength by chemical bonding so that the cohesive force of the pressure-sensitive adhesive does not break under high temperature or high humidity conditions. For example, a monomer having a sulfonic acid group, Containing monomer, an amino group-containing monomer, an imide group-containing monomer, an epoxy group-containing monomer, an ether group-containing monomer, and the like may be used in combination with a monomer having a carboxyl group, a cyano group-containing monomer, a vinyl ester, an aromatic vinyl compound, These may be used alone or in combination of two or more.

Examples of the sulfonic acid group-containing monomer include styrenesulfonic acid, allylsulfonic acid, 2- (meth) acrylamido-2-methylpropanesulfonic acid, (meth) acrylamidopropanesulfonic acid, sulfopropyl (meth) ) Acryloyloxynaphthalenesulfonic acid, sodium vinylsulfonate, and the like.

Examples of the phosphoric acid group-containing monomer include 2-hydroxyethyl acryloyl phosphate.

Examples of the cyano group-containing monomer include (meth) acrylonitrile.

Examples of the vinyl esters include vinyl acetate, vinyl propionate, and vinyl laurate.

Examples of the aromatic vinyl compound include styrene, chlorostyrene, chloromethylstyrene,? -Methylstyrene, and other substituted styrenes.

Examples of the carboxy group-containing monomer include (meth) acrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid and isocrotonic acid.

Examples of the acid anhydride-containing monomer include maleic anhydride, itaconic anhydride, and acid anhydrides thereof.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (Meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4-hydroxymethylcyclohexyl) (Meth) acrylamide, vinyl alcohol, allyl alcohol, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, diethylene glycol monovinyl ether and the like.

Examples of the amide group-containing monomer include (meth) acrylamide, diethylacrylamide, N-vinylpyrrolidone, N, N-dimethyl (meth) acrylamide, N, N'-methylenebisacrylamide, N, N-dimethylaminopropyl (meth) acrylamide, diacetone acrylamide and the like.

Examples of the amino group-containing monomer include aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, (meth) acryloylmorpholine, .

Examples of the imide group-containing monomer include cyclohexylmaleimide, isopropylmaleimide, N-cyclohexylmaleimide and itaconimide.

Examples of the epoxy group-containing monomer include glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, and allyl glycidyl ether.

Examples of the ether group-containing monomer include 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, butoxyethyl (meth) acrylate, phenoxyethyl And morpholine.

The above-mentioned monomer having a crosslinkable functional group is preferably contained in an amount of 1 to 50% by weight based on the total monomer content (100% by weight) used in the production of the acrylic copolymer.

The acrylic copolymer having the above components may be prepared by a conventional method such as a solution polymerization method, a photopolymerization method, a bulk polymerization method, a suspension polymerization method and an emulsion polymerization method, and is preferably prepared by a solution polymerization method.

The acrylic copolymer generally has a weight average molecular weight (in terms of polystyrene) measured by Gel Permeation Chromatography (GPC) of usually 50,000 to 2,000,000, preferably 100,000 to 1,800,000, more preferably 500,000 to 1,500,000 to be.

The crosslinking agent is an isocyanate compound, an epoxy compound, a melamine resin, an aziridine compound or the like which is used for enhancing the cohesive force of the pressure-sensitive adhesive composition by adequately crosslinking the acrylic copolymer, and preferably an isocyanate compound or an epoxy compound is used . These may be used alone or in combination of two or more.

Examples of the isocyanate compound include tolylene diisocyanate, xylene diisocyanate, hexamethylene diisocyanate, 2,4-diphenylmethane diisocyanate, 4,4-diphenylmethane diisocyanate, isophorone diisocyanate, tetramethyl xylene diisocyanate , Naphthalene diisocyanate, and the like.

Examples of the epoxy compound include ethylene glycol diglycidyl ether, triglycidyl ether, trimethylolpropane triglycidyl ether, N, N, N ', N'-tetraglycidyldiamine, glycerin diglycidyl ether, , 3-bis (N, N-diglycidylaminomethyl) cyclohexane, and the like.

Examples of the melamine resin include hexamethylol melamine.

Examples of the aziridine compound include N, N'-toluene-2,4-bis (1-aziridinecarboxamide), N, N'-diphenylmethane-4,4'- Id), triethylene melamine, bisisopropanoyl-1- (2-methyl aziridine), and tri-1-aziridinyl phosphine oxide.

The cross-linking agent is preferably contained in an amount of 0.01 to 15 parts by weight based on 100 parts by weight (based on the solids content) of the acrylic pressure-sensitive adhesive resin. If the content is less than the above range, the adhesive force or the cohesive force of the pressure sensitive adhesive is poor. If the content exceeds the above range, the compatibility may be reduced and the surface migration may occur.

The composition for forming the first pressure-sensitive adhesive layer 103 containing the above-mentioned components may further include a silane coupling agent as needed in order to improve adhesion when bonded to the liquid crystal cell or the substrate.

Specific examples of the silane coupling agent include vinyltrimethoxysilane, vinyltriethoxysilane, methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxy Silane, 3-mercaptopropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane , 3-aminopropyltrimethoxysilane and 3-chloropropyltrimethoxysilane. These may be used alone or in combination of two or more. The silane coupling agent may be contained in an amount of 0.005 to 5 parts by weight based on 100 parts by weight (based on the solids content) of the acrylic pressure-sensitive adhesive resin.

In addition, the composition may further comprise at least one additive selected from the group consisting of an epoxy resin, a curing agent, a UV stabilizer, an antioxidant, a colorant, a reinforcing agent, a filler, a defoamer, a surfactant and a plasticizer to the extent that the effect of the invention is not affected .

The method of forming the first pressure-sensitive adhesive layer 103 is not particularly limited. For example, the first pressure-sensitive adhesive layer 103 may be prepared by mixing the components described above to prepare a composition for forming a first pressure-sensitive adhesive layer, and then subjecting it to a suitable process substrate such as a prism sheet and / or a protective film using a bar coater or a comma coater And then curing it by means of the above-mentioned method. Also, the curing method of the composition for forming the first pressure-sensitive adhesive layer is not particularly limited. For example, the acrylic pressure-sensitive adhesive resin and the crosslinking agent may be aged at an appropriate temperature so that the crosslinking reaction can proceed.

The thickness of the first pressure-sensitive adhesive layer 103 is in the range of 5 to 50 mu m, preferably 10 to 35 mu m. By controlling the thickness to the above-mentioned range, it is possible to effectively prevent shrinkage or expansion even under severe conditions and to maintain excellent durability.

In the present invention, the structure between the prism sheet 101 and the first pressure-sensitive adhesive layer 103 has a structure as shown in Fig. Specifically, FIG. 2 (a) shows a state before bonding of the prism sheet 101 and the first pressure-sensitive adhesive layer 103, and FIG. 2 (b) shows a state after bonding the two layers. The vicinity of the apex angle of the unit prism of the prism sheet 101 partially penetrates into the first pressure sensitive adhesive layer 103 due to the surface shape of the prism sheet 101 and the physical properties of the first pressure sensitive adhesive layer 103, An air gap is formed between the first pressure sensitive adhesive layer 101 and the first pressure sensitive adhesive layer 103 and the air gap affects the brightness and durability of the polarizing plate as well as the occurrence of the moire pattern.

When the height of the unit prism is H and the depth of the unit prism penetrating the first pressure sensitive adhesive layer is p, the air gap height h is the difference between H and p, and the air gap ratio is given by the following equation 1, respectively.

[Equation 1]

(Where H is the height of the unit prism and h is the height of the air gap)

Particularly, since the airgap ratio is related to occurrence of moire pattern as described above, it is possible to improve the brightness of the polarizing plate by improving the generation of moire pattern by adjusting it to 50% or more, and to exhibit excellent durability. And preferably in the range of 75 to 100%.

At this time, the brightness improvement can be confirmed through the half of viewing angle. Herein, the half of viewing angle refers to a viewing angle at which the user can recognize an image at the front of the liquid crystal display device at an angle representing luminance corresponding to half of the highest luminance. The luminance improvement according to the present invention is shown in FIGS. 4 and 5. Referring to FIG. 4, it can be seen that the viewing angle is widened by about 7% or more on average.

The protective film 105 of the present invention is intended to reinforce the strength and optical properties of the polarizer described later. The polarizer to be described later is generally made of a hydrophilic resin such as polyvinyl alcohol and is generally vulnerable to moisture. In addition, since the polarizer is manufactured through a stretching process, deformation such as shrinkage tends to occur under the humidifying condition, thereby deteriorating the optical characteristics of the polarizing plate. A protective film 105 made of a material excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, etc. is used. For example, polyester films such as polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate and polybutylene terephthalate; Cellulose-based films such as diacetylcellulose and triacetylcellulose; Polycarbonate film; Acrylic films such as polymethyl (meth) acrylate and polyethyl (meth) acrylate; Styrene-based films such as polystyrene, acrylonitrile-styrene copolymer and the like. Further, polyolefin-based films such as polyethylene, polypropylene, cyclo-based or norbornene-structured polyolefins and ethylene propylene copolymers; Vinyl chloride film; Amide type films such as nylon and aromatic polyamide; Imidazole film; Polyethersulfone-based films; Sulfone based films; A polyethyl ketone-based film; Vinyl alcohol film; Polyoxymethylene-based films; And an epoxy-based film. These may be used alone or in combination of two or more of the resins for a film. The protective film 105 may be a cured layer formed of a thermosetting or photo-curable resin such as acrylic, urethane, acrylic-urethane, epoxy, or silicone. Among them, the protective film 105 is preferably a polyester film in consideration of the coating property of the first pressure-sensitive adhesive layer 103 described above.

The thickness of the protective film 105 is generally 1 to 200 占 퐉, preferably 5 to 100 占 퐉 in consideration of workability such as strength and handling properties and thin film properties.

If necessary, a functional surface treatment layer such as a hard coating layer, an antireflection layer, a diffusion or antiglare coating layer, an antiglare layer, and an antistatic layer may be further laminated on the other surface of the protective film 105 where the protective film 105 is not bonded to the polarizer .

The polarizer 109 of the present invention is an optical film that serves to convert incident natural light into a desired single polarization state (linearly polarized state), and a film made of a polyvinyl alcohol resin in which a dichroic dye is adsorbed and oriented can be used have.

The polyvinyl alcohol resin constituting the polarizer 109 can be produced by saponifying a polyvinyl acetate resin.

Examples of the polyvinyl acetate resin include copolymers of vinyl acetate and other monomers copolymerizable with vinyl acetate in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate. Specific examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, vinyl ethers, acrylamides having an ammonium group, and the like. The degree of saponification of the polyvinyl alcohol-based resin is usually about 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol resin may be denatured. For example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The degree of polymerization of the polyvinyl alcohol resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000.

The polarizer 109 is usually formed by a process of uniaxially stretching a polyvinyl alcohol film as described above, a process of staining and drawing a stretched polyvinyl alcohol film with a dichroic dye, a process of adsorbing a polyvinyl alcohol film adsorbed with a dichroic dye A step of treating the aqueous solution with an aqueous boric acid solution, and a step of washing with water. At this time, iodine or dichroic organic dyes can be used as the dichroic dye. The thickness of the finally obtained polarizer is generally in the range of 5 to 40 mu m.

The second pressure-sensitive adhesive layer (111) of the present invention is a layer for bonding with the liquid crystal cell, and is referred to in the first pressure-sensitive adhesive layer (103).

The second pressure sensitive adhesive layer 111 may further include a release film (not shown).

The release film is a film for protecting the pressure-sensitive adhesive layer, and the kind thereof is not particularly limited as long as it is a film ordinarily used in the art. Specific examples thereof include polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene-propylene copolymer, ethylene-1-butene copolymer, ethylene- A polyolefin-based film such as an ethylene-vinyl alcohol copolymer; Polyester films such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; Polyamide-based films such as polyacrylate, polystyrene, nylon-6, and partially aromatic polyamide; Polyvinyl chloride films; Polyvinylidene chloride films; Or a polycarbonate film. These may be appropriately subjected to a releasing treatment with a silicone type releasing agent, a fluorine type releasing agent, a silica powder or the like.

3 is a cross-sectional view illustrating a polarizing plate according to a second embodiment of the present invention.

3, a polarizing plate 100 according to the present invention includes a prism sheet 101, a diffusion adhesive layer 113, a protective film 105, a diffusion adhesive layer 107, a polarizer 109 and a second pressure- (111) are sequentially stacked.

Particularly, in the second embodiment, as shown in FIG. 3, a diffusion adhesive layer 113 is provided.

The diffusion pressure sensitive adhesive layer 113 includes particles having light diffusibility in addition to the first pressure sensitive adhesive layer 103 of the first embodiment. As described above, as the particles having light scattering ability are dispersed, generation of moire patterns caused by interference between the prism sheet and the repeated pattern of the liquid crystal cell is alleviated.

The diffusion adhesive layer 113 has a haze value in the range of 30 to 99%, preferably in the range of 40 to 97%. If the haze value is less than the above range, the light diffusion is reduced and a moire pattern is generated. On the other hand, when the haze value is out of the above range, the scattering angle is increased and the luminance is lowered.

The composition and the formation method of the diffusion pressure sensitive adhesive layer 113 are the same as those used in the first pressure sensitive adhesive layer of the first embodiment, and the particles follow the same as mentioned in the diffusion adhesive layer of the first embodiment.

Further, in the first embodiment and the second embodiment of the present invention, an adhesive layer and a protective film may be additionally provided between the polarizer 109 and the second pressure-sensitive adhesive layer 111.

The adhesive layer is for bonding a protective film to a polarizer, and can be formed by applying an adhesive composition on one surface of a polarizer and curing it by drying, heating, or irradiation with electromagnetic waves.

The specific kind that can be used for the adhesive layer is not particularly limited as long as it can be cured to exhibit desired adhesive properties. For example, a polyvinyl alcohol-based adhesive; Acrylic adhesive; Vinyl acetate based adhesive; Urethane based adhesives; Polyester-based adhesives; Polyolefin adhesives; Polyvinyl alkyl ether adhesives; Rubber adhesives; Vinyl chloride-vinyl acetate-based adhesive; Styrene-butadiene-styrene (SBS) adhesives; Hydrogenated styrene-butadiene-styrene (SEBS) based adhesives; Ethylenic adhesives; And acrylic ester-based adhesives, or a mixture of two or more thereof. The above-mentioned adhesive layer can be prepared, for example, by curing an aqueous, solvent-based or solvent-free adhesive composition. The adhesive layer may include a thermosetting, room temperature curing, moisture curing or photocurable adhesive composition in a cured state. Preferred examples of the adhesive layer include an aqueous polyvinyl alcohol-based adhesive composition; A solventless acrylic adhesive composition; Or an adhesive layer containing a solvent-free vinyl acetate-based adhesive composition in a cured state.

The thickness of the adhesive layer is not particularly limited, but is preferably in the range of 0.5 to 20 mu m.

The protective film is intended to prevent deterioration of the strength and physical properties of the polarizer, and is referred to in the first embodiment.

In this case, the cellulose-based film is preferably used in consideration of the polarizing property and durability of the polarizing plate in which the protective film is finally formed between the polarizer and the second pressure-sensitive adhesive layer. The protective film may be either a protective film or a retardation film serving as a retardation film, or a known retardation film laminated on a protective film.

The polarizing plate according to the present invention has a diffusion adhesive layer between the protective film and the polarizer and adjusts the airgap ratio in the bonding surface of the prism sheet and the first pressure sensitive adhesive layer to a certain range. In addition, a first pressure sensitive adhesive layer is provided as a diffusion pressure sensitive adhesive layer.

The polarizing plate has a diffusing adhesive layer containing particles having light scattering ability and a diffusion adhesive layer. The haze value of the layers is kept within a certain range, so that the direction of light can be changed to suppress the occurrence of moire patterns. The airgap ratio at the bonding surface of the first adhesive layer and the first adhesive layer is maintained at a predetermined level or higher so that the moiré pattern is not formed and the brightness and durability of the polarizing plate can be improved. Further, since the prism sheet is integrated with the polarizing plate without using a separate diffusion sheet, the entire thickness can be reduced compared to the conventional one when applied to a liquid crystal device.

In addition, when the polarizing plate of the present invention is applied to the upper, lower or upper and lower portions of the liquid crystal cell, the diffusion adhesive layer and / or the diffusion pressure sensitive adhesive layer are not formed between the polarizer of the upper polarizer and the polarizer of the lower polarizer, Polarized light is prevented from being polarized-diffused-polarized due to the fact that the light emitted from the backlight unit is located outside the polarizers, thereby reducing polarization and brightness.

The present invention also provides a liquid crystal display device including the polarizer.

The type of the liquid crystal cell included in the liquid crystal display device is not particularly limited. For example, the liquid crystal cell of the passive matrix type such as TN (twisted nematic) type, STN (super twisted nematic) type, F (ferroelectic) type or PD (polymer dispersed) type is used. An active matrix type liquid crystal cell such as a two terminal type or a three terminal type; Known liquid crystal cells such as an in-plane switching (IPS) panel and a vertical alignment (VA) liquid crystal cell can all be applied.

The types of the other constituent elements constituting the liquid crystal display device, for example, the types of the upper and lower substrates (e.g., color filter substrate or array substrate) are not particularly limited, and configurations known in this field are not limited .

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to be illustrative of the invention and are not intended to limit the scope of the claims. It will be apparent to those skilled in the art that such variations and modifications are within the scope of the appended claims.

Synthetic example  One

A four neck jacket reactor (1 L) was equipped with a stirrer, a thermometer, a reflux condenser, a dropping funnel and a nitrogen gas inlet tube. The reactor was purged with nitrogen gas and then reacted with 3,4-epoxycyclohexyl Methyl-3 ', 4'-epoxycyclohexanecarboxylate, 20 parts by weight of neopentyl glycol diglycidyl ether, 10 parts by weight of 2-ethylhexyl glycidyl ether, 10 parts by weight of triarylsulfonium hexafluorophosphate , And 500 parts by weight of a propylene carbonate solution were mixed and defoamed to prepare a photo-curable adhesive solution.

Synthetic example  2

A four neck jacket reactor (1L) was equipped with a stirrer, a thermometer, a reflux condenser, a dropping funnel, and a nitrogen gas introducing tube. The reactor was purged with nitrogen gas, 98 parts by weight of butylacrylate (n-BA), 0.5 part by weight of acrylic acid (AA) and 1.4 parts by weight of 2-hydroxyethyl acrylate (2-HEA) were charged and the temperature of the reactor was raised to 50.degree.

Then, a solution in which 0.1 part by weight of 2,2'-azobisisobutyronitrile (AIBN) was completely dissolved in 10 parts by weight of ethyl acetate was added dropwise to the reactor. The reaction was continued for an additional 5 hours while keeping the jacket temperature at 50. Then, 90 parts by weight of ethyl acetate was slowly added dropwise for 1 hour using a dropping funnel.

Then, the mixture was further reacted at the same temperature for 5 hours. When the reaction was completed, the reaction solution was diluted with ethyl acetate to obtain an acrylic copolymer solution having a solid content of 20%.

Manufacturing example  One: Diffusion adhesive layer  Composition for forming

A solution in which the content of polymethylmethacrylate particles (average particle diameter: 5 占 퐉, spherical) was dispersed in toluene solvent was added to 100 parts by weight of the photo-curing adhesive resin prepared in Synthesis Example 1, To prepare a composition for forming a diffusion adhesive layer.

Subsequently, the thus prepared composition for forming a diffusion adhesive layer was coated on one surface of a polyethylene terephthalate film (Toyobo Ester Film E7002, manufactured by Toyobama Co., Ltd.) with a coater (Barcoater, Daiichi Chemical Co., Ltd.) And the coating was cured to a thickness of 10 mu m.

Next, ultraviolet rays were irradiated by a "D valve" manufactured by Fusion UV Systems Co., Ltd. so that the accumulated light quantity became 3,000 mJ / cm 2, thereby curing the adhesive. This was cut into a size of 5 mm x 30 mm, and the polyethylene terephthalate film was peeled off to obtain a diffusion adhesive film.

The haze value of each of the diffusion adhesive films having different amounts of polymethylmethacrylate particles was measured using a haze meter (HZ-1, manufactured by Suga Test Instrument Co., Ltd.) according to JIS K 7361-1 And calculated by the following equation (2).

&Quot; (2) "

Manufacturing example  2: The spreading pressure-  Composition for forming

0.8 parts by weight of trimethylolpropane-modified tolylene diisocyanate (Coronate L, manufactured by Nippon Polyurethane Industry) as crosslinking agent, 100 parts by weight (based on solid content) of the acrylic copolymer resin prepared in Synthesis Example 2, A solution prepared by dispersing 0.15 part by weight of synglycidopropyltrimethoxysilane (KBM-403) and polymethylmethacrylate particles (average diameter: 5 탆, spherical shape, refractive index: 1.49) in a toluene solvent was added, And diluted with toluene to a concentration of 20% to prepare a pressure-sensitive adhesive composition.

Subsequently, the composition for forming a diffusion pressure-sensitive adhesive layer was coated on one surface of a polyethylene terephthalate film (Toyobo Ester Film E7002, Toyobama Co., Ltd.) with a coater (Barcoater, Daiichi Kagaku Co., Ltd.) And the coating was cured to a thickness of 10 mu m.

Next, a diffusion adhesive sheet was prepared by drying in a forced circulation type hot-air dryer of 100 oven for 3 minutes, and then a polyethylene terephthalate releasing film with a silicon release treatment was bonded thereto to prepare a diffusion adhesive transfer tape.

At this time, the haze value of each of the spreading pressure-sensitive adhesive transfer tapes differing in the content of polymethylmethacrylate particles was measured according to JIS K 7361-1 specification using a haze meter (HZ-1, manufactured by Suga Test Instrument Co., Ltd.) And calculated by the above-mentioned formula (2).

Example  1 to 14 and Comparative Example  1 to 3

≪ Examples 1 to 14 >

A corona discharge treatment was carried out on the surface of a triacetyl cellulose film having a thickness of 80 占 퐉 (Konica Kagaku KK8UX2MW, manufactured by Konica Minolta Opto Co., Ltd.), and the respective diffusion adhesives obtained in the above- The spreading pressure-sensitive adhesive was applied using a bar coater so that the film thickness after curing became 15 占 퐉.

Then, a polyvinyl alcohol-iodine polarizer having a thickness of 28 mu m was bonded to the formed diffusion adhesive layer. Next, a corona discharge treatment was performed on the surface of a 40 mu m thick retardation film (N-TAC KC4FR-1, manufactured by Konica Minolta Opto Co., Ltd.) comprising an acetylcellulose resin, and on the corona discharge treated surface, The photocurable adhesive solution containing no particles obtained in Example 1 was applied using a bar coater so that the film thickness after curing would be about 2 占 퐉. The same triacetylcellulose film as above was bonded to the adhesive layer to prepare a laminate. Ultraviolet rays were irradiated from the side of the acetylcellulose-based retardation film of this laminate using ultraviolet ray irradiating device (D valve, Fusion UV Systems Co., Ltd.) with a belt conveyor so that the accumulated light quantity became 250 mJ / cm 2 to cure the adhesive .

Thus, a polarizing plate having a diffusion adhesive layer and a diffusion pressure-sensitive adhesive layer was produced.

≪ Comparative Examples 1 to 3 >

Except that the diffusion-adhesive layer and the diffusion-adhesive layer of Example were replaced with a photo-curable adhesive and a pressure-sensitive adhesive which did not contain particles.

Experimental Example : evaluation

The properties of the polarizing plates prepared in the above Examples and Comparative Examples were measured by the following methods, and the results are shown in Table 1 below.

(1) moire pattern

The prepared polarizing plate is bonded to a lower plate polarizing plate of a liquid crystal cell, and a usual polarizing plate not including a diffusion adhesive layer is bonded to the upper plate polarizing plate of the liquid crystal cell, and then a reflecting plate, a light source, a diffusion plate, and a prism sheet are stacked Was laminated on the prism sheet of the backlight unit. Then, the generation intensity of the moire pattern caused by the prism sheet was visually observed and evaluated based on the following criteria.

<Standard>

◎: Moire pattern does not occur at all

○: Moire pattern slightly occurred

△: moire pattern partially occurs

X: The moire pattern appears clearly

(2) Airgap ratio

The polarizing plates prepared in Examples and Comparative Examples were cut to a size of 5 mm X 5 mm to prepare specimens. Microstructures were then cut to obtain a clean cross-sectional shape. SEM (S-4700; manufactured by Hitachi) The air gap of the prism sheet was measured, and the air gap ratio was calculated by the above formula (1).

(3) Half angle

The polarizing plates prepared in the examples and comparative examples were mounted on a backlight unit (BLU) for a 32-inch liquid crystal display panel and fixed at an omnidirectional angle emitted from the BLU to the front using a viewing angle measuring instrument (EZcontrast, manufactured by ELDIM France) And the half-value angle, which is an angle at which the luminance becomes 50% with respect to the front luminance (angle 0 DEG) with respect to the luminance emitted in the direction perpendicular to the longitudinal direction of the prism, was measured. At this time, the increase rate was calculated based on the value of Comparative Example 1 with respect to the measured half angle, and the obtained results are shown in Tables 1, 4 and 5 below.

Diffusion adhesive layer The spreading pressure- Moire pattern Airgap Half Price Increase Rate (%) T _p
(%) Hayes
(%) T _p
(%) Hayes
(%) H
(탆) H
(탆) Air gap ratio
(%) Example 1 50 45 91 0.1 △ 40 37 92.5 2 Example 2 37 60 91 0.1 ○ 40 37 92.5 2 Example 3 18 80 91 0.1 ○ 40 37 92.5 5 Example 4 9 90 91 0.1 ◎ 40 37 92.5 8 Example 5 5 95 91 0.1 ◎ 40 37 92.5 14 Example 6 37 60 91 0.1 ○ 40 30 75.0 4 Example 7 37 60 91 0.1 △ 40 20 50.0 5 Example 8 50 45 50 45 ○ 40 37 92.5 3 Example 9 37 60 37 60 ○ 40 37 92.5 4 Example 10 18 80 18 80 ◎ 40 37 92.5 8 Example 11 9 90 9 90 ◎ 40 37 92.5 16 Example 12 5 95 5 95 ○ 40 37 92.5 28 Example 13 37 60 37 60 ○ 40 30 75.0 5 Example 14 37 60 37 60 ◎ 40 20 50.0 5 Comparative Example 1 91 0.1 91 0.1 × 40 37 92.5 0 Comparative Example 2 91 0.1 91 0.1 × 40 30 75.0 2 Comparative Example 3 91 0.1 91 0.1 × 40 20 50.0 4

Referring to Table 1 above, Examples 1-7 with only a diffusion adhesive layer and Examples 8-12 with both a diffusion adhesive layer and a diffusion adhesive layer were compared to Comparative Examples 1 to 3 without two layers It was confirmed that the occurrence of the moire pattern was improved and the luminance was also improved.

The polarizing plate according to the present invention can be applied to a liquid crystal display device to suppress the occurrence of moire patterns and to realize a high quality image with improved polarization degree and brightness.

100: polarizer
101: prism sheet 103: first pressure-sensitive adhesive layer
105: protective film 107: diffusion adhesive layer
109: polarizer 111: second pressure-sensitive adhesive layer
113: spreading pressure-sensitive adhesive layer

Claims (11)

A prism sheet, a first pressure-sensitive adhesive layer, a protective film, an adhesive layer, a polarizer and a second pressure-sensitive adhesive layer,
Wherein the adhesive layer is a diffusion adhesive layer. The polarizing plate according to claim 1, wherein a haze value of the diffusion adhesive layer is in the range of 30 to 99%. The polarizer of claim 1, wherein the diffusion adhesive layer comprises particles having an average particle size in the range of 0.1 to 10 mu m. The polarizing plate according to claim 1, wherein the thickness of the diffusion adhesive layer is in the range of 0.5 to 20 μm. The polarizing plate according to claim 1, wherein the airgap ratio represented by the following formula (1) is at least 50% at the interface between the prism sheet and the first pressure-sensitive adhesive layer:
[Equation 1]

(Where H is the height of the unit prism and h is the height of the air gap) The polarizing plate according to claim 1, wherein the first pressure sensitive adhesive layer is a diffusion pressure sensitive adhesive layer. The polarizing plate according to claim 6, wherein a haze value of the diffusion pressure-sensitive adhesive layer is in the range of 30 to 99%. 7. The polarizing plate according to claim 6, wherein the diffusion pressure-sensitive adhesive layer comprises particles having an average particle diameter in the range of 0.1 to 20 mu m. The polarizing plate according to claim 6, wherein the thickness of the diffusion pressure-sensitive adhesive layer is in the range of 5 to 50 μm. The polarizing plate according to claim 1, further comprising an adhesive layer and a protective film between the polarizer and the second pressure-sensitive adhesive layer.  A liquid crystal display device comprising the polarizing plate of claim 1.

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