Polarizing plate and optical display device

Abstract

a polarizer; and a laminate of a first retardation layer, a first pressure-sensitive adhesive layer, and a second retardation layer laminated on one surface of the polarizer, wherein the first pressure-sensitive adhesive layer has an elastic modulus of 4×10 at 25° C. 4 Pa~10×10 4 The present invention provides a polarizing plate having a glass transition temperature of -60°C to -35°C at 10 Pa, and an optical display device including the polarizing plate.

Description

[Technical Field]

[0001] The present invention relates to a polarizing plate and an optical display device. [Background technology]

[0002] One example of an LCD device is one that has a liquid crystal layer in which liquid crystals are aligned in a horizontal alignment mode. Related to this are LCD devices of the IPS (in-plane switching) mode and FFS (fringe field switching) mode. A horizontal alignment mode LCD device aligns liquid crystals horizontally, and when two electrodes are driven on one substrate, the liquid crystals rotate in a plane to transmit or block light, improving the viewing angle.

[0003] In a horizontal alignment mode LCD device, if there is a pretilt in the liquid crystal alignment, there is a high possibility that anisotropy in the horizontal or vertical color or in the horizontal or vertical visibility occurs. Therefore, the amount of birefringence varies between the horizontal or vertical directions, which can lead to uneven horizontal or vertical visibility (viewing angle). To solve this, a polarizing plate with a retardation layer between the polarizer and the panel can be used. Generally, two or more retardation layers are included to solve the above problem.

[0004] However, two or more retardation layers may cause thickness unevenness between the upper and lower surfaces of the polarizer, and since retardation layers are generally manufactured by stretching, bending of the polarizer may occur. Bending is when the edges of the polarizer lift, which can cause light leakage.

[0005] The background art of the present invention is disclosed in Japanese Patent Application Laid-Open No. 2006-251659 and the like. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-251659 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a polarizer that provides diagonal compensation effect on the sides, including the left and right sides.

[0008] Another object of the present invention is to provide a polarizing plate that suppresses bending and light leakage at the edges. [Means for solving the problem]

[0009] One aspect of the present invention is a polarizing plate.

[0010] The polarizing plate includes a polarizer and a laminate of a first retardation layer, a first pressure-sensitive adhesive layer, and a second retardation layer laminated on one surface of the polarizer, and the first pressure-sensitive adhesive layer has a storage modulus of 4×10 at 25° C. 4 Pa~10×10 4 Pa and the glass transition temperature is -60°C to -35°C.

[0011] Another aspect of the present invention is an optical display device.

[0012] The optical display device comprises the polarizing plate of the present invention. [Effects of the Invention]

[0013] The present invention can provide a polarizer that provides diagonal compensation effect on the sides, including the left and right sides.

[0014] The present invention can provide a polarizing plate that suppresses bending and light leakage at the edges. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional view of a polarizing plate according to one embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of a polarizing plate according to another embodiment of the present invention. [Figure 3] FIG. 3 is a cross-sectional view of a polarizing plate according to still another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention may, however, be embodied in various different forms and should not be construed as limited to the embodiments set forth herein.

[0017] The terms used herein are merely used to describe exemplary embodiments and are not intended to limit the present invention. The singular expressions include the plural expressions unless the context clearly indicates a different meaning.

[0018] In the drawings, to clearly explain the present invention, parts that are not relevant to the explanation are omitted, and the same or similar components are designated by the same reference numerals throughout the specification. The length and size of each component in the drawings are for the purpose of explaining the present invention, and the present invention is not limited to the length and size of each component shown in the drawings.

[0019] In this specification, "upper" and "lower" are defined based on the drawings, and "upper" may be changed to "lower" and "lower" to "upper" depending on the viewpoint, and what is described as "on" or "on" may include not only directly on but also the case where another structure is interposed between them. On the other hand, what is described as "directly on," "directly on," "directly formed on," or "formed in direct contact with" means that there is no other structure interposed between them.

[0020] In this specification, the "in-plane retardation (Re)", "thickness direction retardation (Rth)", and "degree of biaxiality (NZ)" are represented by the following formulas A, B, and C:

[0021] [Formula A] Re=(nx-ny)×d

[0022] [Formula B] Rth=((nx+ny) / 2-nz)×d

[0023] [Formula C] NZ=(nx-nz) / (nx-ny)

[0024] (In the above formulas A, B, and C, nx, ny, and nz are the refractive index in the slow axis direction, the fast axis direction, and the thickness direction of the optical element, respectively, at the measurement wavelength, and d is the thickness (unit: nm) of the optical element.)

[0025] In this specification, unless otherwise specified, the in-plane retardation, thickness direction retardation, and degree of biaxiality are values ​​measured by transmitting light in the normal direction to the in-plane direction of the optical element.

[0026] When describing angles in this specification, "+" indicates a clockwise angle relative to the reference (0°), and "-" indicates a counterclockwise angle relative to the reference (0°).

[0027] In this specification, the "storage modulus" of the first pressure-sensitive adhesive layer is a value measured at 25°C by laminating a plurality of 15µm-thick first pressure-sensitive adhesive layers to prepare a specimen having a thickness of 600µm, a diameter of 8mm, and a circular cross section, and measuring the storage modulus of the specimen using an ARES (Advanced Rheometry Expansion System, TA instrument) in a temperature sweep test while increasing the temperature from 0°C to 150°C at a rate of 10°C / min under conditions of a frequency of 1Hz, a strain of 5%, and a normal force of 100N.

[0028] In this specification, the "glass transition temperature" of the first adhesive layer is a value measured using a DSC Discovery (TA Instruments) while heating 15 mg of the first adhesive layer to 100°C at a heating rate of 20°C / min in a nitrogen atmosphere (nitrogen flow rate: 50 mL / min), cooling to -80°C, and then heating to 100°C at a heating rate of 10°C / min.

[0029] In this specification, the "shrinkage force" of a polarizing plate can be measured by thermomechanical analysis (TMA) in accordance with the standard measurement method ASTM E 831. Specifically, the "shrinkage force" of a polarizing plate is measured by preparing a rectangular specimen of MD (machine direction) x TD (transverse direction) (30 mm x 3 mm), clamping both ends of the MD side of the rectangular specimen to a TMA jig, and then measuring the shrinkage force at 85°C for 3 hours.

[0030] In this specification, the "shrinkage rate" of a polarizing plate was calculated by preparing a square specimen of polarizer MD x polarizer TD (60mm x 60mm) and subjecting the specimen to a constant temperature high-temperature treatment at 60°C for 250 hours. The MD lengths of the specimen before and after the high-temperature treatment were measured using a dimension measuring machine, and the shrinkage rate was calculated according to the following formula.

[0031] [formula] Shrinkage ratio = |S1-S0| / S0 x 100

[0032] (In the above formula, S0 is the MD length of the specimen before high-temperature treatment, and S1 is the MD length of the specimen after high-temperature treatment)

[0033] In this specification, the "shrinkage rate" of the retardation layer or the protective layer is a value measured in substantially the same manner as when measuring the shrinkage rate of a polarizing plate, except that a retardation layer or a protective layer is used instead of a polarizing plate.

[0034] In this specification, the "shrinkage force" of the retardation layer or the protective layer is a value measured in substantially the same manner as when measuring the shrinkage force of a polarizing plate, except that a retardation layer or a protective layer is used instead of a polarizing plate.

[0035] As used herein, "(meth)acrylic" can mean acrylic or methacrylic.

[0036] In this specification, when a numerical range is stated, "X to Y" means X or more and Y or less.

[0037] When the polarizer of the present invention is applied to an optical display panel, particularly a liquid crystal panel with a horizontal alignment mode of liquid crystal, it provides a diagonal compensation effect on both the left or upper side and the right or lower side. The horizontal alignment mode of the liquid crystal can be an in-plane switching (IPS) mode or a fringe field sqitching (FFS) mode.

[0038] The polarizing plate of the present invention provides the effect of suppressing light leakage by preventing lifting at the edge of the polarizing plate by suppressing bending. The above-mentioned "bending" means warping, and refers to the edge of the polarizing plate lifting from the flat surface when the polarizing plate is placed on a flat surface. In one embodiment, bending can be measured when a laminate of the first retardation layer, the first adhesive layer, and the second retardation layer in the polarizing plate is placed on a flat surface, and the detailed measurement method will be described below.

[0039] The polarizing plate includes a polarizer and a laminate of a first retardation layer, a first pressure-sensitive adhesive layer, and a second retardation layer laminated on one surface of the polarizer, and the first pressure-sensitive adhesive layer has a storage modulus of 4×10 at 25° C. 4 Pa~10×10 4 Pa and the glass transition temperature is -60°C to -35°C.

[0040] Polarizer The polarizer includes a light-absorbing polarizer that has the function of separating incident light into two orthogonal polarized components, transmitting one polarized component, and absorbing the other polarized component.

[0041] In one embodiment, the axis with the higher refractive index in the in-plane direction of the polarizer is the polarizer's light absorption axis (e.g., the polarizer's mechanical direction (MD, machine direction)), and the axis with the lower refractive index is the polarizer's light transmission axis (e.g., the polarizer's transverse direction (TD, transverse direction)).

[0042] The degree of polarization of the polarizer can be 95% or more, specifically 95% to 100%, more specifically 98% to 100%. Within this range, the polarizing plate has an excellent diagonal compensation effect.

[0043] The polarizer may include a uniaxially stretched polarizer containing a dichroic dye. Specifically, the polarizer containing a dichroic dye may include a polarizer manufactured by uniaxially stretching a polarizer substrate film in the MD direction and dyeing it with a dichroic dye (e.g., containing iodine or potassium iodide as an iodine-containing substance). The polarizer substrate film may include, but is not limited to, a polyvinyl alcohol film or a derivative thereof. The polarizer may be manufactured by a conventional method known to those skilled in the art.

[0044] The polarizer can have a thickness of 1 μm to 40 μm, specifically 15 μm to 30 μm, and more specifically 16 μm to 20 μm. A thickness in this range can be used for a polarizing plate.

[0045] First retardation layer and second retardation layer The first retardation layer and the second retardation layer are laminated on one side of the polarizer, preferably on the side of the polarizer where internal light is incident, thereby providing a diagonal compensation effect on both sides, including the left or upper side and the right or lower side. The "internal light" refers to light that is emitted from a backlight unit, passes through a liquid crystal panel, and then enters the polarizer.

[0046] In one specific example, the first retardation layer and the second retardation layer may be stacked in this order from the bottom surface of the polarizer. In another specific example, the second retardation layer and the first retardation layer may be stacked in this order from the bottom surface of the polarizer. Preferably, the first retardation layer and the second retardation layer are stacked in this order from the bottom surface of the polarizer, thereby further improving the bending and diagonal compensation effects of the present invention.

[0047] The first retardation layer is a positive C layer and can satisfy the relationship of nz>nx≒ny refractive index. The first retardation layer can have a thickness direction retardation at a wavelength of 550 nm of -110 nm to -50 nm, for example, -110 nm, -105 nm, -100 nm, -95 nm, -90 nm, -85 nm, -80 nm, -75 nm, -70 nm, -65 nm, -60 nm, -55 nm, or -50 nm, for example, -110 nm to -60 nm or -90 nm to -65 nm. Within this range, a diagonal compensation effect can be easily provided.

[0048] The first retardation layer can have an in-plane retardation at a wavelength of 550 nm of −10 nm to 10 nm, preferably 0 nm to 5 nm. Within this range, the above-mentioned thickness direction retardation can be easily provided.

[0049] The second retardation layer is a positive A retardation layer and can satisfy the relationship of refractive index nx>ny≒nz. The second retardation layer can have an in-plane retardation at a wavelength of 550 nm of 100 nm to 150 nm, for example, 100 nm, 105 nm, 110 nm, 115 nm, 120 nm, 125 nm, 130 nm, 135 nm, 140 nm, 145 nm, or 150 nm, preferably 110 nm to 130 nm. Within this range, diagonal compensation effect can be easily provided.

[0050] The second retardation layer may have a thickness direction retardation of 50 nm to 80 nm, for example, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, or 80 nm, preferably 55 nm to 70 nm, at a wavelength of 550 nm. Within this range, a diagonal compensation effect can be easily provided.

[0051] The second retardation layer may have a degree of biaxiality at a wavelength of 550 nm of 0.9 to 1.2, for example, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, or 1.2, preferably 0.95 to 1.1. This range can help provide a diagonal compensation effect.

[0052] The first retardation layer may be a liquid crystal layer or a non-liquid crystal layer.

[0053] When the first retardation layer is a liquid crystal layer, the first retardation layer can be formed by coating a liquid crystal layer composition on a substrate film or the like, followed by drying and curing. The first retardation layer in the form of a liquid crystal layer can be manufactured without a process such as stretching, and therefore bending of the polarizing plate can be easily suppressed. The liquid crystal layer composition can be formed using a conventional liquid crystal layer composition known to those skilled in the art. For example, the liquid crystal layer composition can be a nematic or discotic liquid crystal.

[0054] When the first retardation layer is a non-liquid crystal layer, the first retardation layer can be formed by coating a composition for a non-liquid crystal layer on a substrate film or the like, followed by drying and curing. The first retardation layer in the form of a non-liquid crystal layer is a non-stretched coating layer and is manufactured without a process such as stretching, so bending of the polarizing plate can be easily suppressed.

[0055] The composition forming the first retardation layer as an unstretched coating layer can contain, for example, a cellulose-based resin such as a cellulose ester-based resin or a cellulose ether-based resin, a polystyrene-based resin, an oligomer, or a compound such as a monomer.

[0056] The cellulose-based compound may contain at least units in which at least some of the hydrogen atoms (H) of the hydroxyl groups (OH) of the sugar monomers constituting cellulose (C2 hydroxyl group, C3 hydroxyl group, or C6 hydroxyl group) are substituted with acyl groups or ether groups. In other words, the cellulose-based compound may contain one or more of cellulose ester polymers and cellulose ether polymers.

[0057] For example, the cellulose-based polymer may include a cellulose ester-based polymer containing at least a unit in which at least some of the hydrogen atoms (H) of the hydroxyl groups (OH) of the sugar monomers constituting cellulose [the hydroxyl group at C2, the hydroxyl group at C3, or the hydroxyl group at C6] are substituted with acyl groups, as represented by the following formula 1: In this case, the acyl groups may be substituted or unsubstituted.

[0058] [ka] (1)

[0059] (In the above formula 1, n is an integer of 1 or more)

[0060] Substituents for the cellulose ester or acyl groups can each include one or more of halogen, nitro, alkyl (e.g., alkyl groups having 1 to 20 carbon atoms), alkenyl (e.g., alkenyl groups having 2 to 20 carbon atoms), cycloalkyl (e.g., cycloalkyl groups having 3 to 10 carbon atoms), aryl (e.g., aryl groups having 6 to 20 carbon atoms), heteroaryl (e.g., aryl groups having 3 to 10 carbon atoms), alkoxy (e.g., alkoxy groups having 1 to 20 carbon atoms), acyl, and halogen-containing functional groups. The substituents may be the same or different.

[0061] As known to those skilled in the art, the "acyl" can be RC(=O)-* (* is a linking symbol, and R is an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an arylalkyl group having 7 to 20 carbon atoms). The "acyl" is bonded to the cellulose ring through an ester bond (via an oxygen atom) in cellulose.

[0062] The "alkyl", "alkenyl", "cycloalkyl", "aryl", "heteroaryl", "alkoxy", and "acyl" are each, for convenience, non-halogen-based. The composition for the first retardation layer may contain the cellulose ester alone or a mixture of the cellulose esters.

[0063] The "halogen" means fluorine (F), Cl, Br or I, and preferably F.

[0064] The "halogen-containing functional group" may be an organic functional group containing one or more halogens, and may include an aromatic, aliphatic, or alicyclic functional group. For example, the halogen-containing functional group may be a halogen-substituted alkyl group having 1 to 20 carbon atoms, a halogen-substituted alkenyl group having 2 to 20 carbon atoms, a halogen-substituted alkynyl group having 2 to 20 carbon atoms, a halogen-substituted cycloalkyl group having 3 to 10 carbon atoms, a halogen-substituted alkoxy group having 1 to 20 carbon atoms, a halogen-substituted acyl group, a halogen-substituted aryl group having 6 to 20 carbon atoms, or a halogen-substituted arylalkyl group having 7 to 20 carbon atoms, but is not limited thereto.

[0065] The "halogen-substituted acyl group" can be R'-C(=O)-* (* is a linking symbol, and R' is a halogen-substituted alkyl group having 1 to 20 carbon atoms, a halogen-substituted cycloalkyl group having 3 to 20 carbon atoms, a halogen-substituted aryl group having 6 to 20 carbon atoms, or a halogen-substituted arylalkyl group having 7 to 20 carbon atoms). The "halogen-substituted acyl group" is bonded to the cellulose ring through an ester bond (via an oxygen atom) in cellulose.

[0066] Cellulose ester polymers can be prepared by the usual methods known to those skilled in the art, or can be purchased and used as commercially available products.For example, cellulose ester polymers having acyl as a substituent can be prepared by reacting trifluoroacetic acid or trifluoroacetic anhydride with the sugar monomer or sugar monomer polymer that constitutes the cellulose of the above formula 1, or by reacting trifluoroacetic acid or trifluoroacetic anhydride and then further reacting with an acylating agent (for example, carboxylic acid anhydride or carboxylic acid), or by reacting trifluoroacetic acid or trifluoroacetic anhydride and an acylating agent together, and then polymerizing.

[0067] The polystyrene polymer may include repeat units of formula 2:

[0068] [ka] (2)

[0069] (In the above formula 2, JPEG2025538847000004.jpg417 is the linkage site, R 1 ,R 2 ,R 3 are each independently a hydrogen atom, an alkyl group, a substituted alkyl group, or a halogen; R are each independently an alkyl, substituted alkyl, halogen, hydroxy, carboxy, nitro, alkoxy, amino, sulfonate, phosphate, acyl, acyloxy, phenyl, alkoxycarbonyl, or cyano group; and n is an integer of 0 to 5.

[0070] The polystyrene-based polymer may contain a halogen, i.e., a halogenated polystyrene-based polymer. 1 ,R 2 ,R 3 may be halogen and / or at least one R may be halogen. In one embodiment, halogen refers to fluorine (F), Cl, Br or I, preferably F.

[0071] The halogen-containing polystyrene polymer can be formed by polymerizing a mixture containing at least one of 1-(2,2-difluoroethenyl)-2-fluorobenzene and 1',2',2'-trifluorostyrene, for example. The mixture can further contain styrene.

[0072] The first retardation layer may have a thickness of 1 μm to 10 μm, specifically 2 μm to 7 μm, specifically 3 μm to 5 μm. Within this range, it can be used in a polarizing plate and can help improve the bending prevention effect.

[0073] The second retardation layer may be thicker than the first retardation layer. The second retardation layer may have a larger shrinkage rate and / or shrinkage force than the first retardation layer. In this case, it is easy to improve the bending prevention.

[0074] The second retardation layer may have a thickness of 20 μm to 80 μm, specifically 30 μm to 60 μm. Within this range, it can be used in a polarizing plate and can help improve the anti-bending effect.

[0075] The second retardation layer may have a shrinkage force of 0.04 N to 0.1 N, for example, 0.04 N, 0.05 N, 0.06 N, 0.07 N, 0.08 N, 0.09 N, or 0.1 N, specifically 0.05 N to 0.07 N. The second retardation layer may have a shrinkage ratio of 0.15% to 0.30%, specifically 0.18% to 0.25%. Within this range, even if the second retardation layer shrinks due to heat, it can maintain a retardation value that compensates for the diagonal angle.

[0076] The second retardation layer may be a stretched film of a non-liquid crystal layer. This may be advantageous in increasing the in-plane retardation at a wavelength of 550 nm compared to the first retardation layer. In one specific example, the second retardation layer may be an unstretched film for the second retardation layer that has been uniaxially stretched in the MD or TD, biaxially stretched in the MD and TD, or tilt-stretched. Preferably, the second retardation layer may be an unstretched film for the second retardation layer that has been uniaxially stretched in the MD. For example, the second retardation layer may be produced by dry- or wet-stretching the unstretched film for the second retardation layer at a stretch ratio of 5 to 8 times, but is not limited thereto.

[0077] The second retardation layer has a slow axis and a fast axis in the in-plane direction, and the slow axis of the second retardation layer can be substantially parallel to the light absorption axis of the polarizer. The term "substantially parallel" means that, when the light absorption axis of the polarizer is 0°, the slow axis of the second retardation layer is -5° to +5°, preferably -1° to +1°, and more preferably 0°. This can easily achieve the diagonal compensation effect of the polarizing plate. The first adhesive layer described below can easily improve bending of a polarizing plate having the above-mentioned axial relationship.

[0078] The second retardation layer may contain a polymer with positive intrinsic birefringence. Positive intrinsic birefringence means that the refractive index in the stretched direction (MD) increases. For example, the second retardation layer may be a norbornene-based material such as a cyclic olefin polymer (COP) or a cyclic olefin copolymer (COC), or a cellulose-based material such as triacetyl cellulose (TAC).

[0079] The shrinkage force and / or shrinkage rate of the second retardation layer can be realized by adjusting the material for the second retardation layer, the stretching ratio, stretching temperature, thickness, etc. when stretching the unstretched film for the second retardation layer when manufacturing the second retardation layer, and methods for adjusting this are well known to those skilled in the art. In one specific example, the second retardation layer can be manufactured by melt-extruding a composition for the second retardation layer to manufacture an unstretched film and then stretching it, or by manufacturing an unstretched film by a solution casting method and then stretching it.

[0080] The present invention provides two retardation layers (first retardation layer and second retardation layer) laminated on the lower surface of a polarizer. When the first retardation layer and the second retardation layer have different shrinkage rates and / or shrinkage forces, the first adhesive layer having a storage modulus and glass transition temperature within a specific range is provided between the first retardation layer and the second retardation layer to improve bending of the polarizer. In particular, when the second retardation layer has a larger shrinkage rate and / or shrinkage force than the first retardation layer and is located farther away from the polarizer than the first retardation layer, the first adhesive layer is effective in improving bending of the polarizer.

[0081] 1st adhesive layer The first pressure-sensitive adhesive layer is directly laminated on the first retardation layer and the second retardation layer, respectively. Here, "directly laminated" means that no other optical layer, another first pressure-sensitive adhesive layer, or another adhesive layer is laminated between the first retardation layer and the first pressure-sensitive adhesive layer, or between the second retardation layer and the first pressure-sensitive adhesive layer. As a result, the laminate of the first retardation layer, the first pressure-sensitive adhesive layer, and the second retardation layer may be a three-layer laminate.

[0082] The first adhesive layer has a storage modulus of 4×10 at 25°C. 4 Pa~10×10 4The storage modulus and glass transition temperature are -60°C to -35°C at 25°C. When the first pressure-sensitive adhesive layer satisfies both of the above-mentioned storage modulus and glass transition temperature range at 25°C, it acts as an interlayer pressure-sensitive adhesive between the first retardation layer and the second retardation layer to reduce shrinkage, thereby improving bending of a polarizing plate in which the first retardation layer and the second retardation layer are laminated on the lower surface of a polarizer.

[0083] Even if the first pressure-sensitive adhesive layer satisfies the elastic modulus of the present invention, if the glass transition temperature is less than -60°C, the effect of improving bending of the polarizing plate may be slight, and it may be difficult to bond the first retardation layer and the second retardation layer together. Even if the first pressure-sensitive adhesive layer satisfies the elastic modulus of the present invention, if the glass transition temperature is higher than -35°C, the effect of improving bending of the polarizing plate may be slight, and the adhesive strength of the first pressure-sensitive adhesive layer may be low, making it difficult to bond the first retardation layer and the second retardation layer together.

[0084] Even if the first pressure-sensitive adhesive layer satisfies the glass transition temperature of the present invention, the modulus of elasticity at 25°C is 4 × 10 4 If the elastic modulus is less than 10×10 Pa, the effect of improving the bending of the polarizing plate may be slight, or it may be difficult to bond the first retardation layer and the second retardation layer. 4 If the Pa exceeds this value, the effect of improving the bending of the polarizing plate may be slight, or the first pressure-sensitive adhesive layer may be too hard, making it difficult to bond the first retardation layer and the second retardation layer together.

[0085] Preferably, the first pressure-sensitive adhesive layer has an elastic modulus of 5×10 at 25° C. 4 Pa~9×10 4 At this temperature, the glass transition temperature may be −50° C. to −40° C. Within this range, the effect of improving bending of the polarizing plate may be excellent, and the production of the first pressure-sensitive adhesive layer may be facilitated.

[0086] The thickness of the first pressure-sensitive adhesive layer may be greater than that of the first retardation layer and smaller than that of the second retardation layer. For example, the thickness of the first pressure-sensitive adhesive layer may be 5 μm to 30 μm, preferably 10 μm to 20 μm. A thickness in this range can be used in a polarizing plate.

[0087] The composition of the first adhesive layer is not limited as long as it can achieve the above-mentioned range of elastic modulus and glass transition temperature at 25°C. Preferably, the first adhesive layer is a thermosetting adhesive, preferably a pressure-sensitive adhesive (PSA). The pressure-sensitive adhesive can easily achieve the above-mentioned range of elastic modulus and glass transition temperature at 25°C. Preferably, the first adhesive layer can be a (meth)acrylic adhesive layer. In this case, it can easily achieve the above-mentioned range of elastic modulus and glass transition temperature at 25°C.

[0088] In one specific example, the first pressure-sensitive adhesive layer can be formed from a composition for the first pressure-sensitive adhesive layer, which includes a (meth)acrylic pressure-sensitive adhesive resin and a curing agent.

[0089] The (meth)acrylic adhesive resin may include a (meth)acrylic copolymer of a monomer mixture including a (meth)acrylic monomer having an alkyl group and a (meth)acrylic monomer having a crosslinkable functional group.

[0090] The (meth)acrylic monomer having an alkyl group may be an unsubstituted (meth)acrylate having a straight-chain or branched-chain alkyl group having 1 to 20 carbon atoms at the ester moiety, and may include one or more of methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, iso-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, iso-octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, and dodecyl (meth)acrylate.

[0091] The (meth)acrylic monomer having a crosslinkable functional group can include one or more of a (meth)acrylic monomer having a hydroxyl group and a (meth)acrylic monomer having a carboxylic acid group. Preferably, the (meth)acrylic monomer having a hydroxyl group is included as the (meth)acrylic monomer having a crosslinkable functional group, thereby increasing the adhesive strength of the first pressure-sensitive adhesive layer through reaction with a curing agent.

[0092] The (meth)acrylic monomer having a hydroxyl group may be a (meth)acrylate having an alkyl group having 1 to 20 carbon atoms and one or more hydroxyl groups at the ester moiety. Specifically, the (meth)acrylic monomer having a hydroxyl group may include one or more of 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, and 1-chloro-2-hydroxypropyl (meth)acrylate. The monomers may be contained alone or in combination of two or more in the monomer mixture.

[0093] The monomer mixture contains 60% by weight to 99% by weight of a (meth)acrylic monomer having an alkyl group, for example, 60% by weight, 61% by weight, 62% by weight, 63% by weight, 64% by weight, 65% by weight, 66% by weight, 67% by weight, 68% by weight, 69% by weight, 70% by weight, 71% by weight, 72% by weight, 73% by weight, 74% by weight, 75% by weight, 76% by weight, 77% by weight, 78% by weight, 79% by weight, 80% by weight, 81% by weight, 82% by weight, 83% by weight, 84% by weight, 85% by weight, 86% by weight, 87% by weight, 88% by weight, 89% by weight, 90% by weight, 91% by weight, 92% by weight, 93% by weight, 94% by weight, 95% by weight, 96% by weight, 97% by weight, 98% by weight, 99% by weight, preferably 80% by weight to 99% by weight. 9% by weight of a (meth)acrylic monomer having a crosslinkable functional group, and 1% to 40% by weight, for example, 1% by weight, 2% by weight, 3% by weight, 4% by weight, 5% by weight, 6% by weight, 7% by weight, 8% by weight, 9% by weight, 10% by weight, 11% by weight, 12% by weight, 13% by weight, 14% by weight, 15% by weight, 16% by weight, 17% by weight, 18% by weight, 19% by weight, 20% by weight, 21% by weight, 22% by weight, 23% by weight, 24% by weight, 25% by weight, 26% by weight, 27% by weight, 28% by weight, 29% by weight, 30% by weight, 31% by weight, 32% by weight, 33% by weight, 34% by weight, 35% by weight, 36% by weight, 37% by weight, 38% by weight, 39% by weight, 40% by weight, preferably 1% to 20% by weight. Within this range, the elastic modulus and glass transition temperature at 25° C. of the first adhesive layer may be easily achieved.

[0094] The total amount of the (meth)acrylic monomer having an alkyl group and the (meth)acrylic monomer having a crosslinkable functional group in the monomer mixture may be 90% by weight or more, for example, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100%, 95% to 100%, or 100% by weight. Within this range, the effects of the present invention may be easily realized.

[0095] The (meth)acrylic copolymer can be produced using conventional methods known to those skilled in the art.

[0096] The curing agent may include one or more of an isocyanate-based curing agent, an epoxy-based curing agent, a metal chelate-based curing agent, an aziridine-based curing agent, and a carbodiimide-based curing agent as a thermal curing agent, and preferably, an isocyanate-based curing agent may be used as the curing agent.

[0097] Isocyanate-based curing agents include toluene diisocyanates such as hexamethylene diisocyanate, 2,4-toluene diisocyanate, and 2,6-toluene diisocyanate, 4,4'-methylenediphenyl diisocyanate, 1,3-xylylene diisocyanate, and 1,4-xylylene diisocyanate, hydrogenated toluene diisocyanate, isophorone diisocyanate, 1,3-bisisocyanate methylcyclohexane, tetramethylxylene diisocyanate, and 1 ,5-naphthalene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, trimethylolpropane toluene diisocyanate adducts including trimer adducts of trimethylolpropane / toluene diisocyanate, xylylene diisocyanate adducts of trimethylolpropane, triphenylmethane triisocyanate, methylene bis triisocyanate, and other adducts of the above-mentioned isocyanate-based curing agents.

[0098] The curing agent may be contained in an amount of 0.01 to 0.1 parts by weight, for example, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.1 parts by weight, preferably 0.02 to 0.06 parts by weight, relative to 100 parts by weight of the (meth)acrylic adhesive resin. Within this range, the elastic modulus and glass transition temperature of the first adhesive layer at 25°C can be easily achieved.

[0099] The composition may further include a silane coupling agent. Conventional silane coupling agents known to those skilled in the art may be used, and may include, for example, one or more of acetylacetonate-based, acetoacetate-based, and epoxy-based silane coupling agents. The silane coupling agent may be included in an amount of 0.1 to 1 part by weight, specifically 0.1 to 0.5 parts by weight, per 100 parts by weight of the (meth)acrylic adhesive resin. Within this range, the adhesive strength of the first adhesive layer can be further improved.

[0100] The composition for the first pressure-sensitive adhesive layer may be solvent-free. Alternatively, the composition for the first pressure-sensitive adhesive layer may further contain a solvent. When the composition contains a solvent, the first pressure-sensitive adhesive layer can be made thin and its coatability can be improved. Conventional solvents known to those skilled in the art can be used as the solvent. For example, the solvent may include one or more of methyl ethyl ketone, ethyl acetate, and toluene.

[0101] The first pressure-sensitive adhesive layer can be produced by a conventional method known to those skilled in the art, for example, by applying a composition for the first pressure-sensitive adhesive layer to one surface of a substrate film to a predetermined thickness, followed by drying and aging.

[0102] The polarizing plate may further include a first protective layer between the polarizer and the first retardation layer or between the polarizer and the second retardation layer. The first protective layer may include one or more layers in the polarizing plate.

[0103] 1st protective layer The first protective layer may be laminated on the lower surface of the polarizer to increase the mechanical strength of the polarizer, or may serve as a substrate film for forming the first retardation layer.

[0104] The first protective layer may have an in-plane retardation of 10 nm or less, for example, 0 to 10 nm, or 0 to 5 nm, at a wavelength of 550 nm, which may not affect the diagonal compensation effect of the first and second retardation layers.

[0105] The first protective layer may have a lower shrinkage rate and / or a lower shrinkage force than the second retardation layer. The first protective layer may be disposed closer to the polarizer than the first retardation layer and the second retardation layer. This may further improve the bending suppression effect of the polarizing plate.

[0106] In one specific example, the first protective layer may have a contraction force of 0.05 N to 1.0 N, for example, 0.05 N, 0.1 N, 0.2 N, 0.3 N, 0.4 N, 0.5 N, 0.6 N, 0.7 N, 0.8 N, 0.9 N, or 1.0 N, specifically 0.1 N to 0.5 N. Within this range, it is easy to provide an improvement in bending. The first protective layer may have a contraction rate of 0.05% to 0.20%, for example, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, 0.11%, 0.12%, 0.13%, 0.14%, 0.15%, 0.16%, 0.17%, 0.18%, 0.19%, or 0.20%, specifically 0.10% to 0.15%. Within this range, it is easy to provide an improvement in bending.

[0107] The first protective layer can have a thickness of 25 μm to 80 μm, preferably 30 μm to 60 μm. A thickness in this range can be used in a polarizing plate.

[0108] The first protective layer may be a coating layer or film of a liquid crystal layer or a non-liquid crystal layer. For example, the first protective layer may be an optically transparent film. Specifically, the first protective layer may be a film made of one or more resins selected from the group consisting of cellulose-based resins including triacetyl cellulose (TAC) and the like, polyester-based resins including polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate (PEN), polybutylene naphthalate and the like, cyclic polyolefin-based resins, polycarbonate-based resins, polyethersulfone-based resins, polysulfone-based resins, polyamide-based resins, polyimide-based resins, polyolefin-based resins, polyarylate-based resins, polyvinyl alcohol-based resins, polyvinyl chloride-based resins, and polyvinylidene chloride-based resins.

[0109] The first protective layer can be attached to the polarizer by an adhesive layer or a pressure-sensitive adhesive layer. The adhesive layer or the pressure-sensitive adhesive layer can be formed of a thermosetting or photocurable adhesive composition. The thickness of the adhesive layer or the pressure-sensitive adhesive layer can be 1 μm to 30 μm, for example, 2 μm to 10 μm, or 2 μm to 3 μm.

[0110] A second pressure-sensitive adhesive layer can be further laminated between the first protective layer and the first retardation layer.

[0111] 2nd adhesive layer The second pressure-sensitive adhesive layer can increase the strength of the polarizing plate by adhering the first protective layer and the first retardation layer, or the first protective layer and the second retardation layer, to each other.

[0112] The second pressure-sensitive adhesive layer can be formed from a composition for the second pressure-sensitive adhesive layer containing a (meth)acrylic pressure-sensitive adhesive resin and a curing agent.

[0113] The (meth)acrylic adhesive resin may include a (meth)acrylic copolymer of a monomer mixture including a (meth)acrylic monomer having an alkyl group and a (meth)acrylic monomer having a crosslinkable functional group.

[0114] The specific types of the (meth)acrylic monomer having an alkyl group, the (meth)acrylic monomer having a crosslinkable functional group, and the curing agent are the same as those described for the first pressure-sensitive adhesive layer.

[0115] The monomer mixture can contain 60% to 99% by weight, preferably 80% to 99% by weight, of a (meth)acrylic monomer having an alkyl group, and 1% to 40% by weight, preferably 1% to 20% by weight, of a (meth)acrylic monomer having a crosslinkable functional group. Within these ranges, the adhesive strength of the second pressure-sensitive adhesive layer can be ensured.

[0116] The curing agent may be contained in an amount of 0.01 to 0.1 parts by weight, preferably 0.02 to 0.06 parts by weight, per 100 parts by weight of the (meth)acrylic adhesive resin. Within this range, the adhesive strength of the second adhesive layer can be easily ensured.

[0117] The composition may further include a silane coupling agent. Typical silane coupling agents known to those skilled in the art may be used, and may include, for example, one or more of acetylacetonate-based, acetoacetate-based, and epoxy-based silane coupling agents. The silane coupling agent may be included in an amount of 0.1 to 1 part by weight, specifically 0.1 to 0.5 parts by weight, per 100 parts by weight of the (meth)acrylic adhesive resin. Within this range, the adhesive strength of the second adhesive layer can be further improved.

[0118] The composition for the second pressure-sensitive adhesive layer may be solvent-free. Alternatively, the composition for the second pressure-sensitive adhesive layer may further contain a solvent. When the composition contains a solvent, the second pressure-sensitive adhesive layer can be made thin and its coatability can be improved. Conventional solvents known to those skilled in the art can be used as the solvent. For example, the solvent may include one or more of methyl ethyl ketone, ethyl acetate, and toluene.

[0119] The second pressure-sensitive adhesive layer may have a thickness of 15 μm to 35 μm, specifically 20 μm to 30 μm. With a thickness in this range, it can be used in a polarizing plate.

[0120] The polarizing plate may further include a second protective layer laminated on another surface of the polarizer, and the second protective layer may include one or more layers in the polarizing plate.

[0121] 2nd protective layer The second protective layer is disposed on the light exit surface of the internal light polarizer and acts on the light exiting from the polarizer, thereby improving image quality and protecting the polarizer.

[0122] The second protective layer can include a protective film or a protective coating layer.

[0123] The protective film may be an optically transparent film, such as a film made of one or more resins, including cellulose-based films including triacetyl cellulose (TAC), polyester-based films including polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate (PEN), and polybutylene naphthalate, cyclic polyolefin-based films, polycarbonate-based films, polyethersulfone-based films, polysulfone-based films, polyamide-based films, polyimide-based films, polyolefin-based films, polyarylate-based films, polyvinyl alcohol-based films, polyvinyl chloride-based films, and polyvinylidene chloride-based films. Specifically, TAC and PET films may be used. The protective coating layer may be formed from one or more of a thermosetting coating layer composition and a photocurable coating layer composition.

[0124] In one embodiment, the second protective layer may be a retardation film.

[0125] In one specific example, the second protective layer has an in-plane retardation (Re) at a wavelength of 550 nm of 3,000 nm or more, specifically 5,000 nm to 15,000 nm, more specifically 5,000 nm to 12,000 nm, which can improve the front brightness ratio and suppress rainbow unevenness.

[0126] In one specific example, the second protective layer has a thickness direction retardation (Rth) at a wavelength of 550 nm of 6,000 nm or more, specifically 6,000 nm to 15,000 nm, more specifically 6,000 nm to 12,000 nm, which can effectively suppress unevenness due to birefringence and improve the viewing angle characteristics of a liquid crystal display device.

[0127] In one specific example, the degree of biaxiality (NZ) of the second protective layer at a wavelength of 550 nm can be 2.5 or less, specifically 1.0 to 2.2, more specifically 1.2 to 2.0, and most specifically 1.4 to 1.8. Within this range, effects such as controlling unevenness due to birefringence and maintaining the mechanical strength of the film can be achieved.

[0128] In one embodiment, the second protective layer can be a film made of the above-mentioned material and stretched at a predetermined stretch ratio, so that the protective layer has a slow axis and a fast axis in the in-plane direction.

[0129] In one embodiment, the second protective layer may have an in-plane axis with a low refractive index in the machine direction (MD) of the second protective layer, and an in-plane axis with a high refractive index in the transverse direction (TD) of the second protective layer, in which case the second protective layer may be a TD uniaxially stretched protective film.

[0130] In another embodiment, the second protective layer may have a low refractive index axis in the cross direction (TD) of the second protective layer, and a low refractive index axis in the mechanical direction (MD) of the second protective layer, in which case the second protective layer may be an MD uniaxially stretched protective film.

[0131] In another embodiment, the second protective layer may have an in-plane axis with a low refractive index that is tilted relative to the width direction of the second protective layer, and an in-plane axis with a high refractive index that is tilted relative to the mechanical direction of the second protective layer, in which case the second protective layer may be a MD and TD biaxially stretched film or a MD and TD biaxially stretched coating layer.

[0132] In one embodiment, the second protective layer may comprise a TD uniaxially stretched protective film having the above-mentioned low refractive index axis and high refractive index axis in the in-plane direction.

[0133] In TD uniaxial stretching, the unstretched film can be produced by a stretched film manufacturing method that includes stretching the melt-extruded unstretched film resin in the TD direction alone by 100% to 200%, preferably 120% to 140%, of the TD width of the original resin. Stretching can be performed by one or more of dry stretching and wet stretching, and the stretching temperature can be (Tg-20)°C to (Tg+50)°C, based on the glass transition temperature (Tg) of the protective film resin, specifically 70°C to 250°C, more specifically 80°C to 200°C, and even more specifically 100°C to 200°C. The same stretching effect can be achieved across the board within this range.

[0134] The second protective layer may have a thickness of 100 μm or less, specifically more than 0 μm and 100 μm or less, and more specifically 10 μm to 90 μm, and can be used in polarizing plates within this range.

[0135] The second protective layer may further include a functional coating layer formed on at least one surface thereof, which may be a hard coating layer, an anti-fingerprint layer, an anti-reflection layer, a low-reflection layer, an anti-glare layer, a primer layer, or the like.

[0136] The second protective layer can be attached to the polarizer using an adhesive or pressure-sensitive adhesive layer. The adhesive or pressure-sensitive adhesive layer can be formed of a photocurable or thermosetting adhesive or pressure-sensitive adhesive. The thickness of the adhesive or pressure-sensitive adhesive layer can be 1 μm to 30 μm, for example, 2 μm to 10 μm, or 2 μm to 3 μm.

[0137] The polarizing plate may further include a third adhesive layer laminated on the lower surface of the second retardation layer or the first retardation layer.

[0138] 3rd adhesive layer The third pressure-sensitive adhesive layer can adhere the polarizing plate to the panel for optical display devices.

[0139] The third pressure-sensitive adhesive layer can be formed from a composition for the second pressure-sensitive adhesive layer containing a (meth)acrylic pressure-sensitive adhesive resin and a curing agent.

[0140] The (meth)acrylic adhesive resin may include a (meth)acrylic copolymer of a monomer mixture including a (meth)acrylic monomer having an alkyl group and a (meth)acrylic monomer having a crosslinkable functional group.

[0141] The specific types of the (meth)acrylic monomer having an alkyl group, the (meth)acrylic monomer having a crosslinkable functional group, and the curing agent are the same as those described for the first pressure-sensitive adhesive layer.

[0142] The monomer mixture can contain 60% to 99% by weight, preferably 80% to 99% by weight, of a (meth)acrylic monomer having an alkyl group, and 1% to 40% by weight, preferably 1% to 20% by weight, of a (meth)acrylic monomer having a crosslinkable functional group. Within these ranges, the adhesive strength of the third pressure-sensitive adhesive layer can be ensured.

[0143] The curing agent may be contained in an amount of 0.01 to 0.1 parts by weight, preferably 0.02 to 0.06 parts by weight, relative to 100 parts by weight of the (meth)acrylic adhesive resin. Within this range, the adhesive strength of the third adhesive layer can be easily ensured.

[0144] The composition may further include a silane coupling agent. Typical silane coupling agents known to those skilled in the art may be used, and may include, for example, one or more of acetylacetonate-based, acetoacetate-based, and epoxy-based silane coupling agents. The silane coupling agent may be included in an amount of 0.1 to 1 part by weight, specifically 0.1 to 0.5 parts by weight, per 100 parts by weight of the (meth)acrylic adhesive resin. Within this range, the adhesive strength of the third adhesive layer may be further improved.

[0145] The composition for the third pressure-sensitive adhesive layer may be solvent-free. Alternatively, the composition for the third pressure-sensitive adhesive layer may further contain a solvent. When the composition contains a solvent, the third pressure-sensitive adhesive layer can be made thin and its coatability can be improved. Conventional solvents known to those skilled in the art can be used as the solvent. For example, the solvent may include one or more of methyl ethyl ketone, ethyl acetate, and toluene.

[0146] The third pressure-sensitive adhesive layer can have a thickness of 15 μm to 35 μm, specifically 20 μm to 30 μm. With a thickness in this range, it can be used in a polarizing plate.

[0147] 1 to 3 are cross-sectional views of a polarizing plate according to one embodiment of the present invention.

[0148] Referring to FIG. 1, the polarizing plate may include a polarizer 10, a first protective layer 20, a first retardation layer 30, a first adhesive layer 40, and a second retardation layer 50 stacked in order on the lower surface of the polarizer 10, and a second protective layer 60 stacked on the upper surface of the polarizer 10.

[0149] Referring to FIG. 2, the polarizing plate may include a polarizer 10, a first protective layer 20, a second adhesive layer 70, a first retardation layer 30, a first adhesive layer 40, and a second retardation layer 50 stacked in order on the lower surface of the polarizer 10, and a second protective layer 60 stacked on the upper surface of the polarizer 10.

[0150] Referring to FIG. 3, the polarizing plate may include a polarizer 10, a first protective layer 20, a second adhesive layer 70, a first retardation layer 30, a first adhesive layer 40, a second retardation layer 50, and a third adhesive layer 80 stacked in order on the lower surface of the polarizer 10, and a second protective layer 60 stacked on the upper surface of the polarizer 10.

[0151] In one embodiment, the shrinkage force of the polarizing plate may be 3.05 N or less, and the shrinkage rate of the polarizing plate may be 0.3% or less. This range may be advantageous in providing an improvement effect against bending.

[0152] The optical display device of the present invention includes the polarizing plate of the present invention. In one embodiment, the optical display device may include a liquid crystal display device of a vertical alignment mode, for example, an IPS or FFS mode.

[0153] A liquid crystal display device includes a liquid crystal panel, a polarizing plate of the present invention laminated on the light-exiting surface of the liquid crystal panel, and a polarizing plate (light source-side polarizing plate) disposed on the light-incident surface of the liquid crystal panel. The polarizing plate disposed on the light-incident surface may include polarizing plates commonly known to those skilled in the art. The polarizing plate of the present invention can be used as a viewer-side polarizing plate. However, the present invention is not limited thereto, and the polarizing plate of the present invention can be used as a viewer-side polarizing plate or a light source-side polarizing plate.

[0154] The liquid crystal panel changes the orientation of the liquid crystal depending on whether or not a voltage is applied, and as a result, can emit light emitted from a light source.

[0155] The liquid crystal panel may include a pair of substrates and a liquid crystal layer as a display medium between the substrates. One substrate (color filter substrate) may include a color filter and a black matrix, and the other substrate (active matrix substrate) may include, but is not limited to, switching elements (e.g., TFTs) that control the electro-optical properties of the liquid crystal, as well as signal lines and pixel lines that apply gate signals to the switching elements.

[0156] In one embodiment, the liquid crystal panel can employ an IPS or FFS mode liquid crystal, which can improve the viewing angle characteristics of the liquid crystal display device.

[0157] The LCD device includes a light source on the lower surface of the light source-side polarizer. The light source may include a light source having a continuous emission spectrum. For example, the light source may be a white LED light source, a quantum dot (QD) light source, or a metal fluoride red phosphor light source, specifically KSF (K2SiF6:Mn 4+ ) phosphor or KTF (K2TiF6:Mn 4+) phosphor-containing light sources, etc. [Example]

[0158] The present invention will be described in more detail with reference to preferred examples below. However, the following examples are provided to aid in understanding the present invention and are not intended to limit the scope of the present invention.

[0159] Example 1 (1) Polarizer manufacturing A polyvinyl alcohol film (TS4500, KURARAY, thickness: 45 μm) washed with water at 25°C was swelled in a swelling bath of water at 30°C. After passing through the swelling bath, the film was treated for 65 seconds in a dyeing bath at 30°C containing an aqueous solution containing 1 mol / ml potassium iodide and 1 wt% boric acid. After passing through the dyeing bath, the film was stretched to an MD uniaxial stretching ratio of 5.7 times in a wet stretching bath containing an aqueous solution at 60°C containing 3 wt% boric acid. After passing through the wet stretching bath, the film was treated for 65 seconds in a crosslinking bath containing an aqueous solution at 25°C containing 3 wt% boric acid. After passing through the crosslinking bath, the film was treated for 10 seconds in a complementary color bath containing a complementary color solution, an aqueous solution at 30°C containing 4.5 wt% potassium iodide. After passing through the complementary color bath, the film was washed with water and dried to produce a polarizer (thickness: 18 μm).

[0160] (2) Manufacturing the first adhesive layer A composition for a first adhesive layer was prepared by blending (meth)acrylic adhesive resin CI-247 (Soken, a copolymer of a monomer mixture mainly composed of n-butyl acrylate and a hydroxyl-containing acrylic monomer) and a curing agent. The prepared composition for a first adhesive layer was applied to one side of a release film to a predetermined thickness, dried and heat-treated, and then peeled off from the release film to prepare a first adhesive layer (thickness: 15 μm).

[0161] (3) Manufacture of polarizing plates A composition containing a cellulose ester (fluorine-containing, VM500, Eastman) was applied to one side of the release film, cured, and then peeled off from the release film to produce a first retardation layer (positive C layer, Rth: -80 nm at a wavelength of 550 nm, thickness: 3.2 μm).

[0162] A cyclic olefin polymer (COP) film (ZM12, Zeon, positive A layer, Re: 120 nm at 550 nm wavelength, NZ: 1.0, thickness: 46 μm) manufactured by MD uniaxial stretching was prepared as the second retardation layer. The shrinkage force of the second retardation layer was 0.06 N and the shrinkage rate was 0.19%. The second retardation layer has a higher shrinkage force and a higher shrinkage rate than the first retardation layer.

[0163] The second and third pressure-sensitive adhesive layers were prepared by blending (meth)acrylic adhesive resin CI-247 (Soken, a copolymer of a monomer mixture containing n-butyl acrylate and a hydroxyl group-containing acrylic monomer as the main components) and a curing agent to prepare a composition, which was then applied to a release film, cured, and peeled off from the release film to prepare the second and third pressure-sensitive adhesive layers (thickness: 25 μm) and 25 μm, respectively.

[0164] A photocurable adhesive (epoxy resin adhesive) was applied to both sides of the manufactured polarizer. A polyethylene terephthalate film (thickness: 85 μm, DSG-23PET(LR), DNP) with a low-reflection layer formed on its upper surface was laminated to the upper surface of the polarizer as a second protective layer. A triacetyl cellulose film (thickness: 40 μm, KC4CT1SW, Konica) was laminated to the lower surface of the polarizer as a first protective layer. A second adhesive layer, a first retardation layer (+C), a first adhesive layer, a second retardation layer (+A), and a third adhesive layer were laminated to the lower surface of the first protective layer to manufacture a polarizing plate. The slow axis of the second retardation layer was parallel to the light absorption axis of the polarizer.

[0165] Examples 2 and 3 A polarizing plate was manufactured in the same manner as in Example 1, except that the content of the curing agent in manufacturing the first adhesive layer was changed.

[0166] Comparative Example 1 In Example 1, a polarizing plate was produced in which the second protective layer, polarizer, first protective layer, and second adhesive layer were laminated in this order, without using the first retardation layer, first adhesive layer, second retardation layer, and third adhesive layer.

[0167] Comparative Example 2 A cyclic olefin polymer (COP) film (ZM12, Zeon, positive A layer, Re: 120 nm at a wavelength of 550 nm, NZ: 1.0, thickness: 46 μm) manufactured by MD uniaxial stretching was prepared as the second retardation layer.

[0168] A composition containing a cellulose ester (fluorine-containing, VM500, Eastman) was applied to one surface of the second retardation layer and cured to produce a laminate of the first retardation layer (positive C layer, Rth: -80 nm at a wavelength of 550 nm, thickness: 3.7 μm) and the second retardation layer.

[0169] A polarizing plate was produced in the same manner as in Example 1, except that the first pressure-sensitive adhesive layer was not used, and the second protective layer, polarizer, first protective layer, second pressure-sensitive adhesive layer, first retardation layer, second retardation layer, and third pressure-sensitive adhesive layer were laminated in this order. No pressure-sensitive adhesive layer was used between the first retardation layer and the second retardation layer, and the first retardation layer was laminated directly on the second retardation layer.

[0170] Comparative Example 3 A transparent adhesive composition (OCA) containing a partial polymer formed from a monomer mixture containing 90% by weight of 2-ethylhexyl acrylate, 4% by weight of acrylamide, and 6% by weight of acrylic acid was prepared and photocured to prepare a transparent adhesive layer (thickness: 15 μm). A polarizing plate was prepared in the same manner as in Example 1, except that the transparent adhesive layer (OCA) was used instead of the first adhesive layer in Example 1.

[0171] Comparative Examples 4 to 7 In Example 1, the composition of the first adhesive layer was changed to prepare a first adhesive layer having the storage modulus, glass transition temperature, and thickness shown in Table 2. A polarizing plate was prepared in the same manner as in Example 1, except that the prepared first adhesive layer was used.

[0172] Manufacturing of light source side polarizer A polarizer was fabricated in the same manner as described above. A triacetyl cellulose (TAC) film (KC4CT1SW, Konica Minolta Opto, Inc., thickness: 40 μm) was attached to the upper surface of the fabricated polarizer, and a polyethylene terephthalate (PET) film (Toyobo Co., Ltd., thickness: 80 μm, Re: 8400 nm, Rth: 9800 nm at a wavelength of 550 nm) was attached to the lower surface of the polarizer to fabricate a light source side polarizing plate.

[0173] LCD module manufacturing The polarizers prepared in the examples and comparative examples were attached to the light-exiting surface of an IPS liquid crystal-containing liquid crystal panel using a third adhesive layer. The light-source-side polarizer prepared above was attached to the light-incident surface of an IPS liquid crystal-containing liquid crystal panel using an adhesive layer to fabricate a liquid crystal module. In this case, the TAC film of the light-source-side polarizer was adhered to the liquid crystal panel.

[0174] The polarizing plates of the examples and comparative examples were evaluated for the physical properties shown in Tables 1 and 2 below.

[0175] (1) Storage modulus of first adhesive layer or OCA (G', unit: Pa): A test piece having a thickness of 600 μm, a diameter of 8 mm, and a circular cross section is prepared by laminating multiple first adhesive layers each having a thickness of 15 μm. The storage modulus of the test piece is measured at 25°C using an ARES (Advanced Rheometry Expansion System, TA instrument) in a temperature sweep test at a frequency of 1 Hz, a strain of 5%, and a normal force of 100 N, while increasing the temperature from 0°C to 150°C at a rate of 10°C / min.

[0176] (2) Glass transition temperature (Tg, unit: °C) of the first adhesive layer: This value was measured using a DSC Discovery (TA Instruments) while heating 15 mg of the first adhesive layer to 100°C at a heating rate of 20°C / min in a nitrogen atmosphere (50 mL / min), cooling to -80°C, and then heating to 100°C at a heating rate of 10°C / min.

[0177] (3) Left-right (top, bottom) visibility: LCD modules were manufactured using the polarizers manufactured in the Example and Comparative Examples. Using EZ-Contrast XL-88 equipment, the color coordinates x and y were determined at (45°, 60°), (135°, 60°), and (315°, 60°) angles, respectively, with the black color at an azimuth angle of 60°. The distance between (45°, 60°) and (135°, 60°) or (315°, 60°) was calculated as △(x, y). A smaller △(x, y) than Comparative Example 1 was evaluated as good.

[0178] (4) Shrinkage force of polarizer (unit: N): The polarizers prepared in the examples and comparative examples were cut into rectangular specimens of MD x TD (30mm x 3mm), and both ends of the MD side of the rectangular specimens were clamped in a TMA jig, and the shrinkage force was measured at 85°C for 3 hours.

[0179] (5) Shrinkage rate of polarizing plate (unit: %): The polarizing plates manufactured in the examples and comparative examples were cut into square specimens of polarizer MD x polarizer TD (60mm x 60mm), and the specimens were subjected to a constant temperature high-temperature treatment at 60°C for 250 hours. The MD lengths of the specimens before and after the high-temperature treatment were measured using a dimension measuring instrument, and the shrinkage rate was calculated according to the above formula.

[0180] (6) Bending (unit: mm): The polarizing plates prepared in the examples and comparative examples were cut into rectangles measuring MD of the polarizer and TD of the polarizer (219.8 mm x 124.15 mm) (size for 10.1-inch replica evaluation) to prepare specimens. The specimens were placed on a flat surface with the second protective layer on top. After leaving them at 23°C for 2 hours, the maximum height from the bottom to the edge of the specimen was measured three times at each of 8 points and calculated as the average value. A bending value of less than 3 mm is considered to be effective in reducing light leakage.

[0181] [Table 1]

[0182] [Table 2]

[0183] As shown in Tables 1 and 2, the polarizing plate of the present invention provided a diagonal compensation effect on the side surfaces including the left and right sides, suppressed bending, and suppressed light leakage at the edges.

[0184] However, in all of the comparative examples provided with a first pressure-sensitive adhesive layer that did not simultaneously satisfy the storage modulus and glass transition temperature requirements of the present invention, it was not possible to obtain all of the effects of the present invention.

[0185] Simple variations or modifications of the present invention can be easily implemented by those skilled in the art, and all such variations and modifications can be considered to be included within the scope of the present invention.

Claims

1. a polarizer; and a laminate of a first retardation layer, a first pressure-sensitive adhesive layer, and a second retardation layer laminated on one surface of the polarizer; The first pressure-sensitive adhesive layer has a storage modulus of 4×10 at 25° C. ４ Pa ~ 10 x 10 ４ A polarizing plate having a glass transition temperature of -60°C to -35°C at 100 Pa.

2. The polarizing plate of claim 1 , wherein the second retardation layer has a larger shrinkage rate or shrinkage force than the first retardation layer.

3. 3. The polarizing plate of claim 2, wherein the second retardation layer has a shrinkage rate of 0.15% to 0.30% and a shrinkage force of 0.04N to 0.1N.

4. The polarizing plate according to claim 1 , wherein the second retardation layer is located farther away from the polarizer than the first retardation layer.

5. The polarizing plate according to claim 1 , wherein the second retardation layer is thicker than the first retardation layer.

6. The polarizing plate according to claim 1 , wherein the second retardation layer is a stretched film of a non-liquid crystal layer.

7. 2. The polarizing plate according to claim 1, wherein the slow axis of the second retardation layer is inclined from −5° to +5° when the light absorption axis of the polarizer is taken as 0°.

8. The polarizing plate according to claim 1 , wherein the second retardation layer contains a polymer having a positive (+) intrinsic birefringence.

9. The polarizing plate according to claim 8 , wherein the second retardation layer is a cyclic olefin polymer (COP)-based, cyclic olefin copolymer (COC)-based, or triacetyl cellulose (TAC)-based layer.

10. The polarizing plate according to claim 1 , wherein the first retardation layer is a liquid crystal layer or a non-liquid crystal layer.

11. The polarizing plate according to claim 10 , wherein the non-liquid crystal layer is a cellulose-based or polystyrene-based layer.

12. The polarizing plate of claim 1, wherein the first adhesive layer has a thickness of 5 μm to 30 μm.

13. The polarizing plate of claim 1 , wherein the first adhesive layer comprises a cured product of a composition for a first adhesive layer, the composition comprising a (meth)acrylic adhesive resin and a curing agent.

14. The (meth)acrylic adhesive resin comprises a (meth)acrylic copolymer of a monomer mixture including a (meth)acrylic monomer having an alkyl group and a (meth)acrylic monomer having a crosslinkable functional group, 14. The polarizing plate according to claim 13, wherein the curing agent is contained in an amount of 0.01 to 0.1 parts by weight with respect to 100 parts by weight of the (meth)acrylic adhesive resin.

15. 2. The polarizing plate according to claim 1, wherein the first retardation layer is a positive C layer and the second retardation layer is a positive A layer.

16. The first retardation layer has a thickness direction retardation of −110 nm to −60 nm at a wavelength of 550 nm, and the second retardation layer has an in-plane retardation of 100 nm to 150 nm at a wavelength of 550 nm, and a degree of biaxiality of 0.9 to 1.

2. The polarizing plate according to claim 15.

17. The polarizing plate according to claim 1 , comprising the first retardation layer, the first adhesive layer, and the second retardation layer stacked in this order on one surface of the polarizer.

18. The polarizing plate according to claim 17 , further comprising a first protective layer laminated between the polarizer and the first retardation layer.

19. The polarizing plate according to claim 18 , wherein the first protective layer has a lower shrinkage rate or a lower shrinkage force than the second retardation layer.

20. The polarizing plate according to claim 19 , further comprising a second protective layer laminated on another surface of the polarizer.

21. The polarizing plate of claim 17 , further comprising a second adhesive layer laminated between the first protective layer and the first retardation layer.

22. An optical display device comprising the polarizer of any one of claims 1 to 21.

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