Polarizing plate and optical display device

Abstract

Provided are a polarizing plate and an optical display device including the same, in which the polarizing plate includes a polarizer, and a laminate stacked on one surface of the polarizer and including a first phase difference layer, a first adhesive layer, and a second phase difference layer, the first adhesive layer has a modulus of 4 * 104 Pa to 10 * 104 Pa at 25 DEG C and a glass transition temperature of-60 DEG C to-35 DEG C.

Description

Technical Field

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

[0002] The liquid crystal display may include a liquid crystal layer in which liquid crystals are aligned in a horizontal direction. In this regard, there are liquid crystal displays that employ in-plane switching (IPS) or fringe field switching (FFS). In such a horizontally aligned liquid crystal display, when two electrodes are driven on one side of a substrate, the horizontally aligned liquid crystals rotate within a plane to transmit or block light, thereby improving the viewing angle.

[0003] When there is a pre-tilt in the liquid crystal orientation, the horizontally oriented liquid crystal display is likely to have anisotropy of color or visibility on the right and left sides or on the upper and lower sides. Therefore, the amount of birefringence can be different on the right and left sides or on the upper and lower sides, resulting in an imbalance in visibility (field angle) on the right and left sides or on the upper and lower sides. In order to solve this problem, a polarizing plate including a delay layer can be used between the polarizer and the panel. Typically, the polarizing plate can include two or more delay layers to solve this problem.

[0004] However, two or more retardation layers may cause a thickness imbalance between the upper and lower surfaces of the polarizing plate, and since the retardation layer is generally formed by film stretching, the polarizing plate may suffer from bending. In this article, bending refers to a slight warping of the polarizing plate at its edge, which may cause light leakage.

[0005] Background art of the present invention is disclosed in Japanese Unexamined Patent Publication No. 2006-251659 and the like. Summary of the invention

[0006] Technical issues

[0007] An aspect of the present invention is to provide a polarizing plate that provides a diagonal line compensation effect on sides including left and right sides.

[0008] Another aspect of the present invention is to provide a polarizing plate which suppresses light leakage at an edge thereof by suppressing bending.

[0009] Technical Solution

[0010] One aspect of the present invention relates to a polarizing plate.

[0011] The polarizing plate comprises: a polarizer and a laminate of a first retardation layer, a first adhesive layer (adhesive layer) and a second retardation layer stacked on one surface of the polarizer, wherein the storage modulus of the first adhesive layer at 25° C. is 4×104 Pa to 10×10 4 Pa, and the glass transition temperature is from -60°C to -35°C.

[0012] Another aspect of the present invention relates to an optical display device.

[0013] The optical display device includes a polarizing plate according to the present invention.

[0014] Advantageous Effects

[0015] The present invention provides a polarizing plate that provides a diagonal compensation effect on sides including a left side and a right side.

[0016] The present invention provides a polarizing plate that suppresses light leakage at its edges by suppressing bending. Description of the Drawings

[0017] Figure 1 is a side cross-sectional view of a polarizing plate according to an embodiment of the present invention.

[0018] Figure 2 is a side cross-sectional view of a polarizing plate according to another embodiment of the present invention.

[0019] Figure 3 is a side cross-sectional view of a polarizing plate according to other embodiments of the present invention. Detailed Description of the Embodiments

[0020] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings, so that those with ordinary knowledge in the art can easily implement the present invention. It should be understood that the present invention can be embodied in different ways and is not limited to the following embodiments.

[0021] The terms used herein are for the purpose of describing exemplary embodiments and are not intended to limit the present invention. Unless clearly indicated in the context, as used herein, the singular forms "a", "an" and "the" are also intended to include the plural forms.

[0022] In the drawings, for the clear description of the present invention, components irrelevant to the description are omitted, and throughout the specification, the same components will be denoted by the same reference numerals. Although the lengths, thicknesses or widths of multiple components may be magnified in the drawings for understanding, the present invention is not limited thereto.

[0023] In this document, spatial relative terms, such as "upper" and "lower", are defined with reference to the accompanying drawings. Therefore, it will be understood that "upper surface" and "lower surface" can be used interchangeably. Additionally, when an element is referred to as being "on" another element, it can be directly on the other element or there can be an intermediate element. On the other hand, when an element is referred to as being "directly" on or formed "on" another element, there is no intermediate element between them.

[0024] In this document, "in-plane retardation Re", "out-of-plane retardation Rth", and "biaxiality NZ" are represented by Equations A, B, and C, respectively:

[0025] [Equation A]

[0026] Re = (nx - ny) × d

[0027] [Equation B]

[0028] Rth = ((nx + ny) / 2 - nz) × d

[0029] [Equation C]

[0030] NZ = (nx - nz) / (nx - ny)

[0031] where nx, ny, and nz are the refractive indices of the optical device measured in the slow axis direction, fast axis direction, and thickness direction of the optical device at the measurement wavelength, respectively, and d is the thickness of the optical device (unit: nm).

[0032] Unless otherwise specified, the in-plane retardation, out-of-plane retardation, and biaxiality refer to the values measured by transmitting light through the optical device along the normal direction of the in-plane direction of the optical device.

[0033] As used herein to represent an angle, "+" refers to the clockwise direction relative to the reference (0°), and "-" refers to the counterclockwise direction.

[0034] In this document, the "storage modulus" of the first adhesive layer refers to the value measured on a specimen at 25°C through a temperature sweep test under the following conditions using a storage modulus measuring instrument (ARES, Advanced Rheometry Expansion System, TA Instrument Inc.): frequency: 1 Hz, strain: 5%, normal force: 100 N, while heating the specimen from 0°C to 150°C at a heating rate of 10°C / min. The specimen is prepared by stacking a plurality of first adhesive layers each with a thickness of 15 μm to form a laminate with a thickness of 600 μm, and cutting the laminate into a circle with a diameter of 8 mm.

[0035] In this document, the "glass transition temperature" of the first adhesive layer refers to the value measured by using DSC Discovery (TA Instrument Inc.) by heating a specimen prepared from 15 mg of the first adhesive layer to 100 °C at a heating rate of 20 °C / min in a nitrogen atmosphere (nitrogen gas flow rate: 50 mL / min), cooling the specimen to -80 °C, and then heating the specimen to 100 °C again at a heating rate of 10 °C / min.

[0036] In this document, the "shrinking force" of the polarizing plate can be measured using a thermomechanical analyzer (TMA) in accordance with ASTM E831 standard. Specifically, the "shrinking force" of the polarizing plate is measured as follows: a rectangular specimen with dimensions of 30 mm × 3 mm (MD (machine direction) of the polarizer) × its TD (transverse direction)) is prepared, and both ends of the specimen are clamped to two fixtures of the TMA in the MD, and then the shrinking force of the rectangular specimen is measured by shrinking at 85 °C for 3 hours.

[0037] In this document, the "shrinking rate" of the polarizing plate is measured for a square specimen (60 mm × 60 mm) (MD (machine direction) of the polarizer × its TD (transverse direction)) that has been subjected to a constant high-temperature treatment at 60 °C for 250 hours. The MD length of the specimen before the high-temperature treatment and the MD length of the specimen after the high-temperature treatment are measured using a dimensional measuring instrument, and calculated according to the following equation.

[0038] [Equation]

[0039] Shrinking rate = │S1 - S0│ / S0 × 100,

[0040] where S0 is the MD length of the specimen before the high-temperature treatment, and

[0041] S1 is the MD length of the specimen after the high-temperature treatment.

[0042] In this document, the "shrinking rate" of the retardation layer or the protective layer refers to the value measured in substantially the same manner, except that the retardation layer or the protective layer is used instead of the polarizing plate when measuring the shrinking rate of the polarizing plate.

[0043] In this document, the "shrinking force" of the retardation layer or the protective layer refers to the value measured in substantially the same manner, except that the retardation layer or the protective layer is used instead of the polarizing plate when measuring the shrinking force of the polarizing plate.

[0044] In this document, "(meth)acryloyl" means acryloyl and / or methacryloyl.

[0045] As used herein to represent a specific numerical range, "X to Y" means a value greater than or equal to X and less than or equal to Y.

[0046] When applied to an optical display panel, particularly a liquid crystal panel having horizontally aligned liquid crystals, the polarizing plate according to the present invention provides a diagonal compensation effect on side surfaces including a left side and a right side. The liquid crystal panel having horizontally aligned liquid crystals may refer to a liquid crystal panel employing in-plane switching (IPS) or fringe field switching (FFS).

[0047] The polarizing plate according to the present invention provides an effect of suppressing light leakage at the edge of the polarizing plate by suppressing bending. Herein, "bending" may refer to warping, where when the polarizing plate is placed on a flat bottom surface, the edge of the polarizing plate warps from the flat bottom surface. In one embodiment, the bending may be measured when a laminate of a first retardation layer, a first adhesive layer, and a second retardation layer of the polarizing plate is placed on a flat bottom surface, and a specific measurement method will be described below.

[0048] The polarizing plate includes: a polarizer and a laminate of a first retardation layer, a first adhesive layer, and a second retardation layer stacked on one surface of the polarizer, wherein the storage modulus of the first adhesive layer at 25 °C is 4×10 4 Pa to 10×10 4 Pa, and the glass transition temperature is -60 °C to -35 °C.

[0049] Polarizer

[0050] The polarizer includes a light absorption type polarizer that divides incident light into two perpendicular polarization components and transmits one polarization component while absorbing the other polarization component.

[0051] In one embodiment, in the in-plane direction of the polarizer, the axis having a higher refractive index of the polarizer may be the light absorption axis of the polarizer (e.g., the machine direction (MD) of the polarizer), and the axis having a lower refractive index of the polarizer may refer to the light transmission axis of the polarizer (e.g., the transverse direction (TD) of the polarizer).

[0052] The polarizer may have a degree of polarization of 95% or more, specifically 95% to 100%, more specifically 98% to 100%. Within this range, the polarizing plate can ensure an excellent diagonal compensation effect.

[0053] The polarizer may include a polarizer containing a dichroic dye and being uniaxially stretched. Specifically, the polarizer containing a dichroic dye may include a polarizer prepared by uniaxially stretching a base film for the polarizer and dyeing the base film with a dichroic dye (e.g., iodine or iodine-containing substances, including potassium iodide). The base film for the polarizer may include a polyvinyl alcohol film or their derivatives, but is not limited thereto. The polarizer can be prepared by any typical method known to those skilled in the art.

[0054] The polarizing plate may have a thickness of 1 μm to 40 μm, specifically 15 μm to 30 μm, and more specifically 16 μm to 20 μm. Within this range, the polarizing plate can be used for the polarizing panel.

[0055] First retardation layer and second retardation layer

[0056] The first retardation layer and the second retardation layer may be stacked on one surface of the polarizing plate, preferably on the light incident surface on which the internal light of the polarizing plate is incident, so as to provide a diagonal compensation effect on the side surfaces including the left or upper side and the right or lower side. Herein, "internal light" means the light emitted from the backlight unit and incident on the polarizing plate after passing through the liquid crystal panel.

[0057] In one embodiment, the first retardation layer and the second retardation layer may be stacked on the lower surface of the polarizing plate in this order. In another embodiment, the second retardation layer and the first retardation layer may be stacked on the lower surface of the polarizing plate in this order. Preferably, the first retardation layer and the second retardation layer are stacked on the lower surface of the polarizing plate in this order, thereby further suppressing bending while further improving the diagonal compensation effect.

[0058] The first retardation layer may be a positive C layer and may satisfy the following refractive index relationship: nz > nx ≒ ny. The first retardation layer may have an out-of-plane retardation of -110 nm to -50 nm (e.g., -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, for example, -90 nm to -65 nm at a wavelength of 550 nm. Within this range, the polarizing panel can easily provide a diagonal compensation effect.

[0059] The first retardation layer may have an in-plane retardation of -10 nm to 10 nm, preferably 0 nm to 5 nm at a wavelength of 550 nm. Within this range, the polarizing panel can easily provide the out-of-plane retardation described above.

[0060] The second retardation layer may be a positive A retardation layer and may satisfy the following refractive index relationship: nx > ny ≒ nz. The second retardation layer may have an in-plane retardation of 100 nm to 150 nm (e.g., 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 at a wavelength of 550 nm. Within this range, the polarizing panel can easily provide a diagonal compensation effect.

[0061] The second retardation layer may have an out-of-plane retardation of 50 nm to 80 nm (e.g., 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, the polarizing plate can easily provide a diagonal compensation effect.

[0062] The second retardation layer may have a biaxiality of 0.9 to 1.2 (e.g., 0.9, 0.95, 1.0, 1.05, 1.1, 1.15, or 1.2), preferably 0.95 to 1.1, at a wavelength of 550 nm. Within this range, the polarizing plate can easily provide a diagonal compensation effect.

[0063] The first retardation layer may be a liquid crystal layer or a non-liquid crystal layer.

[0064] When the first retardation layer is a liquid crystal layer, the first retardation layer can be formed by coating a liquid crystal layer composition onto a base film or the like, and then drying and curing it. Since the first retardation layer in the form of a liquid crystal layer is formed without performing a process such as stretching, it can easily reduce the bending of the polarizing plate. The liquid crystal layer composition can be prepared from typical compositions for liquid crystal layers known to those skilled in the art. For example, the liquid crystal layer composition may include nematic or discotic liquid crystals, etc.

[0065] When the first retardation layer is a non-liquid crystal layer, the first retardation layer can be formed by coating a non-liquid crystal layer composition onto a base film or the like, and then drying and curing it. The first retardation layer in the form of a non-liquid crystal layer is a non-stretched coating formed without stretching or the like, and can easily suppress the bending of the polarizing plate.

[0066] The composition for forming the first retardation layer as a non-stretched coating may contain the following compounds, for example, cellulose compounds such as cellulose esters, cellulose ethers, etc.; resins such as polystyrene, etc.; oligomers; or monomers.

[0067] The cellulose compound may include at least one unit in which at least some hydrogen atoms (H) of the hydroxyl group (OH) [C2 hydroxyl group, C3 hydroxyl group, or C6 hydroxyl group] of the sugar monomer constituting cellulose are substituted with an acyl group or an ether group. That is, the cellulose compound may include at least one of a cellulose ester polymer or a cellulose ether polymer.

[0068] For example, the cellulose polymer may include a cellulose ester polymer, which includes at least one unit in which at least some hydrogen atoms (H) of the hydroxyl groups (OH) [C2 hydroxyl group, C3 hydroxyl group, or C6 hydroxyl group] of the sugar monomers constituting cellulose are substituted with acyl groups, as shown in Formula 1. Herein, the acyl group may be substituted or unsubstituted.

[0069] [Formula 1]

[0070]

[0071] Wherein, n is an integer of 1 or greater.

[0072] The substituents of the cellulose ester polymer or the acyl group may include at least one selected from the following: halogen, nitro, alkyl (e.g., C1 to C 20 alkyl), alkenyl (e.g., C2 to C 20 alkenyl), cycloalkyl (e.g., C3 to C 10 cycloalkyl), aryl (e.g., C6 to C 20 aryl), heteroaryl (e.g., C3 to C 10 heteroaryl), alkoxy (e.g., C1 to C 20 alkoxy), acyl group, and halogen-containing functional group. The substituents may be the same as or different from each other.

[0073] Herein, "acyl group" may represent R-C(=O)-* (* is the connection site, and R is C1 to C 20 alkyl, C3 to C 20 cycloalkyl, C6 to C 20 aryl, or C7 to C 20 aralkyl), as is well known to those skilled in the art. The "acyl group" is coupled to the cellulose ring through an ester bond (through an oxygen atom) in the cellulose.

[0074] Herein, for convenience, "alkyl", "alkenyl", "cycloalkyl", "aryl", "heteroaryl", "alkoxy", and "acyl group" represent non-halogen compounds without halogen. The first delay layer composition may include only a cellulose ester polymer or a mixture containing a cellulose ester polymer.

[0075] Herein, "halogen" represents fluorine (F), Cl, Br, or I, preferably F.

[0076] "Halogen-containing functional group" is an organic functional group containing at least one halogen and may include aromatic, aliphatic, or alicyclic functional groups. For example, the halogen-containing functional group may represent a halogen-substituted C1 to C 20 alkyl, a halogen-substituted C2 to C 20 alkenyl, a halogen-substituted C2 to C 20Alkynyl, halogen-substituted C3 to C 10 Cycloalkyl, halogen-substituted C1 to C 20 Alkoxy, halogen-substituted acyl, halogen-substituted C6 to C 20 Aryl or halogen-substituted C7 to C 20 Aralkyl, but not limited thereto.

[0077] "Halogen-substituted acyl" can be R'-C(=O)-* (* is the attachment site, R' is halogen-substituted C1 to C 20 alkyl, halogen-substituted C3 to C 20 cycloalkyl, halogen-substituted C6 to C 20 aryl or halogen-substituted C7 to C 20 aralkyl). "Halogen-substituted acyl" can be coupled to the cellulose ring through an ester bond (through an oxygen atom) in the cellulose.

[0078] Cellulose ester polymers can be prepared by typical methods known to those skilled in the art or can be obtained from commercially available products. For example, they can be prepared by reacting trifluoroacetic acid or trifluoroacetic anhydride with the sugar monomers or polymers of sugar monomers that make up cellulose represented by Formula 1; by reacting trifluoroacetic acid or trifluoroacetic anhydride with it and then additionally reacting an acylating reagent (e.g., carboxylic anhydride or carboxylic acid) with it; or by reacting both trifluoroacetic acid or trifluoroacetic anhydride and an acylating reagent with it, thereby preparing a cellulose ester polymer having an acyl as a substituent.

[0079] The polystyrene compound can include a moiety represented by Formula 2.

[0080] [Formula 2]

[0081]

[0082] Wherein, is the attachment site of the element; R 1 , R 2 and R 3 are each independently a hydrogen atom, an alkyl group, a substituted alkyl group, or a halogen; each R is independently an alkyl group, a substituted alkyl group, a halogen, a hydroxyl group, a carboxyl group, a nitro group, an alkoxy group, an amino group, a sulfonate group, a phosphate group, an acyl group, an acyloxy group, a phenyl group, an alkoxycarbonyl group, or a cyano group; and n is an integer from 0 to 5.

[0083] The polystyrene polymer can be a halogen-containing polystyrene polymer. In Formula 2, at least one of R 1 , R 2 and R 3 can be a halogen and / or at least one R can be a halogen. In one embodiment, the halogen represents F, Cl, Br, I, preferably F.

[0084] A halogen-containing polystyrene polymer can be prepared by polymerizing a mixture including at least one of 1-(2,2-difluorovinyl)-2-fluorobenzene or 1',2',2'-trifluorostyrene. The mixture may further include styrene.

[0085] The first retardation layer may have a thickness of 1 μm to 10 μm, specifically 2 μm to 7 μm, more specifically 3 μm to 5 μm. Within this range, the first retardation layer can be used for a polarizing plate and can help improve the bending suppression effect.

[0086] The second retardation layer may have a greater thickness than the first retardation layer. The second retardation layer may have a greater shrinkage rate and / or shrinkage force than the first retardation layer. With this structure, the polarizing plate can easily improve its bending resistance.

[0087] The second retardation layer may have a thickness of 20 μm to 80 μm, specifically 30 μm to 60 μm. Within this range, the second retardation layer can be used for a polarizing plate and can help improve the bending suppression effect.

[0088] The second retardation layer may have a shrinkage force of 0.04 N to 0.1 N (e.g., 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 rate of 0.15% to 0.30%, specifically 0.18% to 0.25%. Within this range, even if shrinkage occurs due to heat, the polarizing plate can maintain a retardation value ensuring diagonal compensation.

[0089] The second retardation layer may be a stretched film of a non-liquid crystal layer. Thus, compared with the first retardation layer described above, the second retardation layer advantageously increases the in-plane retardation at a wavelength of 550 nm. In one embodiment, the second retardation layer can be formed by uniaxial stretching in the MD or TD direction, biaxial stretching in the MD and TD directions, or oblique stretching of an unstretched film for the second retardation layer. Preferably, the second retardation layer can be formed by uniaxial stretching in the MD direction of an unstretched film for the second retardation layer. For example, the second retardation layer can be formed by dry or wet stretching an unstretched film for the second retardation layer to 5 to 8 times its original length.

[0090] The second retardation layer has a slow axis and a fast axis in the in-plane direction, wherein the slow axis of the second retardation layer can be substantially parallel to the light absorption axis of the polarizer. In this context, "substantially parallel" can mean that when the light absorption axis of the polarizer is 0°, the slow axis of the second retardation layer can be inclined relative to the light absorption axis by -5° and +5°, preferably -1° and +1°, more preferably 0°. Such a structure can contribute to the diagonal compensation effect of the polarizing plate. The first adhesive layer described below can contribute to suppressing the bending of the polarizing plate having the above axial relationship.

[0091] The second retardation layer can include a polymer having positive (+) intrinsic birefringence. In this context, positive intrinsic birefringence means that the refractive index of the corresponding film increases in the stretching direction (MD). For example, the second retardation layer can comprise a norbornene polymer such as a cycloolefin polymer (COP), a cycloolefin copolymer (COC), etc.; a cellulose polymer such as triacetyl cellulose (TAC), etc.

[0092] The shrinkage force and / or shrinkage rate of the second retardation layer can be achieved by adjusting the composition of the second retardation layer when forming the second retardation layer, the elongation ratio when stretching the unstretched film for the second retardation layer, the stretching temperature, the thickness, etc., and the methods of adjusting these factors are well-known to those skilled in the art. In one embodiment, the second retardation layer can be formed by melt-extruding a second retardation layer composition to produce an unstretched film and then stretching the film; or by solution casting to prepare an unstretched film and then stretching the film.

[0093] The present invention includes two retardation layers (a first retardation layer and a second retardation layer) stacked on the lower surface of the polarizer by forming a first adhesive layer having a specific range of storage modulus and glass transition temperature between the first retardation layer and the second retardation layer, wherein the first retardation layer and the second retardation layer have different shrinkage rates and / or different shrinkage forces, thereby improving the bending suppression effect of the polarizing plate. Specifically, when the second retardation layer has a higher shrinkage rate and / or a higher shrinkage force than the first retardation layer and is placed farther from the polarizer than the first retardation layer, the first adhesive layer has an excellent effect in improving the bending suppression effect of the polarizing plate.

[0094] First adhesive layer

[0095] The first adhesive layer is directly stacked on each of the first retardation layer and the second retardation layer. As used herein, "directly stacked" means that there is no additional optical layer, additional first adhesive layer or additional adhesive layer between the first retardation layer and the first adhesive layer or between the second retardation layer and the first adhesive layer. Thus, the laminate of the first retardation layer, the first adhesive layer and the second retardation layer can be a three-layer laminate.

[0096] The first adhesive layer has a storage modulus of 4×10 4 Pa to 10×10 4 Pa at 25°C and a glass transition temperature of -60°C to -35°C. When the first adhesive layer satisfies both the storage modulus at 25°C and the glass transition temperature within these ranges, as an interlayer adhesive between the first retardation layer and the second retardation layer, the first adhesive layer can reduce shrinkage, thereby improving the bending inhibition effect of the polarizing plate in which the first retardation layer and the second retardation layer are stacked on the lower surface of the polarizer.

[0097] If the glass transition temperature of the first adhesive layer is less than -60°C, even if the first adhesive layer satisfies the modulus of the present invention, the polarizing plate may show an insignificant bending inhibition effect, or the first adhesive layer may show a deterioration in adhesive strength, making it difficult to adhesively attach the first retardation layer to the second retardation layer. If the glass transition temperature of the first adhesive layer exceeds -35°C, even if the first adhesive layer satisfies the modulus of the present invention, the polarizing plate may show an insignificant bending inhibition effect, or the first adhesive layer may show a deterioration in adhesive strength, making it difficult to adhesively attach the first retardation layer to the second retardation layer.

[0098] If the modulus of the first adhesive layer at 25°C is less than 4×10 4 Pa, even if the first adhesive layer satisfies the glass transition temperature of the present invention, the polarizing plate may show an insignificant bending inhibition effect, or the first adhesive layer may have difficulty bonding the first retardation layer to the second retardation layer. If the modulus of the first adhesive layer at 25°C exceeds 10×10 4 Pa, even if the first adhesive layer satisfies the glass transition temperature of the present invention, the polarizing plate may show an insignificant bending inhibition effect, or the first adhesive layer becomes too hard to bond the first retardation layer to the second retardation layer.

[0099] Preferably, the first adhesive layer has a modulus of 5×10 4 Pa to 9×10 4 Pa at 25°C and a glass transition temperature of -50°C to -40°C. Within this range, the polarizing plate can show an excellent bending inhibition effect, and the first adhesive layer can be easily formed.

[0100] The thickness of the first adhesive layer may be greater than the thickness of the first retardation layer and less than the thickness of the second retardation layer. For example, the first adhesive layer may have a thickness of 5 μm to 30 μm, preferably 10 μm to 20 μm. Within this range, the first adhesive layer can be used for the polarizing plate.

[0101] The first adhesive layer may have any composition as long as the first adhesive layer can achieve the modulus and glass transition temperature at 25 °C within the above range. Preferably, the first adhesive layer is formed of a thermosetting adhesive, preferably a pressure-sensitive adhesive (PSA). The pressure-sensitive adhesive can help achieve the modulus and glass transition temperature at 25 °C within the above range. Preferably, the first adhesive layer is a (meth)acrylic adhesive layer. In this case, the first adhesive layer can help achieve the modulus and glass transition temperature at 25 °C within the above range.

[0102] In one embodiment, the first adhesive layer may be formed from a first adhesive layer composition comprising a (meth)acrylic adhesive resin and a curing agent.

[0103] The (meth)acrylic adhesive resin may include a (meth)acrylic copolymer of a monomer mixture, the monomer mixture including a (meth)acrylic monomer having an alkyl group and a (meth)acrylic monomer having a crosslinkable functional group.

[0104] The (meth)acrylic monomer having an alkyl group may be a (meth)acrylate having an unsubstituted straight-chain or branched C1 to C 20 alkyl at its ester site, and may include at least one selected from the following: methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, and dodecyl (meth)acrylate.

[0105] The (meth)acrylic monomer having a crosslinkable functional group may include at least one of a hydroxyl group-containing (meth)acrylic monomer or a carboxyl group-containing (meth)acrylic monomer. Preferably, the (meth)acrylic monomer having a crosslinkable functional group includes a hydroxyl group-containing (meth)acrylic monomer to improve the adhesion of the first adhesive layer by reacting with the curing agent.

[0106] The hydroxyl group-containing (meth)acrylic monomer may have a C1 to C at its ester site 20(Meth)acrylates of an alkyl group and one or more hydroxyl groups. Specifically, the hydroxyl group-containing (meth)acrylic monomer may include at least one selected from the following: 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. These monomers can be used alone or as a mixture thereof.

[0107] The monomer mixture may include 60 wt% to 99% (e.g., 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, or 99 wt%), preferably 80 wt% to 99 wt%, of a (meth)acrylic monomer having an alkyl group, and 1 wt% to 40 wt% (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, or 40 wt%), preferably 1 wt% to 20 wt%, of a (meth)acrylic monomer having a crosslinkable functional group. Within this range, the first adhesive layer composition can easily achieve the modulus and glass transition temperature at 25 °C within the above range.

[0108] The (meth)acrylic monomer having an alkyl group and the (meth)acrylic monomer having a crosslinkable functional group may be present in the monomer mixture in a total amount of 90 wt% or more (e.g., 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, or 100 wt%), specifically 95 wt% to 100 wt%, more specifically 100 wt%. Within this range, the polarizing plate can easily achieve the effects of the present invention.

[0109] The (meth)acrylic copolymer can be prepared by a typical method known to those skilled in the art.

[0110] The curing agent may be a thermal curing agent and may include at least one selected from the following: isocyanate curing agent, epoxy curing agent, metal chelate curing agent, aziridine curing agent, and carbodiimide curing agent, preferably an isocyanate curing agent.

[0111] The isocyanate curing agent may include: toluene diisocyanate, including hexamethylene diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, etc.; xylylene diisocyanate, including 4,4'-methylenediphenyl diisocyanate, 1,3-xylylene diisocyanate, 1,4-xylylene diisocyanate, etc.; hydrogenated toluene diisocyanate; isophorone diisocyanate; 1,3-bis(isocyanatomethyl)cyclohexane; tetramethylxylylene diisocyanate; 1,5-naphthalene diisocyanate; 2,2,4-trimethylhexamethylene diisocyanate; 2,4,4-trimethylhexamethylene diisocyanate; adducts of any of these isocyanate curing agents, such as toluene diisocyanate adduct of trimethylolpropane, trimer adducts including trimethylolpropane / toluene diisocyanate, etc., xylylene diisocyanate adducts of trimethylolpropane, triphenylmethane triisocyanate or methylene bis(triisocyanate), etc.

[0112] Relative to 100 parts by weight of the (meth)acrylic adhesive resin, the curing agent may be present in an amount of 0.01 to 0.1 part by weight (e.g., 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09 or 0.1 part by weight), preferably 0.02 to 0.06 part by weight. Within this range, the curing agent can facilitate achieving the modulus and glass transition temperature of the first adhesive layer within the above range at 25°C.

[0113] The composition may further contain a silane coupling agent. The silane coupling agent may be selected from any type of silane coupling agent known to those skilled in the art and may include, for example, at least one selected from the following: acetylacetone silane coupling agent, acetoacetic acid silane coupling agent, and epoxy silane coupling agent. Relative to 100 parts by weight of the (meth)acrylic adhesive resin, the silane coupling agent may be present in an amount of 0.1 to 1 part by weight, specifically 0.1 to 0.5 part by weight. Within this range, the composition can further improve the adhesion of the first adhesive layer.

[0114] The first adhesive layer composition may be a solvent-free composition. Alternatively, the first adhesive layer composition may further contain a solvent. When the composition contains a solvent, the first adhesive layer can be formed to have a thin thickness, and the composition can have improved coatability. The solvent may be selected from any typical solvent known to those skilled in the art. For example, the solvent may include at least one selected from the following: methyl ethyl ketone, ethyl acetate, and toluene.

[0115] The first adhesive layer can be formed by any typical method known to those skilled in the art. For example, the first adhesive layer can be formed by depositing the first adhesive layer composition on one surface of the base film to a predetermined thickness and then drying and curing it.

[0116] 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 be present alone or in plural in the polarizing plate.

[0117] First protective layer

[0118] The first protective layer may be stacked on the lower surface of the polarizer to improve the mechanical strength of the polarizing plate. Alternatively, the first protective layer may include a base film for forming the first retardation layer.

[0119] The first protective layer may have an in-plane retardation of 10 nm or less, for example, 0 nm to 10 nm or 0 nm to 5 nm, at a wavelength of 550 nm. Within this range, the first protective layer does not affect the diagonal compensation effect brought by the first retardation layer and the second retardation layer.

[0120] The first protective layer may have a shrinkage rate and / or shrinkage force lower than that of the second retardation layer. The first protective layer may be arranged closer to the polarizer than the first retardation layer and the second retardation layer. With this structure, the polarizing plate can achieve a further improvement in the bending suppression effect.

[0121] In one embodiment, the first protective layer may have a shrinkage 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, the polarizing plate can easily ensure the bending suppression effect. The first protective layer may have a shrinkage 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, the polarizing plate can easily ensure the bending suppression effect.

[0122] The first protective layer may have a thickness of 25 μm to 80 μm, preferably 30 μm to 60 μm. Within this range, the first protective layer can be used for the polarizing plate.

[0123] The first protective layer may be a coating 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 include a film formed of at least one selected from the following: cellulose ester resins, including triacetyl cellulose (TAC), etc.; polyester resins, including polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, etc.; cyclic olefin resins; polycarbonate resins; polyethersulfone resins; polysulfone resins; polyamide resins; polyimide resins; polyolefin resins; polyarylate resins; polyvinyl alcohol resins; polyvinyl chloride resins; and polyvinylidene chloride resins.

[0124] The first protective layer may be bonded to the polarizer through an adhesive layer or a bonding layer. The adhesive layer or the bonding layer may be formed of a thermosetting or photocurable adhesive composition. The adhesive layer or the bonding layer may have a thickness of 1 μm to 30 μm, for example, 2 μm to 10 μm, for example, 2 μm to 3 μm.

[0125] A second bonding layer may be further stacked between the first protective layer and the first retardation layer.

[0126] Second adhesive layer

[0127] The second bonding layer is used to improve the strength of the polarizing plate by adhesively attaching the first protective layer and the first retardation layer to each other or by adhesively attaching the first protective layer and the second retardation layer to each other.

[0128] The second bonding layer may be formed of a second bonding layer composition containing a (meth)acrylic adhesive resin and a curing agent.

[0129] The (meth)acrylic adhesive resin may include a (meth)acrylic copolymer of a monomer mixture, the monomer mixture including a (meth)acrylic monomer having an alkyl group and a (meth)acrylic monomer having a crosslinkable functional group.

[0130] Details 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 bonding layer.

[0131] The monomer mixture may contain 60 wt% to 99 wt%, preferably 80 wt% to 99 wt% of the (meth)acrylic monomer having an alkyl group, and 1 wt% to 40 wt%, preferably 1 wt% to 20 wt% of the (meth)acrylic monomer having a crosslinkable functional group. Within this range, the composition can ensure the adhesion of the second bonding layer.

[0132] Relative to 100 parts by weight of the (meth)acrylic adhesive resin, the curing agent may be present in an amount of 0.01 to 0.1 part by weight, preferably 0.02 to 0.06 part by weight. Within this range, it is easy to ensure the adhesion of the second adhesive layer.

[0133] The composition may further comprise a silane coupling agent. The silane coupling agent may be selected from any type of silane coupling agent known to those skilled in the art and may include, for example, at least one selected from the following: acetylacetone silane coupling agent, acetoacetic acid silane coupling agent, and epoxy silane coupling agent. Relative to 100 parts by weight of the (meth)acrylic adhesive resin, the silane coupling agent may be present in an amount of 0.1 to 1 part by weight, specifically 0.1 to 0.5 part by weight. Within this range, the composition may further improve the adhesion of the second adhesive layer.

[0134] The second adhesive layer composition may be a solvent-free composition. Alternatively, the second adhesive layer composition may further comprise a solvent. When the composition comprises a solvent, the second adhesive layer may be formed to have a thin thickness and the composition may have improved coatability. The solvent may be selected from any typical solvent known to those skilled in the art. For example, the solvent may include at least one selected from the following: methyl ethyl ketone, ethyl acetate, and toluene.

[0135] The second adhesive layer may have a thickness of 15 μm to 35 μm, specifically 20 μm to 30 μm. Within this range, the second adhesive layer can be used for the polarizing plate.

[0136] The polarizing plate may further comprise a second protective layer stacked on the other surface of the polarizing film. The second protective layer may be present alone or in plurality in the polarizing plate.

[0137] Second protective layer

[0138] The second protective layer is disposed on the light-emitting surface of the polarizing film and can improve the image quality or protect the polarizing film by acting on the light emitted from the polarizing film.

[0139] The second protective layer may comprise a protective film or a protective coating.

[0140] The protective film may be an optically transparent film and may include a film formed of at least one selected from the following: cellulose ester resins, including triacetyl cellulose (TAC), etc.; polyester resins, including polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, etc.; cyclic polyolefin resins; polycarbonate resins; polyethersulfone resins; polysulfone resins; polyamide resins; polyimide resins; polyolefin resins; polyarylate resins; polyvinyl alcohol resins; polyvinyl chloride resins; and polyvinylidene chloride resins. Specifically, the protective film may be a TAC film or a PET film. The protective coating may be formed of at least one of a thermosetting composition for coating or a photocurable composition for coating.

[0141] In one embodiment, the second protective layer may be a retardation film.

[0142] In one embodiment, the second protective layer may have an in-plane retardation (Re) of 3,000 nm or greater, specifically 5,000 nm to 15,000 nm, more specifically 5,000 nm to 12,000 nm, at a wavelength of 550 nm. Within this range, the polarizing plate can ensure effects such as improvement of front contrast and suppression of rainbow mura.

[0143] In one embodiment, the second protective layer may have an out-of-plane retardation (Rth) of 6,000 nm or greater, specifically 6,000 nm to 15,000 nm, more specifically 6,000 nm to 12,000 nm, at a wavelength of 550 nm. Within this range, the polarizing plate can ensure effects such as control of spots through birefringence and improvement of the viewing angle characteristics in a liquid crystal display.

[0144] In one embodiment, the second protective layer may have a biaxiality (NZ) of 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, at a wavelength of 550 nm. Within this range, the polarizing plate can ensure effects such as control of spots through birefringence and maintenance of the mechanical strength of the film.

[0145] In one embodiment, the second protective layer may be a film formed of the materials described above and stretched at a predetermined draw ratio. The protective layer may have a slow axis and a fast axis in its in-plane direction.

[0146] In one embodiment, the axis with a lower refractive index in the in-plane direction of the second protective layer may correspond to the machine direction (MD) of the second protective layer, and the axis with a higher refractive index in the in-plane direction of the second protective layer may correspond to the transverse direction (TD) of the second protective layer. In this case, the second protective layer may be a TD uniaxially stretched protective film.

[0147] In another embodiment, the axis with a lower refractive index in the in-plane direction of the second protective layer may correspond to the transverse direction (TD) of the second protective layer, and the axis with a higher refractive index in the in-plane direction of the second protective layer may correspond to the machine direction (MD) of the second protective layer. In this case, the second protective layer may be an MD uniaxially stretched protective film.

[0148] In another embodiment, the axis with a lower refractive index in the in-plane direction of the second protective layer may correspond to a direction inclined with respect to the transverse direction of the second protective layer, and the axis with a higher refractive index in the in-plane direction of the second protective layer may correspond to a direction inclined with respect to the machine direction (MD) of the second protective layer. In this case, the second protective layer may be an MD / TD biaxially stretched film or an MD / TD biaxially stretched coating.

[0149] In one embodiment, the second protective layer may include a TD uniaxially stretched protective film, so as to have an axis with a lower refractive index and an axis with a higher refractive index in the in-plane direction.

[0150] In TD uniaxial stretching, a stretched film can be prepared by a method including a step of stretching the molten extruded resin of the unstretched film only in the TD direction to 100% to 200%, preferably 120% to 140% of its initial length. The stretching can be carried out by dry stretching and / or wet stretching, and can be carried out at a temperature of (Tg - 20)°C to (Tg + 50)°C with respect to the glass transition temperature Tg of the protective film resin, specifically at a temperature of 70°C to 250°C, more specifically 80°C to 200°C, and more specifically 100°C to 200°C. Within this range, the stretching can uniformly achieve the same stretching effect.

[0151] The second protective layer may have a thickness of 100 μm or less, specifically greater than 0 μm and less than or equal to 100 μm, and more specifically 10 μm to 90 μm. Within this range, the second protective layer can be used for the polarizing plate.

[0152] The second protective layer may further include a functional coating formed on at least one of its surfaces. The functional coating may include a hard coating, an anti-fingerprint layer, an anti-reflection layer, a low reflectivity layer, an anti-glare layer, a primer layer, etc.

[0153] The second protective layer can be bonded to the polarizer through an adhesive layer or a bonding layer. The adhesive layer or the bonding layer can be formed of a photocurable or thermosetting adhesive or a photocurable or thermosetting binder. The adhesive layer or the bonding layer can have a thickness of 1 μm to 30 μm, such as 2 μm to 10 μm or 2 μm to 3 μm.

[0154] The polarizing plate may further include a second retardation layer or a third bonding layer stacked on the lower surface of the first retardation layer.

[0155] Third adhesive layer

[0156] The third bonding layer is used to adhesively attach the polarizing plate to the optical display panel.

[0157] The third bonding layer can be formed of a third bonding layer composition containing a (meth)acrylic adhesive resin and a curing agent.

[0158] The (meth)acrylic adhesive resin may include a (meth)acrylic copolymer of a monomer mixture, the monomer mixture including a (meth)acrylic monomer having an alkyl group and a (meth)acrylic monomer having a crosslinkable functional group.

[0159] Details 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 in the first bonding layer.

[0160] The monomer mixture may contain 60 wt% to 99 wt%, preferably 80 wt% to 99 wt% of the (meth)acrylic monomer having an alkyl group, and 1 wt% to 40 wt%, preferably 1 wt% to 20 wt% of the (meth)acrylic monomer having a crosslinkable functional group. Within this range, the composition can ensure the adhesion of the third bonding layer.

[0161] Relative to 100 parts by weight of the (meth)acrylic adhesive resin, the curing agent may be present in an amount of 0.01 part by weight to 0.1 part by weight, preferably 0.02 part by weight to 0.06 part by weight. Within this range, it is easy to ensure the adhesion of the third bonding layer.

[0162] The composition may further comprise a silane coupling agent. The silane coupling agent may be selected from any type of silane coupling agent known to those skilled in the art, and may include, for example, at least one selected from the following: acetylacetone silane coupling agent, acetoacetic acid silane coupling agent, and epoxy silane coupling agent. Relative to 100 parts by weight of the (meth)acrylic adhesive resin, the silane coupling agent may be present in an amount of 0.1 to 1 part by weight, specifically 0.1 to 0.5 part by weight. Within this range, the composition can further improve the adhesion of the third adhesive layer.

[0163] The third adhesive layer composition may be a solvent-free composition. Alternatively, the third adhesive layer composition may further comprise a solvent. When the composition comprises a solvent, the third adhesive layer can be formed to have a thin thickness, and the composition can exhibit improved coatability. The solvent may be selected from any typical solvent known to those skilled in the art. For example, the solvent may include at least one selected from the following: methyl ethyl ketone, ethyl acetate, and toluene.

[0164] The third adhesive layer may have a thickness of 15 μm to 35 μm, specifically 20 μm to 30 μm. Within this range, the third adhesive layer can be used for the polarizing plate.

[0165] Figures 1 to 3 is a cross-sectional view of a polarizing plate according to an embodiment of the present invention.

[0166] Reference Figure 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 sequence on the lower surface of the polarizer 10; and a second protective layer 60 stacked on the upper surface of the polarizer 10.

[0167] Reference Figure 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 sequence on the lower surface of the polarizer 10; and a second protective layer 60 stacked on the upper surface of the polarizer 10.

[0168] Reference Figure 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 sequence on the lower surface of the polarizer 10; and a second protective layer 60 stacked on the upper surface of the polarizer 10.

[0169] In one embodiment, the polarizing plate may have a shrinkage force of 3.05 N or less and a shrinkage rate of 0.3% or less. Within this range, the polarizing plate can advantageously provide a bending suppression effect.

[0170] The optical display device according to the present invention includes a polarizing plate according to the present invention. In one embodiment, the optical display device may include a vertically aligned liquid crystal display, for example, an IPS or FFS liquid crystal display.

[0171] The liquid crystal display includes a liquid crystal panel, a polarizing plate according to the present invention stacked on the light-emitting 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 a polarizing plate generally known to those skilled in the art. The polarizing plate according to the present invention can be used as a viewer-side polarizing plate. However, it should be understood that the present invention is not limited thereto and the polarizing plate according to the present invention can be used as a viewer-side polarizing plate or a light source-side polarizing plate.

[0172] In the liquid crystal panel, the orientation of the liquid crystal is changed according to whether a voltage is applied or not, thereby allowing light emitted from a light source to pass therethrough.

[0173] The liquid crystal panel may include a pair of substrates and a liquid crystal layer as a display medium interposed between the substrates. The substrate on one side (color filter substrate) may be provided with a color filter and a black matrix, and the substrate on the other side (active matrix substrate) may be provided with switching elements (e.g., TFTs) configured to control the electrical and optical characteristics of the liquid crystal, and pixel lines and signal lines for supplying gate signals to the switching elements, but is not limited thereto.

[0174] In one embodiment, the liquid crystal panel may employ IPS or FFS. With this structure, the liquid crystal display can achieve an improvement in the viewing angle.

[0175] The liquid crystal display includes a light source on the lower surface of the light source-side polarizing plate. The light source may include a light source having a continuous emission spectrum. For example, the light source may include a white LED light source, a quantum dot (QD) light source, a metal fluoride red phosphor light source, specifically containing a phosphor such as KSF (K2SiF6:Mn 4+ ) phosphor, a KTF (K2TiF6:Mn 4+ ) phosphor, etc.

[0176] Mode of the Invention

[0177] Next, the present invention will be described in more detail with reference to some embodiments. However, it should be noted that these embodiments are provided for illustrative purposes only and are not to be construed as limiting the present invention in any way.

[0178] Example 1

[0179] (1) Preparation of Polarizer

[0180] A polyvinyl alcohol film (TS4500, thickness: 45 μm, Kuraray) washed with water at 25°C was swollen in a swelling bath at 30°C. After passing through the swelling bath, the film was dyed in a dyeing bath containing an aqueous solution of 1 mol / ml potassium iodide and 1 wt% boric acid at 30°C for 65 seconds. After passing through the dyeing bath, the film was stretched to an MD uniaxial draw ratio of 5.7 times its initial length in a wet stretching bath containing an aqueous solution of 3 wt% boric acid at 60°C. After passing through the wet stretching bath, the film was held in a crosslinking bath containing an aqueous solution of 3 wt% boric acid at 25°C for 65 seconds. After passing through the crosslinking bath, the film was held in a color correction bath containing an aqueous solution of 4.5 wt% potassium iodide (color correction liquid) at 30°C for 10 seconds. The film passing through the color correction bath was washed with water and dried to prepare a polarizer (thickness: 18 μm).

[0181] (2) Preparation of First Adhesive Layer

[0182] A first adhesive layer composition was prepared by mixing a (meth)acrylic adhesive resin (CI-247, a copolymer of a monomer mixture containing n-butyl acrylate and a hydroxyl group-containing acrylic monomer as the main component, Soken Co., Ltd.) and a curing agent. The composition was deposited on one surface of a release film to a predetermined thickness, dried and heat-treated, and the release film was removed to prepare a first adhesive layer (thickness: 15 μm).

[0183] (3) Preparation of Polarizing Plate

[0184] A first retardation layer (positive C layer, Rth: -80 nm at a wavelength of 550 nm, thickness: 3.2 μm) was prepared by depositing a composition containing a cellulose ester (fluorine-containing, VM500, Eastman Co., Ltd.) on one surface of a release film, curing the composition and removing the release film.

[0185] A cycloolefin polymer (COP) film (ZM12, positive A layer, Re: 120 nm at a wavelength of 550 nm, NZ: 1.0, thickness: 46 μm, Zeon Co., Ltd.) prepared by MD uniaxial stretching was used as the second retardation layer. The second retardation layer had a shrinkage force of 0.06 N and a shrinkage rate of 0.19%. The second retardation layer had a higher shrinkage force and a higher shrinkage rate than the first retardation layer.

[0186] Each of the second adhesive layer (thickness: 25 μm) and the third adhesive layer (thickness: 25 μm) is formed as follows: A composition is prepared using a (meth)acrylic adhesive resin (CI-247, a copolymer of a monomer mixture containing n-butyl acrylate and a hydroxyl group-containing acrylic monomer as a main component, Soken Co., Ltd.) and a curing agent. The composition is deposited onto a release film and cured, and then the release film is removed.

[0187] A photocurable binder (epoxy resin binder) is deposited on both surfaces of the prepared polarizing plate. A polyethylene terephthalate film (thickness: 85 μm, DSG-23PET(LR), DNP) having a low-reflection layer formed on its upper surface is stacked on the upper surface of the polarizing plate as a second protective layer. A triacetyl cellulose film (thickness: 40 μm, KC4CT1SW, Konica Co., Ltd.) is stacked on the lower surface of the polarizing plate as a first protective layer. A polarizing plate is prepared by stacking the second adhesive layer, the first retardation layer (+C), the first adhesive layer, the second retardation layer (+A), and the third adhesive layer on the lower surface of the first protective layer. The slow axis of the second retardation layer is parallel to the light absorption axis of the polarizing plate.

[0188] Examples 2 and 3

[0189] A polarizing plate is prepared in the same manner as in Example 1, except that the content of the curing agent in the preparation of the first adhesive layer is changed.

[0190] Comparative Example 1

[0191] A polarizing plate is prepared in the same manner as in Example 1, except that the second protective layer, the polarizing plate, the first protective layer, and the second adhesive layer are stacked in sequence without the first retardation layer, the first adhesive layer, the second retardation layer, and the third adhesive layer.

[0192] Comparative Example 2

[0193] A cycloolefin polymer (COP) film (ZM12, positive A layer, Re: 120 nm at a wavelength of 550 nm, NZ: 1.0, thickness: 46 μm, Zeon Co., Ltd.) prepared by MD uniaxial stretching is used as the second retardation layer.

[0194] A composition containing a cellulose ester (fluorine-containing, VM500, Eastman Co., Ltd.) is deposited on one surface of the second retardation layer and cured to prepare 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.

[0195] A polarizing plate was prepared in the same manner as in Example 1, except that the second protective layer, the polarizer, the first protective layer, the second adhesive layer, the first retardation layer, the second retardation layer, and the third adhesive layer were sequentially stacked without the first adhesive layer. The first retardation layer was directly stacked on the second retardation layer, and there was no adhesive layer between the first retardation layer and the second retardation layer.

[0196] Comparative Example 3

[0197] A transparent adhesive composition (OCA) including a partial polymer formed from a monomer mixture containing 90 wt% of 2-ethylhexyl acrylate, 4 wt% of acrylamide, and 6 wt% of acrylic acid was prepared, and it was photocured to prepare a transparent adhesive layer (thickness: 15 μm). In Example 1, 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.

[0198] Comparative Examples 4 to 7

[0199] By changing the composition of the first adhesive layer in Example 1, a first adhesive layer having a storage modulus, a glass transition temperature, and a thickness listed in Table 2 was prepared. A polarizing plate was prepared in the same manner as in Example 1, except that the first adhesive layer prepared above was used.

[0200] Preparation of the light source side polarizing plate

[0201] A polarizer was prepared by the same method as above. A triacetyl cellulose (TAC) film (KC4CT1SW, thickness: 40 μm, Konica Minolta Opto Inc.) was bonded to the upper surface of the polarizer, and a polyethylene terephthalate (PET) film (thickness: 80 μm, Re: 8400 nm, Rth: 9800 nm at a wavelength of 550 nm, Toyobo Co., Ltd.) was bonded to the lower surface of the polarizer to prepare a light source side polarizing plate.

[0202] Preparation of the liquid crystal module

[0203] Each polarizing plate prepared in the examples and comparative examples was adhesively attached to the light-emitting surface of an IPS liquid crystal-containing liquid crystal panel via a third adhesive layer. A liquid crystal module was manufactured by adhesively attaching the prepared light source side polarizing plate to the light-incident surface of an IPS liquid crystal-containing liquid crystal panel via an adhesive layer. Here, the TAC film of the light source side polarizing plate was bonded to the liquid crystal panel.

[0204] The characteristics listed in Tables 1 and 2 below of the polarizing plates in the examples and comparative examples were evaluated.

[0205] (1) Storage modulus (G', unit: Pa) of the first adhesive layer or OCA: A specimen with a circular cross-section, a thickness of 600 μm, and a diameter of 8 mm was prepared by stacking multiple first adhesive layers with a thickness of 15 μm. Using a storage modulus measuring instrument (ARES, Advanced Rheometry Expansion System, TA Instrument Inc.), the storage modulus of the specimen was measured at 25 °C through a temperature scan test under the following conditions: frequency: 1 Hz, strain: 5%, normal force: 100 N, while heating the specimen from 0 °C to 150 °C at a heating rate of 10 °C / min.

[0206] (2) Glass transition temperature (Tg, unit: °C) of the first adhesive layer: Using DSC Discovery (TA Instrument Inc.), the glass transition temperature of the first adhesive layer was measured by heating a specimen prepared from 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 the specimen to -80 °C, and then heating the specimen to 100 °C again at a heating rate of 10 °C / min.

[0207] (3) Visibility on the left and right (upper and lower sides): A liquid crystal module was prepared from the polarizing plates prepared in the examples and comparative examples by the method described above. Using EZ-Contrast XL-88, the color coordinates (x, y) at each of (45°, 60°), (135°, 60°), and (315°, 60°) were obtained by specifying the left corner (or upper corner) (45°) / right corner (or lower corner) (315°) at a black azimuth (polarization angle, azimuth) of 60°. The distance from (45°, 60°) to (135°, 60°) or (315°, 60°) was calculated as Δ(x, y). A lower Δ(x, y) value than that of Comparative Example 1 indicates good visibility.

[0208] (4) Shrinkage force of the polarizing plate (unit: N): Rectangular specimens with a size of 30 mm × 3 mm (MD × TD of the polarizer) were prepared from each of the polarizing plates manufactured in the examples and comparative examples, and both ends of the specimens were clamped to two fixtures of the TMA in the MD direction, and then the shrinkage force of the rectangular specimens was measured by shrinking at 85 °C for 3 hours.

[0209] (5)Shrinkage rate of polarizing plate (unit: %): Prepare square specimens (60 mm × 60 mm) (MD × TD of polarizer) using each polarizing plate manufactured in the examples and comparative examples, and subject them to constant high-temperature treatment at 60 °C for 250 hours. Measure the MD length of the specimen before the high-temperature treatment and the MD length of the specimen after the high-temperature treatment using a dimensional measuring instrument, and calculate according to the above equation.

[0210] (6)Bending (unit: mm): Cut each polarizing plate manufactured in the examples and comparative examples into rectangular specimens with dimensions of 219.8 mm × 124.15 mm (10.1-inch analog size) (MD × TD of polarizer), and then place them on a flat bottom surface so that the second protective layer becomes the top layer. Then, after holding the specimen at 23 °C for 2 hours, measure the maximum height from the bottom surface to the edge of the specimen three times at 8 points on the specimen, and take the average value. A bending value less than 3 mm indicates an improvement in light leakage suppression.

[0211] [Table 1]

[0212]

[0213] [Table 2]

[0214]

[0215] As shown in Table 1 and Table 2, the polarizing plate according to the present invention provides a diagonal compensation effect on the sides including the left and right sides, and suppresses light leakage at its edges by suppressing bending.

[0216] However, all the polarizing plates of the comparative examples each including a first adhesive layer that does not simultaneously satisfy the storage modulus and glass transition temperature of the present invention cannot achieve the effects of the present invention.

[0217] It should be understood that those skilled in the art can make various modifications, changes, variations, and equivalent embodiments without departing from the spirit and scope of the present invention.

Claims

1. A polarizing plate, comprising: Polarizer; and a laminate of a first retardation layer, a first adhesive layer, and a second retardation layer stacked on one surface of the polarizer, Among them, the first adhesive layer has a storage modulus of 4×10 4 Pa to 10×10 4 Pa at 25°C; and a glass transition temperature of -60°C to -35°C.

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

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

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

5. The polarizing plate according to claim 1, wherein, The second retardation layer has a greater thickness than the first retardation layer.

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

7. The polarizing plate according to claim 1, wherein, When the optical absorption axis of the polarizer is 0°, the slow axis of the second retardation layer is inclined at an angle of -5° to +5° with respect to the optical absorption axis of the polarizer.

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 contains a cycloolefin polymer (COP), a cycloolefin copolymer (COC), or a triacetyl cellulose (TAC) resin.

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

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

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

13. The polarizing plate according to claim 1, wherein, The first adhesive layer contains a cured product of a first adhesive layer composition containing a (meth)acrylic adhesive resin and a curing agent.

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

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

16. The polarizing plate according to claim 15, wherein, The first retardation layer has an out-of-plane 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 and a biaxiality of 0.9 to 1.2 at a wavelength of 550 nm.

17. The polarizing plate according to claim 1, wherein, The first retardation layer, the first adhesive layer, and the second retardation layer are sequentially stacked on one surface of the polarizer.

18. The polarizing plate according to claim 17, further comprising: a first protective layer stacked 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 stacked on the other surface of the polarizer.

21. The polarizing plate according to claim 17, further comprising: a second adhesive layer stacked between the first protective layer and the first retardation layer.

22. An optical display device, comprising the polarizing plate according to any one of claims 1 to 21.

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