Polarizing plate and optical display device including the same

Abstract

Disclosed are a polarizing plate and an optical display device including the same. The polarizing plate includes a polarizer; and a laminate of a first delay layer and a second delay layer, stacked on the lower surface of the polarizer. The first delay layer satisfies equation 1, and the second delay layer satisfies equation 2. The sum of the in-plane delay values ​​of the first delay layer and the second delay layer at a wavelength of 550 nanometers is in the range of 100 nanometers to 110 nanometers, the sum of the out-of-plane delay values ​​of the first delay layer and the second delay layer at a wavelength of 550 nanometers is in the range of ‑30 nanometers to +10 nanometers, and the second delay layer includes a fluorene-based delay layer. The definitions of equations 1 and 2 are the same as those in the specification. The present invention provides a polarizing plate having a good effect on thickness reduction.

Description

Technical Field

[0001] The present invention relates to a polarizing plate and an optical display device including the same. More specifically, the present invention relates to a polarizing plate including a retardation layer that does not suffer from breakage when manufacturing the polarizing plate to provide good processability and having good diagonal compensation and thermal stability, and an optical display device including the same. Background Art

[0002] The liquid crystal display includes a liquid crystal panel, an observer-side polarizing plate mounted on one surface of the liquid crystal panel, and a light source-side polarizing plate mounted on the other surface thereof. The liquid crystal panel includes a liquid crystal layer. Although the front visibility is good, the liquid crystal panel including an in-plane switching (IPS) liquid crystal layer or a fringe field switching (FFS) liquid crystal layer has poor screen visibility at the diagonal. To solve this problem, the observer-side polarizing plate or the light source-side polarizing plate requires a retardation layer.

[0003] In recent years, with the trend of reducing the thickness of the polarizing plate, attempts have been made to provide a liquid crystal layer to the delay layer. However, the liquid crystal layer has a fragile nature, which leads to deterioration in the durability of the polarizing plate. As a delay layer, especially as a positive B (B+) plate, an acrylic film is generally used in this technology. The acrylic film has the advantage of allowing the refractive indices nx, ny and nz of the positive B plate to be easily achieved. However, adding additives to prevent the acrylic film from breaking will bring many problems, such as increased price and reduced compatibility. However, as the use environment of the polarizing plate becomes stricter, the polarizing plate requires thermal stability.

[0004] The background art of the present invention is disclosed in Korean Patent Registration No. 10-1937447. Summary of the invention

[0005] Technical Challenges

[0006] An object of the present invention is to provide a polarizing plate including a retardation layer which does not suffer from breakage when it is manufactured.

[0007] Another object of the present invention is to provide a polarizing plate having good diagonal compensation and thermal stability when applied to a liquid crystal display.

[0008] A further object of the present invention is to provide a polarizing plate having a good effect in thickness reduction.

[0009] Means of solving the problem

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

[0011] The polarizing plate includes a polarizer; and a laminate of a first retardation layer and a second retardation layer stacked on a lower surface of the polarizer,

[0012] Wherein the first delay layer satisfies equation 1, and the second delay layer satisfies equation 2:

[0013] [Equation 1]

[0014] NX>NY>NZ,

[0015] Wherein in equation 1, nx, ny and nz are the refractive indices of the first retardation layer in its slow axis direction, fast axis direction and thickness direction at a wavelength of 550 nanometers, respectively,

[0016] [Equation 2]

[0017] nz>nx>ny,

[0018] Wherein in equation 2, nx, ny and nz are the refractive indices of the second retardation layer in its slow axis direction, fast axis direction and thickness direction at a wavelength of 550 nanometers, respectively,

[0019] The sum of the in-plane retardation values ​​of the first retardation layer and the second retardation layer at a wavelength of 550 nanometers is in the range of 100 nanometers to 110 nanometers,

[0020] The sum of the out-of-plane retardation values ​​of the first retardation layer and the second retardation layer at a wavelength of 550 nanometers is in the range of -30 nanometers to +10 nanometers, and

[0021] The second retardation layer includes a fluorene-based retardation layer.

[0022] The second retardation layer may be formed directly on the first retardation layer.

[0023] Assuming that the first retardation layer has a slow axis disposed at an angle of 0°, the second retardation layer may have a slow axis tilted at an angle of -5° to +5°.

[0024] The second retardation layer may have an in-plane retardation value of 50 nm to 60 nm and an out-of-plane retardation value of -150 nm to -120 nm at a wavelength of 550 nm.

[0025] The second retardation layer may have a biaxiality of -3 to 0 at a wavelength of 550 nanometers.

[0026] The second retardation layer may satisfy 1.0≤Re(450) / Re(550)≤1.2 and 0.85≤Re(650) / Re(550)≤1.0, wherein Re(450), Re(550) and Re(650) represent the in-plane retardation values ​​at wavelengths of 450 nm, 550 nm and 650 nm, respectively.

[0027] In Equation 2, the second retardation layer may have an nx value of 1.59 to 1.61, a ny value of 1.59 to 1.61, and a nz value of 1.61 to 1.63.

[0028] The second retardation layer may include a fluorene-based ring-containing resin and an aromatic thermoplastic resin.

[0029] Assuming that the polarizer has an absorption axis disposed at an angle of 0°, the second retardation layer may have a slow axis tilted at an angle of 87° to 93°.

[0030] The first retardation layer may have an in-plane retardation value of 50 nm to 60 nm and an out-of-plane retardation value of 120 nm to 150 nm at a wavelength of 550 nm.

[0031] The first retardation layer may satisfy the following relationship: 1.0≤Re(450) / Re(550)≤1.2 and 0.85≤Re(650) / Re(550)≤1.0, where Re(450), Re(550) and Re(650) represent the in-plane retardation values ​​at wavelengths of 450 nm, 550 nm and 650 nm, respectively.

[0032] The first retardation layer may include a cyclic olefin polymer film.

[0033] In Equation 1, the first retardation layer may have an nx value of 1.50 to 1.55, a ny value of 1.48 to 1.53, and a nz value of 1.48 to 1.53.

[0034] The first retardation layer and the second retardation layer may be sequentially stacked on the polarizer, or the second retardation layer and the first retardation layer may be sequentially stacked on the polarizer.

[0035] The polarizing plate may further include a protective film stacked on an upper surface of the polarizer.

[0036] Another embodiment of the present invention relates to an optical display device including the polarizing plate according to the present invention.

[0037] Effects of the Invention

[0038] The present invention provides a polarizing plate including a retardation layer which does not suffer from breakage when it is manufactured.

[0039] The invention provides a polarizing plate having good diagonal compensation and thermal stability when applied to a liquid crystal display.

[0040] The present invention provides a polarizing plate having a good effect on thickness reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 FIG. 4 is a cross-sectional view of a polarizing plate according to an embodiment of the present invention.

[0042] Figure 2 FIG. 4 is a cross-sectional view of an optical display device according to an embodiment of the present invention. DETAILED DESCRIPTION

[0043] Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement the present invention. It should be understood that the present invention can be implemented in many different ways and is not limited to the following embodiments. In the accompanying drawings, parts that are not related to this description will be omitted for clarity. Throughout the specification, the same components will be indicated by the same reference numerals. Although the length, thickness or width of various components may be exaggerated in the accompanying drawings for understanding, it should be understood that the present invention is not limited thereto.

[0044] In this document, spatially relative terms such as "upper" and "lower" are defined with reference to the accompanying drawings. Therefore, it should be understood that the term "upper surface" can be used interchangeably with the term "lower surface".

[0045] Herein, “in-plane retardation Re”, “out-of-plane retardation Rth” and “biaxiality NZ” are represented by equations A, B and C, respectively:

[0046] [Formula A]

[0047] Re=(nx-ny)×d,

[0048] [Formula B]

[0049] Rth=((nx+ny) / 2-nz)×d,

[0050] [Formula C]

[0051] NZ=(nx-nz) / (nx-ny),

[0052] Where nx, ny and nz are the refractive indices of the corresponding optical device in the slow axis direction, fast axis direction and thickness direction of the optical device at the measurement wavelength, and d is the thickness of the optical device (unit: nanometer). In equations A to C, the measurement wavelength can be 450 nanometers, 550 nanometers or 650 nanometers.

[0053] Herein, “short wavelength dispersion” refers to Re(450) / Re(550), and “long wavelength dispersion” refers to Re(650) / Re(550), wherein Re(450), Re(550) and Re(650) refer to the in-plane retardation (Re) values ​​of a single retardation layer or a stack of retardation layers at wavelengths of about 450 nm, 550 nm and 650 nm, respectively.

[0054] As used herein to denote angles, "+" means counterclockwise about a reference point, and "-" means clockwise about a reference point.

[0055] The expression "X to Y" used herein to express a specific numerical range means "X ≤ and ≤ Y".

[0056] The inventor of the present invention has invented a polarizing plate formed by stacking a first retardation layer and a second retardation layer on one surface of a polarizer, and controlling the retardation values ​​of the first retardation layer and the second retardation layer and the sum of the retardation values ​​of the first retardation layer and the second retardation layer at the same time, wherein the second retardation layer comprises a fluorene-based retardation layer. With such a structure, the retardation layer of the polarizing plate will not encounter fracture when the polarizing plate is manufactured, thereby improving the processability, diagonal compensation and screen quality of an optical display device including the polarizing plate, and the thermal stability of the polarizing plate or the first retardation layer and the second retardation layer as a whole without brightness loss.

[0057] Herein, "thermal stability" means that the absolute value of the change in the out-of-plane retardation (Rth) value of the first retardation layer and the second retardation layer as a whole is 10 nm or less, and when the polarizing plate or the first retardation layer and the second retardation layer as a whole are treated for 500 hours at 60°C and 95% relative humidity (RH), the polarizing plate shows a small brightness change in the black mode. The details of the measurement will be described in the examples.

[0058] Below, we will refer to Figure 1 A polarizing plate according to an embodiment of the present invention will be described.

[0059] refer to Figure 1 The polarizing plate includes a polarizer 130 , a protective film 140 stacked on an upper surface of the polarizer 130 , and a first retardation layer 110 and a second retardation layer 120 sequentially stacked on a lower surface of the polarizer 130 .

[0060] In one embodiment, the protective film is stacked on the light exiting surface of the polarizer, and the first retardation layer and the second retardation layer are stacked on the light incident surface of the polarizer.

[0061] In another embodiment, the protective film is stacked on the light incident surface of the polarizer, and the first retardation layer and the second retardation layer are stacked on the light exiting surface of the polarizer.

[0062] The second retardation layer 120 is stacked on the lower surface of the polarizer to protect the polarizer from the external environment while improving the mechanical properties of the polarizing plate. Figure 1 Although not shown in the figure, an adhesive layer, a bonding layer or an adhesive / bonding layer is further formed on the lower surface of the second retardation layer, so that the polarizing plate can be bonded to an optical member (e.g., a panel for a liquid crystal display, etc.) by bonding. The adhesive layer, the bonding layer or the adhesive / bonding layer can be formed by a typical method known to those skilled in the art.

[0063] The second retardation layer 120 includes a fluorene-based retardation layer, which is a non-crystalline layer. "Fluorene-based retardation layer" means that at least one of the base resins forming the second retardation layer includes a fluorene-based unit.

[0064] As is well known to those skilled in the art, "fluorene-based" means a moiety represented by Formula 1. In Formula 1, the substituent is omitted. Through the fluorene-based retardation layer, the second retardation layer can improve processability and economic feasibility when manufacturing a polarizing plate without breaking, compared to the second retardation layer formed of a typical acrylic film.

[0065] [Formula 1]

[0066]

[0067] In one embodiment, the second retardation layer is a fluorene-based retardation layer and is composed of a single layer. Herein, "single layer" means that the second retardation layer is composed of a fluorene-based retardation layer and does not include an additional retardation layer on one or both surfaces thereof.

[0068] The fluorene-based retardation layer can be formed of a composition including at least one base resin containing the above-mentioned fluorene-based part.

[0069] In one embodiment, the fluorene-based retardation layer is a non-acrylic retardation layer, and may be formed of a retardation layer composition including a fluorene-based ring-containing resin and an aromatic thermoplastic resin.

[0070] The fluorene-based delay layer may include a simple mixture (meaning unreacted state) of a fluorene-based ring-containing resin and an aromatic thermoplastic resin or a reaction product of a fluorene-based ring-containing resin and an aromatic thermoplastic resin. Preferably, the fluorene-based delay layer includes a simple mixture of the two types of resins, thereby improving the optical transparency of the second delay layer by the stable phase separation of the two types of resins.

[0071] In one embodiment, the resin containing fluorene rings may include polyester containing fluorene rings. The polyester containing fluorene rings may be formed by esterification of dicarboxylic acids and diols. The dicarboxylic acid may include fluorene dicarboxylic acid, which has a carboxylic acid group coupled to carbon No. 9 of the fluorene ring through a hydrocarbon group (e.g., an alkylene group).

[0072] In one embodiment, the fluorene-based dicarboxylic acid may include at least one selected from the group consisting of Formula 2 and Formula 3, but is not limited thereto:

[0073] [Formula 2]

[0074]

[0075] [Formula 3]

[0076]

[0077] In Formula 2 and Formula 3, R 1 and R 2 are each independently a monovalent substituent; k, m and n are each independently an integer from 0 to 4; and X 1 and X 2 Each is independently a divalent hydrocarbon group.

[0078] R 1 and R 2 can be independently cyano, halogen, C 1 To C 10 Alkyl or C 6 To C 10 Aryl. X 1 and X 2 Each independently may be a straight chain or branched chain C 1 To C 10 Alkylene. 1 , R 2 , X 1 and X 2 Can be independently selected from C 1 To C 10 Alkyl, C 6 To C 10 Aryl and C 3 To C 10 At least one of the cycloalkyl group is substituted.

[0079] In one embodiment, the fluorene dicarboxylic acid may include at least one 9,9-bis(carboxyl C 2 To C 6 9,9-bis(2-carboxypropyl)fluorene, for example, 9,9-bis(2-carboxyethyl)fluorene, 9,9-bis(2-carboxypropyl)fluorene, and the like.

[0080] The dicarboxylic acid may further include other dicarboxylic acids (non-fluorene dicarboxylic acids) that do not contain a fluorene moiety so as not to affect the effects of the present invention. For example, the non-fluorene dicarboxylic acid may include at least one selected from the group consisting of aromatic dicarboxylic acids, polycyclic aromatic dicarboxylic acids, and aliphatic dicarboxylic acids, but is not limited thereto.

[0081] The fluorene dicarboxylic acid may be present in an amount of 10 mol% or more, preferably 90 mol% to 100 mol%, based on the total amount of the dicarboxylic acid. Within this range, the fluorene dicarboxylic acid can ensure the advantageous effects of the present invention.

[0082] The diol may include a diol containing a 9,9-biarylfluorene ring, wherein the alcohol group is coupled to carbon 9 of the fluorene ring through a hydrocarbon group (eg, an arylene group). The diol containing a 9,9-biarylfluorene ring may be represented by Formula 4, but is not limited thereto:

[0083] [Formula 4]

[0084]

[0085] Wherein in Formula 4, Z is an aromatic hydrocarbon group; R 3 and R 4 are each independently a monovalent substituent; p is an integer from 0 to 4; R 5 is an alkylene group; and q and r are each independently 0 or 1 or an integer greater than 1.

[0086] In Formula 4, Z represents a monocyclic aromatic hydrocarbon group, such as a phenyl group, or a polycyclic aromatic hydrocarbon group, such as a naphthyl group, anthracenyl group, biphenyl group, etc. 3 Can be cyano, halogen, C 1 To C 10 Alkyl or C 6 To C 10 aryl; and R 4 Is a halogen, straight chain or branched C 1 To C 10 Alkyl, C 6 To C 20 Aryl, C 7 To C 20 Arylalkyl, C 1 To C 10 Alkoxy, C 1 To C 10 Alkylthio, C 6 To C 10 Arylthio, C 2 To C 10 Acyl, nitro, cyano, amine, etc., but not limited thereto. 5 Can be straight chain or branched C 2 To C 10 Alkylene.

[0087] In one embodiment, the diol containing a 9,9-bis(arylfluorene ring) may include at least one of the following: 9,9-bis(hydroxy-alkylphenyl)fluorene, such as 9,9-bis(hydroxyphenyl)fluorene, 9,9-bis(hydroxymethylphenyl)fluorene, 9,9-bis(hydroxyisopropylphenyl)fluorene, 9,9-bis(hydroxydimethylphenyl)fluorene, etc.; 9,9-bis(hydroxyarylphenyl)fluorene, such as 9,9-bis(hydroxyphenylphenyl)fluorene, etc.; and 9,9-bis(hydroxynaphthyl)fluorene, but is not limited thereto.

[0088] The diol may further include at least one type of diol not containing a fluorene group (non-fluorene diol) so as not to affect the effects of the present invention. For example, the non-fluorene diol may include at least one of alkane diol, alkylene diol and polyalkylene diol, but is not limited thereto.

[0089] The polyester containing fluorene rings can be prepared by esterification of dicarboxylic acid and diol. The esterification can be performed by esterification of acid and alcohol known to those skilled in the art.

[0090] The aromatic thermoplastic resin may include at least one selected from aromatic polyether, aromatic polyester, aromatic polycarbonate and aromatic polyamide, preferably aromatic polycarbonate. Preferably, the aromatic thermoplastic resin includes aromatic polycarbonate to improve compatibility with the fluorene ring-containing dicarboxylic acid.

[0091] The fluorene ring-containing resin may be present in an amount of 50 to 90 parts by weight, and the aromatic thermoplastic resin may be present in an amount of 10 to 50 parts by weight, based on a total of 100 parts by weight of the fluorene ring-containing resin and the aromatic thermoplastic resin. Within these ranges, the fluorene ring-containing resin and the aromatic thermoplastic resin can effectively achieve the desired stability and delay of the second delay layer according to the present invention.

[0092] For example, based on 100 parts by weight of the fluorene ring-containing resin and the aromatic thermoplastic resin, the fluorene ring-containing resin may be present in an amount of 50 parts by weight, 51 parts by weight, 52 parts by weight, 53 parts by weight, 54 parts by weight, 55 parts by weight, 56 parts by weight, 57 parts by weight, 58 parts by weight, 59 parts by weight, 60 parts by weight, 61 parts by weight, 62 parts by weight, 63 parts by weight, 64 parts by weight, 65 parts by weight, 66 parts by weight, 67 parts by weight, 68 parts by weight, 69 parts by weight, 70 parts by weight, 71 parts by weight, 72 parts by weight, 73 parts by weight, 74 parts by weight, 75 parts by weight, 76 parts by weight, 77 parts by weight, 78 parts by weight, 79 parts by weight, 80 parts by weight, 81 parts by weight, 82 parts by weight, 83 parts by weight, 84 parts by weight, 85 parts by weight, 86 parts by weight, 87 parts by weight, 88 parts by weight, 89 parts by weight, or 90 parts by weight.

[0093] In addition to the fluorene ring-containing resin and the aromatic thermoplastic resin, the delay layer composition may further include typical additives such as plasticizers, stabilizers, flame retardants, antistatic agents, fillers, foaming agents, defoamers, lubricants, release agents, and the like.

[0094] The second retardation layer may have a thickness of 10 to 60 micrometers, preferably 20 to 40 micrometers. Within this range, the second retardation layer allows the thickness of the polarizing plate to be reduced, can be used in the polarizing plate, and can ensure uniform retardation in the film.

[0095] The second retardation layer may be formed of a retardation layer composition. The formation of the second retardation layer will be described in detail below.

[0096] According to the present invention, compared to the case in the prior art where a liquid crystal layer or an acrylic film is used as the second retardation layer, the second retardation layer includes a fluorene-based retardation layer to prevent embrittlement and fracture of the second retardation layer, and to control the retardation value of each of the first retardation layer and the second retardation layer and the first retardation layer and the second retardation layer as a whole, so as to improve the diagonal compensation function of the polarizing plate while significantly improving the overall thermal stability of the polarizing plate. Next, the retardation of each of the first retardation layer and the second retardation layer will be described in detail.

[0097] The first retardation layer 110 is stacked on a lower surface of the polarizer to protect the polarizer from the external environment while improving the mechanical properties of the polarizing plate.

[0098] The first retardation layer 110 is a negative B plate and can satisfy Equation 1 to improve the diagonal compensation function of the polarizing plate together with the second retardation layer while helping to prevent brightness loss:

[0099] [Equation 1]

[0100] NX>NY>NZ,

[0101] In Equation 1, nx, ny and nz are the refractive indices of the first retardation layer in the slow axis direction, the fast axis direction and the thickness direction at a wavelength of 550 nanometers, respectively.

[0102] In Equation 1, the first retardation layer may have an nx value of 1.50 to 1.55, preferably 1.51 to 1.54, a ny value of 1.48 to 1.53, preferably 1.49 to 1.52, and a nz value of 1.48 to 1.53, preferably 1.49 to 1.52. Within this range, the first retardation layer can ensure improvement in lateral contrast.

[0103] For example, in Equation 1, the first retardation layer may have an nx value of 1.50, 1.51, 1.52, 1.53, 1.54, or 1.55. For example, in Equation 1, the first retardation layer may have an ny value of 1.48, 1.49, 1.50, 1.51, 1.52, or 1.53. For example, in Equation 1, the first retardation layer may have an nz value of 1.48, 1.49, 1.50, 1.51, 1.52, or 1.53.

[0104] The first delay layer 110 may have an in-plane delay value of 50 to 60 nanometers and an out-of-plane delay value of 120 to 150 nanometers at a wavelength of 550 nanometers. Within this range, the laminate of the first delay layer and the fluorene-based delay layer can easily achieve the sum of the in-plane delay values ​​and the sum of the out-of-plane delay values ​​according to the present invention. Preferably, the first delay layer has an in-plane delay value of 52 to 57 nanometers and an out-of-plane delay value of 120 to 135 nanometers. For example, the first delay layer may have an in-plane delay value of 50 nanometers, 51 nanometers, 52 nanometers, 53 nanometers, 54 nanometers, 55 nanometers, 56 nanometers, 57 nanometers, 58 nanometers, 59 nanometers or 60 nanometers at a wavelength of 550 nanometers. For example, the first retardation layer may have an out-of-plane retardation value of 120 nm, 121 nm, 122 nm, 123 nm, 124 nm, 125 nm, 126 nm, 127 nm, 128 nm, 129 nm, 130 nm, 131 nm, 132 nm, 133 nm, 134 nm, 135 nm, 136 nm, 137 nm, 138 nm, 139 nm, 140 nm, 141 nm, 142 nm, 143 nm, 144 nm, 145 nm, 146 nm, 147 nm, 148 nm, 149 nm or 150 nm at a wavelength of 550 nm.

[0105] The first retardation layer 110 may have a biaxiality of 1 to 4, preferably 1.03 to 3, at a wavelength of 550 nanometers. Within this range, the first retardation layer 110 can ensure improvement in lateral contrast. For example, the first retardation layer 110 may have a biaxiality of 1, 1.5, 2, 2.5, 3, 3.5, or 4.

[0106] The first retardation layer 110 may include a protective coating layer formed by coating an actinic radiation curable composition onto a release film and then curing it. However, to facilitate the formation of the second retardation layer, the first retardation layer may be a film formed of an optically transparent resin.

[0107] In one embodiment, the first delay layer may include a stretched film formed by melt extruding a composition containing an optically transparent resin and then stretching it. For example, the polymer resin may include a polycarbonate resin, a polyester resin including polyethylene terephthalate, polyethylene naphthalate, etc., a polyamide resin, a polyarylate resin, a polyimide resin, a polyethylene resin, a polyolefin resin including polypropylene, etc., and at least one of a cyclic olefin polymer (COP). Preferably, the polymer resin includes a cyclic olefin polymer to reduce the delay variation when evaluating the durability while ensuring the stable delay uniformity on the front side of the polarizing plate. The composition may also include typical additives known to those skilled in the art, such as ultraviolet (UV) stabilizers, antioxidants, etc.

[0108] The first delay layer 110 can be formed by uniaxial or biaxial stretching of an unstretched film made by melt extrusion of a composition. In uniaxial or biaxial stretching, the unstretched film can be stretched to ensure the elongation of the first delay layer. For example, the uniaxial stretching of the unstretched film can be performed by uniaxial stretching in the machine direction (machine direction, MD) to an elongation of 1.5 times to 3 times, preferably 1.8 times to 2 times of its initial length. The biaxial stretching of the unstretched film can be performed by sequentially or simultaneously stretching to 1.3 times to 4 times the MD elongation and 1.3 times to 4 times the TD elongation in the MD and transverse directions (transverse direction, TD).

[0109] The first retardation layer 110 is a stretched film having a slow axis and a fast axis in its plane. In one embodiment, assuming that the MD of the first retardation layer is 0°, the first retardation layer may have a slow axis tilted at an angle of -5° to +5°, preferably -1° to +1°. Within this range, the first retardation layer 110 can ensure an improvement in the front contrast ratio. For example, the slow axis of the first retardation layer 110 can be tilted at an angle of -3°, -2°, -1°, 0°, +1°, +2° or +3°.

[0110] In the stack of the first retardation layer 110 and the second retardation layer, the first retardation layer 110 allows adjustment of visibility on a black screen by adjusting wavelength dispersion and retardation together.

[0111] In one embodiment, the first retardation layer may have a short wavelength dispersion Re(450) / Re(550) satisfying the following relationship: 1.0≤Re(450) / Re(550)≤1.2, preferably 1.0≤Re(450) / Re(550)≤1.1. In one embodiment, the first retardation layer may have a long wavelength dispersion Re(650) / Re(550) satisfying the following relationship: 0.85≤Re(650) / Re(550)≤1.0, preferably 0.90≤Re(650) / Re(550)≤1.0. Within this range, the first retardation layer can further improve visibility on a black screen.

[0112] For example, the first retardation layer may have a short wavelength dispersion (Re(450) / Re(550)) of 1.0, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, 1.11, 1.12, 1.13, 1.14, 1.15, 1.16, 1.17, 1.18, 1.19, or 1.2.

[0113] For example, the first retardation layer may have a long wavelength dispersion (Re(650) / Re(550)) of 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, or 1.0.

[0114] The first delay layer 110 may have a thickness of 10 microns to 50 microns, preferably 15 microns to 40 microns. Within this range, the first delay layer 110 can be used in a polarizing plate and can ensure uniform delay in the film. For example, the first delay layer may have a thickness of 10 microns, 11 microns, 12 microns, 13 microns, 14 microns, 15 microns, 16 microns, 17 microns, 18 microns, 19 microns, 20 microns, 21 microns, 22 microns, 23 microns, 24 microns, 25 microns, 26 microns, 27 microns, 28 microns, 29 microns, 30 microns, 31 microns, 32 microns, 33 microns, 34 microns, 35 microns, 36 microns, 37 microns, 38 microns, 39 microns, 40 microns, 41 microns, 42 microns, 43 microns, 44 microns, 45 microns, 46 microns, 47 microns, 48 ​​microns, 49 microns or 50 microns.

[0115] In one embodiment, the first retardation layer may be free of one or more thermal stabilizers.

[0116] The second retardation layer 120 is a negative B plate and can satisfy Equation 2 to improve the diagonal compensation function of the polarizing plate together with the first retardation layer while helping to prevent brightness loss:

[0117] [Equation 2]

[0118] nz>nx>ny,

[0119] In Equation 2, nx, ny and nz are the refractive indices of the second retardation layer in the slow axis direction, the fast axis direction and the thickness direction at a wavelength of 550 nanometers, respectively.

[0120] In Equation 2, the second retardation layer 120 may have an nx value of 1.59 to 1.61, preferably 1.60 to 1.61, a ny value of 1.59 to 1.61, preferably 1.60 to 1.61, and a nz value of 1.61 to 1.63, preferably 1.61 to 1.62. Within this range, the second retardation layer 120 may suppress brightness in a black mode. For example, in Equation 2, the second retardation layer may have an nx value of 1.59, 1.591, 1.592, 1.593, 1.594, 1.595, 1.596, 1.597, 1.598, 1.599, 1.600, 1.601, 1.602, 1.603, 1.604, 1.605, 1.606, 1.607, 1.608, 1.609, or 1.61. For example, in Equation 2, the second retardation layer may have a ny value of 1.59, 1.591, 1.592, 1.593, 1.594, 1.595, 1.596, 1.597, 1.598, 1.599, 1.600, 1.601, 1.602, 1.603, 1.604, 1.605, 1.606, 1.607, 1.608, 1.609, or 1.61. For example, in Equation 2, the second retardation layer may have a nz value of 1.61, 1.611, 1.612, 1.613, 1.614, 1.615, 1.616, 1.617, 1.618, 1.619, 1.62, 1.621, 1.622, 1.623, 1.624, 1.625, 1.626, 1.627, 1.628, 1.629, or 1.63.

[0121] The second retardation layer 120 may have an in-plane retardation value of 50 to 60 nanometers and an out-of-plane retardation value of -150 to -120 nanometers at a wavelength of 550 nanometers. Within this range, the laminate of the first retardation layer and the second retardation layer can easily achieve the sum of the in-plane retardation value and the sum of the out-of-plane retardation value according to the present invention. Preferably, the second retardation layer has an in-plane retardation value of 53 to 58 nanometers and an out-of-plane retardation value of -135 to -115 nanometers.

[0122] For example, the second retardation layer may have an in-plane retardation value of 50 nanometers, 51 nanometers, 52 nanometers, 53 nanometers, 54 nanometers, 55 nanometers, 56 nanometers, 57 nanometers, 58 nanometers, 59 nanometers, or 60 nanometers at a wavelength of 550 nanometers. For example, the second retardation layer may have an out-of-plane retardation value of -150 nm, -149 nm, -148 nm, -147 nm, -146 nm, -145 nm, -144 nm, -143 nm, -142 nm, -141 nm, -140 nm, -139 nm, -138 nm, -137 nm, -136 nm, -135 nm, -134 nm, -133 nm, -132 nm, -131 nm, -130 nm, -129 nm, -128 nm, -127 nm, -126 nm, -125 nm, -124 nm, -123 nm, -122 nm, -121 nm or -120 nm at a wavelength of 550 nm.

[0123] The second retardation layer may have a biaxiality of -3 to 0, preferably -2.6 to -1.8, -2 to -0.1 at a wavelength of 550 nanometers. Within this range, the second retardation layer can ensure an improvement in lateral contrast. For example, the second retardation layer may have a biaxiality of -3, -2.9, -2.8, -2.7, -2.6, -2.5, -2.4, -2.3, -2.2, -2.1, -2.0, -1.9, -1.8, -1.7, -1.6, -1.5, -1.4, -1.3, -1.2, -1.1, -1.0, -0.9, -0.8, -0.7, -0.6, -0.5, -0.4, -0.3, -0.2, -0.1 or 0 at a wavelength of 550 nanometers.

[0124] By controlling the retardation and wavelength dispersion of the polarizing plate, the second retardation layer can improve the diagonal compensation function of the polarizing plate together with the first retardation layer.

[0125] In one embodiment, the second retardation layer may have a short wavelength dispersion Re(450) / Re(550) satisfying the following relationship: 1.0≤Re(450) / Re(550)≤1.2, preferably 1.1≤Re(450) / Re(550)≤1.18. In one embodiment, the second retardation layer may have a long wavelength dispersion Re(650) / Re(550) satisfying the following relationship: 0.85≤Re(650) / Re(550)≤1.0, preferably 0.90≤Re(650) / Re(550)≤0.95. Within this range, the second retardation layer can ensure maximum front black visibility.

[0126] For example, the second retardation layer may have a short wavelength dispersion Re(450) / Re(550) of 1.0, 1.01, 1.02, 1.03, 1.04, 1.05, 1.06, 1.07, 1.08, 1.09, 1.1, 1.11, 1.12, 1.13, 1.14, 1.15, 1.16, 1.17, 1.18, 1.19, or 1.2.

[0127] For example, the second retardation layer may have a long wavelength dispersion Re(650) / Re(550) of 0.85, 0.86, 0.87, 0.88, 0.89, 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, or 1.0.

[0128] The second retardation layer has a slow axis and a fast axis in its plane. In one embodiment, assuming that the machine direction (MD) of the second retardation layer is set at an angle of 0°, the slow axis of the second retardation layer can be tilted at an angle of 87° to 93°, preferably 89° to 91°. Within this range, the second retardation layer can ensure an improvement in front contrast. For example, the slow axis of the second retardation layer is tilted at an angle of 87°, 88°, 89°, 90°, 91°, 92° or 93°.

[0129] In one embodiment, assuming that the slow axis of the first retardation layer is set at an angle of 0°, the slow axis of the second retardation layer can be tilted at an angle of -5° to +5°, preferably -3° to +3°. Within this range, the second retardation layer can improve the contrast of all azimuth angles. For example, the slow axis of the second retardation layer can be tilted at an angle of -5°, -4°, -3°, -2°, -1°, 0°, +1°, +2°, +3°, +4° or +5°.

[0130] In one embodiment, the second retarder layer may be free of one or more thermal stabilizers.

[0131] In the laminate of the first retardation layer and the second retardation layer, the sum of the in-plane retardation value of the first retardation layer at a wavelength of 550 nanometers and the in-plane retardation value of the second retardation layer at a wavelength of 550 nanometers may be in the range of 100 nanometers to 110 nanometers, and the sum of the out-of-plane retardation value of the first retardation layer at a wavelength of 550 nanometers and the out-of-plane retardation value of the second retardation layer at a wavelength of 550 nanometers may be in the range of -30 nanometers to +10 nanometers. When both the sum of the in-plane retardation value and the sum of the out-of-plane retardation value are satisfied, when applied to an optical display device, the polarizing plate can improve the thermal stability of the polarizing plate while ensuring a good diagonal compensation function of the polarizing plate.

[0132] For example, in a stack of a first delay layer and a second delay layer, the sum of the in-plane delay value of the first delay layer at a wavelength of 550 nanometers and the in-plane delay value of the second delay layer at a wavelength of 550 nanometers may be 100 nanometers, 101 nanometers, 102 nanometers, 103 nanometers, 104 nanometers, 105 nanometers, 106 nanometers, 107 nanometers, 108 nanometers, 109 nanometers or 110 nanometers.

[0133] For example, in a stack of a first delay layer and a second delay layer, the sum of the out-of-plane delay value of the first delay layer at a wavelength of 550 nm and the out-of-plane delay value of the second delay layer at a wavelength of 550 nm may be -30 nm, -29 nm, -28 nm, -27 nm, -26 nm, -25 nm, -24 nm, -23 nm, -22 nm, -21 nm, -20 nm, -19 nm, -18 nm, -17 nm, -16 nm, -15 nm, -14 nm, -13 nm, -12 nm, -11 nm, -10 nm, -9 nm, -8 nm, -7 nm, -6 nm, -5 nm, -4 nm, -3 nm, -2 nm, -1 nm, 0 nm, +1 nm, +2 nm, +3 nm, +4 nm, +5 nm, +6 nm, +7 nm, +8 nm, +9 nm or +10 nm.

[0134] Specifically, the first retardation layer and the second retardation layer are stacked on one surface of the polarizer so that the first retardation layer and the second retardation layer as a whole can achieve a diagonal compensation function. To this end, it is necessary not only to adjust the refractive index of the second retardation layer related to the in-plane retardation and the out-of-plane retardation in the slow axis direction and the fast axis direction, but also to adjust its thickness. In addition, the thickness of the second retardation layer can be adjusted to improve thermal stability. The inventors of the present invention have confirmed that even in a structure in which the second retardation layer includes a fluorene-based retardation layer, when the sum of the in-plane retardation values ​​of the first retardation layer and the second retardation layer and the sum of their out-of-plane retardation values ​​are not within the scope of the present invention, the polarizing plate will suffer from deterioration of the diagonal compensation function and thermal stability.

[0135] In one embodiment, the stack of the first retardation layer and the second retardation layer in the polarizing plate may have an absolute value of the change in out-of-plane retardation value of 10 nm or less, for example, 0 nm to 10 nm, calculated by Equation 3, thereby improving the thermal stability of the polarizing plate:

[0136] [Equation 3]

[0137] Absolute value of out-of-plane retardation change = |Rth(0 hours)–Rth(500 hours)|,

[0138] In Formula 3, Rth(0 hours) indicates the out-of-plane retardation value (unit: nanometer) of the laminate of the first retardation layer and the second retardation layer in the polarizing plate at a wavelength of 550 nanometers, and

[0139] Rth(500 hours) indicates an out-of-plane retardation value (unit: nanometer) at a wavelength of 550 nanometers of a laminate of the first retardation layer and the second retardation layer in the polarizing plate measured after the polarizing plate is left at 60° C. and 95% RH for 500 hours.

[0140] For example, the laminate may have an absolute value of the change in out-of-plane retardation value calculated by Equation 3 of 0 nm, 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, or 10 nm.

[0141] Preferably, the sum of the in-plane retardation values ​​is in the range of 105 nm to 110 nm, and the sum of the out-of-plane retardation values ​​is in the range of -30 nm to +5 nm, -25 nm to +0 nm, -20 nm to -5 nm or -10 nm to +10 nm, more preferably -10 nm to -5 nm.

[0142] Next, the production of a stacked body of the first retardation layer and the second retardation layer will be described.

[0143] According to the present invention, the second retardation layer is directly stacked on the first retardation layer without an adhesive layer therebetween, thereby making it possible to easily achieve the above-mentioned sum of in-plane retardation values ​​and the sum of out-of-plane retardation values ​​and improve thermal stability while reducing the thickness of the polarizing plate.

[0144] In one embodiment, a stack of a first delay layer and a second delay layer can be manufactured by coating the second delay layer composition to a predetermined thickness on an unstretched film or a partially stretched film for the first delay layer, and then stretching the unstretched film or the partially stretched film and the coating for the second delay layer as a whole (so that the angle defined between the absorption axis of the polarizer and the slow axis of the first delay layer becomes the same as the angle defined between the absorption axis of the polarizer and the slow axis of the second delay layer).

[0145] In another embodiment, a stack of a first delay layer and a second delay layer can be manufactured by coating the first delay layer composition to a predetermined thickness on an unstretched film or a partially stretched film for the second delay layer, and then stretching the unstretched film or the partially stretched film and the coating for the first delay layer as a whole (so that the angle defined between the absorption axis of the polarizer and the slow axis of the first delay layer becomes the same as the angle defined between the absorption axis of the polarizer and the slow axis of the second delay layer).

[0146] In another embodiment, the polarizing plate can be made by stretching the first delay layer in TD, bonding the stretched first delay layer to the polarizer so that the slow axis of the first delay layer is inclined at right angles to the absorption axis of the polarizer, stretching the second delay layer in MD (for example: with a slow axis inclined at 90°), and bonding the second delay layer to the first delay layer by a roll-to-roll process.

[0147] Alternatively, the polarizing plate can be made by stretching the second delay layer in MD, bonding the stretched second delay layer to a polarizer so that the slow axis of the second delay layer is tilted at right angles to the absorption axis of the polarizer, stretching the first delay layer in TD (e.g., with a slow axis tilted at 90°), and bonding the first delay layer to the second delay layer by a roll-to-roll process.

[0148] The polarizer 130 is used to convert natural light or polarized light into polarized light by linear polarization in a specific direction, and can be produced by a polymer film substantially containing a polyvinyl alcohol resin. Specifically, the polarizer 130 can be produced by dyeing the polymer film with iodine or a dichroic dye and then stretching the film in MD. Specifically, the polarizer can be produced by swelling, dyeing, stretching, and cross-linking.

[0149] The polarizer 130 may have a total transmittance of about 43% or more, such as about 43% to about 50%, and a polarization degree of about 99% or more, such as about 99% to about 100%. Within this range, the polarizer may be combined with the first retardation layer and the second retardation layer to improve the anti-reflection performance of the polarizing plate.

[0150] The polarizer 130 may have a thickness of about 2 micrometers to about 30 micrometers, specifically about 4 micrometers to about 25 micrometers. Within this range, the polarizer may be used in a polarizing plate.

[0151] In one embodiment, assuming that the absorption axis of the polarizer is set at an angle of 0°, the first retardation layer may have a slow axis tilted at an angle of 87° to 93°, preferably 89° to 91°. Within this range, the polarizing plate can improve the front contrast. For example, the slow axis of the first retardation layer can be tilted at an angle of 87°, 88°, 89°, 90°, 91°, 92°, or 93°.

[0152] In another embodiment, assuming that the absorption axis of the polarizer is set at an angle of 0°, the second retardation layer may have a slow axis tilted at an angle of 87° to 93°, preferably 89° to 91°. Within this range, the polarizing plate can perform a diagonal compensation function (reducing the brightness when observing sideways in black). For example, the slow axis of the second retardation layer can be tilted at an angle of 87°, 88°, 89°, 90°, 91°, 92°, or 93°.

[0153] In one embodiment, an axis defined between an absorption axis of the polarizer and a slow axis of the first retardation layer may be the same as an axis defined between an absorption axis of the polarizer and a slow axis of the second retardation layer.

[0154] The protective film 140 is formed on the upper surface of the polarizer to protect the polarizer from the external environment while improving the mechanical strength of the polarizing plate.

[0155] The protective film 140 is used to protect the polarizer from the external environment, and may be an optically transparent film formed of, for example, at least one resin selected from the following: cellulose resins including triacetylcellulose (TAC), polyester resins including polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, cyclic polyolefin resins, polycarbonate resins, polyether sulfone 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.

[0156] The protective film 140 may have a thickness of about 5 micrometers to about 70 micrometers, specifically about 15 micrometers to about 45 micrometers. Within this range, the protective film can be used in a polarizing plate.

[0157] Despite Figure 1 Although not shown in the figure, a functional coating may be further formed on the upper surface of the protective film to provide additional functions to the polarizing plate. For example, the functional coating may include a hard coating, an anti-fingerprint layer, and an anti-reflection layer. These functional coatings may be stacked alone or in combination. The protective film may be attached to the polarizer via an adhesive layer. The adhesive layer may be formed of a water-based or UV-curable adhesive, but is not limited thereto.

[0158] In addition, despite the Figure 1 Not shown in the drawings, a protective film or a protective coating may be further formed between the polarizer 130 and the first retardation layer 110 .

[0159] In addition, despite the Figure 1 Although not shown in the figure, a primer layer is further formed on one surface of each of the first retardation layer and the second retardation layer to improve adhesion between the retardation layers.

[0160] Next, a polarizing plate according to another embodiment of the present invention will be described.

[0161] According to this embodiment, the polarizing plate includes a polarizer, a protective film stacked on an upper surface of the polarizer, a second retardation layer stacked on a lower surface of the polarizer, and a first retardation layer stacked on a lower surface of the second retardation layer. The polarizing plate according to this embodiment is substantially the same as Figure 1 Polarizer shown.

[0162] Next, an optical display device according to the present invention will be explained.

[0163] The optical display device according to the present invention may include a polarizing plate according to an embodiment of the present invention, and may include, for example, a liquid crystal display. The liquid crystal display may include a liquid crystal panel, an observer-side polarizing plate stacked on a light exit surface of the liquid crystal panel, and a light source-side polarizing plate stacked on a light incident surface of the liquid crystal panel. The polarizing plate according to the present invention may be used as an observer-side polarizing plate or a light source-side polarizing plate, preferably located between a liquid crystal cell and a polarizing plate, the polarizing plate being arranged in the same direction as the alignment direction of the liquid crystal in the liquid crystal cell. When used as a light source-side polarizing plate, the polarizing plate according to the present invention can achieve a further reduction in brightness in a black mode.

[0164] refer to Figure 2 , an optical display device according to an embodiment of the present invention will be described.

[0165] refer to Figure 2 , the optical display device includes a liquid crystal panel 210, a light source side polarizing plate 220 and an observer side polarizing plate 230. Figure 2 Although not shown in the figure, the optical display device may include a backlight unit that is disposed below the polarizing plate on the light source side and includes a light source.

[0166] The liquid crystal panel may adopt a typical structure including an upper substrate, a liquid crystal layer and a lower substrate. The liquid crystal layer may include an in-plane switching (IPS) liquid crystal layer and a fringe field switching (FFS) liquid crystal layer, but is not limited thereto.

[0167] The light source side polarizing plate includes a polarizing plate according to an embodiment of the present invention. Figure 2 Although not shown in the figure, the second retardation layer, the first retardation layer, the polarizer and the protective film may be sequentially stacked on the liquid crystal panel. Alternatively, the first retardation layer, the second retardation layer, the polarizer and the protective film may be sequentially stacked on the liquid crystal panel.

[0168] The observer-side polarizing plate may include a polarizing plate well known to those skilled in the art. For example, the polarizing plate may include a polarizer and a protective film stacked on one or both surfaces of the polarizer.

[0169] Mode for Carrying Out the Invention

[0170] Next, the present invention will be described in more detail with reference to examples. However, it should be noted that these examples are provided for illustration only and should not be construed as limiting the present invention in any way.

[0171] Example 1

[0172] A polyvinyl alcohol film (PS#60, pre-stretched thickness: 60 μm, Kuraray Co., Ltd., Japan) was stretched to 6 times its original length in an iodine aqueous solution at 55° C., thereby preparing a 12 μm thick polarizer having a transmittance of 45%.

[0173] A cyclic polyolefin film (RX4500, JSR) was used as a film forming the first delay layer. A second delay layer composition (OKP, Osaka Gas Chemicals Co., Ltd.) was prepared, which contained 50 parts by weight of a fluorene ring-containing resin and 50 parts by weight of an aromatic polycarbonate based on 100 parts by weight of the layer composition.

[0174] The second retardation layer composition was coated on one surface of the first retardation layer to a predetermined thickness, followed by drying and stretching, thereby forming a laminate including the second retardation layer directly formed on the first retardation layer. Re, Rth, NZ (at 550 nm), short wavelength dispersion, and long wavelength dispersion of each of the first retardation layer and the second retardation layer were measured using an AxoScan polarimeter (Axometrics Co., Ltd.).

[0175] As a protective film, a PET film is bonded to the upper surface of the polarizer, and a laminate of a first retardation layer and a second retardation layer is stacked on the lower surface of the polarizer, thereby manufacturing a polarizing plate. In the polarizing plate, the first retardation layer and the second retardation layer are stacked on the polarizer in sequence. Here, the slow axis of the first retardation layer is parallel to the slow axis of the second retardation layer.

[0176] Example 2

[0177] The second delay layer was formed by the same process as in Example 1, except that a film containing a fluorene ring-containing resin and aromatic polycarbonate (OKP, Osaka Gas Chemical Co., Ltd.) was used, and the first delay layer was formed by the same process as in Example 1, except that a composition containing a cycloolefin polymer resin (RX, JSR) was used.

[0178] The first retardation layer composition was coated on one surface of the second retardation layer to a predetermined thickness, followed by drying and stretching, thereby forming a laminate including the second retardation layer directly formed on the first retardation layer. Re, Rth, NZ (at 550 nm), short wavelength dispersion, and long wavelength dispersion of each of the first retardation layer and the second retardation layer were measured using an Aikescan polarimeter (Aikematics Co., Ltd.).

[0179] Example 3

[0180] A polarizing plate was manufactured by the same process as Example 1, except that the retardation and the wavelength dispersion of each of the first retardation layer and the second retardation layer were changed as listed in Table 1.

[0181] Example 4

[0182] A polarizing plate was manufactured by the same process as Example 1, except that the second retardation layer and the first retardation layer were sequentially stacked on the polarizer.

[0183] Comparative Examples 1 and 2

[0184] A polarizing plate was fabricated by the same process as in Example 1, except that the retardation and wavelength dispersion of the second retardation layer were changed as listed in Table 2.

[0185] Comparative Example 3

[0186] A polarizing plate was manufactured by the same process as in Example 1, except that a second delay layer was formed using an acrylic film (I-film, OPTES, Re: 55 nm, Rth: -135 nm, NZ: -2.0, nz>nx>ny, Re(450) / Re(550): 1.1, Re(650) / Re(550): 0.95) and stacked on the first delay layer.

[0187] The polarizing plates of Examples and Comparative Examples were evaluated for the following properties, and the results are shown in Tables 1 and 2.

[0188] (1) Fracture of the delay layer: The fracture of the polarizing plate produced in the examples and comparative examples was evaluated. The laminate of the first delay layer and the second delay layer was cut into a cubic shape of 10 cm × 10 cm (length × width), and an adhesive tape (Ichibang, Nitto Co., Ltd.) was attached to one surface of the delay layer in the polarizing plate. 10 vertical lines and 10 horizontal lines were drawn on the laminate of the first delay layer and the second delay layer to divide the laminate into a total of 100 sheets by cutting the laminate to the depth of the delay layer. After removing the adhesive tape, the number of sheets remaining on the polarizing plate was counted. Fewer sheets indicate fewer fractures in the delay layer.

[0189] (2) Diagonal compensation function (unit: nit) Each of the polarizing plates produced in the examples and comparative examples was mounted on the light exit surface of an IPS liquid crystal panel (LTM270HL02, Samsung Electronics Co., Ltd.). Here, the polarizing plate was mounted on the light exit surface of the IPS liquid crystal panel so that the first retardation layer and the second retardation layer were placed thereon. A polarizing plate of a laminate including TAC-polarizer-TAC was mounted on the light incident surface of the IPS liquid crystal panel. The brightness at an azimuth angle of 30° was measured in a black mode (dark state) at the same polar angle of 60°. In Table 1, a lower value indicates a better diagonal compensation function.

[0190] (3) Thermal stability (unit: nanometer): The stack of the first delay layer and the second delay layer was left at 60°C and 95% RH for 500 hours, and then the change in the out-of-plane delay value was calculated according to Equation 3: |Rth(0 hours)–Rth(500 hours)|.

[0191] [Table 1]

[0192]

[0193] [Table 2]

[0194]

[0195] *In Tables 1 and 2, the sum of the in-plane retardation values ​​indicates the in-plane retardation value of the first retardation layer + the in-plane retardation value of the second retardation layer.

[0196] *In Tables 1 and 2, the sum of the out-of-plane retardation values ​​indicates the out-of-plane retardation value of the first retardation layer + the out-of-plane retardation value of the second retardation layer.

[0197] *In Tables 1 and 2, the first retardation layer satisfies nx>ny>nz, and the second retardation layer satisfies nz>nx>ny.

[0198] As shown in Table 1, when applied to a liquid crystal display, the polarizing plate according to the present invention does not suffer from the breakage of the retardation layer and ensures good diagonal compensation function and thermal stability.

[0199] On the contrary, as shown in Table 2, compared with the polarizing plate of the example, the polarizing plates of Comparative Examples 1 and 2 that failed to meet the sum of the in-plane retardation values ​​of the first retardation layer and the second retardation layer according to the present invention suffered from significant degradation of the diagonal compensation function; and compared with the polarizing plate of the example, the polarizing plate of Comparative Example 3 including an acrylic retardation layer as the second retardation layer suffered from significant breakage of the retardation layer and degradation of the diagonal compensation function, and had poor thermal stability.

[0200] Although some embodiments have been described herein, it should be understood that various modifications, changes, variations, and equivalent embodiments may be made by those skilled in the art without departing from the spirit and scope of the invention.

Claims

1. A polarizing plate, comprising: polarizer; as well as A stack of a first retardation layer and a second retardation layer is stacked on the lower surface of the polarizer, Wherein the first delay layer satisfies equation 1, and the second delay layer satisfies equation 2: [Equation 1] NX>NY>NZ, Wherein in Equation 1, nx, ny and nz are the refractive indices of the first retardation layer in its slow axis direction, fast axis direction and thickness direction at a wavelength of 550 nanometers, [Equation 2] nz>nx>ny, Wherein in Equation 2, nx, ny and nz are the refractive indices of the second retardation layer in its slow axis direction, fast axis direction and thickness direction at a wavelength of 550 nanometers; The sum of the in-plane retardation values ​​of the first retardation layer and the second retardation layer at a wavelength of 550 nanometers is in the range of 100 nanometers to 110 nanometers, The sum of the out-of-plane retardation values ​​of the first retardation layer and the second retardation layer at a wavelength of 550 nanometers is in the range of -30 nanometers to +10 nanometers, and The second retardation layer comprises a fluorene-based retardation layer, The first delay layer satisfies the following relationship: 1.0≤Re(450) / Re(550)≤1.2 and 0.85≤Re(650) / Re(550)≤1.0, wherein Re(450), Re(550) and Re(650) respectively indicate the in-plane delay values ​​at wavelengths of 450 nanometers, 550 nanometers and 650 nanometers. 2 . The polarizing plate according to claim 1 , wherein the second retardation layer is directly formed on the first retardation layer. 3 . The polarizing plate according to claim 1 , wherein when the first retardation layer has a slow axis disposed at an angle of 0°, the second retardation layer has a slow axis inclined at an angle of −5° to +5°. 4 . The polarizing plate according to claim 1 , wherein the second retardation layer has an in-plane retardation value of 50 nm to 60 nm and an out-of-plane retardation value of −150 nm to −120 nm at a wavelength of 550 nm. 5 . The polarizing plate of claim 1 , wherein the second retardation layer has a biaxiality of −3 to 0 at a wavelength of 550 nanometers.

6. The polarizing plate according to claim 1, wherein the second retardation layer satisfies the following relationship: 1.0≤Re(450) / Re(550)≤1.2 and 0.85≤Re(650) / Re(550)≤1.0, wherein Re(450), Re(550) and Re(650) respectively indicate the in-plane retardation values ​​at wavelengths of 450 nanometers, 550 nanometers and 650 nanometers. 7 . The polarizing plate of claim 1 , wherein in Equation 2, the second retardation layer has an nx value of 1.59 to 1.61, a ny value of 1.59 to 1.61, and a nz value of 1.61 to 1.

63. 8 . The polarizing plate according to claim 1 , wherein the second retardation layer comprises a fluorene ring-containing resin and an aromatic thermoplastic resin. 9 . The polarizing plate according to claim 1 , wherein when the polarizer has an absorption axis disposed at an angle of 0°, the polarizer has a slow axis tilted at an angle of 87° to 93°. 10 . The polarizing plate according to claim 1 , wherein the first retardation layer has an in-plane retardation value of 50 nm to 60 nm and an out-of-plane retardation value of 120 nm to 150 nm at a wavelength of 550 nm. The polarizing plate according to claim 1 , wherein the first retardation layer comprises a cycloolefin polymer film. 12 . The polarizing plate of claim 1 , wherein in Equation 1, the first retardation layer has an nx value of 1.50 to 1.55, a ny value of 1.48 to 1.53, and a nz value of 1.48 to 1.

53. 13 . The polarizing plate according to claim 1 , wherein the first retardation layer and the second retardation layer are sequentially stacked on the polarizer, or the second retardation layer and the first retardation layer are sequentially stacked on the polarizer.

14. The polarizing plate according to claim 1, further comprising: A protective film is stacked on an upper surface of the polarizer.

15. An optical display device, comprising the polarizing plate according to any one of claims 1 to 14.

16. The optical display device according to claim 15, comprising: LCD panel; and The polarizing plate is stacked on a light incident surface of the liquid crystal panel.

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