Polarizing plate and optical display device including the same

Abstract

A polarizing plate and an optical display device including the same are provided. The polarizing plate includes: a polarizer; and a laminate of a first retardation layer and a second retardation layer stacked in sequence on the lower surface of the polarizer, and a third retardation layer, wherein the first retardation layer may have a slow axis inclined at an angle of about +40° to +50° or about -50° to -40° with respect to the absorption axis or the transmission axis of the polarizer, the slow axis of the first retardation layer is inclined at an angle of about +80° to +100° or about -100° to -80° with respect to the slow axis of the second retardation layer, the first retardation layer exhibits positive wavelength dispersion and has an in-plane retardation of about 50 nm to 100 nm at a wavelength of about 550 nm, and the second retardation layer has positive wavelength dispersion or flat wavelength dispersion and has an in-plane retardation of about 180 nm to 240 nm at a wavelength of about 550 nm.

Description

Technical Field

[0001] The present invention relates to a polarizing plate and an optical display device including the polarizing plate. More specifically, the present invention relates to a polarizing plate and an optical display device including the polarizing plate, which can significantly reduce the reflectance in all directions including its side surfaces, and at the same time significantly improve the ellipticity. Background Art

[0002] OLED displays require a polarizing plate to improve the screen quality by preventing electrode reflection. For the anti-reflection function, the polarizing plate needs a circular polarizing plate function. To implement a circular polarizing plate, two methods are typically used in the prior art, namely, a method using a positive wavelength dispersion material and a method using a negative wavelength dispersion material.

[0003] In a conventional method for implementing a circular polarizing plate, a negative wavelength dispersion λ / 4 retardation layer and a positive C-plate are sequentially stacked on the lower surface of a polarizer. This method has the following problems: poor processability because it is difficult to attach to the polarizer by roll-to-roll processing, insufficient strength of the retardation layer serving as the lower protective film of the polarizer, and limited improvement in reflectance and ellipticity. In another method, a λ / 2 retardation layer and a λ / 4 retardation layer are sequentially stacked on the lower surface of the polarizer. However, this method has the problem of high reflectance in all directions including the side surfaces of the polarizing plate. On the other hand, in a circular polarizing plate, a liquid crystal layer can be formed as a λ / 4 retardation layer, a λ / 2 retardation layer, or a positive C-plate. However, this method requires an alignment layer and has the following problems: after coating each layer, an additional process for sequentially transferring these layers to the polarizer is required.

[0004] The background art of the present invention is disclosed in Korean Patent Publication No. 2007-0052254, etc. Summary of the Invention

[0005] Technical Challenges

[0006] An object of the present invention is to provide a polarizing plate that exhibits a very low reflectance in all directions including its side surfaces.

[0007] Another object of the present invention is to provide a polarizing plate that exhibits a very high ellipticity in all directions including its side surfaces.

[0008] A further object of the present invention is to provide a polarizing plate including a polarizer protective film that can reduce the thickness of the polarizing plate while ensuring its good processability and mechanical strength.

[0009] Means for Solving the Problems

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

[0011] 1. The polarizing plate includes: a polarizer; and a laminate of a first retardation layer and a second retardation layer stacked in sequence on the lower surface of the polarizer and a third retardation layer, wherein the first retardation layer may have a slow axis inclined at an angle of +40° to +50° or -50° to -40° with respect to the absorption axis or the transmission axis of the polarizer, the slow axis of the first retardation layer is inclined at an angle of +80° to +100° or -100° to -80° with respect to the slow axis of the second retardation layer, the first retardation layer exhibits positive wavelength dispersion and has an in-plane retardation of 50 nm to 100 nm at a wavelength of 550 nm, and the second retardation layer exhibits positive wavelength dispersion or flat wavelength dispersion and has an in-plane retardation of 180 nm to 240 nm at a wavelength of 550 nm.

[0012] 2. In 1, the first retardation layer, the second retardation layer, and the third retardation layer may be stacked in sequence on the polarizer in that order.

[0013] 3. In 1 to 2, the second retardation layer, the first retardation layer, and the third retardation layer may be stacked in sequence on the polarizer in that order.

[0014] 4. In 1 - 3, the third retardation layer may be a positive C plate and may have an out-of-plane retardation of -100 nm to -10 nm at a wavelength of 500 nm.

[0015] 5. In 1 to 4, the first retardation layer may be a negative A plate.

[0016] 6. In 1 - 5, the second retardation layer may be a positive A plate or a negative B plate.

[0017] 7. In 1 to 6, the first retardation layer may satisfy Equation 1:

[0018] Re(450) / Re(550) ≥ 1.1, ---- (1)

[0019] where Re(450) and Re(550) are the in-plane retardations of the first retardation layer at a wavelength of 450 nm and at a wavelength of 550 nm, respectively.

[0020] 8. In 1 to 7, the first retardation layer may have a biaxiality of -0.5 to 0 at a wavelength of 550 nm.

[0021] 9. In 1 to 8, the second retardation layer may satisfy Equation 3:

[0022] 0.95 ≤ Re(450) / Re(550) ≤ 1.03, ---- (3)

[0023] wherein Re(450) and Re(550) are the in-plane retardations of the second retardation layer at a wavelength of 450 nm and the in-plane retardation at a wavelength of 550 nm, respectively.

[0024] 10. Among 1 to 9, the second retardation layer may have a biaxiality of 1.0 to 1.4 at a wavelength of 550 nm.

[0025] 11. Among 1 to 10, the slow axis of the second retardation layer may be inclined at an angle of +40° to +50°, inclined at an angle of -50° to -40°, inclined at an angle of +130° to +140°, or inclined at an angle of -140° to -130° with respect to the absorption axis or the transmission axis of the polarizer.

[0026] 12. Among 1 to 11, assuming that the absorption axis of the polarizer is set at an angle of 0°, the slow axis of the first retardation layer may be inclined at an angle of +40° to +50° and the angle defined between the slow axis of the first retardation layer and the slow axis of the second retardation layer may be in the range of +80° to +100°.

[0027] 13. Among 1 to 12, the laminate of the first retardation layer and the second retardation layer may have an in-plane retardation of 100 nm to 180 nm at a wavelength of 550 nm.

[0028] 14. Among 1 to 13, the laminate of the first retardation layer and the second retardation layer may have a biaxiality of -0.2 to 1.4 at a wavelength of 550 nm.

[0029] 15. Among 1 to 14, each of the first retardation layer and the third retardation layer may be an amorphous layer.

[0030] 16. Among 1 to 15, each of the first retardation layer and the third retardation layer may include a coating formed of a composition, the composition including at least one selected from the group consisting of a substituted or unsubstituted styrene resin, a substituted or unsubstituted (meth)acrylonitrile resin, a substituted or unsubstituted (meth)acrylic alkyl ester resin including (meth)acrylic acid methyl ester, and a cellulose resin.

[0031] 17. In 16, the composition may further include an additive having an aromatic group.

[0032] 18. Among 1 to 17, the second retardation layer may include an MD uniaxially stretched film or an obliquely stretched film.

[0033] 19. Among 1 to 18, each of the first retardation layer, the second retardation layer, and the third retardation layer may include a primer layer on at least one of its surfaces.

[0034] Another embodiment of the present invention relates to an optical display device including a polarizing plate according to the present invention.

[0035] Effects of the present application

[0036] The present invention provides a polarizing plate that exhibits a very low reflectance in all directions including its side surfaces.

[0037] The present invention provides a polarizing plate that exhibits a very high ellipticity in all directions including its side surfaces.

[0038] The present invention provides a polarizing plate including a polarizer protective film, and the polarizer protective film can reduce the thickness while ensuring good processability and mechanical strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 is a cross-sectional view of a polarizing plate according to an embodiment of the present invention.

[0040] Figure 2 is a diagram showing Figure 1 the angles defined between the absorption axis of the polarizer, the slow axis of the first layer, and the slow axis of the second layer in the polarizing plate shown.

[0041] Figure 3 is a cross-sectional view of a polarizing plate according to another embodiment of the present invention. DETAILED DESCRIPTION

[0042] Embodiments of the present invention will be described in detail with reference to the drawings so that those skilled 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. In the drawings, parts irrelevant to the description will be omitted for clarity. Throughout the specification, the same components will be denoted by the same reference symbols. Although the lengths, thicknesses, or widths of various components may be exaggerated in the drawings for understanding, it should be understood that the present invention is not limited thereto.

[0043] Herein, spatial relative terms such as "upper" and "lower" are defined with reference to the drawings. Therefore, it should be understood that the term "upper surface" can be used interchangeably with the term "lower surface".

[0044] In this text, "in-plane retardation Re", "out-of-plane retardation Rth", and "biaxiality NZ" are represented by equations A, B, and C respectively:

[0045] Re = (nx - ny) × d, --- (A)

[0046] Rth = ((nx + ny) / 2 - nz) × d, --- (B)

[0047] NZ = (nx - nz) / (nx - ny), --- (C)

[0048] (where nx, ny, and nz represent the refractive indices of the corresponding optical component at the measurement wavelength in the slow axis direction, fast axis direction, and thickness direction of the optical component respectively, and d represents the thickness of the optical component (unit: nanometer)). In equations A to C, the measurement wavelength can be 450 nanometers, 550 nanometers, or 650 nanometers.

[0049] As used herein to represent an angle, relative to 0°, "+" represents the counterclockwise direction around the reference point, and "-" represents the clockwise direction around the reference point.

[0050] As used herein to represent a specific numerical range, the expression "X to Y" means "X ≤ and ≤ Y".

[0051] Based on the following confirmation, the inventors of the present invention completed the present invention: By using a structure in which a laminate of a first retardation layer and a second retardation layer and a third retardation layer are sequentially stacked on one surface of a polarizer (especially on its display panel side surface), by controlling the wavelength dispersion and in-plane retardation of each of the first retardation layer and the second retardation layer, the angle between the absorption axis of the polarizer and the slow axis of the first retardation layer, and the angle between the slow axis of the first retardation layer and the slow axis of the second retardation layer within the scope of the present invention, the polarizing plate can significantly reduce the reflectance in all directions including its side surface, and at the same time significantly improve the ellipticity. In addition, the polarizing plate according to the present invention includes a first retardation layer, a second retardation layer, and a third retardation layer on one surface of the polarizer, so as to allow the manufacture of the polarizing plate by roll-to-roll processing, thereby improving the processability and at the same time ensuring good mechanical strength of the layer as a protective film for the polarizer.

[0052] In one embodiment, the polarizing plate may include a polarizer; and a first retardation layer, a second retardation layer, and a third retardation layer sequentially stacked on the lower surface of the polarizer.

[0053] In another embodiment, the polarizing plate may include a polarizer; and a second retardation layer, a first retardation layer, and a third retardation layer sequentially stacked on the lower surface of the polarizer.

[0054] Hereinafter, reference will be made toFigure 1 To describe a polarizing plate according to an embodiment of the present invention.

[0055] Referring to Figure 1 , the polarizing plate may include a polarizer 140; and a first retardation layer 110, a second retardation layer 120, and a third retardation layer 130 sequentially stacked on the lower surface of the polarizer 140.

[0056] Although not shown in Figure 1 , the third retardation layer 130 includes an adhesive layer and / or a bonding layer on its lower surface to stack the polarizing plate on an adherend (e.g., an optical display panel including a light-emitting component panel, etc.).

[0057] In the polarizing plate, a certain angular relationship is satisfied among the absorption axis or transmission axis of the polarizer, the slow axis of the first retardation layer, and the slow axis of the second retardation layer. Hereinafter, this will be described with reference to Figure 2 this.

[0058] Referring to Figure 2 , the slow axis 110a of the first retardation layer 110 is inclined at an angle α of +40° to +50° or -50° to -40° with respect to the absorption axis 140a of the polarizer 140, and the angle β defined between the slow axis 110a of the first retardation layer 110 and the slow axis 120a of the second retardation layer 120 may be in the range of +80° to +100° or -100° to -80°. In the polarizing plate according to the present invention, when the polarizing plate including all of the first retardation layer, the second retardation layer, and the third retardation layer has the angles α and β within the above ranges, the reflectance and ellipticity in all directions including its side surfaces can be significantly improved.

[0059] In one embodiment, the angle α may be in the range of +42° to +48°, specifically in the range of +43° to +47°, preferably +45°. In another embodiment, the angle α may be in the range of -48° to -42°, especially in the range of -47° to -43°, preferably -45°.

[0060] In one embodiment, the angle β may be in the range of +83° to +97°, specifically in the range of +85° to +95°, preferably +90°. In another embodiment, the angle β may be in the range of -97° to -83°, especially in the range of -95° to -85°, preferably -90°.

[0061] Figure 2Shows the angle defined between the absorption axis of the polarizer and the slow axis of the first retardation layer. As an alternative, the tilt angle of the slow axis of the first retardation layer can be set with reference to the transmission axis of the polarizer. Preferably, the tilt angle of the slow axis of the first retardation layer is set with reference to the absorption axis of the polarizer.

[0062] In one embodiment, assuming that the absorption axis of the polarizer is set at an angle of 0°, the slow axis of the first retardation layer can be tilted at an angle α of +40° to +50° with respect to the absorption axis of the polarizer (e.g., +40°, +41°, +42°, +43°, +44°, +45°, +46°, +47°, +48°, +49°, or +50°), and the angle β between the slow axis of the first retardation layer and the slow axis of the second retardation layer can be in the range of +80° to +100° (e.g., +80°, +85°, +90°, +95°, or +100°).

[0063] In another embodiment, assuming that the absorption axis of the polarizer is set at an angle of 0°, the slow axis of the first retardation layer can be tilted at an angle α of -40° to -50° and the angle β between the slow axis of the first retardation layer and the slow axis of the second retardation layer can be in the range of -80° to -100°.

[0064] On the other hand, the inventors of the present invention have confirmed that when the polarizing plate is applied to an optical display, the polarizing plate can improve the reflectance and ellipticity only by controlling the above three types of angles. Therefore, for each of the first retardation layer and the second retardation layer, the wavelength dispersion and the in-plane retardation at a wavelength of 550 nm are controlled. In particular, in the polarizing plate according to the present invention, it has been confirmed that by having a first retardation layer and a second retardation layer with an in-plane retardation in a range significantly different from the λ / 2 in-plane retardation and the λ / 4 in-plane retardation known in the art at a wavelength of 550 nm and simultaneously controlling the wavelength dispersion of each of the first retardation layer and the second retardation layer, the reflectance and ellipticity of the polarizing plate can be significantly improved.

[0065] Hereinafter, the first retardation layer, the second retardation layer, the third retardation layer, and the polarizer of the polarizing plate will be described in detail.

[0066] First retardation layer

[0067] The first retardation layer 110 exhibits positive wavelength dispersion and has an in-plane retardation of 50 nm to 100 nm (e.g., 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, or 100 nm) at a wavelength of 550 nm. Here, "positive wavelength dispersion" means that the in-plane retardation gradually decreases as the wavelength increases from 450 nm to 650 nm.

[0068] In one embodiment, the first retardation layer may exhibit positive wavelength dispersion at a wavelength of 450 nm to 550 nm.

[0069] In one embodiment, the first retardation layer may exhibit positive wavelength dispersion or flat wavelength dispersion at a wavelength of 550 nm to 650 nm.

[0070] The first retardation layer is used to improve the ellipticity and reflectance of the polarizing plate at its side surfaces. In particular, the first retardation layer 110 has an in-plane retardation different from that of a typical λ / 4 in-plane retardation at a wavelength of 550 nm, and exhibits positive wavelength dispersion, thereby improving the reflectance and ellipticity of the polarizing plate. For example, at a wavelength of 550 nm, the first retardation layer 110 may have an in-plane retardation of 50 nm to 90 nm, particularly 50 nm to 80 nm, and more particularly 50 nm to 70 nm.

[0071] In one embodiment, the first retardation layer 110 may satisfy the following relational expression 1:

[0072] [Relational expression 1]

[0073] Re(450) / Re(550) ≥ 1.1

[0074] 0.9 ≤ Re(650) / Re(550) < 1.0 or Re(650) / Re(550) = 1.0

[0075] Wherein, Re(450), Re(550), and Re(650) are the in-plane retardation values of the first retardation layer at wavelengths of 450 nm, 550 nm, and 650 nm, respectively.

[0076] When the first retardation layer 110 satisfies the relational expression 1, the first retardation layer 110 can be used to improve the ellipticity and reflectance of the polarizing plate at its side surfaces.

[0077] In one embodiment, the range of Re(450) / Re(550) may be from 1.1 to 1.4, preferably from 1.2 to 1.3. Within this range, the polarizing plate may exhibit a good antireflection effect.

[0078] In one embodiment, the range of Re(650) / Re(550) may be from 0.9 to 1.0, preferably from 0.93 to less than 1.0. Within this range, the polarizing plate may exhibit a good antireflection effect.

[0079] For example, the first retardation layer may have Re(450) of 60 nm to 90 nm, particularly 70 nm to 80 nm, and Re(650) of 40 nm to 70 nm, particularly 50 nm to 60 nm. Within this range, the polarizing plate may exhibit a good antireflection effect.

[0080] As the negative A plate (-A plate), the first retardation layer 110 can satisfy the relational expression 2:

[0081] nx ≒ nz > ny, --- (2)

[0082] wherein, nx represents the refractive index of the first retardation layer in its slow axis direction, ny represents the refractive index of the first retardation layer in its fast axis direction, and nz represents the refractive index of the first retardation layer in its thickness direction. These refractive indices are measured at a wavelength of 550 nm.

[0083] When the -A plate is used as the first retardation layer, the polarizing plate can exhibit a further improved antireflection effect.

[0084] The first retardation layer 110 can have an out-of-plane retardation of -100 nm to 0 nm, particularly -80 nm to -20 nm, preferably -60 nm to -30 nm at a wavelength of 550 nm. Within this range, the polarizing plate can exhibit a good antireflection effect.

[0085] The first retardation layer 110 can have a biaxiality of -0.5 to 0, particularly -0.4 to 0 at a wavelength of 550 nm. Within this range, the polarizing plate can exhibit a good antireflection effect.

[0086] The first retardation layer 110 can be a film or a coating. Here, the "coating" means a layer formed by coating a first retardation layer composition on a second retardation layer or a base film and curing it. Preferably, the first retardation layer is a coating to allow reduction of the thickness of the polarizing plate. The first retardation layer 110 can have a thickness of 30 μm or less than 30 μm, for example, a thickness greater than 0 μm to 10 μm. Within this range, the first retardation layer 110 can be used in the polarizing plate and can reduce the thickness of the polarizing plate.

[0087] When the first retardation layer 110 is a film, the first retardation layer 110 can be formed by stretching an optically transparent unstretched resin film so that the resin film exhibits the above-described characteristics including in-plane retardation. Here, the stretching can include uniaxial stretching, biaxial stretching, or oblique stretching. For example, the resin film can include at least one selected from the group consisting of polyester resins such as polycarbonate, polyethylene terephthalate, and polyethylene naphthalate, polyamide resins, polyarylate resins, polyimide resins, polyolefin resins such as polyethylene and polypropylene, and cyclic olefin polymers (COP).

[0088] When the first retardation layer 110 is a coating, the first retardation layer 110 can include a coating formed from a composition containing a monomer, oligomer, or resin for the coating.

[0089] In one embodiment, the first retardation layer 110 may be an amorphous layer. When the first retardation layer is formed of liquid crystal, an alignment layer needs to be formed to align the liquid crystal at a specific angle, and foreign substances may be generated.

[0090] The monomer, oligomer or resin for the coating may include at least one selected from the group consisting of substituted or unsubstituted styrene resins, substituted or unsubstituted (meth)acrylonitrile resins, substituted or unsubstituted (meth)acrylic alkyl esters including (meth)methyl acrylate, and cellulose resins, preferably substituted or unsubstituted cellulose resins, for example, cellulose ester resins. The cellulose ester resin can be easily implemented as the first retardation layer according to the present invention and the stack of the first retardation layer and the second retardation layer can be easily formed by stretching both the first retardation layer film and the second retardation layer film after coating the first retardation layer composition on the second retardation layer film. Herein, substitution means that at least one hydrogen atom is substituted by a halogen atom, a straight-chain or branched C1 to C 20 alkyl group, a C6 to C 20 aryl group, an acyl group containing a straight-chain or branched C1 to C 20 alkyl group, or an acyl group containing a C6 to C 20 aryl group, but not limited thereto.

[0091] In one embodiment, the first retardation layer may be formed of a composition including a cellulose ester compound.

[0092] In another embodiment, the first retardation layer may be formed of a composition including a cellulose ester compound and a compound containing an aromatic condensed ring.

[0093] The cellulose ester compound may include at least one selected from the group consisting of cellulose ester resins, cellulose ester oligomers, and cellulose ester monomers.

[0094] The cellulose ester compound refers to a condensation product obtained by the reaction between the hydroxyl group on the cellulose ester and the carboxyl group of a carboxylic acid. The cellulose ester compound may be regioselectively substituted or randomly substituted. The regioselectivity can be measured by determining the relative degree of substitution at the C6, C3, and C2 positions on the cellulose ester by carbon-13 NMR.

[0095] The cellulose ester compound can be prepared by a typical method of contacting a cellulose solution with at least one C1-C 20 acylating agent for a sufficient contact time to provide a cellulose ester having a desired degree of substitution and a desired degree of polymerization. Preferably, the acylating agent includes at least one straight-chain or branched C1 to C 20An alkyl or aryl carboxylic anhydride, carboxylic acid halide, diketone or acetoacetate. Examples of carboxylic anhydrides may include acetic anhydride, propionic anhydride, butyric anhydride, isobutyric anhydride, valeric anhydride, hexanoic anhydride, 2-ethylhexanoic anhydride, nonanoic anhydride, lauric anhydride, palmitic anhydride, stearic anhydride, benzoic anhydride, substituted benzoic anhydride, phthalic anhydride and isophthalic anhydride. Examples of carboxylic acid halides may include acetyl chloride, propionyl chloride, butyryl chloride, hexanoyl chloride, 2-ethylhexanoyl chloride, lauroyl chloride, palmitoyl chloride, benzoyl chloride, substituted benzoyl chloride and stearoyl chloride. Examples of acetoacetates may include methyl acetoacetate, ethyl acetoacetate, propyl acetoacetate, butyl acetoacetate and tert-butyl acetoacetate. Preferably, the acylating agent may include a straight-chain or branched C2 to C9 alkyl carboxylic anhydride, such as acetic anhydride, propionic anhydride, butyric anhydride, 2-ethylhexanoic anhydride, nonanoic anhydride and stearic anhydride.

[0096] Preferably, the cellulose ester compound includes, for example, cellulose acetate (CA), cellulose acetate propionate (CAP) and cellulose acetate butyrate (CAB), but is not limited thereto.

[0097] In one embodiment, the cellulose ester compound may include at least two acyl substituents. At least one of the acyl groups may include an aromatic substituent, and in the cellulose ester compound, the relative degree of substitution (RDS) may be set in the order of C6>C2>C3. C6 means the degree of substitution at the 6-carbon position in the cellulose ester, C2 means the degree of substitution at the 2-carbon position in the cellulose ester, and C3 means the degree of substitution at the 3-carbon position in the cellulose ester. The aromatic compound may include benzoate or substituted benzoate.

[0098] In another embodiment, the cellulose ester compound may include a regioselectively substituted cellulose ester compound having (a) a plurality of chromophore-acyl substituents and (b) a plurality of pivaloyl substituents.

[0099] The cellulose ester compound may have a degree of hydroxy substitution of about 0.1 to about 1.2 and a degree of chromophore-acyl substitution of about 0.4 to about 1.6; the difference between the sum of the degree of chromophore-acyl substitution at the 2-carbon in the cellulose ester compound and the degree of chromophore-acyl substitution at the 3-carbon in the cellulose ester compound and the degree of chromophore-acyl substitution at the 6-carbon in the cellulose ester compound may range from about 0.1 to about 1.6; and the chromophore-acyl may be selected from (i), (ii), (iii), and (iv):

[0100] (i) (C6-C 20 ) aryl-acyl, wherein the aryl is unsubstituted or substituted with 1-5 R 1 substituents;

[0101] (ii) Heteroaryl, wherein the heteroaryl is a 5- to 10-membered ring having 1 to 4 heteroatoms selected from N, O, and S, and is unsubstituted or substituted with 1 to 5 R 1 substituted;

[0102] (iii)

[0103] wherein Aryl is C 1- C6 aryl and is unsubstituted or substituted with 1 - 5 R 1 substituted; and

[0104] (iv)

[0105] wherein Heteroaryl is a 5- to 10-membered ring having 1 to 4 heteroatoms selected from N, O, and S, and is unsubstituted or substituted with 1 to 5 R 1 substituted;

[0106] R 1 each independently is nitro, cyano, (C1-C6)alkyl, halo(C1-C6)alkyl, (C6-C 20 )aryl-CO2-, (C6-C 20 )aryl, (C1-C6)alkoxy, halo(C1-C6)alkoxy, halogen, a 5- to 10-membered heteroaryl having 1 - 4 heteroatoms selected from N, O, and S, or

[0107] In one embodiment, the chromophore-acyl group can be unsubstituted or substituted benzoyl or unsubstituted or substituted naphthyl.

[0108] In one embodiment, the chromophore-acyl group can be selected from the group consisting of:

[0109]

[0110]

[0111] and

[0112]

[0113] wherein * represents the connection site of the chromophore-acyl group substituent to the oxygen of the cellulose ester.

[0114] The first retardation layer may further comprise an additive containing an aromatic condensed ring.

[0115] The additive containing an aromatic condensed ring is used to adjust the retardation exhibition rate and wavelength dispersion of the first retardation layer.

[0116] The additive containing an aromatic condensed ring may include naphthalene, anthracene, phenanthrene, pyrene, the compound represented by Formula 1 or the compound represented by Formula 2. The additive containing an aromatic condensed ring may include 2-naphthyl benzoate, the 2,6-naphthalenedicarboxylic acid diester represented by Formula 3, naphthalene and the abietic acid ester represented by Formula 4, but is not limited thereto:

[0117] [Formula 1]

[0118]

[0119] [Formula 2]

[0120]

[0121] [Formula 3]

[0122]

[0123] (In Formula 3, R is a C1 to C 20 alkyl group or a C6 to C 20 aryl group, and n is an integer from 0 to 6.)

[0124] [Formula 4]

[0125]

[0126] (In Formula 4, R is a C1 to C 20 alkyl group or a C6 to C 20 aryl group.)

[0127] Preferably, the additive containing an aromatic condensed ring includes an additive having an aromatic ring, for example, at least one selected from the following: naphthalene, anthracene, phenanthrene, pyrene, 2-naphthyl benzoate and the 2,6-naphthalenedicarboxylic acid diester represented by Formula 3.

[0128] In the first retardation layer, the content of the additive containing an aromatic condensed ring may be 0.1 wt% to 30 wt%, preferably 10 wt% to 30 wt%. Within this range, the additive can improve the thermal stability of the composition and the retardation of the polarizing plate per thickness, and can adjust the wavelength dispersion.

[0129] The first retardation layer 110 may further include at least one typical additive known to those skilled in the art, for example, at least one selected from the following: ultraviolet absorber, wavelength dispersion regulator, polymerization inhibitor, antioxidant, heat stabilizer, plasticizer, anti-sticking agent, slip agent, lubricant and retardation enhancer, but is not limited thereto.

[0130] The first retardation layer 110 may be composed of a single layer or multiple layers.

[0131] Although in Figure 1Not shown in the figure, a primer layer may be formed on at least one surface of the first retardation layer 110. The primer layer is used to enhance the adhesion strength or bonding strength between the first retardation layer and the polarizer or between the first retardation layer and the second retardation layer. The primer layer may be formed of resins known to those skilled in the art, such as acrylic resins, polyurethane resins, acrylic polyurethane resins, ester resins, and ethyleneimine resins, but not limited thereto. The thickness of the primer layer can be adjusted within a range that does not affect the reduction of the thickness of the polarizing plate and its adhesion strength. For example, the primer layer may have a thickness of 10 nanometers to 500 nanometers, particularly 50 nanometers to 300 nanometers.

[0132] The first retardation layer 110 may be directly formed on the second retardation layer 120 without an adhesive layer or a bonding layer, or may be formed on the second retardation layer 120 via an adhesive layer (e.g., a PSA (pressure-sensitive adhesive) layer) or a bonding layer. In this context, the expression "directly formed on" means that there is no adhesive layer or bonding layer between the first retardation layer and the second retardation layer.

[0133] Second retardation layer

[0134] The second retardation layer 120 exhibits positive wavelength dispersion or flat wavelength dispersion and has an in-plane retardation of 180 nanometers to 240 nanometers (e.g., 180 nanometers, 190 nanometers, 200 nanometers, 210 nanometers, 220 nanometers, 230 nanometers, or 240 nanometers) at a wavelength of 550 nanometers. "Positive wavelength dispersion" is the same as described above. "Flat wavelength dispersion" means that the in-plane retardation does not substantially increase or decrease as the wavelength increases from 450 nanometers to 650 nanometers.

[0135] The second retardation layer 120 is used to improve the ellipticity and reflectivity of the polarizing plate at its side surfaces. In particular, the second retardation layer 120 has an in-plane retardation different from the typical λ / 2 in-plane retardation at a wavelength of 550 nanometers and exhibits positive wavelength dispersion or flat wavelength dispersion, thereby improving the reflectivity and ellipticity of the polarizing plate. For example, at a wavelength of 550 nanometers, the second retardation layer 120 may have an in-plane retardation of 180 nanometers to 230 nanometers, particularly 180 nanometers to 220 nanometers.

[0136] In one embodiment, the second retardation layer 120 may satisfy the following relational expression 3:

[0137] [Relational expression 3]

[0138] 0.95 ≤ Re(450) / Re(550) ≤ 1.03

[0139] 0.95 ≤ Re(650) / Re(550) ≤ 1.03

[0140] Among them, Re(450), Re(550), and Re(650) are the in-plane retardation values of the second retardation layer at wavelengths of 450 nm, 550 nm, and 650 nm, respectively.

[0141] When the second retardation layer 120 satisfies Equation 3, the second retardation layer 120 can be used to improve the ellipticity and reflectivity of the polarizing plate at its side surface.

[0142] In one embodiment, the range of Re(450) / Re(550) can be from 0.95 to 1.03, preferably from 0.97 to 1.03. Within this range, the polarizing plate can exhibit good antireflection effects.

[0143] In one embodiment, the range of Re(650) / Re(550) can be from 0.95 to 1.03, preferably from 0.97 to 1.03. Within this range, the polarizing plate can exhibit good antireflection effects.

[0144] For example, the second retardation layer can have Re(450) of 180 nm to 240 nm, particularly 200 nm to 230 nm, and Re(650) of 180 nm to 240 nm, particularly 190 nm to 230 nm.

[0145] As a positive A plate (+A plate) or a negative B plate (-B plate), the second retardation layer 120 can satisfy Equation 4 or 5:

[0146] nx > ny ≒ nz, --- (4)

[0147] nx > ny > nz, --- (5)

[0148] Among them, nx represents the refractive index of the second retardation layer in its slow axis direction, ny represents the refractive index of the second retardation layer in its fast axis direction, and nz represents the refractive index of the second retardation layer in its thickness direction. These refractive indices are measured at a wavelength of 550 nm.

[0149] When using a +A plate or a -B plate as the second retardation layer, the polarizing plate can exhibit further improved antireflection effects.

[0150] The second retardation layer 120 can have an out-of-plane retardation of 50 nm to 250 nm, particularly 80 nm to 200 nm, preferably 100 nm to 180 nm at a wavelength of 550 nm. Within this range, the polarizing plate can exhibit good antireflection effects.

[0151] The second retardation layer 120 may have a birefringence of 1.0 to 1.4 (e.g., 1.1, 1.2, 1.3, or 1.4), particularly greater than 1.0 to 1.4, at a wavelength of 550 nm. Within this range, the polarizing plate can exhibit a good antireflection effect.

[0152] Relative to the absorption axis or the transmission axis of the polarizer, the second retardation layer 120 may have a slow axis inclined at an angle of +40° to +50° (e.g., +40°, +41°, +42°, +43°, +44°, +45°, +46°, +47°, +48°, +49°, or +50°), a slow axis inclined at an angle of -50° to -40° (e.g., -50°, -49°, -48°, -47°, -46°, -45°, -44°, -43°, -42°, -41°, or -40°), a slow axis inclined at an angle of +130° to +140° (e.g., +131°, +132°, +133°, +134°, +135°, +136°, +137°, +138°, +139°, or 140°), or a slow axis inclined at an angle of -140° to -130° (e.g., -140°, -139°, -138°, -137°, -136°, -135°, -134°, -133°, -132°, -131°, or -130°).

[0153] The second retardation layer 120 may be a film or a coating. Preferably, the second retardation layer is a film that helps to form the first retardation layer and the third retardation layer in the polarizing plate. The second retardation layer 120 may have a thickness of 60 μm or less, e.g., a thickness greater than 0 μm to 50 μm. Within this range, the second retardation layer 120 can be used in the polarizing plate and can be used as the lower protective film of the polarizing plate.

[0154] When the second retardation layer 120 is a film, the second retardation layer 120 can be formed by stretching an optically transparent unstretched resin film such that the resin film exhibits the above-described properties including in-plane retardation, etc. Here, the stretching may include uniaxial stretching, biaxial stretching, or oblique stretching. Preferably, the resin film may include a resin film containing a cycloolefin polymer (COP). Preferably, the second retardation layer is an MD uniaxially stretched film or an obliquely stretched film.

[0155] In one embodiment, the second retardation layer 120 may have a retardation performance rate (the ratio of the change in the in-plane retardation of the second retardation layer to the change in the thickness of the second retardation layer) of greater than or equal to 5 nm / μm, preferably greater than 5 nm / μm, e.g., 5 nm / μm to 20 nm / μm. Within this range, the second retardation layer can have a thin thickness, thereby enabling the reduction of the thickness of the polarizing plate.

[0156] The second retardation layer 120 may further include at least one typical additive known to those skilled in the art, for example, at least one selected from the following: ultraviolet absorber, wavelength dispersion regulator, polymerization inhibitor, antioxidant, heat stabilizer, and plasticizer, but not limited thereto.

[0157] The second retardation layer 120 may be composed of a single layer or multiple layers.

[0158] The laminate of the first retardation layer 110 and the second retardation layer 120 may have an in-plane retardation of 100 nm to 180 nm (for example, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, or 180 nm), particularly 120 nm to 160 nm, at a wavelength of 550 nm. Within this range, the laminate can further effectively achieve the advantageous effects of the present invention.

[0159] The laminate of the first retardation layer 110 and the second retardation layer 120 may have an out-of-plane retardation of 50 nm to 120 nm, particularly 50 nm to 110 nm, at a wavelength of 550 nm. Within this range, the laminate can further effectively achieve the advantageous effects of the present invention.

[0160] The laminate of the first retardation layer 110 and the second retardation layer 120 may have a biaxiality of -0.2 to 1.4, particularly -0.1 to 1.3, at a wavelength of 550 nm. Within this range, the laminate can further effectively achieve the advantageous effects of the present invention.

[0161] Although not shown in Figure 1 , a primer layer may be formed on at least one surface of the second retardation layer 120. The primer layer is the same as the above.

[0162] The second retardation layer 120 may be directly formed on the third retardation layer 130 without an adhesive layer or a bonding layer, or may be formed on the third retardation layer 130 via an adhesive layer (for example, a PSA (pressure-sensitive adhesive) layer) or a bonding layer. Herein, the expression "directly formed on" means that there is no adhesive layer or bonding layer between the second retardation layer and the third retardation layer.

[0163] The third retardation layer

[0164] The third retardation layer 130 has an in-plane retardation and / or an out-of-plane retardation different from those of the first retardation layer 110 and the second retardation layer 120 at a wavelength of 550 nm.

[0165] The third retardation layer 130 is formed on the lower surface of the second retardation layer 120, thereby significantly reducing the reflectance at the side surface of the polarizing plate and simultaneously improving the ellipticity. It has been confirmed that inFigure 1 In the structure of the polarizing plate shown, the lack of the third retardation layer results in deterioration of both the reflectance and the ellipticity.

[0166] The third retardation layer 130 may have an out-of-plane retardation of -100 nm to -10 nm (e.g., -100 nm, -90 nm, -80 nm, -70 nm, -60 nm, -50 nm, -40 nm, -30 nm, -20 nm, or -10 nm) at a wavelength of 550 nm. Within this range, the third retardation layer 130 can improve the reflectance and the ellipticity at the side surface together with the first retardation layer and the second retardation layer. Preferably, the third retardation layer 130 has an out-of-plane retardation of -90 nm to -30 nm, more preferably -80 nm to -40 nm, at a wavelength of 550 nm.

[0167] As a positive C-plate (+C plate), the third retardation layer 130 may satisfy the relation 6:

[0168] nz > nx ≒ ny, --- (6)

[0169] wherein, nx represents the refractive index of the third retardation layer in its slow axis direction, ny represents the refractive index of the third retardation layer in its fast axis direction, and nz represents the refractive index of the third retardation layer in its thickness direction. These refractive indices are measured at a wavelength of 550 nm.

[0170] When the +C plate is used as the third retardation layer, the polarizing plate can exhibit a further improved antireflection effect at its side surface.

[0171] The third retardation layer 130 may have an in-plane retardation of 10 nm or less than 10 nm, e.g., 0 nm to 10 nm, at a wavelength of 550 nm.

[0172] The third retardation layer 130 may exhibit positive wavelength dispersion, negative wavelength dispersion, or flat wavelength dispersion.

[0173] The third retardation layer 130 may be a film or a coating. Preferably, the third retardation layer is a coating, so as to be able to reduce the thickness of the polarizing plate. The third retardation layer 130 may have a thickness of 30 μm or less than 30 μm, e.g., a thickness greater than 0 μm to 10 μm. Within this range, the third retardation layer 130 can be used in the polarizing plate and can reduce the thickness of the polarizing plate.

[0174] When the third retardation layer 130 is a film, the third retardation layer 130 can be formed by stretching an optically transparent unstretched resin film so that the resin film exhibits the above-described properties including the in-plane retardation. Here, the stretching may include uniaxial stretching, biaxial stretching, or oblique stretching.

[0175] When the third retardation layer 130 is a coating, the third retardation layer 130 can be an amorphous layer. When the third retardation layer 130 is formed of liquid crystal, an alignment layer needs to be formed to align the liquid crystal at a specific angle, and foreign substances will be generated.

[0176] The coating can be formed of any material as long as the coating can achieve out-of-plane retardation and a positive C-plate. For example, the coating can include at least one selected from the group consisting of substituted or unsubstituted styrene resins, substituted or unsubstituted (meth)acrylonitrile resins, substituted or unsubstituted (meth)acrylic alkyl esters including (meth)acrylic acid methyl ester, and cellulose resins, preferably substituted or unsubstituted cellulose resins, for example, cellulose ester resins. Cellulose ester resins allow for easy implementation of the third retardation layer.

[0177] In one embodiment, the first retardation layer, the second retardation layer, and the third retardation layer can be integrally formed with each other. Herein, "integrally" means a three-layer laminate in which the first retardation layer and the third retardation layer are stacked on the second retardation layer without an adhesive layer or a bonding layer therebetween.

[0178] Hereinafter, the manufacture of the three-layer laminate will be described.

[0179] A laminate of the first retardation layer and the second retardation layer can be manufactured by coating a first retardation layer composition on the upper surface of an unstretched or partially stretched film for the second retardation layer with a predetermined thickness, and then simultaneously stretching the unstretched or partially stretched film and the coating for the first retardation layer. Here, the stretching can be MD uniaxial stretching or diagonal stretching, but is not limited thereto. Thereafter, a three-layer laminate can be manufactured by coating a third retardation layer composition on the lower surface of the second retardation layer, and then drying and / or curing.

[0180] Polarizer

[0181] The polarizer 140 is used to convert natural light or polarized light into polarized light. The polarizer 140 has an absorption axis and a transmission axis orthogonal to the absorption axis. The absorption axis and the transmission axis are respectively arranged in one direction.

[0182] The polarizer can be made of a polymer film mainly composed of a polyvinyl alcohol resin. Specifically, the polarizer can be manufactured by dyeing the polymer film with iodine or a dichroic dye, and then stretching the dyed film in the machine direction (MD). Specifically, the polarizer can be manufactured by a swelling, dyeing, stretching, and crosslinking process.

[0183] The polarizer 140 may have a total light transmittance of 42% or greater than 42%, for example, 42% to 50%, and a degree of polarization of 99% or greater than 99%, for example, 99% to 100%. Within these ranges, by combining with the first retardation layer, the second retardation layer, and the third retardation layer, the polarizer can improve the antireflection performance of the polarizing plate.

[0184] The polarizer 140 may have a thickness of 0.1 μm to 30 μm, particularly 1 μm to about 25 μm. Within this range, the polarizer can be used in a polarizing plate.

[0185] Although not shown in Figure 1 a protective film may be formed on the upper surface of the polarizer 140.

[0186] The protective film formed on the upper surface of the polarizer is used to protect the polarizer from the external environment while improving the mechanical strength of the polarizing plate. The protective film may be an optically transparent film formed of at least one resin selected from, for example, the following: cellulose resins including triacetyl cellulose (TAC), etc., polyester resins including polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, and 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. Specifically, the protective film may be a TAC film or a PET film.

[0187] The protective film may have a thickness of about 5 μm to about 70 μm, particularly about 15 μm to about 45 μm. Within this range, the protective film can be used in a polarizing plate.

[0188] 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 coat, an anti-fingerprint layer, and an antireflection layer. These functional coatings may be stacked individually or in combination. The protective film may be attached to the polarizer via an adhesive layer. The adhesive layer may be formed of an aqueous or UV-curable adhesive, but is not limited thereto.

[0189] Next, a polarizing plate according to another embodiment of the present invention will be described with reference to Figure 3

[0190] Refer to Figure 3 , except that the polarizer 140, the second retardation layer 120, the first retardation layer 110, and the third retardation layer 130 are stacked in this order sequentially, the polarizing plate according to this embodiment is substantially the same as the polarizing plate shown in Figure 1 . The details of the polarizer, the first retardation layer, the second retardation layer, and the third retardation layer described with reference to Figure 1 can also be applied to the polarizing plate according to this embodiment.​

[0191] Next, an optical display device according to the present invention will be described.

[0192] The optical display device according to the present invention may include a polarizing plate according to an embodiment of the present invention. For example, the optical display device may include a light-emitting display device including an organic liquid crystal display, a liquid crystal display device, and the like. In one embodiment, in the polarizing plate, the first retardation layer may be disposed closer to the panel of the display device than the polarizer.

[0193] 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 illustrative purposes only and should not be construed as limiting the present invention in any way.

[0194] Example 1

[0195] In an iodine aqueous solution at 55 °C, a polyvinyl alcohol film (PS#60, pre-stretched thickness: 60 μm, Kuraray Co., Ltd.) was stretched to 6 times its initial length to prepare a 12-μm-thick polarizer with a transmittance of 45%.

[0196] As the resin for the second retardation layer, a cyclic olefin polymer film (COP) [JSR] was extruded and stretched. A (cellulose-containing) composition for the first retardation layer was coated on the upper surface of the stretched film to a predetermined thickness, dried, and stretched together with the stretched film for the second retardation layer to prepare a laminate of the first retardation layer and the second retardation layer. Here, the angle between the slow axis of the first retardation layer and the slow axis of the second retardation layer and the characteristics of the first retardation layer and the second retardation layer can be adjusted by adjusting the stretching ratio and the stretching direction.

[0197] The third retardation layer was formed by coating a (cellulose-containing) third retardation layer composition [Eastman Co., Ltd.] on the lower surface of the second retardation layer, and then drying the composition to manufacture a laminate of the first retardation layer, the second retardation layer, and the third retardation layer.

[0198] Then, a polarizing plate was manufactured by stacking the first retardation layer, the second retardation layer, and the third retardation layer in this order on the lower surface of the polarizer.

[0199] The detailed specifications of the manufactured polarizing plate are shown in Table 1.

[0200] Examples 2 to 5

[0201] Each polarizing plate was manufactured in the same manner as in Example 1, except that the properties and angles of the first retardation layer, the second retardation layer, and the third retardation layer were changed.

[0202] Comparative Example 1

[0203] A polarizing plate was fabricated in the same manner as in Example 1, except that a negative wavelength dispersion film (+A plate, slow axis inclined +45° with respect to the absorption axis of the polarizer, in-plane retardation at a wavelength of 550 nm: 135 nm) and a positive C plate (out-of-plane retardation at a wavelength of 550 nm: -50 nm) were stacked in sequence on the lower surface of the polarizer.

[0204] Comparative Examples 2 to 11

[0205] Each polarizing plate was fabricated in the same manner as in Example 1, except that the properties and angles of the first retardation layer, the second retardation layer, and the third retardation layer were changed.

[0206] The reflectance and ellipticity at the side surface (@60°) of the polarizing plates fabricated in the examples and comparative examples were evaluated, and the results are shown in Tables 1 to 3.

[0207] To evaluate the reflectance and ellipticity at the side surface, the reflectance was evaluated by comparing the average azimuth angle at a 60° angle using DMS, and the ellipticity was evaluated by comparing the minimum value at the azimuth angle using AXOSCAN.

[0208] Lower reflectance and higher ellipticity indicate better screen quality of a display device including the corresponding polarizing plate. The required reflectance is 1.3% or less than 1.3%, and the ellipticity is 75% or more than 75%.

[0209] Table 1

[0210]

[0211] Table 2

[0212]

[0213] Table 3

[0214]

[0215] In Tables 1, 2, and 3,

[0216] The angle α is the angle (unit: °) of the slow axis of the first retardation layer with respect to the absorption axis (0°) of the polarizer

[0217] The angle β is the angle (unit: °) defined between the slow axis of the first retardation layer and the slow axis of the second retardation layer

[0218] As shown in Table 1, the polarizing plate according to the present invention has a very low reflectance and a very high ellipticity.

[0219] On the contrary, compared with the polarizing plate of the example, the reflectance and ellipticity of the polarizing plate of Comparative Example 1 that does not use the polarizing plate structure according to the present invention are poor. In addition, although not shown in Table 1, this polarizing plate has problems such as difficulty in attaching the first retardation layer and the third retardation layer to the polarizer by roll-to-roll processing, and insufficient mechanical strength of the retardation layer as the lower protective film of the polarizer.

[0220] In addition, the polarizing plates of Comparative Examples 2 to 11 do not satisfy the following conditions: the angle α, the angle β, the wavelength dispersion and in-plane retardation of the first retardation layer, and the wavelength dispersion and in-plane retardation of the second retardation layer, and compared with the polarizing plate of the example, the polarizing plates of Comparative Examples 2 to 11 have far poorer reflectance and ellipticity.

[0221] Although some embodiments have been described herein, it should be understood that those skilled in the art can make various modifications, variations, changes, and equivalent embodiments without departing from the spirit and scope of the present invention.

Claims

1. A polarizing plate, comprising: A polarizer; And A laminate of a first retardation layer and a second retardation layer and a third retardation layer stacked in sequence on the lower surface of the polarizer, Wherein the first retardation layer has a slow axis inclined at an angle of +40° to +50° or -50° to -40° with respect to the absorption axis or the transmission axis of the polarizer, The slow axis of the first retardation layer is inclined at an angle of +80° to +100° or -100° to -80° with respect to the slow axis of the second retardation layer, The first retardation layer exhibits positive wavelength dispersion and has an in-plane retardation of 50 nm to 100 nm at a wavelength of 550 nm, and The second retardation layer exhibits positive wavelength dispersion or flat wavelength dispersion and has an in-plane retardation of 180 nm to 240 nm at a wavelength of 550 nm, The laminate of the first retardation layer and the second retardation layer has an out-of-plane retardation of 50 nm to 120 nm at a wavelength of 550 nm, Wherein the second retardation layer has a biaxiality of 1.0 to 1.4 at a wavelength of 550 nm.

2. The polarizing plate according to claim 1, wherein the first retardation layer, the second retardation layer, and the third retardation layer are stacked in sequence on the polarizer in that order.

3. The polarizing plate according to claim 1, wherein the second retardation layer, the first retardation layer, and the third retardation layer are stacked in sequence on the polarizer in that order.

4. The polarizing plate according to claim 1, wherein the third retardation layer is a positive C plate and has an out-of-plane retardation of -100 nm to -10 nm at a wavelength of 550 nm.

5. The polarizing plate according to claim 1, wherein the first retardation layer is a negative A plate.

6. The polarizing plate according to claim 1, wherein the second retardation layer is a positive A plate or a negative B plate.

7. The polarizing plate according to claim 1, wherein the first retardation layer satisfies relation 1: Re(450) / Re(550) ≥ 1.1, ---- (1) Wherein Re(450) and Re(550) are the in-plane retardations of the first retardation layer at a wavelength of 450 nm and at a wavelength of 550 nm, respectively.

8. The polarizing plate according to claim 1, wherein the first retardation layer has a biaxiality of -0.5 to 0 at a wavelength of 550 nm.

9. The polarizing plate according to claim 1, wherein the second retardation layer satisfies relation 3: 0.95 ≤ Re(450) / Re(550) ≤ 1.03, ---- (3) Wherein Re(450) and Re(550) are the in-plane retardations of the second retardation layer at a wavelength of 450 nm and at a wavelength of 550 nm, respectively.

10. The polarizing plate according to claim 1, wherein the slow axis of the second retardation layer is inclined at an angle of +40° to +50°, at an angle of -50° to -40°, at an angle of +130° to +140°, or at an angle of -140° to -130° with respect to the absorption axis or the transmission axis of the polarizer.

11. The polarizing plate according to claim 1, wherein assuming that the absorption axis of the polarizer is set at an angle of 0°, the slow axis of the first retardation layer is inclined at an angle of +40° to +50° and the angle defined between the slow axis of the first retardation layer and the slow axis of the second retardation layer can be in the range of +80° to +100°.

12. The polarizing plate according to claim 1, wherein the laminate of the first retardation layer and the second retardation layer has an in-plane retardation of 100 nm to 180 nm at a wavelength of 550 nm.

13. The polarizing plate according to claim 1, wherein the laminate of the first retardation layer and the second retardation layer has a biaxiality of -0.2 to 1.4 at a wavelength of 550 nm.

14. The polarizing plate according to claim 1, wherein each of the first retardation layer and the third retardation layer is an amorphous layer.

15. The polarizing plate according to claim 1, wherein each of the first retardation layer and the third retardation layer includes a coating formed of a composition including at least one selected from the group consisting of a substituted or unsubstituted styrene resin, a substituted or unsubstituted (meth)acrylonitrile resin, a substituted or unsubstituted (meth)acrylic alkyl ester resin including (meth)acrylic acid methyl ester, and a cellulose resin.

16. The polarizing plate according to claim 15, wherein the composition further includes an additive containing an aromatic group.

17. The polarizing plate according to claim 1, wherein the second retardation layer includes an MD uniaxially stretched film or an obliquely stretched film.

18. The polarizing plate according to claim 1, wherein each of the first retardation layer, the second retardation layer, and the third retardation layer includes a primer layer on at least one of its surfaces.

19. An optical display device, including the polarizing plate according to any one of claims 1 to 18.

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