Polarizing plate and optical display device

Abstract

Provided are a polarizing plate and an optical display device comprising same, the polarizing plate comprising: a polarizer; and a retardation layer stacked on one surface of the polarizer and including a negative B layer and a positive B layer, wherein the negative B layer is disposed between the polarizer and the positive B layer, the negative B layer has an in-plane retardation of 30-130 nm and a degree of biaxiality of 2.5-4.5 at a wavelength of 550 nm, the positive B layer has an in-plane retardation of 100-190 nm and a degree of biaxiality of -1.5 to -0.5 at a wavelength of 550 nm, and, with respect to a light absorption axis of the polarizer, a slow axis of the negative B layer forms an angle of -1° to 1° and a slow axis of the positive B layer forms an angle of 89° to 91°.

Description

Polarizing plates and optical display devices

[0001] It relates to polarizing plates and optical display devices.

[0002]

[0003] Liquid crystal displays (LCDs) include a liquid crystal panel and polarizing plates positioned on both sides of the panel. Among LCDs, in-plane switching mode is used as a liquid crystal driving mode to widen the viewing angle. Recently, with the manufacture of large-screen TVs and automotive display devices utilizing in-plane switching mode, a wider viewing angle is becoming increasingly necessary. Therefore, the development of polarizing plates capable of achieving this is essential. Polarizing plates should not only ensure a wide viewing angle, but also be produced using roll-to-roll processes, ensuring both cost-effectiveness and processability.

[0004] The background technology of the present invention is disclosed in Korean Patent Publication No. 10-2013-0103595, etc.

[0005]

[0006] An object of the present invention is to provide a polarizing plate that provides a visibility improvement effect including a side viewing angle and color improvement effect.

[0007] Another object of the present invention is to provide a polarizing plate that provides a light leakage improvement effect.

[0008] Another object of the present invention is to provide a polarizing plate that is excellent in economy and fairness by being able to be wound and produced in a roll-to-roll manner.

[0009] Another object of the present invention is to provide a polarizing plate capable of reducing thickness.

[0010]

[0011] According to one embodiment, a polarizing plate is provided.

[0012] 1. The polarizing plate comprises a polarizer; and a phase difference layer laminated on one surface of the polarizer and including a negative B layer and a positive B layer, wherein the negative B layer is positioned between the polarizer and the positive B layer, the negative B layer has an in-plane phase difference of 30 to 130 nm and a degree of biaxiality of 2.5 to 4.5 at a wavelength of 550 nm, the positive B layer has an in-plane phase difference of 100 to 190 nm and a degree of biaxiality of -1.5 to -0.5 at a wavelength of 550 nm, and the slow axis of the negative B layer forms -1 to 1° with respect to a light absorption axis of the polarizer, and the slow axis of the positive B layer forms 89 to 91°.

[0013] In paragraph 2.1, the negative B layer may have a thickness direction phase difference of 60 to 325 nm at a wavelength of 550 nm.

[0014] In 3.1-2, the negative B layer may be manufactured by a solvent casting method.

[0015] In 4.1-3, the negative B layer may include fine particles.

[0016] In 5.1-4, the fine particles may include silicon dioxide.

[0017] In 6.1-5, the negative B layer and the positive B layer may have the same stretching direction.

[0018] In 7.1-6, the stretching direction may be the direction of the light absorption axis of the polarizer.

[0019] In 8.1-7, the negative B layer may include a polymer having positive birefringence, and the positive B layer may include a polymer having negative birefringence.

[0020] In 9.1-8, the negative B layer may include at least one of a cyclic olefin copolymer and a cellulose ester copolymer.

[0021] In 10.1-9, the positive B layer may include at least one of a cellulose compound or a polymer thereof, an aromatic compound or a polymer thereof.

[0022] In 11.1-10, the laminate of the positive B layer and the negative B layer may have an in-plane phase difference of 20 to 110 nm at a wavelength of 550 nm.

[0023] In 12.1-11, the laminate of the positive B layer and the negative B layer may have a thickness direction phase difference of -10 to 95 nm at a wavelength of 550 nm.

[0024] In 13.1-12, the positive B layer may have a thickness direction phase difference of -255 to -70 nm at a wavelength of 550 nm.

[0025] In 14.1-13, the positive B layer and the negative B layer satisfy Equation 1 below, and the value of Equation 2 below can be 1.1 to 3.7:

[0026] [Formula 1]

[0027] Re(-B) < Re(+B)

[0028] [Formula 2]

[0029] Re(+B) / Re(-B)

[0030] (In the above equations 1 and 2, Re(-B) and Re(+B) are the in-plane phase differences of the negative B layer and the positive B layer, respectively, at a wavelength of 550 nm.)

[0031] In 15.1-14, the thickness of the laminate of the positive B layer and the negative B layer may be 95% or more of the thickness of the phase difference layer.

[0032] In 16.1-15, the phase difference layer can be laminated on the light incident surface or light exit surface of the polarizer.

[0033] In 17.1-16, a protective layer may be further laminated on one side or the other side of the polarizer.

[0034] According to another embodiment, an optical display device is provided.

[0035] The above optical display device includes the above polarizing plate.

[0036]

[0037] The present invention provides a polarizing plate that provides a visibility improvement effect including a side viewing angle and color improvement effect.

[0038] The present invention provides a polarizing plate that provides a light leakage improvement effect.

[0039] The present invention provides a polarizing plate that is capable of being wound and produced in a roll-to-roll manner, thereby providing excellent economic efficiency and fairness.

[0040] The present invention provides a polarizing plate capable of being thinned.

[0041]

[0042] Figure 1 is a cross-sectional view of a polarizing plate of one embodiment.

[0043] Figure 2 is a cross-sectional view of a polarizing plate of another embodiment.

[0044] Figure 3 is a cross-sectional view of a liquid crystal display device of one embodiment.

[0045] Figure 4 is a cross-sectional view of a liquid crystal display device of another embodiment.

[0046] Figures 5 to 17 show the results of visibility evaluations of examples and comparative examples, respectively.

[0047]

[0048] The present invention is described in detail, with reference to the attached drawings, by way of examples, so that those skilled in the art can easily practice the invention. The present invention may be implemented in various different forms and is not limited to the examples described herein.

[0049] In order to clearly explain the present invention in the drawings, parts irrelevant to the description have been omitted, and the same designations have been used for identical or similar components throughout the specification. The length and size of each component in the drawings are for the purpose of explaining the present invention, and the present invention is not limited to the length and size of each component described in the drawings.

[0050] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0051] In this specification, “upper” and “lower” are defined based on the drawing, and “upper” may be changed to “lower” and “lower” may be changed to “upper” depending on the viewing angle.

[0052] In this specification, the “in-plane phase difference (Re)” is expressed by the following formula A, the “thickness direction phase difference (Rth)” is expressed by the following formula B, and the “degree of biaxiality (NZ)” is expressed by the following formula C:

[0053] [Formula A]

[0054] Re = (nx - ny) xd

[0055] [Formula B]

[0056] Rth = ((nx + ny) / 2 - nz) xd

[0057] [Formula C]

[0058] NZ = (nx - nz) / (nx - ny)

[0059] (In the above formulas A to C, nx, ny, and nz are the refractive indices in the slow axis direction, the fast axis direction, and the thickness direction of the phase difference layer, respectively, at the measurement wavelength, and d is the thickness of the phase difference layer (unit: nm).)

[0060] Unless otherwise specified herein, nx, ny, and nz represent the refractive indices in the slow axis direction, the fast axis direction, and the thickness direction at a wavelength of 550 nm. In this specification, the axis with the highest refractive index in the in-plane direction is defined as the 'slow axis', and the axis with the lowest refractive index in the in-plane direction is defined as the 'fast axis'. The 'slow axis' and the 'fast axis' may be substantially orthogonal, but are not limited thereto.

[0061] According to one embodiment, a polarizing plate is provided that provides side viewing angle and color improvement effects. As a result, the polarizing plate can provide excellent black visibility.

[0062] According to one embodiment, a polarizing plate is provided that provides a light leakage improvement effect by lowering the maximum light transmittance in all directions. For example, the maximum light transmittance in all directions may be 1.0% or less, for example, 0 to 1.0%, 0 to 0.5%, or 0 to 0.3%, and the light leakage improvement effect may be excellent within the above range.

[0063] The above "light transmittance" refers to the amount of light leaking depending on the visual angle, assuming 100% backlight light when the display displays black. It is a value that reflects the eye's tristimulus values. The lower the "light transmittance," the better the viewing angle characteristics.

[0064] According to one implementation example, a polarizing plate with excellent economic efficiency and excellent thickness reduction is provided because it can be wound and produced in a roll-to-roll manner.

[0065] According to one embodiment, a polarizing plate includes a polarizer; and a retardation layer laminated on one surface of the polarizer and including a negative B layer and a positive B layer, wherein the negative B layer is positioned between the polarizer and the positive B layer, wherein the negative B layer has an in-plane retardation of 30 to 130 nm and a degree of biaxiality of 2.5 to 4.5 at a wavelength of 550 nm, and the positive B layer has an in-plane retardation of 100 to 190 nm and a degree of biaxiality of -1.5 to -0.5 at a wavelength of 550 nm, and the slow axis of the negative B layer forms -1 to 1° and the slow axis of the positive B layer forms 89 to 91° with respect to a light absorption axis of the polarizer.

[0066] According to one embodiment, the laminate of the positive B layer and the negative B layer can have an in-plane phase difference of 20 to 110 nm and a thickness direction phase difference of -10 to 95 nm at a wavelength of 550 nm. In the above range, the above-described effect can be remarkably excellent.

[0067] According to one implementation example, the polarizing plate can be a viewer-side polarizing plate or a light source-side polarizing plate.

[0068] In one specific example, when no voltage is applied to the IPS panel, the alignment direction of the driving liquid crystals in the IPS panel, i.e., the rubbing direction, is 90°, the absorption axis of the polarizer among the viewer-side polarizing plates is 0°, and the absorption axis of the polarizer among the light source-side polarizing plates is 90°, the laminate or phase difference layer of the positive B layer and the negative B layer may be positioned on the viewer-side polarizing plate side. Accordingly, the viewer-side polarizer, the negative B layer, the positive B layer, the IPS panel, and the light source-side polarizer are laminated in this order from the viewer side. A person of ordinary skill in the art will refer to this as an O-mode structure.

[0069] In another specific example, when no voltage is applied to the IPS panel, the alignment direction of the driving liquid crystals in the IPS panel, i.e., the rubbing direction, is 0°, the absorption axis of the polarizer among the viewer-side polarizing plates is 0°, and the absorption axis of the polarizer among the light source-side polarizing plates is 90°, the laminate or phase difference layer of the positive B layer and the negative B layer is positioned on the light source-side polarizing plate side, and is laminated in the order of the light source-side polarizer, the negative B layer, the positive B layer, the IPS panel, and the viewer-side polarizer from the light source. A person of ordinary skill in the art refers to this as an E-mode structure.

[0070] However, in the above specific example, the laminate or phase difference layer of the positive B layer and the negative B layer cannot be positioned simultaneously on the polarizing plate on the viewer side and the polarizing plate on the light source side.

[0071] Hereinafter, each component of the polarizing plate of the present invention will be described in detail.

[0072] Negative B layer

[0073] The negative B layer is a phase contrast layer that satisfies the refractive index relationship of nx > ny > nz (nx, ny, and nz are the refractive indices in the slow axis direction, the fast axis direction, and the thickness direction of the negative B layer at a wavelength of 550 nm, respectively).

[0074] The negative B layer is located between the polarizer and the positive B layer in the polarizing plate. The negative B layer can be easily improved in terms of side viewing angle and color by being laminated at the above position. A polarizing plate in which the negative B layer and the positive B layer, each having the above-described in-plane retardation and biaxiality degree, are laminated in the order of the positive B layer and the negative B layer from the polarizer may not properly achieve the side viewing angle and color improvement effect and the light leakage improvement effect of the present invention, or the above-described effects may be weak.

[0075] The negative B layer has a ground axis and a forward axis in the in-plane direction.

[0076] The slow axis of the negative B layer forms an angle of -1 to 1° with respect to the light absorption axis of the polarizer, when the light absorption axis of the polarizer is 0°. In this range, it is easy to provide a viewing angle and color improvement effect from the side and a light leakage improvement effect. For example, when the light absorption axis of the polarizer is 0°, the slow axis of the negative B layer can form 0°.

[0077] The negative B layer has an in-plane phase difference of 30 to 130 nm and a biaxiality of 2.5 to 4.5 at a wavelength of 550 nm. In the above range, it is easy to improve the viewing angle and light leakage from the side when laminating the positive B layer as described below.

[0078] The in-plane phase difference and degree of biaxiality of the above-mentioned negative B layer and the in-plane phase difference and degree of biaxiality of the positive B layer were set in a range such that when a laminate of the negative B layer and the positive B layer was manufactured by the method described below, the effects of improving the viewing angle and color from the side and improving light leakage were achieved.

[0079] For example, the negative B layer may have an in-plane phase difference of 40 to 100 nm, or 40 to 60 nm at a wavelength of 550 nm. For example, the negative B layer may have a biaxiality of 2.5 to 4.0, or 3.0 to 4.0 at a wavelength of 550 nm.

[0080] The negative B layer may have a thickness-wise retardation of 60 to 325 nm at a wavelength of 550 nm. Within this range, it may be easy to improve the viewing angle and light leakage from the side when laminating the positive B layer described below. For example, the negative B layer may have a thickness-wise retardation of 120 to 300 nm or 120 to 150 nm at a wavelength of 550 nm. Within this range, the visibility and light leakage improvement effects may be further enhanced.

[0081] The negative B layer can be formed of a material that satisfies the above-described refractive index relationship and can implement the above-described in-plane phase difference and degree of biaxiality.

[0082] The negative B layer may be made of any material as long as it satisfies the above-described refractive index relationship, in-plane phase difference, and degree of biaxiality.

[0083] In one embodiment, the negative B layer can be a liquid crystal layer or a non-liquid crystal layer. Preferably, the negative B layer can be a non-liquid crystal layer.

[0084] However, the present invention specifically uses a negative B layer manufactured by treating a composition for a negative B layer by a solvent casting method to manufacture an unstretched film, and then uniaxially stretching the manufactured unstretched film in the MD of the unstretched film.

[0085] Generally, film manufacturing methods can be categorized into two types: melt extrusion and solvent casting. Melt extrusion involves heating a polymer to a molten state and then extruding it through an extrusion device to produce an unstretched film. Therefore, it can offer high productivity with relatively low equipment costs. However, melt extrusion can sometimes lead to the formation of thin lines (so-called die lines) on the film because the film thickness cannot be precisely controlled. Therefore, melt extrusion may not be suitable for high-quality films, such as optically functional films.

[0086] On the other hand, the solvent casting method offers the advantages of providing better optical isotropy and thickness uniformity than the melt extrusion method, and producing films with fewer foreign substances. Therefore, the solvent casting method can be advantageous for producing optically functional films.

[0087] The solvent casting method prepares a dope material by dissolving a polymer in a mixed solvent (e.g., a solvent composed of dichloromethane or methyl acetate), and mixes a predetermined additive into the dope material to prepare a casting dope. The casting dope is supplied to a casting die and discharged from a discharge slit onto a casting drum, an endless band, or a continuously moving support. The discharged dope forms beads between the discharge slit and the support to form a casting film on the support. This casting film is returned to the support at a constant speed and cooled or dried to become self-supporting. This casting film is peeled from the support to form a wet film, then dried and wound into a film product.

[0088] The dope material may include the above-described polymer. The polymer is not particularly limited as long as it can implement a negative B layer when manufactured into an unstretched film and then uniaxially stretched along the MD axis. For example, the polymer may be a cellulose ester copolymer including a cyclic olefin copolymer (COC), cellulose acylate, cellulose butyrate, cellulose propionate, cellulose acetate propionate, cellulose acetate butyrate, etc.

[0089] Preferably, among the polymers, the cyclic olefin copolymer (COC) can produce a relatively thin unstretched film by a solvent casting method, and can easily implement the above-described in-plane phase difference and degree of biaxiality when producing a laminate of a negative B layer and a positive B layer described below.

[0090] In one specific embodiment, the polymer may exhibit positive birefringence. Here, "positive birefringence" means a material whose refractive index increases in the stretching direction. In other words, the stretching direction and the slow axis are coincident. Positive birefringence enables the production of a negative B layer by MD uniaxial stretching, thereby satisfying the relationship between the light absorption axis of the polarizer and the slow axis of the negative B layer, and enables roll-to-roll winding and production of the polarizing plate, thereby improving economy and processability.

[0091] Cyclic olefin copolymers are polymers having a cyclic olefin structure. Cyclic olefin copolymers are norbornene polymers, monocyclic olefin polymers, cyclic conjugated diene polymers, vinyl alicyclic hydrocarbon polymers, or hydrides of each of these.

[0092] The dope may contain a solvent. The solvent is not particularly limited, but may include a solvent capable of dissolving the polymer (also called a good solvent). Preferred solvents include chlorine compounds such as dichloromethane or chloroform, chain hydrocarbons, cyclic hydrocarbons, aromatic hydrocarbons, and esters, ketones, and / or ether compounds of all of these having 3 to 12 carbon atoms. The esters, ketones, and ethers may have a cyclic structure. Chain hydrocarbons having 3 to 12 carbon atoms may be hexane, octane, isooctane, and decane. Cyclic hydrocarbons having 3 to 12 carbon atoms may be cyclopentane, cyclohexane, and derivatives thereof. Aromatic hydrocarbons having 3 to 12 carbon atoms may be benzene, toluene, and xylene. Esters having 3 to 12 carbon atoms may be ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate, and pentyl acetate. Ketones having 3 to 12 carbon atoms may be acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, and methyl cyclohexanone. Ethers having 3 to 12 carbon atoms may be diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole, and phenetole. Organic solvents having two or more functional groups may include 2-ethoxyethyl acetate, 2-methoxyethanol, and 2-butoxyethanol. The boiling point of the organic solvent may preferably be 35 to 150 degrees.

[0093] Additionally, the solvent may be a mixture of two or more compounds to control the drying properties, viscosity, and other properties of the dope. In this case, the solvent may additionally contain an antisolvent.

[0094] The antisolvent can be selected depending on the polymer used. For example, if the good solvent is a chlorinated organic solvent, an alcohol can be used as the antisolvent. The alcohol can have any of a straight-chain, branched, or cyclic structure, with a saturated alicyclic hydrocarbon being preferred. Furthermore, the alcohol can be primary, secondary, or tertiary. Examples of such alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, 1-pentanol, 1-methyl-2-butanol, and cyclohexanol. The alcohol may also be a fluorinated alcohol, such as 2-fluoroethanol, 2,2,2-trifluoroethanol, or 2,2,3,3-tetrafluoro-1-propanol. Monohydroxyalcohols are highly preferred as antisolvents because they reduce peeling resistance. Depending on the solvent used, suitable alcohols have a boiling point of 120°C or lower from the standpoint of drying properties, more preferably monohydroxy alcohols having 1 to 6 carbon atoms, and even more preferably alcohols having 1 to 4 carbon atoms. A preferred mixed solvent for dope of a cyclic olefin copolymer is one in which the main component is dichloromethane, and the antisolvent is preferably at least one of methanol, ethanol, propanol, isopropanol, and butanol.

[0095] In the solvent casting method, it is possible to mix additives into the dope material prior to discharging. The additives may include one or more of a deterioration inhibitor, a UV absorber, a retardation control agent, a plasticizer, and fine particles. Preferably, the additives include fine particles.

[0096] Fine particles are added to reduce the coefficient of kinetic friction on the surface of the film product, thereby reducing the stress on the film during handling. Consequently, the fine particles can prevent the entire positive B layer and the entire negative B layer from breaking when the entire layer is rolled and unrolled. In particular, the fine particles eliminate the need for additional protective films to be laminated to the entire positive B layer and the entire negative B layer before roll-to-roll winding, thereby improving the manufacturing process of polarizing plates and making them more economical to produce.

[0097] The particulate matter is not limited, but may be a particle of either an inorganic compound or an organic compound.

[0098] The inorganic compound may be a silicon compound such as silicon dioxide (silica), titanium oxide, zinc oxide, aluminum oxide, barium oxide, zirconium oxide, strontium oxide, antimony oxide, tin oxide, tin / antimony oxide, calcium carbonate, talc, clay, sintered kaolin, sintered calcium silicate, hydrated calcium silicate, aluminum silicate, magnesium silicate, or calcium phosphate. Silicon-containing inorganic compounds and silicon-containing metal oxides are more preferred. Silicon dioxide is particularly preferred from the viewpoint of the haze removal effect of the film.

[0099] Organic compounds can be polytetrafluoroethylene, cellulose acetate, polystyrene, polymethyl methacrylate, polypropyl methacrylate, polymethyl methacrylate, polyethylene carbonate, and starch.

[0100] The primary average diameter of the fine particles may be 1 to 200,000 nm, preferably 1 to 10,000 nm, and more preferably 2 to 1,000 nm. Within this range, haze reduction of the film can be minimized. The above "primary average diameter" can be calculated from the average size of the particles measured using a transmission electron microscope.

[0101] The fine particles may be contained in the negative B layer in an amount of 0.01 to 0.3 parts by weight per 100 parts by weight of the polymer constituting the negative B layer.

[0102] The negative B layer may have a thickness of 20 to 80 μm, for example, 25 to 75 μm, or 30 to 60 μm. In the above range, it can be used in a polarizing plate.

[0103] Positive B layer

[0104] The positive B layer is positioned opposite the polarizer with respect to the negative B layer of the polarizing plate. By laminating the positive B layer at the above position, it can be easily improved in terms of viewing angle and color from the side.

[0105] The positive B layer has a ground axis and a true axis in the in-plane direction.

[0106] The ground axis of the positive B layer forms an angle of 89° to 91° with respect to the light absorption axis of the polarizer, when the light absorption axis of the polarizer is set to 0°. Within this range, it is easy to provide a viewing angle and color improvement effect from the side and a light leakage improvement effect. For example, when the light absorption axis of the polarizer is set to 0°, the ground axis of the positive B layer can form an angle of 90°.

[0107] The positive B layer has an in-plane phase difference of 100 to 190 nm at a wavelength of 550 nm and a biaxiality of -1.5 to -0.5. In this range, it is easy to improve the viewing angle and light leakage from the side when laminating the negative B layer described above.

[0108] For example, the positive B layer may have an in-plane phase difference of 100 to 170 nm, 100 to 150 nm, or 110 to 190 nm at a wavelength of 550 nm. For example, the positive B layer may have a biaxiality of -1.3 to -0.5, or -1.0 to -0.5 at a wavelength of 550 nm. In the above ranges, the viewing angle and light leakage improvement effects from the side when the negative B layer is laminated as described above may be further enhanced.

[0109] The positive B layer may have a thickness-wise phase difference of -255 to -70 nm at a wavelength of 550 nm. Within this range, it may be easy to improve the viewing angle and light leakage from the side when laminating the negative B layer described above. For example, the positive B layer may have a thickness-wise phase difference of -240 to -100 nm, or -120 to -110 nm at a wavelength of 550 nm.

[0110] The positive B layer can be formed of a material that satisfies nz>nx>ny (where nx, ny, and nz are the refractive indices in the slow axis direction, the fast axis direction, and the thickness direction at a wavelength of 550 nm, respectively) and can implement the above-described in-plane phase difference and degree of biaxiality.

[0111] In one embodiment, the positive B layer may be a liquid crystal layer or a non-liquid crystal layer. Preferably, the positive B layer may be a non-liquid crystal layer.

[0112] In one embodiment, the positive B layer may be formed of a polymer or composition comprising a polymer having negative birefringence. Here, "negative birefringence" means a material whose refractive index decreases in the direction of stretching. That is, the direction perpendicular to the direction of stretching becomes the ground axis.

[0113] In one specific example, the positive B layer may be a film formed of a composition including one or more polymers from among cellulose-based polymers including triacetyl cellulose (TAC), polyester-based polymers including polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, cyclic polyolefin (COP)-based polymers, unmodified polycarbonate-based polymers, modified polycarbonate-based polymers, polyethersulfone-based polymers, unmodified polystyrene-based polymers, modified polystyrene-based polymers, polysulfone-based polymers, polyamide-based polymers, polyimide-based polymers, polyolefin-based polymers, polyarylate-based polymers, polyvinyl alcohol-based polymers, polyvinyl chloride-based polymers, polyvinylidene chloride-based polymers, and acrylic-based polymers.

[0114] In another embodiment, the positive B layer may be a film or coating layer comprising a composition comprising at least one of a cellulosic compound or a polymer thereof, an aromatic compound or a polymer thereof.

[0115] The cellulose compound may include at least a unit in which at least some of the hydrogens of the hydroxyl groups [C2 hydroxyl group, C3 hydroxyl group, or C6 hydroxyl group] of the sugar monomers forming the cellulose are replaced with acyl groups or ether groups. That is, the cellulose compound may include at least one of a cellulose ester compound and a cellulose ether compound.

[0116] For example, the cellulose-based compound may include a cellulose ester-based compound that includes at least a unit in which at least some of the hydrogens of the hydroxyl groups (OH) [C2 hydroxyl group, C3 hydroxyl group, or C6 hydroxyl group] of the sugar monomer forming the cellulose are substituted with acyl groups, as shown in the following chemical formula 1: wherein the acyl groups may be substituted or unsubstituted.

[0117] [Chemical Formula 1]

[0118]

[0119] (In the above chemical formula 1, n is an integer greater than or equal to 1)

[0120] Substituents for the cellulose ester group or acyl group may each include one or more of halogen, nitro, alkyl (e.g., an alkyl group having 1 to 20 carbon atoms), alkenyl (e.g., an alkenyl group having 2 to 20 carbon atoms), cycloalkyl (e.g., a cycloalkyl group having 3 to 10 carbon atoms), aryl (e.g., an aryl group having 6 to 20 carbon atoms), heteroaryl (e.g., a heteroaryl group having 3 to 10 carbon atoms), alkoxy (e.g., an alkoxy group having 1 to 20 carbon atoms), acyl, and halogen-containing functional groups. The substituents may be the same or different.

[0121] The above "acyl" can be RC(=O)-* (* is a linking symbol, R is an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an arylalkyl group having 7 to 20 carbon atoms), as is known to those skilled in the art. The above "acyl" is bonded to the ring of cellulose through an ester bond in cellulose (via an oxygen atom).

[0122] The above "alkyl", "alkenyl", "cycloalkyl", "aryl", "heteroaryl", "alkoxy", and "acyl" are each, for convenience, non-halogenated compounds that do not contain halogen. The composition for the positive B layer may contain only the cellulose ester compound or a mixture of the cellulose ester compounds.

[0123] The above “halogen” means fluorine (F), Cl, Br or I, preferably F.

[0124] The above "halogen-containing functional group" is an organic functional group containing one or more halogens, and may include an aromatic, aliphatic, or alicyclic functional group. For example, the halogen-containing functional group may refer to, but is not limited to, a halogen-substituted alkyl group having 1 to 20 carbon atoms, a halogen-substituted alkenyl group having 2 to 20 carbon atoms, a halogen-substituted alkynyl group having 2 to 20 carbon atoms, a halogen-substituted cycloalkyl group having 3 to 10 carbon atoms, a halogen-substituted alkoxy group having 1 to 20 carbon atoms, a halogen-substituted acyl group, a halogen-substituted aryl group having 6 to 20 carbon atoms, or a halogen-substituted arylalkyl group having 7 to 20 carbon atoms.

[0125] The above "halogen-substituted acyl group" may be R'-C(=O)-* (* is a linking symbol, R' is a halogen-substituted alkyl group having 1 to 20 carbon atoms, a halogen-substituted cycloalkyl group having 3 to 20 carbon atoms, a halogen-substituted aryl group having 6 to 20 carbon atoms, or a halogen-substituted arylalkyl group having 7 to 20 carbon atoms). The above "halogen-substituted acyl group" may be bonded to a ring of cellulose through an ester bond in cellulose (via an oxygen atom).

[0126] The above cellulose ester compound can be manufactured by a conventional method known to those skilled in the art, or can be purchased as a commercially available product and used in manufacturing a positive B layer. For example, a cellulose ester compound having an acyl group as a substituent can be manufactured by reacting a sugar monomer or a polymer of sugar monomers forming the cellulose of the above-described chemical formula 1 with trifluoroacetic acid or trifluoroacetic anhydride, or by reacting trifluoroacetic acid or trifluoroacetic anhydride and then further reacting with an acylating agent (e.g., an anhydride of a carboxylic acid or a carboxylic acid), or by reacting trifluoroacetic acid or trifluoroacetic anhydride and an acylating agent together.

[0127] The aromatic compound contains a phenyl group and may include, but is not limited to, a polystyrene-based compound, a fluorobenzene, or a difluorostyrene structure. In one specific example, the polystyrene-based compound may contain a moiety represented by the following chemical formula 2:

[0128] [Chemical Formula 2]

[0129]

[0130] (In the above chemical formula 2, is the connecting part of the silver element,

[0131] R 1 , R 2 , R 3 are each independently a hydrogen atom, an alkyl group, a substituted alkyl group, or a halogen,

[0132] R is each independently a substituent on the styrene ring,

[0133] n is an integer from 0 to 5 indicating the number of substituents on the styrene ring).

[0134] Examples of substituents R on the styrene ring may include alkyl, substituted alkyl, halogen, hydroxy, carboxy, nitro, alkoxy, amino, sulfonate, phosphate, acyl, acyloxy, phenyl, alkoxycarbonyl, cyano, and the like.

[0135] In one specific example, R 1 , R 2 , R 3 One or more of the above may be a halogen, more preferably fluorine.

[0136] The composition for the positive B layer may further include an additive having an aromatic fused ring in addition to the above-described cellulose compound and aromatic compound. The additive having an aromatic fused ring may play a role in controlling wavelength dispersion. Examples of the additive having an aromatic fused ring include 2-naphthylbenzoate, anthracene, phenanthrene, 2,6-naphthalenedicarboxylic acid diester, and the like. The additive having an aromatic fused ring may be included in the composition for the positive B layer in an amount of 0.1 wt% to 30 wt%, preferably 1 wt% to 10 wt%. Within the above range, the additive has the effect of controlling the phase difference expression rate and wavelength dispersion.

[0137] According to one embodiment, the positive B layer may be a coating layer or a cured product of a coating layer comprising the composition for the positive B layer described above.

[0138] According to one embodiment, the positive B layer may be formed directly on the negative B layer. Here, 'directly formed' means that there is no adhesive or bonding layer between the positive B layer and the negative B layer.

[0139] In one specific example, the negative B layer can be manufactured by stretching an unstretched film. Specifically, the unstretched film can be manufactured by a solvent casting method. By coating the composition for the positive B layer on the unstretched film to form a coating layer, and simultaneously stretching the laminate of the unstretched film and the coating layer, the positive B layer and the negative B layer can be manufactured simultaneously. The coating layer can also be cured. For example, by manufacturing the unstretched film by a solvent casting method with a composition having positive birefringence, coating the unstretched film with a composition having negative birefringence to form a coating layer, and simultaneously stretching the laminate of the unstretched film and the coating layer along the MD axis of the unstretched film, the positive B layer and the negative B layer can be manufactured simultaneously. This can provide a thickness reduction effect.

[0140] According to one embodiment, the negative B layer and the positive B layer may have the same stretching direction. In this case, the stretching direction may be the direction of the light absorption axis of the polarizer.

[0141] For example, the positive B layer can be manufactured by coating the composition for the positive B layer on the unstretched film for the negative B layer to form a coating layer and stretching the coating layer. The coating layer can also be cured.

[0142] For example, a positive B layer may be formed by coating a composition for a positive B layer on an arbitrary substrate film to form a coating layer, stretching a laminate of the substrate film and the coating layer to form a positive B layer on the substrate film, and then transferring the positive B layer onto a negative B layer, thereby being included in a polarizing plate. The coating layer may be cured.

[0143] The positive B layer may have a thickness of 1 to 60 μm, specifically 1 to 30 μm, or 1 to 10 μm. Within the above range, it may be applied to a polarizing plate, facilitate the implementation of the phase difference of the present invention, and facilitate the thinning of the polarizing plate.

[0144] A laminate of positive B layers and negative B layers

[0145] The laminate of the positive B layer and the negative B layer can have an in-plane retardation of 20 to 110 nm at a wavelength of 550 nm. In this range, the viewing angle and color improvement effects from the side can be excellent. For example, the laminate can have an in-plane retardation of 40 to 90 nm, 30 to 80 nm, or 50 to 80 nm at a wavelength of 550 nm.

[0146] The laminate of the positive B layer and the negative B layer can have a thickness direction retardation of -10 to 95 nm at a wavelength of 550 nm. In this range, the viewing angle and color improvement effects from a side can be excellent. For example, the laminate can have a thickness direction retardation of 0 to 95 nm, 5 to 95 nm, 10 to 95 nm, 10 to 90 nm, or 20 to 75 nm at a wavelength of 550 nm. In this range, the viewing angle and color improvement effects from a side can be further improved.

[0147] According to one implementation example, the positive B layer and the negative B layer may satisfy Equation 1 below, and the value of Equation 2 below may be 1.1 to 3.7, for example, 1.2 to 3.3, for example, 1.3 to 3.0: In this case, the viewing angle and color improvement effect from the side may be improved.

[0148] [Formula 1]

[0149] Re(-B) < Re(+B)

[0150] [Formula 2]

[0151] Re(+B) / Re(-B)

[0152] (In the above equations 1 and 2, Re(-B) and Re(+B) are the in-plane phase differences of the negative B layer and the positive B layer, respectively, at a wavelength of 550 nm.)

[0153] For example, the value of the above formula 2 can be 1.1 to 1.8 or 2.4 to 3.6. In the above range, the viewing angle and color improvement effects from the side can be further improved.

[0154] The thickness of the laminate of the positive B layer and the negative B layer may be 95% or more, for example, 95 to 100%, or 100%, of the thickness of the phase difference layer. In the above range, a thinning effect of the polarizing plate may be possible.

[0155] polarizer

[0156] A polarizer converts incident natural light or polarized light into linearly polarized light in a specific direction, and can be manufactured from a polymer film containing a polyvinyl alcohol-based resin as a main component. Specifically, the polarizer can be manufactured by dyeing the polymer film with iodine or a dichroic dye and stretching it in the MD (machine direction). In one specific example, the polarizer can be manufactured by subjecting the polyvinyl alcohol-based film to a swelling process, a dyeing step, a stretching step, or optionally, at least one of a complementary color step and a crosslinking step.

[0157] A polarizer has a light absorption axis and a light transmission axis in the in-plane direction, and the light absorption axis can be the MD of the polarizer, and the light transmission axis can be the TD (transverse direction) of the polarizer.

[0158] The polarizer may have a single light transmittance of 40% or more, for example, 40 to 46%, and a polarization degree of 95% or more, for example, 95 to 99.999%. In the above range, when combined with a phase difference layer, anti-reflection performance can be improved. The above "light transmittance" and "polarization degree" are values ​​measured at a wavelength of 380 nm to 780 nm, and are values ​​reflecting the visibility in the corresponding wavelength range.

[0159] The polarizer may have a thickness of 2 to 30 μm, specifically 4 to 25 μm, and may be used in a polarizing plate within the above range.

[0160] The polarizer may be laminated directly onto the positive B layer without an adhesive layer or adhesive layer, or may be laminated onto the positive B layer by an adhesive layer or adhesive layer.

[0161] A polarizing plate may further include a protective layer on one or the other side of the polarizer. The protective layer may be a first protective layer or a second protective layer. The protective layer may be included in one or more layers of the polarizing plate.

[0162] First protective layer

[0163] One side of the polarizer, preferably one side having a phase difference layer of the polarizer, may further include one or more first protective layers. The first protective layer may be included in the laminate to provide additional functions to the laminate and / or the polarizing plate. For example, the first protective layer may enhance the durability and mechanical strength of the laminate by supplementing the thickness of the laminate.

[0164] For example, the first protective layer may be positioned between the polarizer and the positive B layer. For example, the first protective layer may be positioned opposite the positive B layer to the negative B layer.

[0165] The first protective layer is an optically transparent film, and may be a film made of one or more resins selected from the group consisting of cellulose-based films including triacetyl cellulose (TAC), polyester-based films including polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate, cyclic olefin polymer (COP)-based films, cyclic olefin copolymer (COC)-based films, polycarbonate-based films, polyethersulfone-based films, polysulfone-based films, polyamide-based films, polyimide-based films, polyolefin-based films, polyarylate-based films, polyvinyl alcohol-based films, polyvinyl chloride-based films, and polyvinylidene chloride-based films.

[0166] In one specific example, the first protective layer may have a front-side in-plane phase difference and a thickness-wise phase difference of 10 nm or less, for example, 0 nm to 5 nm, at a wavelength of 550 nm. Within this range, the reflectivity reduction effect of the laminate may not be affected on the side surface.

[0167] The polarizing plate may further include a second protective layer, as described below, on the other side of the polarizer. The second protective layer may be laminated in one or more layers on the upper surface of the polarizer.

[0168] Second protective layer

[0169] The second protective layer may further protect the polarizer from the external environment and enhance the mechanical strength of the polarizing plate. The second protective layer may be one or more of a protective film or a protective coating layer.

[0170] In one specific example, the second protective layer may be an optically transparent film, such as a film made of one or more resins selected from the group consisting of cellulose-based films including triacetyl cellulose (TAC), polyester-based films including polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate (PET), polybutylene naphthalate, cyclic olefin polymer (COP)-based films, cyclic olefin copolymer (COC)-based films, polycarbonate-based films, polyethersulfone-based films, polysulfone-based films, polyamide-based films, polyimide-based films, polyolefin-based films, polyarylate-based films, polyvinyl alcohol-based films, polyvinyl chloride-based films, and polyvinylidene chloride-based films.

[0171] A functional coating layer may be additionally formed on at least one surface of the second protective layer. For example, the functional coating layer may be an anti-reflection layer, a low-reflection layer, a hard coating layer, an anti-fingerprint layer, an anti-glare layer, a primer layer, etc.

[0172] The second protective layer may have a thickness of 5 µm to 70 µm, specifically 15 µm to 45 µm, and may be used in a polarizing plate within the above range.

[0173] Figures 1 and 2 are cross-sectional views of a polarizing plate of the present invention.

[0174] Referring to FIG. 1, the polarizing plate may include a polarizer (30); a negative B layer (10) and a positive B layer (20) sequentially laminated on the lower surface of the polarizer (30); and a second protective layer (40) sequentially laminated on the upper surface of the polarizer (30).

[0175] Referring to FIG. 2, the polarizing plate may include a polarizer (30); a negative B layer (10) and a positive B layer (20) sequentially laminated on the upper surface of the polarizer (30); and a second protective layer (40) laminated on the lower surface of the polarizer (30).

[0176] Although not shown in FIGS. 1 and 2, when laminating the polarizer, each phase difference layer, and the protective layer, the polarizing plate may additionally use an adhesive layer, an adhesive layer, or a point-adhesive layer. In addition, a first protective layer may additionally be used between the polarizer and the positive B layer.

[0177] The optical display device of the present invention includes a polarizing plate according to an embodiment of the present invention. The optical display device may include a liquid crystal display device.

[0178] In one specific example, the liquid crystal display device may be a liquid crystal display device having a liquid crystal layer of a planar switching mode, such as an IPS mode or FFS mode.

[0179] In one specific example, the polarizing plate of the present invention can be used as a viewer-side polarizing plate or a light source-side polarizing plate.

[0180] Referring to FIG. 3, the liquid crystal display device includes a liquid crystal panel (100) having a liquid crystal layer, a polarizing plate on the viewing side laminated on one side of the liquid crystal panel (100), and a polarizing plate on the light source side laminated on the other side of the liquid crystal panel (100), and the polarizing plate on the viewing side includes a positive B layer (20), a negative B layer (10), and a polarizer (30) sequentially laminated from the liquid crystal panel (100).

[0181] In Fig. 3, the liquid crystal layer may be a liquid crystal in an in-plane switching mode, for example, an IPS mode liquid crystal layer. The ground axis of the liquid crystal layer and the light absorption axis of the polarizer in the viewer-side polarizing plate are substantially orthogonal. The light absorption axis of the polarizer in the viewer-side polarizing plate is substantially orthogonal to the light absorption axis of the polarizer in the light source-side polarizing plate. The liquid crystal tilt angle of the liquid crystal in the liquid crystal layer may be 0 to 3°. The above 'liquid crystal tilt angle' can be measured by a conventional method known to those skilled in the art.

[0182] Referring to FIG. 4, the liquid crystal display device includes a liquid crystal panel (100) having a liquid crystal layer, a viewer-side polarizing plate (300) laminated on one side of the liquid crystal panel (100), and a light source-side polarizing plate laminated on the other side of the liquid crystal panel (100), and the light source-side polarizing plate includes a positive B layer (20), a negative B layer (10), and a polarizer (30) sequentially laminated from the liquid crystal panel (100).

[0183] In Fig. 4, the liquid crystal layer may be a liquid crystal in an in-plane switching mode, for example, a liquid crystal layer in an FPS mode. The ground axis of the liquid crystal layer and the light absorption axis of the polarizer in the light source-side polarizing plate are substantially orthogonal. The light absorption axis of the polarizer in the viewer-side polarizing plate is substantially orthogonal to the light absorption axis of the polarizer in the light source-side polarizing plate. The liquid crystal tilt angle of the liquid crystal in the liquid crystal layer may be 0 to 3°. The above 'liquid crystal tilt angle' can be measured by a conventional method known to those skilled in the art.

[0184]

[0185] Hereinafter, the structure and operation of the present invention will be described in more detail through preferred embodiments of the present invention. However, these are presented as preferred examples of the present invention and should not be construed as limiting the present invention in any way.

[0186]

[0187] Example 1

[0188] A polyvinyl alcohol film (PS#60, Kuraray, Japan, thickness: 60 ㎛) was stretched 6 times along the MD axis of the polyvinyl alcohol film in an iodine aqueous solution at 55°C to produce a polarizer with a single-axis light transmittance of 43%.

[0189] A composition containing a cyclic olefin copolymer (COC, having positive birefringence) was cast by a solvent casting method to prepare an unstretched film. A cellulose ester composition (VM500, EASTMAN, having negative birefringence) was coated on the lower surface of the unstretched film to a predetermined thickness to prepare a coating layer, and the coating layer was cured to prepare an unstretched laminate having the unstretched film and the cured product of the cellulose ester-based coating layer. The unstretched laminate was stretched along the MD axis of the unstretched film at a predetermined stretching ratio, so that a negative B layer (a cyclic olefin copolymer-based stretched film, thickness: 50 μm) and a positive B layer (a cured product of the cellulose ester-based coating layer, thickness: 3 μm) were simultaneously prepared, as shown in Table 1 below.

[0190] The laminate was laminated on one side of the polarizer, and the negative B layer was laminated on one side of the polarizer in a roll-to-roll manner. A PET film was laminated as a protective layer on the other side of the polarizer, thereby manufacturing a polarizing plate laminated in the order of PET film - polarizer - negative B layer - positive B layer.

[0191]

[0192] Examples 2 to 5

[0193] In Example 1, a polarizing plate was manufactured in the same manner as in Example 1, except that the draw ratio was changed when manufacturing the negative B layer or the conditions in the solvent casting process were changed.

[0194]

[0195] Comparative Examples 1 to 8

[0196] In Example 1, a polarizing plate was manufactured in the same manner as in Example 1, except that the draw ratio was changed when manufacturing the negative B layer or the conditions in the solvent casting process were changed.

[0197]

[0198] The Re, Rth, and NZ of each phase difference layer are values ​​obtained at a wavelength of 550 nm using AXOSCAN.

[0199] The properties below were evaluated using the polarizing plates of the examples and comparative examples and are shown in Table 1 below.

[0200] (1) Maximum light transmittance in all directions (unit: %): Instead of the polarizing plate on the viewer side, the polarizing plates manufactured in the examples and comparative examples were attached and operated on a Samsung Electronics TV model equipped with an IPS liquid crystal panel. Then, the maximum light transmittance in the black state at the entire viewing angle was calculated using the Extended Jones Matrix method through the TECHWIZ 1D (SANAI SYSTEM, KOREA) simulation program. However, the reduction in light transmittance due to the color filter inside the panel was excluded from the above calculation. The lower the maximum light transmittance, the more it can prevent light leakage and improve visibility.

[0201] (2) Results of visibility evaluation when voltage is not applied: The polarizing plates manufactured in the examples and comparative examples were bonded to a 65-inch FFS panel (China BOE) as a polarizing plate on the viewing side to conduct a visibility evaluation. Black visibility and color were evaluated by visual inspection.

[0202] Example 12345 Negative B layer Re (nm) 30 50 50 110 130 Rth (nm) 120 200 150 220 325 NZ 4.5 4.5 3.5 2.5 3.0 Positive B layer Re (nm) 110 100 120 190 160 Rth (nm) -110-200-120-190-240 NZ -0.5-1.5-0.5-0.5-1.0 Laminate of negative B layer and positive B layer Re (nm) 80 50 70 80 30 Rth (nm) 100 30 30 85 Angle 1 (°) 00 000 Angle 2 (°) 90 90 90 90 90 Maximum light transmittance in all directions 0.47 0 8 0.75 23 0.34 96 0.52 8 0.55 74 Visibility Evaluation: 5, black feeling excellent; purple, yellow feeling excellent; 6, black feeling excellent; purple, yellow feeling excellent; 7, black feeling excellent; purple, yellow feeling excellent; 8, black feeling excellent; purple, blue feeling excellent; 9, black feeling excellent; purple, yellow feeling excellent

[0203]

[0204] Comparative Example 12345678 Negative B layer Re (nm) 20150 50 110 130 90 60 130 Rth (nm) 40 60 0 75 49 5 26 0 36 0 120 520 NZ 2.5 4.5 2.0 5.0 2.5 4.5 2.5 4.5 Positive B layer Re (nm) 130 110 100 140 90 200 100 150 Rth (nm) -260-110-150-140-135-400-250-105 NZ -1.5-0.5-1.0-0.5-1.0-1.5-2.0-0.2 Negative B layer and positive B layer Laminated bodyRe(nm)110405030401104020Rth(nm)-220490-75355125-40-130415Angle 1(°)00000000Angle 2(°)9090909090909090Maximum light transmittance in all directions9.7922.12.7323.110.84.1276.0217.53Visibility evaluation 10, poor black feeling; strong light leakage visible; Purple visibility 11, poor black feeling; strong light leakage visible; Yellow visibility 12, poor black feeling; light leakage visible; Purple visibility 13, poor black feeling; strong light leakage visible; Yellow visibility 14, poor black feeling; strong light leakage visible; Purple, yellow visibility 15, poor black feeling; strong light leakage visible; Poet Bora 16, Black feeling bad; Poet with strong light; Poet Bora 17, Black feeling bad; Poet with strong light; Poet with yellow light

[0205]

[0206] *Angle 1: The angle formed by the ground axis of the negative B layer when the light absorption axis of the polarizer is 0°.

[0207] *Angle 2: The angle formed by the ground axis of the positive B layer when the light absorption axis of the polarizer is 0°.

[0208]

[0209] As shown in Table 1 above, the polarizing plate of one embodiment exhibited excellent black visibility, providing improved side viewing angles and color gamut. Furthermore, the polarizing plate of one embodiment exhibited a significantly low maximum light transmittance of less than 0.5% in all directions, suggesting excellent light leakage reduction. Furthermore, the polarizing plate of one embodiment was capable of roll-to-roll winding and production, demonstrating excellent cost-effectiveness and processability.

[0210] However, as shown in Table 2 above, the polarizing plate of the comparative example did not provide all the effects of the polarizing plate of the above-described embodiment.

[0211] As shown in FIGS. 5 to 9, the polarizing plate of the embodiment provided good black visibility and no light leakage. On the other hand, as shown in FIGS. 10 to 17, the polarizing plate of the comparative example had poor black visibility and strong light leakage.

[0212]

[0213] Simple modifications or changes of the present invention can be easily implemented by a person having ordinary skill in the art, and all such modifications or changes can be considered to be included in the scope of the present invention.

Claims

1. A polarizer; and a phase difference layer laminated on one surface of the polarizer and including a negative B layer and a positive B layer, The negative B layer is positioned between the polarizer and the positive B layer, and the negative B layer has an in-plane phase difference of 30 to 130 nm and a biaxiality of 2.5 to 4.5 at a wavelength of 550 nm. The above positive B layer has an in-plane phase difference of 100 to 190 nm and a biaxiality of -1.5 to -0.5 at a wavelength of 550 nm, A polarizing plate in which the ground axis of the negative B layer forms -1 to 1° and the ground axis of the positive B layer forms 89 to 91° with respect to the light absorption axis of the polarizer.

2. A polarizing plate in accordance with claim 1, wherein the negative B layer has a thickness direction phase difference of 60 to 325 nm at a wavelength of 550 nm.

3. A polarizing plate according to claim 1, wherein the negative B layer is manufactured by a solvent casting method.

4. A polarizing plate according to claim 1, wherein the negative B layer contains fine particles.

5. A polarizing plate according to claim 4, wherein the fine particles contain silicon dioxide.

6. A polarizing plate according to claim 1, wherein the negative B layer and the positive B layer have the same stretching direction.

7. A polarizing plate in accordance with claim 6, wherein the stretching direction is the direction of the light absorption axis of the polarizer.

8. A polarizing plate according to claim 1, wherein the negative B layer comprises a polymer having positive birefringence, and the positive B layer comprises a polymer having negative birefringence.

9. A polarizing plate according to claim 8, wherein the negative B layer comprises at least one of a cyclic olefin copolymer and a cellulose ester copolymer.

10. A polarizing plate according to claim 8, wherein the positive B layer comprises at least one of a cellulose compound or a polymer thereof, an aromatic compound or a polymer thereof.

11. A polarizing plate in accordance with claim 1, wherein the laminate of the positive B layer and the negative B layer has an in-plane phase difference of 20 to 110 nm at a wavelength of 550 nm.

12. A polarizing plate in accordance with claim 1, wherein the laminate of the positive B layer and the negative B layer has a thickness direction phase difference of -10 to 95 nm at a wavelength of 550 nm.

13. A polarizing plate in the first paragraph, wherein the positive B layer has a thickness direction phase difference of -255 to -70 nm at a wavelength of 550 nm.

14. In the first paragraph, the positive B layer and the negative B layer satisfy the following equation 1, and the value of the following equation 2 is 1.1 to 3.7, a polarizing plate: [Formula 1] Re(-B) < Re(+B) [Formula 2] Re(+B) / Re(-B) (In the above equations 1 and 2, Re(-B) and Re(+B) are the in-plane phase differences of the negative B layer and the positive B layer, respectively, at a wavelength of 550 nm.) 15. A polarizing plate in accordance with claim 1, wherein the thickness of the laminate of the positive B layer and the negative B layer is 95% or more of the thickness of the phase difference layer.

16. A polarizing plate in accordance with claim 1, wherein the phase difference layer is laminated on the light incident surface or light exit surface of the polarizer.

17. A polarizing plate according to claim 1, wherein a protective layer is further laminated on one side or the other side of the polarizer.

18. An optical display device comprising a polarizing plate according to any one of claims 1 to 17.

Images