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 positive B layer and a negative B layer, wherein the positive B layer is disposed between the polarizer and the negative B layer, the positive B layer has an in-plane retardation of 110 to 180 nm and a degree of biaxiality of -1.5 to -0.5 at a wavelength of 550 nm, the negative B layer has an in-plane retardation of 40 to 120 nm and a degree of biaxiality of 2.5 to 4.0 at a wavelength of 550 nm, and with respect to a light absorption axis of the polarizer, a slow axis of the positive B layer forms -1 to 1° and a slow axis of the negative B layer forms 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, the demand for wide viewing angles has increased. Therefore, the development of polarizing plates capable of securing such a wide viewing angle is necessary. Furthermore, polarizing plates must be capable of securing a wide viewing angle and 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 capable of wide-width manufacturing, thereby improving economic efficiency and processability.

[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 positive B layer and a negative B layer, wherein the positive B layer is positioned between the polarizer and the negative B layer, the positive B layer has an in-plane phase difference of 110 to 180 nm and a degree of biaxiality of -1.5 to -0.5 at a wavelength of 550 nm, the negative B layer has an in-plane phase difference of 40 to 120 nm and a degree of biaxiality of 2.5 to 4.0 at a wavelength of 550 nm, and the slow axis of the positive B layer forms -1 to 1° and the slow axis of the negative B layer forms 89 to 91° with respect to a light absorption axis of the polarizer.

[0013] In 2.1, the negative B layer may have a thickness direction phase difference of 120 to 270 nm at a wavelength of 550 nm.

[0014] In 3.1-2, the negative B layer can be manufactured by a melt extrusion method.

[0015] In 4.1-3, the negative B layer and the positive B layer may have the same stretching direction.

[0016] In 5.1-4, the stretching direction may be orthogonal to the light absorption axis direction of the polarizer.

[0017] In 6.1-5, the negative B layer may include a polymer having positive birefringence, and the positive B layer may include a polymer having negative birefringence.

[0018] In 7.1-6, the negative B layer may include a cyclic olefin copolymer.

[0019] In 8.1-7, the positive B layer may include at least one of a cellulose compound or a polymer thereof, an aromatic compound or a polymer thereof.

[0020] In 9.1-8, the laminate of the positive B layer and the negative B layer may have an in-plane phase difference of 40 to 110 nm at a wavelength of 550 nm.

[0021] In 10.1-9, the laminate of the positive B layer and the negative B layer may have a thickness direction phase difference of 0 to 100 nm at a wavelength of 550 nm.

[0022] In 11.1-10, the positive B layer may have a thickness direction phase difference of -260 to -120 nm at a wavelength of 550 nm.

[0023] In 12.1-11, the positive B layer and the negative B layer satisfy Equation 1 below, and the value of Equation 2 below may be 1.2 to 3.0:

[0024] [Formula 1]

[0025] Re(-B) < Re(+B)

[0026] [Formula 2]

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

[0028] (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.)

[0029] In 13.1-12, 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.

[0030] In 14.1-13, the phase difference layer can be laminated on the light incident surface or light exit surface of the polarizer.

[0031] A polarizing plate in which a protective layer is further laminated on one side or the other side of the polarizer in 15.1-14.

[0032] According to another embodiment, an optical display device is provided.

[0033] The above optical display device includes a polarizing plate of the present invention.

[0034]

[0035] The present invention provides a polarizing plate that provides a visibility improvement effect including a side viewing angle and color improvement effect.

[0036] The present invention provides a polarizing plate that provides a light leakage improvement effect.

[0037] The present invention provides a polarizing plate capable of wide-width manufacturing, thereby improving economic efficiency and processability.

[0038] The present invention provides a polarizing plate capable of being thinned.

[0039]

[0040] Figure 1 is a cross-sectional view of a polarizing plate of one embodiment.

[0041] Figure 2 is a cross-sectional view of a polarizing plate of another embodiment.

[0042] Figure 3 is a cross-sectional view of a liquid crystal display device of one embodiment.

[0043] Figure 4 is a cross-sectional view of a liquid crystal display device of another embodiment.

[0044] Figures 5 to 17 show the results of visibility evaluations of examples and comparative examples, respectively.

[0045]

[0046] 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.

[0047] In order to clearly explain the present invention in the drawings, parts irrelevant to the description have been omitted, and the same or similar components have been designated by the same designation 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.

[0048] 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.

[0049] 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.

[0050] 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:

[0051] [Formula A]

[0052] Re = (nx - ny) xd

[0053] [Formula B]

[0054] Rth = ((nx + ny) / 2 - nz) xd

[0055] [Formula C]

[0056] NZ = (nx - nz) / (nx - ny)

[0057] (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).)

[0058] 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.

[0059] 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.

[0060] 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 0.8% or less, for example, 0 to 0.8%, 0 to 0.5%, or 0 to 0.3%, and the light leakage improvement effect may be excellent in the above range. The 'light transmittance' refers to the degree of light leaking depending on the visual angle assuming that the backlight light is 100% when the display expresses Black, and is a value reflecting the tristimulus values ​​of the eye. The lower the 'light transmittance', the better the viewing angle characteristics may be.

[0061] According to one implementation example, a polarizing plate with excellent cost-effectiveness and excellent thinness was provided by enabling wide-width manufacturing of a phase difference layer.

[0062] According to one embodiment, a polarizing plate includes a polarizer; and a retardation layer laminated on one surface of the polarizer and including a positive B layer and a negative B layer, wherein the positive B layer is positioned between the polarizer and the negative B layer, the positive B layer has an in-plane retardation of 110 to 180 nm and a degree of biaxiality of -1.5 to -0.5 at a wavelength of 550 nm, the negative B layer has an in-plane retardation of 40 to 120 nm and a degree of biaxiality of 2.5 to 4.0 at a wavelength of 550 nm, and a slow axis of the positive B layer is at an angle of -1 to 1° with respect to a light absorption axis of the polarizer, and a slow axis of the negative B layer is at an angle of 89 to 91°.

[0063] According to one embodiment, the laminate of the positive B layer and the negative B layer can have an in-plane phase difference of 40 to 110 nm and a thickness direction phase difference of 0 to 100 nm at a wavelength of 550 nm. In the above range, the above-described effect can be remarkably excellent.

[0064] According to one implementation example, the polarizing plate can be a viewer-side polarizing plate or a light source-side polarizing plate.

[0065] 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 positive B layer, the negative 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.

[0066] 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 positive B layer, the negative B layer, the IPS panel, and the viewer-side polarizer. A person of ordinary skill in the art refers to this as an E-mode structure.

[0067] 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.

[0068] Hereinafter, each component of the polarizing plate of the present invention will be described in detail.

[0069] Positive B layer

[0070] The positive B layer is positioned between the polarizer and the negative B layer in the polarizing plate. The positive B layer can be easily improved in terms of side viewing angle and color by being laminated at this position. A polarizing plate laminated in this order from the polarizer to the negative B layer and then to the positive B layer may not be able to properly achieve the side viewing angle and color improvement effect and the light leakage improvement effect of the present invention, or the effects may be weak.

[0071] The positive B layer has a ground axis and a true axis in the in-plane direction.

[0072] The slow axis of the positive 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 positive B layer can form 0°.

[0073] The positive B layer has an in-plane phase difference of 110 to 180 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 as described below.

[0074] The in-plane phase difference and degree of biaxiality of the positive B layer and the in-plane phase difference and degree of biaxiality of the negative 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, there was an effect of improving the viewing angle and color from the side and an effect of improving light leakage.

[0075] For example, the positive B layer may have an in-plane phase difference of 110 to 160 nm, or 120 to 160 nm at a wavelength of 550 nm. For example, the positive B layer may have a biaxiality of -1.0 to -0.5, or -0.9 to -0.5. In the above ranges, the aforementioned viewing angle improvement and light leakage improvement effects may be more excellent.

[0076] The positive B layer may have a thickness direction retardation of -260 to -120 nm at a wavelength of 550 nm. In this range, it may be easy to improve the viewing angle and light leakage from the side when laminating the negative B layer as described below. For example, the positive B layer may have a thickness direction retardation of -210 to -120 nm, -180 to -120 nm, or -160 to -120 nm at a wavelength of 550 nm. In this range, the aforementioned viewing angle improvement and light leakage improvement effects may be more excellent.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] [Chemical Formula 1]

[0085]

[0086] (In the above chemical formula 1, n is an integer greater than or equal to 1)

[0087] 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.

[0088] 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).

[0089] 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.

[0090] The above “halogen” means fluorine (F), Cl, Br or I, preferably F.

[0091] 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.

[0092] 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).

[0093] 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.

[0094] 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:

[0095] [Chemical Formula 2]

[0096]

[0097] (In the above chemical formula 2, is the connecting part of the silver element,

[0098] R 1 , R 2 , R 3 are each independently a hydrogen atom, an alkyl group, a substituted alkyl group, or a halogen,

[0099] R is each independently a substituent on the styrene ring,

[0100] n is an integer from 0 to 5 indicating the number of substituents on the styrene ring).

[0101] 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.

[0102] In one specific example, R 1 , R 2 , R 3 One or more of the above may be a halogen, more preferably fluorine.

[0103] 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.

[0104] According to one embodiment, the positive B layer may be a coating layer comprising the composition for the positive B layer described above or a cured product of the coating layer.

[0105] 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.

[0106] 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 melt extrusion 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 melt extrusion method with a composition having positive birefringence, coating the composition for the positive B layer having negative birefringence to form a coating layer, and simultaneously stretching the laminate of the unstretched film and the coating layer along the TD uniaxial direction of the unstretched film, the positive B layer and the negative B layer can be manufactured simultaneously.

[0107] This can provide a thickness thinning effect. In addition, the above-described TD stretching can improve the manufacturing process of the polarizer by enabling the negative B layer and positive B layer to be manufactured in a wide width.

[0108] 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 orthogonal to the light absorption axis direction of the polarizer.

[0109] For example, a positive B layer can be prepared by coating the composition for the positive B layer on a negative B layer below to form a coating layer and stretching the coating layer. The coating layer may be cured.

[0110] 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.

[0111] 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.

[0112] Negative B layer

[0113] 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).

[0114] The negative B layer has a ground axis and a forward axis in the in-plane direction.

[0115] The ground axis of the negative B layer can form 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 negative B layer can form an angle of 90°.

[0116] The negative B layer has an in-plane retardation of 40 to 120 nm at a wavelength of 550 nm and a degree of biaxiality of 2.5 to 4.0. When the above in-plane retardation and degree of biaxiality ranges are simultaneously satisfied, the viewing angle and color from the side can be improved when laminated on one side of the above-described positive B layer.

[0117] For example, the negative B layer can have an in-plane phase shift of 40 to 110 nm. For example, the negative B layer can have a biaxiality of 3.0 to 4.0.

[0118] The negative B layer may have a thickness-wise retardation of 120 to 270 nm at a wavelength of 550 nm. In this range, the above-described in-plane retardation and degree of biaxiality may be easily achieved. For example, the negative B layer may have a thickness-wise retardation of 140 to 245 nm. For example, the thickness-wise retardation may be 140 to 240 nm, 140 to 220 nm. In this range, the viewing angle and color improvement effects from the side may be further enhanced.

[0119] 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.

[0120] However, the present invention specifically uses a negative B layer manufactured by processing a composition for a negative B layer by a melt extrusion method to manufacture an unstretched film, and then uniaxially stretching the manufactured unstretched film in the TD of the unstretched film.

[0121] Film manufacturing methods are generally categorized into two types: melt extrusion and solution 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 offers high productivity with relatively low equipment costs.

[0122] In one specific embodiment, the polymer may exhibit positive birefringence. Here, "positive birefringence" means a material whose refractive index increases in the stretching direction. That is, the stretching direction and the slow axis are coincident. Positive birefringence satisfies the relationship between the light absorption axis of the polarizer and the slow axis of the negative B layer by enabling the production of a negative B layer by TD uniaxial stretching, thereby improving economy and processability by enabling roll-to-roll winding and production of the polarizing plate.

[0123] The above polymer may be a cyclic olefin polymer.

[0124] Cyclic olefin polymers are polymers having a cyclic olefin structure. Cyclic olefin polymers include norbornene polymers, monocyclic olefin polymers, cyclic conjugated diene polymers, vinyl alicyclic hydrocarbon polymers, or hydrides thereof.

[0125] 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.

[0126]

[0127] A laminate of positive B layers and negative B layers

[0128] The laminate of the positive B layer and the negative B layer can have an in-plane retardation of 40 to 110 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 an in-plane retardation of 45 to 100 nm, 50 to 80 nm at a wavelength of 550 nm. For example, the in-plane retardation can be 60 to 80 nm. In this range, the viewing angle and color improvement effects from a side can be further enhanced.

[0129] The laminate of the positive B layer and the negative B layer can have a thickness direction retardation of 0 to 100 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 20 to 80 nm, 35 to 55 nm at a wavelength of 550 nm. For example, the thickness direction retardation can be 10 to 60 nm. In this range, the viewing angle and color improvement effects from a side can be further enhanced.

[0130] 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 1.2 to 3.0, for example, 1.4 to 3.0, for example, 1.3 to 2.6: In this case, the viewing angle and color improvement effect from the side may be improved.

[0131] [Formula 1]

[0132] Re(-B) < Re(+B)

[0133] [Formula 2]

[0134] Re(+B) / Re(-B)

[0135] (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.)

[0136] For example, the value of the above formula 2 can be 2 to 2.5. In this range, the viewing angle and color improvement effects from the side can be further improved.

[0137] 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.

[0138] polarizer

[0139] 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.

[0140] 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.

[0141] 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.

[0142] 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.

[0143] 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.

[0144] The 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.

[0145] First protective layer

[0146] 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.

[0147] 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.

[0148] 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.

[0149] 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.

[0150] 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.

[0151] Second protective layer

[0152] 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.

[0153] 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.

[0154] 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.

[0155] 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.

[0156] Figures 1 and 2 are cross-sectional views of a polarizing plate of the present invention.

[0157] Referring to FIG. 1, the polarizing plate may include a polarizer (30); a positive B layer (10) and a negative 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).

[0158] Referring to FIG. 2, the polarizing plate may include a polarizer (30); a positive B layer (10) and a negative 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).

[0159] 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.

[0160] 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.

[0161] 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.

[0162] 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.

[0163] 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 negative B layer (20), a positive B layer (10), and a polarizer (30) sequentially laminated from the liquid crystal panel (100).

[0164] 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.

[0165] 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 negative B layer (20), a positive B layer (10), and a polarizer (30) sequentially laminated from the liquid crystal panel (100).

[0166] 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.

[0167]

[0168] 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.

[0169]

[0170] Example 1

[0171] 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%.

[0172] A composition containing a cyclic olefin polymer (COP, positive birefringence) polymer was prepared as an unstretched film by melt extrusion. A cellulose ester composition (VM500, EASTMAN, negative birefringence) was coated on 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 TD axis of the unstretched film at a predetermined stretching ratio, so that a negative B layer (cyclic olefin polymer-based stretched film, thickness: 50 μm) and a positive B layer (cured product of the cellulose ester-based coating layer, thickness: 3 μm) were simultaneously prepared, as shown in Table 1 below.

[0173] The laminate was laminated onto one side of the polarizer, and the positive B layer was laminated onto one side of the polarizer in a roll-to-roll manner. A PET film was laminated as a protective layer onto the other side of the polarizer, thereby manufacturing a polarizing plate laminated in the order of PET film - polarizer - positive B layer - negative B layer.

[0174]

[0175] Examples 2 to 5

[0176] 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 melt extrusion process were changed.

[0177]

[0178] Comparative Examples 1 to 8

[0179] 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 extrusion process were changed.

[0180]

[0181] The Re, Rth, and NZ of each phase difference layer are values ​​obtained at a wavelength of 550 nm using AXOSCAN.

[0182] The properties below were evaluated using the polarizing plates of the examples and comparative examples and are shown in Table 1 below.

[0183] (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.

[0184] (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.

[0185] Example 12345 Positive B layer Re (nm) 110 120 120 130 180 Rth (nm) -165 - 120 - 240 - 130 - 180 NZ - 1.0 - 0.5 - 1.5 - 0.5 - 0.5 Negative B layer Re (nm) 50 40 70 60 120 Rth (nm) 175 140 245 180 240 NZ 4.0 4.0 4.0 3.5 2.5 Laminate of positive B layer and negative B layer Re (nm) 60 80 50 70 60 Rth (nm) 10 20 55 0 60 Angle 1 (°) 00 000 Angle 2 (°) 90 90 90 90 90 Maximum light transmittance in all directions 0.1 19 60.36 120.75 430.28 170.31 89 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, yellow feeling excellent; 9, black feeling excellent; purple, blue feeling excellent

[0186]

[0187] Comparative Example 12345678 Positive B layer Re (nm) 100 190 140 160 150 130 120 150 Rth (nm) -150-190-350-128-300-260-180-150 NZ -1.0-0.5-2.0-0.3-1.5-1.5-1.0-0.5 Negative B layer Re (nm) 80 50 80 100 30 130 110 120 Rth (nm) 200 100 160 350 75 455 165 480 NZ 3.0 2.5 2.5 4.0 3.0 4.0 2.0 4.5 Positive B layer and negative B layer Laminated body Re (nm) 2014 0 6 0 6 0 1 2 0 0 1 0 3 0 Rth (nm) 50-90-190 222-225 195-15 330 Angle 1 (°) 0 ... Yellow, blue poet 17, black feeling bad; strong light leak poet; yellow, blue poet

[0188]

[0189] *Angle 1: The angle formed by the ground axis of the positive B layer when the light absorption axis of the polarizer is 0°.

[0190] *Angle 2: The angle formed by the ground axis of the negative B layer when the light absorption axis of the polarizer is 0°.

[0191]

[0192] As shown in Table 1 above, the polarizing plate of one embodiment exhibited excellent black visibility, thereby providing improved side viewing angles and color. Furthermore, the polarizing plate of one embodiment exhibited a significantly low maximum light transmittance of 0.8% or less in all directions, which is expected to provide excellent light leakage reduction. Furthermore, since the polarizing plate of one embodiment is manufactured by TD stretching the positive B layer and the negative B layer, wide-width manufacturing is possible, thereby enhancing the manufacturing processability and economic feasibility of the polarizing plate.

[0193] 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.

[0194] As shown in FIGS. 5 to 9, the polarizing plate of the example had excellent black visibility and no light leakage. As shown in FIGS. 10 to 17, the polarizing plate of the comparative example had poor black visibility and severe light leakage.

[0195]

[0196] 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 positive B layer and a negative B layer, The positive B layer is located between the polarizer and the negative B layer, The above positive B layer has an in-plane phase difference of 110 to 180 nm and a biaxiality of -1.5 to -0.5 at a wavelength of 550 nm, The above negative B layer has an in-plane phase difference of 40 to 120 nm at a wavelength of 550 nm and a degree of biaxiality of 2.5 to 4.0, A polarizing plate in which the ground axis of the positive B layer is at an angle of -1 to 1° and the ground axis of the negative B layer is at an angle of 89 to 91° with respect to the light absorption axis of the polarizer.

2. A polarizing plate in the first paragraph, wherein the negative B layer has a thickness direction phase difference of 120 to 270 nm at a wavelength of 550 nm.

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

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

5. A polarizing plate in the fourth paragraph, wherein the stretching direction is orthogonal to the light absorption axis direction of the polarizer.

6. 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.

7. A polarizing plate according to claim 6, wherein the negative B layer comprises a cyclic olefin copolymer.

8. A polarizing plate in claim 6, wherein the positive B layer comprises at least one of a cellulose compound or a polymer thereof, an aromatic compound or a polymer thereof.

9. 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 40 to 110 nm at a wavelength of 550 nm.

10. 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 0 to 100 nm at a wavelength of 550 nm.

11. A polarizing plate in the first paragraph, wherein the positive B layer has a thickness direction phase difference of -260 to -120 nm at a wavelength of 550 nm.

12. 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 1.2 to 3.0, 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.) 13. 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.

14. 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.

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

16. An optical display device comprising a polarizing plate according to any one of claims 1 to 15.

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