Polarizing plate and optical display apparatus

Abstract

Provided are a polarizing plate and an optical display apparatus including same, the polarizing plate including: a polarizer; and a phase difference layer stacked on one surface of the polarizer and including a positive C layer and a negative B layer, wherein: the positive C layer is positioned between the polarizer and the negative B layer; a slow axis of the negative B layer is -1° to 1° when a light absorption axis of the polarizer is 0°; the negative B layer has an in-plane phase difference of 70 to 150 nm and a degree of biaxiality of 1.0 to 1.8 at a wavelength of 550 nm; and a laminate of the positive C layer and the negative B layer has a thickness direction phase difference of -52 to 30nm at a wavelength of 550nm.

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 arranged on both sides of the panel. One of the liquid crystal operation modes in LCDs is in-plane switching mode. In-plane switching mode offers the advantage of widening the viewing angle among LCDs. Recently, with the manufacture of large-screen TVs and automotive display devices utilizing in-plane switching mode, there is a growing demand for wider viewing angles. Therefore, there is a need to develop polarizing plates capable of achieving superior viewing angles. Polarizing plates should not only provide superior viewing angles, but also be capable of being produced using roll-to-roll processes, ensuring 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] According to one embodiment, a polarizing plate is provided that provides a side viewing angle and color improvement effect.

[0007] According to one embodiment, a polarizing plate is provided that provides a light leakage improvement effect.

[0008] According to one embodiment, a polarizing plate with excellent economic efficiency and fairness is provided by enabling roll-to-roll manufacturing.

[0009] According to one embodiment, a polarizing plate capable of being thinned is provided.

[0010]

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

[0012] 1. The polarizing plate includes a polarizer; and a phase difference layer laminated on one surface of the polarizer and including a positive C layer and a negative B layer, wherein the positive C layer is positioned between the polarizer and the negative B layer, and when the light absorption axis of the polarizer is 0°, the slow axis of the negative B layer is -1° to 1°, the negative B layer has an in-plane phase difference of 70 to 150 nm and a biaxiality of 1.0 to 1.8 at a wavelength of 550 nm, and a laminate of the positive C layer and the negative B layer has a thickness direction phase difference of -52 to 30 nm at a wavelength of 550 nm.

[0013] In 2.1, the negative B layer may have a thickness direction phase difference of 35 to 195 nm at a wavelength of 550 nm.

[0014] In 3.1-2, the negative B layer may include at least one of a cyclic olefin copolymer and a cellulose ester copolymer.

[0015] In 4.1-3, the negative B layer can be manufactured by a solution casting method.

[0016] In 5.1-4, the negative B layer may include fine particles.

[0017] In 6.1-5, the fine particles may include silicon dioxide.

[0018] In 7.1-6, the laminate of the positive C layer and the negative B layer can have an in-plane phase difference of 70 to 150 nm at a wavelength of 550 nm.

[0019] In 8.1-7, the positive C layer can be formed directly on the negative B layer.

[0020] In 9.1-8, the positive C layer may have a thickness direction phase difference of -150 to -70 nm at a wavelength of 550 nm.

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

[0022] In 11.1-10, the phase difference layer can be laminated on the light incident surface or light exit surface of the polarizer.

[0023] In 12.1-11, the thickness of the laminate of the positive C layer and the negative B layer may be 95% or more of the thickness of the phase difference layer.

[0024] In 13.1-12, a protective layer may be further laminated on one side or the other side of the polarizer.

[0025] In 14.1-13, a first protective layer is laminated on one surface of the polarizer, and the first protective layer can be positioned between the polarizer and the positive C layer.

[0026] In 15.1-14, the first protective layer may have a front-side in-plane phase difference and a thickness-direction phase difference of 10 nm or less at a wavelength of 550 nm.

[0027] According to one embodiment, an optical display device is provided, wherein the optical display device includes the polarizing plate.

[0028]

[0029] According to one embodiment, a polarizing plate is provided that provides a side viewing angle and color improvement effect.

[0030] According to one embodiment, a polarizing plate providing a light leakage improvement effect is provided.

[0031] According to one embodiment, a polarizing plate with excellent economic efficiency and fairness was provided by enabling roll-to-roll manufacturing.

[0032] According to one embodiment, a polarizing plate capable of being thinned is provided.

[0033]

[0034] Figure 1 is a cross-sectional view of a polarizing plate of one embodiment.

[0035] Figure 2 is a cross-sectional view of a polarizing plate of another embodiment.

[0036] Figure 3 is a cross-sectional view of a liquid crystal display device of one embodiment.

[0037] Figure 4 is a cross-sectional view of a liquid crystal display device of another embodiment.

[0038]

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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:

[0044] [Formula A]

[0045] Re = (nx - ny) xd

[0046] [Formula B]

[0047] Rth = ((nx + ny) / 2 - nz) xd

[0048] [Formula C]

[0049] NZ = (nx - nz) / (nx - ny)

[0050] (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).)

[0051] 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 the present invention is not limited thereto.

[0052] 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.

[0053] 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 0.5% or less, for example, 0 to 0.5%, and the light leakage improvement effect may be excellent within 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.

[0054] According to one implementation example, a polarizing plate with excellent economic efficiency was provided by enabling roll-to-roll manufacturing.

[0055] According to one implementation example, a polarizing plate with excellent thickness reduction was provided.

[0056] 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 C layer and a negative B layer, wherein the positive C layer is positioned between the polarizer and the negative B layer, and when the light absorption axis of the polarizer is 0°, a slow axis of the negative B layer is -1° to 1°, the negative B layer has an in-plane retardation of 70 to 150 nm and a degree of biaxiality of 1.0 to 1.8 at a wavelength of 550 nm, and a laminate of the positive C layer and the negative B layer has a thickness direction retardation of -52 to 30 nm at a wavelength of 550 nm.

[0057] The above positive C layer and negative B layer are adjacent to each other, and a laminate of the positive C layer and the negative B layer can be positioned within a polarizing plate on the viewer side or a polarizing plate on the light source side. The position of the laminate should be at a location where the light absorption axis of the polarizer in the polarizing plate and the alignment direction of the driving liquid crystal within the IPS panel are orthogonal.

[0058] 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°, and the absorption axis of the polarizer in the viewer-side polarizing plate is 0° and the absorption axis of the polarizer in the light source-side polarizing plate is 90°, a stack of positive C layers and negative B layers is positioned on the viewer-side polarizing plate and is stacked in the following order from the viewer side: the viewer-side polarizer, the positive C layer, the negative B layer, the IPS panel, and the light source-side polarizer. A person of ordinary skill in the art will refer to this as an O-mode structure. In this case, the positive C layer and the negative B layer may be stacked on the light incident surface of the viewer-side polarizer.

[0059] 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°, and the absorption axis of the polarizer in the viewer-side polarizer is 0° and the absorption axis of the polarizer in the light source-side polarizer is 90°, the stack of the positive C layer and the negative B layer is positioned on the light source-side polarizer and is stacked in the order of the light source-side polarizer, the positive C layer, the negative B layer, the IPS panel, and the viewer-side polarizer from the light source side. A person of ordinary skill in the art will refer to this as an E-mode structure. In this case, the positive C layer and the negative B layer may be stacked on the light-emitting surface of the light source-side polarizer.

[0060] However, in the above specific example, the laminate of the positive C 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.

[0061] Below, each component of the polarizing plate is described in detail.

[0062] Positive C layer

[0063] The positive C layer is positioned between the polarizer and the negative B layer in the polarizing plate. By being positioned at this position, the positive C layer can easily improve the viewing angle and color from the side and improve light leakage. A polarizing plate laminated in this order from the polarizer to the negative B layer and the positive C layer may not properly achieve the side viewing angle and color improvement effect compared to the polarizing plate according to one embodiment, or the effect may be weak.

[0064] The positive C layer may have a thickness direction retardation of -150 to -70 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 C layer may have a thickness direction retardation of -150, -145, -140, -135, -130, -125, -120, -115, -110, -105, -100, -95, -90, -85, -80, -75, -70 nm at a wavelength of 550 nm, preferably -140 to -80 nm, more preferably -130 to -80 nm.

[0065] The positive C layer may have an in-plane retardation of 0 to 10 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 as described below. For example, the positive C layer may have an in-plane retardation of preferably 0 to 5 nm, more preferably 0 to 3 nm, at a wavelength of 550 nm.

[0066] The positive C layer can be formed of a material that satisfies nz>nx=ny (nx, ny, nz are refractive indices in the slow axis direction, the fast axis direction, and the thickness direction at a wavelength of 550 nm) as a material of a non-liquid crystal layer and can implement the above-described in-plane phase difference and thickness direction phase difference.

[0067] In one specific embodiment, the positive C layer may be a stretched film. For example, the positive C layer may be a stretched film comprising one or more resins selected from the group consisting of cellulose-based; polyester-based including polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, etc.; cyclic polyolefin (COP)-based; polycarbonate-based; polyethersulfone-based; polysulfone-based; polyamide-based; polyimide-based; polyolefin-based; polyarylate-based; polyvinyl alcohol-based; polyvinyl chloride-based; polyvinylidene chloride-based; acrylic-based; and polystyrene-based.

[0068] In another specific example, the positive C layer may be a coating layer formed of a composition containing at least one of a cellulose-based compound or a polymer thereof, an aromatic compound or a polymer thereof for the positive C layer. In this case, the positive C layer may be formed by coating the composition on one surface of the negative B layer to a predetermined thickness and then curing it without stretching (the positive C layer is a non-stretching layer). In this case, the positive C layer is directly formed on the negative B layer. The term "directly formed" means that no adhesive layer, bonding layer, or adhesive layer is formed between the positive C layer and the negative B layer. In the case of "directly formed," the thickness of the entire phase difference layer may be thinned, thereby providing an effect of thinning the thickness of the polarizing plate.

[0069] In another specific embodiment, the positive C layer can be formed by coating the composition for the positive C layer on one side of the base film to a predetermined thickness and then curing it. In this case, the positive C layer can be transferred to the negative B layer to form a laminate of the negative B layer and the positive C layer. Although not particularly limited, in the laminate, the positive C layer can be laminated to the negative B layer by an adhesive layer or an adhesive layer. This can provide the same optical properties as the laminate of the negative B layer and the positive C layer according to the other specific embodiment, but the thickness of the laminate tends to increase somewhat due to the adhesive layer or the adhesive layer. However, even if this is done, it does not depart from the scope of the present invention.

[0070] The above cellulose compound may include at least a unit in which at least some of the hydrogen atoms of the hydroxyl groups [C2 hydroxyl group, C3 hydroxyl group, or C6 hydroxyl group] of the sugar monomer forming the cellulose are substituted with an acyl group or an ether group. That is, the cellulose compound may include at least one of a cellulose ester compound and a cellulose ether compound.

[0071] For example, the cellulose-based compound may include a cellulose ester-based compound including at least a unit in which at least some of the hydrogen atoms of the hydroxyl groups [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.

[0072] [Chemical Formula 1]

[0073]

[0074] (In the above chemical formula 1, n is an integer greater than or equal to 1)

[0075] The substituent for the cellulose ester system or the substituent for the 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), alkynyl (e.g., an alkynyl 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.

[0076] The above "acyl" may 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" may be bonded to the ring of cellulose through an ester bond (via an oxygen atom) at a hydroxyl group of a sugar monomer forming cellulose.

[0077] The above "alkyl", "alkenyl", "cycloalkyl", "aryl", "heteroaryl", "alkoxy", and "acyl" are each non-halogen compounds that do not contain halogen for convenience. The composition for a positive C phase difference layer may contain the above cellulose ester compound alone or a mixture of two or more of the above cellulose ester compounds.

[0078] The above “halogen” may mean fluorine (F), Cl, Br or I, and preferably may mean F.

[0079] 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.

[0080] The above "halogen-substituted acyl group" can 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" is bonded to the ring of cellulose through an ester bond (via an oxygen atom) at a hydroxyl group of a sugar monomer forming cellulose.

[0081] 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 C 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., a carboxylic acid anhydride or a carboxylic acid), or by reacting trifluoroacetic acid or trifluoroacetic anhydride and an acylating agent together.

[0082] The aromatic compound contains a phenyl group and may include, but is not limited to, a polystyrene-based compound, a fluorobenzene-based compound, or a difluorostyrene-based compound. In one specific example, the polystyrene-based compound may contain a moiety represented by the following chemical formula 2:

[0083] [Chemical Formula 2]

[0084]

[0085] (In the above chemical formula 2, is the connecting part of the silver element,

[0086] R 1 , R 2 , R 3 are each independently a hydrogen atom, an alkyl group, a substituted alkyl group, or a halogen,

[0087] R is each independently a substituent on the styrene ring,

[0088] n represents the number of substituents on the styrene ring and is an integer from 0 to 5.

[0089] 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.

[0090] In one specific example, R 1 , R 2 , R 3 One or more of the above may be a halogen, more preferably fluorine.

[0091] The composition for the positive C 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 C layer in an amount of 0.1 to 30 wt%, preferably 1 to 10 wt%. Within the above range, the additive has the effect of controlling the phase difference expression rate and wavelength dispersion.

[0092] The positive C layer may have a thickness of 1 to 60 μm, preferably 1 to 30 μm, and more preferably 1 to 10 μm. Within the above range, it can be applied to a polarizing plate, can facilitate the implementation of the phase difference of the present invention, and can facilitate the thinning of the polarizing plate.

[0093] Negative B layer

[0094] 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).

[0095] The negative B layer can be a stretched film as described below. The negative B layer has a slow axis and a fast axis in the in-plane direction. At this time, 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 the above range, it can be easy to provide a viewing angle and color improvement effect and a light leakage improvement effect from the side. For example, when the light absorption axis of the polarizer is 0°, the slow axis of the negative B layer can form -0.5° to 0.5°, 0°.

[0096] According to one embodiment, the ground axis of the negative B layer may be substantially parallel to the mechanical direction of the negative B layer, and the forward axis of the negative B layer may be substantially parallel to the width direction of the negative B layer. This may facilitate the manufacture of a polarizing plate by roll-to-roll.

[0097] The negative B layer has an in-plane retardation of 70 to 150 nm at a wavelength of 550 nm and a degree of biaxiality of 1.0 to 1.8. When the above-described in-plane retardation and degree of biaxiality ranges are simultaneously satisfied, it can be easily improved in terms of viewing angle and color and light leakage when laminated on one side of the above-described positive C layer. A polarizing plate including a negative B layer that does not satisfy either of the above-described in-plane retardation and degree of biaxiality ranges may have a weak improvement in viewing angle and color when laminated on the one side.

[0098] For example, the negative B layer can have an in-plane retardation of 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150 nm, preferably an in-plane retardation of 70 to 130 nm, more preferably 80 to 120 nm. For example, the negative B layer can have a degree of biaxiality of, for example, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, preferably 1.0 to 1.6, more preferably 1.1 to 1.6, 1.1 to 1.5.

[0099] The negative B layer can have a thickness-wise retardation of 35 to 195 nm at a wavelength of 550 nm. In this range, the above-described in-plane retardation and degree of biaxiality can be easily achieved. For example, the negative B layer may have a thickness direction phase difference of 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195 nm, preferably 35 to 143 nm, more preferably 40 to 120 nm, 48 to 120 nm.

[0100] The negative B layer may be made of any material as long as it satisfies the above-described refractive index relationship, in-plane retardation, and degree of biaxiality. However, the present invention specifically uses a negative B layer manufactured by processing a composition for a negative B layer by a solution casting method to manufacture an unstretched film, and then uniaxially stretching the manufactured unstretched film in the MD of the unstretched film. Generally, film manufacturing methods are classified into two types: melt extrusion and solution casting. Melt extrusion is a method of manufacturing an unstretched film by heating a polymer to a molten state and extruding it through an extrusion device. Therefore, it has good productivity with relatively low equipment cost. On the other hand, melt extrusion is a method in which thin lines (so-called die lines) are formed on the film because the film thickness is not precisely controlled. Therefore, melt extrusion is not suitable for high-quality films such as optically functional films. On the other hand, solution casting has the advantage of providing better optical isotropy and thickness uniformity than melt extrusion, and producing a film with less foreign matter. Therefore, the solution casting method can be used to easily manufacture an optical functional film.

[0101] In general, the solution casting method comprises dissolving a polymer in a mixed solvent (e.g., a solvent composed of dichloromethane or methyl acetate) to prepare a dope material, mixing a predetermined additive into the dope material to prepare a casting dope, supplying the prepared casting dope to a casting die and discharging it from a discharging slit onto a casting drum, an endless band, or a continuously moving support, and the discharged dope forms beads between the discharging slit and the support to produce a casting film on the support. The casting film is returned to the support at a constant speed and cooled or dried to have self-supporting properties. The casting film can be separated from the support to form a wet film, then dried and wound up, thereby producing a final film.

[0102] The above dope material includes 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 cycloolefin copolymer (COC); a cellulose ester copolymer including cellulose acylate, cellulose butyrate, cellulose propionate, cellulose acetate propionate, cellulose acetate butyrate, etc. Preferably, the cycloolefin copolymer can be used to manufacture an unstretched film having a relatively thin thickness by a solution casting method.

[0103] Cyclic olefin copolymers are polymers having a cyclic olefin structure. Cyclic olefin copolymers can be norbornene polymers, monocyclic olefin polymers, cyclic conjugated diene polymers, vinyl alicyclic hydrocarbon polymers, or hydrides of any of these.

[0104] The above dope material may include 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, or esters thereof having 3 to 12 carbon atoms, ketones thereof, and / or ether compounds thereof. The esters, ketones, and ethers may have a cyclic structure.

[0105] Chain hydrocarbons having 3 to 12 carbon atoms can be hexane, octane, isooctane, and decane. Cyclic hydrocarbons having 3 to 12 carbon atoms can be cyclopentane, cyclohexane, and their derivatives. Aromatic hydrocarbons having 3 to 12 carbon atoms can be benzene, toluene, and xylene. Esters having 3 to 12 carbon atoms can be ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate, and pentyl acetate. Ketones having 3 to 12 carbon atoms can 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 be exemplified by 2-ethoxyethyl acetate, 2-methoxyethanol, and 2-butoxyethanol. The boiling point of the organic solvent may preferably be 35 to 150°C.

[0106] Additionally, the solvent may be a mixture of two or more solvents to control the drying properties, viscosity, and other properties of the dope. In this case, the solvent may additionally contain an antisolvent.

[0107] 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 a dope of a cyclic olefin copolymer system is one in which the main component is dichloromethane, and the antisolvent is preferably at least one of methanol, ethanol, propanol, isopropanol, and butanol.

[0108] In the solution casting method, it is possible to mix additives into the dope material prior to dispensing. These 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.

[0109] The 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 when handling the film. As a result, the fine particles can prevent the entire positive C layer and the entire negative B layer from being broken when the entire positive C layer and the entire negative B layer are rolled and then unrolled. In particular, the fine particles can improve the manufacturing process of the polarizing plate and enable economic production by eliminating the need to additionally laminate a protective film over the entire positive C layer and the entire negative B layer and then roll-to-roll them.

[0110] The above fine particles are not limited, but may be fine particles of either an inorganic compound or an organic compound.

[0111] The above 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 turbidity removal effect of the film.

[0112] The organic compound may be polytetrafluoroethylene, cellulose acetate, polystyrene, polymethyl methacrylate, polypropyl methacrylate, polymethyl methacrylate, polyethylene carbonate, and starch.

[0113] The primary average diameter of the above-mentioned 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-mentioned "primary average diameter" can be calculated from the average size of the particles measured using a transmission electron microscope.

[0114] The above 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.

[0115] The unstretched film manufactured by the above solution casting method can be manufactured into a negative B layer by uniaxially stretching the MD of the unstretched film.

[0116] The negative B layer may further include a primer layer formed on at least one surface. The primer layer can facilitate adhesion of the positive C layer to one surface of the negative B layer. The primer layer is not particularly limited in material thickness, etc., as long as it does not affect the phase difference of the negative B layer or the positive C layer. For example, the primer layer may be made of polyester, acrylic, or urethane.

[0117] The negative B layer may have a thickness of 20 to 80 μm, preferably 25 to 70 μm, and more preferably 30 to 60 μm. In the above range, it can be used in a polarizing plate.

[0118] A laminate of a positive C layer and a negative B layer

[0119] The laminate of the positive C layer and the negative B layer can have an in-plane retardation of 70 to 150 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, for example, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150 nm at a wavelength of 550 nm, preferably 70 to 130 nm, more preferably 80 to 120 nm.

[0120] The laminate of the positive C layer and the negative B layer has a thickness direction retardation of -52 to 30 nm at a wavelength of 550 nm. If the thickness direction retardation of the laminate is less than -52 nm, black visibility is reduced, the light leakage improvement effect is weak, and purple or yellow is recognized when evaluating color, so the color improvement effect may not be good. If the thickness direction retardation of the laminate is more than 30 nm, black visibility is reduced, the light leakage improvement effect is weak, and purple or yellow is recognized when evaluating color, so the color improvement effect may not be good. For example, the laminate may have a thickness direction retardation of -52, -50, -45, -40, -35, -30, -25, -20, -15, -10, -5, 0, 5, 10, 15, 20, 25, 30 nm at a wavelength of 550 nm, for example, the laminate may have a thickness direction retardation of preferably -50 to 20 nm, more preferably -40 to 10 nm, and most preferably -30 to 0 nm, -30 to -5 nm, or -30 to -10 nm at a wavelength of 550 nm.

[0121] The thickness of the laminate of the positive C 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.

[0122] polarizer

[0123] 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.

[0124] 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.

[0125] 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.

[0126] 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.

[0127] The polarizer may be laminated directly onto the negative C layer without an adhesive layer or adhesive layer, or may be laminated onto the negative C layer by an adhesive layer or adhesive layer, as described below.

[0128] In the above range, the thinning effect of the polarizing plate can be implemented.

[0129] The polarizing plate may further include a protective layer on one or the other side of the polarizer.

[0130] First protective layer

[0131] 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.

[0132] 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.

[0133] In one embodiment, the first protective layer may be positioned between the polarizer and the positive C layer.

[0134] 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.

[0135] 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.

[0136] Second protective layer

[0137] 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.

[0138] 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 (PET), polybutylene terephthalate, polyethylene naphthalate (PEN), 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.

[0139] 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.

[0140] 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.

[0141] Figures 1 and 2 are cross-sectional views of a polarizing plate of the present invention.

[0142] Referring to FIG. 1, the polarizing plate may include a polarizer (30); a positive C 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).

[0143] Referring to FIG. 2, the polarizing plate may include a polarizer (30); a positive C 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).

[0144] 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 C layer.

[0145] The optical display device of the present invention includes a polarizing plate of an embodiment of the present invention. The optical display device may include a liquid crystal display device.

[0146] 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.

[0147] 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.

[0148] 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 C layer (10), and a polarizer (30) sequentially laminated from the liquid crystal panel (100).

[0149] 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.

[0150] 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 C layer (10), and a polarizer (30) sequentially laminated from the liquid crystal panel (100).

[0151] 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.

[0152]

[0153] 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.

[0154]

[0155] Example 1

[0156] A polyvinyl alcohol film (PS#60, Kuraray, Japan, thickness before stretching: 60 ㎛) was stretched 6 times along the MD (machine direction) axis of the polyvinyl alcohol film in an iodine aqueous solution at 55°C to produce a polarizer with a single-light transmittance of 43%.

[0157] A composition containing a cyclic olefin copolymer (COC) was cast by a solution casting method to produce an unstretched film, and the unstretched film was stretched uniaxially in the MD at a predetermined stretching ratio to produce a negative B layer having a composition shown in Table 1 below.

[0158] A cellulose ester composition (VM500, Eastman, USA) was applied to one side of the negative B layer to a predetermined thickness and cured (without stretching), thereby manufacturing a laminate of a negative B layer and a positive C layer having a positive C layer having a composition shown in Table 1 below on one side of the negative B layer. The positive C layer has Rth = -110 nm, Re = 0 nm, and thickness = 4.6 ㎛ at a wavelength of 550 nm.

[0159] The laminate was laminated on one side of the polarizer, and the positive C layer was laminated as an adhesive layer on one side of the polarizer. A PET film was laminated as an adhesive layer as a protective layer on the other side of the polarizer, thereby manufacturing a polarizing plate laminated in the order of PET film - polarizer - positive C layer - negative B layer.

[0160]

[0161] Examples 2 to 4

[0162] 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 solution casting process were changed, and the phase difference of the positive C layer was changed.

[0163]

[0164] Comparative Examples 1 to 4

[0165] 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 solution casting process were changed, and the phase difference of the positive C layer was changed.

[0166]

[0167] Comparative Example 5

[0168] In Example 1, a polarizing plate was manufactured in the same manner as in Example 1, except that the order of the negative B layer and the positive C layer was changed and the layers were laminated in the order of PET film - polarizer - negative B layer - positive C layer.

[0169]

[0170] The Re, Rth, and NZ of each phase difference layer are values ​​obtained at a wavelength of 550 nm using AXOSCAN.

[0171] The properties below were evaluated using the polarizing plates of the examples and comparative examples and are shown in Table 1 below.

[0172] (1) Maximum light transmittance in all directions: In a Samsung Electronics TV model equipped with an IPS liquid crystal panel, the polarizer manufactured in the examples and comparative examples was attached and operated instead of the polarizer on the viewer side. Then, the maximum light transmittance in the black state over 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.

[0173] (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 (BOE, China) and visibility was evaluated. Black visibility and color were evaluated by visual inspection.

[0174]

[0175] Example Comparative Example 123412345 Negative B layer Re (nm) 100 110 120 90 120 90 70 150 100 Rth (nm) 90 77 72 117 60 117 35 135 90 NZ 1.4 1.2 1.1 1.8 1.0 1.8 1.2 1.4 1.4 Positive C layer Rth (nm) -110 - 90 - 80 - 120 - 150 - 70 - 90 - 80 - 110 Laminate of negative B layer and positive C layer Re (nm) 100 110 120 90 120 90 70 150 100 Rth (nm) -20 - 13 - 8 - 3 - 90 47 - 55 5 - 20 Angle (°) 0 ... Transmittance (%) 0.26 0.27 0.27 0.31 1.27 1.28 1.07 1.25 4.42 Voltage not applied Visibility evaluation result Black feeling Excellent Black feeling Excellent Black feeling Excellent Black feeling Excellent Black feeling Low (purple visible) Black feeling Low (yellow visible) Black feeling Low (yellow visible) Black feeling Low (purple visible) Black feeling significantly low (colorless)

[0176]

[0177] *Angle in Table 1: The angle formed by the ground axis of the negative B layer when the light absorption axis of the polarizer is 0°.

[0178]

[0179] As shown in Table 1 above, the polarizing plate of the present invention is expected to sufficiently provide a light leakage improvement effect due to its significantly low maximum light transmittance in all directions. The polarizing plate of the present invention is expected to provide an excellent black visibility, thereby improving the side viewing angle and color.

[0180] On the other hand, even if the phase difference of the positive C layer and the negative B layer of the present invention is satisfied, the polarizing plate of Comparative Example 5, in which the negative B layer and the positive C layer are laminated in the order from the polarizer, has a significantly low black luminance and an all-directional maximum light transmittance that is too high, making it difficult to use. Even if the positive C layer and the negative B layer of the present invention are provided, the polarizing plates of Comparative Examples 1 to 4, in which the Rth of the laminate of the positive C layer and the negative B layer at a wavelength of 550 nm is outside the range of the present invention, also have a low black luminance and an all-directional maximum light transmittance that is higher than that of the embodiment, so the light leakage improvement effect is not good.

[0181]

[0182] 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 C layer and a negative B layer, The positive C layer is located between the polarizer and the negative B layer, When the optical absorption axis of the above polarizer is 0°, the ground axis of the negative B layer is -1° to 1°, The above negative B layer has an in-plane phase difference of 70 to 150 nm and a biaxiality of 1.0 to 1.8 at a wavelength of 550 nm, A polarizing plate in which the laminate of the positive C layer and the negative B layer has a thickness direction phase difference of -52 to 30 nm at a wavelength of 550 nm.

2. A polarizing plate in the first paragraph, wherein the negative B layer has a thickness direction phase difference of 35 to 195 nm at a wavelength of 550 nm.

3. A polarizing plate according to claim 1, wherein the negative B layer comprises at least one of a cyclic olefin copolymer and a cellulose ester copolymer.

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

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

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

7. A polarizing plate in accordance with claim 1, wherein the laminate of the positive C layer and the negative B layer has an in-plane phase difference of 70 to 150 nm at a wavelength of 550 nm.

8. A polarizing plate according to claim 1, wherein the positive C layer is formed directly on the negative B layer.

9. A polarizing plate in the first paragraph, wherein the positive C layer has a thickness direction phase difference of -150 to -70 nm at a wavelength of 550 nm.

10. A polarizing plate according to claim 1, wherein the positive C layer is a coating layer comprising 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 phase difference layer is laminated on the light incident surface or light exit surface of the polarizer.

12. A polarizing plate in accordance with claim 1, wherein the thickness of the laminate of the positive C layer and the negative B layer is 95% or more of the thickness of the phase difference layer.

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

14. In the first paragraph, a first protective layer is laminated on one surface of the polarizer, A polarizing plate, wherein the first protective layer is positioned between the polarizer and the positive C layer.

15. A polarizing plate in claim 14, wherein the first protective layer has a front-side in-plane phase difference and a thickness direction phase difference of 10 nm or less at a wavelength of 550 nm.

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

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