Polarizing plates and optical display devices

Abstract

The present invention relates to a polarizing plate and an optical display device equipped therewith. The polarizing plate comprises a polarizer and a phase difference layer including a positive C layer and a negative B layer laminated on one surface of the polarizer, wherein the positive C layer is located between the polarizer and the negative B layer; 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 at a wavelength of 550 nm and a degree of biaxiality of 1.0 to 1.8; and 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.

Description

Technical Field

[0001] The present invention relates to a polarizing plate and an optical display device.

Background Art

[0002] A liquid crystal display device includes a liquid crystal panel and polarizing plates disposed on both surfaces of the liquid crystal panel. As one of the liquid crystal driving methods of a liquid crystal display device, there is an in-plane switching method. The in-plane switching method has an advantage that the wide viewing angle of the liquid crystal display device can be widened. In recent years, with the manufacture of image display devices such as large TVs and in-vehicle displays employing the in-plane switching method, wider viewing angle characteristics have been required. Therefore, development of a polarizing plate for securing an excellent viewing angle has been needed. The polarizing plate needs to provide an excellent viewing angle and ensure economic efficiency and manufacturability by being manufacturable by a roll-to-roll method.

[0003] The background art of the present invention is disclosed in Korean Patent No. 10-2013-0103595 and the like.

Summary of the Invention

Problems to be Solved by the Invention

[0004] According to one specific example, a polarizing plate that provides a side viewing angle and a color perception improvement effect is provided.

[0005] According to one specific example, a polarizing plate that provides a light leakage improvement effect is provided.

[0006] According to one specific example, a polarizing plate excellent in economic efficiency and workability is provided by being manufacturable by roll-to-roll.

[0007] According to one specific example, a polarizing plate with a reduced thickness is provided.

Means for Solving the Problems

[0008] In one specific example, a polarizing plate is provided.

[0009] 1. The polarizing plate comprises a polarizer and a phase difference layer laminated on one surface of the polarizer, the phase difference layer comprising a positive C layer and a negative B layer, wherein the positive C layer is located between the polarizer and the negative B layer; 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 at a wavelength of 550 nm and a degree of biaxiality of 1.0 to 1.8; and 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.

[0010] In 2.1, the negative B layer may have a phase difference in the thickness direction of 35 to 195 nm at a wavelength of 550 nm.

[0011] In sections 3.1-2, the negative B layer may include one or more selected from the group consisting of cyclic olefin copolymers and cellulose ester copolymers.

[0012] In sections 4.1 to 4.3, the negative B layer may be manufactured by a solution casting method.

[0013] In sections 5.1 to 5.4, the negative B layer may contain fine particles.

[0014] In sections 6.1 to 6.5, the fine particles may contain silicon dioxide.

[0015] In sections 7.1 to 7.6, the laminate of the positive C layer and the negative B layer may have an in-plane phase difference of 70 to 150 nm at a wavelength of 550 nm.

[0016] In sections 8.1 to 8.7, the positive C layer may be formed directly on the negative B layer.

[0017] 9. In 1 to 8, the positive C layer may have a thickness-direction retardation of -150 to -70 nm at a wavelength of 550 nm.

[0018] 10. In 1 to 9, the positive C layer may be a coating layer containing one or more selected from the group consisting of a cellulose-based compound or its polymer, an aromatic compound or its polymer.

[0019] 11. In 1 to 10, the retardation layer may be laminated on the light incident surface or the light exit surface of the polarizing plate.

[0020] 12. In 1 to 11, the laminate of the positive C layer and the negative B layer may have a thickness of 95% or more of the thickness of the retardation layer.

[0021] 13. In 1 to 12, a protective layer may be further laminated on one or the other surface of the polarizing plate.

[0022] 14. In 1 to 13, a first protective layer is laminated on one surface of the polarizing plate, and the first protective layer may be located between the polarizing plate and the positive C layer.

[0023] 15. In 1 to 14, the first protective layer may have an in-plane retardation and a thickness-direction retardation of 10 nm or less each at a wavelength of 550 nm.

[0024] According to one specific example, an optical display device including the polarizing plate is provided.

Advantages of the Invention

[0025] According to one specific example, a polarizing plate providing a side viewing angle and color perception improvement effect is provided.

[0026] According to one specific example, a polarizing plate providing a light leakage improvement effect is provided.

[0027] In one specific example, a polarizing plate that is economical and easy to process can be provided by enabling roll-to-roll manufacturing.

[0028] In one specific example, a polarizing plate that can be made thinner is provided. [Brief explanation of the drawing]

[0029] [Figure 1] This is a cross-sectional view of a polarizing plate, showing one specific example. [Figure 2] This is a cross-sectional view of a polarizing plate, using another specific example. [Figure 3] This is a cross-sectional view of a liquid crystal display device, showing one specific example. [Figure 4] This is a cross-sectional view of a liquid crystal display device, using another specific example. [Modes for carrying out the invention]

[0030] The present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily implement it according to the examples. The present invention can be implemented in various forms and is not limited to the examples described herein.

[0031] The terms used herein are for illustrative purposes only and are not intended to limit the invention. Singular expressions include plural expressions unless otherwise specified in the context.

[0032] In the drawings, irrelevant parts have been omitted in order to clearly illustrate the present invention, and the same or similar components are referred to by the same names throughout this specification. In the drawings, the lengths and dimensions of each component are used to illustrate the present invention, but the present invention is not limited to the lengths and dimensions of the components shown in the drawings.

[0033] In this specification, "upper" and "lower" are defined based on the drawings, and depending on the viewing angle, "upper" may become "lower" and "lower" may become "upper."

[0034] In this specification, "in-plane phase difference (Re)" is expressed by the following formula A, "thickness phase difference (Rth)" is expressed by the following formula B, and "degree of biaxiality (NZ)" is expressed by the following formula C.

[0035]

number

number

number

[0036] In this specification, unless otherwise specified, nx, ny, and nz refer to the slow axis, fast axis, and refractive index in 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 actually be orthogonal, but the present invention is not limited thereto.

[0037] In one specific example, a polarizing plate is provided that offers improved lateral field of view and color perception. This allows the polarizing plate to provide superior black perception.

[0038] One specific example provides a polarizing plate that improves light leakage by reducing the maximum transmittance in all directions. For example, the maximum transmittance in all directions may be 0.5% or less, or even 0 to 0.5%. Within this range, the light leakage improvement effect is considered to be excellent. The above "transmittance" refers to the degree of light leakage at different viewing angles when the display shows black, with the backlight at 100%, and is a value that reflects the tristimulus values ​​of the human eye. The lower the transmittance, the better the viewing angle characteristics.

[0039] In one specific example, it is possible to provide an economically efficient polarizing plate that can be manufactured using a roll-to-roll process.

[0040] One specific example provides a polarizing plate that excels in reducing thickness.

[0041] In one specific example, the polarizing plate comprises a polarizer and a phase difference layer laminated on one surface of the polarizer, the phase difference layer including a positive C layer and a negative B layer, wherein the positive C layer is located between the polarizer and the negative B layer; 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 at a wavelength of 550 nm and a degree of biaxiality of 1.0 to 1.8; and 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.

[0042] In one specific example, the positive C layer and the negative B layer are adjacent to each other, and the laminate of the positive C layer and the negative B layer can be located within the observation-side polarizer or the light source-side polarizer. The location of the laminate must be such that the light absorption axis of the polarizer in the polarizer and the orientation direction of the driving liquid crystal in the IPS panel are perpendicular to each other.

[0043] In one specific example, when no voltage is applied to the IPS panel, the orientation direction (i.e., rubbing direction) of the driving liquid crystal within the IPS panel is 90°, the absorption axis of the polarizer on the observation-side polarizer is 0°, the absorption axis of the polarizer on the light source-side polarizer is 90°, the laminate of the positive C layer and the negative B layer is located on the observation-side polarizer, and the layers are stacked in the order of observation-side polarizer, positive C layer, negative B layer, IPS panel, and light source-side polarizer from the observation side. This is called an O-mode structure by those skilled in the art. In such a structure, the positive C layer and the negative B layer may be stacked on the light incident surface of the observation-side polarizer.

[0044] In another specific example, when no voltage is applied to the IPS panel, the orientation direction (i.e., rubbing direction) of the driving liquid crystal in the IPS panel is 0°, the absorption axis of the polarizer on the observation-side polarizer is 0°, the absorption axis of the polarizer on the light source-side polarizer is 90°, the laminate of the positive C layer and the negative B layer is located on the light source-side polarizer, and the layers are stacked in the order of light source-side polarizer, positive C layer, negative B layer, IPS panel, and observation-side polarizer from the light source side. This is called an E-mode structure by those skilled in the art. In such a structure, the positive C layer and the negative B layer may be stacked on the light emission surface of the light source-side polarizer.

[0045] However, in the above specific example, the laminate of the positive C layer and the negative B layer must not be located simultaneously on the observation-side polarizer and the light source-side polarizer.

[0046] The following provides a detailed explanation of each component of the polarizing plate. Positive C layer

[0047] The positive C layer is located between the polarizer and the negative B layer in the polarizing plate. By placing the positive C layer in the above position, it is possible to easily improve the lateral viewing angle and color tone, as well as reduce light leakage. Compared to a polarizing plate according to one embodiment, in a polarizing plate in which the polarizer, negative B layer, and positive C layer are laminated in that order, the improvement in lateral viewing angle and color tone may not be sufficient, or the above effects may be insufficient.

[0048] The positive C layer may have a thickness-direction phase difference of -150 to -70 nm at a wavelength of 550 nm. Within this range, when the negative B layer described later is laminated, it is possible to easily improve the lateral viewing angle and light leakage. For example, the positive C layer may have a thickness-direction phase difference of -150, -145, -140, -135, -130, -125, -120, -115, -110, -105, -100, -95, -90, -85, -80, -75, or -70 nm at a wavelength of 550 nm, preferably -140 to -80 nm, and more preferably -130 to -80 nm.

[0049] The positive C layer may have an in-plane phase difference of 0 to 10 nm at a wavelength of 550 nm. Within this range, when the negative B layer described later is laminated, it is possible to easily improve the lateral viewing angle and light leakage. For example, the in-plane phase difference of the positive C layer at a wavelength of 550 nm may preferably be 0 to 5 nm, more preferably 0 to 3 nm.

[0050] The positive C layer may be formed from a non-liquid crystal layer material that satisfies the relationship nz>nx=ny at a wavelength of 550 nm (where nx, ny, and nz are the refractive indices in the slow phase axis direction, fast phase axis direction, and thickness direction at a wavelength of 550 nm, respectively), and that is capable of realizing the in-plane phase difference and thickness-direction phase difference described above.

[0051] In one specific example, the positive C layer may be a stretched film. For example, the positive C layer may be a stretched film containing 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.

[0052] In another specific example, the positive C layer may be a coating layer formed from a composition for the positive C layer comprising one or more compounds selected from the group consisting of cellulose compounds or polymers thereof, and aromatic compounds or polymers thereof. In this case, the positive C layer may be formed by applying the composition to one surface of the negative B layer to a predetermined thickness and then curing it without stretching (the positive C layer is an unstretched layer). In this case, the positive C layer is formed directly on the negative B layer. The term "direct formation" means that no adhesive layer, bonding layer, or visco-adhesive layer is formed between the positive C layer and the negative B layer. In the case of "direct formation," the overall thickness of the phase difference layer can be reduced, thus providing the effect of reducing the thickness of the polarizing plate.

[0053] In another specific example, the positive C layer may be formed by applying the positive C layer composition to one surface of a substrate film to a predetermined thickness and then curing it. In this case, the positive C layer may 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 above laminate, the positive C layer is laminated on the negative B layer via an adhesive or bonding layer. This provides the same optical properties as the laminate of the negative B layer and the positive C layer in the other specific example, but the thickness of the above laminate tends to increase slightly due to the presence of the adhesive or bonding layer. Nevertheless, this structure does not depart from the scope of the present invention.

[0054] The above-mentioned cellulosic compounds may contain at least units in which at least some of the hydrogen atoms of the hydroxyl groups [C2 hydroxyl groups, C3 hydroxyl groups, or C6 hydroxyl groups] of the sugar monomers constituting cellulose are substituted with acyl groups or ether groups. In other words, the cellulosic compounds may contain one or more of the cellulose ester compounds and cellulose ether compounds.

[0055] For example, cellulosic compounds may include cellulose ester compounds that contain at least one unit in which at least some of the hydrogen atoms of the hydroxyl group [C2 hydroxyl group, C3 hydroxyl group, or C6 hydroxyl group] of the sugar monomer constituting cellulose are substituted with an acyl group, as represented by the following chemical formula 1. In this case, the acyl group may be substituted or unsubstituted.

[0056] [ka] (In the above formula 1, n is an integer greater than or equal to 1.)

[0057] The substituents used in cellulose ester systems or acyl groups may each include one or more selected from the group consisting of halogens, nitro groups, alkyl groups (e.g., alkyl groups having 1 to 20 carbon atoms), alkenyl groups (e.g., alkenyl groups having 2 to 20 carbon atoms), alkynyl groups (e.g., alkynyl groups having 2 to 20 carbon atoms), cycloalkyl groups (e.g., cycloalkyl groups having 3 to 10 carbon atoms), aryl groups (e.g., aryl groups having 6 to 20 carbon atoms), heteroaryl groups (e.g., heteroaryl groups having 3 to 10 carbon atoms), alkoxy groups (e.g., alkoxy groups having 1 to 20 carbon atoms), acyl groups, and halogen-containing functional groups. The substituents may be the same or different.

[0058] As is known to those skilled in the art, the above-mentioned "acyl group" is

number

[0059] For the sake of explanation, the above-mentioned "alkyl group," "alkenyl group," "cycloalkyl group," "aryl group," "heteroaryl group," "alkoxy group," and "acyl group" are all non-halogenated and do not contain halogens. The composition for the positive C phase layer may contain only the cellulose ester compound, or it may contain a mixture of two or more of the cellulose ester compounds.

[0060] The term "halogen" above refers to fluorine (F), Cl, Br, or I, and preferably F.

[0061] The above-mentioned "halogen-containing functional group" may include aromatic, aliphatic, or alicyclic functional groups as organic functional groups containing one or more halogens. For example, a 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 having 6 to 20 carbon atoms, or a halogen-substituted aryl group having 7 to 20 carbon atoms.

[0062] The above "halogen-substituted acyl group" is,

number

[0063] The above-mentioned cellulose ester compounds can be produced by methods known to those skilled in the art, or they can be purchased commercially and used in the production of the positive C layer. For example, cellulose ester compounds having an acyl group as a substituent can be produced by reacting the sugar monomer or polymer of the sugar monomer constituting the cellulose of the above formula 1 with trifluoroacetic acid or trifluoroacetic anhydride, or by reacting it with trifluoroacetic acid or trifluoroacetic anhydride and then further reacting it with an acylating agent (e.g., a carboxylic acid anhydride or carboxylic acid), or by reacting trifluoroacetic acid or trifluoroacetic anhydride together with an acylating agent.

[0064] Aromatic compounds may contain a phenyl group and may include, but are not limited to, polystyrene compounds, fluorobenzene compounds, or difluorostyrene structures. In one specific example, the polystyrene compound may include the substructure of the following chemical formula 2.

[0065] [ka] (In formula 2 above,

number

[0066] Examples of substituents R on the styrene ring include alkyl groups, substituted alkyl groups, halogens, hydroxyl groups, carboxyl groups, nitro groups, alkoxy groups, amino groups, sulfonyl groups, phosphates, acyl groups, acyloxy groups, phenyl groups, alkoxycarbonyl groups, and cyano groups.

[0067] In one specific example, R 1 , R 2 , and R 3 One or more of these may be halogens, more preferably fluorine.

[0068] The composition for the positive C layer may further contain additives having aromatic condensed rings in addition to the cellulosic and aromatic compounds mentioned above. Additives having aromatic condensed rings can play a role in adjusting wavelength dispersibility. Examples of additives having aromatic condensed rings include 2-naphthyl benzoate, anthracene, phenanthrene, and dimethyl 2,6-naphthalenedicarboxylate. Additives having aromatic condensed rings can be included in the composition for the positive C layer in an amount of 0.1 to 30% by weight, preferably 1 to 10% by weight. Within this range, there is an effect of adjusting the phase difference expression rate and wavelength dispersibility.

[0069] The thickness of the positive C layer may be 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, the phase difference of the present invention can be easily achieved, and the polarizing plate can be easily made thinner. Negative B-segment

[0070] The negative B layer is a phase difference layer that satisfies the refractive index relationship nx>ny>nz (where nx, ny, and nz are the refractive indices in the slow axis direction, fast axis direction, and thickness direction of the negative B layer at a wavelength of 550 nm, respectively).

[0071] The negative B layer may be a stretched film, as will be described later. The negative B layer has a slow axis and a fast axis in the in-plane direction. When the light absorption axis of the polarizer is 0°, 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. Within this range, it is easy to provide improvements in lateral viewing angle and color tone, as well as improvements in light leakage. For example, when the light absorption axis of the polarizer is 0°, the slow axis of the negative B layer can form an angle of -0.5° to 0.5° (e.g., 0°).

[0072] In one specific example, the slow phase axis of the negative B layer may be substantially parallel to the machine direction of the negative B layer, and the fast phase axis of the negative B layer may be substantially parallel to the width direction of the negative B layer. This can facilitate the production of polarizing plates by roll-to-roll method.

[0073] The negative B layer has an in-plane phase difference of 70-150 nm at a wavelength of 550 nm and a degree of biaxiality of 1.0-1.8. Within the above ranges of in-plane phase difference and degree of biaxiality, lamination on one side of the positive C layer can easily improve the lateral viewing angle and color tone, as well as reduce light leakage. A polarizing plate containing a negative B layer that does not satisfy either the above range of in-plane phase difference or degree of biaxiality may have insufficient improvement in lateral viewing angle and color tone.

[0074] For example, the in-plane phase difference of the negative B layer may be, for example, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, or 150 nm, with 70 to 130 nm being preferred and 80 to 120 nm being more preferred. For example, the degree of biaxiality of the negative B layer may be, for example, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, or 1.8, with 1.0 to 1.6 being preferred and 1 to 1.6, or 1.1 to 1.5 being more preferred.

[0075] The negative B layer may have a thickness-direction phase difference of 35 to 195 nm at a wavelength of 550 nm. Within this range, the above-mentioned in-plane phase difference and degree of biaxiality can be easily achieved. For example, the thickness-direction phase difference of the negative B layer may be, for example, 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, or 195 nm, preferably 35 to 143 nm, more preferably 40 to 120 nm or 48 to 120 nm.

[0076] The material of the negative B layer is not limited as long as it simultaneously satisfies the refractive index relationship, in-plane phase difference, and degree of biaxiality described above. However, in this invention, a negative B layer is particularly used that is produced by treating a composition for the negative B layer with a solution casting method to produce an unstretched film, and then uniaxially stretching the unstretched film produced above in the MD direction of the unstretched film. Generally, there are two types of film manufacturing methods: melt extrusion and solution casting. Melt extrusion is a method of producing an unstretched film by heating a polymer to a molten state and extruding it from an extruder. Therefore, it has good productivity with relatively low equipment costs. On the other hand, with melt extrusion, the thickness of the film cannot be precisely adjusted, and fine lines (so-called die lines) may be formed on the film. 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 good optical isotropy and thickness uniformity compared to melt extrusion, and can produce films with fewer foreign matter. Therefore, solution casting can easily produce optically functional films.

[0077] Typically, in the solution casting method, a polymer is dissolved in a mixed solvent (e.g., a solvent consisting of dichloromethane or methyl acetate) to produce a slurry material, a predetermined additive is mixed with the slurry material to produce a casting slurry, the casting slurry produced is supplied to a casting die and discharged from an discharge slit onto a casting drum, an endless belt, or a continuously moving support, the discharged slurry forms a bead between the discharge slit and the support, and a casting film is produced on the support. The casting film is conveyed onto the support at a constant speed and cooled or dried to become self-supporting. The casting film is peeled from the support to become a wet film, which is then dried and wound up to produce a final film.

[0078] The slurry material described above includes the polymer described above. The polymer is not particularly limited as long as it can form a negative B layer when uniaxially stretched in the MD direction after being made into an unstretched film. For example, the polymer can be a cyclic olefin copolymer (COC); a cellulose ester copolymer containing cellulose acylate, cellulose butyrate, cellulose propionate, cellulose propionate acetate, cellulose acetate butyrate, etc. Preferably, the cyclic olefin copolymer can be used to produce a relatively thin unstretched film by a solution casting method.

[0079] Cyclic olefin copolymers are polymers having a cyclic olefin structure. Examples of cyclic olefin copolymers include norbornene polymers, monocyclic olefin polymers, cyclic conjugated diene polymers, vinyl alicyclic hydrocarbon polymers, or hydrides thereof.

[0080] The slurry material described above may contain a solvent. The solvent is not particularly limited, but examples include any solvent capable of dissolving the polymer (also called a good solvent). Preferred solvents include chlorinated compounds such as dichloromethane and chloroform, linear hydrocarbons, cyclic hydrocarbons, aromatic hydrocarbons, or esters of these having 3 to 12 carbon atoms, their ketones, and / or their ether compounds. The esters, ketones, and ethers may have a cyclic structure.

[0081] The chain hydrocarbons having 3 to 12 carbon atoms may be hexane, octane, isooctane, and decane. The cyclic hydrocarbons having 3 to 12 carbon atoms may be cyclopentane, cyclohexane, and their derivatives. The aromatic hydrocarbons having 3 to 12 carbon atoms may be benzene, toluene, and xylene. The esters having 3 to 12 carbon atoms may be ethyl formate, propyl formate, pentyl formate, methyl acetate, ethyl acetate, and pentyl acetate. The ketones having 3 to 12 carbon atoms may be acetone, methyl ethyl ketone, diethyl ketone, diisobutyl ketone, cyclopentanone, cyclohexanone, and methylcyclohexanone. The ethers having 3 to 12 carbon atoms may be diisopropyl ether, dimethoxymethane, dimethoxyethane, 1,4-dioxane, 1,3-dioxolane, tetrahydrofuran, anisole, and phenetol. Examples of organic solvents having two or more functional groups include 2-ethoxyethyl acetate, 2-methoxyethanol, and 2-butoxyethanol. The boiling point of the organic solvent may preferably be 35 to 150°C.

[0082] Furthermore, in order to adjust the drying properties, viscosity, and other characteristics of the slurry, the solvent may be a mixture of two or more solvents. In this case, the solvent may further contain a poor solvent.

[0083] The poor solvent 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 poor solvent. The alcohol has a linear, branched, or cyclic structure and is preferably a saturated alicyclic hydrocarbon. The alcohol may also be a primary, secondary, or tertiary alcohol. Examples of such alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, tert-butanol, 1-pentanol, 1-methyl-2-butanol, and cyclohexanol. Fluorinated alcohols such as 2-fluoroethanol, 2,2,2-trifluoroethanol, and 2,2,3,3-tetrafluoro-1-propanol are preferred as alcohols. Monohydroxy alcohols are very preferred as poor solvents because they can reduce peeling resistance. While the preferred alcohol varies depending on the good solvent used, from a drying viewpoint, those with a boiling point of 120°C or less are preferred, monohydroxy alcohols with 1 to 6 carbon atoms are more preferred, and alcohols with 1 to 4 carbon atoms are even more preferred. The mixed solvent for cyclic olefin copolymer slurries preferably consists mainly of dichloromethane, with one or more of methanol, ethanol, propanol, isopropanol, and butanol as a poor solvent.

[0084] In the solution casting method, additives can be mixed into the slurry material before dispensing. Examples of such additives include one or more of the following: degradation inhibitors, ultraviolet absorbers, retardation control agents, plasticizers, and fine particles. Preferably, the additives may include fine particles.

[0085] The fine particles are added to reduce the coefficient of dynamic friction on the surface of the film product, thereby reducing stress on the film when handling it. This ensures that when the entire positive C layer and negative B layer are unwound after being wound roll-to-roll, the fine particles prevent complete tearing of the positive C layer and negative B layer. In particular, the fine particles eliminate the need to laminate an additional protective film over the entire positive C layer and negative B layer before winding roll-to-roll, improving the polarizing plate manufacturing process and enabling more economical production.

[0086] The types of fine particles mentioned above are not limited, but they may be fine particles of either an inorganic compound or an organic compound.

[0087] The above inorganic compound may be silicon dioxide (silica), titanium dioxide, 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 a silicon compound such as calcium phosphate. Silicon-containing inorganic compounds and silicon-containing metal oxides are more preferred. From the viewpoint of the anti-fogging effect of the film, silicon dioxide is particularly preferred.

[0088] The above organic compound may be polytetrafluoroethylene, cellulose acetate, polystyrene, polymethyl methacrylate, polypropyl methacrylate, polymethyl methacrylate, polyvinyl carbonate, and starch.

[0089] The primary average particle size of the above 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, the reduction in film haze can be minimized. The above "primary average particle size" can be calculated from the average particle size of the particles measured using a transmission electron microscope.

[0090] In the negative B layer, the fine particles can be contained 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.

[0091] The unstretched film produced by the above solution casting method can be manufactured as a negative B layer by uniaxial stretching in the MD direction of the unstretched film.

[0092] The negative B layer may further include a primer layer formed on at least one side of its surface. The primer layer allows the positive C layer to be easily bonded to one side of the negative B layer. The material, thickness, etc., of the primer layer are not particularly limited, as long as they do not affect the phase difference between the negative B layer or the positive C layer. For example, the primer layer may be polyester, acrylic, or urethane.

[0093] The thickness of the negative B layer may be 20 to 80 μm, preferably 25 to 70 μm, and more preferably 30 to 60 μm. Within the above range, it can be applied to a polarizing plate. A laminate of a positive C layer and a negative B layer

[0094] The laminate of the positive C layer and the negative B layer may have an in-plane phase difference of 70 to 150 nm at a wavelength of 550 nm. Within this range, excellent lateral viewing angle and color perception improvement effects can be obtained. For example, the in-plane phase difference of the laminate at a wavelength of 550 nm may be, for example, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, 120, 125, 130, 135, 140, 145, or 150 nm, with 70 to 130 nm being preferred and 80 to 120 nm being more preferred.

[0095] The laminate of the positive C layer and the negative B layer described above has a thickness-direction phase difference of -52 to 30 nm at a wavelength of 550 nm. If the thickness-direction phase difference of the laminate is less than -52 nm, the perception of black will decrease, the light leakage improvement effect will be very weak, purple or yellow may be visible during color evaluation, and the color perception improvement effect may deteriorate. If the thickness-direction phase difference of the laminate exceeds 30 nm, the perception of black will also decrease, the light leakage improvement effect will be very weak, purple or yellow may be visible during color evaluation, and the color perception improvement effect may deteriorate. For example, the thickness-direction phase difference of the laminate at a wavelength of 550 nm may be -52, -50, -45, -40, -35, -30, -25, -20, -15, -10, -5, 0, 5, 10, 15, 20, 25, or 30 nm. For example, at a wavelength of 550 nm, the phase difference in the thickness direction of the above laminate may preferably be -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.

[0096] The thickness of the laminate of the positive C layer and the negative B layer described above may be 95% or more of the thickness of the phase difference layer, for example, 95% to 100% or 100%. Within this range, the effect of thinning the polarizing plate can be achieved. polarizer

[0097] 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 mainly composed of polyvinyl alcohol resin. Specifically, a polarizer is manufactured by dyeing the polymer film with an iodine dye or a dichroic dye and stretching it in the MD direction (machine direction). In one specific example, a polarizer is manufactured by performing a swelling process, a dyeing process, and a stretching process on the polyvinyl alcohol film, or by selectively performing one or more of the following processes: a complementary color process and a crosslinking process.

[0098] A polarizing film has an absorption axis and a light transmission axis in the in-plane direction. Here, the absorption axis may be the MD direction of the polarizer, and the light transmission axis may be the TD direction (transverse direction) of the polarizer.

[0099] The polarizer may have a single-unit transmittance of 40% or more, for example, 40-46%, and a polarization degree of 95% or more, for example, 95-99.999%. Within the above range, the anti-reflective performance can be improved when used in combination with a phase difference layer. The above "light transmittance" and "polarization degree" are values ​​measured at wavelengths of 380 nm to 780 nm, and reflect visual perception within the corresponding wavelength range.

[0100] The polarizer may have a thickness of 2 to 30 μm, specifically 4 to 25 μm, and can be applied to polarizing plates within the above range.

[0101] The polarizer may be directly attached to the positive C layer (described later) without an adhesive or bonding layer in between, or it may be laminated on the positive C layer via an adhesive or bonding layer.

[0102] Within the above range, it is possible to achieve a thinner polarizing plate.

[0103] The polarizing plate may further include a protective layer on one or both surfaces of the polarizer. First protective layer

[0104] One surface of the polarizer, preferably the surface having the phase difference layer of the polarizer, may further include one or more first protective layers. The first protective layers are included in the laminate and can provide additional functions to the laminate and / or polarizer. For example, the first protective layers can improve the durability and mechanical strength of the laminate by supplementing its thickness.

[0105] 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, for example, cellulose-based (including triacetylcellulose (TAC)); polyester-based (including polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, etc.); cyclic olefin polymer (COP)-based (cyclic olefin copolymer (COC)-based); polycarbonate-based (polyethersulfone-based); polysulfone-based (polyamide-based); polyimide-based (polyolefin-based); polyarylate-based (polyvinyl alcohol-based); polyvinyl chloride-based (polyvinylidene-based); and polyvinylidene chloride-based.

[0106] In one specific example, the first protective layer may be located between the polarizer and the positive C layer.

[0107] In one specific example, the first protective layer may have an in-plane phase difference and a thickness-direction 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 on the sides of the laminate is not affected.

[0108] The polarizing plate may also further include a second protective layer, as described later, on the other surface of the polarizer. The second protective layer may be laminated in one or more layers on the upper surface of the polarizer. Second protective layer

[0109] The second protective layer also protects the polarizer from the effects of the external environment and improves the mechanical strength of the polarizer plate. The second protective layer may be one or more of a protective film and a protective coating layer.

[0110] In one specific example, the second protective layer is an optically transparent film, and may be a film made of one or more resins selected from the group consisting of, for example, cellulose-based materials including triacetylcellulose (TAC); polyester-based materials including polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate (PEN), polybutylene naphthalate, etc.; cyclic olefin polymer (COP)-based materials; cyclic olefin copolymer (COC)-based materials; polycarbonate-based materials; polyethersulfone-based materials; polysulfone-based materials; polyamide-based materials; polyimide-based materials; polyolefin-based materials; polyarylate-based materials; polyvinyl alcohol-based materials; polyvinyl chloride-based materials; and polyvinylidene chloride-based materials.

[0111] A functional coating layer may be further formed on at least one surface of the second protective layer. Examples of functional coating layers include anti-reflective layers, low-reflection layers, hard coat layers, anti-fingerprint layers, anti-glare layers, and primer layers.

[0112] The second protective layer may have a thickness of 5 μm to 70 μm, specifically 15 μm to 45 μm. Within this range, it can be applied to the polarizing plate.

[0113] Figures 1 and 2 are cross-sectional views of the polarizing plate according to the present invention.

[0114] Referring to Figure 1, the polarizing plate may comprise 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.

[0115] Referring to Figure 2, the polarizing plate may comprise 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 sequentially laminated on the lower surface of the polarizer 30.

[0116] Although not shown in Figures 1 and 2, an adhesive layer, bonding layer, or visco-adhesive layer may be further used on the polarizer when laminating the polarizer, each phase difference layer, and protective layer. Additionally, a first protective layer may be further used between the polarizer and the positive C layer.

[0117] The optical display device of the present invention comprises a polarizing plate according to an embodiment of the present invention. The optical display device may also comprise a liquid crystal display device.

[0118] In one specific example, the liquid crystal display device may be a liquid crystal display device that has a plane-switching type liquid crystal layer and operates in IPS mode, FFS mode, or the like.

[0119] In one specific example, the polarizing plate of the present invention can be used as an observation-side polarizing plate or a light source-side polarizing plate.

[0120] Referring to Figure 3, the liquid crystal display device comprises a liquid crystal panel 100 on which liquid crystal layers are arranged, an observation-side polarizing plate laminated on one side of the liquid crystal panel 100, and a light source-side polarizing plate 200 laminated on the other side of the liquid crystal panel. The observation-side polarizing plate comprises a negative B layer 20, a positive C layer 10, and a polarizer 30, which are sequentially laminated from the liquid crystal panel 100.

[0121] In Figure 3, the liquid crystal layer may be a plane-switching liquid crystal, for example, an IPS mode liquid crystal layer. The slow axis of the liquid crystal layer is substantially orthogonal to the light absorption axis of the polarizer in the observation-side polarizer. The light absorption axis of the polarizer in the observation-side polarizer is substantially orthogonal to the light absorption axis of the polarizer in the light source-side polarizer. 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.

[0122] Referring to Figure 4, the liquid crystal display device comprises a liquid crystal panel 100 on which liquid crystal layers are arranged, an observation-side polarizing plate 300 laminated on one side of the liquid crystal panel 100, and a light source-side polarizing plate 300 laminated on the other side of the liquid crystal panel 100. The light source-side polarizing plate comprises a negative B layer 20, a positive C layer 10, and a polarizing plate 30, which are sequentially laminated from the liquid crystal panel 100.

[0123] In Figure 4, the liquid crystal layer may be a plane-switching liquid crystal, for example, an FPS mode liquid crystal layer. The slow axis of the liquid crystal layer is substantially orthogonal to the light absorption axis of the polarizer in the light source-side polarizer. The light absorption axis of the polarizer in the observation-side polarizer is substantially orthogonal to the light absorption axis of the polarizer in the light source-side polarizer. 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. (Embodiment of the invention)

[0124] The structure and operation of the present invention will be described in more detail below through preferred embodiments of the present invention. However, these are merely preferred examples and should not be construed as limiting the present invention in any sense. (Example 1)

[0125] A polyvinyl alcohol-based film (PS#60, manufactured by Nippon Kuraray Co., Ltd., thickness before stretching: 60 μm) was uniaxially stretched six times along the MD (machine direction) direction of the polyvinyl alcohol-based film in an iodine aqueous solution at 55°C to produce a polarizer with a single-unit transmittance of 43%.

[0126] An unstretched film was produced by casting a composition containing a cyclic olefin copolymer (COC) using a solution casting method. Next, the unstretched film was uniaxially stretched in the MD direction at a predetermined stretching ratio to produce a negative B layer having the structure shown in Table 1 below.

[0127] A cellulose ester-based composition (VM500, manufactured by Eastman, USA) was applied to one side of the negative B layer to a predetermined thickness and cured (without a stretching step). A positive C layer having the configuration shown in Table 1 below, and a laminate of the negative B layer and the positive C layer were manufactured on one side of the negative B layer. At a wavelength of 550 nm, the positive C layer had Rth = -110 nm, Re = 0 nm, and a thickness of 4.6 μm.

[0128] The laminate was laminated onto one surface of the polarizer, and the positive C layer was laminated onto the other surface of the polarizer via an adhesive layer. A PET film was laminated onto the other surface of the polarizer as a protective layer via an adhesive layer to produce a polarizing plate in the order of PET film - polarizer - positive C layer - negative B layer. (Examples 2-4)

[0129] In Example 1, a polarizing plate was manufactured using the same method as in Example 1, except that the stretching ratio or the conditions of the solution casting process were changed during the manufacturing of the negative B layer to change the phase difference of the positive C layer. (Comparative Examples 1-4)

[0130] In Example 1, a polarizing plate was manufactured using the same method as in Example 1, except that the stretching ratio or the conditions of the solution casting process were changed during the manufacturing of the negative B layer to change the phase difference of the positive C layer. (Comparative Example 5)

[0131] In Example 1, a polarizing plate was manufactured using the same method 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.

[0132] The Re, Rth, and NZ values ​​for each phase difference layer were measured at a wavelength of 550 nm using AXOSCAN.

[0133] The following physical properties were evaluated using the polarizing plates in the examples and comparative examples, and are shown in Table 1 below.

[0134] (1) Maximum transmittance in all directions: In a Samsung Electronics TV model equipped with an IPS LCD panel, the polarizers manufactured in the examples and comparative examples were mounted and driven in place of the observation-side polarizer. Next, the maximum transmittance in the black display state across the entire field of view was calculated using the Extended Jones Matrix method with the TECHWIZ 1D (manufactured by SANAI SYSTEM, South Korea) simulation program. However, the decrease in transmittance due to the color filter inside the panel was excluded from the above calculation. A lower maximum transmittance indicates that light leakage can be prevented more effectively, further enhancing visual perception.

[0135] (2) Results of visual perception evaluation when no voltage is applied: Polarizing plates manufactured in the examples and comparative examples were attached to a 65-inch FFS panel (manufactured by BOE, China) and visual perception was evaluated. Black perception and color tone were evaluated by visual inspection.

[0136] [Table 1] *Angles in Table 1: The angle the polarizer makes with the slow phase axis of the negative B layer, with the light absorption axis set to 0°.

[0137] As shown in Table 1 above, the polarizing plate of the present invention is expected to provide a sufficient light leakage improvement effect because the maximum transmittance in all directions has been significantly reduced. Furthermore, because the polarizing plate of the present invention has excellent black perception, it is expected to provide an improvement in lateral viewing angle and color perception.

[0138] On the other hand, although the phase difference between the positive C layer and the negative B layer of the present application was satisfied, the polarizer plate of Comparative Example 5, in which the negative B layer and then the positive C layer were laminated in that order from the polarizer, had a significantly reduced sense of blackness and an excessively high maximum transmittance in all directions, making it difficult to use. Furthermore, although the positive C layer and the negative B layer of the present application were arranged, the polarizer 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 was outside the range of the present application, had a reduced sense of blackness and a higher maximum transmittance in all directions than the examples, resulting in a poor light leakage improvement effect.

[0139] Simple amendments or modifications to the present invention can be easily carried out by those skilled in the art, and all such amendments or modifications are considered to fall within the scope of the present invention.

Claims

1. The device comprises a polarizer and a phase difference layer, which includes a positive C layer and a negative B layer, laminated on one surface of the polarizer. The positive C layer is located between the polarizer and the negative B layer. When the optical 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 at a wavelength of 550 nm, and a degree of biaxiality of 1.0 to 1.

8. The laminate of the positive C layer and the negative B layer is a polarizing plate in which the phase difference in the thickness direction at a wavelength of 550 nm is -52 to 30 nm.

2. The polarizing plate according to claim 1, wherein the negative B layer has a phase difference in the thickness direction of 35 to 195 nm at a wavelength of 550 nm.

3. The polarizing plate according to claim 1, wherein the negative B layer comprises one or more selected from the group consisting of cyclic olefin copolymers and cellulose ester copolymers.

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

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

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

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

9. The polarizing plate according to claim 1, wherein the positive C layer has a phase difference in the thickness direction of -150 to -70 nm at a wavelength of 550 nm.

10. The polarizing plate according to claim 1, wherein the positive C layer is a coating layer comprising one or more compounds selected from the group consisting of cellulose compounds or polymers thereof and aromatic compounds or polymers thereof.

11. The polarizing plate according to claim 1, wherein the phase difference layer is laminated on the light incident surface or light emission surface of the polarizing plate.

12. The polarizing plate according to claim 1, wherein the laminate of the positive C layer and the negative B layer has a thickness of 95% or more of the thickness of the phase difference layer.

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

14. A first protective layer is laminated on one surface of the polarizing plate. The polarizing plate according to claim 1, wherein the first protective layer is located between the polarizing plate and the positive C layer.

15. The polarizing plate according to claim 14, wherein the first protective layer has a front-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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