Polarizing plate and optical display device

Abstract

Provided are a polarizing plate and an optical display device, the polarizing plate comprising: a polarizer; a first protective film laminated on the light-exit surface of the polarizer; and a second protective film laminated on the light-incident surface of the polarizer, wherein the first protective film has an internal haze of 1-10%, an external haze of 20-65%, and a total haze of 25-68%, and the second protective film has an in-plane retardation of 45-65 nm at a wavelength of 550 nm and a thickness-direction retardation of 100-150 nm at a wavelength of 550 nm.

Description

Polarizing plate and optical display device

[0001] This relates to a polarizing plate and an optical display device.

[0002]

[0003] A liquid crystal display device essentially includes a polarizing plate. The polarizing plate includes a polarizer and a protective film formed on at least one surface of the polarizer.

[0004] A liquid crystal display makes an image visible by transmitting light from a backlight unit through a light source-side polarizer, an optical display panel, and a viewing-side polarizer in that order. Therefore, in a liquid crystal display, the front side has high brightness and thus a high contrast ratio. However, the brightness of the sides is inevitably lower compared to the front.

[0005] To increase brightness from the side, methods such as changing the protective film on the polarizer or introducing an additional layer may be considered. However, the color shift between the front and the side may become large, leading to color non-uniformity between the front and the side.

[0006] Therefore, when applied to a liquid crystal display, a polarizing plate that can increase the contrast ratio from the front and reduce the color difference between the front and the side may be desirable.

[0007] The background technology of the present invention is disclosed in Korean Registered Patent No. 10-2120989, etc.

[0008]

[0009] According to one embodiment, a polarizing plate is provided that can improve the contrast ratio and reduce the color shift between the front and the side when applied to a liquid crystal display.

[0010]

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

[0012] The above polarizing plate comprises a polarizer; a first protective film laminated on the light-emitting surface of the polarizer; and a second protective film laminated on the light-incident surface of the polarizer, wherein the first protective film has an internal haze of 1 to 10%, an external haze of 20 to 65%, and a total haze of 25 to 68%, and the second protective film has an in-plane phase difference of 45 to 65 nm at a wavelength of 550 nm and a thickness direction phase difference of 100 to 150 nm at a wavelength of 550 nm.

[0013] According to another embodiment, an optical display device is provided.

[0014] The above optical display device includes the polarizing plate.

[0015]

[0016] According to one embodiment, a polarizing plate is provided that can improve the front contrast ratio and reduce the color difference between the front and the side when applied to a liquid crystal display.

[0017]

[0018] Figure 1 is a cross-sectional view of a polarizer of one embodiment.

[0019] FIG. 2 is a cross-sectional view of an optical display device of one embodiment.

[0020]

[0021] With reference to the attached drawings, the present invention is described in detail by way of embodiments so that those skilled in the art can easily implement it. The present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0022] In order to clearly explain the invention in the drawings, parts unrelated to the description have been omitted, and identical or similar components have been given the same names throughout the specification. The lengths and sizes of each component in the drawings are for the purpose of explaining the invention, and the invention is not limited to the lengths and sizes of each component described in the drawings.

[0023] The terms used herein are for describing exemplary embodiments only and are not intended to limit the invention. The singular expression includes the plural expression unless the context clearly indicates otherwise.

[0024] In this specification, "upper" and "lower" are defined based on the drawings, and depending on the viewing angle, "upper" may be changed to "lower" and "lower" to "upper."

[0025] Unless otherwise specified in this specification, a singular form may also include a plural form. Additionally, unless otherwise specified, "A or B" may mean "including A, including B, or including A and B."

[0026] In this specification, "in-plane phase difference (R e )", "Phase difference in thickness direction (R") th )" is represented by the following Equation A and Equation B, respectively:

[0027] [Equation A]

[0028] R e = (n x - n y ) × d

[0029] [Equation B]

[0030] R th = ((n x + n y ) / 2 - n z ) × d

[0031] (In the above equations A and B, n x , n y , n z ε₀, ε₀, and ε₀ are the refractive indices in the slow axis, fast axis, and thickness directions of the corresponding optical element, respectively, at the measurement wavelength, and d is the thickness of the corresponding optical element (unit: nm).

[0032] Unless otherwise specified in this specification, the in-plane phase difference and the thickness direction phase difference are values ​​measured by transmitting light in the normal direction with respect to the in-plane direction of the optical element.

[0033] In this specification, "haze" refers to a value measured using a haze meter in the visible light region, for example, at a wavelength of 380 to 780 nm, and means an average value unless specifically noted. Specifically, haze is a value measured according to JIS K 7136 as [(DT) / (TT)]×100 (DT means diffuse transmittance, and TT means total light transmittance).

[0034] In this specification, the "internal haze" of the first protective film is a value measured using a haze meter after laminating a laminate of an adhesive film and a TAC (triacetylcellulose) film, wherein the total haze is less than 1% (e.g., 0 or more and less than 1%), onto the anti-glare layer (or the anti-glare layer and the anti-reflective layer) of the first protective film. For example, it may be measured as follows:

[0035] A first protective film was cut into a width × height (5cm × 5cm) and fixed to a jig of a haze meter (NIPPON DENSHOKU, NDH-5000), and the total haze was measured. A laminate of an adhesive film (total haze 0%, acrylic-based) and a TAC film was prepared, the first protective film was cut into a width × height (5cm × 5cm), the anti-glare layer of the first protective film was laminated with the adhesive film, and the internal haze was measured by fixing it to a jig of the haze meter.

[0036] In this specification, the "total haze" of the first protective film is a value measured by a conventional method using a haze meter.

[0037] In this specification, the "external haze" of the first protective film is the value obtained by subtracting the internal haze from the total haze.

[0038] In this specification, "(meth)acrylic" means acrylic and / or methacrylic.

[0039] In this specification, when indicating a numerical range, "X to Y" means X or greater and Y or less (X ≤ and ≤Y).

[0040] A polarizing plate according to one embodiment includes a polarizer, a first protective film laminated on the light-emitting surface of the polarizer, and a second protective film laminated on the light-incident surface of the polarizer.

[0041] Here, the 'light incident surface' is the surface where light from a backlight unit passes through a panel for an optical display device (e.g., a panel for a liquid crystal display device) and exits to be incident on a polarizer when the polarizer is laminated on the viewing side of the panel. Here, the 'light exit surface' is the surface where light from the backlight unit is incident on a polarizer and exits from the polarizer.

[0042] The second protective film above is a phase difference film, wherein the in-plane phase difference at a wavelength of 550 nm is 45 to 65 nm and the thickness direction phase difference at a wavelength of 550 nm is 100 to 150 nm.

[0043] When the above second protective film simultaneously satisfies the in-plane phase difference and the thickness direction phase difference, it acts on the light emitted from the panel to improve the front contrast ratio and the side contrast ratio.

[0044] The first protective film can improve contrast ratio and reduce color shift between the front and the side when light passing through the second protective film and the polarizer is emitted.

[0045] Here, the front is (θ,φ)=(0°,0°) in the optical display.

[0046] Here, the sides are (θ, φ)=(70°, 45°), (θ, φ)=(70°, 135°), (θ, φ)=(70°, 225°), and (θ, φ)=(70°, 315°) in the optical display.

[0047] The above color deviation (△L xy) can be calculated using Equation 1 below and can be 0.5 or less:

[0048] [Equation 1]

[0049] △L xy = [(L*1 - L*2) 2 +(x*1 - x*2) 2 + (y*1 - y*2) 2 ] 1 / 2

[0050] (In the above formula,

[0051] L*1 is the luminance at (θ,φ)=(0°,0°)

[0052] L*2 is the average value of the measured luminance for (θ, φ)=(70°, 45°), (θ, φ)=(70°, 135°), (θ, φ)=(70°, 225°), and (θ, φ)=(70°, 315°), respectively.

[0053] x*1 is the x or a* color coordinate at (θ,φ)=(0°,0°),

[0054] x*2 is the measured x or a for (θ, φ)=(70°, 45°), (θ, φ)=(70°, 135°), (θ, φ)=(70°, 225°), and (θ, φ)=(70°, 315°), respectively. * Average value of color coordinates,

[0055] y*1 is y or b at (θ,φ)=(0°,0°). * Color coordinates,

[0056] y*2 is the average value of the measured y or b* color coordinates for (θ, φ)=(70°, 45°), (θ, φ)=(70°, 135°), (θ, φ)=(70°, 225°), and (θ, φ)=(70°, 315°), respectively.

[0057] Among the above color deviations, the luminance, x color coordinate, and y color coordinate can be evaluated according to the CIE1931 color system, or luminance, a * Color coordinates, b * Color coordinates can be evaluated according to the Munsell color system.

[0058] In this regard, the first protective film has an internal haze of 1 to 10%, an external haze of 20 to 65%, and a total haze of 25 to 68%. Within the above range, the color difference between the front and the side can be reduced while improving the front contrast ratio by the second protective film.

[0059] The polarizing plate is described in detail below.

[0060] Second protective film

[0061] The second protective film can improve the contrast ratio by providing an optical compensation function for the polarizer.

[0062] The second protective film has an in-plane phase difference of 45 to 65 nm at a wavelength of 550 nm and a thickness direction phase difference of 100 to 150 nm at a wavelength of 550 nm. It can improve the contrast ratio by acting on light emitted from the panel within the in-plane phase difference range and the thickness direction phase difference range.

[0063] In one embodiment, the second protective film may have an in-plane phase difference of 50 to 65 nm or 50 to 60 nm at a wavelength of 550 nm, and a thickness direction phase difference of 120 to 150 nm, 130 to 150 nm, or 130 to 140 nm at a wavelength of 550 nm.

[0064] The second protective film may have a total haze of 0 to 1%, an internal haze of 0 to 1%, and an external haze of 0 to 1%. Within the above range, it may not affect the effects of the present invention.

[0065] The second protective film may have a thickness greater than 0 and less than or equal to 60 μm, for example, 30 to 55 μm. Within the above range, it may be used in a polarizing plate.

[0066] The second protective film may be a film comprising an optically transparent resin. For example, the second protective film may be a film made of one or more resins selected from a cellulose-based resin including triacetylcellulose (TAC), a polyester-based resin including polyethylene terephthalate (PET), polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate, an acrylic-based resin, a cyclic olefin polymer (COP)-based resin, an amorphous polyolefin (COC)-based resin, a polycarbonate-based resin, a polyethersulfone-based resin, a polysulfone-based resin, a polyamide-based resin, a polyimide-based resin, a polyolefin-based resin, a polyarylate-based resin, a polyvinyl alcohol-based resin, a polyvinyl chloride-based resin, a polyvinylidene chloride-based resin, and an acrylic-based resin. Preferably, the second protective film may be a cyclic olefin polymer (COP)-based or an amorphous polyolefin (COC)-based film.

[0067] The second protective film may be manufactured by melt extrusion or solvent casting of a composition for an unoriented film for the second protective film. Additionally, the unoriented film may have an in-plane phase difference as described above by stretching, etc.

[0068] The second protective film can be adhered to the polarizer by an adhesive layer formed of a water-based or photocurable adhesive.

[0069] An adhesive layer, such as a pressure-sensitive adhesive layer (PSA), for attaching a polarizing plate to a panel or the like may be further laminated on the lower surface of the second protective film.

[0070]

[0071] First protective film

[0072] The first protective film is laminated onto the light-emitting surface of the polarizer to transmit light emitted from the polarizer, thereby allowing the image to be seen.

[0073] The first protective film has an internal haze of 1 to 10%, an external haze of 20 to 65%, and a total haze of 25 to 68%.

[0074] If the internal haze of the first protective film is less than 1% and greater than 10%, there may be a problem of lowering the contrast ratio. In one embodiment, the internal haze of the first protective film may be 2 to 10%, 1 to 8%, or 1 to 5%.

[0075] If the external haze of the first protective film is less than 20% and greater than 65%, the side color deviation may increase. The external haze of the first protective film may be 30 to 58%, for example, 40 to 58%.

[0076] If the total haze of the first protective film is less than 25% and greater than 68%, there may be a problem with the front contrast ratio being lowered. The total haze of the first protective film may be 30 to 68%, for example, 45 to 68%, 30 to 60%, or 45 to 60%.

[0077] As shown above, the first protective film may have an external haze higher than the internal haze. This facilitates the implementation of the effects of the present invention.

[0078] In one embodiment, the ratio of external haze to internal haze in the first protective film may be 2 or more, for example, 2 to 30, or 5 to 30, for example, 8 to 30. Within the above range, it may not affect the improvement of the contrast ratio.

[0079] The first protective film may have a thickness of 20 to 250 μm, for example, 40 to 100 μm. Within the above range, it may be used in a polarizing plate.

[0080] The first protective film may include a base film and an anti-glare layer laminated on the upper surface of the base film. The anti-glare layer may be disposed on the light-emitting surface of the base film.

[0081]

[0082] base film

[0083] The substrate film can support the anti-glare layer.

[0084] The base film may have external haze and internal haze of 3% or less, for example, 1.5% or less. Within the above range, it may not affect the overall haze of the first protective film.

[0085] The substrate film may have a higher refractive index than the anti-glare layer. In one embodiment, the substrate film may have a refractive index of 1.4 to 1.8, specifically 1.45 to 1.8, 1.46 to 1.7, or 1.47 to 1.6.

[0086] The base film may have a thickness of 15 to 250 μm, preferably 40 to 100 μm. Within the above range, it may function as a support for the first protective film.

[0087] The base film may be a film comprising an optically transparent resin. For example, the base film may be a film made of one or more resins selected from cellulose-based resins including triacetylcellulose, polyester-based resins including polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate, acrylic-based resins, cyclic polyolefin-based resins, polycarbonate-based resins, polyethersulfone-based resins, polysulfone-based resins, polyamide-based resins, polyimide-based resins, polyolefin-based resins, polyarylate-based resins, polyvinyl alcohol-based resins, polyvinyl chloride-based resins, and polyvinylidene chloride-based resins. In one embodiment, the base film may have birefringence to allow rainbow streaks to be visible. In this regard, the base film may be a triacetylcellulose film or a polyethylene terephthalate film.

[0088] The base film may be manufactured by melt extrusion or solution casting of a composition for a base film containing the resin. Alternatively, the base film may be manufactured by stretching an unoriented film produced by the melt extrusion or solution casting at a predetermined stretching ratio. The stretching temperature is the glass transition temperature (T) of the unoriented film. g It can be adjusted according to ), for example, Tg It can be ±20℃. Stretching can be performed by ordinary methods known to those skilled in the art.

[0089] The base film may further comprise a primer layer as a functional layer on at least one surface of the base film. The primer layer can improve adhesion to an adherend or an anti-glare layer. The primer layer may be formed from a composition including a resin for the primer layer, such as a urethane-based, acrylic-based, or polyester-based resin, within a range that does not affect the effect of the polarizer.

[0090]

[0091] Anti-glare layer

[0092] The anti-glare layer can help provide overall haze, external haze, and / or internal haze of the first protective film.

[0093] The refractive index of the anti-glare layer can be 1.4 to 1.7, preferably 1.45 to 1.7, more preferably 1.49 to 1.55.

[0094] In one embodiment, the anti-glare layer comprises a matrix and particles impregnated in the matrix, and one surface of the matrix may additionally have irregularities formed thereon. In this case, the entire haze, internal haze, and external haze of the first protective film can be easily reached.

[0095] In another embodiment, the anti-glare layer comprises a matrix, and one surface of the matrix may additionally have irregularities formed thereon. In this case, the entire haze, internal haze, and external haze of the first protective film can be easily reached. The matrix may not contain the particles described above.

[0096] The above particles are light-diffusing particles and may include one or more types of inorganic particles and organic particles.

[0097] The above-mentioned inorganic particles may include spherical silica, such as spherical ones.

[0098] The above organic particles may include polyalkyl (meth)acrylate-based particles, styrene-based particles, etc., including polymethyl methacrylate-based particles.

[0099] In one embodiment, the average particle size D50 of each of the organic particles and the inorganic particles can be 1 to 10 μm, for example, 1 to 4 μm. Within this range, the above-described total haze, internal haze, and external haze ranges can be easily reached.

[0100] The content of inorganic particles, organic particles alone, or the total of inorganic and organic particles in the anti-glare layer can be 0.5% to 10% by weight, for example, 1% to 10% by weight, or 2% to 5% by weight. Within the above range, the above-described total haze and internal haze ranges can be easily reached.

[0101] One surface of the above matrix has irregularities formed thereon, so that it can easily reach the entire haze, internal haze, and external haze of the first protective film.

[0102] In one embodiment, one surface of the matrix, i.e., the surface of the anti-glare layer, has a surface roughness R a The depth can be 0.1㎛ or more, for example, 0.1㎛ to 1.2㎛, 0.2㎛ to 0.7㎛, or 0.4㎛ to 1.2㎛. Within the above range, the total haze, internal haze, and external haze of the first protective film can be easily reached.

[0103] In one embodiment, the anti-glare layer comprises one or more types of inorganic particles and organic particles, and has a surface roughness R a The thickness can be 0.1㎛ or more, for example, 0.1㎛ to 1.2㎛ or 0.4㎛ to 0.5㎛. Within the above range, the total haze, internal haze, and external haze of the first protective film can be easily reached.

[0104] In one embodiment, the anti-glare layer does not include one or more of inorganic particles and organic particles, and has a surface roughness R a The depth can be 0.1㎛ or more, for example, 0.1㎛ to 1.2㎛, 0.2㎛ to 1.15㎛, or 0.5㎛ to 1.15㎛. Within the above range, the total haze, internal haze, and external haze of the first protective film can be easily reached.

[0105] The above matrix may include a cured product of a composition comprising one or more of a curable monomer, a curable oligomer, and an initiator. The above matrix may further include a conventional additive included in an anti-glare layer.

[0106] The above-mentioned matrix composition may be active energy beam curable or thermocurable.

[0107] The curable resin may be one or more of a thermosetting resin and an active energy beam curable resin, and preferably, it may be an active energy beam curable resin for ease of forming an anti-glare layer and reliability of surface roughness.

[0108] Active energy beam curable resin refers to a resin that is cross-linked and cured by irradiation with active energy beams, such as ultraviolet rays or electron beams. The active energy beam curable resin can be selected to facilitate providing the refractive index of the matrix after curing. For example, the resin may be acrylic, urethane, polyester, epoxy, epoxy (meth)acrylate, or urethane (meth)acrylate. Preferably, the active energy beam curable resin may be a urethane (meth)acrylate type, and more preferably a polyfunctional urethane (meth)acrylate type.

[0109] Curable monomers and curable oligomers can each improve the applicability of a matrix composition by increasing the curing rate of the matrix composition while lowering the viscosity. Each of the curable monomers and curable oligomers can be active energy beam curable or thermocurable.

[0110] Active energy beam curable monomers refer to monomers that are cross-linked and cured by irradiation with active energy beams, such as ultraviolet rays or electron beams. Active energy beam curable monomers can increase the curing rate of the matrix composition and increase the degree of dispersion of organic particles. For example, active energy beam curable monomers can be selected to facilitate providing the refractive index of the matrix after curing. For example, the monomer may suitably be a (meth)acrylate having 2 to 10 functional groups, for example, 2 to 6 functional groups. The 2 to 10 functional (meth)acrylates may be selected from types known to those skilled in the art. For example, active energy beam curable monomers include difunctional acrylates such as tricyclodecane dimethanol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, neopentyl glycol adipate di(meth)acrylate, ethoxylated bisphenyl fluorene di(meth)acrylate, etc.; trifunctional (meth)acrylates such as trimethylolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate; and tetrafunctional acrylates such as diglycerin tetra(meth)acrylate or pentaerythritol tetra(meth)acrylate. Examples include but are not limited to pentaerythritol penta(meth)acrylate and other pentaerythritol acrylates; and hexafunctional acrylates such as dipentaerythritol hexa(meth)acrylate, caprolactone-modified dipentaerythritol hexa(meth)acrylate, or urethane (meth)acrylates (e.g., reactants of isocyanate monomers and trimethylolpropane tri(meth)acrylate).

[0111] The initiator may include one or more of a photoinitiator and a thermal initiator. The photoinitiator

[0112] It may include one or more of a photoradical initiator and a photocation initiator. The photoinitiator can cure an active energy beam curable resin, an active energy beam curable monomer, or an active energy beam curable oligomer. The photoradical initiator may include, but is not limited to, photoradical initiators such as acetophenone-based and cyclohexyl ketone-based photoradical initiators.

[0113] The additive may include one or more additives commonly used in optical films, such as dispersants, surfactants, light stabilizers, UV absorbers, and heat stabilizers. Preferably, by including a dispersant as an additive, the clumping of inorganic particles and organic particles in the anti-glare layer can be prevented.

[0114] Based on solid content, the composition for the matrix may include, as a curable resin, 60% to 98% by weight, preferably 92% to 98% by weight, of one or more curable monomers and curable oligomers; 1% to 5% by weight, preferably 2% to 4% by weight, of an initiator; and 0.05% to 3% by weight, preferably 0.1% to 1.5% by weight, of an additive. Within the above range, the refractive index of the anti-glare layer of the present invention can be easily reached, and the curing rate of the anti-glare layer can be increased to increase the mechanical strength of the first protective film.

[0115] The composition for the matrix may include a selected appropriate solvent. The solvent can improve the applicability of the composition for the matrix. The solvent is not particularly limited, but may be methyl ethyl ketone, propylene glycol methyl ether, etc.

[0116] The anti-glare layer may have a thickness of 2㎛ to 15㎛, specifically 3㎛ to 7㎛, more specifically 4㎛ to 6㎛. Within the above range, it may be used in an optical display device.

[0117] The first protective film may further include an anti-reflection layer on the upper surface of the anti-glare layer.

[0118]

[0119] Anti-reflective layer

[0120] The anti-reflection layer has a lower refractive index compared to the anti-glare layer, which can lower the reflectivity of the polarizer. In one embodiment, the anti-reflection layer may have a refractive index of 1.4 or less, for example, 1.3 to 1.37. Within this range, it may be easy to lower the reflectivity of the polarizer.

[0121] The anti-reflection layer may include one or more of low-refractive-index particles and fluorine-based compounds. Low-refractive-index particles and fluorine-based compounds can lower the refractive index of the anti-reflection layer.

[0122] The low-refractive-index particles may be particles having a lower refractive index compared to the anti-glare layer. For example, the low-refractive-index particles may have a hollow structure to have a low refractive index. For example, hollow silica may be preferred as the low-refractive-index inorganic particles. The refractive index may be less than 1.4, for example, between 1.0 and 1.3. Within this range, the refractive index of the anti-reflection layer can be easily lowered.

[0123] Low refractive index particles have a low average particle size (D) relative to the thickness of the anti-reflection layer. 50 It has ), for example, average particle size (D 50 ) can be 20 nm to 120 nm, for example, 40 nm to 100 nm. Within the above range, it can be contained in the anti-reflection layer.

[0124] Low refractive index particles may be included in the anti-reflection layer in an amount of 30% to 70% by weight, for example, 35% to 55% by weight. Within the above range, the reflectance of the present invention can be easily achieved.

[0125] Fluorine-based compounds can facilitate lowering the refractive index of the anti-reflective layer even when using a small amount of low-refractive-index particles. Fluorine-based compounds may include fluorine-containing (meth)acrylate monomers, oligomers thereof, or resins thereof.

[0126] In addition to low-refractive-index particles and fluorine-based compounds, the composition for the anti-reflection layer may further include one or more of an active energy beam curable resin and an active energy beam curable monomer, and a photoinitiator. The active energy beam curable resin and the active energy beam curable monomer can be cured to facilitate the formation of the matrix of the anti-reflection layer and to allow the low-refractive-index particles to be stably incorporated into the anti-reflection layer.

[0127] The active energy beam curable resin, active energy beam curable monomer, and photoinitiator are substantially the same as those described in the anti-glare layer above.

[0128] A composition for an anti-reflection layer may comprise, based on solid content, 30% to 60% by weight of one or more of an active energy beam curable resin and an active energy beam curable monomer, 40% to 60% by weight of low refractive index particles, 0% to 40% by weight of a fluorine-based compound, and 1% to 4% by weight of a photoinitiator. Within the above range, the anti-reflection layer of the present invention can be easily obtained.

[0129] The composition for the anti-reflective layer may include a suitable solvent selected within a range that does not dissolve low-refractive-index particles. The solvent is not particularly limited, but may be methyl ethyl ketone, propylene glycol methyl ether, etc.

[0130] The composition for the anti-reflective layer may further include conventional additives. For example, the additives may be conventional additives known to those skilled in the art that add antifouling and slim properties to the anti-reflective layer. As anti-slip agents, the additives may include one or more of fluorine-containing additives and silicone-based additives.

[0131] The anti-reflective layer may have a thickness of 90 nm to 150 nm, specifically 90 nm to 120 nm. Within the above range, it may be included as an anti-reflective layer in the film.

[0132] An anti-reflective layer can be formed by applying an anti-reflective layer composition to one surface of an anti-glare layer and drying and curing it. Curing can be performed by conventional methods known to those skilled in the art, such as heat curing or photocuring.

[0133] The first protective film may be manufactured by first producing a base film and then forming an anti-glare layer on one side of the base film. Alternatively, the first protective film may be manufactured by forming an anti-glare layer on one side of an unoriented base film and then stretching it.

[0134]

[0135] polarizer

[0136] The polarizer is a linear light-absorbing polarizer that can provide a polarization function by transmitting only light in one direction among the incident light and absorbing light in a direction perpendicular to that direction.

[0137] In one embodiment, the direction of the light absorption axis of the polarizer and the mechanical direction of the substrate film may be substantially parallel.

[0138] The polarizer is a polyvinyl alcohol (PVA)-based film polarizer. Here, "polyvinyl alcohol-based" may refer not only to polyvinyl alcohol itself but also to derivatives of polyvinyl alcohol. Preferably, the polarizer may be a polyvinyl alcohol derivative film polarizer.

[0139] In one embodiment, a derivative of polyvinyl alcohol contains a hydrophilic functional group and a hydrophobic functional group. The hydrophobic functional group is additionally present in addition to the hydroxyl group (OH group), which is a hydrophilic functional group present in polyvinyl alcohol. The hydrophobic functional group may be present in one or more of the main chain and side chains of the polyvinyl alcohol derivative resin. The "main chain" refers to a portion forming the main framework of the polyvinyl alcohol derivative, and the "side chain" refers to a framework connected to the main chain. Preferably, the hydrophobic functional group may be present in the main chain of the polyvinyl alcohol derivative.

[0140] Polyvinyl alcohol derivatives having hydrophilic and hydrophobic functional groups introduced can be prepared by polymerizing one or more vinyl ester monomers, such as vinyl acetate, vinyl formate, vinyl propionate, vinyl butyrate, vinyl pivalate, and isopropene acetate, with a monomer providing a hydrophobic functional group. Preferably, the vinyl ester monomer may include vinyl acetate. The monomer providing the hydrophobic functional group may include a monomer providing a repeating hydrocarbon unit, such as ethylene or propylene.

[0141] The polyvinyl alcohol-based film may have a thickness of 60 μm or less, for example, from 10 μm to 60 μm. Within the above range, there may be no melting or breakage of the film during film stretching.

[0142] Polyvinyl alcohol-based films may use TS-#4500 (or similar, Kuraray, Japan) PVA film, but are not limited thereto.

[0143] A polarizer is a polarizer to which a dichroic material is applied. The dichroic material may be an iodine-based material or a dichroic dye such as an azo dye. Generally, polarizers to which an iodine-based material is applied can be classified as iodine-based polarizers, and polarizers to which a dichroic dye is applied can be classified as dye-based polarizers. In the present invention, both iodine-based polarizers and dye-based polarizers may be used.

[0144] The polarizer may have a thickness of 25 μm or less, for example, greater than 0 μm and less than or equal to 25 μm, for example, between 10 μm and 20 μm. Within the above range, it may be used in a polarizing plate.

[0145] The manufacturing method of a polarizer is described in detail below.

[0146] A polarizer can be manufactured by a manufacturing method comprising a dyeing process, a stretching process, and a crosslinking process. In one embodiment, the polarizer can be manufactured in the order of a dyeing process, a stretching process, and a crosslinking process. At this time, the order of the dyeing process and the stretching process may be changed. At this time, the order of the stretching process and the crosslinking process may be changed. A complementary color process may be further performed after the crosslinking process.

[0147]

[0148] [Dyeing Process]

[0149] The dyeing process includes treating a polyvinyl alcohol-based film in a dyeing tank containing a dichroic substance. In the dyeing process, the polyvinyl alcohol-based film is immersed in a dyeing tank containing a dichroic substance. The dyeing tank containing a dichroic substance includes an aqueous solution containing a dichroic substance and boric acid. By including the dichroic substance and a boron compound together, the dyeing tank dyes the polyvinyl alcohol-based film, and even if the polyvinyl alcohol-based film is stretched under the stretching conditions described above, the polyvinyl alcohol-based film may not break.

[0150] The dichroic material may include one or more of potassium iodide, hydrogen iodide, lithium iodide, sodium iodide, zinc iodide, lithium iodide, aluminum iodide, lead iodide, and copper iodide as iodine. The dichroic material may be included in the dyeing tank, preferably in the dyeing solution, at a concentration of 0.5% to 10% by weight, more preferably 0.5% to 5% by weight. Within this range, the effect of enabling uniform dyeing may be achieved. For example, the dichroic material may be included in the dyeing solution at a concentration of 0.5% to 1% by weight, and within this range, the manufacture of a polarizer having the aforementioned shrinkage force may be facilitated.

[0151] Boron compounds can help prevent melting and rupture of polyvinyl alcohol-based films during the stretching process of polyvinyl alcohol-based films. Boron compounds can help prevent melting and rupture of the film even when the polyvinyl alcohol-based film is stretched at high temperatures and high stretch ratios during the stretching process performed after the dyeing process.

[0152] The boron compound may include one or more of boric acid and borax. The boron compound may be included in the dyeing bath, preferably in an aqueous dyeing solution, at a concentration of 0.1% to 5% by weight, preferably 0.3% to 3% by weight. Within this range, there may be no melting or breakage during the stretching process, and high reliability may be achieved. For example, the dichroic material in the dyeing solution may be included at a concentration of 0.1% to 0.5% by weight, and within this range, it may be easy to manufacture a polarizer having the aforementioned shrinkage force.

[0153] It may be preferable to set the temperature of the dyeing solution to 20°C to 50°C, specifically 25°C to 40°C. The dyeing process can be carried out by immersing a polyvinyl alcohol-based film in a dyeing tank for 30 seconds to 120 seconds, specifically 40 seconds to 80 seconds.

[0154]

[0155] [Stretching Process]

[0156] The stretching process includes stretching a dyed polyvinyl alcohol-based film at a stretching ratio of 5.7 times or more, for example, 5.7 to 7 times, and at a stretching temperature of 57°C or more, for example, 57°C to 65°C. When a conventional polyvinyl alcohol-based film is stretched at the above-mentioned stretching ratio and stretching temperature, the polyvinyl alcohol-based film melts and / or breaks, making it impossible to manufacture a polarizer.

[0157] The stretching process is performed in either wet stretching or dry stretching. Preferably, the stretching process includes wet stretching to apply a boron compound during the stretching process. Wet stretching involves uniaxially stretching a polyvinyl alcohol-based film in a mechanical direction in an aqueous solution containing a boron compound.

[0158] The boron compound may include one or more of boric acid and borax, preferably boric acid. The boron compound may be included in the stretching bath, preferably in the stretching aqueous solution, at a concentration of 0.5% to 10% by weight, preferably 1% to 5% by weight. Within this range, there may be an effect of achieving high reliability without melting or fracture during the stretching process. For example, the boron compound may be included in the stretching bath at a concentration of 3.0% to 3.5% by weight, and within this range, it may be easy to manufacture a polarizer having the aforementioned shrinkage force.

[0159] The stretching bath may further include a dichroic material. The detailed types of the dichroic material are the same as those described above. The dichroic material may be included in the stretching bath, preferably in the stretching solution, at a concentration of 0.5% to 10% by weight, preferably 0.5% to 5% by weight. Within this range, the effect of enabling uniform dyeing may be achieved. For example, the dichroic material may be included in the stretching solution at a concentration of 3.0% to 3.5% by weight, and within this range, it may be easy to manufacture a polarizer having the aforementioned shrinkage force.

[0160]

[0161] [Bridge Process]

[0162] A crosslinking process is performed to strengthen the adsorption of dichroic substances on polyvinyl alcohol-based films that have undergone a stretching process. The crosslinking solution used in the crosslinking process contains a boron compound. The boron compound can help improve reliability even when the polarizer is subjected to thermal shock while strengthening the adsorption of the aforementioned dichroic substances.

[0163] The boron compound may include one or more of boric acid and borax. The boron compound may be included in the crosslinking agent, preferably in an aqueous crosslinking solution, at a concentration of 0.5% to 10% by weight, preferably 1% to 5% by weight. Within this range, there may be an effect of achieving high reliability without melting or breakage during the stretching process. The temperature of the crosslinking agent solution may preferably be 20°C to 50°C, specifically 25°C to 40°C. The crosslinking process may be performed by immersing the polyvinyl alcohol-based film in the crosslinking agent for 30 to 120 seconds, specifically 40 to 80 seconds.

[0164]

[0165] [Complementary Color Process]

[0166] The complementary color process can improve the durability of polyvinyl alcohol-based films.

[0167] The color correction process can be performed by introducing a polyvinyl alcohol-based film into a color correction bath and leaving it to stand. The color correction bath may further contain potassium iodide. Potassium iodide in the color correction bath may be included in an amount greater than 0% by weight and less than or equal to 10% by weight, preferably 1% to 5% by weight. Within the above range, the polarizer of the present invention can be easily reached.

[0168] Before the dyeing process treatment, the polyvinyl alcohol-based film may additionally include one or more of a washing process and a swelling process.

[0169] The washing process involves washing the polyvinyl alcohol-based film with water to remove foreign substances adhering to the polyvinyl alcohol-based film.

[0170] The swelling process can facilitate the dyeing and stretching of dichroic materials by immersing a polyvinyl alcohol-based film in a swelling bath within a predetermined temperature range. The swelling process may include treatment at 15°C to 35°C, preferably 20°C to 30°C, for 30 to 50 seconds.

[0171] The first protective film can be adhered to the polarizer by an adhesive layer formed of a water-based or photocurable adhesive.

[0172] Referring to FIG. 1, the polarizer comprises a polarizer 10, a second protective film 20 laminated on the light incident surface of the polarizer 10, and a first protective film 20 laminated on the light exit surface of the polarizer 10, wherein the first protective film 20 comprises a substrate film 21 and an anti-glare layer 22 laminated on one surface of the substrate film 21.

[0173] According to another embodiment, the optical display device includes a polarizing plate of the present invention.

[0174] The optical display device may be a liquid crystal display, a light-emitting element display, etc., but preferably it may be a liquid crystal display.

[0175] Referring to FIG. 2, the liquid crystal display device may include a panel 100 for the liquid crystal display device, a viewing-side polarizer 110 laminated on one side of the panel 100 for the liquid crystal display device, and a light source-side polarizer 210 laminated on the other side of the panel 100 for the liquid crystal display device.

[0176] In one embodiment, the optical display device comprises a backlight unit, a light source-side polarizer, a panel for the optical display device, and a viewing-side polarizer stacked sequentially, and the viewing-side polarizer may include the polarizer of the present invention. The backlight unit may include a white light source having a continuous emission spectrum as a light source.

[0177]

[0178] Hereinafter, the structure and operation of the present invention will be explained 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 interpreted in any way as limiting the present invention.

[0179] Example 1

[0180] A polyvinyl alcohol film (TS-#4500, Kuraray, Japan, thickness: 45 μm) washed with water at 25°C was subjected to swelling treatment in a swelling bath of water at 30°C. The film that passed through the swelling bath was dyed by treating it for 65 seconds in a dyeing bath at 30°C containing an aqueous solution containing 0.8 wt% potassium iodide and 0.5 wt% boric acid. The film that passed through the dyeing bath was stretched at a stretching ratio of about 6 times in a wet stretching bath containing an aqueous solution at 60°C containing 3.6 wt% boric acid and 3.5 wt% potassium iodide to produce a polarizer.

[0181] The first protective film used is a film in which a base film and an anti-glare layer are laminated on one side of the base film. The base film is a polyethylene terephthalate film (Toyobo). The anti-glare layer has an average particle size D 50 It comprises spherical silica of 1 to 4 μm, and has a surface roughness R a A layer (DNP) with a value of 0.48 µm was used. The first protective film has the internal haze, external haze, and total haze shown in Table 1 below. The internal haze, external haze, and total haze were measured by the haze meter NDH-5000 (NIPPON DENSHOKU) using the method described above. The surface roughness R a The value was measured using the standard method with the Keyence VK-X1100 surface roughness meter.

[0182] For the second protective film, a cyclic olefin polymer film (Zeon, ZB12, with an in-plane phase difference of 55 nm and a thickness direction phase difference of 135 nm at a wavelength of 550 nm) was used. The phase difference was measured at a wavelength of 550 nm using an AXOMETRIC (AXO-SCAN).

[0183] A polarizing plate was manufactured by attaching a first protective film to the upper surface of the polarizer manufactured above using a UV-curing adhesive and attaching a second protective film to the lower surface of the polarizer using a UV-curing adhesive.

[0184]

[0185] Example 2

[0186] The first protective film used is a film in which a base film and an anti-glare layer are laminated on one side of the base film. The base film is a triacetylcellulose film (Konica). The anti-glare layer used is a layer (DAICEL) that does not contain a light diffusing agent including silica beads and has a surface roughness Ra value of 0.76 μm. The first protective film has the internal haze, external haze, and total haze shown in Table 1 below.

[0187] A polarizing plate was manufactured in the same manner as in Example 1, except that the above-mentioned first protective film was used.

[0188]

[0189] Example 3

[0190] The first protective film used is a film in which a base film and an anti-glare layer are laminated on one side of the base film. The base film is a triacetylcellulose film (Konica). The anti-glare layer used is a layer (DAICEL) that does not contain a light diffusing agent including silica beads and has a surface roughness Ra value of 0.77 μm. The first protective film has the internal haze, external haze, and total haze shown in Table 1 below.

[0191] A polarizing plate was manufactured in the same manner as in Example 1, except that the above-mentioned first protective film was used.

[0192]

[0193] Example 4

[0194] The first protective film used is a film in which a base film and an anti-glare layer are laminated on one side of the base film. The base film is a triacetylcellulose film (Konica). The anti-glare layer used is a layer (DAICEL) that does not contain a light diffusing agent including silica beads and has a surface roughness Ra value of 1.12 μm. The first protective film has the internal haze, external haze, and total haze shown in Table 1 below.

[0195] A polarizing plate was manufactured in the same manner as in Example 1, except that the above-mentioned first protective film was used.

[0196]

[0197] Example 5

[0198] The first protective film used is a film in which a base film and an anti-glare layer are laminated on one side of the base film. The base film is a triacetylcellulose film (Konica). The anti-glare layer does not contain a light-diffusing agent including silica beads and has a surface roughness R a A layer with a value of 1.15㎛ (DAICEL) was used. The first protective film has the internal haze, external haze, and total haze of Table 1 below.

[0199] A polarizing plate was manufactured in the same manner as in Example 1, except that the above-mentioned first protective film was used.

[0200]

[0201] Comparative Example 1

[0202] The first protective film used was a polyethylene terephthalate film (Toyobo). A polarizing plate was manufactured in the same manner as in Example 1, except that the first protective film was used.

[0203]

[0204] Comparative Example 2

[0205] The first protective film used is a film in which a base film and an anti-glare layer are laminated on one side of the base film. The base film is a polyethylene terephthalate film (Toybo). The anti-glare layer has an average particle size D 50 It comprises spherical silica of 1 to 4 μm, and surface roughness R a A layer with a value of 0.089 μm (DNP) was used. The first protective film has the internal haze, external haze, and total haze of Table 1 below. A polarizer was manufactured in the same manner as in Example 1, except that the first protective film was used.

[0206]

[0207] Comparative Example 3

[0208] The first protective film used is a film in which a base film and an anti-glare layer are laminated on one side of the base film. The base film is a polyethylene terephthalate film (Toybo). The anti-glare layer has an average particle size D 50 It comprises spherical silica of 1 to 4 μm, and surface roughness R a A layer with a value of 0.39 μm (DNP) was used. The first protective film has the internal haze, external haze, and total haze of Table 1 below. A polarizer was manufactured in the same manner as in Example 1, except that the first protective film was used.

[0209]

[0210] Comparative Example 4

[0211] The first protective film used is a film in which a base film and an anti-glare layer are laminated on one side of the base film. The base film is a polyethylene terephthalate film (Toybo). The anti-glare layer does not contain a light diffusing agent including silica beads and has a surface roughness R a A layer with a value of 1.19 μm (DAICEL) was used. The first protective film has the internal haze, external haze, and total haze of Table 1 below.

[0212] A polarizing plate was manufactured in the same manner as in Example 1, except that the above-mentioned first protective film was used.

[0213]

[0214] Comparative Example 5

[0215] The first protective film used is a film in which a base film and an anti-glare layer are laminated on one side of the base film. The base film is a polyethylene terephthalate film (Toybo). The anti-glare layer has an average particle size D 50 It comprises spherical silica of 1 to 5 μm, and surface roughness R aA layer with a value of 0.54 μm (DNP) was used. The first protective film has the internal haze, external haze, and total haze of Table 1 below. A polarizer was manufactured in the same manner as in Example 1, except that the first protective film was used.

[0216]

[0217] The following physical properties were evaluated using polarizing plates manufactured in the examples and comparative examples.

[0218] An evaluation model was manufactured by removing the viewing-side polarizer from a liquid crystal panel model (55-inch, CSOT, UHD Cell and BLU WLED, vertically aligned liquid crystal), laminating the polarizers manufactured in the example and comparative example as the viewing-side polarizers, and aging them for 60 minutes to stabilize the brightness. At this time, the first protective film among the polarizers was positioned at the outermost edge of the viewing side.

[0219] The following physical properties were evaluated using the manufactured evaluation model and are shown in Table 1 below.

[0220] (1) Front Contrast Ratio (CR) (no unit): After running the above model, measurements were taken from the front using the luminance and color meter EZ-CONTEST (EILDIM) in white mode and black mode, respectively, and the front contrast ratio was calculated as the ratio of the luminance in white mode to the luminance in black mode.

[0221] (2) Color deviation (△L xy )(Unit: None): After running the above model, the brightness and color values ​​were measured at the front (θ,φ)=(0°,0°), and side (θ, φ)=(70°, 45°), (θ, φ)=(70°, 135°), (θ, φ)=(70°, 225°), and (θ, φ)=(70°, 315°), respectively, using the luminance and color meter EZ-CONTEST (EILDIM), and calculated according to Equation 1 above.

[0222] Second protective film First protective film Front contrast ratio △L xy R e Rth Internal Haze External Haze Total Haze Comparative Example 1 551 350.20 0.26 10 20.53 Comparative Example 2 551 352 0 26 0 9 10.53 Comparative Example 3 551 352 41 255 7 10 0.51 Comparative Example 4 551 352 70 72 48 13 0.34 Comparative Example 5 551 354 11 155 90 40.52 Example 1 551 355 42 47 52 17 0.46 Example 2 551 352 56 58 535 9 0.40 Example 3 551 352 58 60 532 10.37 Example 4 551 353 65 68 50 70.34 Example 5 551 351 0 20 30 49 8 10.49

[0223] As can be seen from Table 1 above, the polarizing plate of the example improved both the front contrast ratio and the color difference between the front and the side.

[0224] However, the polarizer of the comparative example was insufficient to improve both the front contrast ratio and the color deviation between the front and the side.

[0225]

[0226] Simple variations or modifications of the present invention can be easily implemented by those skilled in the art, and all such variations or modifications are considered to be included within the scope of the present invention.

Claims

1. A polarizer; a first protective film laminated on the light-emitting surface of the polarizer; and a second protective film laminated on the light-incident surface of the polarizer, comprising The first protective film has an internal haze of 1 to 10%, an external haze of 20 to 65%, and a total haze of 25 to 68%, and The above second protective film is a polarizing plate having an in-plane phase difference of 45 to 65 nm at a wavelength of 550 nm and a thickness direction phase difference of 100 to 150 nm at a wavelength of 550 nm.

2. In paragraph 1, the second protective film is a polarizing plate having a total haze of 0 to 1%, an internal haze of 0 to 1%, and an external haze of 0 to 1%.

3. In paragraph 1, the second protective film is a polarizing plate, wherein the second protective film is a cyclic olefin polymer (COP) or amorphous polyolefin (COC) film.

4. In paragraph 1, the first protective film is a polarizing plate having a ratio of external haze to internal haze of 2 or more.

5. In claim 1, the first protective film comprises a base film and an anti-glare layer laminated on one surface of the base film, a polarizing plate.

6. In paragraph 5, the surface of the anti-glare layer has a surface roughness R a A polarizing plate having a thickness of 0.1㎛ or more.

7. In claim 6, the anti-glare layer has an average particle size D 50 A polarizing plate comprising silica of 1 to 10 μm.

8. A polarizing plate according to claim 7, wherein the silica is included in the anti-glare layer in an amount of 0.5% to 10% by weight.

9. In paragraph 5, the anti-glare layer is a polarizing plate that does not contain one or more of light-diffusing organic particles and inorganic particles.

10. A polarizing plate according to claim 1, wherein a reflective ring layer is further laminated on the anti-glare layer.

11. An optical display device comprising a polarizing plate according to any one of claims 1 to 10.

Images