Polarizing plate and optical display device

Abstract

Provided are a polarizing plate and an optical display device comprising same, the polarizing plate comprising a polarizer and an optical functional layer layered on one surface of the polarizer, wherein: the optical functional layer includes a first skin layer, a core layer and a second skin layer, which are sequentially layered; the core layer includes a matrix and a plurality of microstructures dispersed in the matrix; at least some of the plurality of microstructures include a core layer, which includes a first resin and needle-shaped particles that are oriented in one direction in the first resin and are surface-treated; and the optical functional layer has a ratio of 0.3 to 0.82 in formula 1. [Formula 1] Ratio = b / (a+b+c) (In formula 1, a is the thickness of the first skin layer, b is the thickness of the core layer, c is the thickness of the second skin layer, and the unit of each of a, b and c is μm.)

Description

Polarizing plates and optical display devices

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

[0002]

[0003] The liquid crystal display device has a structure in which a polarizing plate on the viewer side, a liquid crystal panel, and a polarizing plate on the light source side are sequentially laminated.

[0004] Liquid crystal displays (LCDs) offer many advantages, but they suffer from low side visibility and low brightness. To address these issues, a method has been proposed: adding a visibility-enhancing layer, comprising two resin layers with different refractive indices and a pattern formed at the interface between the resin layers, to the polarizing plate on the viewing side. However, this visibility-enhancing layer suffers from yield degradation and material cost savings due to the pattern-forming process. Therefore, a polarizing plate that can improve visibility without this visibility-enhancing layer is desired.

[0005] The background technology of the present invention is disclosed in Korean Patent Publication No. 2018-0047569, etc.

[0006]

[0007] According to one embodiment, a polarizing plate having a visibility improvement effect is provided without having a pattern, for example, a visibility improvement pattern itself or a visibility improvement layer having a pattern.

[0008] According to another embodiment, a polarizing plate is provided in which both frontal luminance and anisotropic diffusion are improved.

[0009] Another embodiment provides a polarizing plate that provides excellent contrast ratio effects even from the front and side.

[0010] According to another embodiment, a polarizing plate having excellent compatibility between a first resin and needle-shaped particles among microstructures is provided.

[0011]

[0012] A polarizing plate according to an embodiment is provided.

[0013] The polarizing plate comprises a polarizer; and an optical functional layer laminated on one surface of the polarizer, wherein the optical functional layer comprises a first skin layer, a core layer, and a second skin layer laminated sequentially, wherein the core layer comprises a matrix and a plurality of microstructures dispersed within the matrix, and wherein at least some of the plurality of microstructures comprise a first resin and acicular particles oriented in one direction and surface-treated within the first resin, and wherein the optical functional layer has a ratio of the following formula 1 of 0.3 to 0.82:

[0014] [Formula 1]

[0015] ratio = b / (a + b + c)

[0016] (In the above equation 1,

[0017] a is the thickness of the first skin layer,

[0018] b is the thickness of the core layer,

[0019] c is the thickness of the second skin layer,

[0020] The units of a, b and c are each ㎛).

[0021] According to another embodiment, an optical display device is provided.

[0022] The above optical display device includes a polarizing plate.

[0023]

[0024] According to one embodiment, a polarizing plate having a visibility improvement effect is provided without having a pattern, for example, a pattern itself for improving visibility or a visibility improvement layer having a pattern.

[0025] According to another embodiment, a polarizing plate having improved frontal luminance and anisotropic diffusion properties is provided.

[0026] According to another embodiment, a polarizing plate is provided that provides an excellent contrast ratio effect even from the front and side.

[0027] According to another embodiment, a polarizing plate having excellent compatibility between the first resin and the needle-shaped particles among the microstructures was provided.

[0028]

[0029] Figure 1 is a conceptual diagram of an optical functional layer.

[0030] Figure 2 is a conceptual diagram of a needle-shaped particle.

[0031] Fig. 3 is a cross-sectional view of an optical functional layer in the direction of the light absorption axis of a polarizer among polarizing plates according to an embodiment.

[0032] Fig. 4 is an enlarged cross-sectional view of an optical functional layer in the direction of the light absorption axis of a polarizer among polarizing plates according to an embodiment.

[0033] Fig. 5 is a cross-sectional view of an optical functional layer in the direction of the light transmission axis of a polarizer among polarizing plates according to an embodiment.

[0034] Fig. 6 is an enlarged cross-sectional view of an optical functional layer in the direction of the light transmission axis of a polarizer among polarizing plates according to an embodiment.

[0035]

[0036] With reference to the attached drawings, the present invention is described in detail with respect to embodiments thereof so that those skilled in the art can easily implement the invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0037] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0038] In order to clearly explain the present invention in the drawings, parts unrelated to the description are omitted, and the same or similar components are given the same drawing reference numerals throughout the specification.

[0039] In this specification, "upper" and "lower" are defined based on the drawing, and depending on the perspective, "upper" may be changed to "lower" and "lower" may be changed to "upper", and reference to "on" or "on" may include not only directly above but also cases where another structure is intervening. On the other hand, reference to "directly on", "directly above", "formed directly" or "formed in direct contact with" means that no other structure is intervening.

[0040] In this specification, the “in-plane phase difference (Re)” is a value at a wavelength of 550 nm and is expressed by the following formula A:

[0041] <Formula A>

[0042] Re = (nx - ny) xd

[0043] (In the above formula A, nx and ny are the refractive indices of the protective layer in the slow axis direction and the fast axis direction, respectively, at a wavelength of 550 nm, and d is the thickness of the protective layer (unit: nm).)

[0044] As used herein, “(meth)acrylic” means acrylic and / or methacrylic.

[0045] In this specification, “refractive index” may be a value measured at a wavelength of 380 to 780 nm, specifically 550 nm.

[0046] In this specification, “light transmittance” may be a value measured at a wavelength of 380 to 780 nm, specifically 550 nm.

[0047] When describing a numerical range in this specification, “X to Y” means “X≤ and ≤Y”.

[0048] The polarizing plate of the present invention provides a visibility improvement effect even without a visibility improvement layer including resin layers having a pattern or a pattern on an interface.

[0049] The polarizing plate of the present invention provides a polarizing plate having excellent frontal brightness and anisotropic diffusion properties.

[0050] Here, "anisotropic diffusivity" refers to the ratio of the luminance measured at the side (60°, 0°) to the luminance measured at the front (0°, 0°) and the side (60°, 0°) when a polarizing plate is mounted on an optical display device and luminance is measured in white mode at the front (0°, 0°). The higher this ratio, the higher the anisotropic diffusivity, and the higher the anisotropic diffusivity, the better the effect of improving the contrast ratio and visibility at the side.

[0051] In the present invention, in order to offset the existing reflective polarization characteristics and maximize the asymmetric diffusion function, a suitable resin material was selected for the matrix and microstructure, and acicular particles were oriented within the microstructure. By unidirectionally orienting the acicular particles during the unstretched film manufacturing process and the stretching process, an optical functional layer having a composite function of improving visibility by integrating the asymmetric diffusion function within the optical functional layer was provided. The optical functional layer can be combined with a polarizer to ultimately produce a polarizing plate with maximized lateral viewing angles of a display product.

[0052] The polarizing plate of the present invention has no voids in the optical functional layer, so there may be no problem in implementing the optical effect of the optical functional layer.

[0053] A polarizing plate of one embodiment comprises a polarizer; and an optical functional layer laminated on one surface of the polarizer, wherein the optical functional layer comprises a first skin layer, a core layer, and a second skin layer laminated sequentially, wherein the core layer comprises a matrix and a plurality of microstructures dispersed in the matrix, and wherein at least some of the plurality of microstructures comprise a first resin and acicular particles oriented in one direction and surface-treated within the first resin, and wherein the optical functional layer has a ratio of the following formula 1 of 0.3 to 0.82:

[0054] [Formula 1]

[0055] ratio = b / (a + b + c)

[0056] (In the above equation 1,

[0057] a is the thickness of the first skin layer,

[0058] b is the thickness of the core layer,

[0059] c is the thickness of the second skin layer,

[0060] The units of a, b and c are each ㎛).

[0061] As described below, the optical functional layer can be manufactured by stretching. The surface-treated needle-shaped particles can reduce void generation during stretching by increasing compatibility between the first resin and the needle-shaped particles.

[0062] The optical functional layer satisfies the above formula 1. The above formula 1 serves as a criterion for determining whether the optical functional layer including the plurality of microstructures has excellent frontal luminance and anisotropic diffusion properties. By satisfying the above formula 1, the optical functional layer can have excellent frontal luminance and anisotropic diffusion properties.

[0063] Hereinafter, a polarizing plate according to one embodiment of the present invention will be described.

[0064] The polarizing plate has a polarizer and an optical functional layer.

[0065] The optical functional layer may have a light transmittance of 95% or more, for example, 96 to 100%. In the above range, it may be used as a polarizing plate on the viewing side.

[0066] optical functional layer

[0067] The optical functional layer is laminated on the light-emitting surface of the polarizer. The above-mentioned 'light-emitting surface' is the surface through which the internal light of the backlight unit reaches the polarizer and is emitted from the polarizer.

[0068] The upper and lower surfaces of the optical functional layer are each entirely flat and unpatterned. Nevertheless, the optical functional layer can improve visibility and / or contrast ratio and / or brightness from the front and side. This can help improve the manufacturing process of the polarizing plate and provide a thinner film, as it does not require an optical pattern or pattern layer.

[0069] The optical functional layer includes a first skin layer, a core layer, and a second skin layer, which are sequentially laminated.

[0070] core layer

[0071] The core layer contains anisotropic diffusing particles.

[0072] Anisotropic diffusing particles include acicular particles. The acicular particles can exhibit particularly excellent visibility and contrast ratio enhancement effects by utilizing the fact that the degree to which they diffuse light incident from a backlight unit (preferably a polarizer) varies depending on the refractive index and orientation of the particles.

[0073] A detailed description of the needle-shaped particles is provided.

[0074] Figure 2 is a schematic cross-sectional view of a needle-shaped particle.

[0075] The acicular particle may be a particle having a length L and a predetermined cross-sectional diameter D, and the cross-sectional diameter D may not be uniform throughout the length L but instead decreases toward both ends of the acicular particle. The acicular particle having an inhomogeneous thickness may exhibit optical anisotropy, thereby causing light incident from a polarizer to be emitted in different directions when passing through the acicular particle.

[0076] Figure 2 illustrates a case where the cross-sectional diameter of a needle-shaped particle decreases from the center to both ends. However, depending on the manufacturing method of the needle-shaped particle, the cross-sectional diameter may be uniform toward one end, but decrease only toward one end.

[0077] It may be preferable that the acicular particles are acicular microparticles having a maximum length L in micrometers. Here, "a value in micrometers" means that the length L is at least 1 ㎛ or more. This can help improve the contrast ratio and brightness by facilitating the orientation of the acicular microparticles among the microstructures in the present invention. Nanoparticles (e.g., nanorods, acicular nanoparticles) having a length L in nanometers may not be easy to orient themselves in the present invention, so it may not be easy to obtain the effects of the present invention, and if they are included in an excessive amount to provide the same effect, optical properties such as light transmittance and haze may not be good.

[0078] In one specific example, the length L may be 10 to 50 μm, for example, 10 to 30 μm, or 15 to 28 μm. Within this range, the orientation of the needle-shaped particles in the present invention is facilitated, which may help improve contrast ratio and brightness.

[0079] In one specific example, the cross-sectional diameter D may be 0.5 to 2.0 μm, preferably 1 to 2.0 μm. In this range, the aspect ratio may increase, thereby allowing a lateral diffusion effect. The "cross-sectional diameter" may refer to the cross-sectional diameter of the acicular particles, and may refer to the maximum diameter measured at the cross-section among the acicular particles.

[0080] In one specific example, the cross-section of the needle-shaped particle may be circular, elliptical, or the like.

[0081] The acicular particles may have an average aspect ratio of 5 or more. Within this range, it may be easy to provide the contrast ratio and brightness improvement effects of the present invention. Preferably, the average aspect ratio may be 5 to 60, 10 to 50, and more preferably 10 to 18. The "average aspect ratio" refers to the average value of the aspect ratios measured for each acicular particle, and the "aspect ratio" refers to the ratio of the length to the maximum cross-sectional diameter of the acicular particles.

[0082] The needle-shaped particles may have a refractive index of 1.5 to 2.2, preferably 1.6 to 1.8, and more preferably 1.65 to 1.7. Within this range, the particles may have an appropriate refractive index relative to the matrix described below, thereby helping to improve contrast ratio and visibility.

[0083] The needle-like particles can be organic particles, inorganic particles, organic-inorganic particles, etc. For example, needle-like particles include metal oxides such as titanium oxide (e.g., TiO2), zirconium oxide (e.g., ZrO2), zinc oxide (e.g., ZnO), calcium carbonate (CaCO3), boehmite, aluminum borate (e.g., AlBO3), calcium silicate (e.g., CaSiO3, wollastonite), magnesium sulfate (MgSO4), magnesium sulfate hydrate (e.g., MgSO 4ㆍ 7H2O), potassium titanate (e.g. K2Ti8O 17 ) may be particles formed of one or more of metal compounds such as silica, inorganic particles such as glass, and organic particles such as synthetic resin. Preferably, needle-shaped particles formed of calcium carbonate can easily implement the effects of the present invention and be easily manufactured.

[0084] The acicular particles are surface-modified. The surface-modified acicular particles can improve the optical properties of the optical functional layer by enhancing compatibility with the first resin and particle dispersibility among the microstructures, and can prevent aggregation of the acicular particles, thereby facilitating the implementation of the effects of the present invention. In addition, the surface modification can increase compatibility between the acicular particles and the first resin during stretching, thereby reducing void formation during stretching.

[0085] More than 50% of the total surface area of ​​the above-mentioned needle-shaped particles, for example, 60% to 100%, or 60% to 95%, can be surface-modified. Within this range, the effects of improving compatibility and dispersibility can be obtained.

[0086] In one specific example, the surface of the needle-shaped particles may be surface-modified with a silane-based compound. Preferably, the needle-shaped particles are surface-treated with at least one of a silane having a vinyl group and a silane-based compound having an epoxy group, thereby achieving excellent compatibility with the first resin described below and excellent dispersibility.

[0087] The above-mentioned silane compound having a vinyl group may include at least one vinylalkoxysilane including vinyltrimethoxysilane, vinyltriethoxysilane, etc.

[0088] The silane compound having the above epoxy group may include at least one of epoxycyclohexylmethyltrimethoxysilane, epoxycyclohexylmethyltriethoxysilane, epoxycyclohexylethyltrimethoxysilane, and epoxycyclohexylethyltriethoxysilane.

[0089] According to one embodiment, the needle-shaped particles may be contained in an amount of 90% or more, for example, 95% to 100%, or 100%, of the total anisotropic diffusion particles contained in the core layer. Within this range, the effects of the present invention may be easily realized. Here, '%' refers to the ratio of the weight of the needle-shaped particles to the weight of the total anisotropic diffusion particles contained in the core layer.

[0090] Anisotropic diffusion particles, preferably needle-shaped particles, may be contained in the core layer at 1 wt% to 30 wt%, for example, 1 wt% to 15 wt%, 1 wt% to 10 wt%, or 1 wt% to 5 wt%. Within the above range, the effect of improving contrast ratio and brightness can be obtained, and the effect of preventing the problem of the haze of the polarizing plate increasing due to excessive inclusion can be prevented.

[0091] In the present invention, anisotropic diffusion particles, for example, needle-shaped particles, are included in a core layer, but instead of including the anisotropic diffusion particles in a matrix forming the core layer, a plurality of microstructures including the anisotropic diffusion particles, for example, needle-shaped particles, are included in the matrix. The anisotropic diffusion particles in the microstructures are oriented in one direction. This improves the arrangement of the needle-shaped particles in a specific direction (for example, the stretching direction during the production of an optical functional layer) compared to a polarizing plate including anisotropic diffusion particles in a matrix, ultimately improving the anisotropic diffusion effect and further providing the effect of improving the contrast ratio.

[0092] According to one embodiment, the core layer comprises a matrix and a plurality of microstructures dispersed in the matrix, at least some of the plurality of microstructures comprising a first resin and needle-shaped particles oriented in one direction within the first resin, and the matrix comprises a second resin.

[0093] The matrix enhances the mechanical strength of the optically functional layer and supports the microstructures formed during their formation. Furthermore, the matrix can also enhance frontal luminance and anisotropic diffusion.

[0094] The microstructure comprises a first resin and a plurality of surface-modified acicular particles oriented in one direction within the first resin. For example, the first resin can form the shape of the microstructure and, during the manufacture of the microstructure, can orient the anisotropically diffusing particles in one direction. Furthermore, the first resin can also serve to enhance frontal brightness and anisotropic diffusivity. The microstructure can be oriented so that the acicular particles are well-oriented by first capturing them within the first resin.

[0095] The microstructure may have a major axis direction and a minor axis direction (wherein the major axis length is longer than the minor axis length), a cross-section in the major axis direction may be elliptical or amorphous, and a cross-section in the minor axis direction may be circular, elliptical, or amorphous. At this time, the length of the major axis direction of the microstructure may be equal to or greater than the longest length of the acicular particles, and the length of the major axis direction of the microstructure may be 3 µm or more, for example, 3 µm to 30 µm, or 5 µm to 25 µm, and the length of the minor axis direction of the microstructure may be equal to or greater than the cross-sectional diameter of the acicular particles, and the length of the minor axis direction of the microstructure may be 2 µm or less, for example, 0.1 µm to 2 µm, or 0.2 µm to 1.5 µm. In the above range, the acicular particles may be easily accommodated.

[0096] The microstructure may comprise 60 to 99 wt%, for example 70 to 99 wt%, 80 to 99 wt%, of the first resin, and 1 to 40 wt%, for example 1 to 30 wt%, 1 to 20 wt%, of the surface-modified acicular particles. In the above range, the microstructure can be easily manufactured, and there may also be an effect of improving the contrast ratio due to the acicular particles.

[0097] In one specific example, the needle-shaped particles may be included in multiples of one or more types of microstructures, for example, two or more types.

[0098] The matrix comprises a second resin, and the microstructure comprises a first resin.

[0099] The above first resin may include at least one type of polycyclohexylenedimethylene terephthalate resin.

[0100] For example, the second resin may include at least one of a polyethylene terephthalate (PET) resin and a polyethylene naphthalate (PEN) resin.

[0101] According to one embodiment, the first resin may be a polycyclohexylene dimethylene terephthalate (PCTG) resin, and the second resin may be a polyethylene terephthalate (PET) resin. When the optical functional layer includes a microstructure made of the first resin and a matrix including the second resin, improvements in frontal brightness and anisotropic diffusion may be significant.

[0102] According to one embodiment, the first resin has a refractive index of 1.5 to 1.6, and the second resin has a refractive index higher than that of the first resin, which may be about 1.6 to 1.7. In this range, refractive index matching between the matrix and the microstructure may be facilitated, and the visibility improvement effect may be further enhanced.

[0103] According to one embodiment, the polycyclohexylenedimethylene terephthalate (PCTG) resin may be included in the first resin at 95 wt% or more, for example, 99 to 100 wt%.

[0104] The matrix in the core layer may be included in an amount of 50 to 95 wt%, for example, 60 to 90 wt%, and the microstructure may be included in an amount of 5 to 50 wt%, for example, 10 to 40 wt%. In this range, frontal brightness and anisotropic diffusion may be improved.

[0105] The microstructures in the core layer may be randomly dispersed within the matrix. However, the microstructures may be oriented within the matrix in the same direction as the orientation direction of the needle-shaped particles.

[0106] According to one embodiment, the microstructure may be, for example, an elliptical cross-section having a major axis and a minor axis in the thickness direction.

[0107] Figure 1 is a conceptual diagram of a polarizing plate according to one implementation.

[0108] Referring to FIG. 1, a polarizing plate includes a polarizer (100) and an optical functional layer (200) laminated on one surface of the polarizer (100). The optical functional layer (200) includes a matrix (210) and a microstructure (220). The microstructure (220) includes a first resin (221) and needle-shaped particles (222).

[0109] Referring to FIG. 1, the light absorption axis direction (indicated by the X-axis in FIG. 1) of the polarizer (100) may be substantially the same direction as the orientation direction of the needle-shaped particles (222) in the microstructure (220) of the optical functional layer (200).

[0110] Here, 'substantially the same direction' means that when the light absorption axis direction of the polarizer is 0°, the orientation direction of the anisotropic diffusing particles is between -5 and +5°, for example, between -3 and +3°, or 0°. In one specific example, the light absorption axis direction of the polarizer is the machine direction (MD) of the polarizer. That is, in Fig. 1, the X-axis is MD, and the Y-axis is TD.

[0111] In one specific example, the core layer may have a thickness of 0.5 to 80 μm, preferably 0.5 to 50 μm, more preferably 1 to 20 μm.

[0112] First skin layer

[0113] The above first skin layer is included in the optical functional layer to maintain film running stability, protect the core layer from external damage, and maintain surface gloss, thereby providing an improvement in optical properties such as transmittance.

[0114] The above first skin layer may include at least one of polyethylene terephthalate (PET) resin and polyethylene naphthalate (PEN) resin.

[0115] The above first skin layer may have a thickness of 1 to 50 μm, preferably 1 to 30 μm, and more preferably 1 to 20 μm.

[0116] Second skin layer

[0117] The above second skin layer is included in the optical functional layer to maintain film running stability, protect the core layer from external damage, and maintain surface gloss, thereby providing an improvement in optical properties such as transmittance.

[0118] The second skin layer may include at least one of polyethylene terephthalate (PET) resin and polyethylene naphthalate (PEN) resin.

[0119] The second skin layer may have a thickness equal to or different from that of the first skin layer, and may have a thickness of 1 to 50 μm, preferably 1 to 30 μm, and more preferably 1 to 20 μm.

[0120] Manufacturing of optical functional layers

[0121] The optical functional layer can be manufactured by introducing a mixture of surface-modified needle-shaped particles and a first resin into an extrusion unit to manufacture a high-concentration master batch, mixing the high-concentration master batch and the first resin to manufacture a composition for a core layer, co-extruding the composition for a core layer, the composition for a first skin layer, and the composition for a second skin layer to manufacture a sheet, and stretching the sheet at a predetermined stretching ratio.

[0122] In one embodiment, the stretching may include stretching from 1 to 6 times in the mechanical direction of the sheet and from 1 to 5 times in the width direction of the sheet.

[0123] In one specific example, the core layer, the first skin layer, and the second skin layer may have the same elongation direction.

[0124] In addition to the optical functional layer, the polarizing plate may further include one or more polarizers, a protective layer (including a phase difference layer), an adhesive layer, and / or an adhesive layer, a functional film (including a functional coating layer), etc.

[0125] (i) Polarizer

[0126] A polarizer is a linear light absorption 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 the one direction.

[0127] The polarizer may be a polarizer manufactured by dyeing and stretching a polyvinyl alcohol (PVA) film, or a polyene polarizer manufactured by dehydrating a polyvinyl alcohol film.

[0128] The polarizer may have a thickness of 50 μm or less, for example, 5 μm to 30 μm. Within this range, melting and breakage of the film may be avoided during film stretching.

[0129] (ii) protective layer

[0130] A protective layer may be included in a polarizing plate to protect the polarizer or increase the mechanical strength of the polarizing plate. The protective layer may also be an adherend forming an optically functional layer.

[0131] The protective layer may include a transparent substrate. The transparent substrate may have a higher or lower refractive index than the optically functional layer. Preferably, the transparent substrate has a higher refractive index than the optically functional layer. This can help improve contrast ratio and brightness.

[0132] The transparent substrate may include an optically transparent resin film having a light incident surface and a light exit surface opposite the light incident surface. The transparent substrate may be formed of a single layer of resin film, but may also be formed by laminating a plurality of resin films. The resin may include at least one of a cellulose ester resin including triacetyl cellulose (TAC) or the like, a cyclic polyolefin resin including amorphous cyclic polyolefin (COP) or the like, a polycarbonate resin, a polyester resin including polyethylene terephthalate (PET) or the like, a polyethersulfone resin, a polysulfone resin, a polyamide resin, a polyimide resin, an acyclic-polyolefin resin, a polyacrylate resin including polymethyl methacrylate resin, a polyvinyl alcohol resin, a polyvinyl chloride resin, and a polyvinylidene chloride resin, but is not limited thereto. Preferably, the transparent substrate includes a polyester resin including polyethylene terephthalate (PET), etc., thereby further enhancing the contrast ratio and brightness improvement effect.

[0133] The transparent substrate may have a haze of 30% or less, specifically 2% to 30%, and a light transmittance of 90% or more, specifically 95% to 100%. Within the above range, the transparent substrate may be applied to a polarizing plate.

[0134] The thickness of the transparent substrate may be 5 μm to 200 μm, for example, 30 μm to 120 μm. Within the above range, it can be used in a polarizing plate.

[0135] A functional layer may be further laminated on at least one side of the transparent substrate. The functional layer may be a primer layer, an anti-glare layer, an anti-reflection layer, a low-refractive index layer, a high-refractive index layer, a hard coating layer, an anti-fingerprint layer, etc.

[0136] The protective layer may be an isotropic film with virtually no phase difference, but may have a certain range of in-plane directional phase difference, which may provide additional functionality when combined with a polarizing plate.

[0137] In one specific embodiment, the protective layer may have an in-plane retardation of 3,000 nm or more at a wavelength of 550 nm. In this range, when combined with an optical functional layer, it may help improve contrast ratio and / or brightness. Preferably, the in-plane retardation may be 4,000 nm or more, 8,000 nm or more, specifically 10,000 nm or more, more specifically greater than 10,000 nm, and more specifically 10,100 nm to 30,000 nm, or 10,100 nm to 15,000 nm.

[0138] In other embodiments, the protective layer may have an in-plane retardation of less than 3,000 nm at a wavelength of 550 nm. For example, the protective layer may have an in-plane retardation of 0 nm to 1,000 nm, or 10 nm to 500 nm at a wavelength of 550 nm.

[0139] The protective layer may be a first protective layer, a second protective layer, or a third protective layer, as described below.

[0140] (iii) adhesive layer and / or adhesive layer;

[0141] The adhesive layer and / or bonding layer can bond or adhere a polarizer, an optical functional layer, a protective layer, a functional film, etc.

[0142] The adhesive layer may be formed of a conventional composition known to those skilled in the art. For example, the adhesive layer may be a (meth)acrylic, epoxy, silicone, urethane, epoxy (meth)acrylic, or urethane (meth)acrylic adhesive layer. For example, the adhesive layer may be a pressure sensitive adhesive (PSA) layer.

[0143] The adhesive layer may be formed of a conventional composition known to those skilled in the art. For example, the adhesive layer may be formed of a water-based adhesive, a photocurable adhesive, or the like.

[0144] (iv) Functional film

[0145] A functional film is not necessarily included in a polarizing plate, but may be a film that provides additional functions when included in a polarizing plate.

[0146] The functional film or functional coating layer may be an anti-glare film, an anti-reflection film, an ultra-low-reflection film, a low-refractive index film, a high-refractive index film, or an anti-fingerprint film.

[0147] According to one implementation, the polarizing plate may include a polarizer; and an optical functional layer laminated on a light-emitting surface of the polarizer.

[0148] According to another embodiment, the polarizing plate may include a polarizer; and an optical functional layer and a first protective layer sequentially laminated on a light-emitting surface of the polarizer.

[0149] According to another embodiment, the polarizing plate may include a polarizer; an optical functional layer and a functional coating layer sequentially laminated on the light-emitting surface of the polarizer.

[0150] According to another embodiment, the polarizing plate may include a polarizer; a second protective layer, an optical functional layer, and a first protective layer sequentially laminated on the light-emitting surface of the polarizer.

[0151] According to another embodiment, the polarizing plate may include a polarizer; a second protective layer, an optical functional layer, and a first protective layer sequentially laminated on a light-emitting surface of the polarizer; and a third protective layer laminated on a light-incident surface of the polarizer.

[0152] Each layer of the above-described polarizing plate can be laminated by an adhesive layer, an adhesive layer, etc., if necessary.

[0153] The optical display device of the present invention includes the polarizing plate of the present invention.

[0154] In one specific example, the optical display device of the present invention may include the polarizing plate of the present invention as a viewer-side polarizing plate for a liquid crystal panel. The "viewer-side polarizing plate" is a polarizing plate that is positioned opposite the screen side, i.e., the light source side, of the liquid crystal panel.

[0155] In one specific example, the liquid crystal display device may sequentially stack a light-collecting backlight unit, a light source-side polarizing plate, a liquid crystal panel, and a viewer-side polarizing plate, wherein the viewer-side polarizing plate may include the polarizing plate of the present invention. The "light source-side polarizing plate" is a polarizing plate disposed on the light source side. The liquid crystal panel may adopt, but is not limited to, a VA (vertical alignment) mode, an IPS mode, a PVA (patterned vertical alignment) mode, or an S-PVA (super-patterned vertical alignment) mode.

[0156] The optical display device may be a foldable or flexible optical display device or a non-foldable or non-flexible optical display device.

[0157]

[0158] Hereinafter, the configuration and operation of the present invention will be described in more detail through preferred embodiments of the present invention. However, the following examples are intended to aid understanding of the present invention, and the scope of the present invention is not limited to the following examples.

[0159]

[0160] Example 1

[0161] (1) 100 parts by weight of a mixture of CaCO3 particles (CaCO3: needle-shaped anisotropic microparticles, length: 10 to 30 μm, cross-sectional diameter: 0.5 to 2.0 μm, Whiscal A, MARUO CALCIUM, refractive index: 1.68) was prepared, added to a methyl ethyl ketone solution containing vinyltriethoxysilane, reacted under room temperature conditions, and then dried in an oven at 90°C to remove the solvent, thereby preparing a mixture of CaCO3 needle-shaped particles surface-modified with vinyltriethoxysilane.

[0162] (2) A composition was prepared by mixing the mixture of the above-mentioned needle-shaped particles in a polycyclohexylenedimethylene terephthalate (PCTG, refractive index: 1.56, TAK) resin at a predetermined ratio, and the composition was injected into an extrusion unit to prepare a high-concentration master batch. At this time, the master batch contains 80 wt% of PCTG and 20 wt% of needle-shaped particles surface-modified with vinyltriethoxysilane.

[0163] (3) Polyethylene terephthalate (PET) resin was used as the matrix component. A composition for the core layer was prepared by mixing 80 wt% of PET resin and 20 wt% of the master batch prepared above. PET resin was used as the skin layer.

[0164] (4) The composition for the core layer and the PET resin for the skin layer were introduced into a coextruder and coextruded (coextrusion temperature: 250 to 270°C) to manufacture a sheet of a certain thickness (0.5 to 1 mm).

[0165] The above sheet was sequentially stretched 5 times in the mechanical direction of the sheet and 2 times in the width direction to produce an optical functional layer.

[0166] The optical functional layer includes a core layer, a first skin layer (PET resin layer) formed on one surface of the core layer, and a second skin layer (PET resin layer) formed on the other surface of the core layer, wherein the core layer includes a matrix made of PET resin, and a plurality of microstructures including CaCO3 particles impregnated in the matrix, oriented in one direction within a PCTG resin, and surface-treated with vinyltriethoxysilane. The core layer has a thickness of 9 μm, and the first skin layer and the second skin layer each have a thickness of 1 μm.

[0167] (5) A polyvinyl alcohol film was stretched 3 times in the mechanical direction of the film at 60°C, iodine was adsorbed, and then stretched 2.5 times in the mechanical direction of the film in a boric acid aqueous solution at 40°C to manufacture a polarizer (thickness: 13 μm, light transmittance: 44%).

[0168] (6) The optical functional layer was laminated on the upper surface of the manufactured polarizer, and a cyclic olefin polymer (COP) film was laminated on the lower surface using an adhesive, thereby manufacturing a polarizing plate in which the optical functional layer - polarizer - cyclic olefin polymer film were sequentially laminated.

[0169]

[0170] Example 2

[0171] A polarizing plate was manufactured in the same manner as in Example 1, except that the thicknesses of the core layer, the first skin layer, and the second skin layer were changed when manufacturing the optical functional layer in Example 1. The thickness of the core layer was 1 μm, and the thicknesses of the first skin layer and the second skin layer were each 1 μm.

[0172]

[0173] Example 3

[0174] A polarizing plate was manufactured in the same manner as in Example 1, except that the surface was modified with epoxycyclohexylethyl trimethoxysilane instead of vinyltriethoxysilane.

[0175]

[0176] Example 4

[0177] A polarizing plate was manufactured in the same manner as in Example 1, except that the surface was modified with epoxycyclohexylethyl trimethoxysilane instead of vinyltriethoxysilane in Example 2.

[0178]

[0179] Comparative Example 1

[0180] A polarizing plate was manufactured in the same manner as in Example 1, except that modification with vinyltriethoxysilane was not performed.

[0181]

[0182] Comparative Example 2

[0183] A polarizing plate was manufactured in the same manner as in Example 1, except that modification with vinyltriethoxysilane was not performed in Example 2.

[0184]

[0185] Comparative Example 3

[0186] A polarizing plate was manufactured in the same manner as in Example 1, except that the ratio of Formula 1 was changed by changing the thickness of the skin layer and the core layer without modifying with vinyltriethoxysilane.

[0187]

[0188] Comparative Example 4

[0189] A polarizing plate was manufactured in the same manner as in Example 1, except that the ratio of Equation 1 was changed by changing the thickness of the skin layer and the core layer in Example 1.

[0190]

[0191] Comparative Example 5

[0192] A polarizing plate was manufactured in the same manner as in Example 1, except that the ratio of Equation 1 was changed by changing the thickness of the skin layer and the core layer in Example 1.

[0193]

[0194] For the polarizing plates manufactured in the examples and comparative examples, a model for measuring the viewing angle below was manufactured and the physical properties shown in Table 1 below were evaluated.

[0195] A viewing-side polarizing plate was removed from a liquid crystal panel model UN55KS8000F (55 inches, Samsung Electronics TV), and a viewing-side polarizing plate was laminated with the polarizing plate manufactured in the examples and comparative examples to produce a model for measuring viewing angles. Among the models for measuring viewing angles, the light-source-side polarizing plate was laminated in the order of COP film - polarizer - PET film from the liquid crystal panel.

[0196]

[0197] The following properties were evaluated, and the results are shown in Table 1 below.

[0198] (1) Confirmation of microstructures within the optical functional layer:

[0199] For the optical functional layer manufactured in the example, the cross-section in the direction of the light absorption axis and light transmission axis of the polarizer was measured using SEM, and the results are shown in Figs. 3, 4, 5, and 6.

[0200] Fig. 3 is a cross-sectional view of an optical functional layer in the direction of the light absorption axis of a polarizer in a polarizing plate, and Fig. 4 is an enlarged cross-sectional view of an optical functional layer in the direction of the light absorption axis of a polarizer in a polarizing plate. Fig. 4 is a cross-sectional view of an optical functional layer in the direction of the light transmission axis of a polarizer in a polarizing plate, and Fig. 4 is an enlarged cross-sectional view of an optical functional layer in the direction of the light transmission axis of a polarizer in a polarizing plate.

[0201] As shown in FIGS. 3 and 4, it can be confirmed that the needle-shaped particles and microstructures including needle-shaped particles are oriented in one direction. As shown in FIGS. 5 and 6, it can be confirmed through the cross-section of the needle-shaped particles that the needle-shaped particles are oriented in the direction of the light absorption axis of the polarizer.

[0202] (2) Frontal luminance (unit: none): A liquid crystal display (LCD) including a single-sided edge-type LED light source (same configuration as a Samsung TV (55 inches, model name: UN55KS8000F) except for the configuration of the liquid crystal display module of the Examples and Comparative Examples) was manufactured by assembling an LED light source, a light guide plate, and a model for measuring the viewing angle. The luminance was measured at the front (0°, 0°) in a spherical coordinate system using EZCONTRAST X88RC (EZXL-176R-F422A4, ELDIM). The relative ratio of the luminance at the front (0°, 0°) measured by the polarizing plate of Reference Example 1 (a polarizing plate laminated in the order of COP film - polarizer - PET film) was calculated.

[0203] (3) Anisotropic diffusion (unit: none): A module for a liquid crystal display was manufactured using the same method as in (2). Luminance was measured in white mode at the front (0°, 0°) and side (60°, 0°) in a spherical coordinate system using EZCONTRAST X88RC (EZXL-176R-F422A4, ELDIM). The ratio of the luminance measured at the side (60°, 0°) to the luminance measured at the front (0°, 0°) in white mode was calculated.

[0204] (4) Unit reflectance (unit: %): The unit reflectance was obtained as SCI reflectance (%) using a colorimeter (Konica Minolta Model CM3600A) for each anisotropic diffusion film.

[0205] (5) Void occurrence level (unit: none): The occurrence level of voids in the optical functional layer was evaluated using SEM and scored from level 1 to level 10. A score from level 1 to level 10 indicates that more voids were generated in the optical functional layer.

[0206] Matrix microstructure, first resin modification, content of needle-shaped particles, ratio of formula 1, frontal luminance, anisotropic diffusion, single-piece reflectance, void generation level, Example 1, PETPCTG vinyltriethoxysilane 2%, 0.827917137, Example 2, PETPCTG vinyltriethoxysilane 2%, 0.338220137, Example 3, PETPCTG epoxysilane 2%, 0.828119103, Example 4, PETPCTG epoxysilane 2%, 0.33852393, Comparative Example 1, PETPCTG unmodified 2%, 0.8279171410, Comparative Example 2, PETPCTG unmodified 2%, 0.3380201410, Comparative Example 3, PETPCTG unmodified No 2% 0.7179171410 Comparative Example 4 PETPCTG Vinyltriethoxysilane 2% 0.257518128 Comparative Example 5 PETPCTG Vinyltriethoxysilane 2% 0.857225178

[0207]

[0208] *Particle content: Content of needle-shaped particles (CaCO3) in the core layer (weight%)

[0209]

[0210] As shown in Table 1 above, the polarizing plate of the embodiment has a visibility improvement effect even without the visibility improvement pattern itself or the visibility improvement layer having the pattern. The polarizing plate of the embodiment has both improved frontal luminance and anisotropic diffusion, has an excellent contrast ratio in frontal and side views, and has excellent compatibility between the first resin and the needle-shaped particles among the microstructures, so that no voids are generated.

[0211] On the other hand, the polarizing plate of the comparative example had voids and had poor frontal luminance and anisotropic diffusion properties.

[0212]

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

Claims

1. A polarizer; and an optical functional layer laminated on one surface of the polarizer, The optical functional layer includes a first skin layer, a core layer, and a second skin layer sequentially laminated, The core layer comprises a matrix and a plurality of microstructures dispersed in the matrix, and at least some of the plurality of microstructures comprise a core layer comprising a first resin and needle-shaped particles oriented in one direction and surface-treated within the first resin, The optical functional layer is a polarizing plate having a ratio of 0.3 to 0.82 in the following formula 1: [Formula 1] ratio = b / (a + b + c) (In the above equation 1, a is the thickness of the first skin layer, b is the thickness of the core layer, c is the thickness of the second skin layer, The units of a, b and c are each ㎛).

2. A polarizing plate according to claim 1, wherein the optical functional layer is a contrast ratio or brightness improvement layer.

3. A polarizing plate according to claim 1, wherein the upper and lower surfaces of the optical functional layer are each entirely flat.

4. A polarizing plate according to claim 1, wherein the needle-shaped particles are needle-shaped microparticles.

5. A polarizing plate according to claim 1, wherein the needle-shaped particles are formed of at least one of titanium oxide, zirconium oxide, zinc oxide, calcium carbonate, boehmite, aluminum borate, calcium silicate, magnesium sulfate, magnesium sulfate hydrate, and potassium titanate.

6. A polarizing plate according to claim 1, wherein the needle-shaped particles have an average aspect ratio of 5 to 60.

7. A polarizing plate according to claim 1, wherein the needle-shaped particles are contained in an amount of 1 to 30 wt% of the optical functional layer.

8. A polarizing plate according to claim 1, wherein the needle-shaped particles are included as a plurality of the microstructures.

9. A polarizing plate in the first paragraph, wherein the microstructure is a structure having a long-axis direction and a short-axis direction.

10. A polarizing plate in the first paragraph, wherein the microstructure is oriented in the matrix in the same direction as the orientation direction of the needle-shaped particles.

11. A polarizing plate in accordance with claim 1, wherein when the light absorption axis direction of the polarizer is 0°, the orientation direction of the needle-shaped particles is -5 to +5°.

12. A polarizing plate in the first paragraph, wherein the needle-shaped particles are surface-treated with at least one of a silane compound having a vinyl group and a silane compound having an epoxy group.

13. A polarizing plate according to claim 1, wherein the first resin comprises at least one type of polycyclohexylene dimethylene terephthalate resin.

14. A polarizing plate according to claim 1, wherein the matrix comprises a second resin, and the second resin comprises at least one of a polyethylene terephthalate (PET) resin and a polyethylene naphthalate (PEN) resin.

15. A polarizing plate in accordance with claim 1, wherein the core layer, the first skin layer, and the second skin layer have the same stretching direction.

16. A polarizing plate according to claim 1, wherein the matrix of the optical functional layer is included in an amount of 50 to 95 wt%, and the microstructure is included in an amount of 5 to 50 wt%.

17. A polarizing plate according to claim 1, wherein the polarizing plate comprises at least one of a protective layer, an adhesive layer, an adhesive layer, a functional film, and a functional coating layer.

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

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