Polarizing plate and optical display apparatus

Abstract

A polarizing plate and an optical display device including the same are disclosed. The polarizing plate includes a polarizer; and an optical functional layer formed on one surface of the polarizer, wherein the optical functional layer includes a first skin layer, a core layer, and a second skin layer. The core layer includes a matrix and a plurality of microstructures dispersed in the matrix, and at least some of the plurality of microstructures include a first resin and needle-like particles aligned in one direction and subjected to surface treatment within the first resin. The optical functional layer has a ratio of 0.3 to 0.82 according to Equation 1.

Description

[Technical Field]

[0001] Relevant documents for patent applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2024-0095422, filed on July 19, 2024, with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference.

[0003] The present invention relates to a polarizing plate and an optical display device. [Previous Technology]

[0004] The liquid crystal display has a structure in which a viewer-side polarizing plate, a liquid crystal panel, and a light source-side polarizing plate are stacked in sequence.

[0005] Despite its many advantages, liquid crystal displays (LCDs) suffer from low visibility and brightness on the lateral side. To address these issues, a method has been proposed that provides a visibility enhancement layer to the viewer-side polarizer, comprising two resin layers with different refractive indices and a pattern at the interface between the resin layers. However, the visibility enhancement layer requires an additional patterning process, leading to reduced yield and increased material costs. Therefore, there is a need for polarizers capable of improving visibility without requiring such a visibility enhancement layer.

[0006] The background technology of the present invention is disclosed in Korean Patent Publication No. 10-2018-0047569, etc. [Summary of the Invention]

[0007] One object of the present invention is to provide a polarizing plate that can enhance visibility without a visibility enhancement pattern or a visibility enhancement layer having such a pattern.

[0008] Another object of the present invention is to provide a polarizing plate that can provide improved characteristics in terms of both front brightness and anisotropic diffusion rate.

[0009] Another object of the present invention is to provide a polarizing plate that can provide improved characteristics in terms of both frontal contrast and lateral contrast.

[0010] Another object of the present invention is to provide a polarizing plate that exhibits good compatibility between a first resin and needle-like microparticles in a microstructure.

[0011] According to one aspect of the present invention, a polarizing plate is provided.

[0012] The polarizing plate includes: a polarizer; and an optical functional layer formed on a surface of the polarizer, wherein the optical functional layer includes a first skin layer, a core layer and a second skin layer, the core layer includes a matrix and a plurality of microstructures dispersed in the matrix, and at least some of the plurality of microstructures include a first resin and needle-like microparticles aligned in one direction and subjected to surface treatment within the first resin, the optical functional layer having a ratio of 0.3 to 0.82 according to Equation 1: [Equation 1] Ratio = b / (a + b + c) where a represents the thickness of the first skin layer, b represents the thickness of the core layer and c represents the thickness of the second skin layer, wherein the thicknesses of a, b and c are each in micrometers.

[0013] According to another aspect of the present invention, an optical display device is provided.

[0014] The optical display device includes a polarizing plate according to the present invention.

[0015] Embodiments of the present invention provide a polarizing plate that can enhance visibility without a visibility enhancement pattern or a visibility enhancement layer having such a pattern.

[0016] Embodiments of the present invention provide a polarizing plate that can improve both front brightness and anisotropic diffusion rate.

[0017] Embodiments of the present invention provide a polarizing plate that can improve both frontal contrast and lateral contrast.

[0018] Embodiments of the present invention provide a polarizing plate that exhibits good compatibility between a first resin and needle-like microparticles in a microstructure.

Implementation Method

[0020] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, enabling those skilled in the art to readily implement the present invention. It should be understood that the present invention can be implemented in different ways and is not limited to the following embodiments.

[0021] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the invention. Unless the context clearly indicates otherwise, the singular forms "a / an" and "the" as used herein are intended to include the plural forms as well.

[0022] For clarity, parts irrelevant to the description will be omitted in this document. Throughout the specification, the same components will be represented by the same figure symbols.

[0023] In this document, spatially relative terms such as "upper part" and "lower part" are defined with reference to the accompanying drawings. Therefore, it should be understood that the term "upper surface" can be used interchangeably with the term "lower surface". When an element such as a layer or film is said to be placed "on" another element, it may be placed directly on the other element, or there may be intervening elements. On the other hand, when an element is said to be "directly placed on", "directly formed on", or "formed as directly adjacent" to another element, there are no intervening elements.

[0024] In this paper, “in-plane delay (Re)” refers to the value measured at a wavelength of 550 nanometers and is represented by Equation A: [Equation A] Re = (nx – ny) × d where nx and ny are the refractive indices of the protective layer measured at a wavelength of 550 nanometers in the slow axis and fast axis directions, respectively, and d is the thickness of the protective layer (unit: nanometers).

[0025] In this document, "(meth)acrylic acid" refers to acrylic acid and / or methacrylic acid.

[0026] In this document, "refractive index" may refer to the value measured at a wavelength of 380 nanometers to 780 nanometers, particularly at a wavelength of 550 nanometers.

[0027] In this document, "transmittance" may refer to the value measured at a wavelength of 380 nanometers to 780 nanometers, particularly at a wavelength of 550 nanometers.

[0028] As used in this document to indicate a specific numerical range, "X to Y" means "above X and below Y (X ≤ and ≤ Y)".

[0029] The polarizing plate according to the invention provides improved visibility in the absence of a visibility enhancement pattern or a visibility enhancement layer comprising a resin layer having a visibility enhancement pattern between interfaces.

[0030] The polarizing plate according to the present invention provides good properties in terms of front brightness and anisotropic diffusion rate.

[0031] In this document, "anisotropic diffusion rate" refers to the ratio of the lateral brightness of an optical display device with a polarizing plate to the front brightness of the optical display device, wherein the front brightness and lateral brightness are measured in white mode on the front side (0°, 0°) and the lateral side (60°, 0°), respectively. A higher ratio indicates a higher anisotropic diffusion rate, meaning that the optical display device has better lateral contrast and better visibility.

[0032] In this invention, to counteract the reflective polarization characteristics of a typical polarizer while maximizing asymmetric diffusion, a resin material suitable for the matrix and microstructure is selected, and needle-like particles are aligned within the microstructure. Furthermore, the needle-like particles are aligned in one direction during the preparation and stretching of the unstretched film, thereby providing a multifunctional optical layer that combines visibility enhancement and asymmetric diffusion. This optical layer can be combined with a polarizer to fabricate a polarizer capable of maximizing the lateral viewing angle of the final display product.

[0033] In the polarizing plate according to the present invention, the optical functional layer is free of voids, thereby effectively realizing its optical effect.

[0034] According to one aspect of the present invention, a polarizing plate includes: a polarizer; and an optical functional layer formed on a surface of the polarizer, wherein the optical functional layer includes a first skin layer, a core layer and a second skin layer, the core layer includes a matrix and a plurality of microstructures dispersed in the matrix, and at least some of the plurality of microstructures include a first resin and needle-like microparticles aligned in one direction and subjected to surface treatment within the first resin, the optical functional layer having a ratio of 0.3 to 0.82 according to Equation 1: [Equation 1] Ratio = b / (a + b + c) where a represents the thickness of the first skin layer, b represents the thickness of the core layer and c represents the thickness of the second skin layer, wherein the thicknesses of a, b and c are each in micrometers.

[0035] As described below, the optical functional layer can be formed by stretching. The surface-treated needle-like particles can suppress the formation of voids during stretching by improving the compatibility between the first resin and the needle-like particles.

[0036] The optical functional layer satisfies Equation 1. Equation 1 is a standard used to determine whether an optical functional layer comprising multiple microstructures has good frontal brightness and anisotropic diffusion. Since the optical functional layer satisfies Equation 1, the polarizer can exhibit good frontal brightness and anisotropic diffusion.

[0037] Next, a polarizing plate according to an embodiment of the present invention will be described in detail.

[0038] The polarizing plate includes a polarizer and an optical functional layer.

[0039] The optical functional layer may have a light transmittance of 95% or higher, for example, 96% to 100%. Within this range, the polarizing plate may be used as a viewer-side polarizing plate.

[0040] Optical Functional Layer

[0041] An optical functional layer is stacked on the light emitting surface of the polarizer. Here, "light emitting surface" refers to the surface of the polarizer from which light emitted from the backlight unit and which has entered the interior of the polarizer is emitted from the polarizer.

[0042] The upper and lower surfaces of the optical functional layer are each completely flat and without patterns. Nevertheless, the optical functional layer can improve frontal and lateral visibility and / or contrast and / or brightness. This structure can help improve the manufacturability of the polarizing plate, while reducing the thickness of the polarizing plate by eliminating the use of optical patterns or patterned layers.

[0043] The optical functional layer includes a first epidermal layer, a core layer, and a second epidermal layer stacked in sequence.

[0044] Core Layer

[0045] The core layer includes anisotropic diffused particles.

[0046] Anisotropic diffused particles include needle-like particles. Needle-like particles can particularly effectively improve visibility and contrast by providing varying degrees of diffusion (depending on the particle's refractive index and alignment) of light incident from the backlight unit (preferably a polarizer).

[0047] The needle-like particles will be described in detail below.

[0048] Figure 2 is a schematic cross-sectional view of needle-like particles.

[0049] The needle-like particles may have a predetermined length L and a predetermined cross-sectional diameter D, wherein the diameter D decreases toward both ends of the particle rather than being uniform along the length L of the particle. The needle-like particles with non-uniform thickness exhibit optical anisotropy, thereby allowing light incident from the polarizer to travel in different directions as it passes through the needle-like particles.

[0050] Figure 2 shows a needle-like particle with a cross-sectional diameter that decreases from the center of the needle-like particle toward both ends. However, it should be understood that the invention is not limited thereto, and the cross-sectional diameter of the needle-like particle may be uniform towards one end of the needle-like particle and decrease towards the other end, depending on the method of manufacturing the needle-like particle.

[0051] Preferably, the needle-like particles are needle-like particles having a maximum length L within the micrometer range. Here, "having a maximum length within the micrometer range" means that the length L is greater than or equal to 1 micrometer. This structure can help improve contrast and brightness by promoting the alignment of the needle-like particles in the microstructure. Since nanoparticles with a length L within the nanometer range (e.g., nanorods, needle-like nanoparticles, etc.) are difficult to align in one direction within the microstructure, such nanoparticles can make it difficult to achieve the effects of the present invention, and an excessive number of nanoparticles to provide the same effect as needle-like particles will lead to the deterioration of optical properties (such as light transmittance, haze, etc.).

[0052] According to one embodiment, the needle-like particles may have a length L of 10 micrometers to 50 micrometers, for example, 10 micrometers to 30 micrometers, specifically 15 micrometers to 28 micrometers. Within this range, the needle-like particles can be easily aligned within the microstructure, thereby aiding in the improvement of contrast and brightness.

[0053] According to one embodiment, the needle-like particles may have a cross-sectional diameter D of 0.5 micrometers to 2.0 micrometers, preferably 1 micrometer to 2.0 micrometers. Within this range, the needle-like particles may provide a lateral diffusion effect due to the increase in their aspect ratio. Here, "cross-sectional diameter" may refer to the maximum diameter measured in the cross-section of the needle-like particles.

[0054] According to one embodiment, the needle-like particles may have a circular or elliptical shape in cross-section.

[0055] The needle-like particles may have an average aspect ratio of 5 or greater. Within this range, the needle-like particles can readily ensure the improvements in contrast and brightness described herein. Preferably, the needle-like particles have an average aspect ratio of 5 to 60, more preferably 10 to 50, and even more preferably 10 to 18. Here, "average aspect ratio" refers to the average of the aspect ratios measured for each individual needle-like particle, and "aspect ratio" refers to the ratio of the length of the needle-like particle to the maximum cross-sectional diameter of the needle-like particle.

[0056] The needle-like particles may have a refractive index of 1.5 to 2.2, more preferably 1.6 to 1.8, and even more preferably 1.65 to 1.7. Within this range, the needle-like particles may have an appropriate refractive index level relative to the matrix described below, thereby contributing to the improvement of contrast and visibility.

[0057] The needle-like particles may include organic particles, inorganic particles, organic-inorganic mixed particles, etc. For example, the needle-like particles may be particles formed from at least one of the following: metal oxides, such as titanium oxide (e.g., TiO2), zirconium oxide (e.g., ZrO2), and zinc oxide (e.g., ZnO); metal compounds, such as calcium carbonate (CaCO3), boehmite, aluminum borate (e.g., AlBO3), calcium silicate (e.g., CaSiO3, wollastonite, etc.), magnesium sulfate (MgSO4), magnesium sulfate hydrate (e.g., MgSO4∙7H2O), and potassium titanate (e.g., K2Ti8O17); inorganic particles, such as glass; and organic particles, such as synthetic resins. Preferably, the needle-like particles are formed from calcium carbonate to promote the realization of the effects of the present invention and its manufacture.

[0058] The needle-like microparticles undergo surface modification. Surface modification of the needle-like microparticles can improve the optical properties of the optical functional layer by further improving the compatibility between the needle-like microparticles and the first resin in the microstructure, and can promote the realization of the effects of the present invention by preventing the aggregation of needle-like microparticles. In addition, surface modification of the needle-like microparticles can improve the compatibility between the needle-like microparticles and the first resin during stretching, thereby suppressing the generation of voids during stretching.

[0059] 50% or more (e.g., 60% to 100% or 60% to 95%) of the total surface area of ​​the needle-like particles can undergo surface modification. Within this range, the needle-like particles can have improved compatibility and dispersibility.

[0060] In one embodiment, the needle-like particles may be surface-modified with a silane compound. Preferably, the needle-like particles are surface-modified with at least one of a vinyl silane compound or an epoxy silane compound to ensure good compatibility and good dispersibility with the first resin described below.

[0061] A vinyl silane compound may include at least one vinylalkoxy silane compound, including vinyltrimethoxysilane, vinyltriethoxysilane, etc.

[0062] Silane compounds having an epoxy group may include at least one of cyclohexylmethyltrimethoxysilane, cyclohexylmethyltriethoxysilane, cyclohexylethyltrimethoxysilane, or cyclohexylmethyltriethoxysilane.

[0063] According to one embodiment, the needle-like particles may be present in an amount of 90% or more, for example, from 95% to 100%, specifically 100%, based on the total amount of anisotropically diffused particles contained in the core layer. Within this range, the needle-like particles can promote the achievement of the effects of the present invention. Here, "%" refers to the weight of needle-like particles based on the total weight of anisotropically diffused particles contained in the core layer.

[0064] Anisotropic diffused particles (preferably needle-shaped particles) may be present in the core layer in an amount of 1 wt% to 30 wt%, for example, 1 wt% to 15 wt%, 1 wt% to 10 wt%, or 1 wt% to 5 wt%. Within this range, the anisotropic diffused particles can provide improvements in contrast and brightness without increasing the haze of the polarizer due to an excess of anisotropic diffused particles.

[0065] In this invention, anisotropic diffused particles (e.g., needle-like particles) are incorporated into the core layer by incorporating multiple microstructures including the anisotropic diffused particles (e.g., needle-like particles) into the matrix, rather than by directly incorporating them into the matrix constituting the core layer. The anisotropic diffused particles are aligned in one direction within the microstructures. Compared to a polarizer that includes anisotropic diffused particles in the matrix, this structure enhances the alignment of the needle-like particles in a specific direction (e.g., the stretching direction in the fabrication of the optical functional layer), thereby providing improved anisotropic diffusion effects while improving contrast ratio.

[0066] According to one embodiment, the core layer includes a matrix and a plurality of microstructures dispersed in the matrix, wherein at least some of the plurality of microstructures include a first resin and needle-like microparticles aligned in one direction within the first resin, and the matrix includes a second resin.

[0067] The matrix is ​​used to support the microstructure during its formation while enhancing the mechanical strength of the optical functional layer. Furthermore, the matrix can be used to improve frontal brightness and anisotropic diffusion.

[0068] The microstructure includes a first resin and needle-like particles aligned in one direction within the first resin. For example, the first resin defines the shape of the microstructure and allows anisotropically diffusing particles to align in one direction during microstructure fabrication. Furthermore, the first resin can be used to improve frontal brightness and anisotropic diffusivity. The microstructure ensures proper alignment of the needle-like particles by allowing them to be initially captured by the first resin.

[0069] The microstructure may have a major axis and a minor axis (the length of the microstructure along the major axis is greater than the length along the minor axis), and may have an elliptical or amorphous shape in the cross-section along the major axis and a circular, elliptical, or amorphous shape in the cross-section along the minor axis. Here, the length of the microstructure along the major axis may be greater than or equal to the maximum length of the needle-like particle, and may be 3 micrometers or more, for example, 3 micrometers to 30 micrometers, or 5 micrometers to 25 micrometers. The length of the microstructure along the minor axis may be greater than or equal to the cross-sectional diameter of the needle-like particle, and may be 2 micrometers or less, for example, 0.1 micrometers to 2 micrometers, or 0.2 micrometers to 1.5 micrometers. Within these ranges, the microstructure can readily receive needle-like particles.

[0070] The microstructure may comprise 60 wt% to 99 wt% (e.g., 70 wt% to 99 wt% or 80 wt% to 99 wt%) of a first resin, and 1 wt% to 40 wt% (e.g., 1 wt% to 30 wt% or 1 wt% to 20 wt%) of surface-modified needle-like microparticles. Within this range, the microstructure can be readily prepared while ensuring that the needle-like microparticles improve the contrast ratio.

[0071] According to one embodiment, one or more types, such as two or more types of needle-like particles, may be present in the microstructure.

[0072] The matrix includes a second resin, and the microstructure includes a first resin.

[0073] For example, the first resin may include polycyclohexane dimethyl terephthalate resin.

[0074] For example, the second resin may include at least one of polyethylene terephthalate (PET) resin or polyethylene naphthalate (PEN) resin.

[0075] According to one embodiment, the first resin may be polycyclohexylenedimethylene terephthalate (PCTG), and the second resin may be polyethylene terephthalate (PET) resin. Since the optical functional layer comprises a microstructure formed of the first resin and a matrix comprising the second resin, the optical functional layer ensures a significant improvement in frontal brightness and anisotropic diffusion rate.

[0076] According to one embodiment, the first resin may have a refractive index of 1.5 to 1.6, and the second resin may have a refractive index of 1.6 to 1.7, which is greater than the refractive index of the first resin. Within these ranges, refractive index matching between the matrix and the microstructure can be promoted, and further improvement in visibility can be achieved.

[0077] According to one embodiment, the polycyclohexanedimethyl terephthalate (PCTG) resin may be present in the first resin in an amount of 95% by weight or more (e.g., 99% by weight to 100% by weight).

[0078] In the core layer, the matrix may be present in an amount of 50 wt% to 95 wt% (e.g., 60 wt% to 90 wt%), and the microstructure may be present in an amount of 5 wt% to 50 wt% (e.g., 10 wt% to 40 wt%). Within these ranges, the optical functional layer ensures improved front-side brightness and anisotropic diffusion.

[0079] In the core layer, the microstructures may be randomly dispersed within the matrix. However, it should be understood that the invention is not limited thereto, and the microstructures may be aligned with the needle-like particles in the same direction within the matrix.

[0080] According to one embodiment, the microstructure may have a cross-section with a major axis and a minor axis in its thickness direction, such as an elliptical cross-section.

[0081] Figure 1 is a conceptual diagram of a polarizing plate according to one embodiment.

[0082] Referring to FIG1, the polarizing plate includes a polarizer 100 and an optical functional layer 200 stacked on one surface of the polarizer 100 in the Z direction. The optical functional layer 200 includes a matrix 210 and a plurality of microstructures 220. The microstructures 220 include a first resin 221 and needle-like particles 222.

[0083] Referring to FIG1, the light absorption axis direction of the polarizer 100 (represented by the X-axis (i.e. direction X) in FIG1) is substantially the same as the alignment direction of the needle-like particles 222 in the microstructure 220 of the optical functional layer 200.

[0084] Here, "substantially the same direction" means that when the light absorption axis of the polarizer is 0°, the anisotropic diffusing particles are aligned with the light absorption axis of the polarizer at an angle of -5° to +5° (e.g., -3° to +3°, or 0°). According to one embodiment, the light absorption axis of the polarizer corresponds to the machine direction (MD) of the polarizer. That is, in Figure 1, the X-axis represents MD and the Y-axis (i.e., direction Y) represents the transverse direction (TD).

[0085] According to one embodiment, the optical functional layer may have a thickness of 0.5 micrometers to 80 micrometers (preferably 0.5 micrometers to 50 micrometers, more preferably 1 micrometer to 20 micrometers).

[0086] First epidermis

[0087] The first skin layer may be included in the optical functional layer to maintain the stability of the membrane operation, protect the core layer from external damage, and maintain the surface gloss to allow for improved optical properties, such as transmittance.

[0088] The first skin layer may include at least one of polyethylene terephthalate (PET) resin or polyethylene naphthalate (PEN) resin.

[0089] The first epidermal layer may have a thickness of 1 micrometer to 50 micrometers (preferably 1 micrometer to 30 micrometers, more preferably 1 micrometer to 20 micrometers).

[0090] Second epidermis

[0091] The second skin layer may be included in the optical functional layer to maintain the stability of the film operation, protect the core layer from external damage, and maintain the surface gloss to allow for improved optical properties, such as transmittance.

[0092] The second skin layer may include at least one of polyethylene terephthalate (PET) resin or polyethylene naphthalate (PEN) resin.

[0093] The second epidermal layer may have the same or different thickness as the first epidermal layer, and may have a thickness of 1 micrometer to 50 micrometers (preferably 1 micrometer to 30 micrometers, more preferably 1 micrometer to 20 micrometers).

[0094] Fabrication of optical functional layers

[0095] The optical functional layer can be formed by introducing a mixture of surface-modified needle-like particles and a first resin into an extruder to produce a high-concentration masterbatch, mixing the high-concentration masterbatch with the first resin to produce a composition for the core layer, co-extruding the composition for the core layer, the composition for the first skin layer and the composition for the second skin layer to produce a sheet, and stretching the sheet at a predetermined stretch ratio.

[0096] According to one embodiment, stretching may include stretching the sheet to 1 to 6 times in the mechanical direction of the sheet and to 1 to 5 times in the transverse direction of the sheet.

[0097] According to one embodiment, the core layer, the first epidermal layer and the second epidermal layer may have the same stretching direction.

[0098] In addition to the optical functional layer, the polarizing plate may further include a polarizer and at least one selected from the protective layer (including the delay layer), the adhesive layer and / or the bonding layer, the functional film (including the functional coating).

[0099] (i) Polarizer

[0100] The polarizer is a linear light absorption type polarizer, and is used to provide polarization function by transmitting a portion of incident light in one direction while absorbing a portion of incident light perpendicular to said one direction.

[0101] 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.

[0102] The polarizer may have a thickness of 50 micrometers or less, for example, from 5 micrometers to 30 micrometers. Within this range, the film will not melt or break when stretched.

[0103] (ii) Protective layer

[0104] The protective layer is used to protect the polarizer or increase the mechanical strength of the polarizing plate. In addition, the protective layer can serve as an adhesive to which an optical functional layer is attached.

[0105] The protective layer may include a transparent substrate. The transparent substrate may have a higher or lower refractive index than the optical functional layer. Preferably, the transparent substrate has a higher refractive index than the optical functional layer. With this structure, the protective layer can help improve contrast and brightness.

[0106] The transparent substrate may include an optically transparent resin film, comprising: a light incident surface; and a light emitting surface opposite to the light incident surface. The transparent substrate may be a single resin film or a stack of multiple resin films. The resin may include, but is not limited to, at least one selected from cellulose resins (including triacetylcellulose (TAC) and the like), cyclic polyolefin resins (including amorphous cyclic olefin polymers (COP) and the like), polycarbonate resins, polyester resins (including polyethylene terephthalate (PET) and the like), polyether resins, polyether resins, polyamide resins, polyimide resins, noncyclic polyolefin resins, polyacrylate resins (including poly(methyl methacrylate) and the like), polyvinyl alcohol resins, polyvinyl chloride resins, and polyvinylidene chloride resins. Preferably, the transparent substrate includes a polyester resin, such as polyethylene terephthalate (PET), to ensure further improvement in contrast and brightness.

[0107] 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 these ranges of haze and light transmittance, the transparent substrate may be used in polarizing plates.

[0108] The transparent substrate may have a thickness of 5 micrometers to 200 micrometers, for example, 30 micrometers to 120 micrometers. Within this range, the transparent substrate can be used in polarizing plates.

[0109] The protective layer may further include a functional layer stacked on at least one surface of the transparent substrate. The functional layer may include a base coat, an anti-glare layer, an anti-reflective layer, a low refractive index layer, a high refractive index layer, a hard coating, a fingerprint-resistant layer, etc.

[0110] The protective layer may be an isotropic film with substantially zero delay, or may have an in-plane delay of a predetermined range to provide additional functionality when combined with a polarizing plate.

[0111] In one embodiment, the protective layer may have an in-plane delay of 3,000 nanometers or greater at a wavelength of 550 nanometers. Within this range, the protective layer may be combined with an optical functional layer to help improve contrast and / or brightness. The protective layer may have an in-plane delay of 4,000 nanometers or greater, specifically 8,000 nanometers or greater, more specifically 10,000 nanometers or greater, even more specifically greater than 10,000 nanometers, even more specifically 10,100 nanometers to 30,000 nanometers or 10,100 nanometers to 15,000 nanometers.

[0112] In another embodiment, the protective layer may have an in-plane delay of less than 3,000 nanometers at a wavelength of 550 nanometers. For example, the protective layer may have an in-plane delay of 0 nanometers to 1,000 nanometers or 10 nanometers to 500 nanometers at a wavelength of 550 nanometers.

[0113] The protective layer may be the first protective layer, the second protective layer or the third protective layer as described below.

[0114] (iii) Adhesive layer and / or bonding layer

[0115] The adhesive layer and / or bonding layer can be used to adhere or bond polarizers, optical functional layers, protective layers, functional films, etc. to each other.

[0116] The adhesive layer may be formed from typical adhesive compositions known to those skilled in the art. For example, the adhesive layer may be a (meth)acrylate adhesive layer, an epoxy adhesive layer, a silicone adhesive layer, a polyurethane adhesive layer, an epoxy (meth)acrylate adhesive layer, or a polyurethane (meth)acrylate adhesive layer. For example, the adhesive layer may be a pressure-sensitive adhesive (PSA) layer.

[0117] The bonding layer may be formed from typical components known to those skilled in the art. For example, the bonding layer may be formed from water-based adhesives, photocurable adhesives, etc.

[0118] (iv) Functional membrane

[0119] The functional film can be selectively used in the polarizer to provide additional functionality to the polarizer.

[0120] The functional film (e.g., functional coating) may be an anti-glare film, an anti-reflection film, an ultra-low reflectivity film, a low refractive index film, a high refractive index film, or an anti-fingerprint film.

[0121] According to one embodiment, the polarizing plate may include: a polarizer; and an optical functional layer stacked on the light emitting surface of the polarizer.

[0122] According to another embodiment, the polarizing plate may include: a polarizer; and an optical functional layer and a first protective layer sequentially stacked on the light emitting surface of the polarizer.

[0123] According to another embodiment, the polarizing plate may include: a polarizer; and an optical functional layer and a functional coating sequentially stacked on the light emitting surface of the polarizer.

[0124] According to yet another embodiment, the polarizing plate may include: a polarizer; and a second protective layer, an optical functional layer and a first protective layer stacked sequentially on the light emitting surface of the polarizer.

[0125] According to yet another embodiment, the polarizing plate may include: a polarizer; a second protective layer, an optical functional layer and a first protective layer stacked sequentially on the light emitting surface of the polarizer; and a third protective layer stacked on the light incident surface of the polarizer.

[0126] As described above, the layers of the polarizing plate can be stacked using adhesive layers, bonding layers, etc., as needed.

[0127] According to another aspect of the present invention, the optical display device includes a polarizing plate according to the present invention.

[0128] In one embodiment, the optical display device may include a polarizing plate according to the present invention as a viewer-side polarizing plate on a liquid crystal panel. Here, "viewer-side polarizing plate" refers to a polarizing plate disposed on the side of the liquid crystal panel facing the screen, that is, a polarizing plate disposed on the side of the liquid crystal panel opposite to the light source.

[0129] In one embodiment, the liquid crystal display may include a light-concentrating backlight unit, a light source-side polarizing plate, a liquid crystal panel, and a viewer-side polarizing plate stacked in sequence, wherein the viewer-side polarizing plate may include a polarizing plate according to the present invention. Here, "light source-side polarizing plate" refers to a polarizing plate disposed on the side of the liquid crystal panel facing the light source. The liquid crystal panel may employ vertical alignment (VA) mode, IPS mode, patterned vertical alignment (PVA) mode, or super-patterned vertical alignment (S-PVA) mode, but is not limited thereto.

[0130] The optical display device may be a foldable or flexible optical display device or a non-foldable or non-flexible optical display device.

[0131] The present invention will now be described in more detail with reference to some examples. However, it should be noted that these examples are provided for illustrative purposes only and should not be construed as limiting the invention in any way.

[0132] Example 1

[0133] (1) 100 parts by weight of a mixture of CaCO3 particles (CaCO3: needle-shaped anisotropic microparticles, length: 10 to 30 micrometers, cross-sectional diameter: 0.5 to 2.0 micrometers, refractive index: 1.68, Whiscal A, Maruo Calcium Co., Ltd.) were added to a solvent solution of methyl ethyl ketone containing vinyltriethoxysilane, reacted at room temperature, and dried in an oven at 90°C to remove the solvent, thereby preparing a mixture of CaCO3 needle-shaped particles that had undergone surface modification with vinyltriethoxysilane.

[0134] (2) A composition is prepared by mixing a mixture of needle-like particles with polycyclohexylenedimethylene terephthalate (PCTG) resin (refractive index: 1.56, TAK Chemical Co., Ltd.) at a predetermined mixing ratio, and then introduced into an extruder to prepare a high-concentration masterbatch. Here, the masterbatch comprises 80% by weight of PCTG and 20% by weight of needle-like particles that have undergone vinyltriethoxysilane surface modification.

[0135] (3) Polyethylene terephthalate (PET) resin was used as the matrix component. The core layer composition was prepared by mixing 80% by weight of PET resin and 20% by weight of the prepared masterbatch. PET resin was used as the skin layer.

[0136] (4)The core layer composition and the skin layer PET resin are introduced into a co-extruder and then co-extruded at a temperature of 250°C to 270°C to prepare a sheet with a predetermined thickness (0.5 mm to 1 mm).

[0137] An optical functional layer is prepared by sequentially stretching a sheet at a stretch ratio of 5 in the mechanical direction and at a stretch ratio of 2 in the transverse direction.

[0138] 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. The core layer includes a matrix formed of PET resin and multiple microstructures including CaCO3 particles impregnated in the matrix. The CaCO3 particles are aligned in one direction in PCTG resin and subjected to a vinyltriethoxysilane surface treatment. The core layer has a thickness of 9 micrometers, and the first and second skin layers each have a thickness of 1 micrometer.

[0139] (5) A polyvinyl alcohol film was stretched at 60°C in its mechanical direction at a stretch ratio of 3, stained with iodine, and further stretched in its MD at 40°C in a boric acid aqueous solution at a stretch ratio of 2.5 to prepare a polarizer (thickness: 13 micrometers, light transmittance: 44%).

[0140] (6) Using an adhesive, the optical functional layer and the cyclic olefin polymer (COP) film are respectively bonded to the upper and lower surfaces of the prepared polarizer, thereby creating a polarizing plate with an optical functional layer / polarizer / cyclic olefin polymer film stacked structure.

[0141] Example 2

[0142] The polarizing plate was fabricated 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 during the fabrication of the optical functional layer. The core layer had a thickness of 1 micrometer, and the first skin layer and the second skin layer each had a thickness of 1 micrometer.

[0143] Example 3

[0144] The polarizing plate was prepared in the same manner as in Example 1, except that epoxycyclohexylethyltrimethoxysilane was used instead of vinyltriethoxysilane for surface modification.

[0145] Example 4

[0146] Except for using epoxycyclohexylethyltrimethoxysilane instead of vinyltriethoxysilane for surface modification, the polarizing plate was prepared in the same manner as in Example 2.

[0147] Comparative Example 1

[0148] The polarizing plate was prepared in the same manner as in Example 1, except that the vinyltriethoxysilane surface modification was not performed.

[0149] Comparative Example 2

[0150] The polarizing plate was prepared in the same manner as in Example 2, except that the vinyltriethoxysilane surface modification was not performed.

[0151] Comparative Example 3

[0152] The polarizing plate was prepared in the same manner as in Example 1, except that the vinyltriethoxysilane surface modification was not performed and the ratio of Equation 1 was changed by changing the thickness of the skin layer and the core layer.

[0153] Comparative Example 4

[0154] Except for changing the ratio of Equation 1 by changing the thickness of the epidermis and the core layer, the polarizing plate was prepared in the same manner as in Example 1.

[0155] Comparative Example 5

[0156] Except for changing the ratio of Equation 1 by changing the thickness of the epidermis and the core layer, the polarizing plate was prepared in the same manner as in Example 1.

[0157] Using each of the polarizing plates manufactured in the examples and comparative examples, a model for measuring the viewing angle was manufactured and evaluated according to the characteristics shown in Table 1.

[0158] A viewer-side polarizer was removed from a liquid crystal panel (model: UN55KS8000F, 55-inch Samsung UHD TV), and then each of the polarizers manufactured in the examples and comparative examples was attached to the liquid crystal panel as a viewer-side polarizer to create a model for measuring viewing angles. The light source-side polarizer of the model for measuring viewing angles includes a COP film, a polarizer, and a PET film stacked sequentially on the liquid crystal panel.

[0159] Evaluate the following characteristics and the results are shown in Table 1.

[0160] (1) Confirmation of the microstructure in the optical functional layer:

[0161] The cross-sections of each of the optical functional layers prepared in the examples and comparative examples were observed by scanning electron microscope (SEM) in the light absorption axis direction and light transmission axis direction of the polarizer, and the results are shown in Figures 3A, 3B, 4A and 4B.

[0162] Figures 3A and 3B are cross-sectional views and magnified cross-sectional views, respectively, of the optical functional layer in the light absorption axis direction of the polarizer of the polarizer according to an embodiment of the present invention. Figures 4A and 4B are cross-sectional views (Figure 4A) and magnified cross-sectional views (Figure 4B), respectively, of the optical functional layer in the light transmission axis direction of the polarizer of the polarizer according to an embodiment of the present invention.

[0163] Referring to Figures 3A and 3B, it can be seen that the needle-like particles and the microstructures including the needle-like particles are aligned in one direction. Referring to Figures 4A and 4B, it can be seen from the cross-section of the needle-like particles that the needle-like particles are aligned in the direction of the light absorption axis of the polarizer.

[0164] (2) Front brightness (unit: none): A liquid crystal display module containing a single-sided LED light source was manufactured by assembling an LED light source, a light guide plate, and a model for measuring the viewing angle (a module with the same configuration as a 55-inch Samsung UHD TV (model: UN55KS8000F) except for the model for measuring the viewing angle manufactured for each of the polarizers in the use examples and comparative examples). The front brightness of the module was measured at the front side (0°, 0°) in a spherical coordinate system using an EZCONTRAST X88RC (EZXL-176R-F422A4, ELDIM SA). The ratio of the front brightness of the module to the front brightness of the polarizer of Reference Example 1 (including the polarizer consisting of a COP film, a polarizer, and a PET film stacked in sequence) measured at the front side (0°, 0°) was calculated.

[0165] (3) Anisotropic diffusion rate: The liquid crystal display module was manufactured in the same manner as in (2). The front and lateral brightness of the module in white mode were measured in a spherical coordinate system at the front (0°, 0°) and lateral (60°, 0°) sides, respectively. The ratio of the lateral brightness (60°, 0°) of the module in white mode to the front brightness (0°, 0°) of the module was calculated.

[0166] (4)Single-sheet reflectance (unit: %): The SCI reflectance (%) was measured on a single sheet of anisotropic film using a colorimeter (model CM3600A, Konica Minolta Co., Ltd.).

[0167] (5)Pore level (unit: none): The pore level of the optical functional layer is evaluated by SEM and scored from level 1 to level 10. From level 1 to level 10, a higher pore level indicates that there are more pores in the optical functional layer.

[0168] Table 1 matrix First Resin Modification Content of needle-like particles Ratio of Equation 1 Front brightness Anisotropic diffusion rate Single-piece reflectivity void level Example 1 PET PCTG Vinyltriethoxysilane 0.82 0.82 0.82 17 7 7 Example 2 PET PCTG Vinyltriethoxysilane 0.33 0.33 0.33 20 13 7 Example 3 PET PCTG Epoxysilane 0.82 0.82 0.82 19 10 3 Example 4 PET PCTG Epoxysilane 0.33 0.33 0.33 twenty three 9 3 Comparative Example 1 PCTG PCTG Unmodified 0.82 0.82 79 17 14 10 Comparative Example 2 PCTG PCTG Unmodified 0.33 0.33 80 20 14 10 Comparative Example 3 PCTG PCTG Unmodified 0.71 0.71 79 17 14 10 Comparative Example 4 PCTG PCTG Vinyltriethoxysilane 0.25 0.25 75 18 12 8 Comparative Example 5 PCTG PCTG Vinyltriethoxysilane 0.85 0.85 0.85 25 17 8 *Particle content: The content (by weight) of needle-like particles (CaCO3) in the core layer.

[0169] As shown in Table 1, the polarizing plate of the examples enhances visibility even without a pattern or a patterned visibility enhancement layer. The polarizing plate of the examples provides improved characteristics in terms of front brightness and anisotropic diffusion rate, has a good contrast ratio on the front and lateral sides, and does not allow voids to be generated by ensuring good compatibility between the first resin and needle-like particles in the microstructure.

[0170] In contrast, the polarizer of the comparative example allows voids to be generated and exhibits poor characteristics in terms of front brightness and anisotropic diffusion rate.

[0171] It should be understood that various modifications, alterations, changes and equivalent embodiments may be made by those skilled in the art without departing from the spirit and scope of the invention. [Simplified Explanation of the Diagram]

[0019] Figure 1 is a conceptual diagram of the optical functional layer. Figure 2 is a conceptual diagram of the needle-like particles. Figures 3A and 3B are respectively a cross-sectional view and a magnified cross-sectional view of the optical functional layer in the polarizer of the polarizing plate according to an embodiment of the present invention, along the light absorption axis. Figures 4A and 4B are respectively a cross-sectional view and a magnified cross-sectional view of the optical functional layer in the polarizer of the polarizing plate according to an embodiment of the present invention, along the light transmission axis.

Claims

1. A polarizing plate, comprising: polarizer; An optical functional layer is formed on one surface of the polarizer, wherein the optical functional layer includes a first skin layer, a core layer, and a second skin layer, and each of the upper and lower surfaces of the optical functional layer is a planar layer. The core layer includes a matrix and a plurality of microstructures dispersed in the matrix, wherein the matrix includes a second resin, the second resin being at least one of polyethylene terephthalate (PET) resin or polyethylene naphthalate (PEN) resin. At least some of the plurality of microstructures include a first resin and needle-like particles aligned in one direction and subjected to surface treatment within the first resin, wherein the first resin is polycyclohexane dimethyl terephthalate resin, and the needle-like particles are surface-modified using at least one of a vinyl silane compound or an epoxy silane compound. When the light absorption axis of the polarizer is 0°, the alignment direction of the needle-like particles is tilted at an angle of -5° to +5° relative to the light absorption axis of the polarizer. The optical functional layer has a ratio of 0.3 to 0.82 according to Equation 1: [Equation 1] Ratio = b / (a + b + c) where a represents the thickness of the first epidermal layer, b represents the thickness of the core layer, and c represents the thickness of the second epidermal layer, wherein each of the thicknesses a, b, and c is in micrometers.

2. The polarizing plate as claimed in claim 1, wherein the optical functional layer is a contrast or brightness enhancement layer.

3. The polarizing plate as claimed in claim 1, wherein the needle-like particles comprise needle-like microparticles.

4. The polarizing plate as claimed in claim 1, wherein the needle-like particles are formed from at least one selected from titanium dioxide, zirconium oxide, zinc oxide, calcium carbonate, boehmite, aluminum borate, calcium silicate, magnesium sulfate, magnesium sulfate hydrate, and potassium titanate.

5. The polarizing plate as claimed in claim 1, wherein the needle-like particles have an average aspect ratio of 5 to 60.

6. The polarizing plate as claimed in claim 1, wherein the needle-like particles are present in the optical functional layer in an amount of 1% to 30% by weight.

7. The polarizing plate as claimed in claim 1, wherein the microstructure is provided with a plurality of said needle-like particles.

8. The polarizing plate as claimed in claim 1, wherein the microstructure has a structure having a long axis direction and a short axis direction.

9. The polarizing plate of claim 1, wherein the microstructure is aligned in the matrix in the same direction as the alignment direction of the needle-like particles.

10. The polarizing plate as claimed in claim 1, wherein the core layer, the first skin layer, and the second skin layer have the same stretching direction.

11. The polarizing plate of claim 1, wherein the matrix is ​​present in the optical functional layer in an amount of 50% to 95% by weight, and the microstructure is present in the optical functional layer in an amount of 5% to 50% by weight.

12. The polarizing plate as described in claim 1, further comprising: It is selected from at least one of the protective layer, adhesive layer, bonding layer, functional film and functional coating.

13. An optical display device comprising a polarizing plate as described in any one of claims 1 to 12.

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