Polarizing plate and optical display device

Abstract

The present application provides a polarizing plate and an optical display device comprising the same, the polarizing plate comprising a polarizing sheet, and an optical functional layer laminated on one face of the polarizing sheet, the optical functional layer comprising a base body, and a plurality of microstructures dispersed in the base body, at least a part of the plurality of microstructures comprising a first resin, and needle-shaped particles oriented in a direction within the first resin, the base body comprising a second resin, the first resin comprising an alloy-based resin, and a difference between glass transition temperatures of the second resin and the alloy-based resin is 10°C or less.

Description

Technical Field

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

[0002] The liquid crystal display device has a structure in which a viewing-side polarizing plate, a liquid crystal panel, and a light source-side polarizing plate are stacked in sequence.

[0003] While liquid crystal displays (LCDs) offer many advantages, they suffer from poor side visibility and low brightness. To address these issues, one method involves adding a visibility-enhancing layer—comprising two resin layers with different refractive indices and a patterned interface between them—to a viewing-side polarizing plate. However, this visibility-enhancing layer suffers from reduced yield due to the patterning process and has limitations in reducing material costs. Therefore, there is a need for a polarizing plate that improves visibility even without this visibility-enhancing layer.

[0004] The background technology of this invention is disclosed in Korean Patent Publication No. 2018-0047569, etc. Summary of the Invention

[0005] The problem that the invention aims to solve

[0006] According to one embodiment, a polarizing plate is provided that has the effect of improving visibility even without a pattern, such as the pattern itself used to improve visibility or a visibility-improving layer with a pattern.

[0007] According to another embodiment, a polarizing plate is provided, which improves both front brightness and anisotropic diffusion.

[0008] According to another embodiment, a polarizing plate is provided that has excellent contrast on both the front and side surfaces.

[0009] Solution for solving the problem

[0010] A polarizing plate according to one embodiment includes: a polarizer and an optical functional layer stacked on one side of the polarizer. The optical functional layer includes a substrate and a plurality of microstructures dispersed in the substrate. At least a portion of the plurality of microstructures includes a first resin and needle-like particles oriented in one direction within the first resin. The substrate includes a second resin. The first resin includes an alloy-based resin. The glass transition temperature difference between the second resin and the alloy-based resin is less than 10°C.

[0011] According to another embodiment, the optical display device includes a polarizing plate according to one embodiment.

[0012] Invention Effects

[0013] According to one embodiment, a polarizing plate is provided that has the effect of improving visibility even without a pattern, such as the pattern itself used to improve visibility or a visibility-improving layer with a pattern.

[0014] According to another embodiment, a polarizing plate is provided, which improves both front brightness and anisotropic diffusion.

[0015] According to another embodiment, a polarizing plate is provided that has excellent contrast on both the front and side surfaces. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a polarizing plate according to one embodiment.

[0017] Figure 2 It is a schematic cross-sectional view of needle-like particles.

[0018] Figure 3 This is a cross-sectional view of the optical functional layer of the polarizer in the absorption axis direction of a polarizer in an embodiment.

[0019] Figure 4 yes Figure 3 Enlarged sectional view.

[0020] Figure 5 This is a cross-sectional view of the optical functional layer in the direction of the light transmission layer of the polarizer in an embodiment of a polarizer.

[0021] Figure 6 yes Figure 5 Enlarged sectional view. Detailed Implementation

[0022] The embodiments are described in detail with reference to the accompanying drawings, enabling those skilled in the art to readily implement them. The invention can be implemented in various different forms and is not limited to the embodiments described herein.

[0023] The terminology used herein is for illustrative purposes only and is not intended to limit the invention. Unless the meaning clearly differs in the context, singular expressions include plural expressions.

[0024] To clearly illustrate the present invention, parts unrelated to the description have been omitted from the accompanying drawings, and the same reference numerals have been assigned to the same or similar components throughout the specification.

[0025] In this specification, "upper part" and "lower part" are defined based on the accompanying drawings. Depending on the viewing position, "upper part" may be changed to "lower part," or "lower part" may be changed to "upper part." The phrase "on" or "on" includes not only the case where it is directly above, but also the case where other structures are provided in the middle. However, "directly on," "directly above," "directly formed," or "directly contacted" refers to the case where no other structures are provided in the middle.

[0026] In this specification, "in-plane phase difference (Re)" is the value at a wavelength of 550 nm, expressed by the following formula A:

[0027] [Formula A]

[0028] Re = (nx - ny) × d

[0029] (In Equation A above, nx and ny are the refractive indices of the protective layer in the slow axis and fast axis directions at a wavelength of 550nm, respectively, and d is the thickness of the protective layer (unit: nm)).

[0030] In this specification, "(meth)acryloyl" refers to acrylamide and / or methacryloyl.

[0031] In this specification, "refractive index" can be a value measured at wavelengths from 380 nm to 780 nm, specifically a value measured at a wavelength of 550 nm.

[0032] In this specification, "transmittance" can be a value measured at wavelengths from 380 nm to 780 nm, specifically, a value measured at a wavelength of 550 nm.

[0033] In this specification, when describing the range of values, "X to Y" means "X ≤ and ≤ Y".

[0034] The polarizing plate of the present invention provides improved visibility even without a visibility-improving layer comprising a patterned resin layer or having a pattern on the interface. The polarizing plate of the present invention provides excellent frontal brightness and anisotropic diffusion.

[0035] "Anisotropic diffusion" refers to the ratio of the brightness measured at the side (60°, 0°) to the brightness measured at the front (0°, 0°) in white mode after the polarizing plate is installed in the optical display device. A higher ratio indicates higher anisotropic diffusion; higher anisotropic diffusion results in better contrast and visibility on the side.

[0036] In this invention, to counteract existing reflective polarization characteristics and maximize asymmetric diffusion, a resin material suitable for the substrate and microstructure is selected, and needle-like particles are oriented within the microstructure. Channels are formed through a sealing function, allowing the needle-like particles to align in one direction during both the unstretched film preparation and stretching processes. This provides a composite optical functional layer that enhances visibility, integrating asymmetric diffusion. This optical functional layer can be combined with a polarizer to ultimately manufacture a polarizing plate that maximizes the side viewing angle of a display product.

[0037] One embodiment of the polarizing plate includes a polarizer and an optical functional layer stacked on one side of the polarizer. The optical functional layer includes a substrate and a plurality of microstructures dispersed in the substrate. At least a portion of the plurality of microstructures includes a first resin and needle-like particles oriented in one direction within the first resin. The substrate includes a second resin. The first resin includes an alloy-based resin. The glass transition temperature difference between the second resin and the alloy-based resin is less than 10°C.

[0038] The first resin mentioned above includes an alloy-based resin, and the glass transition temperature difference between the alloy-based resin and the second resin is less than 10°C. Therefore, the optical functional layer can be manufactured using the first resin and the second resin under the same extrusion conditions.

[0039] That is, the optical functional layer can be manufactured by melt extrusion or solution casting of the composition to produce an unstretched film, followed by stretching. In this case, the glass transition temperature difference is below 10°C, allowing the unstretched film to be manufactured under the same conditions. When the unstretched film is stretched, the viscosity difference between the first and second resins allows for the formation of microstructures, which act as channels, enabling the needle-like particles within the microstructures to align in one direction. If the glass transition temperature difference is greater than 10°C, the needle-like particles may not align well within the microstructures during both the unstretched film manufacturing and stretching processes.

[0040] Among them, "alloy resin" can refer to a resin in which two different resins are combined in a non-chemical way through complementary forces, or one resin is combined with another resin through a chemical reaction.

[0041] According to one embodiment, the glass transition temperature difference between the alloy resin and the second resin can be from 0°C to 10°C, for example, from 0°C to 5°C.

[0042] According to one embodiment, the glass transition temperature of the alloy-based resin may be greater than or equal to the glass transition temperature of the second resin.

[0043] According to one embodiment, the first resin comprises an alloy-based resin. Compared to using a common resin instead of an alloy-based resin as the first resin to manufacture the optical functional layer, the alloy-based resin allows for better refractive index matching between the first and second resins, improves compatibility with the polyethylene naphthalate (PEN) resin used as the second resin, thereby resulting in an excellent appearance of the final optical functional layer and further providing excellent lateral visibility.

[0044] Hereinafter, a polarizing plate according to an embodiment of the present invention will be described.

[0045] A polarizing plate includes a polarizer and an optical functional layer.

[0046] The light transmittance of the polarizing plate can be above 95%, for example, it can be 96% to 100%. Within the above range, it can be used as a viewing-side polarizing plate.

[0047] Optical functional layer

[0048] The optical functional layer is stacked on the light-emitting surface of the polarizer. The aforementioned "light-emitting surface" is the surface that allows the internal light of the backlight unit to reach the polarizer and exit from the polarizer.

[0049] The upper and lower surfaces of the optical functional layer are each planar and unpatterned. Nevertheless, the optical functional layer can improve visibility and / or contrast and / or brightness on the front and sides. This helps improve the manufacturability of the polarizing plate and provides a thinner profile because it does not require optical patterns or patterned layers.

[0050] The optical functional layer includes anisotropic diffused particles.

[0051] Anisotropic diffused particles include needle-like particles. Needle-like particles utilize the different refractive indices and orientations of the particles to achieve varying degrees of light diffusion from the backlight unit, preferably from the polarizer, resulting in significantly improved visibility and contrast.

[0052] A detailed description of needle-like particles is provided.

[0053] Figure 2 It is a schematic cross-sectional view of needle-like particles.

[0054] Needle-shaped particles can be particles with a length L and a certain cross-sectional diameter D, where the cross-sectional diameter D is non-uniform along the entire length L and gradually decreases towards the two ends of the needle-shaped particle. Needle-shaped particles with non-uniform thickness exhibit optical anisotropy, which allows light incident from a polarizer to exit in different directions when passing through the needle-shaped particles.

[0055] Figure 2 This illustrates a case where the cross-sectional diameter of the needle-like particle gradually decreases from the center towards both ends. However, depending on the manufacturing method of the needle-like particle, the cross-sectional diameter can be uniform towards one end, while gradually decreasing only towards the other end.

[0056] The needle-like particles are preferably needle-like microparticles with a longest length L of at least 1 μm. Here, "at least 1 μm" means that the length L is at least 1 μm. This facilitates the orientation of the needle-like microparticles in the microstructure, contributing to improved contrast and brightness. Nanoparticles with a length L of at least 1 nanometer (e.g., nanorollers, needle-like nanoparticles) are inherently difficult to orient in this invention, making it harder to achieve the desired effects. If an excessive amount is included to achieve the same effect, optical properties such as transmittance and haze may be undesirable.

[0057] In one specific embodiment, the length L can be from 10 μm to 50 μm, for example, from 10 μm to 30 μm or from 15 μm to 28 μm. Within the above range, the needle-like particles in this invention are easily oriented, thereby contributing to improved contrast and brightness.

[0058] In one specific embodiment, the cross-sectional diameter D can be from 0.5 μm to 2.0 μm, preferably from 1 μm to 2.0 μm. Within this range, the aspect ratio increases, thereby achieving a lateral diffusion effect. The aforementioned "cross-sectional diameter" refers to the cross-sectional diameter of the needle-like particles, and can refer to the maximum value of the diameter measured on the cross-section of the needle-like particles.

[0059] In one specific embodiment, the cross-section of the needle-like particles can be circular, elliptical, or the like.

[0060] The average aspect ratio of the needle-like particles can be from 5 to 60. Within this range, the contrast and brightness improvement effects of the present invention are readily provided. Preferably, the average aspect ratio can be from 10 to 50, more preferably from 10 to 18. The term "average aspect ratio" refers to the average of the aspect ratios measured individually relative to the needle-like particles, and the term "aspect ratio" refers to the ratio of length to the maximum cross-sectional diameter of the needle-like particles.

[0061] The refractive index of the needle-like particles can be from 1.5 to 2.2, preferably from 1.6 to 1.8, and more preferably from 1.65 to 1.7. Within the above range, a suitable refractive index is achieved relative to the matrix described below, thereby contributing to improved contrast and visibility.

[0062] Needle-shaped particles can be organic particles, inorganic particles, or organic / inorganic particles. For example, needle-shaped particles can be metal oxides such as titanium dioxide (e.g., TiO2), zirconium oxide (e.g., ZrO2), and 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., MgSO4·7H2O), and potassium titanate (e.g., K2Ti8O). 17 Particles formed from one or more of the following: metallic compounds such as calcium carbonate; inorganic particles such as glass; and organic particles such as synthetic resins. Preferably, needle-shaped particles formed from calcium carbonate readily achieve the effects of the present invention and are easy to manufacture.

[0063] Needle-like particles can also be included in the optical functional layer in an unmodified state. However, surface-modified needle-like particles further improve compatibility with the first resin (e.g., an alloy-based resin) in the microstructure and particle dispersibility, thereby improving the optical properties of the optical functional layer and preventing the aggregation of needle-like particles, thus easily achieving the effects of the present invention. More than 50%, for example 60% to 100% or 60% to 95%, of the total surface area of ​​the needle-like particles can be surface-modified. Within the above range, improved compatibility and dispersibility are obtained.

[0064] In one specific embodiment, the surface of the needle-like particles may be modified by one or more of silane compounds, surfactants, and oils. Preferably, the needle-like particles, by surface treatment with a silane compound having (meth)acryloyloxy or (meth)acrylate groups, exhibit excellent compatibility and dispersibility with the alloy-based resins described below.

[0065] Silane compounds having (meth)acryloyloxy or (meth)acrylate groups may include 3-(meth)acryloyloxypropylmethyldimethoxysilane, 3-(meth)acryloyloxypropylmethyldiethoxysilane, 3-(meth)acryloyloxypropyltriethoxysilane, 3-(meth)acryloyloxypropyltrimethoxysilane, preferably one or more of 3-(meth)acryloyloxypropyltrimethoxysilane and 3-(meth)acryloyloxypropyltriethoxysilane.

[0066] According to one embodiment, the needle-like particles can be contained in the optical functional layer in an amount of more than 90%, for example, 95% to 100%, or 100%, of the total anisotropic diffused particles contained therein. Within the above range, the effects of the present invention can be easily achieved. Here, "%" represents the ratio of the weight of the needle-like particles to the weight of the total anisotropic diffused particles contained in the optical functional layer.

[0067] Anisotropic diffused particles, preferably needle-like particles, can be included in the optical functional layer at 1% to 30% by weight, for example, 3% to 15% by weight, 3% to 10% by weight, or 4% to 10% by weight. Within the above range, improved contrast and brightness can be obtained, and the effect of preventing the increase of haze in the polarizer due to excessive inclusion can also be achieved.

[0068] In this invention, anisotropic diffused particles, such as needle-like particles, are included in the optical functional layer. However, instead of including the anisotropic diffused particles within the substrate forming the optical functional layer, multiple microstructures containing the anisotropic diffused particles (e.g., needle-like particles) are incorporated into the substrate. The anisotropic diffused particles in these microstructures are oriented along one direction. Compared to a polarizer containing anisotropic diffused particles within the substrate, this improves the alignment of the needle-like particles in a specific direction (e.g., the stretching direction during the fabrication of the optical functional layer), ultimately improving the anisotropic diffusion effect and further enhancing contrast.

[0069] According to one embodiment, the optical functional layer includes a matrix and a plurality of microstructures dispersed in the matrix. At least a portion of the plurality of microstructures includes a first resin and needle-like particles oriented in one direction within the first resin. The matrix includes a second resin. The first resin includes an alloy-based resin. The glass transition temperature difference between the second resin and the alloy-based resin is less than 10°C.

[0070] The substrate enhances the mechanical strength of the optical functional layers and supports the microstructures during their formation. Furthermore, the substrate also improves frontal brightness and anisotropic diffusion.

[0071] The microstructure includes a first resin and a plurality of needle-like particles oriented in one direction within the first resin. For example, the first resin forms the morphology of the microstructure, and during the fabrication of the microstructure, the anisotropically diffusing particles are oriented in one direction. Furthermore, the first resin can also enhance frontal brightness and anisotropic diffusivity. The microstructure first oriented the needle-like particles within the first resin by a trapping mechanism, thereby ensuring good orientation of the needle-like particles.

[0072] The microstructure has a major axis and a minor axis (in this case, the length of the major axis is longer than the length of the minor axis). It can be a structure with an elliptical or amorphous cross-section along the major axis and a circular, elliptical, or amorphous cross-section along the minor axis. In this case, the length of the major axis of the microstructure can be greater than or equal to the longest length of the needle-like particle, and the length of the major axis of the microstructure can be greater than 3 μm, for example, 3 μm to 30 μm or 5 μm to 25 μm. The length of the minor axis of the microstructure can be greater than or equal to the cross-sectional diameter of the needle-like particle, and the length of the minor axis of the microstructure can be less than 2 μm, for example, 0.1 μm to 2 μm or 0.2 μm to 1.5 μm. Within the above range, needle-like particles can be easily accommodated.

[0073] The microstructure may contain 60% to 99% by weight, for example 70% to 99% by weight, or 90% to 99% by weight, of a first resin, such as an alloy-based resin, and may contain 1% to 40% by weight, for example 1% to 30% by weight, or 1% to 10% by weight, of needle-like particles. Within the above range, it also has the effect of easily manufacturing microstructures and improving contrast through needle-like particles.

[0074] In one specific embodiment, the needle-like particles may include one or more microstructures, such as two or more.

[0075] The matrix includes a second resin, and the microstructure includes a first resin.

[0076] The first resin mentioned above includes an alloy-based resin, and the glass transition temperature difference between the second resin and the alloy-based resin is less than 10°C.

[0077] According to one embodiment, the glass transition temperature of the alloy-based resin can be 100°C to 120°C, for example, 110°C to 115°C, and the glass transition temperature of the second resin can be 100°C to 130°C, for example, 115°C to 120°C. Within the above range, a glass transition temperature difference of less than 10°C can be easily achieved, thereby facilitating the fabrication of optical functional layers.

[0078] According to one embodiment, the alloy resin and the second resin are different from each other.

[0079] For example, alloy-based resins may include one or more of polycarbonate resins and polycyclohexanedimethyl terephthalate resins.

[0080] For example, the second resin may include one or more of polyethylene naphthalate (PEN) resin and polyethylene terephthalate (PET) resin.

[0081] According to one embodiment, the alloying resin can be a polycarbonate alloy (an alloy of polycyclohexanedimethyl terephthalate (PCTG) and polycarbonate (PC)) resin, and the second resin can be polyethylene naphthalate (PEN) resin. When the optical functional layer includes a microstructure made of the first resin and a matrix containing the second resin, the front brightness and anisotropic diffusion can be significantly improved.

[0082] According to one embodiment, the first resin, such as an alloy-based resin, has a refractive index of about 1.5 to 1.6, and the second resin, such as polyethylene naphthalate resin, has a higher refractive index than the first resin (e.g., an alloy-based resin), which may be about 1.6 to 1.7. Within the above range, it is easy to match the refractive index between the matrix and the microstructure, and it can also improve visibility.

[0083] According to one embodiment, the refractive index of polyethylene naphthalate (PEN) resin can be about 1.65, and the refractive index of polycarbonate alloy resin can be about 1.58.

[0084] According to one embodiment, the polycarbonate alloy may be composed of a mixture of polycyclohexylene dimethylene terephthalate (PCTG) and polycarbonate. The combination of polyethylene naphthalate and the polycarbonate alloy is designed to have a high molecular melt flowability difference, i.e., a viscosity difference (intrinsic viscosity of 0.01 or higher), so that microstructures are arranged within the matrix component; preferably, the flowability of the matrix component is superior to that of the microstructure component. According to one embodiment, the polycarbonate alloy may contain 50% to 90% by weight, for example, 55% to 70% by weight of a polycarbonate resin, and 10% to 50% by weight, for example, 30% to 45% by weight of PCTG.

[0085] According to one embodiment, the alloy-based resin can be included in the first resin at a rate of 95% by weight or more, for example, 99% by weight to 100% by weight.

[0086] The optical functional layer may comprise 50% to 95% (e.g., 60% to 90% by weight) of a matrix and 5% to 50% (e.g., 10% to 40% by weight) of microstructures. Within these ranges, frontal brightness and anisotropic diffusion can be improved.

[0087] The microstructures in the optical functional layer can be arbitrarily dispersed within the matrix. However, the orientation of the microstructures within the matrix can be the same as the orientation of the needle-like particles.

[0088] According to one embodiment, the microstructure is a cross-section in the thickness direction having a major axis and a minor axis, for example, it can be elliptical.

[0089] Figure 1 This is a schematic diagram of a polarizing plate according to one embodiment.

[0090] Reference Figure 1 The polarizing plate includes a polarizer 100 and an optical functional layer 200 stacked on one side of the polarizer 100. The optical functional layer 200 includes a substrate 210 and microstructures 220. The microstructures 220 include a first resin 221 and needle-like particles 222.

[0091] Reference Figure 1 The light absorption axis direction of polarizer 100 ( Figure 1 In the image (represented by the X-axis), the orientation can be substantially the same as the orientation of the needle-like particles 222 within the microstructure 220 in the optical functional layer 200.

[0092] Here, "fundamentally the same direction" means that, assuming the light absorption axis of the polarizer is 0°, the orientation direction of the anisotropic diffusing particles is -5° to +5°, for example -3° to +3° or 0°. In a specific embodiment, the light absorption axis of the polarizer is the machine direction (MD) of the polarizer. That is, Figure 1 In the diagram, the X-axis is represented by MD, and the Y-axis by TD.

[0093] In one specific embodiment, the thickness of the optical functional layer can be from 5 μm to 50 μm, preferably from 5 μm to 20 μm, and more preferably from 5 μm to 15 μm.

[0094] In addition to the optical functional layer, the polarizing plate may also include one or more of the following: polarizer, protective layer (including phase difference layer), adhesive layer and / or bonding layer, functional film (including functional coating).

[0095] (i) Polarizer

[0096] A polarizer is a linear absorptive polarizer that allows light to pass through only one direction of the incident light and absorbs light in a direction perpendicular to that direction, thereby providing polarization functionality.

[0097] Polarizing films can be manufactured by dyeing, adsorbing, and stretching polyvinyl alcohol (PVA) films, or by dehydrating polyvinyl alcohol films to produce polyolefin polarizing films.

[0098] The thickness of the polarizer can be less than 50 μm, for example, from 5 μm to 30 μm. Within this range, the film will not melt or break when stretched.

[0099] (ii) Protective layer

[0100] The protective layer is contained within the polarizing plate and can protect the polarizer or improve the mechanical strength of the polarizing plate. The protective layer can be an adhesive that forms the optical functional layer.

[0101] The protective layer may include a transparent substrate. The refractive index of the transparent substrate may be higher or lower than that of the optical functional layer. Preferably, the refractive index of the transparent substrate may be higher than that of the optical functional layer. This can help improve contrast and brightness.

[0102] The transparent substrate may include an optically transparent resin film having a light incident surface and a light emitting surface opposite to the light incident surface. The transparent substrate may be composed of a single layer of resin film, or multiple resin films may be stacked. The resin may include cellulose ester resins such as triacetyl cellulose (TAC); cyclic polyolefin resins including amorphous cyclic polyolefins (COP); polycarbonate resins; polyester resins including polyethylene terephthalate (PET); polyethersulfone resins; polysulfone resins; polyamide resins; polyimide resins; non-cyclic polyolefin resins; polyacrylate resins including polymethyl methacrylate resins; polyvinyl alcohol resins; polyvinyl chloride resins; and polyvinylidene chloride resins, but is not limited thereto. Preferably, the transparent substrate includes a polyester resin such as polyethylene terephthalate (PET), thereby further improving contrast and brightness.

[0103] The haze of the transparent substrate is below 30%, specifically 2% to 30%, and the light transmittance is above 90%, specifically 95% to 100%. Within the above range, it can be used for polarizing plates.

[0104] The thickness of the transparent substrate can range from 5 μm to 200 μm, for example, from 30 μm to 120 μm. Within this range, it can be used for polarizing plates.

[0105] Functional layers may also be stacked on at least one side of the transparent substrate. These functional layers may include a primer layer, an anti-glare layer, an anti-reflective layer, a low-refractive-index layer, a high-refractive-index layer, a hard coating layer, a fingerprint-resistant layer, etc.

[0106] The protective layer is an isotropic film, which can have virtually no phase difference, but has a certain range of in-plane phase difference. Therefore, when combined with a polarizing plate, it can provide additional functions.

[0107] In one specific embodiment, the in-plane phase difference of the protective layer at a wavelength of 550 nm can be greater than 3000 nm. Within this range, when combined with an optical functional layer, it helps to improve contrast and / or brightness. Preferably, the in-plane phase difference can be greater than 4000 nm, greater than 8000 nm, specifically greater than 10000 nm, more specifically greater than 10000 nm, and even more specifically from 10100 nm to 30000 nm, or from 10100 nm to 15000 nm.

[0108] In another specific embodiment, the in-plane phase difference of the protective layer at a wavelength of 550 nm can be less than 3000 nm. For example, the in-plane phase difference of the protective layer at a wavelength of 550 nm can be 0 nm to 1000 nm or 10 nm to 500 nm.

[0109] The protective layer may be a first protective layer, a second protective layer, or a third protective layer, as described below.

[0110] (iii) Adhesive layer and / or bonding layer

[0111] The adhesive layer and / or bonding layer can bond or adhere polarizers, optical functional layers, protective layers, functional films, etc.

[0112] The adhesive layer can be formed from conventional compositions known to those skilled in the art. For example, the adhesive layer can be a (meth)acrylic, epoxy, silicone, urethane, epoxy (meth)acrylic, or polyurethane (meth)acrylic adhesive layer. As an example, the adhesive layer can be a pressure-sensitive adhesive (PSA) layer.

[0113] The adhesive layer can be made of conventional compositions known to those skilled in the art. For example, the adhesive layer can be made of water-based adhesives, UV-curable adhesives, etc.

[0114] (iv) Functional membranes

[0115] Functional films do not necessarily have to be included in polarizing plates, but when included in polarizing plates, they can be films that provide additional functions.

[0116] Functional films and coatings can be anti-glare films, anti-reflective films, ultra-low reflection films, low refractive index films, high refractive index films, or fingerprint-resistant films.

[0117] 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.

[0118] According to another embodiment, the polarizing plate may include a polarizer, an optical functional layer and a first protective layer sequentially stacked on the light emitting surface of the polarizer.

[0119] 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.

[0120] According to another embodiment, the polarizing plate may include a polarizer, and a second protective layer, an optical functional layer, and a first protective layer sequentially stacked on the light emitting surface of the polarizer.

[0121] 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 stacked on the light emitting surface of the polarizer; and a third protective layer stacked on the light incident surface of the polarizer.

[0122] The layers in the aforementioned polarizing plate can be stacked using adhesive layers, bonding layers, etc., as needed.

[0123] The optical display device of the present invention includes the polarizing plate of the present invention.

[0124] In one specific embodiment, the optical display device of the present invention may include the polarizing plate of the present invention as a viewing-side polarizing plate relative to the liquid crystal panel. The aforementioned "viewing-side polarizing plate" refers to a polarizing plate arranged facing the screen side, i.e., the light source side, relative to the liquid crystal panel.

[0125] In one specific embodiment, the liquid crystal display device comprises, in sequence, a light-concentrating backlight unit, a light source-side polarizing plate, a liquid crystal panel, and a viewing-side polarizing plate. The viewing-side polarizing plate may include the polarizing plate of the present invention. The aforementioned "light source-side polarizing plate" is a polarizing plate disposed on the light source side. 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 to these.

[0126] Optical display devices can be foldable or flexible optical display devices, or non-foldable or non-flexible optical display devices.

[0127] Preferred Implementation

[0128] The structure and function of the present invention will be described in more detail below through preferred embodiments. However, the following embodiments are only for the purpose of helping to understand the present invention, and the scope of the present invention is not limited to the following embodiments.

[0129] Example 1

[0130] (1) A mixture of CaCO3 particles was prepared (CaCO3: needle-shaped anisotropic microparticles, length: 10 μm to 30 μm, cross-sectional diameter: 0.5 μm to 2.0 μm, Whiscal A, Maruo CALCIUM, refractive index nx: 1.53, refractive index ny: 1.68, refractive index nx: 1.68).

[0131] A composition was prepared by mixing the aforementioned needle-like particles in a certain proportion in polycyclohexanedimethyl terephthalate (PCTG, refractive index: 1.56, TAK Corporation) resin. The composition was then fed into an extrusion section to prepare a high-concentration masterbatch. At this time, the masterbatch contained 80% by weight of PCTG and 20% by weight of needle-like particles.

[0132] Subsequently, polycarbonate resin (PC, refractive index: 1.58) was mixed into the aforementioned masterbatch and then fed into the extrusion section and heated at 250°C, thereby preparing the composition for manufacturing microstructures. At this time, the composition for manufacturing microstructures contained needle-like particles and a PC alloy resin (glass transition temperature: 118°C) consisting of 60 wt% PC and 40 wt% PCTG.

[0133] A sheet of a certain thickness was produced by mixing 60 parts by weight of polyethylene naphthalate (PEN, refractive index: 1.65, glass transition temperature: 118°C) and 40 parts by weight of the above-mentioned components for manufacturing microstructures and feeding them into the extrusion section. The sheet was then extruded at an extrusion temperature of 230°C to 250°C.

[0134] The optical functional layer was manufactured by stretching the sheet in the mechanical direction at a stretch ratio of 5 and in the width direction at a stretch ratio of 2.

[0135] In the optical functional layer, the matrix and microstructure are contained in a total of 100 parts by weight in a ratio of 60 parts by weight to 40 parts by weight, and the optical functional layer contains 3% by weight needle-like particles.

[0136] (2) For polyvinyl alcohol film, the film was stretched 3 times along the mechanical direction at 60°C and then iodine was adsorbed. The film was then stretched 2.5 times along the mechanical direction in a boric acid aqueous solution at 40°C to produce a polarizer (thickness: 13 μm, transmittance: 44%).

[0137] (3) By using an adhesive, the above-mentioned optical functional layer is bonded to the upper surface of the manufactured polarizer and a cyclic olefin polymer (COP) film is bonded to the lower surface, thereby manufacturing a polarizer consisting of an optical functional layer, a polarizer, and a cyclic olefin polymer film stacked in sequence.

[0138] Examples 2 to 9

[0139] The contents of polyethylene naphthalate and microstructures in Example 1 were changed as shown in Table 1 below, and the contents of needle-like particles in the optical functional layer were changed as shown in Table 1 below. Otherwise, a polarizing plate was manufactured using the same method as in Example 1.

[0140] Comparative Example 1

[0141] The mixture of needle-like particles described in Example 1 was not used; instead, the polarizing plate was manufactured using the same method as in Example 1. The microstructures in the optical functional layer consisted only of an alloy resin composed of PC and PCTG.

[0142] Comparative Example 2

[0143] A polycarbonate (PC) resin (refractive index: 1.58) was mixed with polycyclohexanedimethyl terephthalate (PCTG, refractive index: 1.56, TAK Corporation) and fed into an extrusion section. Sheets of a certain thickness were manufactured by extrusion at extrusion temperatures ranging from 230°C to 250°C. The aforementioned sheets comprise an alloy resin of PC and PCTG.

[0144] For the above-mentioned sheet, an optical functional layer was manufactured by stretching it at a stretch ratio of 5 along the mechanical direction and at a stretch ratio of 2 along the width direction, and a polarizing plate was manufactured by the same method as in Example 1.

[0145] Comparative Example 3

[0146] A mixture of CaCO3 particles was prepared (CaCO3: needle-shaped anisotropic microparticles, length: 10 μm to 30 μm, cross-sectional diameter: 0.5 μm to 2.0 μm, Whiscal A, Maruo Calcium Co., Ltd., refractive index nx: 1.53, refractive index ny: 1.68, refractive index nx: 1.58).

[0147] A composition was prepared by mixing the above-mentioned needle-like particles in a certain proportion in polycyclohexanedimethyl terephthalate (PCTG, refractive index: 1.56, TAK Corporation) resin, and the composition was fed into the extrusion section to prepare a high-concentration masterbatch.

[0148] Subsequently, a polycarbonate-based resin (refractive index: 1.58) was mixed into the aforementioned masterbatch, and then fed into the extrusion section. Extrusion was performed at an extrusion temperature of 230°C to 250°C to produce a sheet of a certain thickness. The sheet was then stretched along its mechanical direction at a stretch ratio of 5 to produce an optical functional layer. A polarizing plate was then manufactured using the same method as in Example 1. The matrix of the aforementioned optical functional layer comprises an alloy resin of PC and PCTG.

[0149] Comparative Example 4

[0150] Polyethylene naphthalate (refractive index: 1.65) was fed into the extrusion section and extruded at an extrusion temperature of 230°C to 250°C to produce a sheet of a certain thickness. An optical functional layer was manufactured by stretching the sheet at a stretch ratio of 5 along its mechanical direction and at a stretch ratio of 2 along its width direction. A polarizing plate was manufactured using the same method as in Example 1.

[0151] Comparative Example 5

[0152] A mixture of CaCO3 particles was prepared (CaCO3: needle-shaped anisotropic microparticles, length: 10 μm to 30 μm, cross-sectional diameter: 0.5 μm to 2.0 μm, Whiscal A, Maruo Calcium Co., Ltd., refractive index nx: 1.53, refractive index ny: 1.68, refractive index nx: 1.58).

[0153] A composition was prepared by mixing the aforementioned needle-like particles in a certain proportion in polyethylene naphthalate (refractive index: 1.65). This composition was then fed into an extrusion section to prepare a high-concentration masterbatch. After being fed into the extrusion section, the masterbatch was extruded at an extrusion temperature of 230°C to 250°C to produce a sheet of a certain thickness. The sheet was then stretched along its mechanical direction at a stretch ratio of 5 to produce an optical functional layer. A polarizing plate was manufactured using the same method as in Example 1.

[0154] Comparative Example 6

[0155] A high-concentration masterbatch was prepared by feeding polyethylene naphthalate (refractive index: 1.65) into the extrusion section.

[0156] Subsequently, polycarbonate resin (PC, refractive index: 1.58) and polycyclohexanedimethyl terephthalate (PCTG, refractive index: 1.56, TAK Corporation) were mixed in the aforementioned masterbatch and then fed into the extrusion section. Extrusion was performed at an extrusion temperature of 230°C to 250°C to produce a sheet of a certain thickness. The sheet was then stretched along its mechanical direction at a stretch ratio of 5 to produce an optical functional layer. A polarizing plate was manufactured using the same method as in Example 1. The matrix in the optical functional layer comprised an alloy resin of PC and PCTG.

[0157] Comparative Examples 7 to 9

[0158] The content of needle-like particles in Comparative Example 6 was changed as shown in Table 1 below. Otherwise, a polarizing plate was manufactured using the same method as in Example 1.

[0159] Reference example 1

[0160] The optical functional layer of Example 1 is not included, but the polarizing plate is manufactured using the same method as in Example 1.

[0161] For the polarizing plates manufactured in the embodiments and comparative examples, the following models for measuring viewing angles were manufactured, and the physical properties in Table 1 below were evaluated.

[0162] In the LCD panel model UN55KS8000F (55-inch, Samsung Electronics TV), the viewing-side polarizer was removed, and the polarizer manufactured in the embodiments and comparative examples was laminated to form the viewing-side polarizer, thereby creating a model for viewing angle measurement. In the model for viewing angle measurement, the light source-side polarizer is stacked in the order of COP film - polarizer - PET film, starting from the LCD panel.

[0163] Evaluate the following physical properties and show the results in Table 1 below.

[0164] (1) Identify the microstructures in the optical functional layer:

[0165] For the optical functional layers manufactured in the embodiments and comparative examples, the cross-sections of the polarizer along the light absorption axis and light transmission axis were measured using SEM, and... Figures 3 to 6 The results are shown in the figure.

[0166] Figure 3 This is a cross-sectional view of the optical functional layer of the polarizer in a polarizing plate according to one embodiment, along the light absorption axis. Figure 4 yes Figure 3 Enlarged sectional view. Figure 5 This is a cross-sectional view of the optical functional layer in the light transmission layer direction of the polarizer in an embodiment of a polarizing plate. Figure 6 yes Figure 5 An enlarged sectional view. For example... Figure 3 and Figure 4 As shown, it can be confirmed that the needle-like particles and the microstructures including the needle-like particles are oriented along one direction. Figure 5 and Figure 6 As shown, the orientation of the needle-like particles along the light absorption axis of the polarizer can be confirmed by examining the cross-section of the needle-like particles.

[0167] (2) Front brightness: An LED light source, a light guide plate, and the above-mentioned viewing angle measurement model were assembled to manufacture a liquid crystal display device containing a single-edge type LED light source (the structure is the same as that of a Samsung TV (55-inch, model: UN55KS8000F), except for the structure of the liquid crystal display device module in the embodiment and comparative example). The brightness at the front (0°, 0°) was measured in a spherical coordinate system using an EZCONTRASTX88RC (EZXL-176R-F422A4, ELDIM). The relative ratio of the brightness at the front (0°, 0°) measured by the polarizer of Reference Example 1 was calculated.

[0168] (3) Anisotropic diffusion: A module for a liquid crystal display device was manufactured using the same method as in (2). Using an EZCONTRAST X88RC (EZXL-176R-F422A4, ELDIM Corporation), the brightness at the front (0°, 0°) and side (60°, 0°) locations was measured in white mode in spherical coordinates. The ratio of the brightness measured at the side (60°, 0°) to the brightness measured at the front (0°, 0°) in white mode was calculated.

[0169] Table 1

[0170]

[0171]

[0172] *Particle content: The content (by weight) of needle-like particles (CaCO3) in the optical functional layer.

[0173] As shown in Table 1 above, the polarizer according to one embodiment can achieve a front brightness of 75 or higher and an anisotropic diffusion of 20 or higher. Therefore, although not shown in Table 1 above, it is predicted that it can provide improved visibility and improve contrast on both the front and side surfaces.

[0174] However, the polarizer of the comparative example, which does not have the optical functional layer of the embodiment, has lower front brightness and anisotropic diffusion than the embodiment.

[0175] Simple variations or modifications of the present invention can be readily implemented by those skilled in the art, and these variations or modifications are considered to be included within the scope of the present invention.

Claims

1. A polarizing plate, comprising: A polarizer and an optical functional layer stacked on one side of the polarizer. The optical functional layer includes a substrate and multiple microstructures dispersed in the substrate. At least a portion of the plurality of microstructures includes a first resin and needle-like particles oriented in one direction within the first resin. The matrix includes a second resin. The first resin includes an alloy-based resin. The glass transition temperature difference between the second resin and the alloy-based resin is less than 10°C.

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

3. The polarizing plate according to claim 1, wherein, The upper and lower surfaces of the optical functional layer are each planar in general.

4. The polarizing plate according to claim 1, wherein, The needle-like particles are needle-like microparticles.

5. The polarizing plate according to claim 1, wherein, The needle-like particles are formed from one or more of the following: titanium oxide, zirconium oxide, zinc oxide, calcium carbonate, boehmite, aluminum borate, calcium silicate, magnesium sulfate, magnesium sulfate hydrate, and potassium titanate.

6. The polarizing plate according to claim 1, wherein, The average aspect ratio of the needle-like particles is 5 to 60.

7. The polarizing plate according to claim 1, wherein, The needle-like particles are included in the optical functional layer at a weight percentage of 1% to 30% by weight.

8. The polarizing plate according to claim 1, wherein, The microstructure contains a plurality of the needle-like particles.

9. The polarizing plate according to claim 1, wherein, The microstructure is a structure with a major axis and a minor axis.

10. The polarizing plate according to claim 1, wherein, The microstructures are arranged in the matrix in the same orientation as the needle-like particles.

11. The polarizing plate according to claim 1, wherein, When the light absorption axis of the polarizer is set to 0°, the orientation of the needle-like particles is -5° to +5°.

12. The polarizing plate according to claim 1, wherein, The glass transition temperature of the alloy-based resin is 100°C to 120°C, and the glass transition temperature of the second resin is 100°C to 130°C.

13. The polarizing plate according to claim 1, wherein, The alloy resin includes one or more of polycarbonate resins and polycyclohexanedimethyl terephthalate.

14. The polarizing plate according to claim 13, wherein, The alloy resin comprises 50% to 90% by weight of polycarbonate resin and 10% to 50% by weight of polycyclohexanedimethyl terephthalate.

15. The polarizing plate according to claim 1, wherein, The second resin includes one or more of polyethylene naphthalate resins and polyethylene terephthalate resins.

16. The polarizing plate according to claim 1, wherein, The optical functional layer comprises 50% to 95% by weight of the substrate and 5% to 50% by weight of the microstructure.

17. The polarizing plate according to claim 1, wherein, The polarizing plate includes one or more of the following: a protective layer, an adhesive layer, a functional film, and a functional coating.

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

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