TW201823033A - Polarizing plate and display device containing the same - Google Patents

Abstract

Embodiments of the invention relate to a polarizing plate. The polarizing plate includes a first polyvinyl alcohol (PVA) layer, a protective layer on a first side of the first polyvinyl alcohol layer, and a second polyvinyl alcohol layer on a second side of the first polyvinyl alcohol layer. The thickness of the second polyvinyl alcohol layer is larger than the thickness of the first polyvinyl alcohol layer.

Description

   Polarizing plate and display device containing the same   

The embodiment of the present invention relates to a polarizing plate, and in particular to a polarizing plate having a retardation film.

Display devices have been widely used in various electronic products. Generally speaking, display devices (such as liquid crystal display devices) generally include an upper polarizing plate, a lower polarizing plate, a display medium layer sandwiched between the upper and lower polarizing plates, and The lower polarizing plate is away from the backlight on one side of the display medium layer. When the backlight provides light, the incident light sequentially passes through the lower polarizing plate, the display medium layer, and the lower polarizing plate. At this time, the incident light will be polarized by the upper and lower polarizing plates, and the polarization state of the display medium layer will be different to match. The display device can display the visual feeling in a bright state and a dark state.

The polarizing plate only allows light in a certain direction to pass through itself. Its composition usually includes a polarizing substrate, an inner protective layer disposed closer to the display medium layer, a protective layer disposed farther from the display medium layer, and an adhesive layer.

In the prior art, the protective layer of the above-mentioned polarizing plate may be formed of Triacetate Cellulose (TAC). However, the thickness of the protective layer formed by the above-mentioned triacetate cellulose (TAC) material is relatively large (usually 60 μm (micrometers)), which is not conducive to the demand for thinning.

An embodiment of the present invention provides a polarizing plate, including: a first polyvinyl alcohol (PVA) layer; a protective layer on the first side of the first polyvinyl alcohol layer; and a second polyvinyl alcohol layer on the first A second layer of polyvinyl alcohol is on the second side. The thickness of the second polyvinyl alcohol layer is greater than the thickness of the first polyvinyl alcohol layer.

An embodiment of the present invention also provides a display device, including: a display medium layer; a first substrate and a second substrate sandwiching the display medium layer; and the polarizing plate provided in the foregoing embodiment of the present invention, disposed on the first substrate or On the second substrate.

10‧‧‧ polarizing plate

20‧‧‧ display device

100‧‧‧ Adhesive layer

102‧‧‧Second polyvinyl alcohol layer

104‧‧‧first polyvinyl alcohol layer

104a‧‧‧First side of the first polyvinyl alcohol layer

104b‧‧‧ Second side of the first polyvinyl alcohol layer

106‧‧‧ protective layer

200‧‧‧Display media layer

202‧‧‧First substrate

204‧‧‧Second substrate

206‧‧‧first polarizer

208‧‧‧Second polarizing plate

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that, in accordance with standard practice in the industry, various features are not drawn to scale and are for illustration purposes only. In fact, it is possible to arbitrarily enlarge or reduce the size of the element to clearly show the characteristics of the embodiment of the present invention.

FIG. 1 is a cross-sectional view of a polarizing plate according to some embodiments of the present invention.

FIG. 2 is a cross-sectional view of a display device according to some embodiments of the present invention.

A number of different implementation methods or examples are disclosed below to implement different features of the embodiments of the present invention. Specific embodiments and arrangements thereof are described below to illustrate the present invention. Of course, these embodiments are only for illustration, and the scope of the present invention should not be limited by this. For example, in the description, it is mentioned that the first element is formed on the second element, which includes an embodiment in which the first element and the second element are in direct contact, and also includes the other between the first element and the second element. An embodiment of the element, that is, the first element is not in direct contact with the second element. In addition, repeated reference numerals or signs may be used in different embodiments. These repetitions are only for simply and clearly describing the embodiments of the present invention, and do not represent a specific relationship between the different embodiments and / or structures discussed.

In addition, space-related terms such as "below", "below", "lower", "above", "higher" and similar terms may be used. These space-related terms Words are used to facilitate the description of the relationship between one or more elements or features and other elements or features in the illustration. These spatially related terms include different positions of the device in use or operation, and The described orientation. The device may be turned to different orientations (rotated 90 degrees or other orientations), and the spatially related adjectives used therein can be interpreted the same way.

In addition, the definitions of the terms of optical properties in the embodiments of the present invention are as follows:

(1) n _x is the refractive index in the direction of the largest refractive index in the plane of the film (that is, the direction of the late phase axis), and n _y is the direction in the plane of the film that is perpendicular to the direction of the late phase axis (that is, the phase advance Axis direction), n _z is the refractive index in the thickness direction of the film layer, and d is the thickness of the film layer.

(2) The phase difference value in the film plane is defined as Δ n × d, where Δ n is the birefringence difference, and Δ n = (n _x -n _y ). In general, the phase difference value within a film is measured using light having a wavelength of 590 nm (nanometers).

(3) The phase difference in the thickness direction is defined as {[(n _x + n _y ) / 2] -n _z } × d. Generally, the phase difference value in the thickness direction is measured using light having a wavelength of 590 nm.

The polarizing plate of the embodiment of the present invention uses a retardation film to replace the protective layer of a traditional polarizing plate (especially an inner protective layer provided closer to the polarizing substrate), and the same retardation film is formed using the same material as the polarizing substrate, so Simplify the material composition of the polarizing plate, thereby reducing the production cost of the polarizing plate.

Please refer to FIG. 1, which illustrates a polarizing plate 10 according to some embodiments of the present invention. The polarizing plate 10 includes a first polyvinyl alcohol (PVA) layer 104 and a first side 104 a of the first polyvinyl alcohol layer 104. The protective layer 106, the second polyvinyl alcohol layer 102 located on the second side 104b opposite to the first polyvinyl alcohol layer 104, and the adhesive layer 100.

In some embodiments, the first polyvinyl alcohol layer 104 is used as a polarizing substrate, and may include a hydrophilic polymer film, such as a polyvinyl alcohol-based film, a part of a dimethoxymethane-based polyvinyl alcohol-based film, and ethylene-acetic acid. The vinyl ester copolymer is a partially saponified film, a combination thereof, or other appropriate materials.

The production of the first polyvinyl alcohol layer 104 as a polarizing substrate may generally include processes such as water washing, swelling, dyeing, stretching, and drying. For example, a transparent and colorless polyvinyl alcohol film can be dyed in a certain proportion of iodine solution to make iodine ions adhere to the polyvinyl alcohol film, and then according to a first extension multiple (for example: 1 to 7 times, (It is preferably 5 to 7 times.) The extension process is performed along the first main extension direction, so that the length of the polyvinyl alcohol film becomes 1 to 7 times, preferably 5 to 7 times, the original length, so as to form the first polyethylene layer 104. And its absorption axis. The above-mentioned extension process may be uniaxial extension or biaxial extension. In the biaxial extension process, the first main extension direction of the first polyvinyl alcohol layer 104 is defined as a direction with a larger extension multiple. For example, the above-mentioned stretching process may be wet stretching (for example: stretching process in aqueous iodine solution, boric acid, zinc sulfate, zinc chloride, potassium iodide, etc.) or dry stretching (for example: stretching with a tenter) . Optionally, a water washing process may be performed on the polyvinyl alcohol film before dyeing to wash dirt on the surface of the polyvinyl alcohol film. In addition, the above water washing process may cause swelling of the polyvinyl alcohol film and make subsequent dyeing more uniform.

The absorption axis is formed in the first polyvinyl alcohol layer 104 through the above-mentioned processes such as dyeing and stretching, so that the first polyvinyl alcohol layer 104 has a polarizing effect. In other words, the first polyvinyl alcohol layer 104 can have polarities in any direction. The converted light is converted into polarized light having a specific direction. Specifically, when polarized light having any direction passes through the first polyvinyl alcohol layer 104, polarized light in some directions may be absorbed by the absorption axis of the first polyvinyl alcohol layer 104, while polarized light in other directions may be absorbed. The effect of polarizing light can be achieved through the first polyvinyl alcohol layer 104.

Please continue to refer to FIG. 1. In some embodiments, the second polyvinyl alcohol layer 102 can be used as a retardation film. In the embodiment of the present invention, the second polyvinyl alcohol layer 102 is formed of the same material as the first polyvinyl alcohol layer 104, so the material composition of the polarizing plate 10 can be simplified and the manufacturing process can be simplified, thereby reducing the production cost of the polarizing plate 10. . In some embodiments, the first polyvinyl alcohol layer 104 and the second polyvinyl alcohol layer 102 are both formed of polyvinyl alcohol. However, since the role of the second polyvinyl alcohol layer 102 is to provide a proper phase difference, they are different. The first polyvinyl alcohol layer 104 and the second polyvinyl alcohol layer 102 described above are not dyed.

In some embodiments, the first polyvinyl alcohol layer 104 with dyed polyvinyl alcohol may have a first chromaticity (x1, y1). For example, x1 may be -1 to -2, and y1 may be 2 to 5; The second polyvinyl alcohol layer 102 with undyed polyvinyl alcohol may have a second chromaticity (x2, y2). For example, x2 may be 0 and y2 may be 0. In some embodiments, (x1-x2) <-1 and (y1-y2)> 2.

The production of the second polyvinyl alcohol layer 102 as a retardation film may generally include processes such as water washing, swelling, stretching, and drying. For example, the transparent and colorless polyvinyl alcohol film may be stretched along the second main stretching direction according to the second stretching factor (for example, 1 to 5 times, preferably 3 to 5 times), so that the polyvinyl alcohol film The length becomes 1 to 5 times the original length, preferably 3 to 5 times to form the second polyvinyl alcohol layer 102. The above-mentioned extension process may be uniaxial extension or biaxial extension. In the biaxial extension process, the second main extension direction of the second polyvinyl alcohol layer 102 is defined as a direction with a larger extension multiple. For example, the above-mentioned stretching process may be a wet stretching process (for example, a stretching process in an aqueous solution of boric acid, zinc sulfate, zinc chloride, or the like) or a dry stretching process (for example, stretching by a tenter). According to requirements, a water washing process is performed on the polyvinyl alcohol film to wash the dirt on the surface of the polyvinyl alcohol film.

In some embodiments, the second polyvinyl alcohol layer 102 formed of the same material (eg, polyvinyl alcohol) as the first polyvinyl alcohol layer 104 does not have a polarizing effect. In other words, the second polyvinyl alcohol layer 102 may Let polarized light in either direction pass (ie, no polarization effect is produced). Specifically, the second polyvinyl alcohol layer 102 is not dyed, and therefore, an absorption axis is not formed during the extension process.

In some embodiments, the first extension factor is greater than the second extension factor. In some embodiments, the thickness of the first polyvinyl alcohol layer 104 extended according to the first extension multiple may be 0.1 μm to 50 μm, preferably 0.1 μm to 30 μm; the second polyvinyl alcohol layer extended according to the second extension multiple. The thickness of 102 may be 1 μm to 60 μm, and preferably 1 μm to 45 μm. In other words, the thickness of the second polyvinyl alcohol layer 102 formed by a smaller extension factor is greater than the thickness of the first polyvinyl alcohol layer 104 formed by a larger extension factor.

Generally speaking, the materials used for the protective layer on one side of the polarizing substrate are usually Triacetate Cellulose (TAC), Polymethylmethacrylate (PMMA), and Polyethylene Terephthalate. (Polyethylene Terephthalate, PET), Polypropylene (PP), Cyclo Olefin Polymer (COP) or Polycarbonate (PC). The thickness ranges from 60 μm to 100 μm. Therefore, the structure of the polarizing plate (the second polyvinyl alcohol layer 102 formed by the same material as the polarizing substrate (for example, polyvinyl alcohol) is used instead of the traditional protective layer) for the display device (such as a liquid crystal display or OLED displays), in addition to compensating the phase difference value to increase the viewing angle of the display device, the overall thickness of the polarizing plate can be reduced to facilitate the thinning of the display device. For example, the total thickness of the polarizing plate 10 can be reduced to 180 μm or less, and preferably 80 μm to 130 μm.

In some embodiments, the in-plane phase difference value of the second polyvinyl alcohol layer 102 as a phase difference mode may be 30 nm to 90 nm, and the thickness direction phase difference value may be 120 nm to 300 nm, where the in-plane phase difference value and The phase difference in the thickness direction can be determined by the extension multiple. The above-mentioned phase difference value enables the polarizing plate 10 to achieve better optical performance when used in combination with a vertical alignment liquid crystal (VA liquid crystal).

In other embodiments, the in-plane phase difference value of the second polyvinyl alcohol layer 102 may be 0 to 90 nm, and the thickness direction phase difference value may be 0 to 300 nm. The above-mentioned phase difference value makes the polarizing plate 10 and the twist direction Column liquid crystal (Twisted Nematic liquid crystal, TN liquid crystal for short) can achieve better optical performance when used in combination.

For example, n _{y of the} first polyvinyl alcohol layer 104 and the second polyvinyl alcohol layer 102 may be 1.39 to 1.69, n _x may be 1.41 to 1.71, and the refractive index in the thickness direction may be 1.41 to 1.71. In some embodiments, the birefringence difference (Δ n = (n _x -n _y )) of the first polyvinyl alcohol layer 104 is greater than the birefringence difference of the second polyvinyl alcohol layer 102. For example, the birefringence difference of the first polyvinyl alcohol layer 104 may be 0.03 to 0.5, more preferably 0.06 to 0.24; the birefringence difference of the second polyvinyl alcohol layer 102 may be 0.01 to 0.1, and more preferably 0.02 to 0.05.

In some embodiments, the light transmittance of the first polyvinyl alcohol layer 104 may be greater than 40% (for example: 40.99% to 49.99%) and the light transmittance of the second polyvinyl alcohol layer 102 may be greater than 90% (for example: 90% to 99.9%), and the haze may be less than 1% (for example, 0.1% to 0.99%). In some embodiments, the ratio of the light transmittance of the second polyvinyl alcohol layer 102 and the first polyvinyl alcohol layer 104 is greater than 2, thereby allowing the polarizing plate 10 to have better optical effects.

In some embodiments, the second polyvinyl alcohol layer 102 is directly bonded to the first polyvinyl alcohol layer 104 with an adhesive layer (not shown), that is, the second polyvinyl alcohol layer 102 and the first polyvinyl alcohol No other optical film or functional film is interposed between the layers 104. In some embodiments, the adhesive layer is a transparent adhesive layer made of an aqueous adhesive, wherein the material of the adhesive comprises polyvinyl alcohol powder. In some embodiments, the adhesive layer includes a photo-curable adhesive. The photocurable adhesive material is selected from the group consisting of acrylic resin, polyester resin, polycarbonate resin, and amorphous polyolefin resin. The photocurable adhesive material further includes a photopolymerizable compound.

In some embodiments, in the polarizing plate 10, the second main extension direction of the second polyvinyl alcohol layer 102 may be substantially perpendicular to the first main extension direction of the first polyvinyl alcohol layer 104, and the first polyvinyl alcohol layer The extension factor of 104 is greater than the extension factor of the second polyvinyl alcohol layer 102, thereby achieving better optical effects. It should be noted that "substantially vertical" in this case means that the angle between the two directions is 85 degrees to 95 degrees, preferably 88 degrees to 92 degrees, and more preferably 90 degrees.

In addition, according to use requirements or process requirements, the second polyvinyl alcohol layer 102 may include a plasticizer, a dispersant, an ultraviolet absorber, an infrared absorber, a refractive index adjuster, a filler, an inorganic polymer, and an organic compound, as necessary. Polymers, defoamers, lubricants, antioxidants, acid scavengers, free radical scavengers, conductivity increasers, thickeners, anti-fading agents, preservatives, chemical stabilizers, gas permeability reducing agents, water Permeability reducing agent, antimicrobial agent, anticaking agent, combination of the above, or other appropriate additives.

For example, the above plasticizers may include plasticizers based on unsaturated and / or saturated alicyclic or heterocyclic di- or polycarboxylic acid esters or urethanes (eg, tricyclohexyltri Carbamate, di-2-naphthyl-1,4-cyclohexane dicarboxylate, tetra-3-methylphenyltetrahydrofuran-2,3,4,5-tetracarboxylate, tetrabutyl -1,2,3,4-cyclopentane tetracarboxylic acid ester, triphenyl-1,3,5-cyclohexyl tricarboxylic acid ester, 1,2-cyclohexane dicarboxylic acid diisononyl ester, Triphenylbenzene-1,3,5-tetracarboxylate), citric acid-based plasticizers (e.g. ethyl triethyl citrate or ethyl butyl citrate, ethyl citrate Trimethyl ester), polyether-based plasticizers, phosphate-based plasticizers (e.g., triphenyl phosphate, tricresyl phosphate, bis (diethyl phosphate) butylene Ester, bis (diphenyl phosphate) ethylene ester, diphenyl diphenyl phosphate, bis (dibutyl phosphate) phenylene ester, bis (diphenyl phosphate) phenylene ester, bisphenol A -Diphenyl phosphate, bis (xylyl phosphate) phenylene ester, diphenyl phosphate- (2-ethylhexyl) phosphate, octyl phosphate Diphenyl or triethyl phosphate), plasticizers based on phthalic acid (e.g., diethyl phthalate, dimethyl phthalate, diphthalate Methoxyethyl ester, dioctyl phthalate, dibutyl phthalate, bis (2-propylheptyl) phthalate, bis (2-ethyl phthalate) Hexyl) ester or dicyclohexyl phthalate, dicyclohexyl terephthalate, methyl phthalate-methyl glycolate, ethyl phthalate-ethyl glycolate, (Propyl phthalate-propyl glycolate, butyl phthalate-butyl glycolate, glycerides, such as glyceryl triacetate), plasticization based on aliphatic dicarboxylates Agents (e.g., dioctyladipat, dicyclohexyladipat, or diphenylsuccinat), combinations thereof, or other appropriate Plasticizer.

For example, the above-mentioned ultraviolet absorbent may include Tinuvin 326 (2-tertiary-butyl-6- (5-chloro-benzotriazol-2-yl) -4-methyl-phenol = 2- (5- Chloro (2hydro) -benzotriazol-2-yl) -4- (methyl) -6- (tertiary-butyl) phenol = `` bumetriazole ''), Tinuvin 327 (2,4-di -Tertiary-butyl-6- (5-chlorobenzotriazol-2-yl) -phenol), Uvinul 2049 (2,2-dihydroxy-4,4-dimethoxybenzophenone), Uvinul D-50 (2,2 ', 4,4'-tetrahydroxybenzophenone), a combination of the above, or other appropriate ultraviolet absorbers.

For example, the infrared absorbing agent may include a metal chelate, a quinone, a Squarilium compound, a cyan dye, an aluminum compound, a methine compound, a dimethylene compound, a combination thereof, or other appropriate materials.

Please continue to refer to FIG. 1, the adhesive layer 100 is located below the second polyvinyl alcohol layer 102. For example, the adhesive layer 100 may include a pressure sensitive adhesive (PSA) or other suitable materials, which may have a function of fixing or protecting. In some applications of the polarizing plate 10, the adhesive layer 100 is adhered to the surface of a substrate sandwiching a display medium layer (such as a liquid crystal layer or an organic light emitting layer).

In some embodiments, a protective layer is not included between the adhesive layer 100 and the first polyvinyl alcohol layer 104, and the total thickness of the polarizing plate 10 can be reduced or the material composition of the polarizing plate 10 can be simplified. In addition, the adhesive layer 100 can directly contact the second polyvinyl alcohol layer 102, that is, no other optical film or functional film is interposed between the adhesive layer 100 and the second polyvinyl alcohol layer 102.

Please continue to refer to FIG. 1, the protective layer 106 is disposed on the first side 104 a of the first polyvinyl alcohol layer 104. A suitable material may be selected to form the protective layer 106 according to requirements. For example, the protective layer 106 may be formed of a plastic film having excellent transparency, mechanical strength, thermal stability, moisture blocking property, or isotropic property. In some embodiments, the protective layer 106 may include triacetate, COP (Cyclo olefin polymer), polyester resin, polyether resin, polyfluorene resin, polycarbonate resin, polyamide resin, polyurethane Amine resins, polyolefin resins, acrylic resins, cellulose resins, polyarylate resins, polystyrene resins, polyacrylic resins, combinations thereof, or other appropriate materials. In addition, the protective layer 106 may be formed using a thermosetting resin such as acrylic, urethane-based, urethane-based, epoxy-based, or silicone-based, or a UV-curable resin.

In some embodiments, the polarizing plate 10 may further include other single or multiple protective or functional optical film layers, such as optical gain, alignment, compensation, steering, orthogonal, diffusion, protection, anti-adhesion, resistance Scraping, anti-glare, reflection suppression, high refractive index, and other helpful layers may be, for example, an alignment liquid crystal layer having characteristics such as controlled viewing angle compensation or birefraction, an easily-bonded processing layer, a hard coating layer, and anti-reflection Layer, anti-adhesive layer, diffusion layer, anti-glare layer and other surface treatment layers.

In summary, the polarizing plate in this case replaces the protective layer of the traditional polarizing plate with a retardation film (especially the inner protective layer provided closer to the polarizing substrate), and uses the same material as the polarizing substrate to form the above retardation film. To simplify the material composition of the polarizer. In addition, the retardation film of the polarizing plate of the present case can have a proper in-plane retardation value and a thickness direction retardation value. Therefore, when used in a display device, the display device can have good optical performance. The following description will apply the present polarizing plate Application examples for display devices.

Please refer to FIG. 2, which illustrates a display device 20 according to some embodiments of the present invention, which includes a display medium layer 200, a first substrate 202 and a second substrate 204 sandwiching the display medium layer 200. For example, the display device 20 may be a liquid crystal display device or an organic light-emitting diode (Organic Light-Emitting Diode, OLED) display device. In other words, the display medium layer 200 may be a liquid crystal layer or an organic light emitting layer.

In some embodiments, if the display medium layer 200 is a liquid crystal layer, the display device 20 may include a first polarizing plate 206 and a second polarizing plate 208 sandwiching the display medium layer 200, the first substrate 202 and the second substrate 204. In some embodiments, if the display medium layer 200 is an organic light emitting layer, the display device 20 may include a first polarizing plate 206 disposed on the first substrate 202 or a second polarizing plate 208 disposed on the second substrate 204.

In some embodiments, the aforementioned liquid crystal layer may adopt an in-plane switching (IPS) mode liquid crystal, a vertical alignment liquid crystal (VA), or a twisted nematic liquid crystal (TN). ) And other driving methods.

For example, the first substrate 202 may be an active matrix substrate, which is provided with a switching element (such as a thin film transistor) that controls the electro-optical characteristics of a display medium (such as a liquid crystal layer or an organic light emitting layer), and the switching element described above The second substrate 204 may be a color filter substrate (if the display medium is a liquid crystal layer), and is provided with a color filter. However, the above-mentioned color filter may be provided on an active matrix substrate.

In the display device 20, the first polarizing plate 206 and / or the second polarizing plate 208 are the polarizing plate 10 according to the embodiment of the present invention, so that the display device 20 has the advantages of simplifying the material composition, reducing the thickness, reducing the cost, or improving the optical performance. In some embodiments, the second polyvinyl alcohol layer (not shown) in the first polarizing plate 206 and / or the second polarizing plate 208 is closer to the display medium layer 200 than the first polyvinyl alcohol layer (not shown).

For example, the phase difference value of the display medium layer 200 may be 310 nm to 370 nm. In some embodiments, the display medium layer 200 is a vertical alignment type liquid crystal. Therefore, polarized light having a phase difference value of 30 nm to 90 nm and a thickness phase difference value of 120 nm to 300 nm in the second polyvinyl alcohol layer 102 may be used. The plate 10 enables the display device 20 to achieve better optical performance. In other embodiments, the display medium layer 200 is a twisted nematic liquid crystal, so the in-plane phase difference value of the second polyvinyl alcohol layer 102 can be 0 to 90 nm, and the phase difference value of the thickness direction is 0 to 300 nm. The polarizing plate 10 allows the display device 20 to achieve better optical performance.

In summary, the polarizing plate of the embodiment of the present invention replaces the protective layer of the traditional polarizing plate with a retardation film, and uses the same material as the polarizing substrate to form the retardation film. Therefore, the material composition of the polarizing plate can be simplified and reduced. The complexity of the process and equipment reduces the production cost of polarizing plates. In addition, by providing the phase retardation film with an appropriate phase difference value, a display device using the polarizing plate of the embodiment of the present invention has good optical performance.

Although the present invention has been disclosed above with several preferred embodiments, it is not intended to limit the present invention. Any person with ordinary knowledge in the technical field can make any changes without departing from the spirit and scope of the present invention. And retouching, so the scope of protection of the present invention shall be determined by the scope of the attached patent application.

Claims (14)

    A polarizing plate includes: a first polyvinyl alcohol (PVA) layer; a protective layer on a first side of the first polyvinyl alcohol layer; and a second polyvinyl alcohol layer on the first On a second side of one of the first polyvinyl alcohol layers, a thickness of the second polyvinyl alcohol layer is greater than a thickness of the first polyvinyl alcohol layer.         The polarizing plate according to item 1 of the scope of patent application, wherein the first polyvinyl alcohol layer is formed by extending along a first main extension direction, and the second polyvinyl alcohol layer is formed by extending along a second main extension direction. Formed, wherein the first main extension direction is substantially perpendicular to the second main extension direction.         The polarizing plate according to item 2 of the scope of patent application, wherein the first polyvinyl alcohol layer is formed by extending at a first extension multiple, and the second polyvinyl alcohol layer is formed by extending at a second extension multiple, wherein the The first extension multiple is greater than the second extension multiple.         The polarizing plate according to item 1 of the scope of the patent application, wherein the first polyvinyl alcohol layer includes dyed polyvinyl alcohol, and the second polyvinyl alcohol layer includes undyed polyvinyl alcohol.         The polarizing plate according to item 1 of the scope of the patent application, wherein the ratio of the light transmittance of the second polyvinyl alcohol layer to the light transmittance of the first polyvinyl alcohol layer is greater than two.         The polarizing plate according to item 1 of the scope of the patent application, wherein the birefringence difference of the first polyvinyl alcohol layer is greater than the birefringence difference of the second polyvinyl alcohol layer.         The polarizing plate according to item 1 of the scope of patent application, wherein the first polyvinyl alcohol has a first chromaticity (x1, y1), and the second polyvinyl alcohol layer has a second chromaticity (x2, y2) , Where (x1-x2) <-1 and (y1-y2)> 2.         The polarizing plate according to item 1 of the scope of the patent application, wherein the phase difference within the film surface of the second polyvinyl alcohol layer is 30 nm to 90 nm, and the phase difference between the thickness direction of the second polyvinyl alcohol layer is 120 nm to 300nm.         The polarizing plate according to item 1 of the scope of patent application, wherein the thickness of the second polyvinyl alcohol layer is 1 μm to 60 μm.         The polarizing plate according to item 1 of the patent application scope further includes an adhesive layer, and the first polyvinyl alcohol layer and the second polyvinyl alcohol layer are directly bonded with the adhesive layer.         A display device includes: a display medium layer; a first substrate and a second substrate, sandwiching the display medium layer; and the polarizing plate according to any one of claims 1 to 10 of a patent application scope, disposed on On the first substrate or the second substrate.         The display device according to item 11 of the scope of patent application, wherein the display medium layer is a vertical alignment type liquid crystal, the phase difference within the film plane of the second polyvinyl alcohol layer in the polarizing plate is 30 nm to 90 nm, and the The phase difference in thickness direction of the second polyvinyl alcohol layer is 120 nm to 300 nm.         The display device according to item 11 in the scope of the patent application, wherein the display medium layer is a twisted nematic liquid crystal, and the phase difference within the film plane of the second polyvinyl alcohol layer in the polarizing plate is 0 to 90 nm. The phase difference in thickness direction of the second polyvinyl alcohol layer is 0 to 300 nm.         The display device according to item 11 of the scope of patent application, wherein the second polyvinyl alcohol layer in the polarizing plate is closer to the display medium layer than the first polyvinyl alcohol layer.