Polarizing plate with high transmittance

Abstract

According to the polarizing plate with the high transmittance, the optical film layer is additionally arranged in the polarizing plate, and the purpose of improving the transmittance of the polarizing plate is achieved by adjusting the refractive index of the optical film layer and enabling the refractive index of the optical film layer to be matched with the refractive index of other layers such as the polarizing layer and the protective film.

Description

Technical Field

[0001] The present invention relates to the technical field of polarizing plates, and in particular to a polarizing plate with high transmittance and a preparation method thereof. Background Art

[0002] The optical properties of polarizing plates include three main performance indicators: polarization, transmittance and hue. Others include UV protection and transmittance, total reflectance and diffuse reflectance of semi-transparent polarizing plates. In the use of general LCD products, the higher the polarization and transmittance performance indicators, the better. The higher the polarization and transmittance, the higher the display efficiency of the LCD display device and the lower the relative energy consumption. In recent years, the development of liquid crystal display devices has been moving towards low energy consumption, thinness and high added value. As one of the important components of LCD display screens, improving the transmittance of polarizing plates also plays an important role in reducing the energy consumption of liquid crystal displays.

[0003] In order to meet the demand for improved transmittance, polarizing plate manufacturers generally adopt the method of reducing the ratio of dyeing liquid KI to obtain a relatively high transmittance. However, for conventional iodine-dyed polarizing plate products, polarization and transmittance are a pair of contradictory parameters. Improving transmittance in this way will lead to a decrease in the polarization of the polarizing plate, which will eventually affect the contrast of the liquid crystal display device and the display effect. Another commonly used way to improve the transmittance of polarizing plates is to use high-stretching ratio stretching PVA technology. This method can improve the transmittance of polarizing plates while keeping the polarization at a high level. When the expected transmittance is high, a large stretching ratio will be used, and a large stretching ratio is very likely to cause breakage during production, that is, the increase in transmittance beyond a certain range conflicts with product productivity. Although improvements can be made in terms of materials, using PVA with stronger stretchability, such as PVA materials based on polyvinyl alcohol with a high degree of polymerization, when the stretching ratio needs to be further increased, PVA will still break frequently during stretching, resulting in the inability to mass-produce products and even affecting the stability of the appearance optical quality. It may not be possible to overcome productivity by adjusting parameters based on existing equipment. In other words, mass production requires lowering the requirements for high transmittance and high polarization levels.

[0004] Therefore, improving the transmittance and polarization degree of polarizing films is still the main problem currently faced. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a polarizing plate with high transmittance and high polarization degree in view of the shortcomings of the prior art.

[0006] To solve the above technical problems, the present invention can be implemented through the following technical solutions:

[0007] The present application provides a polarizing plate, which at least includes a polarizing layer, a protective film layer on at least one side of the polarizing layer, and an optical film layer. The refractive index of the polarizing layer is between 1.4 and 1.6, the refractive index of the protective film layer is between 1.3 and 1.6, and the refractive index of the optical film layer is between 1.3 and 1.6.

[0008] As a further improvement of the present application, the haze of the optical film layer < 3%, the total light transmittance of the optical film layer > 90%, the thickness of the optical film layer is 3 - 30000 nm, the thickness of the protective film layer is 3 - 80 μm, and the thickness of the polarizing layer is 1 - 50 μm.

[0009] As a further improvement of the present application, the protective film layer can be a film prepared from any commercially available optical material, such as a cellulose triacetate (TAC) film, a polyethylene terephthalate (PET) film, an acrylic (PMMA) film, a cyclopentene (COP) and its derivatives or modified film products, a polyimide (PI) film, a polystyrene (PS) and its derivatives film products, a polyvinyl alcohol (PVA) film, a polyester (PE) film, an epoxy resin (ER) film, a polyurethane (PU) film, a polysilane film, etc.

[0010] As a further improvement of the present application, the polarizing layer is a dichroic type polyvinyl alcohol-based polarizer for liquid crystal displays. The polarizing layer is prepared by adsorbing dichroic substances such as iodine and dichroic dyes on a polyvinyl alcohol-based thin film, and then performing steps such as dyeing and stretching. Steps such as swelling, crosslinking, and water washing can be added as needed. The polarizing layer can be, for example, a 10 - μm thick polarizing layer prepared by the lamination technology of Nitto Denko.

[0011] As a further improvement of the present application, in order to fix the polarizing plate to the panel surface, the polarizing plate can further include an adhesive layer. The adhesive layer can use any existing known technology, such as commercially available acrylate mixtures, and at the same time, the optical film layer described in the present application can also be used.

[0012] As a further improvement of the present application, the optical film layer is disposed on the surface of the polarizing layer away from the protective film layer, or the optical film layer is disposed on the surface of the protective film layer away from the polarizing layer.

[0013] As a further improvement of the present application, when the optical film layer is disposed on the side of the polarizer protective film layer away from the polarizer, preferably, the refractive index of the optical film layer is lower than that of the protective film layer. More preferably, the lower the refractive index of the optical film layer, the better, and the thinner the thickness of the optical film layer, the better. When the optical film layer is disposed between the protective film layer and the polarizer, preferably, the refractive index of the optical film layer is higher than that of the protective film layer and higher than that of the layer in contact with the other side of the optical film layer.

[0014] As a further improvement of the present application, the polarizing plate further includes a functional film layer.

[0015] As a further improvement of the present application, the functional film layer is any one of a retardation compensation film, a light diffusing film, a wide viewing angle film, a brightness enhancement film, and a reflective film.

[0016] As a further improvement of the present application, the optical film layer is disposed on either side of the functional film layer.

[0017] As a further improvement of the present application, the optical film layer is cured from the following components: a main prepolymer resin mixture, a solvent, and an additive. Preferably, the curing method is photocuring or thermal curing.

[0018] As a further improvement of the present application, the main prepolymer resin mixture is at least one of a polyester resin and an acrylic resin.

[0019] As a further improvement of the present application, the weight average molecular weight of the acrylic resin is 200,000 to 1,000,000.

[0020] As a further improvement of the present application, the acrylic resin is selected from one or more of (meth)acrylic acid alkyl esters, acrylic acid alkyl esters, (meth)acrylic acid epoxy esters, acrylic acid hydroxyalkyl esters, (meth)acrylic acid alkyl esters containing carboxyl groups, alkyl acrylates, and acrylic esters containing sulfonates. Preferably, the acrylic ester containing sulfonate may be an acrylic ester containing sodium 2-methyl-2-propene-1-sulfonate, an acrylic ester containing aryl sulfonate, and an acrylic ester containing 2-propene-1-sulfonate.

[0021] As a further improvement of the present application, the acrylic resin is an epoxy acrylate resin containing epoxy groups. The copolymerization of the epoxy acrylate resin containing epoxy groups can improve the high-temperature stability of the polyester resin because the epoxy rings in the epoxy acrylate resin containing epoxy groups dissociate at high temperatures and crosslink through additional polymerization therebetween to improve the high-temperature durability of the main chain of the polyester resin.

[0022] As a further improvement of the present application, the weight-average molecular weight of the polyester resin is 30,000 to 100,000, and the polyester resin is prepared by the esterification reaction and polycondensation reaction of polybasic acid and polyhydric alcohol.

[0023] As a further improvement of the present application, any existing known technology can be used for the solvent, and it is selected and used according to the type and adhesion of the main prepolymer resin mixture, including ester compounds, ketone compounds, such as any one of methyl acetate, ethyl acetate, butyl acetate, and methyl ethyl ketone, etc., or it can also be water. Further, the addition amount of the solvent can be determined according to the required viscosity and the thickness of the optical film layer. When the required viscosity is low, or when the thickness of the optical film layer is about 3 to 500 nm, the addition amount of the solvent should be appropriately increased; when the required viscosity is high, or when the thickness of the optical film layer is about 500 to 30,000 nm, the addition amount of the solvent should be appropriately reduced.

[0024] As a further improvement of the present application, the auxiliary agent is at least one of a diluting monomer, an initiator, a dispersant, a compatibilizer, a leveling agent, a surfactant, an antistatic agent, a silane coupling agent, a thickening agent, an anti-coloring agent, a coloring agent, a defoaming agent, a flame retardant, an ultraviolet absorber, a tackifier, a polymerization inhibitor, an antioxidant, and a surface modifier. The auxiliary agent can be appropriately added according to the purposes of increasing the hardness of the internal scattering layer, suppressing curing shrinkage, and controlling the refractive index, etc.

[0025] As a further improvement of the present application, any existing known technology can be used for the initiator, which can be selected from photo-polymerizable initiators, or can further include thermo-polymerizable initiators on this basis. The photo-polymerizable initiator is a radical initiator or a cationic initiator. The radical initiator includes but is not limited to any one or a combination of several of 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, methyl benzoylformate, phenylglyoxylic acid 2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester, phenylglyoxylic acid 2-[2-hydroxy-ethoxy]-ethyl ester, α-dimethoxy-α-phenylacetophenone, 2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone, 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, and diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide; The cationic initiator includes but is not limited to any one or a combination of several of diaryliodonium salts, triarylsulfonium salts, and arene-iron salt compounds, and specifically can be selected from any one or a combination of several of diphenyl-4-(phenylthio)phenylsulfonium hexafluorophosphate, (4-hydroxyphenyl)methylbenzylsulfonium tetrakis(pentafluorophenyl)borate, 4-(4-biphenylthio)phenyl-4-biphenylylphenylsulfonium tetrakis(pentafluorophenyl)borate, 4-(phenylthio)phenyl diphenylsulfonium phenyltris(pentafluorophenyl)borate, diphenyl[4-(phenylthio)phenyl]sulfonium tris(pentafluoroethyl)trifluorophosphate, diphenyl[4-(phenylthio)phenyl]sulfonium tetrakis(pentafluorophenyl)borate, diphenyl[4-(phenylthio)phenyl]sulfonium hexafluorophosphate, 4-(4-biphenylthio)phenyl-4-biphenylylphenylsulfonium tris(pentafluoroethyl)trifluorophosphate, bis[4-(diphenylsulfonium)phenyl]sulfide phenyltris(pentafluorophenyl)borate, [4-(2-thioxanthonylthio)phenyl]phenyl-2-thioxanthonylsulfonium phenyltris(pentafluorophenyl)borate, and 4-(phenylthio)phenyl diphenylsulfonium hexafluoroantimonate.

[0026] As a further improvement of the present application, any existing known technology can be used for the dispersant, and preferably it is silica.

[0027] As a further improvement of the present application, any existing known technology can be used for the compatibilizer, such as one or more of cyclic anhydride type compatibilizers, carboxylic acid type compatibilizers, epoxy type compatibilizers, oxazoline type compatibilizers, imide type compatibilizers, and isocyanate type compatibilizers.

[0028] As a further improvement of the present application, any existing known technology can be used for the leveling agent, such as one or more of acrylic leveling agents, silicone leveling agents, and fluorocarbon leveling agents. The resin mixture for the optical film layer added with the leveling agent can make the surface of the coating film have smoothness and stain resistance during coating or drying, and can endow scratch resistance; the leveling agent is preferably a composition containing a fluorine group or a silicon group.

[0029] As a further improvement of the present application, the polarizing layer is a PVA polarizing layer, and the PVA polarizing layer is prepared by the following chemical or physical treatment steps: swelling the PVA original film, with the swelling temperature being 22 - 35°C; performing dyeing after swelling, the dyeing tank contains KI / I2 / HB, the KI concentration is 0 - 1%, the I2 concentration is 0 - 0.5%, the HB concentration is 0 - 1%, the pH is 3 - 5, the dyeing temperature is 22 - 35°C, and the residence time is 50 - 90 seconds; performing crosslinking after dyeing, the KI concentration in the crosslinking tank is 1.8 - 2.5%, the HB concentration is 3.5 - 4.5%, the pH is 3 - 5, the temperature is 25 - 45°C, and the residence time is 20 - 40 seconds; performing stretching after crosslinking, the KI concentration in the stretching tank is 3.6 - 5.0%, the HB concentration is 3.3 - 4.5%, the total stretching ratio is 6 - 7 times, the stretching temperature is 55 - 65°C, and the residence time is 50 - 100 seconds; performing hue adjustment after stretching, the KI concentration in the adjustment tank is 3.6 - 4.5%, the HB concentration < 1.5%, the pH is 2.5 - 4.0, the temperature is 25 - 35°C, and the residence time is 20 - 40 seconds; finally, entering the oven to adjust the moisture content, preferably the moisture content < 13.5%.

[0030] As a further improvement of the present application, the chemical or physical treatment steps for the polarizing layer and the optical film layer include: placing them in an oven for drying, the oven temperature is 70 - 100°C, the residence time is 10 - 60 seconds, and the time interval from the optical film layer coming out of the oven to being laminated with the polarizing layer is 30 - 280 seconds.

[0031] The beneficial effects of the present application are as follows: An optical film layer is added to the polarizing plate of the present application. By adjusting the refractive index of the optical film layer and matching it with the refractive indices of other layers such as the polarizing layer and the protective film layer, the purpose of improving the transmittance of the polarizing plate is achieved. Description of the Drawings

[0032] Figure 1 It is a schematic structural diagram of an embodiment of the polarizing plate of the present application;

[0033] Figure 2 It is a schematic structural diagram of another embodiment of the polarizing plate of the present application;

[0034] Figure 3 It is a schematic structural diagram of another embodiment of the polarizing plate of the present application;

[0035] Figure 4 Schematic structural diagram of another embodiment of the polarizing plate of the present application;

[0036] Figure 5 Schematic structural diagram of the polarizing plate of Embodiment 1 of the present application. Detailed implementation manners

[0037] The present invention will be described in detail below in conjunction with the embodiments shown in the drawings. However, these embodiments do not limit the present invention, and structural, method, or functional transformations made by those of ordinary skill in the art based on these embodiments are all included within the protection scope of the present invention.

[0038] The present application provides a polarizing plate, which at least includes a polarizing layer, a protective film layer on at least one side of the polarizing layer, and an optical film layer. The refractive index of the polarizing layer is between 1.4 and 1.6, the refractive index of the protective film layer is between 1.3 and 1.6, and the refractive index of the optical film layer is between 1.3 and 1.6.

[0039] In an alternative embodiment, the haze of the optical film layer < 3%, the total light transmittance of the optical film layer > 90%, the thickness of the optical film layer is 3 - 30000 nm, the thickness of the protective film layer is 3 - 80 μm, and the thickness of the polarizing layer is 1 - 50 μm.

[0040] In an alternative embodiment, the protective film layer can be a film prepared from any commercially available optical material, such as a cellulose triacetate (TAC) film, a polyethylene terephthalate (PET) film, an acrylic (PMMA) film, a cyclopentene (COP) and its derivatives or modified film products, a polyimide (PI) film, a polystyrene (PS) and its derivatives film products, a polyvinyl alcohol (PVA) film, a polyester (PE) film, an epoxy resin (ER) film, a polyurethane (PU) film, a polysilane film, etc.

[0041] In an alternative embodiment, the polarizing layer is a dichroic type polyvinyl alcohol-based polarizer for liquid crystal displays. The polarizing layer is prepared by adsorbing dichroic substances such as iodine and dichroic dyes on a polyvinyl alcohol-based thin film, and then performing steps such as dyeing and stretching. Steps such as swelling, crosslinking, and water washing can be added as needed. The polarizing layer can be, for example, a 10-μm-thick polarizing layer prepared by the lamination technology of Nitto Denko.

[0042] In an alternative embodiment, in order to fix the polarizing plate to the panel surface, the polarizing plate can further include an adhesive layer. The adhesive layer can use any existing known technology, such as commercially available acrylate mixtures, and at the same time, the optical film layer described in the present application can also be used.

[0043] In an alternative embodiment, the optical film layer is disposed on a surface of the polarizing layer away from the protective film layer, or the optical film layer is disposed on a surface of the protective film layer away from the polarizing layer.

[0044] In an alternative embodiment, when the optical film layer is disposed on a side of the polarizing layer protective film away from the polarizing layer, preferably, the refractive index of the optical film layer is lower than that of the protective film layer. More preferably, the lower the refractive index of the optical film layer, the better, and the thinner the thickness of the optical film layer, the better; when the optical film layer is disposed between the protective film layer and the polarizing layer, preferably, the refractive index of the optical film layer is higher than that of the protective film layer and higher than that of the layer in contact with the other side of the optical film layer.

[0045] In an alternative embodiment, the polarizing plate further includes a functional film layer.

[0046] In an alternative embodiment, the functional film layer is any one of a retardation compensation film, a light diffusing film, a wide viewing angle film, a brightness enhancement film, and a reflective film.

[0047] In an alternative embodiment, the optical film layer is disposed on either side of the functional film layer.

[0048] In an alternative embodiment, the optical film layer is cured from the following components: a main prepolymer resin mixture, a solvent, and an additive. Preferably, the curing method is photocuring or thermal curing.

[0049] In an alternative embodiment, the main prepolymer resin mixture is at least one of a polyester resin and an acrylic resin.

[0050] In an alternative embodiment, the weight average molecular weight of the acrylic resin is 200,000 to 1,000,000. Preferably, when the optical resin layer is used as an adhesive layer between the polarizing plate and the panel, the optical film layer mixture before curing contains at least an acrylic main agent, a diluting monomer, an antistatic agent, a coupling agent, a curing agent, etc. with a weight average molecular weight of about 200,000 to 1,000,000.

[0051] In an alternative embodiment, the acrylic resin is selected from one or more of (meth)acrylic acid alkyl esters, acrylic acid alkyl esters, (meth)acrylic acid epoxy esters, acrylic acid hydroxyalkyl esters, (meth)acrylic acid alkyl esters containing a carboxyl group, alkyl acrylates, and acrylate esters containing a sulfonate. Preferably, the acrylate ester containing a sulfonate can be an acrylate ester containing sodium 2-methyl-2-propene-1-sulfonate, an acrylate ester containing arylsulfonate sodium, and an acrylate ester containing 2-propene-1-sulfonate.

[0052] In an alternative embodiment, the acrylic resin is an epoxy acrylate resin containing epoxy groups. The copolymerization of the epoxy acrylate resin containing epoxy groups can improve the high-temperature stability of the polyester resin because the epoxy rings in the epoxy acrylate resin containing epoxy groups dissociate at high temperatures and crosslink through additional polymerization therebetween to improve the high-temperature durability of the main chain of the polyester resin.

[0053] In an alternative embodiment, the polyester resin has a weight-average molecular weight of 30,000 to 100,000 and is prepared by an esterification reaction and a polycondensation reaction of a polybasic acid and a polyol.

[0054] In an alternative embodiment, any existing known technology can be used for the solvent, which is selected and used according to the type and adhesion of the main body prepolymer resin mixture, including any one of ester compounds, ketone compounds, such as methyl acetate, ethyl acetate, butyl acetate, and methyl ethyl ketone, etc., and water can also be used. Further, the addition amount of the solvent can be determined according to the required viscosity and the thickness of the optical film layer. When the required viscosity is low, or when the thickness of the optical film layer is about 3 to 500 nm, the addition amount of the solvent should be appropriately increased; when the required viscosity is high, or when the thickness of the optical film layer is about 500 to 30,000 nm, the addition amount of the solvent should be appropriately decreased.

[0055] In an alternative embodiment, the additives are at least one of a diluent monomer, an initiator, a dispersant, a compatibilizer, a leveling agent, a surfactant, an antistatic agent, a silane coupling agent, a thickener, a curing agent, an anti-coloring agent, a coloring agent, a defoaming agent, a flame retardant, an ultraviolet absorber, a tackifier, a polymerization inhibitor, an antioxidant, and a surface modifier. The additives can be appropriately added according to the purposes of increasing the hardness of the internal scattering layer, suppressing curing shrinkage, and controlling the refractive index, etc.

[0056] In an alternative embodiment, the initiator can be any known existing technology, and can be selected from photo-polymerizable initiators, and can also include thermal-polymerizable initiators on this basis. The photo-polymerizable initiator is a radical initiator or a cationic initiator. The radical initiator includes but is not limited to any one or a combination of several of 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, methyl benzoylformate, phenyl acetate-2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester, phenyl acetate-2-[2-hydroxy-ethoxy]-ethyl ester, α-dimethoxy-α-phenylacetophenone, 2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-butanone, 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, and diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide; the cationic initiator includes but is not limited to any one or a combination of several of diaryliodonium salts, triarylsulfonium salts, and ferrocenium salt compounds, and specifically can be selected from any one or a combination of several of diphenyl-4-(phenylthio)phenylsulfonium hexafluorophosphate, (4-hydroxyphenyl)methylbenzylsulfonium tetrakis(pentafluorophenyl)borate, 4-(4-biphenylthio)phenyl-4-biphenylylphenylsulfonium tetrakis(pentafluorophenyl)borate, 4-(phenylthio)phenyl diphenylsulfonium phenyltris(pentafluorophenyl)borate, diphenyl[4-(phenylthio)phenyl]sulfonium tris(pentafluoroethyl)trifluorophosphate, diphenyl[4-(phenylthio)phenyl]sulfonium tetrakis(pentafluorophenyl)borate, diphenyl[4-(phenylthio)phenyl]sulfonium hexafluorophosphate, 4-(4-biphenylthio)phenyl-4-biphenylylphenylsulfonium tris(pentafluoroethyl)trifluorophosphate, bis[4-(diphenylsulfonium)phenyl]sulfide phenyltris(pentafluorophenyl)borate, [4-(2-thioxanthonylthio)phenyl]phenyl-2-thioxanthonylsulfonium phenyltris(pentafluorophenyl)borate, and 4-(phenylthio)phenyl diphenylsulfonium hexafluoroantimonate.

[0057] In an alternative embodiment, the dispersant can be any known existing technology, and is preferably silica.

[0058] In an alternative embodiment, the diluent monomer can be any known one. Here, because the acrylate resin is used in the examples, the monomer can also be an acrylate monomer.

[0059] In an alternative embodiment, the compatibilizer can be any known existing technology, such as one or more of cyclic anhydride type compatibilizers, carboxylic acid type compatibilizers, epoxy type compatibilizers, oxazoline type compatibilizers, imide type compatibilizers, and isocyanate type compatibilizers.

[0060] In an alternative embodiment, any existing known technology can be used for the leveling agent, such as one or more of an acrylic leveling agent, a silicone leveling agent, and a fluorocarbon leveling agent. The resin mixture for the optical film layer added with the leveling agent can make the surface of the coating film have smoothness and stain resistance during coating or drying, and can endow scratch resistance; the leveling agent is preferably a composition containing a fluorine group or a silicon group.

[0061] In an alternative embodiment, the polarizing layer is a PVA polarizing layer, and the PVA polarizing layer is prepared by the following chemical or physical treatment steps: swelling the PVA original film, and the swelling temperature is 22-35°C; after swelling, dyeing is carried out, and the dyeing tank contains KI / I2 / HB, the concentration of KI is 0-1%, the concentration of I2 is 0-0.5%, the concentration of HB is 0-1%, the pH is 3-5, the dyeing temperature is 22-35°C, and the residence time is 50-90 seconds; after dyeing, crosslinking is carried out, and the concentration of KI in the crosslinking tank is 1.8-2.5%, the concentration of HB is 3.5-4.5%, the pH is 3-5, the temperature is 25-45°C, and the residence time is 20-40 seconds; after crosslinking, stretching is carried out, and the concentration of KI in the stretching tank is 3.6-5.0%, the concentration of HB is 3.3-4.5%, the total stretching ratio is 6-7 times, the stretching temperature is 55-65°C, and the residence time is 50-100 seconds; after stretching, hue adjustment is carried out, and the concentration of KI in the adjustment tank is 3.6-4.5%, the concentration of HB < 1.5%, the pH is 2.5-4.0, the temperature is 25-35°C, and the residence time is 20-40 seconds; finally, enter the oven to adjust the moisture content, and preferably the moisture content < 13.5%.

[0062] In an alternative embodiment, the chemical or physical treatment steps for the polarizing layer and the optical film layer include: placing them in an oven for drying, the oven temperature is 70-100°C, the residence time is 10-60 seconds, and the time interval from the optical film layer coming out of the oven to being laminated with the polarizing layer is 30-280 seconds.

[0063] In an alternative embodiment, the polarizing plate with high transmittance and high polarization degree has a multi-layer structure, and its effective structure at least includes the above-mentioned optical film layer, upper protective film layer, and polarizing layer, as Figure 1 shown; it may also include a lower protective film layer, as Figure 2 shown; other film layers can also be selectively added as needed, for example, further combined with a 1 / 2λ retardation film stack, a light diffusing film, a wide-angle film, a brightness enhancement film, a reflective film, or other functional coatings, etc., and its structure is as Figure 3 and Figure 4 shown; however, it should be recognized that the present application is not limited to this.

[0064] The present application will be further described below in conjunction with examples and comparative examples.

[0065] Example 1

[0066] A. Preparation of Resin Mixture A1 for Optical Film Layer

[0067] First, 70% deionized water was added to 29.99% epoxy acrylate resin, and then 0.01% dispersant silica was added. After stirring at 1200 rpm for 50 min, resin mixture A1 was obtained.

[0068] B. Preparation of Optical Film Layer B1

[0069] The obtained resin mixture A1 was sprayed on one side D of a PMMA optical film layer (Okura OHX) with a refractive index of 1.49, dried in an oven at 80 °C, and uniaxially stretched in the TD direction simultaneously to obtain optical film layer B1. The thickness of the optical film layer was measured to be 5 nm, and the refractive index was 1.37.

[0070] C. Preparation of Polarizer C1

[0071] The schematic structural diagram of polarizer C1 is as Figure 5 shown, including an outer protective film, an upper optical film layer, a protective film layer on the polarizing layer, a polarizing layer, a protective film layer under the polarizing layer, a lower optical film layer, an adhesive layer, and a release film, which are stacked in sequence.

[0072] The preparation method of the polarizer includes the following steps:

[0073] Step 1. Chemical or physical treatment of the polarizing layer: The prepared PVA film was immersed in pure water at 30 °C for 80 s; then it was immersed in an aqueous solution with a pH of about 4.0, a temperature of 30 °C, and a mass concentration of KI 0.25%, I2 0.02%, and HB 0.6% for 70 s for dyeing; the dyed PVA was immersed in an aqueous solution with a pH of about 3.2, a temperature of 40 °C, and a mass concentration of KI 2.0% and HB 4.0% for 30 s; then the colored PVA film was placed in an aqueous solution with a temperature of 60 °C and a mass concentration of KI 4.1% and HB 3.8% and immersed, and a three-stage stretching operation was completed within 60 s, with a total stretching ratio of about 6.0 times; finally, it entered an oven with an average temperature of 50 °C.

[0074] The moisture content of the polarizing layer was measured to be about 13%.

[0075] Step 2. Chemical or physical treatment of the protective film layer on / under the polarizing layer: The protective film layer on / under the polarizing layer was corona-treated with a power of 2.5 kW and then entered an oven with an average temperature of 85 °C for 30 s in three sections.

[0076] Step 3: On the front and back sides of the prepared polarizing layer, the upper and lower protective film layers of the polarizing layer are adhered through an ultraviolet curable adhesive. The distances from the upper and lower protective film layers of the polarizing layer to the laminating table are calculated as 210 seconds according to the predetermined machine speed. After lamination, it enters a 10-section oven for drying for 150 seconds, and the oven temperatures are 70°C, 70°C, 70°C, 70°C, 70°C, 75°C, 75°C, 80°C, 80°C, 80°C respectively.

[0077] Optical film layer B1 is used for the upper optical film layer outside the upper protective film layer of the polarizing layer, and optical film layer B1 is also used for the lower optical film layer outside the lower protective film layer of the polarizing layer. The bonding surfaces with the polarizing layer are all non-D surfaces.

[0078] Step 4: A PET release film is attached to the outer side surface of the lower optical film layer away from the lower protective film layer of the polarizing layer, and at the same time, PSA adhesive is coated. After aging, an outer protective film is laminated on the upper protective film layer of the polarizing layer.

[0079] Example 2

[0080] A. Preparation of resin mixture A2 for optical film layer

[0081] First, acrylate resin with a content of 14.1% and ethyl acetate as a solvent with a content of 17.0% are added to polyester resin with a content of 67.7%. Then, a leveling agent with a content of 1.2% is added respectively. After stirring at a speed of 1200 rpm for 50 min, resin mixture A2 is obtained.

[0082] B. Preparation of optical film layer B2

[0083] The obtained resin mixture A2 is coated on a D surface on one side of a PET optical film layer with a refractive index of 1.58, and dried in an oven at 80°C to obtain optical film layer B2. The measured thickness of the optical film layer is 200 nm, and the refractive index is 1.45.

[0084] C. Preparation of polarizing plate C2

[0085] Optical film layer B2 is used for the upper optical film layer outside the upper protective film layer of the polarizing layer, and optical film layer B1 is used for the lower optical film layer outside the lower protective film layer of the polarizing layer. Except for this, the polarizing plate is prepared in the same manner as in Example 1.

[0086] Example 3

[0087] A. Preparation of resin mixture A3 for optical film layer

[0088] 14.1% by content of acrylate resin and 17.1% by content of diluting monomer were added to 66.7% by content of polyester resin, and then 1.1% by content of photoinitiator and 1.0% by content of leveling agent were added respectively. After stirring at 1200 rpm for 50 min, resin mixture A3 was obtained.

[0089] B. Preparation of optical film layer B3

[0090] The obtained resin mixture A3 was coated on one side D surface of a PET optical film (TOYOBO TA048) with a refractive index of 1.58, and dried in an oven at 80 °C to obtain optical film layer B3. The thickness of the optical resin layer was measured to be 200 nm, and the refractive index was 1.53.

[0091] C. Preparation of polarizer C3

[0092] The optical film layer outside the protective film layer on the polarizer layer used optical film layer B3, and the protective film layer under the polarizer layer used a commercially available COP optical film layer (ZEON e-ZB12). Except for this, the polarizer was prepared in the same manner as in Example 1.

[0093] Example 4

[0094] A. Preparation of resin mixture A4 for optical film layer

[0095] 26.05% by content of acrylate resin and 40.0% by content of solvent ethyl acetate were added to 14.9% by content of polyester resin, and then 4.0% by content of coupling agent and 15% by content of curing agent were added respectively. Finally, 0.05% by content of antistatic agent was added. After stirring at 1200 rpm for 50 min, resin mixture A4 was obtained.

[0096] B. Preparation of polarizer C4

[0097] The protective film layer on the polarizer layer used a commercially available PET optical film, the protective film layer under the polarizer layer used a commercially available COP optical film, and the adhesive layer was replaced by an optical film layer prepared from resin mixture A4. Except for this, the polarizer was prepared in the same manner as in Example 1.

[0098] The thickness of the optical film layer was measured to be 25000 nm, and the refractive index was 1.60.

[0099] Comparative Example 1

[0100] A. Preparation of polarizer C5

[0101] For the protective film layer on the polarizing layer, a commercially available PET optical film is used. For the protective film layer under the polarizing layer, a commercially available COP optical film is used. For the adhesive, a commercially available PSA adhesive is used. Except for this, the polarizing plate is prepared in the same manner as in Example 1.

[0102] Comparative Example 2

[0103] A. Preparation of Polarizing Plate C6

[0104] Directly use a commercially available general - specification polarizing plate for LCD - IPS.

[0105] Comparative Example 3

[0106] A. Preparation of Polarizing Plate C7

[0107] Directly use a commercially available high - specification polarizing plate for LCD - IPS.

[0108] Comparative Example 4

[0109] B. Preparation of Polarizing Plate C8

[0110] Directly use a commercially available general - specification polarizing plate for LCD - VA.

[0111] Comparative Example 5

[0112] B. Preparation of Polarizing Plate C9

[0113] Directly use a commercially available high - specification polarizing plate for LCD - VA.

[0114] The test results related to the products are shown in Table 1 and Table 2. The test methods are as follows:

[0115] Test Example 1

[0116] <Transmittance Test>

[0117] Cut the polarizing plates prepared in Examples 1 - 4 and Comparative Examples 1 - 5 into pieces of 30 mm * 40 mm size, and use JASCO (V - 7100) to measure the transmittance of the polarizing plates.

[0118] Test Example 2

[0119] <Polarization Degree Test>

[0120] Cut the polarizing plates prepared in Examples 1 - 4 and Comparative Examples 1 - 5 into pieces of 30 mm * 40 mm size, and use JASCO (V - 7100) to measure the polarization degree of the polarizing plates.

[0121] Test Example 3

[0122] <Thickness Test>

[0123] The polarizing plates prepared in Examples 1 to 4 and Comparative Examples 1 to 5 were cut into triangles with a size of about 10 mm * 15 mm. After sample preparation by a slicing machine, the thickness of the optical resin layer was measured by SEM.

[0124] Test Example 4

[0125] <Refractive index test>

[0126] The polarizing plates prepared in Examples 1 to 4 and Comparative Examples 1 to 5 were cut into a size of 30 mm * 40 mm and tested using an Abbe refractometer.

[0127] Table 1 Test results related to the product (transmittance, degree of polarization)

[0128]

[0129] As can be seen from Table 1, compared with Comparative Examples 1 to 5, Examples 1 to 4 have better optical performance, with a transmittance of up to 44.3 - 44.6% and a degree of polarization of up to 99.998%. This is due to the use of the polarizing plate structure of the present invention.

[0130] Table 2 Test results related to the product (thickness, refractive index)

[0131]

[0132] As can be seen from Table 2, compared with Comparative Examples 3 / 5, Comparative Example 1 has better optical performance, with a transmittance of up to 43.5% and a degree of polarization of up to 99.998%. This is due to the use of the polarizing plate preparation process of the present invention.

[0133] In summary, by providing a high - transmittance polarizing plate including an optical film layer, the present invention can solve the problem of difficult improvement of optical performance without affecting its appearance quality performance. At the same time, using the polarizing plate preparation process provided by the present invention, a polarizing plate product can be manufactured that not only meets the ultra - high optical requirements of downstream customers but also has both high productivity and high quality.

[0134] It should be noted that the above - mentioned are only preferred embodiments for explaining the present invention and are not intended to limit the present invention in any form. Therefore, any modification or change to the present invention made under the same inventive spirit should still be included in the scope intended to be protected by the present invention.

Claims

1. A polarizing plate, characterized in that, The polarizing plate at least includes a polarizing layer, a protective film layer on at least one side of the polarizing layer, and an optical film layer. The refractive index of the polarizing layer is between 1.4 and 1.6, the refractive index of the protective film layer is between 1.3 and 1.6, and the refractive index of the optical film layer is between 1.3 and 1.

6.

2. The polarizing plate according to claim 1, wherein The haze of the optical film layer is < 3%, the total light transmittance of the optical film layer is > 90%, the thickness of the optical film layer is 3 - 30000 nm, the thickness of the protective film layer is 3 - 80 μm, and the thickness of the polarizing layer is 1 - 50 μm.

3. The polarizing plate according to claim 2, wherein The optical film layer is disposed on the surface of the polarizing layer away from the protective film layer, or the optical film layer is disposed on the surface of the protective film layer away from the polarizing layer.

4. The polarizing plate according to claim 1, characterized in that, The polarizing plate further includes a functional film layer.

5. The polarizing plate according to claim 4, wherein The functional film layer is any one of a retardation compensation film, a light diffusing film, a wide viewing angle film, a brightness enhancement film, and a reflective film.

6. The polarizing plate according to claim 4, wherein The optical film layer is disposed on either side of the functional film layer.

7. The polarizing plate according to any one of claims 1-6, characterized in that, The optical film layer is cured from the following components: a main prepolymer resin mixture, a solvent, and an auxiliary agent.

8. The polarizing plate according to claim 7, wherein, The main prepolymer resin mixture is at least one of a polyester resin and an acrylic resin.

9. The polarizing plate according to claim 8, wherein The weight average molecular weight of the acrylic resin is 200,000 - 1,000,000.

10. The polarizing plate according to claim 9, characterized in that, The acrylic resin is selected from one or more of (meth)acrylic acid alkyl esters, acrylic acid alkyl esters, (meth)acrylic acid epoxy esters, acrylic acid hydroxyalkyl esters, (meth)acrylic acid alkyl esters containing carboxyl groups, alkyl acrylic acids, and acrylic acid esters containing sulfonates.

11. The polarizing plate according to claim 10, wherein The acrylic resin is an epoxy acrylate resin containing epoxy groups.

12. The polarizing plate according to claim 8, wherein The weight average molecular weight of the polyester resin is 30000 - 100000, and the polyester resin is prepared by an esterification reaction and a polycondensation reaction of a polybasic acid and a polyhydric alcohol.

13. The polarizing plate according to claim 7, wherein The solvent is any one of water, methyl acetate, ethyl acetate, butyl acetate, and methyl ethyl ketone.

14. The polarizing plate according to claim 7, wherein The auxiliary agent is at least one of a diluting monomer, an initiator, a dispersant, a compatibilizer, a leveling agent, a surfactant, an antistatic agent, a silane coupling agent, a thickening agent, an anti-coloring agent, a coloring agent, a defoaming agent, a flame retardant, an ultraviolet absorber, a tackifier, a polymerization inhibitor, an antioxidant, and a surface modifier.

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