Polarizing plate, method for manufacturing polarizer, and method for manufacturing polarizing plate

Abstract

To suppress polyene formation in a polarizer made of a polyvinyl alcohol resin film.SOLUTION: A polarizing plate 100 includes a polarizer 101 in which a dichroic dye is adsorbed and aligned on a polyvinyl alcohol-based resin film, and a protective film 103 laminated on at least one surface of the polarizer 101 via an adhesive layer 102. The adhesive layer 102 contains a urea compound. The polarizer 101 contains a radical scavenger. The urea compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives. The radical scavenger is a hindered amine compound.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polarizing plate, a method for manufacturing a polarizer, and a method for manufacturing a polarizing plate. [Background technology]

[0002] It is known that when a polarizing plate having a polarizer made of a polyvinyl alcohol-based resin film is placed in a high-temperature environment, polyenization of the polyvinyl alcohol proceeds, resulting in a change in optical properties.

[0003] Patent Document 1 discloses a polarizer containing a radical scavenger as a polarizer capable of suppressing polyenization, and describes the polarizer as a polarizing film. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2021 / 210342 Summary of the Invention [Problem to be solved by the invention]

[0005] There is a demand for a polarizing plate that can suppress the polyenization of polyvinyl alcohol even in a high-temperature environment. [Means for solving the problem]

[0006] The present invention includes the following inventions. [Invention 1] A polarizing plate comprising: a polarizer in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film; and a protective film laminated on at least one surface of the polarizer via an adhesive layer, the adhesive layer contains a urea compound, the polarizer contains a radical scavenger, the urea compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives; The polarizing plate, wherein the radical scavenger is a hindered amine compound.

[0007] [Invention 2] A polarizing plate comprising: a polarizer in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film; and a protective film laminated on at least one surface of the polarizer, the polarizer contains a urea compound and a radical scavenger, the urea compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives; The polarizing plate, wherein the radical scavenger is a hindered amine compound.

[0008] [Invention 3] The polarizing plate according to [Invention 1] or [Invention 2], wherein the hindered amine compound is a compound represented by formula (1).

[0009] [ka]

[0010] [In formula (1), R 1 represents an oxy radical group, a hydrogen atom, a hydroxy group, an alkyl group having 1 to 30 carbon atoms which may have a hydroxy group, or an alkoxy group having 1 to 30 carbon atoms which may have a hydroxy group.

[0011] R 2 , R 3 , R 4 and R 5 each independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. n represents 0 or 1.

[0012] X represents any organic group. [Invention 4] R1 The polarizing plate according to [Invention 3], wherein is an oxy radical group.

[0013] [Invention 5] A method for producing a polarizer from a polyvinyl alcohol-based resin film, comprising: a step of immersing the polyvinyl alcohol-based resin film in a solution containing a urea compound and a radical scavenger, the urea compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives; The method for producing a polarizer, wherein the radical scavenger is a hindered amine compound.

[0014] [Invention 6] A method for manufacturing a polarizing plate including a polarizer and a protective film, a polarizer production step of producing the polarizer from the polyvinyl alcohol-based resin film, the step including a step of immersing the polyvinyl alcohol-based resin film in a solution containing a radical scavenger; a protective film bonding step of bonding the protective film to at least one surface of the polarizer via an adhesive layer formed from an adhesive composition containing a urea compound, the urea compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives; The method for producing a polarizing plate, wherein the radical scavenger is a hindered amine compound. [Effects of the Invention]

[0015] By suitably suppressing the polyenization of polyvinyl alcohol, the high-temperature durability of the polarizing plate can be improved. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a polarizing plate. [Figure 2]FIG. 2 is a schematic diagram showing a polarizer manufacturing apparatus used in the polarizer manufacturing method. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, embodiments of a polarizing plate, a method for manufacturing a polarizer, and a method for manufacturing a polarizing plate will be described. <Polarizing plate> The polarizing plate 100 includes a polarizer 101. The polarizer 101 contains a radical scavenger, as will be described later.

[0018] As shown in FIG. 1, the polarizing plate 100 includes a polarizer 101 and a first protective film 103 laminated on one surface thereof with an adhesive layer 102 interposed therebetween. As shown in FIG. 1, polarizing plate 100 may have second protective film 104 laminated on the other surface of polarizer 101 via bonding layer 102.

[0019] In the polarizing plate 100, a protective film may be laminated on at least one surface of the polarizer 101 via an attachment layer 102. That is, only the first protective film 103 may be laminated, or only the second protective film 104 may be laminated.

[0020] The attachment layer 102 may be a pressure-sensitive adhesive layer or an adhesive layer, and is preferably an adhesive layer. At least one of the polarizer 101 and the adhesive layer contains a urea compound, as will be described later.

[0021] <Polarizer> The polarizer is a uniaxially stretched polyvinyl alcohol (PVA) resin film to which a dichroic dye is adsorbed and aligned. The polyvinyl alcohol resin may be, for example, a saponified polyvinyl acetate resin. The saponification degree of the polyvinyl acetate resin is preferably 85 mol% or more, more preferably 90 mol% or more, and even more preferably 99 mol% or more.

[0022] Examples of polyvinyl acetate resins that can be used include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate with other copolymerizable monomers. Examples of the copolymerizable other monomers include unsaturated carboxylic acids, olefins, vinyl ethers, and unsaturated sulfonic acids.

[0023] The degree of polymerization of the polyvinyl alcohol resin is preferably 1,000 or more and 10,000 or less, and more preferably 1,500 or more and 5,000 or less. The polyvinyl alcohol resin may be modified. Examples of the modified polyvinyl alcohol resin include polyvinyl formal, polyvinyl acetal, and polyvinyl butyral modified with aldehydes.

[0024] Examples of the dichroic dye include iodine and water-soluble dichroic dyes. The thickness of the polarizer is not particularly limited, but is, for example, 1 μm or more, preferably 5 μm or more, more preferably 8 μm or more, and even more preferably 11 μm or more, and may be 50 μm or less, preferably 30 μm or less, more preferably 20 μm or less, or 15 μm or less.

[0025] The polarizer preferably has a boron content of 0.5% by mass or more, more preferably 1.5% by mass or more, even more preferably 2.5% by mass or more, and may even have a boron content of 3.5% by mass or more. The boron content of the polarizer is preferably 5.5% by mass or less, more preferably 5.0% by mass or less, and even more preferably 4.5% by mass or less. By having a boron content of 4.5% by mass or less, shrinkage of the polarizer caused by heating can be suppressed.

[0026] [Radical Scavenger] The polarizer contains a radical scavenger. For example, the radical scavenger can be incorporated into the polarizer during the manufacturing process of the polarizer. Examples of methods for incorporating the radical scavenger into the polarizer include immersing a PVA-based resin film in a solution containing the radical scavenger, or spraying, flowing, or dropping a solution containing the radical scavenger onto a PVA-based resin film. When the adhesive layer or pressure-sensitive adhesive layer laminated on the polarizer in the polarizing plate contains a radical scavenger, part of the radical scavenger contained in the adhesive layer or pressure-sensitive adhesive layer may be part of the radical scavenger that has migrated to the polarizer.

[0027] The content of the radical scavenger in the polarizer is preferably 20% by mass or less. From the viewpoint of suppressing a decrease in the single-piece transmittance due to coloration of the polarizer in a high-temperature environment, the content of the radical scavenger in the polarizer is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, and even more preferably 0.1% by mass or more, and is preferably 15% by mass or less, more preferably 12% by mass or less, and even more preferably 10% by mass or less. The content of the radical scavenger in the polarizer can be measured, for example, by analyzing a solution obtained by dissolving the polarizer using liquid chromatography.

[0028] The radical scavenger is a hindered amine compound. The hindered amine compound is a water-soluble hindered amine compound that can be dissolved in an amount of, for example, 1 part by mass or more in 100 parts by mass of water at 25° C. The hindered amine compound may be used alone or in combination of two or more kinds.

[0029] From the viewpoint of being able to efficiently capture radicals generated in the polyenation reaction, the hindered amine compound preferably has a molecular weight of 1,000 or less, more preferably 500 or less, and even more preferably 300 or less.

[0030] The hindered amine compound of the present embodiment is a secondary amine or tertiary amine in which an alkyl group is substituted on the carbon atom adjacent to the amino group to sterically protect the amino group, and examples thereof include compounds having an organic group having the following structure:

[0031] The hindered amine compound is, for example, a compound represented by the following formula (1).

[0032] [ka]

[0033] [In formula (1), R 1 represents an oxy radical group, a hydrogen atom, a hydroxy group, an alkyl group having 1 to 30 carbon atoms which may have a hydroxy group, or an alkoxy group having 1 to 30 carbon atoms which may have a hydroxy group.

[0034] R 2 , R 3 , R 4 and R 5 each independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. n represents 0 or 1.

[0035] X represents any organic group. The hindered amine compounds are known compounds, and include, for example, 2,2,6,6-tetraalkylpiperidine compounds, acid addition salts thereof, or complexes of these with metal compounds, as described in columns 5 to 11 of U.S. Pat. No. 4,619,956 and columns 3 to 5 of U.S. Pat. No. 4,839,405.

[0036] The organic group represented by X in the above formula (1) is not particularly limited, but examples of compounds having an organic group as X include compounds represented by the following formulas (2) to (5).

[0037] [ka]

[0038] [In formula (2), R 1 , R 2 , R 3 , R 4 , R 5 and n have the same meaning as in formula (1). R 6 represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an acyl group having 1 to 10 carbon atoms, or an aryl group having 1 to 10 carbon atoms.]

[0039] [ka]

[0040] [In formula (3), R 1 , R 2 , R 3 , R 4 , R 5 and n have the same meaning as in formula (1). R 7 and R 8 each independently represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an acyl group having 1 to 10 carbon atoms, or an aryl group having 1 to 10 carbon atoms.]

[0041] [ka]

[0042] [In formula (4), R 1 , R 2 , R 3 , R 4 , R 5 and n have the same meaning as in formula (1). R 9 , R 10 and R 11each independently represents a hydrogen atom, an amino group, a hydroxy group, an alkyl group having 1 to 10 carbon atoms, an acyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms, and the alkyl group, acyl group, alkoxy group, and aryl group may have a substituent.]

[0043] [ka]

[0044] [In formula (5), R 1 , R 2 , R 3 , R 4 , R 5 and n have the same meaning as in formula (1). R 12 represents a hydrogen atom, an amino group, a hydroxy group, an alkyl group having 1 to 10 carbon atoms, an acyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, or an aryl group having 6 to 10 carbon atoms, and the alkyl group, acyl group, alkoxy group, and aryl group may have a substituent.] In formulas (1) to (5), R 1 As the group, from the viewpoint of efficiently suppressing polyenization of polyvinyl alcohol, an oxy radical group, a hydrogen atom, a hydroxy group, or an alkyl group is preferred, and an oxy radical group is more preferred.

[0045] R 2 ~R 5 From the viewpoints of availability and water solubility, alkyl groups having 1 to 6 carbon atoms are preferred, and alkyl groups having 1 to 3 carbon atoms are more preferred. From the viewpoint of availability, n is preferably 1.

[0046] In equation (2), R 6 From the viewpoints of availability and water solubility, a hydrogen atom or an alkyl group having 1 to 10 carbon atoms is preferred, and a hydrogen atom is more preferred. In equation (3), R 7 and R8 From the viewpoints of availability and water solubility, each of them is preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and more preferably a hydrogen atom.

[0047] In equation (4), R 9 ~R 11 From the viewpoints of availability and water solubility, a hydrogen atom or an alkyl group having 1 to 10 carbon atoms is preferred. In equation (5), R 12 From the viewpoints of availability and water solubility, a hydroxy group, an amino group, or an alkoxy group is preferred.

[0048] Examples of the substituent that the alkyl group, acyl group, alkoxy group and aryl group may have include an amino group and a hydroxy group. Specific examples of the hindered amine compound that is a radical scavenger include compounds represented by the following formulas.

[0049] [ka]

[0050] [Urea compound] The polarizer may contain a urea compound. A method for incorporating a urea compound into a polarizer includes incorporating a urea compound into a polarizer during the production of the polarizer using a solution containing a urea compound, similar to the above-mentioned method for incorporating a radical scavenger into a polarizer. In a polarizing plate, when an adhesive layer described below contains a urea compound, the urea compound contained in the polarizer may be a urea compound that has been partially transferred from the adhesive layer to the polarizer.

[0051] The urea compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives. One urea compound may be used alone, or two or more urea compounds may be used in combination.

[0052] The content of the urea compound in the polarizer is, for example, 0.005% by mass or more and 20% by mass or less, preferably 0.01% by mass or more, further preferably 0.1% by mass or more, and further preferably 10% by mass or less. The content of the urea compound in the polarizer can be measured, for example, by analyzing a solution obtained by dissolving the polarizer using liquid chromatography.

[0053] (urea derivative) A urea derivative is a compound in which at least one of the four hydrogen atoms of a urea molecule is substituted with a substituent. In this case, the substituent is not particularly limited, but is preferably a substituent consisting of carbon, hydrogen, and oxygen atoms.

[0054] Specific examples of the urea derivatives include mono-substituted ureas such as methylurea, ethylurea, propylurea, butylurea, isobutylurea, N-octadecylurea, 2-hydroxyethylurea, hydroxyurea, acetylurea, allylurea, 2-propynylurea, cyclohexylurea, phenylurea, 3-hydroxyphenylurea, (4-methoxyphenyl)urea, benzylurea, benzoylurea, o-tolylurea, and p-tolylurea.

[0055] Examples of disubstituted ureas include 1,1-dimethylurea, 1,3-dimethylurea, 1,1-diethylurea, 1,3-diethylurea, 1,3-bis(hydroxymethyl)urea, 1,3-tert-butylurea, 1,3-dicyclohexylurea, 1,3-diphenylurea, 1,3-bis(4-methoxyphenyl)urea, 1-acetyl-3-methylurea, 2-imidazolidinone (ethyleneurea), and tetrahydro-2-pyrimidinone (propyleneurea).

[0056] Examples of 4-substituted ureas include tetramethylurea, 1,1,3,3-tetraethylurea, 1,1,3,3-tetrabutylurea, 1,3-dimethoxy-1,3-dimethylurea, 1,3-dimethyl-2-imidazolidinone, and 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone.

[0057] (thiourea derivatives) A thiourea derivative is a compound in which at least one of the four hydrogen atoms of a thiourea molecule is substituted with a substituent. In this case, the substituent is not particularly limited, but is preferably a substituent consisting of carbon, hydrogen, and oxygen atoms.

[0058] Specific examples of the thiourea derivatives include mono-substituted thioureas such as N-methylthiourea, ethylthiourea, propylthiourea, isopropylthiourea, 1-butylthiourea, cyclohexylthiourea, N-acetylthiourea, N-allylthiourea, (2-methoxyethyl)thiourea, N-phenylthiourea, (4-methoxyphenyl)thiourea, N-(2-methoxyphenyl)thiourea, N-(1-naphthyl)thiourea, (2-pyridyl)thiourea, o-tolylthiourea, and p-tolylthiourea.

[0059] Examples of disubstituted thioureas include 1,1-dimethylthiourea, 1,3-dimethylthiourea, 1,1-diethylthiourea, 1,3-diethylthiourea, 1,3-dibutylthiourea, 1,3-diisopropylthiourea, 1,3-dicyclohexylthiourea, N,N-diphenylthiourea, N,N′-diphenylthiourea, 1,3-di(o-tolyl)thiourea, 1,3-di(p-tolyl)thiourea, 1-benzyl-3-phenylthiourea, 1-methyl-3-phenylthiourea, N-allyl-N′-(2-hydroxyethyl)thiourea, and ethylenethiourea.

[0060] Tri-substituted thioureas include trimethylthiourea. Examples of 4-substituted thioureas include tetramethylthiourea and 1,1,3,3-tetraethylthiourea.

[0061] [Metal ions] The polarizer may contain metal ions. Examples of a method for incorporating metal ions into a polarizer include a method in which a PVA-based resin film is immersed in a solution containing a salt of the metal ion when producing the polarizer.

[0062] The metal ions are not limited as long as they are metal ions other than potassium ions, and are preferably ions of metals other than alkali metals. In particular, from the viewpoints of color adjustment and durability, it is preferable to include at least one metal ion of a transition metal such as cobalt, nickel, zinc, chromium, aluminum, copper, manganese, or iron. Among these metal ions, zinc ions are preferred from the viewpoints of color adjustment and heat resistance. Examples of zinc ion salts include zinc halides such as zinc chloride and zinc iodide, zinc sulfate, and zinc acetate.

[0063] <Protective film> The protective film is not particularly limited, and various transparent protective films that can be used in polarizing plates can be employed. Examples of materials that can be used to form the protective film include thermoplastic resins that are excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, and isotropy. Examples of the thermoplastic resins include cellulose ester resins such as triacetyl cellulose, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins such as nylon and aromatic polyamide, polyimide resins, polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymers, (meth)acrylic resins, cyclic polyolefin resins (norbornene resins) having a cyclo- or norbornene structure, polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. The protective film can also be a cured layer formed from a thermosetting resin or ultraviolet-curable resin, such as a (meth)acrylic, urethane, acrylic urethane, epoxy, or silicone resin. Among these, cellulose ester resins, polycarbonate resins, (meth)acrylic resins, cyclic polyolefin resins, and polyester resins are preferred.

[0064] The surface of the protective film to which the polarizer is not attached may be provided with a functional layer such as a hard coat layer, an antireflection layer, an antisticking layer, a diffusion layer, an antiglare layer, etc. The functional layer such as the hard coat layer, the antireflection layer, the antisticking layer, the diffusion layer, or the antiglare layer may be provided in the protective film itself, or may be provided separately as a layer separate from the protective film.

[0065] Either or both of the surface of the protective film to which the polarizer is attached and the surface of the polarizer to which the protective film is attached may be subjected to a surface treatment, such as a corona treatment, a plasma treatment, a primer treatment, or a saponification treatment.

[0066] The thickness of the protective film is not particularly limited, but from the viewpoint of ease of handling in the manufacturing process, it is 1 μm or more, preferably 10 μm or more, and more preferably 30 μm or more, and from the viewpoint of thinning the polarizing plate, it is 200 μm or less, preferably 100 μm or less, more preferably 80 μm or less, and even more preferably 60 μm or less.

[0067] The moisture permeability of the protective film is not particularly limited, but it is preferable that the moisture permeability be, for example, 350 g / (m) at a temperature of 40°C and a relative humidity of 90%. 2 The moisture permeability is, for example, 50 g / (m 2 The moisture permeability can be measured in accordance with the moisture permeability test (cup method) of JIS Z0208.

[0068] The moisture permeability is 50g / (m 2 ·24 hours) or more 350g / (m 2 24 hours) or less, and 80g / (m 2 ·24 hours) or more 300g / (m 2 24 hours) or less is more preferable, and 100g / (m 2 ·24 hours) or more 200g / (m 2 It is even more preferable that the time is 24 hours or less.

[0069] <Laminating layer> The attachment layer, which is an adhesive layer or a pressure-sensitive adhesive layer, may contain a radical scavenger, or may not contain a radical scavenger. The radical scavenger can be appropriately selected from the radical scavengers exemplified above for use in the polarizer.

[0070] <Adhesive layer> As the pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer, any conventionally known pressure-sensitive adhesive composition having excellent optical transparency can be used without particular limitation, and for example, a pressure-sensitive adhesive composition having a base polymer such as an acrylic resin, a urethane resin, a silicone resin, or a polyvinyl ether resin can be used. Among these, a pressure-sensitive adhesive composition having an acrylic resin as a base polymer is preferred, as it is excellent in transparency, adhesive strength, removability, weather resistance, heat resistance, etc. The pressure-sensitive adhesive composition may further contain a crosslinking agent, a silane compound, an antistatic agent, etc.

[0071] <Adhesive layer> The adhesive composition forming the adhesive layer is preferably a resin-containing aqueous adhesive composition. The aqueous adhesive composition is an adhesive composition consisting of an aqueous solution in which adhesive components are dissolved in water, and the solids concentration of the aqueous adhesive composition is preferably 0.5% to 20% by mass, more preferably 1% to 15% by mass.

[0072] Examples of resins contained in the aqueous adhesive composition (or adhesive layer) include urethane resins and polyvinyl alcohol (PVA) resins, with PVA resins being preferred. When a polyvinyl alcohol resin is used as the main component of the aqueous adhesive composition, the polyvinyl alcohol resin may be a polyvinyl alcohol resin such as a partially saponified polyvinyl alcohol or a fully saponified polyvinyl alcohol, or a modified polyvinyl alcohol resin. Examples of the modified polyvinyl alcohol resin include a carboxyl group-modified polyvinyl alcohol resin and an acetoacetyl group-modified polyvinyl alcohol resin.

[0073] The average degree of polymerization of the polyvinyl alcohol resin (preferably an acetoacetyl group-modified polyvinyl alcohol resin) is preferably from 100 to 5500, more preferably from 500 to 4500, from the viewpoint of adhesiveness.

[0074] The degree of saponification of the polyvinyl alcohol resin (preferably an acetoacetyl group-modified polyvinyl alcohol resin) is usually 80 mol % to 100 mol %, and preferably 85 mol % or more.

[0075] The degree of modification (amount of modification) with acetoacetyl groups in the acetoacetyl group-modified polyvinyl alcohol resin is usually 0.1 mol % to 40 mol %, and preferably 0.5 mol % to 20 mol %, from the viewpoint of adhesiveness.

[0076] Among aqueous adhesive compositions, polyvinyl alcohol-based adhesive compositions are preferred, and acetoacetyl-modified polyvinyl alcohol-based adhesive compositions are more preferred. That is, the adhesive layer is preferably a cured layer of an aqueous adhesive composition containing a polyvinyl alcohol-based resin.

[0077] The adhesive may be applied to either the protective film side or the polarizer side, or to both. After lamination, a drying step is performed to form an adhesive layer consisting of a dried coated layer. After the drying step, ultraviolet light or electron beams may be irradiated as necessary.

[0078] The thickness of the adhesive layer is not particularly limited, but is preferably, for example, about 1 nm to 5000 nm, more preferably about 10 nm to 1000 nm, and even more preferably about 10 nm to 300 nm.

[0079] The components that may be contained in the adhesive composition will be described below. [Urea compound] The adhesive composition may contain a urea compound. When at least one of the polarizer and the adhesive composition contains a urea compound, polyenization of polyvinyl alcohol in a high-temperature environment is more easily suppressed. The urea compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives. One urea compound may be used alone, or two or more may be used in combination. Specifically, the urea compound can be appropriately selected from the urea compounds that may be contained in the polarizer. Urea compounds include water-soluble and slightly water-soluble urea compounds, and either type can be used. When a slightly water-soluble urea compound is used in a water-soluble adhesive, it is preferable to devise a dispersion method to prevent an increase in haze after forming the adhesive layer. Urea is preferred as the urea compound.

[0080] The content of the urea compound in the adhesive composition (or adhesive layer) is preferably, for example, in the following range: For example, when the adhesive composition is an aqueous adhesive containing a polyvinyl alcohol-based resin, the content of the urea compound is 0.1 parts by mass or more and 400 parts by mass or less, preferably 1 part by mass or more and 200 parts by mass or less, and more preferably 3 parts by mass or more and 100 parts by mass or less, per 100 parts by mass of the polyvinyl alcohol-based resin.

[0081] [Other ingredients] The adhesive composition may contain a nitric acid compound. The nitric acid compound is not particularly limited, but is preferably a nitrate.

[0082] The adhesive composition may contain an organic solvent. Alcohols are preferred as organic solvents because they are miscible with water, and among alcohols, methanol or ethanol is more preferred. The concentration of the organic solvent in the aqueous adhesive is preferably 10% by mass or more and 70% by mass or less, more preferably 15% by mass or more and 60% by mass or less, and even more preferably 20% by mass or more and 60% by mass or less. Increasing the organic solvent content in the aqueous adhesive composition can reduce the water content. Having an organic solvent concentration of 10% by mass or more can more easily suppress polyenation of polyvinyl alcohol in high-temperature environments. Furthermore, having an organic solvent content of 70% by mass or less can suppress deterioration of color. While some of the above-mentioned urea derivatives have low solubility in water, some have sufficient solubility in alcohol. In this case, one preferred embodiment is to dissolve a urea compound in alcohol to prepare an alcohol solution of the urea compound, and then add the alcohol solution of the urea compound to an aqueous PVA solution to prepare the adhesive.

[0083] The aqueous adhesive composition may contain a crosslinking agent. The crosslinking agent is typically a compound having at least two functional groups per molecule that are reactive with the polymer or other components that make up the adhesive. Examples of such crosslinking agents include alkylenediamines, isocyanates, epoxies, aldehydes, amino-formaldehydes such as methylolmelamine, glyoxal, and glyoxal derivatives. The amount of crosslinking agent in the adhesive is typically about 5 to 60 parts by mass per 100 parts by mass of the polymer or other components that make up the adhesive.

[0084] The aqueous adhesive composition may contain a dicarboxylic acid such as maleic acid or phthalic acid to improve heat resistance. The content of the dicarboxylic acid is preferably 0.01 to 5 parts by mass, more preferably 0.02 to 1 part by mass, per 100 parts by mass of the PVA resin.

[0085] <Polarizer manufacturing method> The method for producing a polarizer includes, for example, a swelling step, a dyeing step, a crosslinking step, a washing step, and a stretching step. The swelling step is a step of swelling an unstretched polyvinyl alcohol-based resin film (raw film) by immersing it in a swelling liquid. The dyeing step is a step of dyeing the polyvinyl alcohol-based resin film after the swelling step by immersing it in a dyeing liquid. The crosslinking step is a step of crosslinking the polyvinyl alcohol-based resin film after the dyeing step by immersing it in a crosslinking liquid. The washing step is a step of washing the polyvinyl alcohol-based resin film. The stretching step is a step of uniaxially stretching the polyvinyl alcohol-based resin film.

[0086] The method for producing a polarizer may further include other treatment steps as necessary, such as a drying step of drying the polyvinyl alcohol-based resin film.

[0087] In the swelling step, dyeing step, crosslinking step, and washing step, the polyvinyl alcohol-based resin film is brought into contact with a treatment liquid. The swelling step, dyeing step, crosslinking step, and washing step may each be a treatment in which the polyvinyl alcohol-based resin film is brought into contact with one treatment liquid, or may each be a treatment in which the polyvinyl alcohol-based resin film is brought into contact with two or more treatment liquids in sequence. Among these, the crosslinking step is preferably a treatment in which the polyvinyl alcohol-based resin film is brought into contact with two or more treatment liquids in sequence.

[0088] The step of immersing a PVA-based resin film in a solution containing a radical scavenger can be carried out simultaneously with steps such as a swelling step, stretching step, dyeing step, crosslinking step, and washing step. A polarizer containing a radical scavenger can be produced by, for example, including a treatment solution containing a radical scavenger in one or more of the swelling step, dyeing step, crosslinking step, washing step, and stretching step. The step of immersing a PVA-based resin film in a solution containing a radical scavenger may be carried out separately from steps such as a swelling step, stretching step, dyeing step, crosslinking step, and washing step.

[0089] The content of the radical scavenger in the polarizer can be controlled by the concentration of the radical scavenger in the solution containing the radical scavenger, the treatment temperature and treatment time with the solution containing the radical scavenger, etc. In particular, when a washing step is performed after the dyeing step, crosslinking step, and stretching step, the washing step can easily adjust the content of the radical scavenger to a desired range, taking into account the treatment conditions in the dyeing step, crosslinking step, stretching step, etc., from the viewpoint of eluting components such as the radical scavenger from the polyvinyl alcohol-based resin film or adsorbing components such as the radical scavenger to the polyvinyl alcohol-based resin film. That is, the step of immersing the PVA-based resin film in a solution containing a radical scavenger is preferably a washing step, and the washing liquid preferably contains a radical scavenger.

[0090] The concentration of the radical scavenger in the solution containing the radical scavenger cannot be determined in general because it is affected by the number of treatments, treatment time, treatment temperature, etc. of each treatment. However, from the viewpoint of efficiently controlling the content of the radical scavenger in the polarizer, the concentration is usually preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, and is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less.

[0091] The step of immersing a PVA-based resin film in a solution containing a urea compound may be performed simultaneously with a swelling step, stretching step, dyeing step, crosslinking step, washing step, or other step, or may be performed as a separate step. A polarizer containing a urea compound can be produced, for example, by using a treatment liquid containing a urea compound in one or more of the swelling step, dyeing step, crosslinking step, washing step, and stretching step. Both the urea compound and the radical scavenger may be contained in a single treatment liquid, or the urea compound and the radical scavenger may be contained in separate treatment liquids. The step of immersing a PVA-based resin film in a solution containing a urea compound is, for example, a washing step, and the washing liquid contains the urea compound.

[0092] The concentration of the urea compound in the solution containing the urea compound cannot be determined in general because it is affected by the number of treatments, treatment time, treatment temperature, etc. of each treatment. However, from the viewpoint of efficiently controlling the content of the urea compound in the polarizer, the concentration is usually preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more, and is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less.

[0093] The method for manufacturing a polarizer according to this embodiment will be described in more detail below with reference to Fig. 2. Fig. 2 shows an example of a polarizer manufacturing apparatus 20 that manufactures a polarizer 101. The polarizer manufacturing apparatus 20 shown in Fig. 2 uses a swelling liquid 14, a dyeing liquid 15, a first cross-linking liquid 16a, a second cross-linking liquid 16b, and a cleaning liquid 17. The polarizer manufacturing apparatus 20 also includes a drying furnace 18, guide rolls 30 to 48, 60, and 61, and nip rolls 70 to 76. By appropriately arranging the guide rolls and nip rolls, a transport path for the polyvinyl alcohol-based resin film can be constructed.

[0094] When manufacturing the polarizer 101, an unstretched polyvinyl alcohol resin film 21 is used. The unstretched polyvinyl alcohol resin film 21 is wound around a roll 22. First, raw film 21 is unwound from roll 22 and transported along the film transport path of polarizer manufacturing apparatus 20. Next, a treatment step is performed in which raw film 21 is immersed in a treatment liquid and then pulled out. A drying step is then performed, whereby long polarizers 101 can be continuously manufactured. Note that the arrow in FIG. 2 indicates the film transport direction.

[0095] Polarizer manufacturing apparatus 20 transports a film using guide rolls 30 to 48, 60, and 61 and nip rolls 70 to 76. The film is then passed through swelling liquid 14, dyeing liquid 15, first cross-linking liquid 16a, second cross-linking liquid 16b, and cleaning liquid 17, which are provided on the film transport path, in that order. Finally, the film is passed through drying oven 18.

[0096] The guide rolls 30-48, 60, and 61 and the nip rolls 70-76 can be placed before, after, or within each processing liquid. This allows the film to be introduced into, immersed in, and withdrawn from the processing liquid efficiently. For example, by providing one or more guide rolls in each processing liquid and transporting the film along these guide rolls, the film can be efficiently immersed in each processing liquid.

[0097] As described above, the swelling liquid 14 may contain a urea compound. The swelling liquid 14 may contain a radical scavenger. As described above, the dyeing liquid 15 may contain a urea compound. The dyeing liquid 15 may contain a radical scavenger. As described above, the first cross-linking liquid 16a may contain a urea compound. The first cross-linking liquid 16a may contain a radical scavenger. As described above, the second cross-linking liquid 16b may contain a urea compound. The second cross-linking liquid 16b may contain a radical scavenger. As described above, the cleaning liquid 17 may contain a urea compound. The cleaning liquid 17 may contain a radical scavenger.

[0098] In the polarizer manufacturing method, a swelling step, a dyeing step, a crosslinking step, a cleaning step, and a drying step are performed in this order using a polarizer manufacturing apparatus 20. The swelling step, dyeing step, crosslinking step, cleaning step, drying step, and stretching step will be described in detail below.

[0099] [Stretching process] The stretching step in the method for producing a polarizer will be described. The guide rolls 30-48, 60, and 61 of the polarizer manufacturing apparatus 20 are used to support the film being transported and change the film transport direction. The nip rolls 70-76 are used to press and clamp the film being transported and to apply a driving force to the film by their rotation. Furthermore, by arranging the nip rolls 70-76 before and after each treatment liquid, a difference in peripheral speed can be created between the nip rolls 70-76 located before and after one or more treatment liquids. By creating a difference in peripheral speed between the nip rolls 70-76, it is possible to perform inter-roll stretching. In other words, a uniaxial stretching process can be performed as a stretching process during the period in which a series of treatment processes from the swelling process to the washing process are performed, i.e., before, after, or during one or more treatment processes.

[0100] The total stretching ratio of the polarizer 101, i.e., the final cumulative stretching ratio, based on the original film 21 is, for example, 4 times or more and 8 times or less, preferably 4.5 times or more and 7 times or less, and more preferably 5 times or more and 6.5 times or less.

[0101] [Swelling step] In the swelling step, it is also possible to remove foreign matter from the surface of the raw film 21, remove plasticizers in the raw film 21, impart dyeability, plasticize the raw film 21, and the like.

[0102] The treatment conditions are determined within a range that does not cause changes such as excessive dissolution or devitrification of the raw film 21 . 2, the swelling step is carried out by transporting raw film 21 along a film transport path while continuously unwinding it from roll 22. Furthermore, raw film 21 is immersed in swelling liquid 14 for a predetermined time and then pulled out.

[0103] Pure water can be used as the swelling liquid 14. Alternatively, an aqueous solution of boric acid (as described, for example, in JP-A-10-153709), chloride (as described, for example, in JP-A-06-281816), inorganic acid, inorganic salt, water-soluble organic solvent, alcohol, or the like can also be used as the swelling liquid. The concentration in the aqueous solution can be in the range of 0.01% by mass to 10% by mass.

[0104] The temperature of the swelling liquid 14 is, for example, 10° C. or higher, preferably 20° C. or higher, and 50° C. or lower, preferably 40° C. or lower. The immersion time of the raw film 21 is 10 seconds or more, preferably 20 seconds or more, and 300 seconds or less, preferably 200 seconds or less.

[0105] [Dyeing process] The dyeing step is a step of dyeing the polyvinyl alcohol-based resin film after the swelling step by immersing it in a dye solution. Specifically, in the dyeing step, a dichroic dye is adsorbed and oriented on the polyvinyl alcohol-based resin film after the swelling step.

[0106] 2, in the dyeing step, the film after the swelling step is transported along a film transport path formed by nip roll 71, guide rolls 33 to 36, and nip roll 72. Then, the film is immersed in dyeing solution 15 for a predetermined time and then pulled out.

[0107] In order to enhance the dyeability of the dichroic dye, the film to be subjected to the dyeing step is preferably a film that has been subjected to at least some degree of uniaxial stretching treatment. Alternatively, it is preferable to perform uniaxial stretching treatment during the dyeing treatment instead of or in addition to the uniaxial stretching treatment before the dyeing treatment.

[0108] The dichroic dye may be, for example, iodine. When iodine is used as the dichroic dye, the staining solution 15 may be, for example, an aqueous solution having a mass ratio of iodine / potassium iodide / water=0.003 to 3 / 0.1 to 20 / 100.

[0109] Instead of potassium iodide, other iodides such as zinc iodide may be used, or potassium iodide may be used in combination with other iodides.In addition, compounds other than iodides, such as boric acid, zinc chloride, and cobalt chloride, may also be present.

[0110] When boric acid is added to the dyeing solution 15, it is distinguished from the crosslinking solution described below in that it contains iodine. If an aqueous solution contains 0.003 parts by mass or more of iodine per 100 parts by mass of water, it can be treated as dyeing solution 15. When the dyeing solution contains boric acid, the dyeing solution can be an aqueous solution in which the mass ratio of iodine / potassium iodide / boric acid / water is, for example, 0.003 to 3 / 0.003 to 20 / 0.5 to 2.0 / 100.

[0111] The temperature of the dye solution 15 when the film is immersed is 10° C. or higher, preferably 20° C. or higher, and 50° C. or lower, preferably 40° C. or lower. The immersion time of the film is 10 seconds or more, preferably 30 seconds or more, and 600 seconds or less, preferably 300 seconds or less.

[0112] [Crosslinking process] The crosslinking step is a step in which a crosslinking treatment is carried out by bringing a crosslinking liquid into contact with the polyvinyl alcohol-based resin film after the dyeing treatment. The crosslinking step is a treatment step carried out for the purposes of imparting water resistance through crosslinking or adjusting the hue (complementary color), etc. The crosslinking treatment may be carried out multiple times. When the crosslinking treatment is carried out multiple times, the crosslinking treatment for the purpose of imparting water resistance through crosslinking may be carried out multiple times, or the crosslinking treatment for the purpose of adjusting the hue may be carried out multiple times. However, it is preferable to carry out at least one crosslinking treatment for the purpose of imparting water resistance through crosslinking and at least one crosslinking treatment for the purpose of adjusting the hue, and it is more preferable to carry out the crosslinking step for the purpose of imparting water resistance through crosslinking after the crosslinking step for the purpose of adjusting the hue.

[0113] The crosslinking liquid can be a solution in which a crosslinking agent is dissolved in a solvent, and it is preferable to use an aqueous solution in which a crosslinking agent is dissolved in water. A boron compound is used as the crosslinking agent. A specific example of the boron compound is boric acid.

[0114] In addition to boric acid, the boron compound may contain borax. In addition to boric acid, a compound other than the boron compound may be contained. Examples of the compound other than the boron compound include glyoxal and glutaraldehyde. These compounds may be used alone or in combination of two or more.

[0115] (1st crosslinking step) 2, when the crosslinking step is performed multiple times, the first crosslinking step is performed by transporting the dyed film along a film transport path formed by nip roll 72, guide rolls 37 to 40, and nip roll 73. The film is then immersed in first crosslinking liquid 16a for a predetermined time and then pulled out.

[0116] When the first crosslinking step is a step of performing a crosslinking treatment for the purpose of imparting water resistance through crosslinking, the first crosslinking liquid 16a contains 5 parts by mass or less, preferably 4 parts by mass or less, of boric acid per 100 parts by mass of water. The first crosslinking liquid 16a contains 1 part by mass or more, preferably 1.5 parts by mass or more, of boric acid per 100 parts by mass of water.

[0117] When the dichroic dye used in the dyeing process is iodine, the first crosslinking liquid 16a preferably contains iodide in addition to boric acid. The amount of iodide can be, for example, 1 part by mass to 20 parts by mass per 100 parts by mass of water.

[0118] Examples of iodides include potassium iodide, zinc iodide, etc. Compounds other than iodides, such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, and sodium sulfate, may also be present.

[0119] In the first cross-linking step, the concentrations of boric acid and iodide in the first cross-linking liquid 16a and the temperature of the first cross-linking liquid 16a can be selected appropriately. When the first crosslinking step is a step of performing a crosslinking treatment for the purpose of imparting water resistance through crosslinking, the first crosslinking liquid 16a is preferably an aqueous solution with a mass ratio of boric acid / potassium iodide / water=1-5 / 1-20 / 100.

[0120] The temperature of the first crosslinking liquid 16a when the film is immersed is 40° C. or higher, preferably 50° C. or higher, and 80° C. or lower, preferably 70° C. or lower. The immersion time of the film is 10 seconds or more, preferably 20 seconds or more, more preferably 30 seconds or more, and 600 seconds or less, preferably 300 seconds or less, more preferably 150 seconds or less.

[0121] (Second crosslinking step) 2, in the second crosslinking step, the film after the first crosslinking step is transported along a film transport path formed by nip roll 73, guide rolls 41 to 44, and nip roll 74. Then, the film is immersed in second crosslinking liquid 16b for a predetermined time and then pulled out.

[0122] The second cross-linking liquid 16b contains, for example, 10 parts by mass or less, and preferably 8 parts by mass or less, of boric acid per 100 parts by mass of water. The second cross-linking liquid 16b contains 1 part by mass or more, and preferably 1.5 parts by mass or more, of boric acid per 100 parts by mass of water.

[0123] The second cross-linking liquid 16b may contain an iodide, such as potassium iodide, which may be the same as the iodides exemplified for the first cross-linking liquid 16a. In the second cross-linking step, the concentrations of boric acid and iodide in the second cross-linking liquid 16b and the temperature of the second cross-linking liquid 16b can be selected appropriately.

[0124] The temperature of the second cross-linking liquid 16b when the film is immersed is 20° C. or higher, preferably 30° C. or higher, and 60° C. or lower, preferably 50° C. or lower. The temperature of the second cross-linking liquid 16b when the film is immersed is preferably lower than the temperature of the first cross-linking liquid 16a, from the viewpoint of increasing the neck-in of the film and consequently improving the degree of polarization.

[0125] The immersion time of the film is 1 second or more, and from the viewpoint of adjusting the degree of crosslinking of the polarizer 101 within the above range, is 30 seconds or less, and preferably 20 seconds or less. When the second crosslinking step is a step of performing a crosslinking treatment for the purpose of adjusting the hue, the content of boric acid in the second crosslinking liquid 16b is, for example, 1 part by mass to 20 parts by mass, preferably 1 part by mass to 10 parts by mass, and more preferably 1 part by mass to 5 parts by mass, per 100 parts by mass of water. If the content of boric acid in the second crosslinking liquid 16b is higher than the content of boric acid in the first crosslinking liquid 16a, the durability of the resulting polarizer becomes good, which is preferable.

[0126] When the second crosslinking step is a step of performing a crosslinking treatment for the purpose of adjusting the hue, the content of potassium iodide in the second crosslinking liquid 16b is, for example, 1 part by mass or more and 20 parts by mass or less per 100 parts by mass of water, preferably 1 part by mass or more and 10 parts by mass or less, and more preferably 1 part by mass or more and 5 parts by mass or less.

[0127] [Cleaning process] The washing step is a step of bringing the polyvinyl alcohol-based resin film after the crosslinking step into contact with a washing liquid to perform a washing treatment, for the purpose of removing excess chemicals such as boric acid and iodine adhering to the polyvinyl alcohol-based resin film.

[0128] 2, in the cleaning step, the polyvinyl alcohol-based resin film after the crosslinking step is transported along a film transport path formed by nip roll 74, guide rolls 45 to 48, and nip roll 75. Then, the film is immersed in cleaning liquid 17 for a predetermined time and then pulled out.

[0129] The cleaning liquid 17 used in the cleaning step can be a medium containing water as a main component, such as water, distilled water, pure water, etc. Furthermore, from the viewpoint of controlling the potassium content in the polarizer, the cleaning liquid may contain potassium iodide, and in this case, the concentration of potassium iodide in the cleaning liquid is preferably about 1 to 10 mass %, more preferably about 1.5 to 4 mass %, and even more preferably about 1.8 to 3.8 mass %.

[0130] The cleaning step can be performed by spraying the cleaning liquid onto the film as a shower instead of immersing the film in the cleaning liquid 17, or by combining immersion in the cleaning liquid 17 with spraying the cleaning liquid.

[0131] The temperature of the cleaning solution 17 in the cleaning treatment is preferably 2° C. or more and 50° C. or less, and the immersion time of the film is preferably 1 second or more and 120 seconds or less. In the example shown in FIG. 2, the film drawn out from the cleaning liquid 17 passes through a guide roll 48 and a nip roll 75 in this order and is introduced into a drying oven 18 .

[0132] [Drying process] After the crosslinking step or the washing step, it is preferable to carry out a treatment for drying the polyvinyl alcohol-based resin film.

[0133] The method for drying the film is not particularly limited, but it is preferable to use a drying oven 18 as shown in Figure 2. The drying oven 18 may be, for example, one equipped with a hot air dryer.

[0134] The drying temperature is, for example, 30° C. or higher, preferably 50° C. or higher, more preferably 60° C. or higher, and even more preferably 70° C. or higher, and 100° C. or lower, preferably 90° C. or lower, and more preferably 80° C. or lower.

[0135] The drying time is, for example, 30 seconds or more, preferably 50 seconds or more, and more preferably 80 seconds or more, and 600 seconds or less, preferably 300 seconds or less, and more preferably 200 seconds or less. The treatment of drying the polyvinyl alcohol-based resin film can also be performed using a far-infrared heater.

[0136] The obtained polarizer 101 may be wound up around a winding roll to form a roll, or may be directly subjected to a step for producing a polarizing plate, i.e., a step for laminating a protective film or the like on one or both surfaces of the polarizer 101, without being wound up.

[0137] <Polarizing Plate Manufacturing Method> The method for manufacturing a polarizing plate includes, for example, a polarizer manufacturing step for manufacturing a polarizer according to the above-described manufacturing method.

[0138] The method for producing a polarizing plate includes a protective film laminating step. The protective film bonding step is a step of bonding a protective film to at least one surface of a polarizer via an adhesive layer formed from the above-described adhesive composition or a pressure-sensitive adhesive layer formed from the above-described pressure-sensitive adhesive composition.

[0139] When the polarizer production process does not involve immersing the PVA resin film in a solution containing a urea compound, an adhesive composition containing a urea compound may be used in the protective film laminating process. That is, when a polarizer not containing a urea compound is used, a protective film may be laminated to the polarizer via an adhesive layer formed from an adhesive composition containing a urea compound.

[0140] The protective film laminating step can be performed using, for example, a roll laminating machine. The polarizing plate may be manufactured by preparing long members, laminating the respective members together using a roll-to-roll process, and then cutting them into a predetermined shape, or by cutting the respective members into a predetermined shape and then laminating them together.

[0141] <Effects of this embodiment> A polarizing plate including a polarizer containing a urea compound and a radical scavenger can suppress the polyenization of polyvinyl alcohol even in a high-temperature environment.

[0142] When an adhesive layer laminated on a polarizer in a polarizing plate contains a urea compound, part of the urea compound contained in the adhesive layer may migrate to the polarizer. Therefore, even with a polarizing plate in which the polarizer contains a radical scavenger and at least one of the polarizer and the adhesive layer contains a urea compound, polyenization of polyvinyl alcohol can be suppressed in a high-temperature environment.

[0143] By using a polarizer containing a urea compound and a radical scavenger, a polarizing plate can be produced that can suppress polyenization in a high-temperature environment. When a polarizer containing a radical scavenger but not a urea compound is used, a polarizing plate capable of suppressing polyenization in a high-temperature environment can be produced by laminating a protective film to the polarizer via an adhesive composition containing a urea compound.

[0144] A polarizing plate having excellent high-temperature durability can be suitably used in an image display device that may be exposed to a high-temperature environment for a long period of time. For example, an image display device for vehicle use, such as a car navigation device or a rear monitor, may be exposed to a high-temperature environment for a long period of time. The polarizing plate of this embodiment can also be suitably used in an image display device for vehicle use.

[0145] In this embodiment, "high temperature environment" means an environment of 100°C or higher, for example, 105°C. Furthermore, "long period of time" means 100 hours or longer, for example, 500 hours. [Example]

[0146] The polarizing plate, the manufacturing method of a polarizer, and the manufacturing method of a polarizing plate will be described in more detail based on the following examples. Note that the polarizing plate, the manufacturing method of a polarizer, and the manufacturing method of a polarizing plate are not limited to the configurations described in the examples.

[0147] (Production Example 1: Preparation of polarizer) <Preparation of Polarizer 1> A 30 μm-thick polyvinyl alcohol resin film was immersed in pure water at 21.5°C for 79 seconds (swelling step), then immersed in an aqueous solution at 23°C containing 1.0 mM iodine and having a potassium iodide / boric acid / water mass ratio of 2 / 2 / 100 for 151 seconds (dyeing step). It was then immersed in an aqueous solution at 68.5°C containing a potassium iodide / boric acid / water mass ratio of 2.5 / 4 / 100 for 76 seconds (first crosslinking step). It was then immersed in an aqueous solution at 45°C containing a potassium iodide / boric acid / zinc chloride / water mass ratio of 3 / 5.5 / 0.6 / 100 for 11 seconds (second crosslinking step, metal ion treatment step). The film was then immersed in a 45°C cleaning solution (potassium iodide concentration: 2.0% by mass, 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl free radical (hereinafter also referred to as TEMPOL; TEMPOL is represented by the formula below) concentration: 0.4% by mass, and urea concentration: 0.4% by mass) for 10 seconds to wash (cleaning step), and then dried at 38°C (drying step) to obtain a 12 μm-thick polarizer in which iodine was adsorbed and aligned in polyvinyl alcohol. Stretching was mainly performed in the dyeing step and the first crosslinking step, and the total stretching ratio was 5.85 times. The thickness of the obtained polarizer was measured using a Nikon digital micrometer "MH-15M."

[0148] [ka]

[0149] <Fabrication of Polarizer 2> A 30 μm-thick polyvinyl alcohol resin film was immersed in pure water at 21.5°C for 79 seconds (swelling step), then immersed in an aqueous solution at 23°C containing 1.0 mM iodine and having a potassium iodide / boric acid / water mass ratio of 2 / 2 / 100 for 151 seconds (dyeing step). It was then immersed in an aqueous solution at 68.5°C containing a potassium iodide / boric acid / water mass ratio of 2.5 / 4 / 100 for 76 seconds (first crosslinking step). It was then immersed in an aqueous solution at 45°C containing a potassium iodide / boric acid / zinc chloride / water mass ratio of 3 / 5.5 / 0.6 / 100 for 11 seconds (second crosslinking step, metal ion treatment step). The film was then immersed in a 45°C cleaning solution (potassium iodide concentration 2.0% by mass, TEMPOL concentration 0.4% by mass) for 10 seconds to be washed (washing step), and then dried at 38°C (drying step) to obtain a 12µm-thick polarizer in which iodine was adsorbed and oriented in the polyvinyl alcohol. Stretching was mainly performed in the dyeing step and the first crosslinking step, and the total stretching ratio was 5.85 times.

[0150] <Fabrication of Polarizer 3> A 40 μm-thick polyvinyl alcohol resin film was immersed in pure water at 21.5°C for 79 seconds (swelling step), then immersed in an aqueous solution at 23°C containing 1.0 mM iodine and having a potassium iodide / boric acid / water mass ratio of 2 / 2 / 100 for 151 seconds (dyeing step). It was then immersed in an aqueous solution at 68.5°C containing a potassium iodide / boric acid / water mass ratio of 2.5 / 4 / 100 for 76 seconds (first crosslinking step). It was then immersed in an aqueous solution at 45°C containing a potassium iodide / boric acid / zinc chloride / water mass ratio of 3 / 5.5 / 0.6 / 100 for 11 seconds (second crosslinking step, metal ion treatment step). The film was then immersed in a 45°C cleaning solution (potassium iodide concentration 2.0% by mass, TEMPOL concentration 0.4% by mass) for 10 seconds to be washed (washing step), and then dried at 38°C (drying step) to obtain a 16µm thick polarizer in which iodine was adsorbed and oriented in the polyvinyl alcohol. Stretching was mainly performed in the dyeing step and the first crosslinking step, and the total stretching ratio was 5.85 times.

[0151] <Fabrication of Polarizer 4> A 30 μm-thick polyvinyl alcohol resin film was immersed in pure water at 21.5°C for 79 seconds (swelling step), then immersed in an aqueous solution at 23°C containing 1.0 mM iodine and having a potassium iodide / boric acid / water mass ratio of 2 / 2 / 100 for 151 seconds (dyeing step). It was then immersed in an aqueous solution at 68.5°C containing a potassium iodide / boric acid / water mass ratio of 2.5 / 4 / 100 for 76 seconds (first crosslinking step). It was then immersed in an aqueous solution at 45°C containing a potassium iodide / boric acid / zinc chloride / water mass ratio of 3 / 5.5 / 0.6 / 100 for 11 seconds (second crosslinking step, metal ion treatment step). The film was then washed by immersion in a 45°C cleaning solution (potassium iodide concentration: 2.0% by mass) for 10 seconds (washing step), and then dried at 38°C (drying step) to obtain a 12µm-thick polarizer in which iodine was adsorbed and oriented in the polyvinyl alcohol. Stretching was mainly performed in the dyeing step and the first crosslinking step, and the total stretching ratio was 5.85 times.

[0152] (Production Example 2: Preparation of adhesive composition) 50 g of modified polyvinyl alcohol resin with acetoacetyl groups (Gohsenex Z-410, manufactured by Mitsubishi Chemical Corporation) was dissolved in 950 g of pure water, heated at 90°C for 2 hours, and then cooled to room temperature to obtain an acetoacetyl group-modified polyvinyl alcohol resin solution (PVA solution).

[0153] Adhesive compositions 1, 2, and 3 were prepared by blending a PVA solution, urea, a commercially available 40% by mass glyoxal solution, maleic acid, TEMPOL, and pure water so that the contents of PVA, glyoxal, TEMPOL, urea, and maleic acid were as shown in Table 1. In the table, "-" indicates that the corresponding component was not contained.

[0154] [Table 1]

[0155] (Production Example 3: Preparation of polarizing plate) <Preparing the protective film> The following protective films were prepared: The moisture permeability of the protective films was measured at a temperature of 40°C and a relative humidity of 90% in accordance with the moisture permeability test (cup method) of JIS Z0208. Protective film F1: saponified triacetyl cellulose film with a hard coat layer (manufactured by Toppan Printing Co., Ltd., product name "40FJCHCN-LMP", triacetyl cellulose film thickness: 40 μm, hard coat layer thickness: 7 μm). Moisture permeability is 200 g / (m 2 -24 hours). Protective film F2: Saponified commercially available cellulose acylate film: Fujitac ZRD40 (manufactured by Fujifilm Corporation: thickness 40 μm). Moisture permeability is 850 g / (m 2 -24 hours).

[0156] <Example 1: Preparation of polarizing plate 1> A protective film F1 was laminated onto one surface of the polarizer 1 produced in Production Example 1 via the adhesive composition 1 prepared in Production Example 2, with the surface without the hard coat layer facing the polarizer. A protective film F2 was laminated onto the other surface of the polarizer via the adhesive composition 1 prepared in Production Example 2, and the resulting film was laminated using a roll laminator. This was then dried at 75°C for 8 minutes to obtain a polarizing plate 1. The adhesive layers formed from the adhesive compositions each had a thickness of 80 nm after drying. The configuration of polarizing plate 1 is shown in Table 2.

[0157] <Example 2: Preparation of polarizing plate 2> A protective film F1 was laminated onto one surface of the polarizer 2 produced in Production Example 1 via the adhesive composition 2 prepared in Production Example 2, with the surface without the hard coat layer facing the polarizer. A protective film F2 was laminated onto the other surface of the polarizer via the adhesive composition 2 prepared in Production Example 2, and the resulting laminate was attached using a roll laminator. This was then dried at 75°C for 8 minutes to obtain polarizing plate 2. The adhesive layers formed from the adhesive compositions each had a thickness of 80 nm after drying. The configuration of polarizing plate 2 is shown in Table 2.

[0158] <Example 3: Preparation of polarizing plate 3> Polarizing plate 3 was produced in the same manner as in Example 2, except that polarizer 2 was replaced with polarizer 3. Table 2 shows the configuration of polarizing plate 3.

[0159] <Comparative Example 1: Preparation of Polarizing Plate 4> A protective film F1 was laminated to one surface of the polarizer 4 produced in Production Example 1 via the adhesive composition 3 prepared in Production Example 2, with the surface without the hard coat layer facing the polarizer. A protective film F2 was laminated to the other surface of the polarizer via the adhesive composition 3 prepared in Production Example 2, and the resulting laminate was attached using a roll laminator. This was then dried at 75°C for 8 minutes to obtain polarizing plate 4. The adhesive layers formed from the adhesive compositions each had a thickness of 80 nm after drying. The configuration of polarizing plate 4 is shown in Table 2.

[0160] <Comparative Example 2: Preparation of Polarizing Plate 5> Polarizing plate 5 was produced in the same manner as in Example 2 above, except that adhesive composition 2 was replaced with adhesive composition 1. Table 2 shows the configuration of polarizing plate 5.

[0161] (Production Example 4: Preparation of laminate) <Preparation of Laminate 1> A 25 μm thick acrylic pressure-sensitive adhesive layer was formed on the protective film F2 side of polarizing plate 1, thereby obtaining pressure-sensitive adhesive layer-attached polarizing plate 1. The obtained pressure-sensitive adhesive layer-attached polarizing plate 1 was cut into a size of 90 mm × 100 mm so that its absorption axis was parallel to the long side. A 100 mm × 100 mm non-alkali glass plate ("EAGLE XG" manufactured by Corning) was attached to the pressure-sensitive adhesive layer surface of pressure-sensitive adhesive layer-attached polarizing plate 1, thereby obtaining glass plate-attached polarizing plate 1.

[0162] A 100 mm x 100 mm alkali-free glass sheet (manufactured by Corning Incorporated, "EAGLE XG") was attached to the protective film F1 side of the obtained polarizing plate 1 with a glass plate via a 250 μm thick adhesive layer (manufactured by 3M, product name "CEF2810"), and the sheet was then heated at a temperature of 50°C and a pressure of 5 kgf / cm. 2 (490.3 kPa) for 15 minutes to prepare a laminate 1.

[0163] <Preparation of Laminates 2 to 5> Laminates 2 to 5 were prepared in the same manner as for the laminate 1, except that polarizing plate 1 was changed to polarizing plates 2 to 5, respectively.

[0164] (High temperature durability evaluation) <Measurement of initial optical properties> The five evaluation samples of laminates 1 to 5 obtained above were left to stand for 1 hour in an environment of 23°C and a relative humidity of 55%. After standing, the initial luminous efficiency-corrected single transmittance was measured using a spectrophotometer / colorimeter (Konica Minolta, Inc., "CM-3700A").

[0165] <High temperature durability test> After measuring the initial luminous efficacy-corrected single transmittance, five types of evaluation samples of Laminates 1 to 5 were left standing for 500 hours in an environment at a temperature of 105° C. After being left standing, the luminous efficacy-corrected single transmittance of each evaluation sample was measured.

[0166] Based on the above measurement results, the change in luminous efficacy-corrected single transmittance was calculated as the absolute value of the difference between the luminous efficacy-corrected single transmittance after the high-temperature durability test and the initial luminous efficacy-corrected single transmittance for Laminates 1 to 5. Based on these results, the effect of inhibiting polyenization was evaluated on a three-point scale according to the following criteria. The smaller the change in luminous efficacy-corrected single transmittance, the more effectively polyenization of polyvinyl alcohol was inhibited.

[0167] A (Excellent): The absolute value of the difference is less than 3% B (Good): The absolute value of the difference is 3% or more and less than 5% C (Fail): The absolute value of the difference is 5% or more

[0168] [Table 2] [Explanation of symbols]

[0169] 100...Polarizing plate 101...Polarizer 102...Laminating layer 103...First protective film 104...Second protective film

Claims

1. A polarizing plate comprising: a polarizer in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film; and a protective film laminated on at least one surface of the polarizer via an adhesive layer, the adhesive layer contains a urea compound, the polarizer contains a radical scavenger, the urea compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives; The polarizing plate, wherein the radical scavenger is a hindered amine compound.

2. A polarizing plate comprising: a polarizer in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film; and a protective film laminated on at least one surface of the polarizer, the polarizer contains a urea compound and a radical scavenger, the urea compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives; The polarizing plate, wherein the radical scavenger is a hindered amine compound.

3. The hindered amine compound is a compound represented by formula (1): The polarizing plate according to claim 1 or 2. 【Chemistry 1】 [In formula (1), R １ represents an oxy radical group, a hydrogen atom, a hydroxy group, an alkyl group having 1 to 30 carbon atoms which may have a hydroxy group, or an alkoxy group having 1 to 30 carbon atoms which may have a hydroxy group. R ２ , R ３ , R ４ and R ５ each independently represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. n represents 0 or 1. X represents any organic group.

4. R １ is an oxy radical group The polarizing plate according to claim 3 .

5. A method for producing a polarizer from a polyvinyl alcohol-based resin film, comprising: a step of immersing the polyvinyl alcohol-based resin film in a solution containing a urea compound and a radical scavenger, the urea compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives; The radical scavenger is a hindered amine compound. A method for manufacturing a polarizer.

6. A method for manufacturing a polarizing plate including a polarizer and a protective film, a polarizer production step of producing the polarizer from the polyvinyl alcohol-based resin film, the step including a step of immersing the polyvinyl alcohol-based resin film in a solution containing a radical scavenger; a protective film bonding step of bonding the protective film to at least one surface of the polarizer via an adhesive layer formed from an adhesive composition containing a urea compound, the urea compound is at least one selected from the group consisting of urea, urea derivatives, thiourea, and thiourea derivatives; The radical scavenger is a hindered amine compound. A method for manufacturing a polarizing plate.

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