Polarizing film

Abstract

To provide a polarization film that includes a polarizing film with high-content iodine, and has initial simple transmissivity of 41% or less, is excellent in inhibition effect for reduction in simple transmissivity of a polarizing film due to colouring under high temperature environment, and further excellent in inhibition effect (humidification durability) for reduction in degree of polarization under high temperature and high humidity environment.SOLUTION: A polarization film is obtained by bonding a transparent protective film or an optical functional film on at least one surface of the polarizing film. The polarization film is a first film in which iodine is absorbed and arrayed on a polyvinyl alcohol film, iodine concentration is more than 10 weight%, and the transparent protective film and the optical functional film has moisture vapor permeability of 200 g / (m2 24h) or less. The polarization film has single transmissivity of 41% or less, and satisfies the condition that an amount of change (ΔTs) of the single transmissivity represented by a general formula (1):ΔTs(%)=Ts96-Ts0 is 0% or more and 5% or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polarizing film. [Background technology]

[0002] Conventionally, dyed polyvinyl alcohol films (containing dichroic substances such as iodine or dichroic dyes) have been used as polarizing films for various image display devices, such as liquid crystal display devices and organic electroluminescence (EL) display devices, because they combine high transmittance and high polarization. The polarizing films are produced by subjecting polyvinyl alcohol films to various treatments, such as swelling, dyeing, crosslinking, and stretching, in a bath, followed by washing and drying. Furthermore, the polarizing films are typically used as polarizing films (polarizing plates) with protective films, such as triacetyl cellulose, attached to one or both sides of the film using an adhesive.

[0003] On the other hand, as polarizing films become thinner, polarizing films with a higher iodine content are required (Patent Document 1).Furthermore, even for such thin polarizing films, some are known that can suppress the amount of change in single-unit transmittance under high-temperature conditions (105°C x 30 hours) (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 186244 [Patent Document 2] International Publication No. 2019 / 103002 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the thin polarizing films specifically disclosed in Patent Documents 1 and 2 do not sufficiently suppress the decrease in single-unit transmittance in a high-temperature environment, and there is room for improvement in this performance.

[0006] Meanwhile, the present inventors have found that iodine contained in iodine-based polarizing films promotes polyenation under high-temperature conditions. Therefore, reducing the iodine content in the polarizing film is effective in suppressing a decrease in the single-unit transmittance due to coloration of the polarizing film under high-temperature conditions. However, it has been difficult to obtain a polarizing film with a high iodine content that has a good polarization degree.

[0007] Furthermore, as described in Patent Document 2, in polarizing films with a high iodine content, a polarizing film with a single transmittance of 41% or less is desired, from the viewpoint that contrast can be increased by setting the single transmittance low.

[0008] Furthermore, polarizing films have the problem that, in a high-temperature and high-humidity environment, the boric acid crosslinks in the polarizing film are released and the iodine complex is broken, resulting in a decrease in polarization degree.

[0009] In view of the above circumstances, an object of the present invention is to provide a polarizing film having a high iodine content, which has an initial single-piece transmittance of 41% or less, is excellent in suppressing a decrease in the single-piece transmittance due to coloration of the polarizing film in a high-temperature environment, and is also excellent in suppressing a decrease in the degree of polarization in a high-temperature, high-humidity environment (humidification durability). [Means for solving the problem]

[0010] That is, the present invention provides a polarizing film having a transparent protective film or an optically functional film laminated to at least one surface of the polarizing film, the polarizing film being formed by adsorbing and orienting iodine on a polyvinyl alcohol-based film, and the iodine concentration is greater than 10% by weight, and the transparent protective film or the optically functional film has a moisture permeability of 200 g / (m 2 24h), and the polarizing film has a single transmittance of 41% or less and is expressed by the general formula (1): ΔTs(%)=Ts 96 -Ts0 (in the general formula (1), Ts0 is the single transmittance of a laminate in which a glass plate is bonded to the surface of the polarizing film opposite to the first film surface via a pressure-sensitive adhesive layer, and Ts96 represents the single-piece transmittance after the laminate is heat-treated at 105°C for 96 hours. The polarizing film satisfies the condition that the change in single-piece transmittance (ΔTs) represented by (ΔTs) is 0% or more and 5% or less. [Effects of the Invention]

[0011] Although the details of the mechanism of action of the polarizing film of the present invention are unclear, it is presumed as follows: However, the present invention should not be construed as being limited to this mechanism of action.

[0012] The polarizing film of the present invention is a polarizing film having a transparent protective film or an optically functional film laminated to at least one surface of the polarizing film, the polarizing film being formed by adsorbing and orienting iodine on a polyvinyl alcohol-based film, and having an iodine concentration of more than 10% by weight, and the transparent protective film or the optically functional film having a moisture permeability of 200 g / (m 2 24h), and the polarizing film has a single transmittance of 41% or less and is expressed by the general formula (1): ΔTs(%)=Ts 96 -Ts0 (in the general formula (1), Ts0 is the single transmittance of a laminate in which a glass plate is bonded to the surface of the polarizing film opposite to the first film surface via a pressure-sensitive adhesive layer, and Ts 96represents the single-layer transmittance after the laminate is heat-treated at 105°C for 96 hours. The change in single-layer transmittance (ΔTs) expressed by ( ) satisfies the condition that it is 0% or more and 5% or less. The polarizing film of the present invention exhibits a small change in single-layer transmittance (ΔTs) after the heat treatment (in a high-temperature environment), thereby suppressing a decrease in single-layer transmittance due to coloration of the polarizing film. The reason for the small change in single-layer transmittance (ΔTs) before and after the heat treatment is presumably because the temperature at which the dehydration reaction due to polyenation occurs in the polarizing film of the present invention is higher than that of conventional polarizing films. In particular, the heat treatment is a heat durability test used as an indicator of the heat resistance of displays, and is more severe than the heat durability tests described in Patent Documents 1 and 2. Furthermore, by setting the iodine concentration in the polarizing film within a certain range, the polarizing film of the present invention exhibits a good initial polarization degree while controlling the temperature at which the dehydration reaction due to polyenation occurs to a higher temperature.

[0013] In addition, in the polarizing film of the present invention, the transparent protective film or the optically functional film has a moisture permeability of 200 g / (m 2 24h or less), preventing water from entering the polarizing film and providing excellent resistance to deterioration of polarization even in high-temperature, high-humidity environments (humidity durability). DETAILED DESCRIPTION OF THE INVENTION

[0014] <Polarizing film> The polarizing film of the present invention is an iodine-based polarizing film formed by adsorbing and aligning iodine on a polyvinyl alcohol-based film, and has an iodine content of more than 10% by weight.

[0015] The polarizing film has an iodine content of more than 10% by weight from the viewpoint of improving the initial polarization degree of the polarizing film. The polarizing film has an iodine content of preferably 12% by weight or more, more preferably 15% by weight or more, from the viewpoint of controlling the initial polarization degree to 99.98% or more, and the polarizing film has an iodine content of preferably 30% by weight or less, more preferably 25% by weight or less, from the viewpoint of increasing the temperature at which a dehydration reaction due to polyenization occurs.

[0016] From the viewpoint of controlling the initial polarization degree to 99.98 or more, the thickness of the polarizing film is preferably 0.2 μm or more, and more preferably 0.5 μm or more. From the viewpoint of reducing the thickness of the polarizing film, the thickness is preferably 10 μm or less, more preferably 8 μm or less, and even more preferably 5 μm or less.

[0017] The polarizing film preferably contains a radical scavenger. It is believed that the radical scavenger captures radicals generated by heating the polyvinyl alcohol of the polarizing film, thereby enabling the temperature at which the dehydration reaction of polyenization occurs to be set to a higher temperature. Examples of the radical scavenger include hindered phenol-based, hindered amine-based, phosphorus-based, sulfur-based, benzotriazole-based, benzophenone-based, hydroxylamine-based, salicylic acid ester-based, and triazine-based compounds. From the viewpoint of easily enabling the temperature at which the dehydration reaction of polyenization occurs to be set to a higher temperature, the radical scavenger is preferably, for example, a compound having a nitroxy radical or a nitroxide group.

[0018] As the nitroxy radical or the compound having a nitroxide group, an N-oxyl compound (having a functional group of CN(-C)-O) is preferred from the viewpoint of having a radical that is relatively stable in air at room temperature. · Compounds having the formula (O · represents an oxy radical), and known compounds can be used. Examples of N-oxyl compounds include compounds having an organic group with the following structure: [ka] (In general formula (1), R 1 represents an oxy radical, and R 2 From R 5 are independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and n is 0 or 1.) In addition, in general formula (1), the left side of the dotted line represents any organic group.

[0019] Examples of the compound having the organic group include compounds represented by the following general formulas (2) to (5). [ka] (In general formula (2), R 1 ~R 5 , and n are the same as above, and R 6 represents a hydrogen atom, or an alkyl group, acyl group, or aryl group having 1 to 10 carbon atoms, and n represents 0 or 1. [ka] (In general formula (3), R 1 From R 5 , and n are the same as above, and R 7 and R 8 each independently represents a hydrogen atom, or an alkyl group, acyl group, or aryl group having 1 to 10 carbon atoms. [ka] (In general formula (4), R 1 From R 5 , and n are the same as above, and R 9 From R 11 are independently a hydrogen atom, or an alkyl group having 1 to 10 carbon atoms, an acyl group, an amino group, an alkoxy group, a hydroxy group, or an aryl group. [ka] (In general formula (5), R 1 From R 5 , and n are the same as above, and R 12 represents a hydrogen atom, or an alkyl group having 1 to 10 carbon atoms, an amino group, an alkoxy group, a hydroxy group, or an aryl group.

[0020] In the general formulas (1) to (5), R 2 From R 5From the viewpoint of availability, R is preferably an alkyl group having 1 to 6 carbon atoms, and more preferably an alkyl group having 1 to 3 carbon atoms. 6 is preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and more preferably a hydrogen atom. 7 and R 8 are preferably independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and more preferably a hydrogen atom. 9 From R 11 is preferably a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. 12 is preferably a hydroxy group, an amino group, or an alkoxy group. In the general formulae (1) to (5), n is preferably 1 from the viewpoint of availability.

[0021] Examples of the N-oxyl compound include the N-oxyl compounds described in JP-A Nos. 2003-64022, 11-222462, 2002-284737, and WO 2016 / 047655.

[0022] Furthermore, from the viewpoint of being able to efficiently capture radicals generated in the polyenation reaction, the radical scavenger preferably has a molecular weight of 1,000 or less, more preferably 500 or less, and even more preferably 300 or less.

[0023] The radical scavenger is preferably soluble in an amount of 1 part by weight or more in 100 parts by weight of water at 25°C, more preferably soluble in an amount of 2 parts by weight or more in 100 parts by weight of water at 25°C, and even more preferably soluble in an amount of 5 parts by weight or more in 100 parts by weight of water at 25°C, from the viewpoints of being able to efficiently penetrate into the polarizing film together with water during production of the polarizing film, being able to be impregnated into the polarizing film at a high concentration, and being able to be impregnated into even a thick polyvinyl alcohol-based film in a short time, thereby increasing the productivity of the polarizing film.

[0024] Examples of the compound having a nitroxy radical or a nitroxide group include the following compounds: [ka] (In general formula (6), R represents a hydrogen atom, or an alkyl group, acyl group, or aryl group having 1 to 10 carbon atoms.) [ka] [ka]

[0025] When the polarizing film contains the radical scavenger, the content of the radical scavenger in the polarizing film is preferably 0.1% by weight or more, more preferably 0.2% by weight or more, and even more preferably 0.5% by weight or more, from the viewpoint of suppressing a decrease in the single-unit transmittance due to coloration of the polarizing film in a high-temperature environment, and from the viewpoint of appearance, the content is preferably 30% by weight or less, more preferably 20% by weight or less, and even more preferably 10% by weight or less.

[0026] Furthermore, when the polarizing film contains the radical scavenger, the weight ratio of the content of the radical scavenger to the content of the iodine (weight ratio of radical scavenger content / iodine content) of the polarizing film is preferably 0.01 or more, and more preferably 0.05 or more, from the viewpoint of suppressing a decrease in the single-unit transmittance due to coloration of the polarizing film in a high-temperature environment, and is preferably 1.0 or less, and more preferably 0.5 or less, from the viewpoint of appearance.

[0027] <Method of manufacturing polarizing film> The polarizing film is produced by subjecting a polyvinyl alcohol film (PVA film) to any of the following steps: swelling, washing, and drying, and at least dyeing, crosslinking, and stretching. The iodine content in the polarizing film can be controlled by the concentration of iodine and iodides such as potassium iodide contained in any of the treatment baths in the swelling, dyeing, crosslinking, stretching, and washing steps, as well as the treatment temperature and treatment time in each of the treatment baths. The steps may be performed in any appropriate order, and one step may be performed multiple times as necessary.

[0028] The polyvinyl alcohol-based film is transparent in the visible light region and can be used without any particular limitation as long as it disperses and adsorbs dichroic substances such as iodine and dichroic dyes. Examples of materials for the polyvinyl alcohol-based film include polyvinyl alcohol and its derivatives. Examples of polyvinyl alcohol derivatives include polyvinyl formal, polyvinyl acetal; olefins such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, and their alkyl esters, modified with acrylamide, etc. The polyvinyl alcohol preferably has an average degree of polymerization of approximately 100 to 10,000, more preferably approximately 1,000 to 10,000, and even more preferably approximately 1,500 to 4,500. The polyvinyl alcohol preferably has a saponification degree of approximately 80 to 100 mol%, more preferably approximately 95 mol% to 99.95 mol%. The average degree of polymerization and the saponification degree can be determined in accordance with JIS K 6726.

[0029] The polyvinyl alcohol film may contain additives such as plasticizers and surfactants. Examples of the plasticizer include polyols such as glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol, and condensates thereof. The amount of the additives used is not particularly limited, but is preferably about 20% by weight or less of the polyvinyl alcohol film.

[0030] The polyvinyl alcohol-based film may be a laminate in which a polyvinyl alcohol-based resin layer (PVA-based resin layer) containing a polyvinyl alcohol-based resin (PVA-based resin) is formed on one side of a long thermoplastic resin substrate. Any appropriate method may be used to prepare the laminate, and an example of such a method includes applying a coating liquid containing the PVA-based resin to the surface of the thermoplastic resin substrate and drying it. The thickness of the thermoplastic resin substrate is preferably about 20 to 300 μm, more preferably about 50 to 200 μm. The thickness of the PVA-based resin layer is preferably about 3 to 40 μm, more preferably about 3 to 20 μm.

[0031] Any suitable thermoplastic resin can be used as the constituent material of the thermoplastic resin substrate. Examples of the thermoplastic resin include ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, and copolymer resins thereof. Among these, norbornene resins and amorphous polyethylene terephthalate resins are preferred. Furthermore, amorphous polyethylene terephthalate resins are preferred because the thermoplastic resin substrate has excellent stretchability and crystallization during stretching can be suppressed. Examples of amorphous polyethylene terephthalate resins include copolymers containing isophthalic acid and / or cyclohexanedicarboxylic acid as dicarboxylic acids, and copolymers containing cyclohexanedimethanol or diethylene glycol as glycols.

[0032] The thermoplastic resin substrate may be subjected to a surface treatment (e.g., corona treatment) before forming the PVA-based resin layer, or an easy-adhesion layer may be formed on the thermoplastic resin substrate. By performing such treatment, the adhesion between the thermoplastic resin substrate and the PVA-based resin layer can be improved. Furthermore, the thermoplastic resin substrate may be stretched before forming the PVA-based resin layer.

[0033] The coating liquid is a solution in which a PVA resin is dissolved in a solvent. Examples of the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine, with water being preferred. These can be used alone or in combination. The concentration of the PVA resin in the coating liquid is preferably about 3 to 20 parts by weight per 100 parts by weight of the solvent, from the viewpoint of forming a uniform coating film that adheres closely to the thermoplastic resin substrate.

[0034] The coating solution may contain a halide to improve the orientation of polyvinyl alcohol molecules during stretching. Any appropriate halide may be used as the halide, and examples thereof include iodide and sodium chloride. Examples of the iodide include potassium iodide, sodium iodide, and lithium iodide, with potassium iodide being preferred. The concentration of the halide in the coating solution is preferably about 5 to 20 parts by weight, more preferably about 10 to 15 parts by weight, per 100 parts by weight of the PVA resin.

[0035] The coating liquid may contain additives, such as plasticizers such as ethylene glycol and glycerin, and surfactants such as nonionic surfactants.

[0036] Any appropriate method can be used as the method for applying the coating liquid, and examples thereof include roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, and knife coating (such as comma coating).

[0037] In the stretching step, the PVA-based film is typically uniaxially stretched about 3 to 7 times. The stretching direction may be the longitudinal direction (MD) of the film or the width direction (TD) of the film. The stretching direction is preferably the TD direction from the viewpoint of roll-to-roll lamination with a transparent protective film or an optically functional film. The stretching method may be dry stretching, wet stretching, or a combination of these. The PVA-based film may also be stretched during a crosslinking step, a swelling step, a dyeing step, or the like. The stretching step may be performed in one step or multiple steps. When performed in multiple steps, the stretching ratio is the product of the stretching ratios in each step. The stretching direction may correspond to the absorption axis direction of the resulting polarizing film.

[0038] The swelling step is carried out before the dyeing step, if necessary. The swelling step is carried out, for example, by immersing the PVA-based film in a swelling bath. The swelling bath typically uses water such as distilled water or pure water. The swelling bath may contain any appropriate other component other than water. Examples of the other components include solvents such as alcohol, additives such as surfactants, and iodides. Examples of the iodides include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide, with potassium iodide being preferred. The temperature of the swelling bath is, for example, about 20 to 45°C. The immersion time is, for example, about 10 to 300 seconds.

[0039] The dyeing step is a step of dyeing a PVA-based film with a dichroic substance. Examples of the adsorption method include a method of immersing a PVA-based film in a dye solution containing a dichroic substance, a method of coating the PVA-based film with the dye solution, and a method of spraying the dye solution onto the PVA-based film. From the viewpoint of good adsorption of the dichroic substance, the method of immersing a PVA-based film in the dye solution is preferred.

[0040] Examples of the dichroic substance include iodine and dichroic dyes, with iodine being preferred. When iodine is used as the dichroic substance, an iodine aqueous solution is preferably used as the dyeing solution. The iodine content of the iodine aqueous solution is preferably about 0.04 to 5.0 parts by weight per 100 parts by weight of water. Furthermore, to increase the solubility of iodine in water, it is preferable to blend iodide into the iodine aqueous solution. Potassium iodide is preferably used as the iodide. The iodide content is preferably about 0.3 to 15 parts by weight per 100 parts by weight of water. From the viewpoint of obtaining a polarizing film with good optical properties, the ratio of the iodine and iodide contents in the iodine aqueous solution is preferably about 1:5 to 1:20, more preferably about 1:5 to 1:10. The temperature of the dyeing solution is, for example, 20 to 50°C. The immersion time is, for example, 5 seconds to 5 minutes.

[0041] In the crosslinking step, a boron compound is usually used as a crosslinking agent. Examples of the boron compound include boric acid and borax, with boric acid being preferred. The boron compound is usually used in the form of an aqueous solution. In the aqueous solution containing the boron compound, the concentration of the boron compound is, for example, about 0.5 to 15% by weight, preferably about 1 to 10% by weight. The aqueous solution containing the boron compound may also contain an iodide such as potassium iodide.

[0042] Examples of the crosslinking step include a method of immersing a PVA-based film in an aqueous solution containing a boron compound, a method of applying an aqueous solution containing a boron compound to a PVA-based film, and a method of spraying an aqueous solution containing a boron compound onto a PVA-based film, and the method of immersing in an aqueous solution containing a boron compound is preferred.

[0043] In the crosslinking step, the temperature of the aqueous solution containing the boron compound is, for example, 25° C. or higher, preferably about 30 to 85° C., and more preferably about 40 to 70° C. The immersion time is, for example, about 5 to 800 seconds, and preferably about 8 to 500 seconds.

[0044] The washing step is carried out after the crosslinking step, if necessary. The washing step is typically carried out by immersing the PVA film in a washing solution. A typical example of the washing solution is pure water. The washing solution may contain an iodide such as potassium iodide. The temperature of the washing solution is, for example, about 5 to 50°C. The immersion time is, for example, about 1 to 300 seconds.

[0045] Furthermore, when producing a polarizing film containing the radical scavenger, the radical scavenger may be contained in one or more treatment baths in the swelling step, washing step, dyeing step, crosslinking step, and stretching step. The concentration of the radical scavenger contained in any of the treatment baths 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 polarizing film, the concentration is usually preferably 0.01 wt % or more, more preferably 0.05 wt % or more, and even more preferably 0.1 wt % or more, and preferably 30 wt % or less, more preferably 25 wt % or less, and even more preferably 20 wt % or less.

[0046] Furthermore, each treatment bath in the swelling, dyeing, crosslinking, stretching, and washing steps may contain additives such as zinc salts, pH adjusters, pH buffers, and other salts. Examples of zinc salts include zinc halides such as zinc chloride and zinc iodide; and inorganic zinc salts such as zinc sulfate and zinc acetate. Examples of pH adjusters include strong acids such as hydrochloric acid, sulfuric acid, and nitric acid, and strong bases such as sodium hydroxide and potassium hydroxide. Examples of pH buffers include carboxylic acids such as acetic acid, oxalic acid, and citric acid, and their salts; and inorganic weak acids such as phosphoric acid and carbonic acid, and their salts. Examples of other salts include chlorides such as sodium chloride, potassium chloride, and barium chloride; nitrates such as sodium nitrate and potassium nitrate; sulfates such as sodium sulfate and potassium sulfate; and salts of alkali metals and alkaline earth metals.

[0047] The drying step may be carried out, for example, by natural drying, air drying, reduced pressure drying, or heat drying, and heat drying is preferred. When heat drying is carried out, the heating temperature is, for example, 30 to 100° C. The drying time is, for example, 20 seconds to 10 minutes.

[0048] <Polarizing film> The polarizing film of the present invention is a polarizing film in which a transparent protective film or an optically functional film is attached to at least one surface of the polarizing film, and the transparent protective film or the optically functional film has a moisture permeability of 200 g / (m 2 24h), and the polarizing film has a single transmittance of 41% or less and is expressed by the general formula (1): ΔTs(%)=Ts 96 -Ts0 (in the general formula (1), Ts0 is the single transmittance of a laminate in which a glass plate is bonded to the surface of the polarizing film opposite to the first film surface via a pressure-sensitive adhesive layer, and Ts 96 represents the single-piece transmittance after the laminate has been heat-treated at 105° C. for 96 hours. The change in the single-piece transmittance (ΔTs) represented by (a) satisfies the condition that the change in the single-piece transmittance (ΔTs) represented by (b) is 0% or more and 5% or less.

[0049] The transparent protective film is not particularly limited, and various transparent protective films used in polarizing films can be used. Examples of materials that can be used to form the transparent protective film include thermoplastic resins that are excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, and isotropy. Examples of 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 transparent protective film can also include 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.

[0050] The thickness of the transparent protective film can be determined as appropriate, but generally, from the viewpoints of workability such as strength and handling, thinness, etc., it is preferably about 1 to 500 μm, more preferably about 1 to 300 μm, and even more preferably about 5 to 100 μm.

[0051] The transparent protective film may contain any appropriate additive, such as an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, a coloring inhibitor, a flame retardant, an antistatic agent, a pigment, a colorant, etc. In particular, when the transparent protective film contains an ultraviolet absorber, the light resistance of the polarizing film can be improved.

[0052] The optical functional film is not particularly limited, and can be one or more layers of optical functional films that are sometimes used in the formation of liquid crystal displays, such as reflectors, semi-transmitters, retardation plates (including half- and quarter-wave plates), viewing angle compensation films, and brightness enhancement films such as linearly polarized light separation films. Examples of polarizing films having the optical functional film include reflective polarizing films or semi-transmitting polarizing films obtained by laminating a reflector or semi-transmitting reflector on the polarizing film, elliptically polarizing films or circularly polarizing films obtained by laminating a retardation plate on the polarizing film, wide-viewing angle polarizing films obtained by laminating a viewing angle compensation film on the polarizing film, and polarizing films obtained by laminating a brightness enhancement film on the polarizing film.

[0053] The transparent protective film or the optically functional film (the first film on one side of the polarizing film) attached to at least one side of the polarizing film has a moisture permeability of 200 g / (m 2 24h) or less, and from the viewpoint of preventing the deterioration of the polarization degree of the polarizing film in a high-temperature and high-humidity environment, the moisture permeability is 180g / (m 2 24h) or less, and 150g / (m 2 24h) or less. In addition, the other transparent protective film or optically functional film (the second film on the other side of the polarizing film) has a moisture permeability of 200 g / (m) from the viewpoint of production efficiency in the drying process after laminating the polarizing film and the transparent protective film or the optically functional film. 2 24h) or more, and 300g / (m 2 24h) or more, and from the viewpoint of suppressing the decrease in the polarization degree of the polarizing film in a high-temperature and high-humidity environment, the moisture permeability is preferably 1200g / (m 2 24h) or less, and 1000g / (m 2The moisture permeability can be calculated in accordance with the moisture permeability test (cup method) of JIS Z0208 by cutting a sample to a diameter of 60 mm, placing it in a moisture permeability cup containing approximately 15 g of calcium chloride, placing it in an incubator at a temperature of 40°C and a humidity of 90% RH, and measuring the increase in weight of the calcium chloride before and after leaving it for 24 hours.

[0054] When the transparent protective film or the optically functional film is attached to both sides of the polarizing film, the films on both sides may be the same or different.

[0055] The surface of the transparent protective film or the optical functional film to which the polarizing film is not attached may be provided with a functional layer such as a hard coat layer, an anti-reflection layer, an anti-sticking layer, a diffusion layer, an anti-glare layer, etc. The functional layer such as the hard coat layer, the anti-reflection layer, the anti-sticking layer, the diffusion layer, or the anti-glare layer may be provided as a part of the film itself, or may be provided as a separate layer from the film.

[0056] The polarizing film and the transparent protective film or the optically functional film, or the polarizing film and the functional layer, are usually bonded together via a pressure-sensitive adhesive layer or an adhesive layer.

[0057] The pressure-sensitive adhesive that forms the pressure-sensitive adhesive layer can be any of various pressure-sensitive adhesives used in polarizing films, including, for example, rubber-based pressure-sensitive adhesives, acrylic-based pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, vinyl alkyl ether-based pressure-sensitive adhesives, polyvinyl alcohol-based pressure-sensitive adhesives, polyvinyl pollidone-based pressure-sensitive adhesives, polyacrylamide-based pressure-sensitive adhesives, cellulose-based pressure-sensitive adhesives, etc. Among these, acrylic-based pressure-sensitive adhesives are preferred.

[0058] Examples of methods for forming the pressure-sensitive adhesive layer include a method in which the pressure-sensitive adhesive is applied to a release-treated separator or the like, dried to form a pressure-sensitive adhesive layer, and then transferred to a polarizing film or the like, or a method in which the pressure-sensitive adhesive is applied to a polarizing film or the like, and dried to form a pressure-sensitive adhesive layer, etc. The thickness of the pressure-sensitive adhesive layer is not particularly limited and is, for example, about 1 to 100 μm, and preferably about 2 to 50 μm.

[0059] The adhesive for forming the adhesive layer can be any of various adhesives used in polarizing films, including, for example, isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl latex-based adhesives, water-based polyesters, etc. These adhesives are usually used as adhesives made from aqueous solutions (water-based adhesives) and contain 0.5 to 60% by weight of solids.

[0060] The aqueous adhesive 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, such as alkylenediamines, isocyanates, epoxies, aldehydes, and amino-formaldehydes such as methylol urea and methylol melamine. The amount of crosslinking agent in the adhesive is typically about 10 to 60 parts by weight per 100 parts by weight of the polymer or other components that make up the adhesive.

[0061] In addition to the above, examples of the adhesive include active energy ray-curable adhesives such as ultraviolet ray-curable adhesives and electron beam-curable adhesives. Examples of the active energy ray-curable adhesives include (meth)acrylate-based adhesives. Examples of the curable components in the (meth)acrylate-based adhesives include compounds having a (meth)acryloyl group and compounds having a vinyl group. Examples of the compounds having a (meth)acryloyl group include alkyl (meth)acrylates such as linear alkyl (meth)acrylates, alicyclic alkyl (meth)acrylates, and polycyclic alkyl (meth)acrylates having 1 to 20 carbon atoms; hydroxyl group-containing (meth)acrylates; and epoxy group-containing (meth)acrylates such as glycidyl (meth)acrylate. The (meth)acrylate adhesive may contain a nitrogen-containing monomer such as hydroxyethyl (meth)acrylamide, N-methylol (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-ethoxymethyl (meth)acrylamide, (meth)acrylamide, or (meth)acryloylmorpholine. The (meth)acrylate adhesive may contain a polyfunctional monomer as a crosslinking component, such as tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, tricyclodecane dimethanol diacrylate, cyclic trimethylolpropane formal acrylate, dioxane glycol diacrylate, or EO-modified diglycerin tetraacrylate. Furthermore, compounds containing epoxy groups or oxetanyl groups can also be used as cationic polymerization-curable adhesives. The epoxy group-containing compound is not particularly limited as long as it has at least two epoxy groups in the molecule, and various commonly known curable epoxy compounds can be used.

[0062] The adhesive may contain appropriate additives as needed, such as coupling agents such as silane coupling agents and titanium coupling agents, adhesion promoters such as ethylene oxide, ultraviolet absorbers, anti-degradants, dyes, processing aids, ion trapping agents, antioxidants, tackifiers, fillers, plasticizers, leveling agents, foam inhibitors, antistatic agents, heat stabilizers, and hydrolysis stabilizers.

[0063] The adhesive may be applied to either the transparent protective film or the optical functional film side (or the functional layer side), or the polarizing film side, or may be applied 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. The thickness of the adhesive layer is not particularly limited, and when a water-based adhesive or the like is used, it is preferably about 30 to 5,000 nm, more preferably about 100 to 1,000 nm. When a UV-curable adhesive, an electron beam-curable adhesive, or the like is used, it is preferably about 0.1 to 100 μm, more preferably about 0.5 to 10 μm.

[0064] The transparent protective film or the optical functional film and the polarizing film, or the polarizing film and the functional layer, may be laminated via an intervening layer such as a surface modification treatment layer, an easy-adhesive layer, a blocking layer, or a refractive index adjustment layer.

[0065] Examples of the surface modification treatment for forming the surface modification layer include corona treatment, plasma treatment, primer treatment, and saponification treatment.

[0066] Examples of the easy-adhesion adhesive that forms the easy-adhesion layer include forming materials containing various resins having a polyester skeleton, a polyether skeleton, a polycarbonate skeleton, a polyurethane skeleton, a silicone-based skeleton, a polyamide skeleton, a polyimide skeleton, a polyvinyl alcohol skeleton, etc. The easy-adhesion layer is usually provided on the film in advance, and the easy-adhesion layer side of the film and the polarizing film are laminated with the pressure-sensitive adhesive layer or the adhesive layer.

[0067] The blocking layer has a function of preventing impurities such as oligomers and ions eluted from the transparent protective film or the optical functional film from migrating (penetrating) into the polarizing film. The blocking layer may be any layer that is transparent and can prevent impurities from eluting from the transparent protective film or the optical functional film. Examples of materials that can form the blocking layer include urethane prepolymer-based forming materials, cyanoacrylate-based forming materials, and epoxy-based forming materials.

[0068] The refractive index adjusting layer is a layer provided to suppress a decrease in transmittance due to reflection between layers having different refractive indices, such as the transparent protective film or the optical functional film and a polarizing film, etc. Examples of refractive index adjusting materials that form the refractive index adjusting layer include forming agents containing various resins such as silica-based, acrylic-based, acrylic-styrene-based, and melamine-based resins and additives.

[0069] The polarizing film of the present invention has a structure represented by the general formula (1): ΔTs(%)=Ts 96 -Ts0 (in the general formula (1), Ts0 is the single transmittance of a laminate in which a glass plate is bonded to the surface of the polarizing film opposite to the first film surface via a pressure-sensitive adhesive layer, and Ts 96 represents the single-piece transmittance after the laminate is heat-treated at 105°C for 96 hours. The change in single-piece transmittance (ΔTs) represented by (ΔTs) satisfies the condition that it is 0% or more and 5% or less. Preferably, the change in single-piece transmittance (ΔTs) is 0% or more and 3% or less.

[0070] The polarizing film has a single transmittance of 41% or less. From the viewpoint of display panel brightness, the polarizing film preferably has a single transmittance of 30% or more, more preferably 35% or more, and from the viewpoint of controlling the initial polarization degree to 99.98 or more, the single transmittance is preferably 41% or less, more preferably 40% or less. The single transmittance is the Y value measured using an integrating sphere spectrophotometer (for example, JASCO Corporation, product name: V7100) using a 2-degree visual field (C light source) according to JIS Z8701 and corrected for luminosity.

[0071] The polarizing film preferably has a polarization degree of 99.98% or more, and more preferably has a polarization degree of 99.99% or more.

[0072] An adhesive layer for bonding other members may be provided on one or both surfaces of the polarizing film. A pressure-sensitive adhesive layer is suitable as the adhesive layer. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited, and may be appropriately selected from those having, as a base polymer, an acrylic polymer, a silicone polymer, polyester, polyurethane, polyamide, polyether, a fluorine-based polymer, a rubber-based polymer, or the like. In particular, pressure-sensitive adhesives that have excellent optical transparency, adequate wettability, cohesion, and adhesive properties, and excellent weather resistance, heat resistance, and the like, such as pressure-sensitive adhesives containing acrylic polymers, are preferably used.

[0073] The adhesive layer can be applied to one or both surfaces of the polarizing film by any suitable method. Examples of adhesive layer application include preparing an adhesive solution and applying it directly to the polarizing film by a suitable application method such as casting or coating, or forming an adhesive layer on a separator and then transferring it onto the polarizing film. The thickness of the adhesive layer can be determined appropriately depending on the intended use, adhesive strength, etc., and is generally 1 to 500 μm, preferably 5 to 200 μm, and more preferably 10 to 100 μm. A polarizing film having an adhesive layer on at least one surface thereof is also referred to as an adhesive layer-attached polarizing film.

[0074] It is preferable that a separator be temporarily attached to cover the exposed surface of the pressure-sensitive adhesive layer to prevent contamination, etc., until the product is put into practical use. This prevents contamination, etc., of the pressure-sensitive adhesive layer under normal handling conditions. Examples of the separator include suitable thin sheets such as plastic films, rubber sheets, paper, cloth, nonwoven fabrics, nets, foam sheets, metal foils, and laminates thereof, which are coated with a suitable release agent, such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide-based release agent, as needed. [Example]

[0075] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0076] Example 1 <Preparation of polarizing membrane and polarizing film> An isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 μm) was used as the thermoplastic resin substrate. One side of the substrate was subjected to a corona treatment, and an aqueous solution containing polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (degree of polymerization 1200, degree of acetoacetyl modification 4.6%, degree of saponification ≥99.0 mol%, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER Z200") in a 9:1 ratio was applied to the corona-treated surface and dried at 25°C to form a PVA-based resin layer and a laminate. The resulting laminate was stretched in air at 4.5 times its original size in the direction perpendicular to the longitudinal direction of the laminate at 140°C using a tenter stretching machine (stretching treatment). The laminate was then immersed in a dye bath (aqueous solution containing 1.0 wt% iodine and 7.0 wt% potassium iodide) at a liquid temperature of 25°C for 12 seconds for dyeing (dyeing treatment). Next, the laminate was immersed for 21 seconds in a crosslinking bath (an aqueous solution containing 1.0 wt% boron, 1.0 wt% potassium iodide, and 5.0 wt% of a compound represented by the following general formula (9)) at a liquid temperature of 60°C (crosslinking treatment). The laminate was then immersed for 10 seconds in a cleaning bath (an aqueous solution containing 4.5 wt% potassium iodide) at a liquid temperature of 25°C (cleaning treatment). The laminate was then dried for 21 seconds in an oven at 60°C (drying treatment), yielding a laminate having a 1.2 μm-thick PVA-based resin layer (polarizing film). Next, a linearly polarized light separating film (manufactured by 3M, product name "DBEF", moisture permeability 8.5 g / (m)) was attached as a first film to the polarizing film side of the resulting laminate having a PVA-based resin layer (polarizing film) via a 20 μm-thick acrylic adhesive layer. 2 After laminating the two films for 24 hours, the thermoplastic resin substrate was peeled off, and a 20 μm thick acrylic adhesive layer was applied to the peeled surface to produce a polarizing film. The single film transmittance was 39.7%. [ka]

[0077] [Method for measuring the iodine content (wt%) in polarizing film] The iodine concentration (wt %) of the polarizing film was determined using a fluorescent X-ray analyzer (manufactured by Rigaku Corporation, trade name "ZSX-PRIMUS IV", measurement diameter: ψ20 mm) according to the following formula. Iodine concentration (wt%) = 14.474 × (fluorescent X-ray intensity) / (film thickness) (kcps / μm). The coefficient used to calculate the concentration varies depending on the measuring device, but this coefficient can be determined using an appropriate calibration curve. The results are shown in Table 1.

[0078] [Method for measuring the dehydration temperature of polyenation] The polarized film was introduced into a heating furnace-type pyrolyzer (Frontier Labs, PY-2020iD), and the generated gas was directly introduced into a TOFMS (JEOL, MS-T100GCV) for measurement by evolved gas analysis (EGA / TOFMS). The peak temperature at which the detected water had the maximum intensity was determined, and this temperature was taken as the dehydration temperature for polyenation. [Measurement conditions] Temperature rise conditions: 40℃ → +10℃ / min → 350℃ Interface: Inert fused silica tubing, 2.5m x 0.15mm id Carrier gas: He (1.0 mL / min) Inlet temperature: 300℃ Inlet: Split ratio 20:1 Interface temperature: 300℃ Mass spectrometer: TOFMS Ionization method: EI method Mass range: m / z=18

[0079] [Method for measuring the content (wt%) of radical scavenger in polarizing film] Approximately 20 mg of polarizing film was collected, weighed, and dissolved in 1 mL of water by heating, then diluted with 4.5 mL of methanol. The resulting extract was filtered through a membrane filter, and the concentration of the radical scavenger in the filtrate was measured using HPLC (Waters ACQUITY UPLC H-class Bio). The results are shown in Table 1.

[0080] [Method for measuring the degree of polarization] The degree of polarization of a polarizing film can be measured using a spectrophotometer (manufactured by JASCO Corporation, product name "V7100"). Specifically, the degree of polarization can be measured by measuring the parallel transmittance (H0) and crossed transmittance (H90) of the polarizing film and calculating it using the formula: Polarization degree (%) = {(H0 - H90) / (H0 + H90)} 1 / 2 × 100. The parallel transmittance (H0) is the transmittance value of a parallel-type laminated polarizing film made by stacking two identical polarizing films so that their absorption axes are parallel to each other. The crossed transmittance (H90) is the transmittance value of a crossed-type laminated polarizing film made by stacking two identical polarizing films so that their absorption axes are perpendicular to each other. These transmittances are Y values ​​corrected for luminosity using a 2-degree visual field (illuminant C) according to JIS Z 8701-1982. The results are shown in Table 1.

[0081] [Evaluation of single-piece transmittance in high-temperature environments] The polarized film obtained above was cut into a size of 5.0 x 4.5 cm so that the absorption axis of the polarizing film was parallel to the long side, and a 1.3 mm alkali-free glass plate was attached to the adhesive layer surface of the polarized film to produce a laminate. The resulting laminate was left to stand in a hot air oven at 105°C for 96 hours, and the single-piece transmittance (ΔTs) was measured before and after heating. The single-piece transmittance was measured using a spectrophotometer (manufactured by JASCO Corporation, product name "V7100") and evaluated according to the following criteria. The measurement wavelength was 380 to 700 nm (5 nm intervals). The results are shown in Table 1. ΔTs(%)=Ts 96 -Ts0 where Ts0 is the single transmittance of the laminate before heating, and Ts 96 is the single transmittance of the laminate after heating for 96 hours.

[0082] [Evaluation of humidity durability] The laminate sample was left to stand in a moist heat oven at 85°C and 85% RH for 120 hours, after which the polarization degree was evaluated using the spectrophotometer (manufactured by JASCO Corporation, product name "V7100"), and a polarization degree of 99% or more after the test was set as the pass criterion. The results are shown in Table 1.

[0083] <Example 2> A polarizing film and a polarizing film were prepared in the same manner as in Example 1, except that in the above <Preparation of Polarizing Film and Polarizing Film>, the crosslinking bath was changed to a crosslinking bath (an aqueous solution containing 1.0 wt % boron, 1.0 wt % potassium iodide, and 10.0 wt % compound represented by general formula (9)). The results of the above measurements and evaluations of the polarizing film and the polarizing film are shown in Table 1.

[0084] Example 3 Polarizing films and polarizing films were produced in the same manner as in Example 1, except that in the above <Preparation of Polarizing Film and Polarizing Film>, the dyeing bath was changed to a dyeing bath (an aqueous solution having an iodine concentration of 0.7 wt % and a potassium iodide concentration of 4.9 wt %) and the crosslinking bath was changed to a crosslinking bath (an aqueous solution having a boron concentration of 1.0 wt %, a potassium iodide concentration of 1.0 wt %, and a compound represented by general formula (9) at a concentration of 10.0 wt %). The results of the above measurements and evaluations of the polarizing film and polarizing film are shown in Table 1.

[0085] Example 4 A polarizing film and a polarizing film were prepared in the same manner as in Example 1, except that in the above <Preparation of Polarizing Film and Polarizing Film>, the crosslinking bath was changed to a crosslinking bath (an aqueous solution containing 1.0 wt % boron, 1.0 wt % potassium iodide, and 10.0 wt % compound represented by general formula (8)). The results of the above measurements and evaluations of the polarizing film and the polarizing film are shown in Table 1.

[0086] <Example 5> A polarizing film and a polarizing film were prepared in the same manner as in Example 1, except that in the above <Preparation of Polarizing Film and Polarizing Film>, the crosslinking bath was changed to a crosslinking bath (an aqueous solution containing 1.0 wt % boron, 1.0 wt % potassium iodide, and 10.0 wt % compound represented by general formula (7)). The results of the above measurements and evaluations of the polarizing film and the polarizing film are shown in Table 1.

[0087] Example 6 In the above <Preparation of Polarizing Film and Polarizing Film>, a (meth)acrylic resin transparent protective film (manufactured by Nippon Shokubai Co., Ltd., moisture permeability 125 g / (m)) was applied as a first film to the polarizing film side of the laminate having the obtained PVA resin layer (polarizing film) via an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm. 2 A polarizing film and a polarizing membrane were prepared in the same manner as in Example 1, except that the polarizing membrane and the polarizing film were laminated together after 24 h. The results of the above measurements and evaluations of the polarizing membrane and the polarizing film are shown in Table 1.

[0088] Example 7 In the above <Preparation of Polarizing Film and Polarizing Film>, a linearly polarized light separating film (manufactured by 3M, product name "DBEF", moisture permeability 85 g / (m)) was applied as a first film to the polarizing film side of the laminate having the obtained PVA resin layer (polarizing film) via an acrylic adhesive layer having a thickness of 20 μm. 2 After laminating the thermoplastic resin substrate to the laminate, a 20 μm thick acrylic adhesive layer was placed on the peeled surface, and a triacetyl cellulose transparent protective film (manufactured by Fujifilm, product name "TJ40UL", moisture permeability 380 g / (m)) was applied as a second film. 2 A polarizing film and a polarizing membrane were produced in the same manner as in Example 1, except that the transparent triacetyl cellulose protective film and the polarizing membrane were laminated together and a 20 μm-thick acrylic adhesive layer was applied to the triacetyl cellulose transparent protective film side. The results of the above measurements and evaluations of the polarizing membrane and the polarizing film are shown in Table 1.

[0089] Example 8 In the above <Preparation of Polarizing Film and Polarizing Film>, a laminate was prepared by forming a PVA-based resin layer so that the final polarizing film would have a thickness of 4.8 μm, and the dyeing bath was changed to a dyeing bath (an aqueous solution having an iodine concentration of 0.5 wt % and a potassium iodide concentration of 3.5 wt %) and the crosslinking bath was changed to a crosslinking bath (an aqueous solution having a boron concentration of 1.0 wt %, a potassium iodide concentration of 1.0 wt %, and a compound represented by the general formula (9) at a concentration of 10.0 wt %). A polarizing film and a polarizing film were prepared in the same manner as in Example 1. The results of the above measurements and evaluations of the polarizing film and polarizing film are shown in Table 1.

[0090] Example 9 Polarizing films and polarizing films were produced in the same manner as in Example 1, except that in the above <Preparation of Polarizing Film and Polarizing Film>, the dyeing bath was changed to a dyeing bath (an aqueous solution having an iodine concentration of 1.5 wt % and a potassium iodide concentration of 10.5 wt %) and the crosslinking bath was changed to a crosslinking bath (an aqueous solution having a boron concentration of 1.0 wt %, a potassium iodide concentration of 1.0 wt %, and a compound represented by general formula (9) at a concentration of 15.0 wt %). The results of the above measurements and evaluations of the polarizing film and polarizing film are shown in Table 1.

[0091] <Comparative Example 1> A polarizing film and a polarizing film were prepared in the same manner as in Example 1, except that in the above <Preparation of Polarizing Film and Polarizing Film>, the crosslinking bath was changed to a crosslinking bath (an aqueous solution with a boron concentration of 1.0 wt % and a potassium iodide concentration of 1.0 wt %). The results of the above measurements and evaluations of the polarizing film and the polarizing film are shown in Table 1.

[0092] <Comparative Example 2> In the above <Preparation of Polarizing Film and Polarizing Film>, a triacetyl cellulose resin transparent protective film (manufactured by Konica Minolta, Inc., product name "KC2CT", moisture permeability 380 g / (m)) was applied as a first film to the polarizing film side of the laminate having the PVA resin layer (polarizing film) obtained, via an acrylic adhesive layer having a thickness of 20 μm. 2 A polarizing film and a polarizing membrane were prepared in the same manner as in Example 1, except that the polarizing membrane and the polarizing film were laminated together after 24 h. The results of the above measurements and evaluations of the polarizing membrane and the polarizing film are shown in Table 1.

[0093] <Comparative Example 3> Polarizing films and polarizing films were produced in the same manner as in Example 1, except that in the above <Preparation of Polarizing Film and Polarizing Film>, the dyeing bath was changed to a dyeing bath (an aqueous solution having an iodine concentration of 0.5 wt % and a potassium iodide concentration of 3.5 wt %) and the crosslinking bath was changed to a crosslinking bath (an aqueous solution having a boron concentration of 1.0 wt %, a potassium iodide concentration of 1.0 wt %, and a compound represented by general formula (9) at a concentration of 10.0 wt %). The results of the above measurements and evaluations of the polarizing film and polarizing film are shown in Table 1.

[0094] <Comparative Example 4> In the above <Preparation of Polarizing Film and Polarizing Film>, a linearly polarized light separating film (manufactured by 3M, product name "DBEF") was attached as the first film to the polarizing film side of the laminate having a PVA resin layer (polarizing film) via a 20 μm-thick acrylic pressure-sensitive adhesive layer, and then the thermoplastic resin substrate was peeled off. The peeled surface was coated with a treatment liquid (aqueous solution of 0.5 wt % sodium bicarbonate and 50 wt % isopropyl alcohol: pH 6.0) using a bar coater and dried at 50°C for 60 seconds. After that, a 20 μm-thick acrylic pressure-sensitive adhesive layer was applied to prepare a polarizing film. Polarizing films and polarizing films were prepared in the same manner as in Example 1. The results of the above measurements and evaluations of the polarizing film and polarizing film are shown in Table 1.

[0095] <Comparative Example 5> A polarizing film and a polarizing film were produced in the same manner as in Example 1, except that in the above <Production of Polarizing Film and Polarizing Film>, the dye bath was changed to a dye bath (an aqueous solution containing potassium iodide at a concentration of 15.0 wt % and ferric sulfate n-hydrate at 2.0 wt %). The results of the above measurements and evaluations of the polarizing film and the polarizing film are shown in Table 1.

[0096] [Table 1]

Claims

1. A polarizing film in which a transparent protective film or an optically functional film is attached to at least one surface of a polarizing film, the polarizing film is formed by adsorbing and aligning iodine on a polyvinyl alcohol-based film, and has an iodine concentration of more than 10% by weight; the polarizing film contains a radical scavenger, and the weight ratio of the content of the radical scavenger to the content of iodine (radical scavenger content / iodine content) is 0.01 or more; the radical scavenger is one or more compounds selected from the group consisting of hindered phenol compounds, hindered amine compounds, phosphorus compounds, sulfur compounds, benzotriazole compounds, benzophenone compounds, hydroxylamine compounds, salicylic acid ester compounds, triazine compounds, and compounds having a nitroxy radical or a nitroxide group, The transparent protective film or the optical functional film has a moisture permeability of 200 g / (m ２ - 24h) or less, The polarizing film has a single transmittance of 41% or less, and General formula (1): ΔTs (%) = Ts ９６ -Ts ０ (In the general formula (1), Ts ０ is the single transmittance of a laminate in which a glass plate is bonded to the surface opposite to the first film surface of the polarizing film via a pressure-sensitive adhesive layer, and Ts ９６ represents the single-piece transmittance after the laminate is heat-treated at 105°C for 96 hours.) A polarizing film, characterized in that a change in single-piece transmittance (ΔTs) represented by

2. 2. The polarizing film according to claim 1, wherein the polarizing film has a thickness of 10 [mu]m or less.

3. 3. The polarizing film according to claim 1, wherein the radical scavenger is a compound having a nitroxy radical or a nitroxide group.

4. 4. The polarizing film according to claim 1, wherein the polarization degree is 99.98% or more.

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