Polarizing film and polarizing film

Abstract

The present invention provides a polarizing film which is formed by adsorbing iodine on a polyvinyl alcohol-based film and performing orientation, has an iodine content of more than 10% by weight and a monomer transmittance of 41% or less, and contains a radical scavenger, the weight ratio of the content of the radical scavenger to the content of the iodine (the content of radical scavenger / the content of iodine) is 0.01 or more, and in a generated gas analysis, in the presence of an inert gas, under conditions of a temperature increase rate of 10 DEG C / min and a temperature increase range of 40 DEG C to 350 DEG C, the content of the radical scavenger and the content of the iodine are separated from each other, and the content of the radical scavenger and the content of the iodine are separated from each other. The peak temperature of the maximum intensity of water detected by the polarizing film is 175 DEG C or more. The polarizing film has a high iodine content, an initial monomer transmittance of 41% or less, and an excellent effect of suppressing a decrease in monomer transmittance due to coloring of the polarizing film in a high-temperature environment.

Description

[0001] This application is a divisional application of the application with the application number 202180028180.2 and the title “POLARIZING FILM AND POLARIZING FILM” filed on March 19, 2021. TECHNICAL FIELD

[0002] The present application relates to a polarizing film and a polarizing film. BACKGROUND

[0003] In the past, as a polarizing film for various image display devices such as liquid crystal display devices, organic EL display devices, etc., a polyvinyl alcohol-based film subjected to dyeing treatment (containing iodine, a dichroic dye, or the like) has been used from the viewpoint of simultaneously having high transmittance and high polarization degree. The polarizing film is manufactured by, after subjecting a polyvinyl alcohol-based film to each treatment such as swelling, dyeing, crosslinking, stretching, etc. in a bath, subjecting to a cleaning treatment, and then performing drying. In addition, the above-described polarizing film is generally used in the form of a polarizing film (polarizing plate) in which a protective film such as cellulose triacetate is attached to one or both surfaces thereof with an adhesive.

[0004] On the other hand, with thinning of the polarizing film, a polarizing film having a high content of iodine is required (Patent Document 1). Furthermore, in such a thin polarizing film, a polarizing film capable of suppressing the amount of change in monomer transmittance in a high-temperature environment (105°C x 30 hours) is also known (Patent Document 2).

[0005] PRIOR ART DOCUMENTS

[0006] PATENT DOCUMENTS

[0007] Patent Document 1: International Publication No. 2018 / 186244

[0008] Patent Document 2: International Publication No. 2019 / 103002 SUMMARY

[0009] PROBLEMS TO BE SOLVED BY THE INVENTION

[0010] However, the thin polarizing film specifically disclosed in Patent Documents 1 and 2 does not sufficiently suppress the decrease in monomer transmittance in a high-temperature environment, and there is room for improvement in this performance.

[0011] On the other hand, the present inventors, etc. have found that iodine contained in an iodine-based polarizing film promotes polyenization in a high-temperature environment. Therefore, in order to suppress the decrease in monomer transmittance due to coloring of the polarizing film in a high-temperature environment, it is effective to reduce the content of iodine in the polarizing film. On the other hand, it is difficult to obtain a polarizing film having a good polarization degree and a high content of iodine.

[0012] In addition, as described in Patent Document 2, in a polarizing film having a high iodine content, from the viewpoint of improving the contrast ratio by setting a low monomer transmittance, a polarizing film having a monomer transmittance of 41% or less is required.

[0013] In view of the above, an object of the present application is to provide a polarizing film having a high iodine content, which has an initial monomer transmittance of 41% or less and excellent inhibitory effect on reduction in monomer transmittance due to discoloration of the polarizing film in a high-temperature environment.

[0014] In addition, an object of the present application is to provide a polarizing film using the above-described polarizing film.

[0015] Method for solving the problem

[0016] That is, the present application relates to a polarizing film formed by adsorbing iodine to a polyvinyl alcohol-based film and orienting the same, which has an iodine content of more than 10% by weight and a monomer transmittance of 41% or less, and in a gas analysis, the peak temperature of the maximum intensity of water detected from the polarizing film is 175°C or higher under the presence of an inert gas at a temperature increase rate of 10°C / min and a temperature increase range of 40°C to 350°C.

[0017] In addition, the present application relates to a polarizing film in which a transparent protective film or an optical functional film is attached to at least one side of the above-described polarizing film.

[0018] Effects of the invention

[0019] The detailed circumstances of the mechanism of action of the effects of the polarizing film of the present application are not clear, but are presumed as follows. However, the present application can be explained without being limited to this mechanism of action.

[0020] The polarizing film of the present application is an iodine-based polarizing film formed by adsorbing iodine to a polyvinyl alcohol-based film and orienting it, and has an iodine content of more than 10% by weight, a monomer transmittance of 41% or less, and, in a gas production analysis, a peak temperature of the maximum intensity of water detected is 175°C or higher under the presence of an inert gas at a temperature increase rate of 10°C / min and a temperature increase range of 40°C to 350°C. As described above, iodine-based polarizing films undergo polyenization due to dehydration of polyvinyl alcohol in a high-temperature environment, but, in the polarizing film of the present application, by setting the temperature at which the dehydration occurs to the high-temperature side, that is, by setting the peak temperature of the maximum intensity of water detected (observed) by a gas production analysis to 175°C or higher, a decrease in monomer transmittance due to coloring of the polarizing film in a high-temperature environment can be suppressed. Furthermore, in the polarizing film of the present application, by setting the iodine content in the polarizing film to a certain value or higher, the peak temperature of the maximum intensity of water detected (observed) by a gas production analysis can be controlled to 175°C or higher, and the monomer transmittance is 41% or less, and the initial degree of polarization is good.

[0021] On the other hand, the present inventors and others have observed that when a polarizing film formed by adsorbing iodine to an iodine-containing polyvinyl alcohol-based film and orienting it is exposed to a high-temperature environment for a certain period of time, radicals are generated from the polarizing film. The time at which the polarizing film is colored by polyenization is very similar to the time at which the radicals are generated, and thus suggests a phenomenon in which radicals are generated due to the progress of polyenization of the polarizing film. Therefore, in order to set the temperature at which the above-described dehydration occurs in the polarizing film to the high-temperature side, that is, to set the peak temperature of the maximum intensity of water detected (observed) by a gas production analysis to 175°C or higher, it is preferable to contain a radical trapping agent in the polarizing film. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is an example of a graph showing a peak of water detected in a gas production analysis using an iodine-based polarizing film as a sample. DETAILED DESCRIPTION

[0023] <Polarizing Film>

[0024] The polarizing film of the present application is an iodine-based polarizing film formed by adsorbing iodine to a polyvinyl alcohol-based film and orienting it, and has an iodine content of more than 10% by weight, a monomer transmittance of 41% or less, and, in a gas production analysis, a peak temperature of the maximum intensity of water detected is 175°C or higher under the presence of an inert gas at a temperature increase rate of 10°C / min and a temperature increase range of 40°C to 350°C.

[0025] The content of the iodine in the polarizing film described above is more than 10% by weight from the viewpoint of making the initial degree of polarization of the polarizing film good. The content of the iodine in the polarizing film described above is preferably 12% by weight or more, more preferably 15% by weight or more from the viewpoint of controlling the initial degree of polarization to be 99.98% or more, and is preferably 30% by weight or less, more preferably 25% by weight or less from the viewpoint of controlling the peak temperature of the maximum intensity of the water detected by the gas evolution analysis to be 175°C or more.

[0026] The thickness of the polarizing film described above is preferably 0.2 μm or more, more preferably 0.5 μm or more from the viewpoint of controlling the initial degree of polarization to be 99.98% or more, and is preferably 10 μm or less, more preferably 8 μm or less, further preferably 5 μm or less from the viewpoint of thinning the polarizing film.

[0027] The monomer transmittance of the polarizing film described above is 41% or less. The monomer transmittance of the polarizing film described above is preferably 30% or more, more preferably 35% or more from the viewpoint of the display panel brightness, and is preferably 41% or less, more preferably 40% or less from the viewpoint of controlling the initial degree of polarization to be 99.98% or more. Note that the monomer transmittance is a Y value obtained by measuring using a spectrophotometer with an integrating sphere (for example, manufactured by Japan Spectroscopic Co., Ltd., product name: V7100) according to JIS Z8701, 2-degree field of view (C light source), and performing visibility correction.

[0028] In the gas evolution analysis, the peak temperature of the maximum intensity of the water detected from the polarizing film described above shows 175°C or more under the condition that the temperature increasing rate is 10°C / min and the temperature increasing range is 40°C to 350°C in the presence of an inert gas. By setting the temperature at which the dehydration reaction of polyvinyl alcohol occurs to the high temperature side, that is, by setting the peak temperature of the maximum intensity of the water detected by the gas evolution analysis to 175°C or more, the polarizing film described above can suppress the decrease in the monomer transmittance caused by the coloring of the polarizing film in a high temperature environment. On the other hand, in the case where the peak temperature of the maximum intensity of the water described above is less than 175°C or more, it is difficult to control the change amount of the monomer transmittance of the polarizing film before and after the heat resistance test (105°C x 96 hours) which is considered as an index of the heat resistance of a display to be 0% or more and 5% or less.

[0029] Figure 1 is an example of a graph showing the peak of the water detected by the gas evolution analysis described above, and the peak temperature of the maximum intensity of the water detected is 175°C or more.

[0030] In addition, the above gas production analysis method is a method in which a gas chromatograph device and a mass spectrometer device are directly connected by an inert metal capillary or the like and the gas produced when a sample is heated is analyzed in real time, and is generally referred to as an EGA / MS method, an EGA / TOFMS method, or the like.

[0031] The above polarizing film preferably contains a radical trapping agent. It is presumed that the above trapping agent can trap radicals produced from the polyvinyl alcohol of the polarizing film due to heating, and the temperature at which polyene dehydration reaction occurs is set to the high temperature side. As the above radical trapping agent, for example, a compound such as a hindered phenol, a hindered amine, a phosphorus, a sulfur, a benzotriazole, a benzophenone, a hydroxylamine, a salicylate, a triazine, or the like can be given. As the above radical trapping agent, from the viewpoint that the temperature at which polyene dehydration reaction occurs can be easily set to the high temperature side, a compound having a nitroxyl radical or a nitroxyl group, for example, is preferable.

[0032] As the above compound having a nitroxyl radical or a nitroxyl group, from the viewpoint that the radical is relatively stable at room temperature in the air, an N-hydrocarbyloxy compound (a compound having a C-N(-C)-O · As the compound having a functional group (O · denotes an oxygen radical), a publicly known compound can be used. As the N-hydrocarbyloxy compound, for example, a compound having an organic group having the following structure, or the like can be given.

[0033] [Chemical Formula 1]

[0034]

[0035] (In General Formula (1), R 1 denotes an oxygen radical, R 2 ~R 5 independently denotes a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and n denotes 0 or 1), and it is to be noted that the left side of the dotted line portion in General Formula (1) denotes an arbitrary organic group.

[0036] As the compound having the above organic group, for example, a compound represented by the following General Formulas (2) to (5), or the like can be given.

[0037] [Chemical Formula 2]

[0038]

[0039] (In General Formula (2), R 1 ~R 5 and n have the same meanings as described above, R 6 denotes a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an acyl group, or an aryl group, and n denotes 0 or 1.)

[0040] [Chemical Formula 3]

[0041]

[0042] (In general formula (3), R) 1 ~R 5 And n has the same meaning as above, R 7 and R 8 (Independently representing a hydrogen atom, an alkyl group, an acyl group, or an aryl group having 1 to 10 carbon atoms.)

[0043] [Chemical Formula 4]

[0044]

[0045] (In general formula (4), R) 1 ~R 5 And n has the same meaning as above, R 9 ~R 11 Independently representing a hydrogen atom, an alkyl group, acyl group, amino group, alkoxy group, hydroxyl group, or aryl group having 1 to 10 carbon atoms.

[0046] [Chemical Formula 5]

[0047]

[0048] (In general formula (5), R) 1 ~R 5 And n has the same meaning as above, R 12 (This refers to a hydrogen atom, or an alkyl, amino, alkoxy, hydroxyl, or aryl group with 1 to 10 carbon atoms.)

[0049] In the above general formulas (1) to (5), from the perspective of ease of acquisition, R 2 ~R 5 Preferably, it is an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms. Furthermore, in the above general formula (2), from the viewpoint of ease of acquisition, R... 6 Preferably, it is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, more preferably a hydrogen atom. Furthermore, in the above general formula (3), from the viewpoint of ease of acquisition, R... 7 and R 8 Preferably, it is an alkyl group that is independently composed of hydrogen atoms or has 1 to 10 carbon atoms, and more preferably, it is composed of hydrogen atoms. Furthermore, in the above general formula (4), from the viewpoint of ease of acquisition, R... 9 ~R 11 Preferably, it is an alkyl group having 1 to 10 hydrogen atoms. Furthermore, in the above general formula (5), from the viewpoint of ease of acquisition, R... 12 Preferably, it is hydroxyl, amino, or alkoxy. In the above general formulas (1) to (5), from the viewpoint of ease of acquisition, n is preferably 1.

[0050] In addition, as the above-mentioned N-hydrocarbyloxy compound, for example, an N-hydrocarbyloxy compound described in Japanese Patent Application Publication No. 2003-64022, Japanese Patent Application Publication No. H11-222462, Japanese Patent Application Publication No. 2002-284737, International Publication No. WO 2016 / 047655, or the like can be mentioned.

[0051] In addition, from the viewpoint that radicals generated in the polyene reaction can be efficiently captured, the molecular weight of the above-mentioned radical capturing agent is preferably 1000 or less, more preferably 500 or less, and further preferably 300 or less.

[0052] From the viewpoint that the above-mentioned radical capturing agent can efficiently penetrate into the polarizing film together with water at the time of manufacturing the polarizing film, the viewpoint that the above-mentioned radical capturing agent can be impregnated in the polarizing film at a high concentration, and the viewpoint that even in the case where a polyvinyl alcohol-based film having a large thickness is used, the above-mentioned radical capturing agent can be impregnated in a short time and thus the productivity of the polarizing film can be improved, the above-mentioned radical capturing agent preferably has a solubility of 1 part by weight or more in 100 parts by weight of water at 25°C, more preferably has a solubility of 2 parts by weight or more in 100 parts by weight of water at 25°C, and further preferably has a solubility of 5 parts by weight or more in 100 parts by weight of water at 25°C.

[0053] In addition, as the above-mentioned compound having a nitroxyl radical or a nitroxyl group, for example, the following compounds and the like can be mentioned.

[0054] [Chemical Formula 6]

[0055]

[0056] (In General Formula (6), R represents a hydrogen atom, an alkyl group having a carbon atom number of 1 to 10, an acyl group, or an aryl group.)

[0057] [Chemical Formula 7]

[0058]

[0059] [Chemical Formula 8]

[0060]

[0061] In the case where the above-mentioned polarizing film contains the above-mentioned radical capturing agent, from the viewpoint of suppressing a decrease in monomer transmittance due to coloring of the polarizing film in a high-temperature environment, the content of the above-mentioned radical capturing agent in the above-mentioned polarizing film is preferably 0.1% by weight or more, more preferably 0.2% by weight or more, and further preferably 0.5% by weight or more, and from the viewpoint of appearance, is preferably 30% by weight or less, more preferably 20% by weight or less, and further preferably 10% by weight or less.

[0062] In addition, in the case where the above-described polarizing film contains the above-described radical capturing agent, from the viewpoint of inhibiting a decrease in monomer transmittance due to coloring of the polarizing film in a high-temperature environment, the weight ratio of the content of the above-described radical capturing agent to the content of the above-described iodine (weight ratio of the content of the radical capturing agent / the content of iodine) in the above-described polarizing film is preferably 0.01 or greater, more preferably 0.05 or greater, and from the viewpoint of appearance, is preferably 1.0 or less, more preferably 0.5 or less.

[0063] <Method for manufacturing polarizing film>

[0064] The above-described method for manufacturing a polarizing film includes: subjecting a polyvinyl alcohol-based film (PVA-based film) to an optional swelling step, a washing step, and a drying step, and at least a dyeing step, a crosslinking step, and a stretching step, thereby obtaining the above-described polarizing film. The content of the above-described iodine contained in the above-described polarizing film can be controlled by the concentration of the above-described iodine and iodides such as potassium iodide, and the like, contained in any of the treatment baths in each of the swelling step, the dyeing step, the crosslinking step, the stretching step, and the washing step, the treatment temperature, and the treatment time in the above-described treatment baths. In addition, each of the steps can be performed in any appropriate order, and one step can be performed multiple times as needed.

[0065] The above-described polyvinyl alcohol-based film can be used without particular limitation as a polyvinyl alcohol (PVA)-based film having light transmittance in the visible light region, and obtained by dispersing and adsorbing iodine, a dichroic substance such as a dichroic dye, and the like. As a material for the above-described polyvinyl alcohol-based film, polyvinyl alcohol or a derivative thereof can be cited. As the derivative of the above-described polyvinyl alcohol, for example, polyvinyl formal, polyvinyl acetal, an olefin such as ethylene or propylene, a derivative obtained by modifying with an unsaturated carboxylic acid such as acrylic acid, methacrylic acid, or crotonic acid, an alkyl ester thereof, acrylamide, and the like can be cited. The average degree of polymerization of the above-described polyvinyl alcohol is preferably around 100 to 10000, more preferably around 1000 to 10000, and further preferably around 1500 to 4500. In addition, the saponification degree of the above-described polyvinyl alcohol is preferably around 80 to 100 mol%, and more preferably around 95 mol% to 99.95 mol%. Note that the above-described average degree of polymerization and the above-described saponification degree can be found based on JIS K 6726.

[0066] An additive such as a plasticizer, a surfactant, and the like can be contained in the above-described polyvinyl alcohol-based film. As the above-described plasticizer, for example, a polyhydric alcohol such as glycerol, diglycerol, triglycerol, ethylene glycol, propylene glycol, polyethylene glycol, and the like, and a condensate thereof, and the like can be cited. The amount of the above-described additive is not particularly limited, and for example, it is appropriate for the amount to be around 20% by weight or less in the polyvinyl alcohol-based film.

[0067] The polyvinyl alcohol-based film described above can be used in a laminate obtained by forming a polyvinyl alcohol-based resin layer (PVA-based resin layer) containing a polyvinyl alcohol-based resin (PVA-based resin) on one side of a long strip-shaped thermoplastic resin base material. As a method of producing the above-described laminate, any appropriate method can be employed, and for example, a method in which a coating liquid containing the above-described PVA-based resin is applied to the surface of the above-described thermoplastic resin base material and dried can be mentioned. The thickness of the above-described thermoplastic resin base material is preferably about 20 to 300 μm, and more preferably about 50 to 200 μm. The thickness of the above-described PVA-based resin layer is preferably about 3 to 40 μm, and more preferably about 3 to 20 μm.

[0068] As a material constituting the above-described thermoplastic resin base material, any appropriate thermoplastic resin can be used. As the above-described thermoplastic resin, for example, an ester-based resin such as a polyethylene terephthalate-based resin, a cyclic olefin-based resin such as a norbornene-based resin, an olefin-based resin such as polypropylene, a polyamide-based resin, a polycarbonate-based resin, a copolymer resin thereof, and the like can be mentioned. Among these, a norbornene-based resin, an amorphous (non-crystalline) polyethylene terephthalate-based resin are preferred, and further, from the viewpoint that the stretchability of the thermoplastic resin base material is very excellent and crystallization at the time of stretching can be suppressed, an amorphous (non-crystalline) polyethylene terephthalate-based resin is preferably used. As the amorphous (non-crystalline) polyethylene terephthalate-based resin, a copolymer containing isophthalic acid and / or cyclohexane dicarboxylic acid as a dicarboxylic acid, a copolymer containing cyclohexane dimethanol, diethylene glycol as a diol can be mentioned.

[0069] The above-described thermoplastic resin base material can be subjected to surface treatment (for example, corona treatment, or the like) before the PVA-based resin layer is formed, or an easy-adhesion layer can be formed on the thermoplastic resin base material. By performing such treatment, the adhesion of the thermoplastic resin base material to the PVA-based resin layer can be improved. In addition, the above-described thermoplastic resin base material can be stretched before the PVA-based resin layer is formed.

[0070] The above-described coating liquid is a solution obtained by dissolving a PVA-based resin in a solvent. As the above-described solvent, for example, water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, a polyhydric alcohol such as trimethylolpropane, an amine such as ethylenediamine, diethylenetriamine, and the like can be mentioned, and water is preferred. These solvents can be used alone, or two or more kinds can be used in combination. From the viewpoint that a uniform coating film that adheres to the thermoplastic resin base material can be formed, the concentration of the PVA-based resin in the above-described coating liquid is preferably about 3 to 20 parts by weight per 100 parts by weight of the solvent.

[0071] From the viewpoint of improving the orientation of the polyvinyl alcohol molecule based on stretching, a halide can be incorporated in the above-mentioned coating liquid. As the halide, any appropriate halide can be used, and examples thereof include iodides and sodium chloride. As the iodide, examples thereof include potassium iodide, sodium iodide, lithium iodide, and the like, with potassium iodide being preferred. The concentration of the halide in the above-mentioned coating liquid is preferably about 5 to 20 parts by weight and more preferably about 10 to 15 parts by weight, relative to 100 parts by weight of the PVA-based resin.

[0072] In addition, an additive can be incorporated in the above-mentioned coating liquid. As the additive, examples thereof include plasticizers such as ethylene glycol and glycerin; surfactants such as nonionic surfactants; and the like.

[0073] As the coating method for the above-mentioned coating liquid, any appropriate method can be used, and examples thereof include roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, blade coating (comma coating, and the like), and the like.

[0074] In the above-mentioned stretching process, the PVA-based film is typically uniaxially stretched to about 3 to 7 times. The stretching direction can be the length direction (MD direction) of the film or the width direction (TD direction) of the film. From the viewpoint of laminating the transparent protective film or the optical functional film in a roll-to-roll manner, the stretching direction is preferably the TD direction. The stretching method can be dry stretching, wet stretching, or a combination thereof. In addition, the PVA-based film can be stretched while the crosslinking process, the swelling process, the dyeing process, or the like is performed. The stretching process can be performed in one stage or in multiple stages. In the case where the stretching process is performed in multiple stages, the stretching ratio is the product of the stretching ratios of the respective stages. Note that the stretching direction can correspond to the absorption axis direction of the resulting polarizing film.

[0075] The above-mentioned swelling process is performed before the dyeing process, as necessary. The swelling process is performed by, for example, immersing the PVA-based film in a swelling bath. As the swelling bath, water such as distilled water or pure water is generally used. The above-mentioned swelling bath can contain any appropriate other component(s) other than water. As the other component(s), examples thereof include solvents such as alcohols, additives such as surfactants, and iodides. As the iodide, examples thereof include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, and the like, with potassium iodide being preferred. The temperature of the above-mentioned swelling bath is, for example, about 20 to 45°C. In addition, the immersion time is, for example, about 10 to 300 seconds.

[0076] The above-described dyeing process is a process of dyeing the PVA-based film with a dichroic substance. As the adsorption method, for example, a method of immersing the PVA-based film in a dyeing solution containing the dichroic substance; a method of applying the dyeing solution to the PVA-based film; a method of spraying the dyeing solution to the PVA-based film, and the like are exemplified, and the method of immersing the PVA-based film in the dyeing solution is preferred from the viewpoint of being able to adsorb the dichroic substance favorably.

[0077] As the above-described dichroic substance, for example, iodine, a dichroic dye, and the like are exemplified, and iodine is preferred. In the case where iodine is used as the above-described dichroic substance, an aqueous iodine solution is preferably used as the dyeing solution. The content of iodine in the aqueous iodine solution is preferably about 0.04 to 5.0 parts by weight with respect to 100 parts by weight of water. In addition, in order to improve the solubility of iodine in water, it is preferred to incorporate an iodide in the aqueous iodine solution. As the above-described iodide, potassium iodide is preferably used. The content of the above-described iodide is preferably about 0.3 to 15 parts by weight with respect to 100 parts by weight of water. From the viewpoint of obtaining a polarizing film having good optical properties, the ratio of the contents of iodine and the iodide in the aqueous iodine solution is preferably about 1:5 to 1:20, and 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.

[0078] In the above-described cross-linking process, a boron compound is generally used as the cross-linking agent. As the above-described boron compound, for example, boric acid, borax, and the like are exemplified, and boric acid is preferred. The above-described boron compound is generally 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, and preferably about 1 to 10% by weight. In addition, an iodide such as potassium iodide can be contained in the above-described aqueous solution containing the boron compound.

[0079] The above-described cross-linking process is exemplified by, for example, a method of immersing the PVA-based film in an aqueous solution containing a boron compound; a method of applying an aqueous solution containing a boron compound to the PVA-based film; a method of spraying an aqueous solution containing a boron compound to the PVA-based film, and the like, and the method of immersing in the aqueous solution containing the boron compound is preferred.

[0080] In the above-described cross-linking process, the temperature of the aqueous solution containing the boron compound is, for example, 25°C or higher, and preferably about 30 to 85°C, and further preferably about 40 to 70°C. The immersion time is, for example, about 5 to 800 seconds, and preferably about 8 to 500 seconds.

[0081] The above-described cleaning process is performed after the cross-linking process, as necessary. The cleaning process is typically performed by immersing the PVA-based film in a cleaning solution. As a representative example of the cleaning solution, pure water is exemplified. An iodide such as potassium iodide can be contained in the cleaning solution. The temperature of the cleaning solution is, for example, about 5 to 50°C. The immersion time is, for example, about 1 to 300 seconds.

[0082] In addition, in the case of manufacturing the polarizing film containing the above radical scavenger, it is sufficient that the above radical scavenger is contained in any one or more of the above swelling step, the above cleaning step, the above dyeing step, the above cross-linking step, and the above stretching step. The concentration of the above radical scavenger contained in any one of the above steps is affected by the number of times of treatment, the treatment time, the treatment temperature, and the like, and thus cannot be determined generally. From the viewpoint that the content of the radical scavenger in the polarizing film can be controlled efficiently, it is generally preferable that the concentration of the radical scavenger be 0.01% by weight or more, more preferably 0.05% by weight or more, and further preferably 0.1% by weight or more, and it is preferable that the concentration of the radical scavenger be 30% by weight or less, more preferably 25% by weight or less, and further preferably 20% by weight or less.

[0083] In addition, an additive such as a zinc salt, a pH adjuster, a pH buffer, and another salt can be contained in each of the above swelling step, the above dyeing step, the above cross-linking step, the above stretching step, and the above cleaning step. As the above zinc salt, for example, a halogenated zinc such as zinc chloride and zinc iodide; an inorganic zinc salt such as zinc sulfate and zinc acetate; and the like can be given. As the above pH adjuster, for example, a strong acid such as hydrochloric acid, sulfuric acid, and nitric acid; a strong base such as sodium hydroxide and potassium hydroxide; and the like can be given. As the above pH buffer, for example, a carboxylic acid such as acetic acid, oxalic acid, and citric acid and a salt thereof; an inorganic weak acid such as phosphoric acid and carbonic acid and a salt thereof can be given. As the above another salt, for example, a chloride such as sodium chloride, potassium chloride, and barium chloride; a nitrate such as sodium nitrate and potassium nitrate; a sulfate such as sodium sulfate and potassium sulfate; and a salt of an alkali metal and an alkaline earth metal; and the like can be given.

[0084] The above drying step can be, for example, natural drying, air blowing drying, reduced pressure drying, heating drying, and the like, and is preferably heating drying. In the case of heating drying, the heating temperature is, for example, 30 to 100°C. In addition, the drying time is, for example, 20 seconds to 10 minutes.

[0085] < Polarizing film >

[0086] The polarizing film of the present application is a film in which a transparent protective film or an optical functional film, or the like, is attached to at least one side of the above polarizing film.

[0087] The transparent protective film is not particularly limited, and various transparent protective films used in polarizing films can be used. As a material constituting the transparent protective film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy, and the like can be used. As the thermoplastic resin, for example, cellulose ester-based resins such as cellulose triacetate, polyester-based resins such as polyethylene terephthalate, polyethylene naphthalate, polyether sulfone-based resins, polysulfone-based resins, polycarbonate-based resins, nylon, aramid-based resins such as aromatic polyamides, polyimide-based resins, polyethylene, polypropylene, polyolefin-based resins such as ethylene-propylene copolymers, (meth)acrylic-based resins, cyclic or cyclic polyolefin-based resins having a norbornene structure (norbornene-based resins), polyarylate-based resins, polystyrene-based resins, polyvinyl alcohol-based resins, and mixtures thereof can be exemplified. In addition, the transparent protective film can use a cured layer formed of a thermosetting resin such as a (meth)acrylic-based resin, a urethane-based resin, an acryl urethane-based resin, an epoxy-based resin, a silicone-based resin, or an ultraviolet-curable resin. Among these, cellulose ester-based resins, polycarbonate-based resins, (meth)acrylic-based resins, cyclic polyolefin-based resins, and polyester-based resins are preferred.

[0088] The thickness of the transparent protective film can be appropriately determined, and in general, from the viewpoints of strength, handleability, thinness, and the like, a thickness of about 1 to 500 μm, more preferably about 1 to 300 μm, and further preferably about 5 to 100 μm is preferred.

[0089] Any appropriate additive such as an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, a coloration-preventing agent, a flame retardant, an antistatic agent, a pigment, a colorant, and the like can be contained in the transparent protective film. In particular, in the case where an ultraviolet absorber is contained in the transparent protective film, the light resistance of the polarizing film can be improved.

[0090] The optical functional film is not particularly limited, and for example, an optical functional film such as a reflective plate, a semi-transmissive plate, a phase difference plate (including a 1 / 2, 1 / 4, or the like), a viewing angle compensation film, a linearly polarized light separating film, or the like that is sometimes used in the formation of a liquid crystal display device or the like can be used. As a polarizing film having the optical functional film, for example, a reflective polarizing film or a semi-transmissive polarizing film in which a reflective plate or a semi-transmissive reflective plate is further laminated on the polarizing film, an elliptically polarizing film or a circularly polarizing film in which a phase difference plate is further laminated on the polarizing film, a wide viewing angle polarizing film in which a viewing angle compensation film is further laminated on the polarizing film, or a polarizing film in which a brightness improving film is further laminated on the polarizing film can be exemplified.

[0091] In the case where the transparent protective film or the optical functional film or the like is attached to both surfaces of the polarizing film, the films on the both surfaces can be the same or different.

[0092] A hard coat layer, an anti-reflection layer, an anti-adhesion layer, a diffusion layer, an anti-glare layer, or the like can be provided on the side of the film not bonded to the polarizing film. Note that the hard coat layer, the anti-reflection layer, the anti-adhesion layer, the diffusion layer, the anti-glare layer, or the like can be provided as a layer different from the film in addition to being provided as the film itself.

[0093] The polarizing film and the film, or the polarizing film and the functional layer are typically bonded together with an adhesive layer or a bonding agent layer interposed therebetween.

[0094] As the adhesive forming the adhesive layer, various adhesives used in polarizing films can be used, and examples thereof include rubber-based adhesives, acrylic adhesives, silicone-based adhesives, urethane-based adhesives, vinyl alkyl ether-based adhesives, polyvinyl alcohol-based adhesives, polyvinyl pyrrolidone-based adhesives, polyacrylamide-based adhesives, and cellulose-based adhesives. Among these, an acrylic adhesive is preferable.

[0095] As the method of forming the adhesive layer, a method in which the adhesive is applied to a separator or the like subjected to a release treatment and dried to form an adhesive layer, and then transferred to a polarizing film or the like, or a method in which the adhesive is applied to a polarizing film or the like and dried to form an adhesive layer, or the like can be exemplified. The thickness of the adhesive layer is not particularly limited, and is, for example, about 1 to 100 μm, and preferably about 2 to 50 μm.

[0096] As the bonding agent forming the bonding agent layer, various bonding agents used in polarizing films can be used, and examples thereof include isocyanate-based bonding agents, polyvinyl alcohol-based bonding agents, gelatin-based bonding agents, vinyl-based latexes, and water-based polyesters. These bonding agents are typically used in the form of a bonding agent formed from an aqueous solution (water-based bonding agent), and contain 0.5 to 60% by weight of a solid component.

[0097] The water-based bonding agent can contain a cross-linking agent. As the cross-linking agent, a compound having at least two functional groups having reactivity with components such as a polymer constituting the bonding agent in one molecule can be generally used, and examples thereof include alkylene diamines, isocyanates, epoxies, aldehydes, amino-formaldehyde such as a methylol urea and a methylol melamine. The amount of the cross-linking agent in the bonding agent is generally about 10 to 60 parts by weight per 100 parts by weight of the components such as the polymer constituting the bonding agent.

[0098] As the above-mentioned adhesive, in addition to the above, an active energy ray-curable adhesive such as an ultraviolet-curable adhesive, an electron beam-curable adhesive, and the like can be mentioned. As the above-mentioned active energy ray-curable adhesive, for example, a (meth)acrylate-based adhesive can be mentioned. As the curable component in the above-mentioned (meth)acrylate-based adhesive, for example, a compound having a (meth)acryloyl group, a compound having a vinyl group can be mentioned. As the compound having a (meth)acryloyl group, for example, a (meth)acrylic acid alkyl ester such as a (meth)acrylic acid alkyl ester having 1 to 20 carbon atoms, a (meth)acrylic acid alicyclic alkyl ester, a (meth)acrylic acid polycyclic alkyl ester, and the like; a hydroxyl group-containing (meth)acrylate; an epoxy group-containing (meth)acrylate such as a glycidyl (meth)acrylate, and the like can be mentioned. The (meth)acrylate-based adhesive can contain a nitrogen-containing monomer such as a hydroxyethyl (meth)acrylamide, an N-methylol (meth)acrylamide, an N-methoxy methyl (meth)acrylamide, an N-ethoxy methyl (meth)acrylamide, a (meth)acrylamide, a (meth)acrylamidomorpholine, and the like. The (meth)acrylate-based adhesive can contain a multifunctional monomer such as a tripropylene glycol diacrylate, a 1,9-nonanediol diacrylate, a tricyclodecane dimethanol diacrylate, a cyclic trimethylolpropane formal acrylate, a diethylene glycol diacrylate, an EO-modified diglycerol tetraacrylate, and the like as a cross-linking component. In addition, as a cationic polymerization-curable adhesive, a compound having an epoxy group, an oxetanyl group can also be used. The compound having an epoxy group is not particularly limited as long as it is a compound having at least two epoxy groups in the molecule, and various curable epoxy compounds generally known can be used. The above-mentioned adhesive can also contain a suitable additive as needed. As the above-mentioned additive, for example, a coupling agent such as a silane coupling agent, a titanium coupling agent, an adhesion promoter such as an oxirane, an ultraviolet absorber, a deterioration preventive agent, a dye, a processing aid, an ion capturing agent, an antioxidant, a tackifier, a filler, a plasticizer, a leveling agent, a foaming inhibitor, an antistatic agent, a heat-resistant stabilizer, a hydrolysis-resistant stabilizer, and the like can be mentioned.

[0099] The above-mentioned adhesive can also contain a suitable additive as needed. As the above-mentioned additive, for example, a coupling agent such as a silane coupling agent, a titanium coupling agent, an adhesion promoter such as an oxirane, an ultraviolet absorber, a deterioration preventive agent, a dye, a processing aid, an ion capturing agent, an antioxidant, a tackifier, a filler, a plasticizer, a leveling agent, a foaming inhibitor, an antistatic agent, a heat-resistant stabilizer, a hydrolysis-resistant stabilizer, and the like can be mentioned.

[0100] The coating of the above-mentioned adhesive can be performed on either side of the above-mentioned film side (or the above-mentioned functional layer side), the above-mentioned polarizing film side, or both sides. After the lamination, a drying process is performed to form an adhesive layer made of the coated and dried layer. After the above-mentioned drying process, ultraviolet rays, electron beams can be irradiated as needed. The thickness of the above-mentioned adhesive layer is not particularly limited, and in the case of using a water-based adhesive and the like, it is preferably around 30 to 5000 nm, more preferably around 100 to 1000 nm, and in the case of using an ultraviolet-curable adhesive, an electron beam-curable adhesive, and the like, it is preferably around 0.1 to 100 μm, more preferably around 0.5 to 10 μm.

[0101] The aforementioned transparent protective film and the aforementioned polarizing film, or the aforementioned polarizing film and the aforementioned functional layer, can be stacked together with interlayers such as surface modification treatment layer, easy-to-adhere layer, blocking layer, and refractive index adjustment layer.

[0102] Examples of surface modification treatments for forming the above-mentioned surface modified layer include: corona treatment, plasma treatment, primer treatment, saponification treatment, etc.

[0103] Examples of easy-adhesive agents used to form the aforementioned easy-adhesive layer include: resins comprising various resins having a polyester backbone, polyether backbone, polycarbonate backbone, polyurethane backbone, silicone backbone, polyamide backbone, polyimide backbone, polyvinyl alcohol backbone, etc. The aforementioned easy-adhesive layer can typically be pre-formed on the aforementioned film, and the easy-adhesive layer side of the film is laminated to the polarizing film via the aforementioned adhesive layer or adhesive layer.

[0104] The aforementioned barrier layer is a layer that functions to prevent impurities such as oligomers and ions dissolved from the aforementioned film from migrating (invading) into the polarizing film. The barrier layer can be any transparent layer that can prevent impurities dissolved from the aforementioned film, etc. Examples of materials forming the barrier layer include: urethane prepolymer forming materials, cyanoacrylate forming materials, epoxy forming materials, etc.

[0105] The aforementioned refractive index adjustment layer is provided to suppress the decrease in transmittance caused by reflection between layers with different refractive indices, such as the aforementioned film and the polarizing film. Examples of refractive index adjustment materials forming the aforementioned refractive index adjustment layer include forming materials comprising various resins and additives such as silica-based, acrylic-based, acrylic-styrene-based, and melamine-based resins.

[0106] The polarization degree of the above-mentioned polarizing film is preferably 99.98% or higher, and more preferably 99.99% or higher.

[0107] An adhesive layer for bonding other components can be provided on one or both sides of the aforementioned polarizing film. Preferably, an adhesive layer is used as this adhesive layer. There are no particular limitations on the adhesive used to form this adhesive layer; adhesives with polymers such as acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyethers, fluorinated polymers, and rubbers as the base polymer can be suitably selected. Adhesives containing acrylic polymers, exhibiting excellent optical transparency, moderate wetting, cohesiveness, and adhesion, as well as excellent weather resistance and heat resistance, are particularly preferred.

[0108] The adhesive layer can be provided to one or both sides of the polarizing film by a suitable method. As a method of providing the adhesive layer, for example, a method in which an adhesive solution is prepared and provided directly on the polarizing film by a suitable spreading method such as a flow casting method or a coating method, or a method in which an adhesive layer is formed on a separator and transferred to the polarizing film, or the like can be given. The thickness of the adhesive layer can be suitably determined depending on the purpose of use, adhesive strength, and the like, and is generally 1 to 500 μm, preferably 5 to 200 μm, and more preferably 10 to 100 μm. A material in which the adhesive layer is provided to at least one side of the polarizing film as described above is also referred to as a polarizing film with an adhesive layer.

[0109] The exposed surface of the adhesive layer is preferably temporarily bonded with a separator to cover it for the purpose of preventing contamination thereof or the like during a period until it is used in practice. Thus, contamination of the adhesive layer in a usual handling state or the like can be prevented. As the separator, a separator or the like obtained by coating a suitable thin layer such as a plastic film, a rubber sheet, paper, cloth, nonwoven fabric, mesh, foamed sheet, metal foil, a laminate thereof, or the like with a suitable release agent such as a silicone-based, long-chain alkyl-based, fluorine-based, molybdenum sulfide-based, or the like, as needed, can be used.

[0110] Example

[0111] Hereinafter, the present application will be described in more detail by citing examples, but the present application is not limited to only these examples.

[0112] Example 1

[0113] Production of Polarizing Film and Polarizing Film

[0114] As the thermoplastic resin substrate, a 100 μm thick poly(ethylene terephthalate) (IPA) copolymer PET film was used. One side of the substrate was corona-treated, and an aqueous solution containing polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetyl-modified PVA (degree of polymerization 1200, acetyl-modification rate 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 coated onto the corona-treated surface at 25°C and dried to form a PVA-based resin layer, thus producing a laminate. The resulting laminate was stretched at 140°C in a gas atmosphere at 4.5 times its length (stretching treatment). Next, the laminate was immersed in a staining bath (an aqueous solution of 1.0 wt% iodine and 7.0 wt% potassium iodide) at 25°C for 12 seconds for staining (staining treatment). Then, it was immersed in a crosslinking bath (an aqueous solution of 1.0 wt% boron, 1.0 wt% potassium iodide, and 5.0 wt% of the compound represented by the following general formula (9)) at 60°C for 21 seconds (crosslinking treatment). Next, the laminate was immersed in a washing bath (an aqueous solution of 4.5 wt% potassium iodide) at 25°C for 10 seconds (washing treatment). Finally, the laminate was dried in an oven at 60°C for 21 seconds (drying treatment) to obtain a laminate with a PVA-type resin layer (polarizing film) of 1.2 μm thickness. Next, a linear polarization separator (manufactured by 3M, trade name "DBEF") was attached to the polarization film side of the laminate with a PVA resin layer (polarization film) through a 20 μm thick acrylic adhesive layer. The thermoplastic resin substrate was then peeled off, and a 20 μm thick acrylic adhesive layer was applied to the peeled surface to create a polarization film with a monomer transmittance of 39.7%.

[0115] [Chemical Formula 9]

[0116]

[0117] [Method for determining the iodine content (wt%) in polarizing film]

[0118] For the polarizing film, the iodine concentration (wt%) was determined using a fluorescence X-ray analysis device (manufactured by Rigaku Corporation, trade name "ZSX-PRIMUSIV", measurement diameter: φ20mm) and the following formula.

[0119] Iodine concentration (wt%) = 14.474 × (fluorescent X-ray intensity) / (film thickness) (kcps / μm)

[0120] Note that the coefficient at the time of calculating the concentration differs depending on the measuring apparatus, and the coefficient can be found using an appropriate calibration curve. The results are shown in Table 1.

[0121] [Gas production analysis method]

[0122] A polarizing film was introduced into a heating furnace type pyrolyzer (Frontier Lab, PY-2020iD), and the generated gas was directly introduced into a TOFMS (JEOL, JMS-T100GCV), and gas production analysis (EGA / TOFMS) was performed. The results are shown in Table 1.

[0123] [Measurement conditions]

[0124] Temperature rising conditions: 40°C→ +10°C / min→ 350°C

[0125] Interface: deactivated fused silica tube, 2.5 m x 0.15 mm id

[0126] Carrier gas: He (1.0 mL / min)

[0127] Injection port temperature: 300°C

[0128] Injection port: split ratio 20:1

[0129] Interface temperature: 300°C

[0130] Mass spectrometer: TOFMS

[0131] Ionization method: EI method

[0132] Mass range: m / z = 18

[0133] [Method for measuring the content (wt%) of a radical trapping agent in a polarizing film]

[0134] About 20 mg of a polarizing film was taken, and quantification was performed after heating and dissolving in 1 mL of water, followed by dilution with methanol 4.5 mL, and the obtained extract was filtered with a membrane filter, and the concentration of the radical trapping agent was measured using HPLC (Waters, ACQUITY UPLC H-class Bio). The results are shown in Table 1.

[0135] [Evaluation of the polarization degree]

[0136] The degree of polarization of a polarizing film can be measured using a spectrophotometer (Japanese Spectrophotometer, product name "V7100"). Specifically, the degree of polarization can be measured by determining the parallel transmittance (H0) and orthogonal transmittance (H90) of the polarizing film and then calculating using the formula: Degree of polarization (%) = {(H0 - H90) / (H0 + H90)}¹ / ² × 100. The parallel transmittance (H0) is the transmittance value of a parallel-type stacked polarizing film manufactured by stacking two identical polarizing films with their absorption axes parallel. Similarly, the orthogonal transmittance (H90) is the transmittance value of an orthogonal-type stacked polarizing film manufactured by stacking two identical polarizing films with their absorption axes orthogonal. It should be noted that these transmittance values ​​are Y values ​​obtained by correcting for visibility using a 2-degree field of view (C light source) according to JlS Z 8701-1982. The results are shown in Table 1.

[0137] [Evaluation of monomer transmittance in high-temperature environments]

[0138] The polarizing film obtained above was cut into 5.0 × 4.5 cm pieces with the absorption axis parallel to the long side. A 1.3 mm alkali-free glass plate was then bonded to the adhesive layer of the polarizing film to create a laminate. The laminate was then placed in a hot air oven at 105 °C for 96 hours, and the single-cell transmittance (ΔTs) before and after heating was measured. The single-cell transmittance was measured using a spectrophotometer (Japanese Spectrophotometer, product name "V7100") and evaluated based on the following criteria. It should be noted that the measurement wavelength was 380–700 nm (in 5 nm intervals), and the results are shown in Table 1.

[0139] ΔTs(%)=Ts 96 -Ts0

[0140] Here, Ts0 is the monomer transmittance of the laminate before heating, and Ts 96 The transmittance of the laminate after heating for 96 hours is the monomer transmittance. Preferably, ΔTs(%) is 5 ≥ ΔTs(%) ≥ 0, more preferably 3 ≥ ΔTs(%) ≥ 0.

[0141] <Example 2>

[0142] In the above-described fabrication of polarizing and polarizing films, the crosslinking bath was changed to an aqueous solution containing 1.0 wt% boron, 1.0 wt% potassium iodide, and 10.0 wt% of the compound represented by the above general formula (9). Otherwise, the polarizing and polarizing films were fabricated using the same procedures as in Example 1. The results of the above-described measurements and evaluations of the polarizing and polarizing films are shown in Table 1.

[0143] <Example 3>

[0144] In the above-mentioned "Manufacture of polarizing film and polarizing film", the cross-linking bath was changed to a cross-linking bath (an aqueous solution in which the concentration of boron was 1.0% by weight, the concentration of potassium iodide was 1.0% by weight, and the concentration of the compound represented by the above general formula (8) was 10.0% by weight), and otherwise, the polarizing film and the polarizing film were manufactured by the same operation as in Example 1. The results of the measurement and the evaluation based on the above-mentioned of the polarizing film and the polarizing film are shown in Table 1.

[0145] <Example 4>

[0146] In the above-mentioned "Manufacture of polarizing film and polarizing film", the cross-linking bath was changed to a cross-linking bath (an aqueous solution in which the concentration of boron was 1.0% by weight, the concentration of potassium iodide was 1.0% by weight, and the concentration of the compound represented by the above general formula (7) was 10.0% by weight), and otherwise, the polarizing film and the polarizing film were manufactured by the same operation as in Example 1. The results of the measurement and the evaluation based on the above-mentioned of the polarizing film and the polarizing film are shown in Table 1.

[0147] <Example 5>

[0148] In the above-mentioned "Manufacture of polarizing film and polarizing film", the PVA-based resin layer was formed in such a manner that the thickness of the finally obtained polarizing film became 4.8 μm, and otherwise, the polarizing film and the polarizing film were manufactured by the same operation as in Example 1. The results of the measurement and the evaluation based on the above-mentioned of the polarizing film and the polarizing film are shown in Table 1.

[0149] <Example 6>

[0150] In the above-mentioned "Manufacture of polarizing film and polarizing film", the dyeing bath was changed to a dyeing bath (an aqueous solution in which the concentration of iodine was 0.7% by weight and the concentration of potassium iodide was 4.9% by weight), the cross-linking bath was changed to a cross-linking bath (an aqueous solution in which the concentration of boron was 1.0% by weight, the concentration of potassium iodide was 1.0% by weight, and the concentration of the compound represented by the above general formula (9) was 10.0% by weight), and otherwise, the polarizing film and the polarizing film were manufactured by the same operation as in Example 1. The results of the measurement and the evaluation based on the above-mentioned of the polarizing film and the polarizing film are shown in Table 1.

[0151] <Example 7>

[0152] In the above-described "Production of a polarizing film and a polarizing film", the PVA-based resin layer was formed so that the thickness of the finally obtained polarizing film would be 2.5 μm, and a laminate was produced. The dyeing bath was changed to a dyeing bath (an aqueous solution having an iodine concentration of 0.5% by weight and a potassium iodide concentration of 3.5% by weight), the cross-linking bath was changed to a cross-linking bath (an aqueous solution having a boron concentration of 1.0% by weight, a potassium iodide concentration of 1.0% by weight, and a concentration of the compound represented by the above general formula (9) of 10.0% by weight), and a polarizing film and a polarizing film were produced by the same operations as in Example 1, except for this. The results of the measurement and evaluation based on the above of the polarizing film and the polarizing film are shown in Table 1.

[0153] Example 8

[0154] In the above-described "Production of a polarizing film and a polarizing film", the PVA-based resin layer was formed so that the thickness of the finally obtained polarizing film would be 4.8 μm, and a laminate was produced. The dyeing bath was changed to a dyeing bath (an aqueous solution having an iodine concentration of 0.5% by weight and a potassium iodide concentration of 3.5% by weight), the cross-linking bath was changed to a cross-linking bath (an aqueous solution having a boron concentration of 1.0% by weight, a potassium iodide concentration of 1.0% by weight, and a concentration of the compound represented by the above general formula (9) of 10.0% by weight), and a polarizing film and a polarizing film were produced by the same operations as in Example 1, except for this. The results of the measurement and evaluation based on the above of the polarizing film and the polarizing film are shown in Table 1.

[0155] Comparative Example 1

[0156] In the above-described "Production of a polarizing film and a polarizing film", the cross-linking bath was changed to a cross-linking bath (an aqueous solution having a boron concentration of 1.0% by weight and a potassium iodide concentration of 1.0% by weight), and a polarizing film and a polarizing film were produced by the same operations as in Example 1, except for this. The results of the measurement and evaluation based on the above of the polarizing film and the polarizing film are shown in Table 1.

[0157] Comparative Example 2

[0158] In the above-described "Production of a polarizing film and a polarizing film", the dyeing bath was changed to a dyeing bath (an aqueous solution having an iodine concentration of 0.5% by weight and a potassium iodide concentration of 3.5% by weight), the cross-linking bath was changed to a cross-linking bath (an aqueous solution having a boron concentration of 1.0% by weight, a potassium iodide concentration of 1.0% by weight, and a concentration of the compound represented by the above general formula (9) of 10.0% by weight), and a polarizing film and a polarizing film were produced by the same operations as in Example 1, except for this. The results of the measurement and evaluation based on the above of the polarizing film and the polarizing film are shown in Table 1.

[0159] Comparative Example 3

[0160] In the above-mentioned "manufacture of polarizing film and polarizing film", after the linear polarizing light separating film (3M Co., Ltd., trade name "DBEF") was attached to the polarizing film side of the laminate having the PVA-based resin layer (polarizing film) with the thickness of 20 μm of the acrylic-based adhesive layer interposed therebetween, the thermoplastic resin substrate was peeled off, the treatment liquid (aqueous solution of sodium bicarbonate 0.5% by weight and isopropyl alcohol 50% by weight: pH 6.0) was applied on the peeled surface using a wire bar coater, and after drying at 50°C for 60 seconds, the polarizing film was manufactured by applying the acrylic-based adhesive layer having the thickness of 20 μm. Other than this, the polarizing film and the polarizing film were manufactured by the same operation as in Example 1. The results of the measurement and evaluation based on the above-mentioned of the polarizing film and the polarizing film are shown in Table 1.

[0161] <Comparative Example 4>

[0162] In the above-mentioned "manufacture of polarizing film and polarizing film", the dyeing bath was changed to a dyeing bath (aqueous solution of potassium iodide concentration 15.0% by weight and sulfuric acid n hydrate 2.0% by weight), and other than this, the polarizing film and the polarizing film were manufactured by the same operation as in Example 1. The results of the measurement and evaluation based on the above-mentioned of the polarizing film and the polarizing film are shown in Table 1.

[0163]

[0164] The polarizing film in which the content of iodine exceeds 10% by weight, the monomer transmittance is 41% or less, and the peak temperature of the maximum intensity of water in the gas production analysis is 175°C or more has an excellent effect of suppressing the decrease in monomer transmittance due to coloring of the polarizing film in a high-temperature environment in the Examples.

[0165] On the other hand, the peak temperature of the maximum intensity of water in the gas production analysis of the polarizing film of Comparative Example 1 was 173°C, and thus the effect of suppressing the decrease in monomer transmittance due to coloring of the polarizing film in a high-temperature environment was poor. In addition, the monomer transmittance of the polarizing film of Comparative Example 2 was 41.5%, and thus the criterion of the monomer transmittance of the present application was not satisfied. Furthermore, Comparative Examples 3 and 4 correspond to the polarizing films disclosed in the prior art documents Patent Documents 1 and 2, and the peak temperature of the maximum intensity of water in the gas production analysis was less than 175°C, and thus the effect of suppressing the decrease in monomer transmittance due to coloring of the polarizing film in a high-temperature environment was poor.

Claims

1. A polarizing film formed by adsorbing iodine to a polyvinyl alcohol-based film and orienting the same, wherein the content of iodine in the polarizing film exceeds 10% by weight, the monochromatic transmittance is 41% or less, the polarizing film contains a radical trapping agent, the content of the radical trapping agent has a weight ratio to the content of iodine (content of radical trapping agent / content of iodine) of 0.01 or more, and in a gas generation analysis, the peak temperature of the maximum intensity of water detected in the presence of an inert gas at a temperature increase rate of 10°C / min and a temperature increase range of 40°C to 350°C is 175°C or more.

2. The polarizing film according to claim 1, having a thickness of 10 μm or less.

3. The polarizing film according to claim 1 or 2, wherein the radical trapping agent is a compound having a nitroxyl radical or a nitroxyl group.

4. A polarizing film in which a transparent protective film or an optical functional film is attached to at least one side of the polarizing film according to any one of claims 1 to 3.

5. The polarizing film according to claim 4, having a degree of polarization of 99.98% or more. ​ ​ ​ ​ ​

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