Polarizing film, laminated polarizing film, image display panel, and image display device

Abstract

To provide a highly light-resistant polarizing film.SOLUTION: A polarizing film product constituting an image display panel is provided, the polarizing film product comprising a polarizing film, a functional layer, an adhesive layer, and a first transparent protective film. The functional layer is disposed next to the polarizing film on the viewing side and contains a water-soluble radical scavenger, and the first transparent protective film is provided on the functional layer with the adhesive layer in between.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polarizing film, a laminated polarizing film, an image display panel, and an image display device. [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] The polarizing film is used as a laminated polarizing film (optical laminate) by laminating other optical layers as necessary, and the polarizing film or the laminated polarizing film (optical laminate) is used as an image display panel bonded to an image display cell such as a liquid crystal cell or an organic EL element. Furthermore, the image display panel is bonded to a front transparent plate (window layer) on the viewing side or a front transparent member such as a touch panel via a pressure-sensitive adhesive layer or an adhesive layer, and used as the various image display devices mentioned above (Patent Document 1).

[0004] In recent years, the applications of such various image display devices have expanded, for example, to include use in mobile devices such as mobile phones and tablet terminals, as well as in-vehicle image display devices such as car navigation devices and rear monitors. Accordingly, the polarizing films and laminated polarizing films are required to have higher durability in harsher environments (for example, high-temperature environments) than has been conventionally required, and polarizing films and image display devices intended to ensure such durability have been proposed (Patent Documents 2-3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-102353 [Patent Document 2] Special Publication No. 2012-516468 [Patent Document 3] Japanese Patent Application Publication No. 2018-101117 Summary of the Invention [Problem to be solved by the invention]

[0006] In the case of the above-mentioned in-vehicle image display devices, the display designs have become increasingly irregular and larger due to the recent advancement of autonomous driving technology. Along with these changes in display design, there is a demand for polarizing films with excellent performance (light resistance) against external light (especially ultraviolet light and the short wavelength region of visible light).

[0007] In view of the above circumstances, an object of the present invention is to provide a polarizing film having excellent light resistance.

[0008] Another object of the present invention is to provide a laminated polarizing film, an image display panel, and an image display device using the above polarizing film. [Means for solving the problem]

[0009] That is, the present invention relates to a polarizing film constituting an image display panel, the polarizing film having a polarizing film, a functional layer, an adhesive layer, and a first transparent protective film, the functional layer being adjacent to the viewing side of the polarizing film and containing a water-soluble radical scavenger, and the first transparent protective film being provided on the functional layer via an adhesive layer.

[0010] The present invention also relates to a laminated polarizing film in which the polarizing film is bonded to an optical layer.

[0011] The present invention also relates to an image display panel in which the side opposite to the viewing side of the polarizing film of the polarizing film or the side opposite to the viewing side of the polarizing film of the laminated polarizing film is attached to an image display cell.

[0012] The present invention also relates to an image display device comprising a front transparent member on the polarizing film or laminated polarizing film side of the image display panel. [Effects of the Invention]

[0013] Although the mechanism of action of the polarizing film of the present invention is not fully understood, it is presumed as follows: However, the present invention is not limited to this mechanism.

[0014] The polarizing film of the present invention is a polarizing film constituting an image display panel. The polarizing film comprises a polarizing film, a functional layer, an adhesive layer, and a first transparent protective film. The functional layer is adjacent to the viewing side of the polarizing film and contains a water-soluble radical scavenger. The first transparent protective film is attached to the functional layer via the adhesive layer. Generally, external light (ultraviolet light or short-wavelength visible light) irradiated onto an image display panel penetrates the viewing side (viewing surface) of the polarizing film. It is believed that degradation of the polarizing film from the viewing side (viewing surface) due to light energy causes a decrease in the single-unit transmittance (polyenization). In contrast, the polarizing film of the present invention has a water-soluble radical scavenger in the functional layer adjacent to the viewing side of the polarizing film. This water-soluble radical scavenger easily migrates to water in the polarizing film and can capture radicals that may be generated by the progression of polyenization. This effectively suppresses a decrease in the single-unit transmittance from the viewing side of the polarizing film, resulting in excellent light resistance. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic cross-sectional view showing one embodiment of a polarizing film. [Figure 2] FIG. 1 is a schematic cross-sectional view showing one embodiment of a polarizing film. [Figure 3]1 is a schematic cross-sectional view showing an embodiment of an image display panel and an image display device. DETAILED DESCRIPTION OF THE INVENTION

[0016] Fig. 1 is a schematic cross-sectional view showing one embodiment of the polarizing film of the present invention. Fig. 1 shows one embodiment of polarizing film 10 in which functional layer 12 is adjacent to the viewing side of polarizing film 11, and first transparent protective film 13 is provided on functional layer 12 via adhesive layer 20.

[0017] Fig. 2 is a schematic cross-sectional view showing one embodiment of the polarizing film of the present invention. Fig. 2 shows one embodiment of polarizing film 10 in which functional layer 12 is adjacent to the viewing side of polarizing film 11, first transparent protective film 13 is provided on functional layer 12 via adhesive layer 20, and second transparent protective film 14 is provided on the side opposite the viewing side of polarizing film 11 via a pressure-sensitive adhesive layer or adhesive layer 30.

[0018] Fig. 3 is a schematic cross-sectional view showing one embodiment of the image display panel and image display device of the present invention. Fig. 3 shows one embodiment of an image display panel 100 in which the side opposite the viewing side of the polarizing film of a polarizing film 10 is bonded to an image display cell 90 via a pressure-sensitive adhesive layer or adhesive layer 50. Fig. 3 also shows one embodiment of an image display device 200 in which a front transparent member 80 is provided on the polarizing film side of the image display panel 100 via a pressure-sensitive adhesive layer or adhesive layer 40.

[0019] <Polarizing film> The polarizing film of the present invention is a polarizing film constituting an image display panel, the polarizing film having a polarizing film, a functional layer, an adhesive layer, and a first transparent protective film, the functional layer being adjacent to the viewing side of the polarizing film and containing a water-soluble radical scavenger, and the first transparent protective film being provided on the functional layer via an adhesive layer. The polarizing film constituting the image display panel refers to an image display panel in which the side opposite the viewing side (viewing surface) of the polarizing film of the polarizing film, or the side opposite the viewing side (viewing surface) of the polarizing film of a laminated polarizing film having the polarizing film, is bonded to an image display cell, as described below. The viewing side (viewing surface) of the polarizing film refers to the viewing side of the image display panel.

[0020] <Polarizing film> The polarizing film of the present invention is formed by adsorbing and aligning a dichroic substance such as iodine or a dichroic dye on a polyvinyl alcohol film. From the viewpoint of the initial polarization performance of the polarizing film, iodine is preferred as the dichroic substance.

[0021] The polyvinyl alcohol (PVA) film can be used without any particular limitation as long as it is transparent in the visible light region and disperses and adsorbs dichroic substances such as iodine and dichroic dyes. In addition, the PVA film typically used as a raw sheet preferably has a thickness of about 1 to 100 μm, more preferably about 1 to 50 μm, and a width of about 100 to 5000 mm.

[0022] Examples of materials for the polyvinyl alcohol-based film include polyvinyl alcohol or 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.

[0023] 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.

[0024] The polarizing film can be produced, for example, by dyeing the polyvinyl alcohol-based film by immersing it in an aqueous solution of a dichroic substance such as iodine or a dichroic dye, and then stretching the film to 3 to 7 times its original length. If necessary, the film can also be immersed in an aqueous solution of boric acid, potassium iodide, or the like. Furthermore, if necessary, the polyvinyl alcohol-based film may be immersed in water and washed before dyeing. Washing the polyvinyl alcohol-based film with water not only removes dirt and antiblocking agents from the surface of the polyvinyl alcohol-based film, but also swells the polyvinyl alcohol-based film, thereby preventing unevenness such as uneven dyeing. Stretching may be performed after dyeing with iodine, or may be performed while dyeing, or may be performed after stretching and then dyeing with iodine. Stretching may be performed in an aqueous solution of boric acid, potassium iodide, or the like, or in a water bath.

[0025] The polarizing film preferably has a thickness of 1 μm or more, more preferably 2 μm or more, from the viewpoint of improving the initial polarization degree of the polarizing film, and preferably has a thickness of 15 μm or less, more preferably 10 μm or less, and even more preferably 8 μm or less, from the viewpoint of preventing warping of the panel. In particular, to obtain a polarizing film having a thickness of about 8 μm or less, the following method for producing a thin polarizing film can be applied, in which the polyvinyl alcohol-based film is a laminate including a polyvinyl alcohol-based resin layer formed on a thermoplastic resin substrate.

[0026] <Method for manufacturing thin polarizing film> A method for producing a thin polarizing film includes 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 thermoplastic resin substrate to form a laminate, and subjecting the laminate to an in-air auxiliary stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment, in that order. In particular, to obtain a polarizing film with excellent optical properties, a two-stage stretching method is selected, which combines an in-air auxiliary stretching treatment (dry stretching) with an underwater stretching treatment in a boric acid aqueous solution.

[0027] The laminate may be produced by any suitable method, for example, by applying a coating liquid containing the PVA resin to the surface of the thermoplastic resin substrate and drying the coating liquid. 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 resin layer is preferably about 3 to 40 μm, more preferably about 3 to 20 μm.

[0028] The thermoplastic resin substrate preferably has a water absorption rate of about 0.2% or more, more preferably about 0.3% or more, from the viewpoint of absorbing water to significantly reduce the stretching stress and enabling high stretching ratios. On the other hand, the thermoplastic resin substrate preferably has a water absorption rate of about 3% or less, more preferably about 1% or less, from the viewpoint of preventing defects such as a significant decrease in the dimensional stability of the thermoplastic resin substrate and a deterioration in the appearance of the resulting polarizing film. The water absorption rate can be adjusted, for example, by introducing a modifying group into the constituent material of the thermoplastic resin substrate. The water absorption rate is a value determined in accordance with JIS K 7209.

[0029] The thermoplastic resin substrate preferably has a glass transition temperature (Tg) of about 120°C or less, from the viewpoint of ensuring sufficient stretchability of the laminate while suppressing crystallization of the PVA-based resin layer. Furthermore, considering the plasticization of the thermoplastic resin substrate with water and the smooth underwater stretching, the glass transition temperature (Tg) is more preferably about 100°C or less, and even more preferably about 90°C or less. On the other hand, the glass transition temperature of the thermoplastic resin substrate is preferably about 60°C or more, from the viewpoint of preventing problems such as deformation of the thermoplastic resin substrate during application and drying of the coating liquid and producing a good laminate. The glass transition temperature can be adjusted, for example, by introducing a modifying group into the constituent material of the thermoplastic resin substrate or by heating using a crystallizing material. The glass transition temperature (Tg) is a value determined in accordance with JIS K 7121.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] The coating solution preferably contains a halide to improve the orientation of polyvinyl alcohol molecules during stretching. Any appropriate halide can 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, and more preferably about 10 to 15 parts by weight, per 100 parts by weight of the PVA resin.

[0034] The coating liquid may contain additives, such as plasticizers such as ethylene glycol and glycerin, and surfactants such as nonionic surfactants.

[0035] The coating liquid may be applied by any suitable method, such as roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, knife coating (comma coating, etc.), etc. The drying temperature of the coating liquid is preferably about 50° C. or higher.

[0036] The in-air auxiliary stretching treatment can stretch the laminate at a high stretching ratio while suppressing crystallization of the thermoplastic resin substrate. The stretching method in the in-air auxiliary stretching treatment may be fixed-end stretching (e.g., a method of stretching using a tenter stretching machine) or free-end stretching (e.g., a method of uniaxially stretching the laminate by passing it between rolls with different peripheral speeds). However, free-end stretching is preferred from the viewpoint of obtaining high optical properties.

[0037] The stretching ratio in the auxiliary in-air stretching is preferably about 2 to 3.5. The auxiliary in-air stretching may be carried out in one stage or in multiple stages. When carried out in multiple stages, the stretching ratio is the product of the stretching ratios in each stage.

[0038] The stretching temperature in the auxiliary in-air stretching can be set to any appropriate value depending on the material forming the thermoplastic resin substrate, the stretching method, etc., and is, for example, preferably equal to or higher than the glass transition temperature (Tg) of the thermoplastic resin substrate, more preferably equal to or higher than the glass transition temperature (Tg) + 10° C., and even more preferably equal to or higher than the glass transition temperature (Tg) + 15° C. On the other hand, the upper limit of the stretching temperature is preferably about 170° C., from the viewpoint of suppressing rapid crystallization of the PVA-based resin and suppressing defects due to crystallization (for example, preventing the orientation of the PVA-based resin layer due to stretching).

[0039] If necessary, an insolubilization treatment may be carried out after the auxiliary air-stretching treatment and before the dyeing treatment or the underwater stretching treatment. The insolubilization treatment is typically carried out by immersing the PVA-based resin layer in an aqueous boric acid solution. The insolubilization treatment imparts water resistance to the PVA-based resin layer, and prevents a decrease in the orientation of PVA when immersed in water. The concentration of the aqueous boric acid solution is preferably about 1 to 5 parts by weight per 100 parts by weight of water. The liquid temperature of the insolubilization bath is preferably about 20 to 50°C.

[0040] The dyeing treatment is carried out by dyeing the PVA-based resin layer with iodine. Examples of the adsorption method include a method of immersing the PVA-based resin layer (laminate) in a dyeing solution containing iodine, a method of applying the dyeing solution to the PVA-based resin layer, and a method of spraying the dyeing solution onto the PVA-based resin layer, and the method of immersing the PVA-based resin layer (laminate) in a dyeing solution containing iodine is preferred.

[0041] The amount of iodine in the dye bath is preferably about 0.05 to 0.5 parts by weight per 100 parts by weight of water. To increase the solubility of iodine in water, the iodide is preferably added to the iodine aqueous solution. The amount of iodide is preferably about 0.1 to 10 parts by weight, more preferably about 0.3 to 5 parts by weight, per 100 parts by weight of water. The temperature of the dye bath is preferably about 20 to 50°C to suppress dissolution of the PVA-based resin. The immersion time is preferably about 5 seconds to 5 minutes, more preferably about 30 to 90 seconds, from the viewpoint of ensuring the transmittance of the PVA-based resin layer. To obtain a polarizing film with good optical properties, the ratio of the iodine content to the iodide content in the iodine aqueous solution is preferably about 1:5 to 1:20, more preferably about 1:5 to 1:10.

[0042] If necessary, a crosslinking treatment may be performed after the dyeing treatment and before the underwater stretching treatment. The crosslinking treatment is typically performed by immersing the PVA-based resin layer in an aqueous boric acid solution. The crosslinking treatment imparts water resistance to the PVA-based resin layer, thereby preventing a decrease in the orientation of the PVA when the layer is immersed in high-temperature water during the subsequent underwater stretching treatment. The boric acid concentration of the aqueous boric acid solution is preferably about 1 to 5 parts by weight per 100 parts by weight of water. Furthermore, when performing the crosslinking treatment, it is preferable to further incorporate the iodide into the crosslinking bath used in the crosslinking treatment. The incorporation of the iodide can suppress the elution of iodine adsorbed to the PVA-based resin layer. The amount of the iodide incorporated is preferably about 1 to 5 parts by weight per 100 parts by weight of water. The liquid temperature of the crosslinking bath (boric acid aqueous solution) is preferably about 20 to 50°C.

[0043] The underwater stretching treatment is carried out by immersing the laminate in a stretching bath. Underwater stretching allows stretching at a temperature lower than the glass transition temperature (typically about 80°C) of the thermoplastic resin substrate or the PVA-based resin layer, allowing the PVA-based resin layer to be stretched at a high magnification while suppressing crystallization. The underwater stretching method may be fixed-end stretching (e.g., stretching using a tenter stretching machine) or free-end stretching (e.g., uniaxial stretching by passing the laminate between rolls with different peripheral speeds). However, free-end stretching is preferred from the viewpoint of obtaining high optical properties.

[0044] The underwater stretching treatment is preferably carried out by immersing the laminate in an aqueous boric acid solution (stretching in boric acid solution). By using an aqueous boric acid solution as a stretching bath, it is possible to impart to the PVA resin layer rigidity sufficient to withstand the tension applied during stretching and water resistance sufficient to prevent dissolution in water. The boric acid concentration in the aqueous boric acid solution is preferably 1 to 10 parts by weight, more preferably 2.5 to 6 parts by weight, per 100 parts by weight of water. In addition, an iodide may be blended into the stretching bath (aqueous boric acid solution). The liquid temperature of the stretching bath is preferably about 40 to 85°C, more preferably about 60 to 75°C. The immersion time of the laminate in the stretching bath is preferably about 15 seconds to 5 minutes.

[0045] The stretching ratio in the underwater stretching is preferably about 1.5 times or more, and more preferably about 3 times or more.

[0046] The total stretching ratio of the laminate is preferably about 5 times or more, more preferably about 5.5 times or more, relative to the original length of the laminate.

[0047] The drying shrinkage treatment may be performed by zone heating, in which the entire zone is heated, or by heating the transport rolls (using so-called heated rolls), but preferably both are used. Drying using heated rolls efficiently suppresses heat curling of the laminate, making it possible to produce a polarizing film with excellent appearance. Furthermore, since the laminate can be dried while being maintained flat, it is possible to suppress not only curling but also wrinkles. Furthermore, from the viewpoint of improving the optical properties of the resulting polarizing film by shrinking the laminate in the width direction during the drying shrinkage treatment, the shrinkage rate of the laminate in the width direction due to the drying shrinkage treatment is preferably about 1 to 10%, more preferably about 2 to 8%.

[0048] Drying conditions can be controlled by adjusting the heating temperature of the transport rolls (heating roll temperature), the number of heating rolls, the contact time with the heating rolls, etc. The temperature of the heating rolls is preferably about 60 to 120°C, more preferably about 65 to 100°C, and even more preferably 70 to 80°C. From the viewpoint of satisfactorily increasing the crystallinity of the thermoplastic resin and satisfactorily suppressing curling, the number of transport rolls is usually about 2 to 40, preferably about 4 to 30. The contact time between the laminate and the heating rolls (total contact time) is preferably about 1 to 300 seconds, more preferably 1 to 20 seconds, and even more preferably 1 to 10 seconds.

[0049] The heating rolls may be installed in a heating furnace or in a normal production line (under room temperature). Preferably, they are installed in a heating furnace equipped with a blower. By using both heating roll drying and hot air drying, it is possible to suppress abrupt temperature changes between the heating rolls, and to easily control shrinkage in the width direction. The hot air drying temperature is preferably about 30 to 100°C. The hot air drying time is preferably about 1 to 300 seconds.

[0050] After the underwater stretching treatment and before the drying shrinkage treatment, it is preferable to carry out a washing treatment, typically by immersing the PVA-based resin layer in an aqueous potassium iodide solution.

[0051] Each treatment bath in the dyeing process, the underwater stretching process, the insolubilization process, the crosslinking process, and the washing process 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.

[0052] <Functional layer> The functional layer of the present invention is adjacent to the viewing side of the polarizing film and contains a water-soluble radical scavenger.

[0053] From the viewpoint of ease of migration into the moisture in the polarizing film, the water-soluble radical scavenger is preferably a compound that can be dissolved in an amount of 1 part by weight or more in 100 parts by weight of water at 25° C., more preferably a compound that can be dissolved in an amount of 2 parts by weight or more in 100 parts by weight of water at 25° C., and even more preferably a compound that can be dissolved in an amount of 5 parts by weight or more in 100 parts by weight of water at 25° C. The water-soluble radical scavengers may be used alone or in combination of two or more kinds.

[0054] The water-soluble radical scavenger is presumed to be capable of suppressing the polyenization of the polarizing film caused by light energy. Examples of the water-soluble radical scavenger include compounds having a radical scavenging function, such as 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 the radical species generated in the polarizing film, the water-soluble radical scavenger is preferably, for example, a compound having a nitroxy radical or a nitroxide group.

[0055] 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, 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.

[0056] 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 From 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.

[0057] In the general formulas (1) to (5), R 2 From R 5 From 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. 9From 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.

[0058] 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.

[0059] 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]

[0060] Furthermore, the water-soluble radical scavenger preferably has a molecular weight of 1,000 or less, more preferably 500 or less, and even more preferably 300 or less, from the viewpoint of suppressing polyenization of the polarizing film due to light energy.

[0061] From the viewpoint of suppressing polyenization of the polarizing film, the content of the water-soluble radical scavenger in the functional layer is preferably 0.1% by weight or more, more preferably 5% by weight or more, and even more preferably 10% by weight or more, and from the viewpoint of the appearance of the functional layer after the drying process, the content of the water-soluble radical scavenger in the functional layer is preferably 50% by weight or less, more preferably 40% by weight or less, and even more preferably 30% by weight or less.

[0062] The functional layer can be formed from any material as long as it is a binder resin capable of forming a layer such as a coating film, and examples thereof include water-soluble plastic resins such as polyvinyl alcohol resins and polyacrylamides. Among these, polyvinyl alcohol resins are preferred from the viewpoints of adhesion to the polarizing film and durability. The binder resins can be used alone or in combination of two or more.

[0063] An example of the polyvinyl alcohol-based resin is polyvinyl alcohol. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. Another example of the polyvinyl alcohol-based resin is a saponified copolymer of vinyl acetate and a copolymerizable monomer. When the copolymerizable monomer is ethylene, an ethylene-vinyl alcohol copolymer is obtained. Examples of the copolymerizable monomer include unsaturated carboxylic acids and their esters, such as maleic acid (anhydride), fumaric acid, crotonic acid, itaconic acid, and (meth)acrylic acid; α-olefins, such as ethylene and propylene; (meth)allylsulfonic acid (sodium); sodium sulfonate (monoalkyl maleate); sodium disulfonate alkyl maleate; N-methylolacrylamide; alkali salts of acrylamidoalkylsulfonic acid; N-vinylpyrrolidone; and N-vinylpyrrolidone derivatives. Another example of the polyvinyl alcohol-based resin is a modified polyvinyl alcohol-based resin having a hydrophilic functional group on the side chain of the polyvinyl alcohol or its copolymer. Examples of the hydrophilic functional group include an acetoacetyl group, a carbonyl group, etc. The modified polyvinyl alcohol resin may be a polyvinyl alcohol resin that has been acetalized, urethane-modified, etherified, grafted, phosphate-modified, or the like.

[0064] The saponification degree of the polyvinyl alcohol resin may be, for example, 88% or more, and from the viewpoint of optical durability under high temperature and high humidity, the saponification degree is preferably 90% or more, and more preferably 95% or more. The saponification degree can be determined in accordance with JIS K 6726.

[0065] The functional layer is formed from a resin composition containing the binder resin as a main component, and, for example, the proportion of the binder resin in the functional layer is preferably 70% by weight or more, more preferably 80% by weight or more, and even more preferably 90% by weight or more.

[0066] The resin composition may be prepared as a solution by dissolving or dispersing the binder resin in a solvent. Examples of the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, glycols, alcohols, and amines such as ethylenediamine and diethylenetriamine. The solvents may be used alone or in combination of two or more.

[0067] The functional layer may contain additives such as a crosslinking agent, a plasticizer, a surfactant, a coupling agent, a tackifier, a heat stabilizer, and a hydrolysis stabilizer.

[0068] The functional layer may be formed, for example, by applying the resin composition to the polarizing film and drying the applied composition. The application method is not particularly limited, and examples thereof include roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, and knife coating.

[0069] From the viewpoint of suppressing polyenization of the polarizing film, the functional layer preferably has a thickness of 0.1 μm or more, more preferably 0.2 μm or more, and even more preferably 0.5 μm or more, and from the viewpoint of optical durability under high temperature and high humidity conditions, the functional layer preferably has a thickness of 10 μm or less, more preferably 5 μm or less, even more preferably 2 μm or less, and even more preferably 1 μm or less.

[0070] The polarizing film may have a first transparent protective film provided on the functional layer via an adhesive layer, and a second transparent protective film provided on the side opposite to the viewing side of the polarizing film.

[0071] <First and second transparent protective films> The first and second transparent protective films are 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 films include thermoplastic resins that are excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, etc. 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 may have a cured layer formed from a thermosetting resin or an ultraviolet-curable resin, such as a (meth)acrylic, urethane, acrylic urethane, epoxy, or silicone resin, etc. Among these, cellulose ester resins, polycarbonate resins, (meth)acrylic resins, cyclic polyolefin resins, and polyester resins are preferred.

[0072] The thickness of the first and second transparent protective films can be determined as appropriate, but generally, from the standpoint 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.

[0073] When the first and second transparent protective films are attached to both sides of the polarizing film, the transparent protective films on both sides may be the same or different.

[0074] The transparent protective film can be a retardation plate having a front retardation of 40 nm or more and / or a thickness retardation of 80 nm or more. The front retardation is usually controlled to be in the range of 40 to 200 nm, and the thickness retardation is usually controlled to be in the range of 80 to 300 nm. When a retardation plate is used as the transparent protective film, the retardation plate also functions as the transparent protective film, allowing for a thinner film.

[0075] Examples of the retardation plate include a birefringent film obtained by uniaxially or biaxially stretching a polymer material, an oriented film of a liquid crystal polymer, and an oriented layer of a liquid crystal polymer supported by a film. The thickness of the retardation plate is not particularly limited, but is generally about 20 to 150 μm. The retardation plate may be used by being attached to a transparent protective film that does not have a retardation.

[0076] The first and second transparent protective films may contain any appropriate additives, such as ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, coloring inhibitors, flame retardants, antistatic agents, pigments, colorants, etc. In particular, when the transparent protective films contain ultraviolet absorbers, the light resistance of the polarizing film can be improved.

[0077] The first transparent protective film has a moisture permeability of 100 g / (m) from the viewpoint of production efficiency in the drying process after lamination. 2 24h) or more, and 200g / (m 2 24h) or more, and from the viewpoint of durability of the polarizing plate under high temperature and high humidity, the moisture permeability is preferably 1000g / (m 2 24h) or less, and 600g / (m 2 24h). In addition, the second transparent protective film has a moisture permeability of 300 g / (m 2 24h) or less, and 200g / (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.

[0078] The surfaces of the first and second transparent protective films that are not bonded to the polarizing film may be provided with other layers such as a hard coat layer, an anti-reflection layer, an anti-sticking layer, a diffusion layer, an anti-glare layer, etc. The hard coat layer, anti-reflection layer, anti-sticking layer, diffusion layer, anti-glare layer, etc. may be provided on the protective film itself, or may be provided separately from the protective film.

[0079] The functional layer and the first transparent protective film are bonded together via an adhesive layer, and the polarizing film and the second transparent protective film, the first and second transparent protective films and the other layer, or the polarizing film and the other layer are usually bonded together via a pressure-sensitive adhesive layer or an adhesive layer.

[0080] 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.

[0081] 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.

[0082] The adhesive for forming the adhesive layer can be any of various adhesives used in polarizing films, including isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl latex-based adhesives, and water-based polyesters. These adhesives are typically used as aqueous solution adhesives (water-based adhesives) and contain 0.5 to 60% by weight of solids. Among these, polyvinyl alcohol-based adhesives are preferred, and acetoacetyl group-containing polyvinyl alcohol-based adhesives are more preferred. In particular, water-based adhesives are preferred as adhesives for bonding the functional layer and the first transparent protective film from the viewpoint of adhesion between the functional layer and the polarizing film.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] The adhesive may be applied to any one of the functional layer side, the first and second transparent protective film side (or the other layer side), and the polarizing film side, or may be applied to both. After lamination, a drying step is performed to form an adhesive layer consisting of the applied and dried 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.

[0087] In an embodiment in which the functional layer and the first transparent protective film are bonded together via the adhesive layer, the total thickness of the functional layer and the adhesive layer is preferably 0.2 μm or more, more preferably 0.3 μm or more, and even more preferably 0.6 μm or more, from the viewpoint of suppressing polyenization of the polarizing film, and is preferably 11 μm or less, more preferably 6 μm or less, even more preferably 4 μm or less, and even more preferably 2 μm or less, from the viewpoint of durability of the polarizing plate under high temperature and high humidity conditions.

[0088] The polarizing film, the functional layer, the first and second transparent protective films, and the other layers may be subjected to a surface modification treatment or an easy-adhesion treatment.

[0089] Examples of the surface modification treatment include corona treatment, plasma treatment, primer treatment, and saponification treatment.

[0090] Examples of the adhesion-improving treatment include treatment with a forming material containing various resins having a polyester skeleton, a polyether skeleton, a polycarbonate skeleton, a polyurethane skeleton, a silicone-based resin, a polyamide skeleton, a polyimide skeleton, a polyvinyl alcohol skeleton, or the like.

[0091] The functional layer and the first transparent protective film, the second transparent protective film and the polarizing film, the first and second transparent protective films and the other layer, or the polarizing film and the other layer may be laminated via an intervening layer such as a blocking layer or a refractive index adjusting layer.

[0092] The blocking layer has the function of preventing impurities such as oligomers and ions eluted from a transparent protective film, etc., from migrating (penetrating) into the polarizing film. The blocking layer may be any layer as long as it is transparent and can prevent impurities from eluting from a transparent protective film, etc. Examples of materials for forming the blocking layer include urethane prepolymer-based forming materials, cyanoacrylate-based forming materials, and epoxy-based forming materials.

[0093] 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 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.

[0094] <Laminated polarizing film> The laminated polarizing film (optical laminate) of the present invention has the polarizing film laminated to an optical layer. The optical layer is not particularly limited, and may be, for example, one or more optical layers that are sometimes used in the formation of liquid crystal displays, such as a reflector, a semi-transmitting plate, a retardation plate (including half-wave or quarter-wave plates), or a viewing angle compensation film. Examples of the laminated polarizing film include a reflective polarizing film or a semi-transmitting polarizing film obtained by laminating a reflector or semi-transmitting reflector on the polarizing film; an elliptical polarizing film or a circular polarizing film obtained by laminating a retardation plate on the polarizing film; a wide-viewing angle polarizing film obtained by laminating a viewing angle compensation film on the polarizing film; and a polarizing film obtained by laminating a brightness enhancement film on the polarizing film.

[0095] An adhesive layer may be provided on one or both surfaces of the polarizing film or the laminated polarizing film for bonding an image display cell such as a liquid crystal cell or an organic EL element to other components, such as a front transparent plate or a front transparent member such as a touch panel on the viewing side. 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 a base polymer such as an acrylic polymer, a silicone polymer, polyester, polyurethane, polyamide, polyether, a fluorine-based polymer, or a rubber-based polymer. In particular, pressure-sensitive adhesives that have excellent optical transparency, moderate wettability, cohesion, and adhesion, and excellent weather resistance, heat resistance, etc., such as pressure-sensitive adhesives containing acrylic polymers, are preferably used.

[0096] The application of a pressure-sensitive adhesive layer to one or both surfaces of the polarizing film or the laminated polarizing film can be carried out by any suitable method. Examples of application of a pressure-sensitive adhesive layer include preparing a pressure-sensitive adhesive solution and applying it directly to the polarizing film or the laminated polarizing film by a suitable application method such as a casting method or a coating method, or forming a pressure-sensitive adhesive layer on a separator and then transferring it onto the polarizing film or the laminated polarizing film. The thickness of the pressure-sensitive 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. The polarizing film or the laminated polarizing film having a pressure-sensitive adhesive layer on at least one surface thereof is referred to as a pressure-sensitive adhesive layer-attached polarizing film or a pressure-sensitive adhesive layer-attached laminated polarizing film.

[0097] 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.

[0098] <Image display panel and image display device> The image display panel of the present invention has the polarizing film or the laminated polarizing film bonded to the image display cell on the side opposite to the viewing side of the polarizing film. The image display device of the present invention also has a front transparent member on the polarizing film or laminated polarizing film side (viewing side) of the image display panel.

[0099] Examples of the image display cell include a liquid crystal cell and an organic EL cell. The liquid crystal cell may be, for example, a reflective liquid crystal cell that uses external light, a transmissive liquid crystal cell that uses light from a light source such as a backlight, or a semi-transmissive semi-reflective liquid crystal cell that uses both external light and light from the light source. When the liquid crystal cell uses light from a light source, the image display device (liquid crystal display device) has a polarizing film disposed on the opposite side of the image display cell (liquid crystal cell) from the viewing side, and further has a light source disposed thereon. The polarizing film on the light source side and the liquid crystal cell are preferably bonded together via an appropriate adhesive layer. The liquid crystal cell may be driven in any mode, such as VA mode, IPS mode, TN mode, STN mode, or bend orientation (π type).

[0100] The organic EL cell preferably has a light-emitting body (organic electroluminescence light-emitting body) formed by sequentially laminating a transparent electrode, an organic light-emitting layer, and a metal electrode on a transparent substrate. The organic light-emitting layer is a laminate of various organic thin films, and various layer configurations can be adopted, such as a laminate of a hole-injection layer made of a triphenylamine derivative or the like and a light-emitting layer made of a fluorescent organic solid such as anthracene, a laminate of such a light-emitting layer and an electron-injection layer made of a perylene derivative or the like, or a laminate of a hole-injection layer, a light-emitting layer, and an electron-injection layer.

[0101] Examples of the front transparent member disposed on the viewing side of the image display cell include a front transparent plate (window layer) and a touch panel. A transparent plate having appropriate mechanical strength and thickness is used as the front transparent plate. Examples of such transparent plates include transparent resin plates such as acrylic resins and polycarbonate resins, and glass plates. Examples of the touch panel include various touch panels such as resistive, capacitive, optical, and ultrasonic touch panels, as well as glass or transparent resin plates equipped with touch sensor functions. When a capacitive touch panel is used as the front transparent member, it is preferable to provide a front transparent plate made of glass or a transparent resin plate on the viewing side of the touch panel. [Example]

[0102] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0103] Example 1 <Preparation of polarizing film> A 100 μm thick amorphous isophthalic acid-co-polyethylene terephthalate (IPA-co-PET) film substrate with a water absorption of 0.75% and a Tg of 75°C was corona-treated on one side. An aqueous solution containing polyvinyl alcohol (4200°C, 99.2 mol% saponification degree) and acetoacetyl-modified PVA (1200°C, 4.6% acetoacetyl-modification degree, and at least 99.0 mol% saponification degree, manufactured by Nippon Synthetic Chemical Industry Co., Ltd. under the trade name "GOHSEFIRMER Z200") in a 9:1 ratio was applied to the corona-treated surface and dried at 25°C to form an 11 μm thick PVA resin layer. The resulting laminate was then uniaxially stretched 2.0 times in the machine direction (longitudinal direction) between rolls operating at different peripheral speeds in a 120°C oven (in-air assisted stretching). Next, the laminate was immersed in an insolubilizing bath (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 30°C for 30 seconds (insolubilization treatment). Next, the laminate was immersed in a dyeing bath (a dyeing treatment) at a liquid temperature of 30°C, adjusting the iodine concentration and immersion time so that the polarizing plate had a predetermined transmittance. Next, the laminate was immersed in a crosslinking bath (a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 30°C for 30 seconds (crosslinking treatment). Thereafter, while immersed in a boric acid aqueous solution (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid and 5 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 70°C, the laminate was uniaxially stretched in the longitudinal direction (machine direction) between rolls operating at different peripheral speeds to a total stretch ratio of 5.5 times (underwater stretching treatment). The laminate was then immersed in a cleaning bath (aqueous solution prepared by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 30°C (cleaning treatment). It was then dried in an oven maintained at 90°C, while being brought into contact with a SUS heated roll maintained at a surface temperature of 75°C for approximately 2 seconds (drying shrinkage treatment). This resulted in an optical film laminate including a 5 μm-thick polarizing film.

[0104] <Preparation of Resin Composition for Forming Functional Layer> An aqueous solution (solid content 25 wt%) was prepared containing a polyvinyl alcohol resin (manufactured by Nippon Vinyl Acetate & Poval Co., Ltd., product name: JC-25H) with a degree of polymerization of 2500 and a degree of saponification of 99.8 mol% dissolved in pure water and a water-soluble radical scavenger represented by the following general formula (9) in a weight ratio of 3:1 after drying and film formation. [ka]

[0105] <Preparation of polarizing film> The surface of the optical film laminate where the polarizing film was exposed, cut into sheets along the stretching axis direction, was subjected to a corona treatment, and the resin composition prepared above was applied with a wire bar so that the thickness after drying would be 0.8 μm, and then dried at 60°C for 5 minutes to form a functional layer on the polarizing film. The thickness of the functional layer was measured by cutting the cross section with a microtome (Leica, "EM UC7") as a pretreatment, and then subjecting the cut surface to metal ion sputtering, followed by measuring the film thickness with an SEM (JEOL Ltd., "JSM-7100F"). The results are shown in Table 1. Next, a 48 μm-thick triacetyl cellulose film (moisture permeability 300 g / (m)) having a hard coat layer was attached as a first transparent protective film via a water-based adhesive. 2 A polarized film was fabricated by laminating a triacetyl cellulose film (Fujifilm, "TJ40UL") to the functional layer using a roll laminator with the triacetyl cellulose film facing the functional layer, followed by heating and drying in an oven (60°C for 4 minutes). The aqueous adhesive used was an aqueous solution containing acetoacetyl-containing polyvinyl alcohol resin (average degree of polymerization: 1,200, saponification degree: 98.5 mol%, acetoacetylation degree: 5 mol%) and methylol melamine in a weight ratio of 3:1. Furthermore, after lamination, the functional layer swells and deforms, resulting in interfacial mixing and difficult separation. Therefore, the combined thickness of the functional layer and the aqueous adhesive layer was measured using an SEM, in the same way as for the functional layer described above. The results are shown in Table 1.

[0106] <Fabrication of pseudo image display panel> The polarizing film obtained above was used, and after the polyethylene terephthalate film was peeled off, the polarizing film on the peeled surface was subjected to a corona treatment. A cycloolefin film (with a moisture permeability of 31 g / (m)) was then applied as a second transparent protective film. 2 The specimen was then attached to a sheet of "G-Film" manufactured by ZEON Corporation via a UV-curable adhesive (thickness 1.0 μm) for 24 hours, and then irradiated with ultraviolet light as active energy rays to cure the adhesive. The ultraviolet light was irradiated using a gallium-filled metal halide lamp, irradiation equipment: Light HAMMER 10 manufactured by Fusion UV Systems, Inc., bulb: V bulb, peak irradiance: 1,600 mW / cm 2 , cumulative irradiation dose 1,000 / mJ / cm 2 The ultraviolet irradiance was measured using a Sola-Check system manufactured by Solatell, Inc. The cycloolefin film was then attached to a small piece of glass (pseudo image display cell) measuring 45 x 50 mm with an adhesive to produce a pseudo image display panel.

[0107] <Evaluation of light resistance (1)> The pseudo image display panel obtained above was placed in a light resistance tester (manufactured by Suga Test Instruments Co., Ltd., "Ultraviolet Fade Meter U48") so that the pseudo image display cell was set up so that light was incident from the viewing side, and then light was irradiated for 528 hours, and the single transmittance before and after irradiation was measured. Before irradiation, it was Ts0, and after irradiation, it was Ts 528 When this is the case, the change in single transmittance (ΔTs) was calculated using the following formula. ΔTs(%)=Ts 528 -Ts0 The optical characteristics of the single-piece transmittance were measured using a UV-visible spectrophotometer (Otsuka Electronics, "LPF-200") to obtain the initial single-piece transmittance Ts0. The single-piece transmittance is the Y value corrected for visibility using a 2-degree visual field (C light source) according to JIS Z 8701-1982. The measurement wavelength was 380 to 780 nm (every 5 nm). The results of this ΔTs are shown in Table 1.

[0108] <Evaluation of lightfastness (2)> The pseudo image display panel obtained above was placed in a light resistance tester (manufactured by Suga Test Instruments Co., Ltd., "NX75") so that light was incident from the visible side, and then subjected to irradiance of 100 W / m 2 at a wavelength of 300 to 400 nm. 2 The sample was irradiated for 300 hours at a black panel temperature of 89°C and a humidity of 50%RH in the chamber, and ΔTs was calculated from the single-unit transmittance before and after irradiation in the same manner as in the above evaluation (1). The results of ΔTs are shown in Table 1.

[0109] Based on the above light resistance evaluation results, the evaluation was made according to the following criteria. The evaluation results are shown in Table 1. ◎: 3% ≥ ΔTs ≥ 0 ○: 5% ≥ ΔTs > 3% ×: ΔTs<0

[0110] <Example 2> A polarizing film and a pseudo image panel were prepared in the same manner as in Example 1, except that the thickness of the functional layer was changed to 0.4 μm, and were subjected to evaluation. The results are shown in Table 1.

[0111] Example 3 A polarizing film and a pseudo image panel were prepared and evaluated in the same manner as in Example 1, except that the thickness of the functional layer was changed to 1.5 μm. The results are shown in Table 1.

[0112] Example 4 A polarizing film and a pseudo image panel were prepared and evaluated in the same manner as in Example 1, except that the water-soluble radical scavenger contained in the functional layer was adjusted to a solids content of 15% by weight. The results are shown in Table 1.

[0113] <Comparative Example 1> A polarizing film and a pseudo image panel were produced and evaluated in the same manner as in Example 1, except that no functional layer was formed. The results are shown in Table 1.

[0114] <Comparative Example 2> A polarizing film and a pseudo image panel were prepared and evaluated in the same manner as in Example 1, except that no water-soluble radical scavenger was added to the resin composition forming the functional layer. The results are shown in Table 1.

[0115] [Table 1] [Explanation of symbols]

[0116] 10: Polarizing film 11: Polarizing film 12: Functional layer 13: First transparent protective film 14: Second transparent protective film 20: Adhesive layer 30, 40, and 50: adhesive layer or glue layer 80: Front transparent component 90: Image display cell 100: Image display panel 200: Image display device

Claims

1. A polarizing film constituting an image display panel, the polarizing film has a polarizing membrane, a functional layer, an adhesive layer, and a first transparent protective film; the functional layer is adjacent to the viewing side of the polarizing film and contains a water-soluble radical scavenger; A polarizing film, characterized in that the first transparent protective film is provided on the functional layer via an adhesive layer.

2. 2. The polarizing film according to claim 1, wherein the functional layer contains a polyvinyl alcohol-based resin.

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

4. 4. The polarizing film according to claim 1, wherein the functional layer has a thickness of 10 μm or less.

5. 5. The polarizing film according to claim 1, wherein the polarizing film has a thickness of 15 μm or less.

6. 6. The polarizing film according to claim 1, wherein the adhesive forming the adhesive layer is a water-based adhesive.

7. 7. The polarizing film according to claim 1, wherein the total thickness of the functional layer and the adhesive layer is 0.2 μm or more and 11 μm or less.

8. 8. The polarizing film according to claim 1, further comprising a second transparent protective film provided on the side opposite to the viewing side of the polarizing film.

9. A laminated polarizing film, comprising the polarizing film according to any one of claims 1 to 8 laminated to an optical layer.

10. An image display panel, characterized in that the polarizing film according to any one of claims 1 to 8, the side opposite to the viewing side of the polarizing film, or the laminated polarizing film according to claim 9, is bonded to an image display cell.

11. An image display device comprising: a front transparent member on the polarizing film or laminated polarizing film side of the image display panel according to claim 10.

Images