Image display device

Abstract

To provide an image display device which is superior in suppressing a reduction in single transmittance and suppressing an increase in the single hue b value of a polarizing membrane in a high temperature environment.SOLUTION: An image display device comprising a front transparent member, a polarizing film, and an image display cell is provided, in this order, with a pressure-sensitive adhesive layer or an adhesive layer between each, wherein a laminate formed by bonding glass sheets via the pressure-sensitive adhesive layer or the adhesive layer to both surfaces of the polarizing film has a change amount in single transmittance of 0 to 3% and a change amount in single hue b value of 0 to 4 in NBS ratings before and after a heat resistance test under conditions of 105°C and 500 hours.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to 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 above-mentioned in-vehicle image display devices, display designs have become increasingly irregular and larger due to the recent development of autonomous driving technology. Along with these changes in display design, there is a demand for means to further improve the durability of polarizing films under high-temperature environments.

[0007] In view of the above circumstances, an object of the present invention is to provide an image display device that is excellent in suppressing a decrease in the single transmittance of a polarizing film and in suppressing an increase in the single hue b value in a high-temperature environment. [Means for solving the problem]

[0008] That is, the present invention relates to an image display device in which a front transparent member, a polarizing film, and an image display cell are arranged in this order via a pressure-sensitive adhesive layer or an adhesive layer, and the laminate in which glass plates are bonded to both sides of the polarizing film via the pressure-sensitive adhesive layer or the adhesive layer has a change in single-unit transmittance of 0 to 3% and a change in single-unit hue b value of 0 to 4 NBS before and after a heat resistance test at 105°C for 500 hours. [Effects of the Invention]

[0009] Although the details of the mechanism of action of the effects of the image display device of the present invention are unclear, it is presumed as follows: However, the present invention does not need to be interpreted as being limited to this mechanism of action.

[0010] The image display device of the present invention comprises a front transparent member, a polarizing film, and an image display cell, arranged in this order with a pressure-sensitive adhesive layer or adhesive layer interposed therebetween. Glass plates are bonded to both sides of the polarizing film with the pressure-sensitive adhesive layer or adhesive layer interposed therebetween to form a laminate. The laminate exhibits a change in single-piece transmittance of 0 to 3% and a change in single-piece hue b value of 0 to 4 NBS before and after a heat resistance test at 105°C for 500 hours. Since the glass plates correspond to the front transparent member and the image display cell, the laminate corresponds to a pseudo image display device. To date, no laminate (pseudo image display device) has been known in which the change in single-piece transmittance is 0 to 3% and the change in single-piece hue b value is 0 to 4 NBS under the heat resistance test conditions described above. On the other hand, to prevent a decrease in the single-unit transmittance of a polarizing film, for example, Patent Document 1 discloses that a heat treatment (aging) is performed after bonding a polarizing film with a pressure-sensitive adhesive layer on one side to an image display cell to form an image display panel, thereby reducing the moisture content of the polarizing film (hereinafter also referred to as conventional aging treatment). In the present invention, it has been discovered that moisture contained in the pressure-sensitive adhesive or adhesive layers on both sides of a polarizing film for bonding to the front transparent member or image display cell affects the decrease in the single-unit transmittance and the increase in the single-unit hue b value (high-temperature durability) of the polarizing film after a heat resistance test of the image display device. Therefore, by subjecting the pressure-sensitive adhesive or adhesive layers on both sides of the polarizing film for bonding to the front transparent member or image display cell to a heat treatment (aging), the high-temperature durability of the polarizing film can be further improved. Furthermore, in the present invention, in addition to the conventional aging treatment, a water-soluble radical scavenger is added to the polarizing film. This scavenges generated radicals and suppresses polyenization, even in high-temperature environments where polyenization is likely to occur in the polarizing film, thereby further improving the high-temperature durability of the polarizing film. In addition to the above-mentioned techniques, the present invention can further improve the high-temperature durability of the polarizing film by increasing the potassium concentration of the polarizing film. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view showing one embodiment of an image display device. [Figure 2] FIG. 1 is a schematic cross-sectional view showing one embodiment of a polarizing film. DETAILED DESCRIPTION OF THE INVENTION

[0012] Fig. 1 is a schematic cross-sectional view showing one embodiment of an image display device of the present invention. In the image display device 100 of Fig. 1, a front transparent member 80 and a polarizing film 10 are bonded together via a pressure-sensitive adhesive layer or adhesive layer 20, and an image display cell 90 and the polarizing film 10 are bonded together via a pressure-sensitive adhesive layer or adhesive layer 30.

[0013] Fig. 2 is a schematic cross-sectional view showing one embodiment of the polarizing film of the present invention. In the polarizing film 10 shown in Fig. 3, a polarizing film 11 and a transparent protective film 13 are bonded together via a pressure-sensitive adhesive layer or adhesive layer 50, and the polarizing film 11 and a transparent protective film 12 are bonded together via a pressure-sensitive adhesive layer or adhesive layer 40.

[0014] The image display device of the present invention comprises a front transparent member, a polarizing film, and an image display cell arranged in this order via a pressure-sensitive adhesive layer or an adhesive layer, and a laminate in which glass plates are bonded to both sides of the polarizing film via the pressure-sensitive adhesive layer or the adhesive layer, exhibits a change in single-unit transmittance of 0 to 3% and a change in single-unit hue b value of 0 to 4 NBS before and after a heat resistance test at 105°C for 500 hours.

[0015] <Polarizing film> The polarizing film of the present invention has a polarizing layer formed by adsorbing and aligning a dichroic substance such as iodine or a dichroic dye on a polyvinyl alcohol-based film. From the viewpoint of the initial polarization performance of the polarizing layer, an iodine-based polarizing layer containing iodine as the dichroic substance is preferred.

[0016] The polyvinyl alcohol (PVA) film is transparent in the visible light region and can be used without any particular limitation as long as it disperses and adsorbs dichroic substances such as iodine and dichroic dyes. Examples of materials for the polyvinyl alcohol film include polyvinyl alcohol and its derivatives. Examples of polyvinyl alcohol derivatives include polyvinyl formal, polyvinyl acetal; olefins such as ethylene and propylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, and their alkyl esters, modified with acrylamide, etc. The polyvinyl alcohol preferably has an average degree of polymerization of approximately 100 to 10,000, more preferably approximately 1,000 to 10,000, and even more preferably approximately 1,500 to 4,500. The polyvinyl alcohol preferably has a saponification degree of approximately 80 to 100 mol%, more preferably approximately 95 mol% to 99.95 mol%. The average degree of polymerization and the saponification degree can be determined in accordance with JIS K 6726.

[0017] The polarizing film may contain a water-soluble radical scavenger from the viewpoint of suppressing a decrease in the single-unit transmittance of the polarizing film and an increase in the single-unit hue b value in a high-temperature environment. The water-soluble radical scavenger is preferably a compound that can dissolve at least 1 part by weight in 100 parts by weight of water at 25°C, more preferably a compound that can dissolve at least 2 parts by weight in 100 parts by weight of water at 25°C, and even more preferably a compound that can dissolve at least 5 parts by weight in 100 parts by weight of water at 25°C, from the viewpoint of easy migration into moisture in the polarizing film. The water-soluble radical scavenger may be used alone or in combination of two or more types.

[0018] The water-soluble radical scavenger is presumed to be capable of suppressing the formation of polyenes in the polarizing film in a high-temperature environment. 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.

[0019] 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 each 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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]

[0024] Furthermore, from the viewpoint of being able to efficiently capture radicals generated in the polarizing film, 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.

[0025] When the polarizing film contains the water-soluble radical scavenger, the content of the water-soluble radical scavenger is preferably 0.005% by weight or more, more preferably 0.01% by weight or more, and even more preferably 0.1% by weight or more, from the viewpoint of suppressing a decrease in the single-piece transmittance of the polarizing film and an increase in the single-piece hue b value in a high-temperature environment, and is preferably 15% by weight or less, more preferably 12% by weight or less, even more preferably 10% by weight or less, and even more preferably 5% by weight or less.

[0026] The polarizing film may have an increased potassium concentration in order to suppress a decrease in the single-unit transmittance of the polarizing film and an increase in the single-unit hue b value in a high-temperature environment. When the potassium concentration is increased, the potassium concentration is preferably 0.3 wt % or more, more preferably 0.35 wt % or more, and even more preferably 0.4 wt % or more. In order to suppress a change in reflective hue in a high-temperature environment, the potassium concentration in the polarizing film is preferably 0.8 wt % or less, and more preferably 0.6 wt % or less.

[0027] The polarizing film can be obtained by a conventional polarizing film manufacturing method, for example, by subjecting the polyvinyl alcohol film to optional swelling and washing steps, and at least a dyeing step, a crosslinking step, and a stretching step. When the polarizing film contains the water-soluble radical scavenger, the treatment bath in one or more of the swelling, washing, dyeing, crosslinking, and stretching steps may contain the water-soluble radical scavenger. Furthermore, the potassium concentration of the polarizing film can be increased by controlling the concentration of a potassium component-donating substance, such as a potassium halide such as potassium iodide, contained in one or more of the swelling, washing, dyeing, crosslinking, and stretching steps, and the treatment temperature and treatment time in each of the treatment baths.

[0028] 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 20 μm or less, more preferably 15 μm or less, even 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.

[0029] A polarizing film (thin polarizing film) can be obtained by a conventional polarizing film manufacturing method, for example, 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 thermoplastic resin substrate to prepare a laminate, and then, while transporting the obtained laminate in the longitudinal direction, subjecting the laminate to optional insolubilization treatment, crosslinking treatment, and washing treatment, and at least an auxiliary in-air stretching treatment, dyeing treatment, and underwater stretching treatment. When the polarizing film contains the water-soluble radical scavenger, the treatment bath in any one or more of the insolubilization treatment, crosslinking treatment, washing treatment, dyeing treatment, and underwater stretching treatment may contain the water-soluble radical scavenger. Furthermore, when the potassium concentration of the polarizing film is increased, it can be controlled by the concentration of a potassium component donor, such as potassium halide, such as potassium iodide, contained in a treatment bath in one or more of the insolubilization treatment step, the crosslinking treatment step, the washing treatment step, the dyeing treatment step, and the underwater stretching treatment step, and by the treatment temperature and treatment time in each of the treatment baths.

[0030] The polarizing film is usually a polarizing film having a transparent protective film attached to at least one surface of the polarizing film via a pressure-sensitive adhesive layer or an adhesive layer.

[0031] <Adhesive layer> The adhesive layer may be formed from various adhesives used in polarizing films, such as rubber-based adhesives, acrylic-based adhesives, silicone-based adhesives, urethane-based adhesives, vinyl alkyl ether-based adhesives, polyvinyl alcohol-based adhesives, polyvinyl pollidone-based adhesives, polyacrylamide-based adhesives, and cellulose-based adhesives. Among these, acrylic-based adhesives are preferred. The acrylic-based adhesive contains an acrylic polymer as a base polymer, and examples of the acrylic-based adhesives include those described in JP 2017-75998 A and the like.

[0032] The acrylic polymer in the acrylic pressure-sensitive adhesive has a main skeleton of a (meth)acrylic acid alkyl ester monomer unit. A (meth)acrylic acid alkyl ester having an alkyl group containing 1 to 20 carbon atoms is preferably used as the (meth)acrylic acid alkyl ester. The content of the (meth)acrylic acid alkyl ester is preferably 40% by weight or more, more preferably 60% by weight or more, based on the total amount of monomer components constituting the base polymer. Furthermore, from the viewpoint of adjusting the adhesive properties of the pressure-sensitive adhesive, a monomer unit such as a nitrogen-containing monomer unit or a hydroxyl group-containing monomer may be contained. Furthermore, a crosslinking agent may be used to form a crosslinked structure in the pressure-sensitive adhesive layer. Examples of commonly used crosslinking agents include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, oxazoline-based crosslinking agents, aziridine-based crosslinking agents, carbodiimide-based crosslinking agents, and metal chelate-based crosslinking agents. The amount of crosslinking agent used is typically 10 parts by weight or less, preferably 5 parts by weight or less, based on 100 parts by weight of the base polymer.

[0033] To the pressure-sensitive adhesive, tackifiers such as silane coupling agents, terpene-based tackifiers, styrene-based tackifiers, phenol-based tackifiers, rosin-based tackifiers, and epoxy-based tackifiers may be added in order to adjust the adhesive strength. Furthermore, to improve light resistance, ultraviolet absorbers may be added. In addition to the components exemplified above, the pressure-sensitive adhesive may contain additives such as plasticizers, softeners, antidegradants, fillers, colorants, antioxidants, surfactants, and antistatic agents, provided that the properties of the pressure-sensitive adhesive are not impaired.

[0034] 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.

[0035] <Adhesive layer> The adhesive layer may be formed using various adhesives used in polarizing films, such as isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl latex-based adhesives, and water-based polyesters. These adhesives are usually 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] The adhesive may be applied to either the transparent protective film side (or the functional layer side) described below, the polarizing film side, or 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 is preferably about 30 to 5,000 nm, more preferably about 100 to 1,000 nm, when a water-based adhesive or the like is used. When a UV-curable adhesive or an electron beam-curable adhesive is used, the thickness is preferably about 0.1 to 100 μm, more preferably about 0.5 to 10 μm.

[0040] <Transparent protective film> The transparent protective film is not particularly limited, and various transparent protective films used in polarizing films can be used. Examples of materials that can be used to form the transparent protective film include thermoplastic resins that are excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, and isotropy. Examples of thermoplastic resins include cellulose ester resins such as triacetyl cellulose, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins such as nylon and aromatic polyamide, polyimide resins, polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymers, (meth)acrylic resins, cyclic polyolefin resins (norbornene resins) having a cyclo- or norbornene structure, polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. The transparent protective film can also include a cured layer formed from a thermosetting resin or ultraviolet-curable resin, such as a (meth)acrylic, urethane, acrylic urethane, epoxy, or silicone resin. Among these, cellulose ester resins, polycarbonate resins, (meth)acrylic resins, cyclic polyolefin resins, and polyester resins are preferred.

[0041] The thickness of the transparent protective film can be determined as appropriate, but generally, from the viewpoints of workability such as strength and handling, thinness, etc., it is preferably about 1 to 500 μm, more preferably about 1 to 300 μm, and even more preferably about 5 to 100 μm.

[0042] When the 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.

[0043] 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.

[0044] 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.

[0045] The transparent protective film may contain any appropriate additive, such as an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, a coloring inhibitor, a flame retardant, an antistatic agent, a pigment, a colorant, etc. In particular, when the transparent protective film contains an ultraviolet absorber, the light resistance of the polarizing film can be improved.

[0046] When the transparent protective film is attached to the viewing side of the polarizing film, the film should have a moisture permeability of 600 g / (m 2 24h) or less, and 400g / (m 2 When the transparent protective film is attached to the image display cell side of the polarizing film, it is more preferable that the moisture permeability of the transparent protective film is 50 g / (m 2 ) or less from the viewpoint of production efficiency in the drying process after attachment. 2 24h) or more, and 100g / (m 2 24h) or more, and the moisture permeability is 1000g / (m 2 24h) or less, and 600g / (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.

[0047] The surface of the transparent protective film to which the polarizing film is not attached may be provided with a functional layer such as a hard coat layer, an anti-reflection layer, an anti-sticking layer, a diffusion layer, an anti-glare layer, etc. The functional layer such as the hard coat layer, the anti-reflection layer, the anti-sticking layer, the diffusion layer, or the anti-glare layer may be provided on the protective film itself, or may be provided separately from the protective film.

[0048] The polarizing film and the transparent protective film, or the polarizing film and the functional layer, are usually bonded together via the pressure-sensitive adhesive layer or the adhesive layer.

[0049] The transparent protective film and the polarizing film, or the polarizing film and the functional layer, may be laminated via an intervening layer such as a surface modification treatment layer, an easy-adhesive layer, a blocking layer, or a refractive index adjustment layer.

[0050] Examples of the surface modification treatment for forming the surface modification layer include corona treatment, plasma treatment, primer treatment, and saponification treatment.

[0051] Examples of the easy-adhesion adhesive that forms the easy-adhesion layer include forming materials containing various resins having a polyester skeleton, a polyether skeleton, a polycarbonate skeleton, a polyurethane skeleton, a silicone skeleton, a polyamide skeleton, a polyimide skeleton, a polyvinyl alcohol skeleton, etc. The easy-adhesion layer is usually provided in advance on the protective film, and the easy-adhesion layer side of the protective film and the polarizing film are laminated with the pressure-sensitive adhesive layer or the adhesive layer.

[0052] 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.

[0053] 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.

[0054] The polarizing film may have an optical layer attached to at least one surface of the polarizing film via the pressure-sensitive adhesive layer or the adhesive layer.

[0055] The optical layer is not particularly limited, and may be one or more optical layers that are sometimes used in forming liquid crystal displays, such as a reflector, a semi-transmitting plate, a retardation plate (including half- or quarter-wave plates), a viewing angle compensation film, etc. Examples of the 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.

[0056] The pressure-sensitive adhesive layer or adhesive layer may be applied in advance to one or both surfaces of the polarizing film in order to bond 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.

[0057] It is preferable that a separator be temporarily attached to cover the exposed surface of the pressure-sensitive adhesive layer or the adhesive layer to prevent contamination, etc., until the product is put into practical use. This prevents contamination, etc., of the pressure-sensitive adhesive layer or the adhesive layer under normal handling conditions. Examples of the separator include appropriate thin sheets such as plastic films, rubber sheets, paper, cloth, nonwoven fabrics, nets, foam sheets, metal foils, and laminates thereof, which are coated with an appropriate release agent such as a silicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide-based release agent, as needed.

[0058] <Front transparent member> The front transparent member of the present invention is a front transparent member arranged on the viewing side of the image display cell. Examples of the front transparent member include a front transparent plate (window layer) and a touch panel. The front transparent plate used has appropriate mechanical strength and thickness. Examples of such transparent plates include transparent resin plates such as acrylic resins and polycarbonate resins, and glass plates. Examples of the touch panel used 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.

[0059] <Image display cell> Examples of the image display cell of the present invention include a liquid crystal cell and an organic EL cell. The liquid crystal cell may be, for example, a reflective liquid crystal cell that utilizes external light, a transmissive liquid crystal cell that utilizes light from a light source such as a backlight, or a semi-transmissive semi-reflective liquid crystal cell that utilizes both external and light from the light source. When the liquid crystal cell utilizes light from a light source, the image display device (liquid crystal display device) has a polarizing film disposed on the side opposite the viewing side of the image display cell (liquid crystal cell), 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 alignment (π type).

[0060] 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.

[0061] When forming the image display device, after forming the image display panel by bonding the image display cell and the polarizing film, the image display panel may be subjected to a heat (aging) treatment in a high-temperature environment before bonding to the front transparent member, in order to suppress a decrease in the polarizing film's single transmittance and an increase in the single hue b value. In this case, by subjecting the pressure-sensitive adhesive layer or adhesive layer on both sides of the polarizing film for bonding to the front transparent member or the image display cell to a heat (aging) treatment, a decrease in the single transmittance and an increase in the single hue b value in a high-temperature environment can be further suppressed. The heating conditions for the heat (aging) treatment are not particularly limited as long as they can sufficiently reduce the moisture contained in the polarizing film and the pressure-sensitive adhesive layer or adhesive layer provided on both sides of the polarizing film. For example, the heating temperature is preferably about 70°C to 90°C, more preferably about 75°C to 85°C. The heating time is preferably about 30 minutes to 5 hours, more preferably about 1 hour to 3 hours. Furthermore, when the heat (aging) treatment is performed with a pressure-sensitive adhesive layer or adhesive layer on both sides of the polarizing film, it is more effective if the pressure-sensitive adhesive layer or adhesive layer has high moisture permeability, while when the heat (aging) treatment is performed with a pressure-sensitive adhesive layer or adhesive layer on one side, it is more effective if the pressure-sensitive adhesive layer or adhesive layer to be laminated later (the pressure-sensitive adhesive layer or adhesive layer on the other side) has a low moisture content. Note that when forming the image display device, the front transparent member and the polarizing film may be bonded together, and then the heat (aging) treatment may be performed, and then the image display cell may be bonded. [Example]

[0062] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0063] Example 1 <Preparation of polarizing film> A polyvinyl alcohol film with an average degree of polymerization of 2,400, a degree of saponification of 99.9 mol%, and a thickness of 45 μm was prepared. The polyvinyl alcohol film was immersed in a 30°C swelling bath (water bath) for 30 seconds between rolls with different peripheral speed ratios, where it was stretched 2.2 times in the conveying direction while swelling (swelling step). Subsequently, the film was immersed in a 30°C dye bath (iodine solution obtained by blending iodine and potassium iodide in a weight ratio of 1:7 with 100 parts by weight of water) for 30 seconds, with the iodine concentration adjusted so that the polarizing film had the desired transmittance. The film was then stretched 3.3 times in the conveying direction relative to the original polyvinyl alcohol film (polyvinyl alcohol film that was not stretched in the conveying direction at all) while dyeing (dyeing step). The dyed polyvinyl alcohol film was then immersed in a 40°C crosslinking bath (aqueous solution containing 3.5 wt% boric acid, 3.0 wt% potassium iodide, and 3.6 wt% zinc sulfate) for 28 seconds and stretched in the machine direction to 3.6 times its original size (crosslinking step). The resulting polyvinyl alcohol film was then immersed in a 64°C stretching bath (aqueous solution containing 4.5 wt% boric acid, 5.0 wt% potassium iodide, and 5.0 wt% zinc sulfate) for 60 seconds and stretched in the machine direction to 6.0 times its original size (stretching step). The resulting polyvinyl alcohol film was then immersed in a 27°C washing bath (aqueous solution containing 2.3 wt% potassium iodide and 1.0 wt% water-soluble radical scavenger, a compound represented by the following general formula (9)) for 10 seconds (washing step). The washed polyvinyl alcohol film was dried at 40°C for 30 seconds to produce a polarizing film. The potassium content in the polarizing film was 0.31% by weight, the content of the compound represented by the following general formula (9) was 0.3% by weight, and the thickness of the polarizing film was 18 μm. [ka]

[0064] <Method for measuring potassium content (wt%) in polarizing film> The fluorescent X-ray intensity (kcps) of potassium for the polarizing film was measured using an X-ray fluorescence analyzer (Rigaku Corporation, trade name "ZSX100E," measuring diameter: 10 mm). The thickness (μm) of the polarizing film was measured using a spectroscopic film thickness meter (PEACOCK Corporation, trade name "DG-205"). The potassium content (wt%) was calculated from the obtained fluorescent X-ray intensity and thickness using the following formula. Note that "2.99" below is the coefficient of a calibration curve derived by measuring the fluorescent X-ray intensity (kcps) of a sample with a known thickness (μm) and potassium concentration (wt%) (for example, a PVA-based resin film with a fixed amount of KI added). Potassium content in polarizing film (wt%) = 2.99 × (fluorescent X-ray intensity of potassium element) / (polarizing film thickness)

[0065] <Method for measuring the content (wt%) of water-soluble radical scavenger in polarizing film> Approximately 20 mg of polarizing film was collected, quantified, and dissolved by heating in 1 mL of water, then diluted with 4.5 mL of methanol. The resulting extract was filtered through a membrane filter, and the concentration of the water-soluble radical scavenger in the filtrate was measured using HPLC (Waters ACQUITY UPLC H-class Bio).

[0066] <Preparation of polarizing film> The adhesive used was an aqueous solution containing acetoacetyl group-containing polyvinyl alcohol resin (average polymerization degree 1,200, saponification degree 98.5 mol%, acetoacetylation degree 5 mol%) and methylol melamine in a weight ratio of 3:1. Using this adhesive, a 30 μm-thick transparent protective film (manufactured by Nippon Shokubai, moisture permeability 125 g / (m)) made of (meth)acrylic resin (modified acrylic polymer having a lactone ring structure) was applied to one side (image display cell side) of the polarizing film obtained above. 2 24h)), and on the other side (viewing side) a 48μm thick transparent protective film (moisture permeability 300g / (m 2After laminating the polarizing film on both sides of the film using a roll laminator, the film was subsequently dried by heating in an oven (at 90°C for 10 minutes) to produce a polarizing film with transparent protective films laminated on both sides of the polarizing film.

[0067] <Preparation of acrylic adhesive> A four-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas inlet tube, and a condenser was charged with a monomer mixture containing 99 parts of butyl acrylate and 1 part of 4-hydroxybutyl acrylate. Furthermore, 0.1 parts of 2,2'-azobisisobutyronitrile as a polymerization initiator and 100 parts of ethyl acetate were charged to 100 parts of the monomer mixture (solid content). Nitrogen gas was introduced with gentle stirring to replace the atmosphere, and the temperature in the flask was maintained at around 55°C to carry out a polymerization reaction for 8 hours, producing an acrylic polymer solution with a weight-average molecular weight (Mw) of 1,800,000. Thereafter, 0.02 parts of an isocyanate crosslinking agent (manufactured by Tosoh Corporation, trade name "Takenate D110N", trimethylolpropane / xylylene diisocyanate adduct) and 0.2 parts of a silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "X-41-1056") were blended with 100 parts of the solid content of the obtained acrylic polymer solution to prepare a solution of an acrylic pressure-sensitive adhesive composition.

[0068] <Preparation of polarizing film with adhesive layer> The solution of the acrylic pressure-sensitive adhesive composition obtained above was applied to one side of a polyethylene terephthalate film (Mitsubishi Chemical Polyester Film Co., Ltd., product name "MRF38", separator film) treated with a silicone-based release agent so that the thickness of the pressure-sensitive adhesive layer after drying would be 20 μm, and the film was dried at 90° C. for 1 minute to form a pressure-sensitive adhesive layer on the surface of the separator film. Next, the pressure-sensitive adhesive layer formed on the separator film was transferred to the protective film surface on the image display cell side of the polarized film prepared above, to prepare a polarized film with a pressure-sensitive adhesive layer.

[0069] <Fabrication of pseudo-image display device (laminate)> The resulting polarizing film with adhesive layer was cut to a size of 150 x 45 mm so that the absorption axis of the polarizing film was parallel to the long side. A glass plate (EG-XG, manufactured by Hiraoka Special Glass Manufacturing Co., Ltd., 165 x 50 mm, 0.7 mm thick) was bonded to the adhesive layer. The resulting laminate was then autoclaved at 50°C and 0.5 MPa for 15 minutes to produce a pseudo-image display panel (a laminate having a polarizing film with an adhesive layer on one side). The pseudo-image display panel was then placed in an 80°C hot air oven for 2 hours for aging, then removed from the oven and left for 1 hour in an environment of 23°C and 55% humidity. Another glass panel was then bonded to the viewing-side protective film surface via a 200 μm-thick acrylic acid monomer-free adhesive (manufactured by Nitto Denko Corporation, product name LUCIACS CS98210). The resulting laminate was autoclaved at 50°C and 0.5 MPa for 15 minutes to produce a pseudo-image display device (laminate).

[0070] <Evaluation of durability in high temperature environments> The pseudo-image display device (laminate) obtained above was left to stand in a hot air oven at a temperature of 105°C for 500 hours, and the single-piece transmittance (ΔTs) and single-piece hue b value (Δb) were measured before and after heating. The single-piece transmittance and single-piece hue b value were measured using a spectrophotometer (Otsuka Electronics Co., Ltd., LPF-200). The single-piece transmittance is a 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 (5 nm intervals). ΔTs(%)=Ts 500 -Ts0 Δb(NBS)=b 500 -b0 where Ts0 and b0 are the initial (before heating) single transmittance and single hue b value, and Ts 500 and b 500 are the single-piece transmittance and single-piece hue b value after heating for 500 hours. ΔTs (%) is preferably 0% or more and 3% or less, and more preferably 0% or more and 2% or less. Δb (NBS) is preferably 0 NBS or more and 4 NBS or less, and more preferably 0 NBS or more and 3 NBS or less. The results are shown in Table 1.

[0071] <Example 2> A polarizing film, a polarizing film, and a pseudo-image display device (laminate) were produced in the same manner as in Example 1, except that in producing the polarizing film, the compound represented by general formula (9) was not added to the cleaning bath and the potassium iodide concentration was adjusted to 3.6 wt %; and in producing the pseudo-image display device, a 200 μm-thick acrylic acid monomer-free adhesive was attached to the viewing-side protective film surface before placing it in an 80°C hot air oven to produce a pseudo-image display panel (a laminate having a polarizing film with double-sided adhesive layers).

[0072] <Comparative Example 1> A polarizing film, a polarizing film, and a pseudo-image display device (laminate) were produced in the same manner as in Example 1, except that in the production of the polarizing film, the compound represented by general formula (9) was not added to the cleaning bath and the potassium iodide concentration was adjusted to 3.6 wt %, and in the production of the pseudo-image display device, the pseudo-image display panel was not subjected to aging treatment by being left in a hot air oven at 80°C for 2 hours.

[0073] <Comparative Example 2> A polarizing membrane, a polarizing film, and a pseudo-image display device (laminate) were prepared in the same manner as in Example 1, except that the compound represented by general formula (9) was not added to the cleaning bath in preparing the polarizing membrane.

[0074] <Comparative Example 3> In the preparation of the pseudo-image display device, a polarizing film, a polarizing film, and a pseudo-image display device (laminate) were prepared in the same manner as in Example 1, except that the pseudo-image display panel was not aged by being left in a hot air oven at 80°C for 2 hours.

[0075] <Comparative Example 4> A polarizing film, a polarizing film, and a pseudo-image display device (laminate) were produced in the same manner as in Example 1, except that in the production of the polarizing film, a 75 μm-thick polyvinyl alcohol film was used, the compound represented by general formula (9) was not added to the cleaning bath, and the potassium iodide concentration was adjusted to 4.0 wt %, and in the production of the pseudo-image display device, the film was left standing in a hot air oven at 90° C. for 5 hours. The polarizing film had a thickness of 28 μm.

[0076] The pseudo image display devices (laminates) of the examples and comparative examples obtained above were used to evaluate durability in high temperature environments. The results are shown in Table 1.

[0077] [Table 1] [Explanation of symbols]

[0078] 10: Polarizing film 11: Polarizing film 12 and 13: Transparent protective film 20, 30, 40, and 50: adhesive layer or adhesive layer 80: Front transparent component 90: Image display cell 100: Image display device

Claims

1. An image display device in which a front transparent member, a polarizing film, and an image display cell are provided in this order via a pressure-sensitive adhesive layer or an adhesive layer, An image display device characterized in that a laminate in which glass plates are bonded to both sides of the polarizing film via the pressure-sensitive adhesive layer or the adhesive layer has a change in single-unit transmittance of 0 to 3% and a change in single-unit hue b value of 0 to 4 NBS before and after a heat resistance test under conditions of 105°C and 500 hours.

2. 2. The image display device according to claim 1, wherein the polarizing film has a transparent protective film attached to at least one surface of the polarizing film via the pressure-sensitive adhesive layer or the adhesive layer.

3. 3. The image display device according to claim 1, wherein the polarizing film has an optical layer bonded to at least one surface of the polarizing film via the pressure-sensitive adhesive layer or the adhesive layer.

Images