Image display device

Abstract

Provided is an image display device, which is provided with a front surface transparent member, a polarizing film, and an image display unit in this order with an adhesive layer or a bonding agent layer interposed therebetween, and in which the amount of change in the monomer transmittance and the amount of change in the monomer hue b value are 0 to 3% and 0 to 4 NBS, respectively, before and after a heat resistance test at 105°C for 500 hours of a laminate in which a glass plate is attached to both surfaces of the polarizing film with the adhesive layer or the bonding agent layer interposed therebetween. The image display device is excellent in the inhibitory effect on the decrease in the monomer transmittance and the increase in the monomer hue b value of the polarizing film in a high-temperature environment.

Description

Technical Field

[0001] This invention relates to an image display device. Background Technology

[0002] Conventionally, polarizing films used in various image display devices such as liquid crystal displays and organic EL displays have employed dyed polyvinyl alcohol (PVA) films (containing dichroic substances such as iodine and dichroic dyes) to achieve both high transmittance and high polarization. These polarizing films are manufactured by subjecting the PVA film to various treatments in a bath, such as swelling, dyeing, crosslinking, and stretching, followed by cleaning and drying. Furthermore, these polarizing films are typically used in the form of polarizing films (polarizers) with a protective film such as cellulose triacetate bonded to one or both sides using an adhesive.

[0003] The aforementioned polarizing film is used in the form of a stacked polarizing film (optical laminate) by stacking other optical layers as needed. In addition, the aforementioned polarizing film or the aforementioned stacked polarizing film (optical laminate) is used in the form of an image display panel attached to an image display unit such as a liquid crystal cell or an organic EL element. Furthermore, the aforementioned image display panel is attached to a front surface transparent plate (window layer) or a touch panel on the visible side through an adhesive layer or a bonding agent layer, thereby making the aforementioned various image display devices for use (Patent Document 1).

[0004] In recent years, in addition to mobile devices such as mobile phones and tablets, such image display devices have also been used in vehicles such as car navigation systems and rearview monitors, and their applications are expanding. Along with this, compared to previous requirements, there is a further demand for high durability in more demanding environments (such as high-temperature environments) for the aforementioned polarizing films and the aforementioned stacked polarizing films, leading to the development of polarizing films and image display devices designed to ensure such durability (Patent Documents 2-3).

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2014-102353

[0008] Patent Document 2: Japanese Patent Publication No. 2012-516468

[0009] Patent Document 3: Japanese Patent Application Publication No. 2018-101117 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] In the aforementioned automotive image display devices, the development of autonomous driving technology in recent years has led to the proliferation of irregularly shaped and larger displays. With these changes in display design, there is a growing demand for methods to further improve the durability of polarizing films in high-temperature environments.

[0012] In view of the above, the object of the present invention is to provide an image display device that effectively suppresses the decrease in monomer transmittance and the increase in monomer hue b value of the polarizing film in a high-temperature environment.

[0013] Problem Solving Methods

[0014] That is, the present invention relates to an image display device, wherein a front surface transparent member, a polarizing film, and an image display unit are sequentially disposed therebetween an adhesive layer or a bonding agent layer. Before and after a heat resistance test at 105°C for 500 hours, the change in the single-unit transmittance of the laminate in which glass plates are bonded to both sides of the polarizing film through the adhesive layer or the bonding agent layer is 0 to 3%, and the change in the single-unit hue b value is 0 to 4 NBS.

[0015] The effects of the invention

[0016] The exact mechanism of action of the image display device of the present invention is not fully understood, but it is presumed to be so. However, the present invention may be interpreted in a way that is not limited to this mechanism of action.

[0017] The image display device of the present invention comprises a front surface transparent member, a polarizing film, and an image display unit sequentially disposed between an adhesive layer or a bonding agent layer. Before and after a heat resistance test at 105°C for 500 hours, the change in the monomer transmittance of the laminate containing a glass plate bonded to both sides of the polarizing film between the adhesive layer or the bonding agent layer is 0-3%, and the change in the monomer hue b-value is 0-4 NBS. The glass plate corresponds to the front surface transparent member and the image display unit; therefore, the laminate corresponds to an analog image display device. Until now, a laminate (analog image display device) exhibiting a change in monomer transmittance of 0-3% and a change in monomer hue b-value of 0-4 NBS under the aforementioned heat resistance test conditions was unknown. On the other hand, in order to suppress the decrease in the transmittance of the polarizing film, for example, in the aforementioned Patent Document 1, it is described that after bonding a polarizing film with an adhesive layer on one side to an image display unit to form an image display panel, a heating (aging) treatment is performed to reduce the moisture content of the polarizing film (hereinafter also referred to as conventional aging treatment). In the present invention, it has been found that the moisture contained in the adhesive layer or adhesive layer provided on both sides of the polarizing film used to bond to the aforementioned front surface transparent member and image display unit affects the decrease in the transmittance of the polarizing film and the increase in the b-value of the polarizing film (high temperature durability) after the heat resistance test of the image display device. Therefore, by performing a heating (aging) treatment on the adhesive layer or adhesive layer on both sides of the polarizing film used to bond to the aforementioned front surface transparent member and image display unit, the high temperature durability of the polarizing film can be further improved. Furthermore, in this invention, in addition to the conventional aging treatment described above, by also including a water-soluble free radical scavenger in the polarizing film, free radicals generated can be captured and polyene formation suppressed even in high-temperature environments where the polarizing film is prone to polyene formation. Therefore, the high-temperature durability of the polarizing film can be further improved. In addition to the methods described above, this invention further improves the high-temperature durability of the polarizing film by increasing the potassium concentration. Attached Figure Description

[0018] Figure 1 This is a cross-sectional schematic diagram showing one manner of an image display device.

[0019] Figure 2 This is a cross-sectional schematic diagram showing one way of using a polarizing film.

[0020] Symbol Explanation

[0021] 10: Polarizing film

[0022] 11: Polarizing film

[0023] 12 and 13: Transparent protective film

[0024] 20, 30, 40, and 50: Adhesive layer or bonding agent layer

[0025] 80: Transparent component on the front surface

[0026] 90: Image display unit

[0027] 100: Image display device Detailed Implementation

[0028] Figure 1 This is a cross-sectional schematic diagram illustrating one embodiment of the image display device of the present invention. Figure 1 In the image display device 100, the front surface transparent member 80 is bonded to the polarizing film 10 through an adhesive layer or adhesive layer 20, and the image display unit 90 is bonded to the polarizing film 10 through an adhesive layer or adhesive layer 30.

[0029] Figure 2 This is a cross-sectional schematic diagram illustrating one embodiment of the polarizing film of the present invention. Figure 2 In the polarizing film 10, the polarizing film 11 and the transparent protective film 13 are bonded together with an adhesive layer or adhesive layer 50 in between, and the polarizing film 11 and the transparent protective film 12 are bonded together with an adhesive layer or adhesive layer 40 in between.

[0030] The image display device of the present invention comprises a front surface transparent member, a polarizing film, and an image display unit arranged sequentially with an adhesive layer or a bonding agent layer in between. Before and after a heat resistance test at 105°C for 500 hours, the change in the single-unit transmittance of the laminate in which glass plates are bonded to both sides of the polarizing film with the adhesive layer or the bonding agent layer in between is 0 to 3%, and the change in the single-unit hue b value is 0 to 4 NBS.

[0031] <Polarizing film>

[0032] The polarizing film of the present invention comprises a polarizing film formed by adsorbing dichroic substances such as iodine and dichroic dyes onto a polyvinyl alcohol film and orienting them. From the viewpoint of the initial polarization performance of the polarizing film, an iodine-based polarizing film containing iodine as the aforementioned dichroic substance is preferred.

[0033] The aforementioned polyvinyl alcohol (PVA) films can be used without particular limitation, and are obtained by dispersing and adsorbing dichroic substances such as iodine and dichroic dyes in the visible light region. Examples of materials for the aforementioned PVA films include polyvinyl alcohol or its derivatives. Examples of PVA derivatives include: polyvinyl formal, polyvinyl acetal; olefins such as ethylene and propylene; and derivatives obtained by modifying unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, their alkyl esters, and acrylamide. The average degree of polymerization of the aforementioned PVA is preferably about 100 to 10,000, more preferably about 1,000 to 10,000, and even more preferably about 1,500 to 4,500. Furthermore, the degree of saponification of the aforementioned PVA is preferably about 80 to 100 mol%, more preferably about 95 mol% to 99.95 mol%. It should be noted that the aforementioned average degree of polymerization and degree of saponification can be determined based on JIS K 6726.

[0034] From the viewpoint of suppressing the decrease in monomer transmittance and the increase in monomer hue b-value of the polarizing film in high-temperature environments, the aforementioned polarizing film may contain a water-soluble free radical scavenger. From the viewpoint of easy migration to the moisture in the polarizing film, the aforementioned water-soluble free 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 at least 2 parts by weight in 100 parts by weight of water at 25°C, and even more preferably at least 5 parts by weight in 100 parts by weight of water at 25°C. The aforementioned water-soluble free radical scavenger can be used alone or in combination of two or more.

[0035] It is presumed that the aforementioned water-soluble free radical scavenger can suppress polyene formation in polarizing films under high-temperature conditions. Examples of such water-soluble free radical scavengers include compounds with free radical scavenging functions such as hindered phenols, hindered amines, phosphorus compounds, sulfur compounds, benzotriazoles, benzophenones, hydroxylamines, salicylates, and triazines. From the viewpoint of the types of free radicals generated in the polarizing film, compounds having nitryl radicals or nitryl groups are preferred as such water-soluble free radical scavengers.

[0036] As for the compounds containing nitryl radicals or nitryl groups mentioned above, from the viewpoint of having relatively stable free radicals at room temperature and in air, N-hydroxyl radical compounds (containing CN(-C)-O) can be cited as examples. · Compounds with functional groups (O) · (This refers to oxygen free radicals), and well-known compounds can also be used. Examples of N-hydroxyl radical compounds include compounds with organic groups having the following structures.

[0037] [Chemical Formula 1]

[0038]

[0039] (In general formula (1), R) 1 R represents oxygen free radicals. 2 ~R 5 The number of hydrogen atoms or alkyl groups with 1 to 10 carbon atoms can be independently represented (n represents 0 or 1). It should be noted that the left side of the dashed part in general formula (1) represents any organic group.

[0040] Examples of compounds having the above-mentioned organic groups include compounds represented by the following general formulas (2) to (5).

[0041] [Chemical Formula 2]

[0042]

[0043] (In general formula (2), R) 1 ~R 5 And n has the same meaning as above, R 6 (This indicates a hydrogen atom, an alkyl group, an acyl group, or an aryl group with 1 to 10 carbon atoms; n represents 0 or 1.)

[0044] [Chemical Formula 3]

[0045]

[0046] (In general formula (3), R) 1 ~R 5 And n has the same meaning as above, R 7 and R 8 (Independently representing a hydrogen atom, an alkyl group, an acyl group, or an aryl group having 1 to 10 carbon atoms.)

[0047] [Chemical Formula 4]

[0048]

[0049] (In general formula (4), R) 1 ~R 5 And n has the same meaning as above, R 9 ~R 11 Independently representing a hydrogen atom, an alkyl group, acyl group, amino group, alkoxy group, hydroxyl group, or aryl group having 1 to 10 carbon atoms.

[0050] [Chemical Formula 5]

[0051]

[0052] (In general formula (5), R) 1 ~R 5 And n has the same meaning as above, R 12(This refers to a hydrogen atom, or an alkyl, amino, alkoxy, hydroxyl, or aryl group having 1 to 10 carbon atoms.)

[0053] In the above general formulas (1) to (5), from the perspective of ease of acquisition, R 2 ~R 5 Preferably, it is an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms. Furthermore, in the above general formula (2), from the viewpoint of ease of acquisition, R... 6 Preferably, it is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, more preferably a hydrogen atom. Furthermore, from the viewpoint of ease of acquisition, R is preferred in the above general formula (3). 7 and R 8 Independently, it is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, more preferably a hydrogen atom. Furthermore, in the above general formula (4), from the viewpoint of ease of acquisition, R... 9 ~R 11 Preferably, it is an alkyl group having 1 to 10 hydrogen atoms. Furthermore, in the above general formula (5), from the viewpoint of ease of acquisition, R... 12 Preferably, it is hydroxyl, amino, or alkoxy. In the above general formulas (1) to (5), from the viewpoint of ease of acquisition, n is preferably 1.

[0054] In addition, examples of the aforementioned N-hydroxyl compounds include those described in Japanese Patent Application Publication No. 2003-64022, Japanese Patent Application Publication No. 11-222462, Japanese Patent Application Publication No. 2002-284737, and International Publication No. 2016 / 047655.

[0055] In addition, the following compounds can be cited as examples of compounds having nitrocellulose radicals or nitrocellulose groups.

[0056] [Chemical Formula 6]

[0057]

[0058] (In general formula (6), R represents a hydrogen atom, an alkyl group, an acyl group, or an aryl group with 1 to 10 carbon atoms.)

[0059] [Chemical Formula 7]

[0060]

[0061] [Chemical Formula 8]

[0062]

[0063] Furthermore, from the viewpoint of being able to efficiently capture free radicals generated in the polarizing film, the molecular weight of the aforementioned water-soluble free radical scavenger is preferably 1000 or less, more preferably 500 or less, and even more preferably 300 or less.

[0064] When the polarizing film contains the water-soluble free radical scavenger, from the viewpoint of suppressing the decrease in monomer transmittance and the increase in monomer hue b value of the polarizing film in a high-temperature environment, the content of the water-soluble free radical scavenger is preferably 0.005% by weight or more, more preferably 0.01% by weight or more, even more preferably 0.1% by weight or more, and 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.

[0065] Furthermore, from the viewpoint of suppressing the decrease in monomer transmittance and the increase in monomer hue b-value of the polarizing film in high-temperature environments, the potassium concentration of the aforementioned polarizing film can be increased. When increasing the potassium concentration, the potassium concentration is preferably 0.3% by weight or more, more preferably 0.35% by weight or more, and even more preferably 0.4% by weight or more. Moreover, from the viewpoint of suppressing changes in reflected hue in high-temperature environments, the potassium concentration is preferably 0.8% by weight or less, more preferably 0.6% by weight or less in the aforementioned polarizing film.

[0066] The aforementioned polarizing film is obtained using existing polarizing film manufacturing methods, such as by performing optional swelling and cleaning processes on the aforementioned polyvinyl alcohol film, and at least performing dyeing, crosslinking, and stretching processes. When the aforementioned polarizing film contains the aforementioned water-soluble free radical scavenger, the treatment bath in any one or more of the aforementioned swelling, cleaning, dyeing, crosslinking, and stretching processes must contain the water-soluble free radical scavenger. Furthermore, to increase the potassium concentration of the aforementioned polarizing film, the potassium concentration can be increased by adjusting the concentration of potassium-providing substances such as potassium iodide or potassium halides contained in any one or more of the aforementioned swelling, cleaning, dyeing, crosslinking, and stretching processes, as well as the treatment temperature and treatment time of each of the aforementioned treatment baths.

[0067] From the viewpoint of improving the initial polarization degree of the polarizing film, the thickness of the polarizing film is preferably 1 μm or more, more preferably 2 μm or more, and from the viewpoint of preventing panel warping, it is preferably 20 μm or less, more preferably 15 μm or less, further preferably 10 μm or less, and even more preferably 8 μm or less. In particular, in order to obtain a polarizing film with a thickness of about 8 μm or less, the following method for manufacturing a thin polarizing film can be applied, in which a laminate comprising a thermoplastic resin substrate and a polyvinyl alcohol resin layer formed on the thermoplastic resin substrate is used as the polyvinyl alcohol film.

[0068] The polarizing film (thin polarizing film) is obtained by existing polarizing film manufacturing methods, for example, by performing the following steps: forming a polyvinyl alcohol resin layer (PVA resin layer) containing polyvinyl alcohol resin (PVA resin) on one side of a strip-shaped thermoplastic resin substrate to prepare a laminate; while transporting the obtained laminate in the length direction, performing any insoluble treatment step, crosslinking treatment step, and cleaning treatment step on the laminate, and performing at least an assisted stretching treatment step in a gas atmosphere, a dyeing treatment step, and a stretching treatment step in an aqueous solution step. When the polarizing film contains the aforementioned water-soluble free radical scavenger, the treatment bath in any one or more of the aforementioned insoluble treatment step, crosslinking treatment step, cleaning treatment step, dyeing treatment step, and stretching treatment step in an aqueous solution step may contain the aforementioned water-soluble free radical scavenger. In addition, when increasing the potassium concentration of the polarizing film, the potassium concentration of the polarizing film can be increased by adjusting the concentration of potassium-providing substances such as potassium iodide or potassium halide in the treatment bath of any one or more of the above-mentioned insoluble treatment process, the above-mentioned crosslinking treatment process, the above-mentioned cleaning treatment process, the above-mentioned dyeing treatment process, and the above-mentioned stretching treatment process in aqueous solution, as well as the treatment temperature and treatment time of each of the above-mentioned treatment baths.

[0069] The aforementioned polarizing film typically has a transparent protective film bonded to at least one side of the polarizing film, separated by an adhesive layer or bonding agent layer.

[0070] <Adhesive layer>

[0071] As the adhesive forming the adhesive layer described above, various adhesives used in polarizing films can be applied, such as rubber adhesives, acrylic adhesives, silicone adhesives, urethane adhesives, vinyl alkyl ether adhesives, polyvinyl alcohol adhesives, polyvinylpyrrolidone adhesives, polyacrylamide adhesives, and cellulose adhesives. Among these, acrylic adhesives are preferred. The aforementioned acrylic adhesives contain acrylic polymers as the base polymer, and examples include the acrylic adhesives described in, for instance, Japanese Patent Application Publication No. 2017-75998.

[0072] The acrylic polymer in the aforementioned acrylic adhesive uses alkyl (meth)acrylate monomer units as the main backbone. As the alkyl (meth)acrylate, alkyl (meth)acrylates with 1 to 20 carbon atoms in the alkyl group can be suitably used, and the content of this alkyl (meth)acrylate is preferably 40% by weight or more, more preferably 60% by weight or more, relative to the total amount of monomer components constituting the base polymer. Furthermore, from the viewpoint of being able to adjust the adhesive properties, nitrogen-containing monomer units, hydroxyl-containing monomer units, etc., may also be included. In addition, to form a crosslinked structure in the adhesive layer, a crosslinking agent can be used; for example, isocyanate crosslinking agents, epoxy crosslinking agents, etc., can be used. Commonly used crosslinking agents include zopyridine crosslinking agents, carbodiimide crosslinking agents, and metal chelate crosslinking agents. The amount of crosslinking agent used is typically 10 parts by weight or less, preferably 5 parts by weight or less, relative to 100 parts by weight of the base polymer.

[0073] From the perspective of adjusting adhesive strength, silane coupling agents, terpene tackifiers, styrene tackifiers, phenol tackifiers, rosin tackifiers, epoxy tackifiers, and other tackifiers can be added to the above adhesives. Additionally, from the perspective of improving lightfastness, ultraviolet absorbers can be added. Besides the components listed above, additives such as plasticizers, softeners, deterioration inhibitors, fillers, colorants, antioxidants, surfactants, and antistatic agents can be used in the adhesives without impairing their properties.

[0074] Examples of methods for forming the adhesive layer include: applying the adhesive to a diaphragm or similar material that has undergone a peeling treatment and drying it to form an adhesive layer, and then transferring it to a polarizing film or similar material; or applying the adhesive to a polarizing film or similar material and drying it to form an adhesive layer. The thickness of the adhesive layer is not particularly limited, but is, for example, about 1 to 100 μm, preferably about 2 to 50 μm.

[0075] <Adhesive layer>

[0076] As the adhesive for forming the adhesive layer described above, various adhesives used in polarizing films can be applied, such as isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latexes, and waterborne polyesters. These adhesives are typically used in the form of adhesives formed from aqueous solutions (waterborne adhesives) and contain 0.5 to 60% by weight of solid components. Among these, polyvinyl alcohol adhesives are preferred, and polyvinyl alcohol adhesives containing acetylacetyl groups are more preferred.

[0077] The aforementioned water-based adhesive may contain a crosslinking agent. As the crosslinking agent, a compound typically used is one having at least two functional groups in one molecule that are reactive with the polymer or other components constituting the adhesive. Examples include: alkylene diamines; isocyanates; epoxy compounds; aldehydes; amino-formaldehydes such as hydroxymethylurea and hydroxymethyl melamine. The amount of crosslinking agent in the adhesive is typically about 10 to 60 parts by weight relative to 100 parts by weight of the polymer or other components constituting the adhesive.

[0078] In addition to the above, examples of adhesives that can be cured by active energy radiation, such as ultraviolet-cured adhesives and electron beam-cured adhesives, are also examples of adhesives that can be cured by active energy radiation. Examples of such active energy radiation-cured adhesives include (meth)acrylate adhesives. Examples of curing components in such (meth)acrylate adhesives include compounds having (meth)acryloyl groups and compounds having vinyl groups. Examples of compounds having (meth)acryloyl groups include chain-like alkyl (meth)acrylates with 1 to 20 carbon atoms, cycloalkyl (meth)acrylates, polycyclic alkyl (meth)acrylates, and other alkyl (meth)acrylates; hydroxyl-containing (meth)acrylates; glycidyl (meth)acrylates, and epoxy-containing (meth)acrylates. (Meth)acrylate adhesives may contain nitrogen-containing monomers such as hydroxyethyl (meth)acrylamide, N-hydroxymethyl (meth)acrylamide, N-methoxymethyl (meth)acrylamide, N-ethoxymethyl (meth)acrylamide, (meth)acrylamide, and (meth)acryloylmorpholine. (Meth)acrylate adhesives may also contain tripropylene glycol diacrylate, 1,9-nonanediol diacrylate, tricyclodecanediethanol diacrylate, cyclic trimethylolpropane methyl acetal acrylate, and di... Multifunctional monomers such as alkyl glycol diacrylate and EO-modified diglycerol tetraacrylate are used as crosslinking components. Additionally, compounds with epoxy groups or oxocyclic butyl groups can also be used as cationic polymerization curing adhesives. There are no particular limitations on compounds with epoxy groups, as long as they have at least two epoxy groups within the molecule; various commonly known curing epoxy compounds can be used.

[0079] The aforementioned adhesives may also contain suitable additives as needed. Examples of such additives include: silane coupling agents, titanium coupling agents, and other coupling agents; ethylene oxide and other adhesion promoters; ultraviolet absorbers; deterioration inhibitors; dyes; processing aids; ion scavengers; antioxidants; tackifiers; fillers; plasticizers; leveling agents; foaming inhibitors; antistatic agents; heat stabilizers; and hydrolysis stabilizers.

[0080] The adhesive coating can be applied to either the transparent protective film side (or the functional layer side described later) or the polarizing film side, or to both sides. After bonding, a drying process is performed to form an adhesive layer made of the coated and dried layer. After the drying process, ultraviolet light or an electron beam can be applied as needed. The thickness of the adhesive layer is not particularly limited. When using water-based adhesives, it is preferably about 30 to 5000 nm, more preferably about 100 to 1000 nm. When using ultraviolet-curing adhesives or electron beam-curing adhesives, it is preferably about 0.1 to 100 μm, more preferably about 0.5 to 10 μm.

[0081] <Transparent Protective Film>

[0082] There are no particular limitations on the aforementioned transparent protective film, and various transparent protective films used in polarizing films can be used. As materials constituting the aforementioned transparent protective film, thermoplastic resins with excellent transparency, mechanical strength, thermal stability, moisture barrier properties, and isotropy can be used, for example. Examples of such thermoplastic resins include: cellulose ester resins such as cellulose triacetate, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, polyethersulfone resins, polysulfone resins, polycarbonate resins, nylon, polyamide resins such as aromatic polyamides, polyimide resins, polyolefin resins such as polyethylene, polypropylene, and ethylene-propylene copolymers, (meth)acrylic resins, cyclic or cyclic polyolefin resins with a norbornene structure (norbornene resins), polyaryl ester resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. Furthermore, the aforementioned transparent protective film can be a cured layer formed from thermosetting resins such as (meth)acrylic acid, urethane, acrylate urethane, epoxy, and silicone, or ultraviolet-curable resins. Among these, cellulose ester resins, polycarbonate resins, (meth)acrylic resins, cyclic polyolefin resins, and polyester resins are preferred.

[0083] The thickness of the aforementioned transparent protective film can be appropriately determined. Generally speaking, from the perspectives of strength, processability, operability, and thinness, it is preferably about 1 to 500 μm, more preferably about 1 to 300 μm, and even more preferably about 5 to 100 μm.

[0084] When the above-mentioned transparent protective film is attached to both sides of the above-mentioned polarizing film, the transparent protective film on both sides may be the same or different.

[0085] The aforementioned transparent protective film can use a phase retardation plate having a frontal phase difference of 40 nm or more and / or a thickness direction phase difference of 80 nm or more. Typically, the frontal phase difference is controlled within the range of 40–200 nm, and the thickness direction phase difference is typically controlled within the range of 80–300 nm. When a phase retardation plate is used as the aforementioned transparent protective film, the phase retardation plate also functions as a transparent protective film, thus enabling thinner designs.

[0086] Examples of phase retardation plates include: birefringent films formed by unidirectional or bidirectional stretching of polymer raw materials, alignment films of liquid crystal polymers, and phase retardation plates formed by supporting an alignment layer of liquid crystal polymers with a film. The thickness of the phase retardation plate is not particularly limited, typically ranging from 20 to 150 μm. It should be noted that the aforementioned phase retardation plates can be bonded to transparent protective films that do not possess phase retardation properties.

[0087] The aforementioned transparent protective film may contain any suitable additives such as UV absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-coloring agents, flame retardants, antistatic agents, pigments, and colorants. In particular, the inclusion of UV absorbers in the aforementioned transparent protective film can improve the lightfastness of the polarizing film.

[0088] When the aforementioned transparent protective film is adhered to the visible side of the polarizing film, considering the durability of the polarizing film under high temperature and high humidity conditions, the preferred moisture permeability is 600 g / (m²). 2 • 24h or less, more preferably 400g / (m 2 • 24h or less. When the above-mentioned transparent protective film is laminated to the image display unit side of the polarizing film, from the viewpoint of production efficiency in the drying process after lamination, the moisture permeability is preferably 50 g / (m²). 2 • 24h or more, more preferably 100g / (m 2 • 24h or more, and the preferred moisture permeability is 1000g / (m³) 2 • 24h or less, more preferably 600g / (m 2 • 24h or less. In addition, it should be noted that the moisture permeability can be calculated as follows: According to the moisture permeability test (cup method) of JIS Z0208, a sample cut into 60mm diameter pieces is placed in a moisture permeability cup containing about 15g of calcium chloride, and placed in a constant temperature machine at 40°C and 90% RH. The weight increase of calcium chloride before and after 24 hours is measured and calculated.

[0089] Functional layers such as a hard coating layer, anti-reflective layer, anti-adhesion layer, diffusion layer, or anti-glare layer can be provided on the side of the aforementioned transparent protective film that is not bonded to the polarizing film. It should be noted that the aforementioned functional layers such as the hard coating layer, anti-reflective layer, anti-adhesion layer, diffusion layer, and anti-glare layer can be either the protective film itself or layers different from the protective film.

[0090] The polarizing film and the transparent protective film, or the polarizing film and the functional layer, are usually bonded together with the adhesive layer or the bonding agent layer in between.

[0091] The aforementioned transparent protective film and the aforementioned polarizing film, or the aforementioned polarizing film and the aforementioned functional layer, can be stacked together with interlayers such as surface modification treatment layer, easy-to-adhere layer, blocking layer, and refractive index adjustment layer.

[0092] Examples of surface modification treatments for forming the above-mentioned surface modified layer include: corona treatment, plasma treatment, primer treatment, saponification treatment, etc.

[0093] Examples of easy-adhesive agents used to form the aforementioned easy-adhesive layer include: resins comprising various resins having a polyester backbone, polyether backbone, polycarbonate backbone, polyurethane backbone, silicone backbone, polyamide backbone, polyimide backbone, polyvinyl alcohol backbone, etc. The aforementioned easy-adhesive layer can typically be pre-formed onto a protective film, and the easy-adhesive layer side of this protective film is laminated to the polarizing film via the aforementioned adhesive layer or adhesive layer.

[0094] The aforementioned barrier layer is a layer that functions to prevent impurities such as oligomers and ions dissolved from a transparent protective film from migrating (invading) into the polarizing film. The barrier layer can be any layer that is transparent and can prevent impurities dissolved from a transparent protective film, etc. Examples of materials forming the barrier layer include: urethane prepolymer forming materials, cyanoacrylate forming materials, epoxy forming materials, etc.

[0095] The aforementioned refractive index adjustment layer is provided to suppress the decrease in transmittance caused by reflections between layers with different refractive indices, such as the transparent protective film and the polarizing film. Examples of refractive index adjustment materials forming this layer include forming materials comprising various resins and additives such as silica-based, acrylic-based, acrylic-styrene-based, and melamine-based resins.

[0096] In addition, the aforementioned polarizing film may have an optical layer attached to at least one side of the polarizing film, with the adhesive layer or the bonding agent layer in between.

[0097] The aforementioned optical layer is not particularly limited. For example, one or more layers of reflective plates, semi-transparent plates, phase retardation plates (including 1 / 2 and 1 / 4 wave plates), viewing angle compensation films, and other optical layers sometimes used in the formation of liquid crystal display devices can be used. As for the aforementioned polarizing film, examples include reflective polarizing films or semi-transparent polarizing films formed by further stacking reflective plates or semi-transparent reflective plates on the aforementioned polarizing film; elliptical polarizing films or circular polarizing films formed by further stacking phase retardation plates on the aforementioned polarizing film; wide-viewing-angle polarizing films formed by further stacking viewing angle compensation films on the aforementioned polarizing film; and polarizing films formed by further stacking brightness-enhancing films on the aforementioned polarizing film.

[0098] In order to bond with image display units such as liquid crystal cells and organic EL elements, as well as other components such as front surface transparent plates and touch panels on the visible side, the adhesive layer or the bonding agent layer can be pre-applied on one or both sides of the polarizing film.

[0099] For the purpose of preventing contamination, the exposed surface of the aforementioned adhesive layer or bonding agent layer is preferably temporarily covered by an adhesive diaphragm until it is put into actual use. This prevents contamination of the adhesive layer or bonding agent layer under normal processing conditions. As the diaphragm, a diaphragm can be used that is coated with a suitable thin layer such as plastic film, rubber sheet, paper, cloth, nonwoven fabric, mesh, foam sheet, metal foil, or their laminates using a suitable release agent such as silicone, long-chain alkyl, fluorine, or molybdenum sulfide, as needed.

[0100] <Front surface transparent component>

[0101] The front surface transparent member of the present invention is a front surface transparent member disposed on the viewable side of an image display unit. Examples of such front surface transparent members include: a front surface transparent plate (window layer), a touch panel, etc. As the front surface transparent plate, a front surface transparent plate with suitable mechanical strength and thickness can be used. Such a transparent plate can be, for example, a transparent resin plate such as acrylic resin or polycarbonate resin, or a glass plate. As the touch panel, various touch panels such as resistive film type, capacitive type, optical type, ultrasonic type, etc., glass plates with touch sensor functions, transparent resin plates, etc., can be used. When using a capacitive type touch panel as the front surface transparent member, it is preferable to provide a front surface transparent plate made of glass or a transparent resin plate closer to the viewable side than the touch panel.

[0102] <Image Display Unit>

[0103] Examples of image display units in this invention include liquid crystal units (LCDs) and organic EL units (OLEDs). The LCD can be any of the following: a reflective LCD that utilizes external light, a transmissive LCD that utilizes light from a backlight or other light source, or a semi-transmissive / semi-reflective LCD that utilizes both external light and light from a light source. In the case where the LCD utilizes light from a light source, the image display device (LCD) also provides a polarizing film and a light source on the side of the LCD opposite to the viewable side. The polarizing film on the light source side is preferably bonded to the LCD via a suitable adhesive layer. The driving method for the LCD can be any type, such as VA mode, IPS mode, TN mode, STN mode, or bent alignment (π-type).

[0104] As the aforementioned organic EL unit, an organic EL unit in which a light emitter (organic electroluminescent emitter) is formed by sequentially stacking a transparent electrode, an organic light-emitting layer, and a metal electrode on a transparent substrate can be used. The aforementioned organic light-emitting layer is a stack of various organic thin films and can employ various layer structures, including, for example: a stack of a hole injection layer formed from a triphenylamine derivative and a light-emitting layer formed from a fluorescent organic solid such as anthracene; a stack of these light-emitting layers and an electron injection layer formed from a dinaphthalene derivative; or a stack of a hole injection layer, a light-emitting layer, and an electron injection layer.

[0105] When forming the image display device described above, after the image display unit and the polarizing film are bonded together to form the image display panel, and before it is bonded to the front surface transparent member, from the viewpoint of suppressing the decrease in the transmittance of individual polarizers and the increase in the b-value of individual polarizers in a high-temperature environment, the image display panel can be subjected to a heat (aging) treatment. In this case, by performing a heat (aging) treatment on the adhesive layer or bonding agent layer on both sides of the polarizing film used to bond to the front surface transparent member and the image display unit, the decrease in transmittance of individual polarizers and the increase in the b-value of individual polarizers in a high-temperature environment can be further suppressed. The heating conditions in the heat (aging) treatment are not particularly limited as long as they can sufficiently reduce the moisture content contained in the adhesive layer or bonding agent layer provided on both sides of the polarizing film and the polarizing film. For example, the heating temperature is preferably about 70°C to 90°C, more preferably about 75°C to 85°C. In addition, the heating time is preferably about 30 minutes to 5 hours, more preferably about 1 hour to 3 hours. Furthermore, when performing heat (aging) treatment with adhesive or bonding agent layers on both sides of the polarizing film, high moisture permeability of the adhesive or bonding agent layers is effective. Conversely, when performing heat (aging) treatment with adhesive or bonding agent layers on one side, low moisture content of the adhesive or bonding agent layers stacked on the rear side (the adhesive or bonding agent layers on the other side) is effective. It should be noted that when forming the above-described image display device, the above-described heat (aging) treatment can be performed after the above-described front surface transparent member is bonded to the above-described polarizing film, and then the image display unit can be attached.

[0106] Example

[0107] The present invention will be described in more detail below with reference to specific embodiments, but the present invention is not limited to these embodiments.

[0108] <Example 1>

[0109] <Production of Polarizing Film>

[0110] A polyvinyl alcohol (PVA) film with an average degree of polymerization of 2400, a saponification degree of 99.9 mol%, and a thickness of 45 μm was prepared. The PVA film was immersed in a swelling bath (water bath) at 30°C for 30 seconds between rollers with different circumferential speeds to induce swelling, while simultaneously stretching it 2.2 times in the transport direction (swelling process). Next, it was immersed in a dyeing bath at 30°C (an iodine aqueous solution prepared by mixing iodine and potassium iodide in a 1:7 weight ratio relative to 100 parts by weight of water) for 30 seconds, adjusting the concentration to achieve a given transmittance for the polarizing film. During this dyeing process, the original PVA film (completely unstretched in the transport direction) was used as a reference and stretched 3.3 times in the transport direction (dyeing process). Next, the dyed polyvinyl alcohol film was immersed in a crosslinking bath at 40°C (an aqueous solution of 3.5 wt% boric acid, 3.0 wt% potassium iodide, and 3.6 wt% zinc sulfate) for 28 seconds, and the original polyvinyl alcohol film was stretched to 3.6 times its original length in the transport direction (crosslinking process). Further, the obtained polyvinyl alcohol film was immersed in a stretching bath at 64°C (an aqueous solution of 4.5 wt% boric acid, 5.0 wt% potassium iodide, and 5.0 wt% zinc sulfate) for 60 seconds, and the original polyvinyl alcohol film was stretched to 6.0 times its original length in the transport direction (stretching process). Then, it was immersed in a cleaning bath at 27°C (an aqueous solution of 2.3 wt% potassium iodide and 1.0 wt% of the compound represented by the following general formula (9) as a water-soluble free radical scavenger) for 10 seconds (cleaning process). The cleaned polyvinyl alcohol film was dried at 40°C for 30 seconds to produce a polarizing film. The polarizing film contains 0.31% potassium by weight, 0.3% by weight of the compound represented by the following general formula (9), and has a thickness of 18 μm.

[0111] [Chemical Formula 9]

[0112]

[0113] <Method for determining potassium content (wt%) in polarizing film>

[0114] For the polarizing film, the fluorescence X-ray intensity (kcps) of potassium was measured using a fluorescence X-ray analyzer (Rigaku Corporation, trade name "ZSX100E", measuring diameter: ψ10mm). On the other hand, the thickness (μm) of the polarizing film was measured using a spectrophotometer (PEACOCK Corporation, trade name "DG-205"). The potassium content (wt%) was calculated based on the obtained fluorescence X-ray intensity and thickness using the following formula. It should be noted that "2.99" below refers to the coefficient of a calibration curve derived from measuring the fluorescence X-ray intensity (kcps) of a sample with known thickness (μm) and potassium concentration (wt%) (e.g., a PVA-type resin film with a certain amount of KI added).

[0115] Potassium content (wt%) in the polarizing film = 2.99 × (X-ray fluorescence intensity of potassium) / (thickness of polarizing film)

[0116] <Method for determining the content (wt%) of water-soluble free radical scavengers in polarizing films>

[0117] Take about 20 mg of polarizing membrane for quantitative analysis. Dissolve it in 1 mL of water by heating, then dilute with 4.5 mL of methanol. Filter the resulting extract through a membrane filter and determine the concentration of water-soluble free radical scavenger in the filtrate using HPLC (Waters ACQUITY UPLC H-class Bio).

[0118] <Fabrication of Polarizing Film>

[0119] As an adhesive, an aqueous solution containing polyvinyl alcohol resin with acetylacetyl groups (average degree of polymerization 1200, degree of saponification 98.5 mol%, degree of acetylacetylation 5 mol%) and hydroxymethyl melamine in a weight ratio of 3:1 was used. Using this adhesive and a roller laminator, a 30 μm thick transparent protective film (made by Nippon Shokubai, with a moisture permeability of 125 g / (m²)) formed from (meth)acrylic resin (a modified acrylic polymer with a lactone ring structure) was laminated onto one side (image display unit side) of the obtained polarizing film. 2 • 24h)), and on the other side (visible side), a transparent protective film with a thickness of 48μm and HC is formed on a cellulose triacetate membrane (Fuji Film Manufacturing, trade name "TJ40UL") (humidity permeability is 300g / (m²)). 2 After 24 hours, the film was dried in an oven (at 90°C for 10 minutes) to produce a polarizing film with a transparent protective film laminated on both sides.

[0120] <Preparation of Acrylic Adhesives>

[0121] A monomer mixture containing 99 parts of butyl acrylate and 1 part of 4-hydroxybutyl acrylate was added to a four-necked flask equipped with a stirring blade, thermometer, nitrogen inlet tube, and condenser. Further, relative to 100 parts of the monomer mixture (solid component), 0.1 parts of 2,2'-azobisisobutyronitrile (2,2'-azobisisobutyronitrile) as a polymerization initiator and 100 parts of ethyl acetate were added together. Nitrogen gas was introduced while stirring slowly to purge the mixture. The liquid temperature in the flask was maintained at approximately 55°C, and the polymerization reaction was carried out for 8 hours to prepare a solution of an acrylic polymer with a weight-average molecular weight (Mw) of 1.8 million. Then, relative to 100 parts of the solid component of the obtained acrylic polymer solution, 0.02 parts of isocyanate crosslinking agent (manufactured by Tosoh Corporation, trade name "Takenate D110N", trimethylolpropane / phenylenedimethyl diisocyanate adduct) and 0.2 parts of silane coupling agent (manufactured by Shin-Etsu Chemical Industry Co., Ltd., trade name "X-41-1056") were added to prepare an acrylic adhesive composition solution.

[0122] <Fabrication of Polarizing Film with Adhesive Layer>

[0123] The solution of the acrylic adhesive composition obtained above was coated onto one side of a polyethylene terephthalate film (Mitsubishi Chemical Polyester Film, trade name "MRF38", separator) treated with an organosilicon release agent, so that the thickness of the adhesive layer after drying was 20 μm. The film was then dried at 90°C for 1 minute, forming an adhesive layer on the surface of the separator. Next, the adhesive layer formed on the separator was transferred to the protective film surface of the polarizing film on the image display unit side, thus creating a polarizing film with an adhesive layer.

[0124] <Fabrication of Analog Image Display Device (Laminated Component)>

[0125] The polarizing film with adhesive layer obtained above was cut into 150×45mm pieces with the absorption axis of the polarizing film parallel to its long side. A glass plate (EG-XG, 165×50mm, 0.7mm thick, manufactured by Hiraoka Special Glass Co., Ltd.) was bonded to the glass plate through the adhesive layer. The plate was then autoclaved at 50°C and 0.5MPa for 15 minutes to produce an analog image display panel (a laminate with a polarizing film on one side with adhesive layer). The analog image display panel was then aged in an 80°C hot air oven for 2 hours, removed from the oven, and left to stand at 23°C and 55% for 1 hour. Then, other glass panels were bonded to the protective film side of the visible side through a 200μm thick acrylic monomer-free adhesive (LUCIACS CS98210, manufactured by Nitto Denko Co., Ltd.). The laminate was then autoclaved at 50°C and 0.5MPa for 15 minutes to produce an analog image display device (a laminate).

[0126] <Durability Evaluation in High-Temperature Environments>

[0127] The simulated image display device (layer) obtained above was placed in a hot air oven at 105°C for 500 hours, and the monomer transmittance (ΔTs) and monomer hue b-value (Δb) before and after heating were measured. The monomer transmittance and monomer hue b-value were measured using a spectrophotometer (Otsuka Electronics Co., Ltd., LPF-200). The monomer transmittance was obtained by visibility correction using a 2-degree field of view (C light source) according to JlS Z 8701-1982. It should be noted that the measurement wavelength was 380–780 nm (in 5 nm intervals).

[0128] ΔTs(%)=Ts 500 -Ts0

[0129] Δb(NBS)=b 500 -b0

[0130] Where Ts0 and b0 are the initial (before heating) monomer transmittance and monomer hue b value, respectively. 500 and b 500 These are the monomer transmittance and monomer hue b value after heating for 500 hours. ΔTs (%) is preferably 0% or more and 3% or less, more preferably 0% or more and 2% or less. Δb (NBS) is preferably 0NBS or more and 4NBS or less, more preferably 0NBS or more and 3NBS or less. The results are shown in Table 1.

[0131] <Example 2>

[0132] In the fabrication of the polarizing film, no compound represented by general formula (9) was added to the cleaning bath, the concentration of potassium iodide was adjusted to 3.6% by weight, and in the fabrication of the analog image display device, before being placed in a hot air oven at 80°C, an acrylic monomer-free adhesive with a thickness of 200 μm was bonded to the protective film surface on the visible side to fabricate an analog image display panel (a laminate of polarizing films with adhesive layers on both sides). Otherwise, the polarizing film, the polarizing film, and the analog image display device (laminated body) were fabricated by the same operation as in Example 1.

[0133] <Comparative Example 1>

[0134] In the fabrication of the polarizing film, no compound represented by general formula (9) was added to the cleaning bath, the concentration of potassium iodide was adjusted to 3.6% by weight, and in the fabrication of the analog image display device, the analog image display panel was not subjected to aging treatment by being left to stand in a hot air oven at 80°C for 2 hours. Otherwise, the polarizing film, the polarizing film, and the analog image display device (laminated assembly) were fabricated by the same operation as in Example 1.

[0135] <Comparative Example 2>

[0136] In the fabrication of the polarizing film, no compound represented by general formula (9) was added to the cleaning bath. Otherwise, the polarizing film, the polarizing film, and the analog image display device (stack) were fabricated by the same operation as in Example 1.

[0137] <Comparative Example 3>

[0138] In the fabrication of the analog image display device, the analog image display panel was not subjected to aging treatment by being left to stand in an 80°C hot air oven for 2 hours. Otherwise, the polarizing film, the polarizing film, and the analog image display device (laminated assembly) were fabricated using the same procedures as in Example 1.

[0139] <Comparative Example 4>

[0140] In the fabrication of the polarizing film, a 75 μm thick polyvinyl alcohol film was used. No compound represented by general formula (9) was added to the cleaning bath. The potassium iodide concentration was adjusted to 4.0% by weight. In the fabrication of the analog image display device, it was left to stand in a hot air oven at 90°C for 5 hours. Otherwise, the polarizing film, the polarizing film, and the analog image display device (laminated structure) were fabricated using the same procedures as in Example 1. It should be noted that the thickness of the polarizing film was 28 μm.

[0141] The above-described evaluation of the durability in high-temperature environments was conducted using the analog image display device (layer) obtained from the embodiments and comparative examples. The results are shown in Table 1.

[0142]

Claims

1. An image display device, comprising a front surface transparent member, a polarizing film, and an image display unit sequentially disposed therebetween an adhesive layer or bonding agent layer. The polarizing film is a polarizing film formed by the adsorption and orientation of dichroic substances on a polyvinyl alcohol film. This polarizing film contains a water-soluble free radical scavenger, which is a compound containing nitryl radicals or nitryl groups. Before and after a heat resistance test at 105°C for 500 hours, the change in the monomer transmittance of the laminated body with a glass plate bonded to both sides of the polarizing film through the adhesive layer or the bonding agent layer is 0~3%, and the change in the monomer hue b value is 0~4NBS.

2. The image display device according to claim 1, wherein, The polarizing film has a transparent protective film bonded to at least one side of the polarizing film, separated from the adhesive layer or the bonding agent layer.

3. The image display device according to claim 1 or 2, wherein, The polarizing film has an optical layer bonded to at least one side therebetween, separated by the adhesive layer or the bonding agent layer.

4. The image display device according to claim 1 or 2, wherein, The polarizing film contains more than 0.4% by weight and less than 0.6% by weight of potassium.

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