JP2020124898A - Bonded structure - Google Patents

Abstract

To provide a bonded structure in which delayed bubbles are prevented from occurring under a high-temperature environment.SOLUTION: The bonded structure includes an optical transparent adhesive sheet 10 that has a first acrylic adhesive layer 11 that forms a first surface, a thermosetting polyurethane layer 12, and a second acrylic adhesive layer 13 that forms a second surface, in this order, and a polycarbonate substrate bonded to the first surface. The thickness of the optical transparent adhesive sheet 10 and the thickness of the polycarbonate substrate meet a relationship (1) or (2). (1) The thickness of the optical transparent adhesive sheet 10 is 0.3 mm or more and 1.0 mm or less, and the thickness of the polycarbonate substrate is 1.0 mm or less and (2) the thickness of the optical transparent adhesive sheet 10 is more than 1.0 mm and 2.0 mm or less, and the thickness of the polycarbonate substrate is 2.0 mm or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a laminated structure joined by using an optical transparent pressure-sensitive adhesive sheet.

An optically transparent adhesive (OCA: Optically Clear Adhesive) sheet is a transparent adhesive sheet used for bonding optical members. As an example of the use of the OCA sheet, it may be used in a display device for joining a display panel such as a liquid crystal module and a cover panel provided on the outermost surface of the display device. The space between the display panel and the cover panel is filled with the OCA sheet, so that the visibility of the screen of the display panel can be improved.

As a document disclosing the prior art in the field related to the OCA sheet, for example, Patent Document 1 can be cited. Patent Document 1 discloses a first crosslinked pressure-sensitive adhesive layer having a first main surface and a second main surface and having a first surface energy, and a first main surface and a second main surface. A second siloxane-based pressure-sensitive adhesive layer having a surface and having a second surface energy, wherein the first main surface of the second siloxane-based pressure-sensitive adhesive layer is the first At least one surface comprising a second siloxane-based pressure-sensitive adhesive layer in contact with the second major surface of the crosslinked pressure-sensitive adhesive layer of, and a microstructured surface comprising aligned microstructures A release liner having the microstructured surface in contact with the second major surface of the second siloxane-based pressure sensitive adhesive layer, the first surface comprising: Disclosed is a double-sided adhesive article having an energy lower than the second surface energy.

By the way, with the diversification of display devices, the use of a resin panel as a cover panel, which is more advantageous in design, safety (prevention of scattering when broken) and price than a glass panel which has been commonly used in the past, has been recently adopted. Consideration is being made. Therefore, as the OCA sheet, one suitable for joining with the resin panel is required.

Japanese Patent Publication No. 2018-507926

In order to realize an OCA sheet suitable for bonding a display panel and a touch panel body, the present inventors have laminated a first acrylic pressure-sensitive adhesive layer, a thermosetting polyurethane layer and a second acrylic pressure-sensitive adhesive layer in a multilayer structure. We have been developing OCA sheets that have The OCA sheet having this multilayer structure has excellent flexibility due to the thermosetting polyurethane layer and excellent adhesiveness due to the first and second acrylic pressure-sensitive adhesive layers, and therefore has excellent peelability against shear stress. It is possible to exhibit excellent properties such as difficulty in performing.

However, when the bonded structure produced by bonding the OCA sheet having the multilayer structure and the resin panel is put into a high temperature environment in a reliability test, the bonding structure is immediately after bonding at the bonding interface between the OCA sheet and the resin panel. In some cases, bubbles that do not exist and are generated later, that is, delayed bubbles are generated.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a bonded structure in which delayed bubbles are prevented in a high temperature environment.

The bonded structure of the present invention has a first acrylic pressure-sensitive adhesive layer that constitutes the first surface, a thermosetting polyurethane layer, and a second acrylic pressure-sensitive adhesive layer that constitutes the second surface in this order. An optical transparent pressure-sensitive adhesive sheet and a polycarbonate substrate adhered to the first surface are provided, and the thickness of the optical transparent pressure-sensitive adhesive sheet and the thickness of the polycarbonate substrate have the following relationship (1) or (2). It is characterized by satisfying.
(1) The thickness of the optically transparent pressure-sensitive adhesive sheet is 0.3 mm or more and 1.0 mm or less, and the thickness of the polycarbonate substrate is 1.0 mm or less (2) The thickness of the optically transparent pressure-sensitive adhesive sheet is more than 1.0 mm 2 0.0 mm or less, and the thickness of the polycarbonate substrate is 2.0 mm or less

The thickness of the optically transparent pressure-sensitive adhesive sheet is preferably equal to or greater than the thickness of the polycarbonate substrate.

The thermosetting polyurethane layer is preferably thicker than the first acrylic pressure-sensitive adhesive layer and the second acrylic pressure-sensitive adhesive layer.

The thickness of the first acrylic pressure-sensitive adhesive layer is preferably 3 to 100 μm.

According to the bonded structure of the present invention, it is possible to prevent the generation of delayed bubbles in a high temperature environment.

It is sectional drawing which showed typically an example of the optically transparent adhesive sheet with which the laminated structure of this invention is equipped. It is a schematic diagram for demonstrating the evaluation method of adhesive force. It is sectional drawing which showed typically the structure of the bonding structure of this invention which has a bezel-on bonding structure.

The bonded structure of the present invention has a first acrylic pressure-sensitive adhesive layer that constitutes the first surface, a thermosetting polyurethane layer, and a second acrylic pressure-sensitive adhesive layer that constitutes the second surface in this order. An optical transparent pressure-sensitive adhesive sheet and a polycarbonate substrate adhered to the first surface are provided, and the thickness of the optical transparent pressure-sensitive adhesive sheet and the thickness of the polycarbonate substrate have the following relationship (1) or (2). It is characterized by satisfying.
(1) The thickness of the optically transparent pressure-sensitive adhesive sheet is 0.3 mm or more and 1.0 mm or less, and the thickness of the polycarbonate substrate is 1.0 mm or less (2) The thickness of the optically transparent pressure-sensitive adhesive sheet is more than 1.0 mm 2 0.0 mm or less and the thickness of the polycarbonate substrate is 2.0 mm or less

[Optical transparent adhesive sheet]
FIG. 1 is a cross-sectional view schematically showing an example of an optical transparent pressure-sensitive adhesive sheet included in the bonded structure of the present invention. The optically transparent adhesive sheet 10 shown in FIG. 1 comprises a first acrylic adhesive layer 11 forming a first surface (adhesive surface), a thermosetting polyurethane layer 12, and a second surface (adhesive surface). And a second acrylic pressure-sensitive adhesive layer 13 in this order. The thermosetting polyurethane layer 12 is preferably thicker than the first acrylic pressure-sensitive adhesive layer 11 and the second acrylic pressure-sensitive adhesive layer 13. By having such a laminated structure, even when the adherend is a resin panel, high adhesive force and cohesive force at the adhesive interface are obtained, and the adherend is deformed in accordance with expansion and contraction. can do.

<Acrylic adhesive layer>
The first acrylic pressure-sensitive adhesive layer 11 and the second acrylic pressure-sensitive adhesive layer 13 are layers containing an acrylic resin. The acrylic resin is obtained by curing an acrylic resin composition. The acrylic resin composition contains, for example, a (meth)acrylic acid ester-based polymer or a copolymer thereof (hereinafter, also referred to as a (meth)acrylic-based copolymer) and a crosslinking agent. There are things.

Examples of the (meth)acrylic copolymer include a copolymer of (meth)acrylic acid alkyl ester and a carboxyl group-containing monomer.

As the above-mentioned (meth)acrylic acid alkyl ester, a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 18 carbon atoms (CH ₂ =CR ¹ -COOR ² ; R ¹ is a hydrogen atom or a methyl group, and R is ² is an alkyl group having 1 to 18 carbon atoms), and the alkyl group preferably has 4 to 12 carbon atoms.

Examples of the (meth)acrylic acid alkyl ester having 1 to 18 carbon atoms in the alkyl group include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, and n-butyl. (Meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, octyl (meth)acrylate , Isooctyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, isodecyl (meth) acrylate, undeca (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate Can be mentioned. These may be used alone or in combination of two or more.

Examples of the carboxyl group-containing monomer include β-carboxyethyl (meth)acrylate, 5-carboxypentyl (meth)acrylic acid, mono(meth)acryloyloxyethyl succinate, and ω-carboxypolycaprolactone mono(meth). Carboxyl group-containing (meth)acrylates such as acrylates; acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid, and maleic acid. These may be used alone or in combination of two or more.

As the cross-linking agent, for example, a component capable of causing a cross-linking reaction with a cross-linkable functional group derived from a cross-linkable functional group-containing monomer, which the (meth)acrylic copolymer has, can be used, Examples thereof include isocyanate compounds, metal chelate compounds, and epoxy compounds. The above crosslinking agents may be used alone or in combination of two or more.

The first acrylic adhesive layer 11 and the second acrylic adhesive layer 13 may contain polyurethane. The polyurethane is obtained by curing a polyurethane composition. Examples of the polyurethane composition include a thermosetting polyurethane composition. As the thermosetting polyurethane composition, the same thermosetting polyurethane composition used for the thermosetting polyurethane layer 12 described later can be used.

It is preferable that the first acrylic pressure-sensitive adhesive layer 11 and the second acrylic pressure-sensitive adhesive layer 13 have an adhesive force to glass at room temperature (23° C.) of 5 N/25 mm or more. In addition, in this specification, an adhesive force means the measured value in a 180 degree peeling test. Details of the test method of the 180° peel test will be described later. The adhesive strength at room temperature is more preferably 20 N/25 mm or more. The upper limit of the adhesive strength at room temperature is not particularly limited, but is 100 N/25 mm, for example.

FIG. 2 is a schematic diagram for explaining an evaluation method of adhesive force. The 180° peel test will be described with reference to FIG. First, the optically transparent pressure-sensitive adhesive sheet 10 cut into a length of 75 mm and a width of 25 mm is used as a test piece. One surface of this test piece is attached to a slide glass 31 having a length of 75 mm and a width of 25 mm, and the pressure is maintained at 0.4 MPa for 30 minutes, and the optical transparent adhesive sheet 10 and the slide glass 31 are attached to each other. Next, as shown in FIG. 2A, a PET sheet 32 is attached to the surface of the optical transparent pressure-sensitive adhesive sheet 10 opposite to the slide glass 31. Then, after leaving it at a predetermined temperature for a certain period of time, as shown in FIG. 2B, the PET sheet 32 is pulled in a direction of 180°, and the optical transparent pressure-sensitive adhesive sheet 10 is peeled at the interface with the slide glass 31, and slides. The adhesive force of the optically transparent adhesive sheet 10 to the glass 31 is measured. As the PET sheet, for example, a 125 μm-thick PET sheet (“Melinex (registered trademark) S” manufactured by Teijin DuPont Films) can be used.

The thickness of the first acrylic pressure-sensitive adhesive layer 11 and the second acrylic pressure-sensitive adhesive layer 13 is preferably 3 to 100 μm. If the thickness is less than 3 μm, there is a possibility that sufficient adhesive force to sufficiently suppress delayed bubbles may not be obtained. On the other hand, when the thickness exceeds 100 μm, there is a possibility that flexibility (step-following property) to the extent that it can be deformed following the step existing on the surface of the adherend on which the optical transparent pressure-sensitive adhesive sheet is stuck may not be obtained. .. Further, when the optical transparent pressure-sensitive adhesive sheet is used for bonding substrates having different elasticity when the environment changes, such as bonding a glass substrate and a resin substrate, the optical transparent pressure-sensitive adhesive sheet is It may not follow the dimensional change of the base material when the environment changes and may peel off. The thickness of the first acrylic pressure-sensitive adhesive layer 11 and the second acrylic pressure-sensitive adhesive layer 13 is more preferably 3 to 40 μm.

<Thermosetting polyurethane layer>
The thermosetting polyurethane layer 12 is a layer containing thermosetting polyurethane. Since the thermosetting polyurethane layer 12 contains the thermosetting polyurethane and is flexible, the optically transparent pressure-sensitive adhesive sheet used in the present invention stretches well and is very difficult to be torn when tensile stress is applied. Therefore, it can be peeled off without leaving any adhesive residue. In addition, since the thermosetting polyurethane layer 12 contains thermosetting polyurethane, the dielectric constant is high, and the optical transparent pressure-sensitive adhesive sheet used in the present invention can have a high capacitance. Therefore, the optically transparent pressure-sensitive adhesive sheet used in the present invention is suitable for sticking a capacitive touch panel. Further, since the thermosetting polyurethane can be formed into a film without using a solvent, the thermosetting polyurethane layer 12 can be made thick.

The thermosetting polyurethane is preferably not acrylic-modified, and it is preferable that the main chain does not include a site derived from an acrylate ester, a methacrylate ester, or the like. When the thermosetting polyurethane is modified with acrylic, it becomes hydrophobic, so that water easily aggregates at high temperature and high humidity. This aggregation of water may cause whitening, foaming, etc., and impair optical characteristics. Therefore, when the thermosetting polyurethane is not acrylic-modified, it is possible to prevent deterioration of optical characteristics due to whitening, foaming, etc. under high temperature and high humidity. In the thermosetting polyurethane, the total amount of the monomer units derived from the polyol component and the monomer units derived from the polyisocyanate component is 80 mol% or more of the monomer units constituting the entire thermosetting polyurethane. Preferably.

The thermosetting polyurethane composition preferably contains a polyol component and a polyisocyanate component. As the above-mentioned polyol component and the above-mentioned polyisocyanate component, those that are liquid at room temperature (23°C) can be used, and a thermosetting polyurethane can be obtained without using a solvent. Other components such as a tackifier can be added to either the polyol component or the polyisocyanate component, and are preferably added to the polyol component. Since it is not necessary to remove the solvent when producing the thermosetting polyurethane layer 12, a uniform sheet can be formed thick. Further, the thermosetting polyurethane layer 12 can maintain optical characteristics even when formed thick, and can sufficiently suppress coloring and foaming (generation of bubbles at the interface with the adherend). Furthermore, the thermosetting polyurethane layer 12 is excellent in impact resistance because it can be made thick and is flexible. The optically transparent pressure-sensitive adhesive sheet provided with the thermosetting polyurethane layer 12 can be used for bonding a transparent member having a transparent conductive film as a surface layer to a cover panel, and when another member is used, a display panel, or It can also be used for bonding a transparent member having a transparent conductive film as a surface layer to another member. When the optical transparent pressure-sensitive adhesive sheet having the thermosetting polyurethane layer 12 is used for bonding a display panel and a transparent member (touch panel) having a transparent conductive film as a surface layer, it is formed by a bezel arranged on the outer edge of the display panel. The steps can be covered with an optically transparent adhesive sheet.

The polyol component is not particularly limited, and examples thereof include polyether polyol, polycaprolactone polyol, polycarbonate polyol, polyester polyol and the like. These may be used alone or in combination of two or more.

The polyol component preferably has an olefin skeleton. That is, it is preferable that the main chain is composed of polyolefin or its derivative. Examples of the polyol component having an olefin skeleton include polybutadiene-based polyols such as 1,2-polybutadiene polyol, 1,4-polybutadiene polyol, 1,2-polychloroprene polyol, and 1,4-polychloroprene polyol, and polyisoprene. Examples thereof include system polyols and their double bonds saturated with hydrogen or halogen. Further, the polyol component may be a polyol obtained by copolymerizing a polybutadiene-based polyol or the like with an olefin compound such as styrene, ethylene, vinyl acetate or an acrylic ester, or a hydrogenated product thereof. The polyol component may have a linear structure or a branched structure. The above polyol component may be used alone or in combination of two or more. The polyol component used in the polyurethane preferably contains a polyol component having an olefin skeleton in an amount of 80 mol% or more, and more preferably consists only of a polyol component having an olefin skeleton.

The polyisocyanate component is not particularly limited, it is possible to use a conventionally known polyisocyanate, a hydrophilic polyisocyanate having a hydrophilic unit, and either one of the hydrophobic polyisocyanate having no hydrophilic unit, Alternatively, both may be used. Incidentally, the hydrophilic polyisocyanate having the hydrophilic unit is not one having improved hydrophilicity only by a structure derived from an isocyanate group such as an isocyanurate structure or a biuret structure, and a functional group for enhancing hydrophilicity (hydrophilicity A carboxylic acid unit) is added to the polyisocyanate. By including a hydrophilic unit in the polyisocyanate component, an effect of suppressing whitening due to moisture absorption can be obtained.

An ethylene oxide unit is preferable as the hydrophilic unit. The content of the ethylene oxide unit is preferably 0.1% by weight or more and 20% by weight or less based on the entire thermosetting polyurethane composition. If the content is less than 0.1% by weight, the effect of suppressing whitening may not be sufficiently obtained. If the content is more than 20% by weight, the compatibility with the low-polarity olefinic polyol component, tackifier, plasticizer, etc. may decrease, and thus optical properties such as haze may deteriorate. The content of the ethylene oxide unit is more preferably 0.1 to 5% by weight. If the content exceeds 5% by weight, the amount of moisture absorption in the high temperature and high humidity environment may be too large.

Examples of hydrophilic units other than the ethylene oxide unit include units containing a carboxylic acid group, an alkali metal base of carboxylic acid, a sulfonic acid group, an alkali metal base of sulfonic acid, a hydroxyl group, an amide group, an amino group, and the like. More specifically, polyacrylic acid, an alkali metal salt of polyacrylic acid, a sulfonic acid group-containing copolymer, an alkali metal salt of a sulfonic acid group-containing copolymer, polyvinyl alcohol, polyacrylamide, carboxymethyl cellulose, an alkali metal of carboxymethyl cellulose Examples thereof include salts and polyvinylpyrrolidone.

The polyisocyanate component is preferably a modified polyisocyanate obtained by reacting an aliphatic and/or alicyclic polyisocyanate having an isocyanate group with an ether compound having an ethylene oxide unit. By using an aliphatic and/or alicyclic polyisocyanate, coloring and discoloration are less likely to occur, and the transparency of the optically transparent pressure-sensitive adhesive sheet can be more reliably ensured for a long period of time. In addition, the modified polyisocyanate component can suppress whitening due to the action of the hydrophilic part (ethylene oxide unit) and the hydrophobic part (other units) by reacting with an ether compound having an ethylene oxide unit. By the action of, the compatibility with low polarity tackifier, plasticizer, etc. can be exhibited.

The thermosetting polyurethane composition preferably has an α ratio (the number of OH groups derived from the polyol component/the number of NCO groups derived from the polyisocyanate component) of 1 or more. When the α ratio is less than 1, the blending amount of the polyisocyanate component is excessive with respect to the blending amount of the polyol component, so that the thermosetting polyurethane becomes hard and the flexibility required for the optical transparent pressure-sensitive adhesive sheet is increased. It may be difficult to secure. When the thermosetting polyurethane layer 12 has low flexibility, it is not possible to cover irregularities and steps existing on the bonding surface, particularly when bonding optical members such as a touch panel. Further, if the α ratio is less than 1, the adhesive strength required for the optically transparent adhesive sheet may not be secured. The α ratio is preferably less than 2.0. When the α ratio is 2.0 or more, the thermosetting polyurethane composition may not be sufficiently cured.

The thermosetting polyurethane composition may further contain a tackifier (tackifier). The tackifier is an additive that is added to improve the adhesive strength, and is usually an amorphous oligomer having a molecular weight of several hundreds to several thousands, and is a liquid or solid thermoplastic resin at room temperature.

The thermosetting polyurethane composition may further contain a plasticizer. The plasticizer is not particularly limited as long as it is a compound used for imparting flexibility to the thermosetting polyurethane, but it is preferable to include a carboxylic acid plasticizer from the viewpoint of compatibility and weather resistance.

The thermosetting polyurethane composition may further contain a catalyst. The catalyst is not particularly limited as long as it is a catalyst used for urethanization reaction, and examples thereof include organotin compounds such as di-n-butyltin dilaurate, dimethyltin dilaurate, dibutyltin oxide and octane tin; organotitanium compounds Organic zirconium compounds; carboxylic acid tin salts; carboxylic acid bismuth salts; amine catalysts such as triethylenediamine.

The thermosetting polyurethane may further contain a silane coupling agent. The silane coupling agent preferably has an epoxy group or isocyanurate structure, and more preferably has an epoxy group or isocyanurate structure and an alkoxy group. Examples of the alkoxy group include a methoxy group and an ethoxy group. The silane coupling monomer having an epoxy group is not particularly limited, and examples thereof include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropyltriethoxysilane, and 3-glycidyl. Examples include cidoxypropylmethyldiethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. The silane coupling monomer having an isocyanurate structure is not particularly limited, and examples thereof include tris-(trimethoxysilylpropyl) isocyanurate.

The thermosetting polyurethane layer 12 obtained by using the silane coupling agent having an epoxy group or an isocyanurate structure firmly adheres to the first acrylic pressure-sensitive adhesive layer 11 and the second acrylic pressure-sensitive adhesive layer 13. Therefore, the interface between the first acrylic pressure-sensitive adhesive layer 11 and the thermosetting polyurethane layer 12 and the interface between the thermosetting polyurethane layer 12 and the second acrylic pressure-sensitive adhesive layer 13 can be effectively prevented from peeling off. Therefore, according to the optical transparent pressure-sensitive adhesive sheet of the present invention, by providing the first acrylic pressure-sensitive adhesive layer 11 and the second acrylic pressure-sensitive adhesive layer 13, a high pressure-sensitive adhesive force to an adherend can be exhibited, and It is possible to prevent adhesive residue from occurring during peeling.

The content of the silane coupling agent is preferably 0.2% by weight or more and 3% by weight or less based on the thermosetting polyurethane composition. When the content of the silane coupling agent is less than 0.2% by weight, the effect of preventing the adhesive residue from being added due to the addition of the silane coupling agent may not be sufficiently obtained. When the content of the silane coupling agent exceeds 3% by weight, the silane coupling agent may segregate on the surface of the optically transparent pressure-sensitive adhesive sheet, which may reduce the adhesive strength of the optically transparent pressure-sensitive adhesive sheet.

The thermosetting polyurethane composition, as long as it does not impair the required properties of the optical transparent pressure-sensitive adhesive sheet, if necessary, various additives such as colorants, stabilizers, antioxidants, anti-mildew agents, flame retardants, etc. It may be added.

The storage elastic modulus (G′ _{85° C.} ) of the thermosetting polyurethane layer 12 at _{85° C.} is preferably 1.0×10 ⁴ Pa or more and 15.0×10 ⁴ Pa or less. When G'85 _°C of the thermosetting polyurethane layer 12 is less than 1.0 x 10 ⁴ Pa, internal foaming is likely to occur due to being too soft and peeling is likely to occur in the heat cycle test. On the other hand, if the G'85 _°C of the thermosetting polyurethane layer 12 exceeds 15.0 x 10 ⁴ Pa, the flexibility decreases, and sufficient step followability cannot be obtained. Also, when used for bonding substrates having different stretchability due to environmental changes, they cannot follow the dimensional changes between the substrates and peel. The more preferable lower limit of G′ _{85° C.} of the thermosetting polyurethane layer 12 is 2.0×10 ⁴ Pa, and the more preferable upper limit thereof is 14.0×10 ⁴ Pa.

The storage elastic modulus (G′ _{30° C.} ) of the thermosetting polyurethane layer 12 at _{30° C.} may be, for example, 8×10 ⁴ Pa or more and 33×10 ⁴ Pa or less. The preferable lower limit of G′ _{30° C.} of the thermosetting polyurethane layer 12 is 12.0×10 ⁴ Pa, and the preferable upper limit thereof is 25.0×10 ⁴ Pa.

The storage elastic modulus can be measured using, for example, a viscoelasticity measuring device “Physica MCR301” manufactured by Anton Paar Germany GmbH. The measurement conditions are that PP12 is used as a measurement plate, strain is 0.1%, frequency is 1 Hz, cell temperature is 25°C to 100°C (heating rate 3°C/min), and the measured value at the target temperature is adopted. You can

The loss tangent (tan δ _{85° C.} ) of the thermosetting polyurethane layer 12 at _{85° C.} may be, for example, 0.2 or more and 0.8 or less. The preferable lower limit of tan δ _{85° C.} of the thermosetting polyurethane layer 12 is 0.3, and the preferable upper limit thereof is 0.5.

The loss tangent (tan δ _{30° C.} ) of the thermosetting polyurethane layer 12 at _{30° C.} may be, for example, 0.3 or more and 0.85 or less. The preferable lower limit of tan δ _{30° C.} of the thermosetting polyurethane layer 12 is 0.35, and the preferable upper limit thereof is 0.6.

The loss tangent can be measured under the same measurement conditions using the same measuring device as for the storage elastic modulus, and the measured value at the target temperature can be adopted.

The thickness of the thermosetting polyurethane layer 12 is preferably 100 to 2000 μm. When the thickness is less than 100 μm, the flexibility of the optical transparent pressure-sensitive adhesive sheet as a whole is lowered, and when one surface of the optical transparent pressure-sensitive adhesive sheet is attached to the surface of the optical member, the optical transparent pressure-sensitive adhesive sheet allows the optical member to be coated. In some cases, it is not possible to cover the unevenness or the step existing on the surface of the above, and it may not be possible to bond the other surface of the optically transparent pressure-sensitive adhesive sheet and the surface of another optical member with sufficient adhesive force. When the thickness exceeds 2000 μm, optical characteristics such as haze and total light transmittance may not be sufficiently obtained. A more preferable lower limit of the thickness of the thermosetting polyurethane layer 12 is 200 μm, and a still more preferable lower limit thereof is 250 μm. The more preferable upper limit of the thickness of the thermosetting polyurethane layer 12 is 1500 μm, and the further preferable upper limit thereof is 1000 μm.

The optical transparent pressure-sensitive adhesive sheet 10 may have the first acrylic pressure-sensitive adhesive layer 11, the thermosetting polyurethane layer 12, and the second acrylic pressure-sensitive adhesive layer 13 in this order, and may further have other layers. Good. The first acrylic pressure-sensitive adhesive layer 11 and the second acrylic pressure-sensitive adhesive layer 13 may be located on the outermost surface of the optically transparent pressure-sensitive adhesive sheet 10 (the surface in contact with the adherend). The first acrylic pressure-sensitive adhesive layer 11 and the thermosetting polyurethane layer 12 are preferably in contact with each other, and the second acrylic pressure-sensitive adhesive layer 13 and the thermosetting polyurethane layer 12 are preferably in contact with each other.

<Optical transparent adhesive sheet>
The optical transparent pressure-sensitive adhesive sheet 10 preferably has a haze of 1% or less, and more preferably 0.5% or less, in order to ensure the performance as an optical transparent pressure-sensitive adhesive sheet. Further, the optical transparent pressure-sensitive adhesive sheet 10 preferably has a total light transmittance of 90% or more. The haze and the total light transmittance can be measured using, for example, a turbidimeter “HazeMeter NDH2000” manufactured by Nippon Denshoku Industries Co., Ltd. The haze is measured by the method according to JIS K 7136, and the total light transmittance is measured by the method according to JIS K 7361-1.

The method for laminating the first acrylic pressure-sensitive adhesive layer 11, the thermosetting polyurethane layer 12, and the second acrylic pressure-sensitive adhesive layer 13 in this order is not particularly limited. For example, the first acrylic pressure-sensitive adhesive layer 11, A method may be mentioned in which the second acrylic pressure-sensitive adhesive layer 13 and the thermosetting polyurethane layer 12 are individually prepared and then bonded together.

The method for producing the first acrylic pressure-sensitive adhesive layer 11 and the second acrylic pressure-sensitive adhesive layer 13 is not particularly limited. For example, a general-purpose film forming apparatus such as various coating apparatuses, bar coats, doctor blades, or the like for coating the acrylic resin composition may be used. A film method may be used. Alternatively, the first acrylic pressure-sensitive adhesive layer 11 and the second acrylic pressure-sensitive adhesive layer 13 may be produced by using a centrifugal molding method.

The method for producing the thermosetting polyurethane layer 12 is not particularly limited, and examples thereof include a method in which a thermosetting polyurethane composition is prepared and then the composition is thermoset by a conventionally known method while being molded, and preferably a polyol is used. The method includes a step of preparing the thermosetting polyurethane composition by stirring and mixing the components, the polyisocyanate component, and the tackifier, and a step of curing the thermosetting polyurethane composition.

As a specific example of the production method, first, a predetermined amount of tackifier is added to the polyol component, and the master batch is prepared by heating and stirring to dissolve. Subsequently, the obtained masterbatch, a polyol component, a polyisocyanate component, a silane coupling agent, and, if necessary, other components such as a catalyst are mixed and stirred with a mixer or the like to give a liquid or gel form. A thermosetting polyurethane composition is obtained. Immediately thereafter, the thermosetting polyurethane composition is put into a molding apparatus, and a curing reaction (crosslinking reaction) is performed while moving the thermosetting polyurethane composition while being sandwiched between the first and second release films. The thermosetting polyurethane composition is semi-cured to obtain a sheet integrated with the first and second release films. Then, the thermosetting polyurethane layer 12 is obtained by carrying out a crosslinking reaction for a certain period of time in a furnace.

[Polycarbonate substrate]
The polycarbonate substrate is not particularly limited, and a conventionally known plate-shaped member made of polycarbonate is preferably used. The polycarbonate substrate may be one that has been subjected to heat treatment (for example, 60° C. or higher) before being bonded to the optical transparent pressure-sensitive adhesive sheet. Further, a surface treatment such as plasma treatment may be applied to the surface of the polycarbonate base material in contact with the first surface.

[Lamination structure]
The laminated structure of the present invention may be any structure as long as it has a structure in which a polycarbonate substrate is adhered to the first surface of the optically transparent pressure-sensitive adhesive sheet. A glass base material or a resin base material may be bonded to the second surface of the optically transparent pressure-sensitive adhesive sheet. The resin constituting the resin base material is not particularly limited, and examples thereof include polycarbonate, polymethyl methacrylate resin (PMMA), triacetyl cellulose (TAC), and the like.

The thickness of the optically transparent pressure-sensitive adhesive sheet and the thickness of the polycarbonate substrate satisfy the following relationship (1) or (2). Moreover, it is preferable that the thickness of the optically transparent pressure-sensitive adhesive sheet and the thickness of the polycarbonate substrate satisfy the following relationship (3).
(1) The thickness of the optically transparent pressure-sensitive adhesive sheet is 0.3 mm or more and 1.0 mm or less, and the thickness of the polycarbonate substrate is 1.0 mm or less (2) The thickness of the optically transparent pressure-sensitive adhesive sheet is more than 1.0 mm 2 0.0 mm or less, and the thickness of the polycarbonate substrate is 2.0 mm or less (3) The thickness of the optically transparent pressure-sensitive adhesive sheet is equal to or more than the thickness of the polycarbonate substrate.

Generally, since polycarbonate is a material that easily absorbs moisture, when a structure in which a polycarbonate base material and an optical transparent pressure-sensitive adhesive sheet are bonded together is put into a high temperature environment, bubbles (delay Foam) was sometimes generated. On the other hand, in the present invention, since the polycarbonate substrate is adhered to the first surface constituted by the first acrylic pressure-sensitive adhesive layer, it exhibits high adhesive strength and suppresses the generation of delayed bubbles. You can Moreover, since the optically transparent pressure-sensitive adhesive sheet has a function of absorbing the outgas (moisture) released from the polycarbonate substrate, it is possible to prevent the outgas from being accumulated at the interface and causing delayed bubbles. As a result of the study by the present inventors, depending on the thickness of the polycarbonate substrate, by ensuring the thickness of the optically transparent pressure-sensitive adhesive sheet so as to satisfy the relationship of (1) or (2) above, it is possible to maintain a high temperature environment for a long time. It has been found that even if left unattended, the generation of delayed bubbles due to the outgas released from the polycarbonate substrate can be sufficiently prevented.

Further, in a high temperature and high humidity environment (for example, 85° C. and 85%), the moisture absorption of the polycarbonate base material is promoted, so that delayed bubbles are more likely to occur. On the other hand, depending on the thickness of the polycarbonate substrate, by ensuring the thickness of the optically transparent pressure-sensitive adhesive sheet so as to satisfy the relationship of (3) above, even if it is left for a long time in a high temperature and high humidity environment, It was found that the generation of delayed bubbles due to the outgas released from the polycarbonate substrate can be sufficiently prevented.

The lower limit of the thickness of the polycarbonate substrate is not particularly limited, but it is preferably 0.5 mm or more. When the thickness of the polycarbonate substrate is less than 0.5 mm, the outgas (moisture) released from the polycarbonate substrate is small. Therefore, the effect of suppressing delayed bubbles obtained by adjusting the thickness of the optically transparent pressure-sensitive adhesive sheet is compared. Get smaller.

When the thickness of the optically transparent pressure-sensitive adhesive sheet 10 is not uniform, as in the case where the bonding structure of the present invention has a bezel-on bonding structure to be described later, the relationship of (1), (2) and (3) above is satisfied. The thickness of the optically transparent pressure-sensitive adhesive sheet means the average thickness in the range where the optically transparent pressure-sensitive adhesive sheet and the polycarbonate substrate are superposed.

Further, when the polycarbonate substrate used in the present invention has been subjected to heat treatment or surface treatment, the contribution of the adjustment of the thickness of the optically transparent pressure-sensitive adhesive sheet in suppressing delayed bubbles is relatively small. there is a possibility. Therefore, from the viewpoint of enjoying the effects of the present invention, the polycarbonate base material used in the present invention is preferably an untreated product that has not been subjected to heat treatment or surface treatment.

The application of the bonded structure of the present invention is not particularly limited, and may be one in which a liquid crystal module and a cover panel are joined by an optical transparent adhesive sheet. The polycarbonate substrate may be the outermost member of the liquid crystal module or a cover panel. The visibility of the liquid crystal module can be improved by joining the liquid crystal module and the cover panel with an optically transparent adhesive sheet and eliminating the air layer existing between the liquid crystal module and the cover panel. When the liquid crystal module is arranged in a housing (bezel) having an opening in the display unit, the bezel is arranged on the outer edge of the liquid crystal module. Therefore, a step corresponding to the thickness of the bezel is formed. The method of joining the liquid crystal module and the cover panel by overlapping the optically transparent adhesive sheet not only in the center of the liquid crystal module but also in the area where the bezel is arranged is also called "bezel-on bonding". The bonding structure formed by the bezel-on bonding is also referred to as “bezel-on bonding structure”.

The optically transparent pressure-sensitive adhesive sheet used in the present invention is suitable for bezel-on bonding because it is flexible and can be formed into a thick film. The bonding structure of the present invention may have a bezel-on bonding structure, for example, a structure including an optical transparent pressure-sensitive adhesive sheet and a supporting member between a first base material and a second base material. Having, the supporting member has a step forming portion arranged on the outer edge of the first base material, the optical transparent pressure-sensitive adhesive sheet, the first base material and the second base material. It may include a thick film portion to be bonded and an end portion sandwiched between the step forming portion and the second base material. The polycarbonate substrate may be the first substrate or the second substrate.

FIG. 3 is a cross-sectional view schematically showing the structure of the bonded structure of the present invention having a bezel-on bonded structure. The laminated structure 50 shown in FIG. 3 has a configuration in which the optical transparent adhesive sheet 10 and the upper bezel (support member) 41 are provided between the first base material 51 and the second base material 52. However, for example, it may be a part of an electronic device such as a display device. The upper bezel 41 is integrated with the lower bezel 42 to form a housing (bezel) that houses the first base material 51.

In the laminated structure 50, the optically transparent pressure-sensitive adhesive sheet 10 includes a thick film portion that adheres the first base material 51 and the second base material 52, a step forming portion of the upper bezel 41, and the second base material 52. And an end sandwiched between and. Since the end portion of the optically transparent pressure-sensitive adhesive sheet 10 is sandwiched between the second base material 52 and the step forming portion of the upper bezel 41, it does not easily peel off. Moreover, since the optical transparent adhesive sheet 10 reaches the step forming portion of the upper bezel 41, the upper surface of the first base material 51 is entirely covered with the step forming portion of the upper bezel 41 or the optical transparent adhesive sheet 10. Therefore, moisture absorption of the first base material 51 can be prevented. When the polarizing plate is located on the upper surface of the first base material 51, moisture absorption of the polarizing plate can be prevented. When the polarizing plate absorbs moisture, the performance may be deteriorated quickly, or the moisture absorbed in a high temperature environment may evaporate to cause delayed bubbles.

The combination of the first base material 51 and the second base material 52 is not particularly limited, and for example, constitutes a display device such as a display panel, a touch panel (glass substrate with an ITO transparent conductive film), a cover panel (cover glass), or the like. Various members are included. The type of display panel is not particularly limited, and examples thereof include a liquid crystal panel and an organic electroluminescence panel (organic EL panel). Further, a polarizing plate, a retardation film or the like may be arranged on the surface of the display panel to which the optically transparent adhesive sheet 10 is attached. By bonding various members in the display device using the optically transparent pressure-sensitive adhesive sheet 10, it is possible to eliminate an air layer (air gap) in the display device and improve the visibility of the display screen. Further, when a polarizing plate is arranged, the optically transparent pressure-sensitive adhesive sheet 10 can effectively prevent the polarizing plate from absorbing moisture. A combination in which the first base material 51 is a display panel such as a liquid crystal module and the second base material 52 is a polycarbonate base material (cover panel) is suitable.

The upper bezel 41 is a frame-shaped member arranged around the optical transparent adhesive sheet 10 in a plan view, and at least a part of the upper bezel 41 is arranged on the outer edge of the first base material 51. The side surface of the portion (step forming portion) arranged on the outer edge of the first base material 51 forms a step. The shape of the side surface of the step forming portion is not particularly limited, and the side surface of the step forming portion may be perpendicular to the upper surface of the first base material 51. When the first base material 51 is a display panel, the upper bezel 41 is arranged in the frame area of the display device, but the first base material is placed so that the user of the display device cannot see the upper bezel 41. A light shielding portion 52A may be provided on the outer edge of 51. The material of the upper bezel 41 is not particularly limited, and examples thereof include metal and resin.

The thickness (size of the step) of the upper bezel 41 is not particularly limited, but is, for example, 200 to 1000 μm. When the thickness of the upper bezel 41 exceeds 200 μm, it is necessary to set the thickness of the optical transparent pressure-sensitive adhesive sheet 10 to 300 μm (0.3 mm) or more, so an optical transparent pressure-sensitive adhesive sheet thicker than a normal optical transparent pressure-sensitive adhesive sheet is used. To be

The thickness of the thick film portion of the optically transparent adhesive sheet 10 is 1.5 times or more, and more preferably 2 times or more, the thickness of the step forming portion of the upper bezel 41. As a result, a sufficient thickness can be secured at the end of the optically transparent pressure-sensitive adhesive sheet 10 sandwiched between the step forming portion of the upper bezel 41 and the second base material 52, and peeling of the end can be prevented. .. The thickness of the thick film portion of the optically transparent adhesive sheet 10 in the laminated structure 50 is substantially the same as the thickness of the optically transparent adhesive sheet 10 before being laminated. That is, the thickness of the optically transparent pressure-sensitive adhesive sheet 10 before being bonded is preferably 1.5 times or more, and more preferably 2 times or more the thickness of the upper bezel 41.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

(Example 1)
First, 75 parts by weight of a polyolefin polyol (“EPOL (registered trademark)” manufactured by Idemitsu Kosan Co., Ltd.) and 2.4 parts by weight of an IPDI (isophorone diisocyanate)-based polyisocyanate (“Desmodur I” manufactured by Sumika Bayer Urethane Co., Ltd.) Parts, 4.6 parts by weight of modified polyisocyanate containing ethylene oxide unit (“Coronate 4022” manufactured by Tosoh Corporation), 17 parts by weight of tackifier (“Imerb P-100” manufactured by Idemitsu Kosan Co., Ltd.), and catalyst (dilauric acid). 1 part by weight of dimethyltin) was stirred and mixed using a reciprocating rotary stirrer agitator to prepare a thermosetting polyurethane composition having an α ratio of 1.60. In the thermosetting polyurethane composition, the mixing ratio (molar ratio) of the IPDI polyisocyanate (A) and the modified polyisocyanate (B) was A:B=2:1.

In addition, "Coronate 4022" manufactured by Tosoh Corporation is obtained by reacting a polyisocyanate starting from hexamethylene diisocyanate and/or hexamethylene diisocyanate monomer with an ether polyol having an average of 3 or more ethylene oxide units per molecule. It was obtained.

After that, while conveying the obtained thermosetting polyurethane composition in a state of being sandwiched by a pair of release films (PET film having a surface subjected to a release treatment), a furnace temperature of 50 to 90° C. and a furnace time It was crosslinked and cured under the condition of several minutes to obtain a sheet with a release film. After that, a cross-linking reaction was performed for 10 to 15 hours with a heating device to prepare a thermosetting polyurethane layer having a release film on both surfaces. The thickness of the thermosetting polyurethane layer was 250 μm.

The loss tangent (tan δ) of the thermosetting polyurethane layer was measured using a viscoelasticity measuring device “Physica MCR301” manufactured by Anton Paar Germany GmbH. PP12 was used as the measurement plate, and the measurement conditions were strain 0.1%, frequency 1 Hz, and cell temperature 25° C. to 100° C. (heating rate 3° C./min). The measured loss tangent at 30° C. was 0.35.

On the other hand, 0.15 parts by weight of an epoxy-based curing agent (“E-AX” by Soken Chemical Industry Co., Ltd.) was added to 99.85 parts by weight of an acrylic resin (“SK1838” manufactured by Soken Chemical Industry Co., Ltd.) to obtain an acrylic resin. A resin composition was prepared. The obtained acrylic resin composition was applied to a release film with a comma coater and dried in a drying oven at 80 to 120° C., and then the release film was placed on the coated surface. Then, the curing was completed by heating at 40° C. for 1 week to prepare an acrylic pressure-sensitive adhesive layer. The thickness of the acrylic pressure-sensitive adhesive layer was 25 μm.

Then, two sheets of the acrylic adhesive layer with the release film and one sheet of the thermosetting polyurethane layer with the release film were prepared. One release film was peeled off from the first acrylic pressure-sensitive adhesive layer with a release film, and a thermosetting polyurethane layer was laminated on the surface of the first acrylic pressure-sensitive adhesive layer from which the release film was peeled off. Further, one release film is peeled off from the second acrylic adhesive layer with release film, and the first acrylic adhesive layer (first acrylic adhesive layer) of the thermosetting polyurethane layer is laminated. A second acrylic pressure-sensitive adhesive layer (second acrylic pressure-sensitive adhesive layer) was laminated on the surface opposite to the surface on which the above-mentioned processing was performed. Thereby, a release sheet, a first acrylic pressure-sensitive adhesive layer, a thermosetting polyurethane layer, a second acrylic pressure-sensitive adhesive layer, and a release film were laminated in this order to produce a laminated sheet. The thickness of the optically transparent pressure-sensitive adhesive sheet including the first acrylic pressure-sensitive adhesive layer, the thermosetting polyurethane layer and the second acrylic pressure-sensitive adhesive layer was 0.3 mm.

Optics with the release film peeled onto a transparent glass substrate (soda glass manufactured by Matsunami Glass Industry Co., Ltd.) by vacuum-bonding one surface of the optical transparent adhesive sheet from which the release film was peeled off with a pressing pressure of 0.15 MPa. A 0.5 mm thick polycarbonate base material (“resin sheet PCTSH” manufactured by MISUMI Group Headquarters) was vacuum-bonded to the other surface of the transparent adhesive sheet at a pressing pressure of 0.15 MPa. By this bonding, a bonded structure in which a polycarbonate substrate and a glass substrate were bonded with an optical transparent pressure-sensitive adhesive sheet was obtained.

(Examples 2 to 16 and Comparative Examples 1 to 14)
As shown in Table 1 below, except that the thickness of the optically transparent adhesive sheet (OCA) and the thickness of the polycarbonate substrate were changed, Examples 2 to 16 and Comparative Examples 1 to 14 were performed in the same manner as Example 1. Each of the bonded structures according to the above was produced.

The thickness of the optically transparent pressure-sensitive adhesive sheet is adjusted by changing the thickness of the thermosetting polyurethane layer, and the thicknesses of the first acrylic pressure-sensitive adhesive layer and the second acrylic pressure-sensitive adhesive layer are 25 μm in all Examples and Comparative Examples. I chose

The polycarbonate substrate used in the examples and comparative examples is as follows.
Thickness 0.5mm: "Resin Sheet PCTSH" manufactured by MISUMI Group Headquarters
Thickness 1.0mm: "Resin Sheet PCTSH" manufactured by MISUMI Group Head Office
Thickness 1.5mm: "PC1151" manufactured by Teijin Limited
Thickness 2.0 mm: "PC1600" manufactured by Takiron CAI
Thickness 3.0mm: "PC1600" manufactured by Takiron CAI

As shown in Table 1 above, Examples 1 to 4 and 7 to 10 satisfy the following condition (1), and Examples 5, 6, 11 to 16 satisfy the following condition (2). Moreover, Examples 2-6, 10-14, and 16 satisfy the following condition (3).
(1) The thickness of the optically transparent adhesive sheet is 0.3 mm or more and 1.0 mm or less, and the thickness of the polycarbonate substrate is 1.0 mm or less (2) The thickness of the optically transparent adhesive sheet is more than 1.0 mm and 2.0 mm or less. And the thickness of the polycarbonate substrate is 2.0 mm or less. (3) The thickness of the optically transparent adhesive sheet is equal to or more than the thickness of the polycarbonate substrate.

(Evaluation test)
Two rectangular test bodies (diagonal length: 7 inches) were prepared for each of the bonded structures produced in the examples and comparative examples. The first test body was left in an oven at 95° C. for 24 hours, and the second test body was left in a high temperature and high humidity environment of 85° C. and 85% for 24 hours. Visual observation of the first and second test specimens after being left standing reveals that bubbles (delayed) at the adhesive interface between the glass substrate and the optically transparent adhesive sheet and at the adhesive interface between the polycarbonate substrate and the optically transparent adhesive sheet. It was confirmed whether or not bubbles were generated.

Table 2 below shows the test results of the first test body, and Table 3 below shows the test results of the second test body. In Tables 2 and 3, “◯” is described for the condition where the delayed foam was not generated, and “X” was described for the condition where the delayed foam was generated.

As can be seen from Table 2 above, in Examples 1 to 16 satisfying the following condition (1) or (2), delayed foaming did not occur even when left in a high temperature environment of 95°C for 24 hours.
(1) The thickness of the optically transparent adhesive sheet is 0.3 mm or more and 1.0 mm or less, and the thickness of the polycarbonate substrate is 1.0 mm or less (2) The thickness of the optically transparent adhesive sheet is more than 1.0 mm and 2.0 mm or less. And the thickness of the polycarbonate substrate is 2.0 mm or less

As can be seen from Table 3 above, in Examples 2 to 6, 10 to 14 and 16 satisfying the following condition (3), delayed bubbles were generated even when left in a high temperature and high humidity environment of 85° C. and 85% for 24 hours. There wasn't.
(3) The thickness of the optically transparent adhesive sheet is equal to or greater than the thickness of the polycarbonate substrate.

10: Optically transparent adhesive sheet 11: First acrylic adhesive layer 12: Thermosetting polyurethane layer 13: Second acrylic adhesive layer 31: Slide glass 32: PET sheet 41: Upper bezel (support member)
42: Lower bezel 50: Laminated structure 51: First base material 52: Second base material 52A: Light shielding part

Claims (4)

A first acrylic pressure-sensitive adhesive layer constituting the first surface, a thermosetting polyurethane layer, and an optical transparent pressure-sensitive adhesive sheet having a second acrylic pressure-sensitive adhesive layer constituting the second surface in this order,
A polycarbonate substrate adhered to the first surface,
The laminated structure, wherein the thickness of the optically transparent pressure-sensitive adhesive sheet and the thickness of the polycarbonate substrate satisfy the following relationship (1) or (2).
(1) The thickness of the optically transparent pressure-sensitive adhesive sheet is 0.3 mm or more and 1.0 mm or less, and the thickness of the polycarbonate substrate is 1.0 mm or less (2) The thickness of the optically transparent pressure-sensitive adhesive sheet exceeds 1.0 mm 2 0.0 mm or less, and the thickness of the polycarbonate substrate is 2.0 mm or less The laminated structure according to claim 1, wherein the optically transparent pressure-sensitive adhesive sheet has a thickness equal to or greater than the thickness of the polycarbonate substrate. The laminated structure according to claim 1 or 2, wherein the thermosetting polyurethane layer is thicker than the first acrylic adhesive layer and the second acrylic adhesive layer. The laminated structure according to claim 1, wherein the first acrylic pressure-sensitive adhesive layer has a thickness of 3 to 100 μm.

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