Adhesive, adhesive sheet, laminate, and display

Abstract

To provide an adhesive, an adhesive sheet, a laminate, and a display, which exhibit excellent transparency, and further satisfy heat resistance and humidity heat resistance, as well as flexibility and winding capability.SOLUTION: The problem of the present invention is solved by an adhesive comprising a specific acrylic copolymer (A), an isocyanate compound (B), and a metal chelate compound (C), the adhesive satisfying all of (1) to (3). (1) 3.0×104 Pa<G'(-20)<4.0×105 Pa; (2) 5<G'(-20) / G'(200)<17; (3) 2<tanδ(-20) / tanδ(200)<6. In these formulas, G'(-20) represents the storage elastic modulus at -20°C and 1 Hz, G'(200) represents the storage elastic modulus at 200°C and 1 Hz, tanδ (-20) represents the loss tangent at -20°C and 1 Hz, and tanδ (200) represents the loss tangent at 200°C and 1 Hz, respectively.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a pressure-sensitive adhesive suitable for forming a laminate including a light-transmitting substrate, a pressure-sensitive adhesive layer, and a polarizing plate, a pressure-sensitive adhesive sheet, and a laminate having the pressure-sensitive adhesive layer. The laminate is suitable for use in displays. [Background technology]

[0002] Thin image display devices such as liquid crystal displays and organic EL displays usually have a laminated structure including image forming layers such as a liquid crystal layer and an organic EL layer, and an optical film and a cover panel. Adhesives are generally used to bond each layer constituting an image display device. For example, a transparent conductive film used in a touch panel is laminated on a member such as a support glass or a support film via an adhesive layer. In addition, a polarizing plate film used in an image device is attached to a liquid crystal module or an organic EL module via an adhesive layer. In this way, each member of the image display device is attached and fixed by the adhesive layer.

[0003] Furthermore, while flat displays using glass substrates have been mainstream as the image display devices, flexible displays using flexible substrates such as plastics, such as foldable displays and rollable displays, have been developed in recent years. Such flexible displays have various advantages, such as being lighter, thinner, more flexible, and more attractive in design, compared to conventional flat displays using glass substrates.

[0004] The adhesive layer has traditionally been required to have a property of not foaming or peeling in a high temperature environment or a high temperature and high humidity environment, but in recent years, further functionality has been required, and flexibility has become necessary for flexible displays. For example, in the case of a foldable display, flexibility is the suitability (flexibility) of the display to bend. In general, the flexibility requires a property (dynamic flexibility) that does not cause foaming, lifting, or peeling when repeatedly folded.

[0005] Patent Document 1 discloses a pressure-sensitive adhesive containing an acrylic polymer and a radically polymerizable compound, while Patent Document 2 discloses a pressure-sensitive adhesive containing two types of acrylic polymers. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2023-89937 A [Patent Document 2] International Publication No. 2023 / 068009 Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, in order to keep up with the ever-increasing durability of displays, the adhesives used are required to have higher durability than ever before. In particular, for foldable displays, in addition to the property of not causing foaming, lifting or peeling when repeatedly bent (dynamic flexibility), the adhesive also needs to have the property of not causing foaming, lifting or peeling when the bent state is maintained for a long period of time (static flexibility). In addition, for rollable displays, the adhesive needs to be suitable for rolling up the display (winding ability) so that it can be used for rollable displays. In terms of winding ability, the adhesive needs to have the property of not causing foaming, lifting or peeling when the rolled state is maintained for a long period of time. Characteristics are required.

[0008] Furthermore, while conventionally, this flexibility was a required quality only at room temperature, with the spread of displays, flexibility in low-temperature environments such as those in extremely cold regions, and high-temperature environments such as those found in extremely hot regions or inside automobiles under the blazing sun, is now also becoming necessary.

[0009] In contrast, conventional pressure-sensitive adhesive sheets currently fail to satisfy the requirements for heat resistance, moist heat resistance, and flexibility, such as bendability and rollability, at a level that is practically problem-free. In addition, flexibility requires dynamic bending, static bending, and rollability depending on the display configuration. Although it is possible to satisfy these flexibility requirements individually, it is difficult to satisfy all of them at the same time. In addition, the current situation is that dynamic bending, static bending, and rollability cannot be satisfied in high temperature environments or high temperature and high humidity environments.

[0010] An object of the present invention is to provide a pressure-sensitive adhesive, a pressure-sensitive adhesive sheet, and a laminate thereof, which are excellent in transparency and further satisfy heat resistance, moist heat resistance, bending property and winding property, as well as a display. [Means for solving the problem]

[0011] As a result of extensive investigations, the present inventors have found that the problems of the present invention can be solved in the following aspect, and have thus completed the present invention. That is, an embodiment of the present invention includes an acrylic copolymer (A), an isocyanate compound (B), and a metal chelate compound (C), The acrylic copolymer (A) is a copolymer of a monomer mixture containing the following monomers (a-1), (a-2) and (a-3): The problems are solved by a pressure-sensitive adhesive that satisfies all of the following (1) to (3): (a-1) (Meth)acrylic acid alkyl ester monomer having an alkyl group with 8 to 12 carbon atoms (a-2) Monomer having a hydroxyl group (a-3) Monomers that form chelate bridges with metal compounds (1) 3.0×10 4Pa <G’(-20)<4.0×10 5 Pa (2)5 <G’(-20) / G’(200)<17 (3)2 <tanδ(-20) / tanδ(200)<6 Here, in the above formula, G'(-20) is the storage modulus at -20℃ and 1Hz G'(200) is the storage modulus at 200℃ and 1Hz tanδ(-20) is the loss tangent at -20℃ and 1Hz tanδ(200) is the loss tangent at 200℃ and 1Hz Each refers to:

[0012] Another embodiment of the present invention is the above-mentioned pressure-sensitive adhesive, characterized in that the acrylic copolymer (A) contains, in 100 mass% of the monomer mixture, 20 to 98 mass% of monomer (a-1), 0.2 to 2 mass% of monomer (a-2), and 0.2 to 5 mass% of monomer (a-3).

[0013] Another embodiment of the present invention is the above pressure-sensitive adhesive, which contains 0.5 to 5 mass% of the isocyanate compound (B) and 0.2 to 2 mass% of the metal chelate compound (C) relative to 100 mass% of the acrylic copolymer (A1).

[0014] In addition, an embodiment of the present invention is the above-mentioned, characterized in that the gel fraction is 60 to 90 mass %. The adhesive is as described above.

[0015] Another embodiment of the present invention is a pressure-sensitive adhesive sheet in which a pressure-sensitive adhesive layer, which is a cured product of the pressure-sensitive adhesive, is sandwiched between release films.

[0016] Moreover, an embodiment of the present invention is a laminate comprising a light-transmitting substrate, a pressure-sensitive adhesive layer, and a polarizing plate, the pressure-sensitive adhesive layer being a cured product of the pressure-sensitive adhesive.

[0017] Another embodiment of the present invention is a display comprising the above laminate and an optical element. Effect of the Invention

[0018] The present invention provides a pressure-sensitive adhesive, a pressure-sensitive adhesive sheet, and a laminate using the pressure-sensitive adhesive sheet, which are excellent in transparency and further capable of achieving heat resistance, moist heat resistance, flexibility, and roll-up properties. Furthermore, by using the pressure-sensitive adhesive sheet and laminate of the present invention, a display excellent in visibility and contrast can be provided. [Brief description of the drawings]

[0019] [Figure 1] 1 is a schematic cross-sectional view partially illustrating a pressure-sensitive adhesive sheet of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view partially illustrating a laminate, which is an example of use of the pressure-sensitive adhesive sheet of the present invention. [Diagram 3] FIG. 1 is a schematic cross-sectional view partially illustrating a display, which is an example of the use of the pressure-sensitive adhesive sheet of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, examples of the configurations of the pressure-sensitive adhesive, pressure-sensitive adhesive sheet, laminate, and display of the present invention will be described, but the present invention is not limited thereto.

[0021] The terms used in this specification are defined. (Meth)acrylic acid ester includes acrylic acid ester and methacrylic acid ester. Monomer is an ethylenically unsaturated group-containing monomer. Adherend refers to a counterpart to which the pressure-sensitive adhesive sheet is attached. In the present invention, sheet, film, and tape are synonymous terms. In this specification, (a-1) (meth)acrylic acid alkyl ester monomers having an alkyl group with 8 to 12 carbon atoms, (a-2) monomers having a hydroxyl group, (a-3) monomers forming chelate crosslinks with metal compounds, and (a-4) other monomers other than (a-1), (a-2), and (a-3) may be abbreviated as monomer (a-1), monomer (a-2), monomer (a-3), and monomer (a-4), respectively. In addition, acrylic copolymers (A), isocyanate compounds (B), metal compounds (C), and other crosslinking agents (D) other than (B) and (C) may be abbreviated as copolymers (A), compounds (B), compounds (C), and other crosslinking agents (D), respectively. Unless otherwise noted, the various components appearing in this specification may be used independently as a single type or as a combination of two or more types.

[0022] In this specification, any numerical range specified using "to" is intended to include the numerical values ​​before and after "to" as the lower and upper limit values ​​of the range.

[0023] <Adhesive> The pressure-sensitive adhesive of the present invention comprises a specific acrylic copolymer (A), an isocyanate compound (B) and a metal chelate compound (C), The pressure-sensitive adhesive is characterized by satisfying all of the following (1) to (3): (1) 3.0×10 4 Pa <G’(-20)<4.0×10 5 Pa (2)5 <G’(-20) / G’(200)<17 (3)2 <tanδ(-20) / tanδ(200)<6 Here, in the above formula, G'(-20) is the storage modulus at -20℃ and 1Hz G'(200) is the storage modulus at 200℃ and 1Hz tanδ(-20) is the loss tangent at -20℃ and 1Hz tanδ(200) is the loss tangent at 200℃ and 1Hz Each refers to:

[0024] <Acrylic copolymer (A)> The acrylic copolymer (A) is a copolymer of a monomer mixture containing at least (a-1), (a-2) and (a-3), and the monomer mixture may contain a monomer (a-4) as necessary. (a-1) (Meth)acrylic acid alkyl ester monomer having an alkyl group with 8 to 12 carbon atoms (a-2) Monomer having a hydroxyl group (a-3) Monomers that form chelate bridges with metal compounds (a-4) Other monomers other than (a-1), (a-2), and (a-3)

[0025] [Monomer (a-1)] Monomer (a-1) is an alkyl (meth)acrylate having an alkyl group with 8 to 12 carbon atoms. It is an ester monomer, and specific examples thereof include n-octyl (meth)acrylate, 2-octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, and dodecyl (meth)acrylate. Among these monomers (a-1), the use of n-octyl (meth)acrylate, isooctyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate is preferable because it is possible to particularly impart stress relaxation properties and adhesion, and as a result, flexibility is improved.

[0026] The acrylic copolymer (A) contains the monomer (a-1) and has a long-chain alkyl group in the side chain, which allows the polymers to be appropriately entangled with each other, imparting stress relaxation properties and adhesion to the substrate, and as a result, the flexibility is highly improved.

[0027] The monomer (a-1) is preferably contained in an amount of 20 to 98% by mass, more preferably 40 to 90% by mass, based on 100% by mass of the monomer mixture. When the content is 20% by mass or more, sufficient stress relaxation properties can be imparted and flexibility can be improved. When the content is 98% by mass or less, flexibility can be maintained.

[0028] [Monomer (a-2)] The monomer (a-2) is a monomer having a hydroxyl group, and specific examples thereof include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Among these monomers (a-2), 2-hydroxyethyl (meth)acrylate is preferably used since it can impart cohesive strength, thereby improving heat resistance and moist heat resistance.

[0029] The acrylic copolymer (A) contains the monomer (a-2) and thus has a hydroxyl group in the side chain, which allows it to form a crosslinked structure with the isocyanate compound (B) described later and impart cohesive strength, thereby improving heat resistance and moist heat resistance.

[0030] The monomer (a-2) is preferably contained in an amount of 0.2 to 2 mass% and more preferably 0.4 to 1.5 mass% in 100 mass% of the monomer mixture. When the content is 0.2 mass% or more, sufficient cohesiveness can be imparted, and heat resistance and moist heat resistance can be improved. When the content is 2 mass% or less, heat resistance and moist heat resistance can be maintained.

[0031] [Monomer (a-3)] Monomer (a-3) is a monomer that forms a chelate crosslink with a metal compound, and examples thereof include carboxyl group-containing monomers and monomers containing α-hydrogen in the molecule. Here, α-hydrogen means hydrogen bonded to the carbon adjacent to the carbonyl group. Specifically, carboxyl group-containing monomers such as (meth)acrylic acid, p-carboxybenzyl acrylate, β-carboxyethyl acrylate, maleic acid, monoethyl maleic acid, itaconic acid, citraconic acid, and fumaric acid; Examples of monomers containing an α-hydrogen atom in the molecule include acetylmethyl (meth)acrylate, propionylmethyl (meth)acrylate, 2-oxopropyl (meth)acrylate, oxobutyl (meth)acrylate, 2-butyrylethyl (meth)acrylate, 4-oxohexyl (meth)acrylate, and acetoacetoxyethyl (meth)acrylate. Among these monomers (a-3), (meth)acrylic acid and acetoacetoxyethyl (meth)acrylate are particularly capable of imparting cohesive strength, which results in improved winding properties, and are therefore preferred.

[0032] The acrylic copolymer (A) contains the monomer (a-3), and thus has a substituent on the side chain that forms a crosslink with a metal compound, which can form a crosslinked structure with the metal compound (C) described below and impart cohesive strength, thereby improving winding properties.

[0033] The monomer (a-3) is preferably contained in an amount of 0.2 to 5 mass %, more preferably 0.5 to 3 mass %, based on 100 mass % of the monomer mixture. When the content is 0.2 mass % or more, sufficient cohesiveness can be imparted and winding properties can be improved. When the content is 5 mass % or less, winding properties can be maintained.

[0034] [Monomer (a-4)] Monomer (a-4) is a monomer other than monomers (a-1), (a-2), and (a-3). Examples of monomer (a-4) include (meth)acrylic acid alkyl ester monomers other than monomer (a-1), monomers having an epoxy group, monomers having an amino group, monomers having an alkyleneoxy group, and vinyl monomers.

[0035] Examples of (meth)acrylic acid alkyl ester monomers other than monomer (a-1) include (meth)acrylic acid alkyl ester monomers having an alkyl group with 1 to 7 carbon atoms, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, and heptyl (meth)acrylate, and (meth)acrylic acid alkyl ester monomers having an alkyl group with 13 or more carbon atoms, such as octadecyl (meth)acrylate.

[0036] Examples of the monomer having an epoxy group include glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, and 3,4-epoxycyclohexylmethyl (meth)acrylate. , and 6-methyl-3,4-epoxycyclohexylmethyl (meth)acrylate.

[0037] Examples of monomers having an amino group include monoalkylamino (meth)acrylates such as monomethylaminoethyl (meth)acrylate, monoethylaminoethyl (meth)acrylate, monomethylaminopropyl (meth)acrylate, and monoethylaminopropyl (meth)acrylate.

[0038] Examples of the monomer having an alkyleneoxy group include a monomer represented by the following general formula (1) or a monomer represented by the following general formula (2).

[0039] [ka]

[0040] [ka]

[0041] In the general formula (1) and the general formula (2), R 1 , R 2 each independently represents a hydrogen atom or a methyl group; n and m each represent an integer representing a repeating unit, and 1≦n≦25, 1≦m≦25, and preferably 1≦n≦13, 1≦m≦5.

[0042] A commercially available product of the monomer represented by the general formula (1) is, for example, methoxyethyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd.; R 1 is a hydrogen atom, n=1), methoxydiethylene glycol acrylate (Osaka Organic Chemical Industry Co., Ltd.: in the above formula (1), R 1 is a hydrogen atom, n=2), methoxytriethylene glycol acrylate (Osaka Organic Chemical Industry Co., Ltd.: in the above formula (1), R 1 is a hydrogen atom, n=3), methoxypolyethylene glycol #400 acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.: in the above formula (1), R 1 is a hydrogen atom, n=9), methoxypolyethylene glycol #600 acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.: in the above formula (1), R 1 is a hydrogen atom, n=13), methoxypolyethylene glycol #1000 acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.: in the above formula (1), R 1 is a hydrogen atom, n=23), methoxydiethylene glycol methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.: in the above formula (1), R 1 is a methyl group, n=2), methoxytriethylene glycol methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.: in the above formula (1), R 1 is a methyl group, n=3), methoxytetraethylene glycol methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.: in the above formula (1), R 1 is a methyl group, n=4), methoxypolyethylene glycol #400 methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.: in the above formula (1), R1 is a hydrogen atom, n=9) , methoxypolyethylene glycol #600 methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.; in the above formula (1), R 1 is a hydrogen atom, n=13), methoxypolyethylene glycol #1000 methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.: in the above formula (1), R 1 is a hydrogen atom, n=23).

[0043] A commercially available product of the monomer represented by the general formula (2) is, for example, methoxytripropylene glycol acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.; in the above formula (2), R 1 is a hydrogen atom, m=3), methoxytripropylene glycol methacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.: in the above formula (2), R 1 is a methyl group, m=3)

[0044] Examples of the vinyl monomer include vinyl acetate, vinyl crotonate, styrene, and acrylonitrile.

[0045] When the monomer mixture contains the monomer (a-4), the monomer mixture preferably contains 100% by mass, or 5 to 40% by mass. When the content is 5% by mass or more, the cohesive strength is further improved. When the content is 40% by mass or less, the adhesion is further improved.

[0046] [Production of acrylic copolymer (A)] The copolymer (A) can be produced by polymerizing a monomer mixture. The polymerization can be carried out by a known polymerization method such as solution polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, etc., but solution polymerization is preferred. The solvent used in the solution polymerization is preferably, for example, acetone, methyl acetate, ethyl acetate, toluene, xylene, anisole, methyl ethyl ketone, cyclohexanone, etc. The polymerization temperature is preferably a boiling point reaction at 60 to 120° C. The polymerization time is preferably about 5 to 12 hours.

[0047] The polymerization initiator used in the polymerization is preferably a radical polymerization initiator, and the radical polymerization initiator is generally a peroxide or an azo compound. Examples of peroxides include dialkyl peroxides such as di-t-butyl peroxide, dicumyl peroxide, t-butylcumyl peroxide, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, and 2,5-di(t-butylperoxy)hexyne-3; Peroxyesters such as t-butyl peroxybenzoate, t-butyl peroxyacetate, and 2,5-dimethyl-2,5-di(benzoylperoxy)hexane; ketone peroxides such as cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, and methylcyclohexanone peroxide; Peroxyketals such as 2,2-bis(4,4-di-t-butylperoxycyclohexyl)propane, 1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, and n-butyl-4,4-bis(t-butylperoxy)valerate; Hydroperoxides such as cumene hydroperoxide, diisopropylbenzene hydroperoxide, and 2,5-dimethylcyclohexane-2,5-dihydroperoxide; diacyl peroxides such as benzoyl peroxide, decanoyl peroxide, lauroyl peroxide, and 2,4-dichlorobenzoyl peroxide; Examples include peroxydicarbonates such as bis(t-butylcyclohexyl) peroxydicarbonate.

[0048] Azo compounds include, for example, 2,2'-azobisbutyronitride such as 2,2'-azobisisobutyronitrile (ABN) and 2,2'-azobis(2-methylbutyronitrile). Le; 2,2'-azobisvaleronitriles such as 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) and 2,2'-azobis(2,4-dimethylvaleronitrile); 2,2'-azobispropionitriles such as 2,2'-azobis(2-hydroxymethylpropionitrile); Examples include 1,1'-azobis-1-alkanenitriles such as 1,1'-azobis(cyclohexane-1-carbonitrile).

[0049] The polymerization initiator is preferably used in an amount of 0.01 to 10 parts by mass, more preferably 0.1 to 2 parts by mass, based on 100 parts by mass of the monomer mixture.

[0050] [Weight average molecular weight (Mw)] The weight average molecular weight of the acrylic copolymer (A) is preferably 600,000 to 1,800,000, more preferably 800,000 to 1,200,000. If it is in the range of 600,000 to 1,800,000, the cohesive force is further improved, and the moist heat resistance and heat resistance are further improved. The specific method for measuring the weight average molecular weight is described in the Examples section.

[0051] <Isocyanate compound (B)> The isocyanate compound (B) reacts with the hydroxyl group of the copolymer (A) to impart cohesive strength to the pressure-sensitive adhesive layer, thereby highly improving the flexibility.

[0052] The isocyanate compound (B) is an isocyanate having two or more isocyanate groups. The isocyanate compound is preferably, for example, an isocyanate monomer such as an aromatic polyisocyanate, an aliphatic polyisocyanate, an araliphatic polyisocyanate, or an alicyclic polyisocyanate, as well as a biuret, a nurate, or an adduct thereof.

[0053] Examples of aromatic polyisocyanates include 1,3-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-toluidine diisocyanate, 2,4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, and 4,4',4"-triphenylmethane triisocyanate.

[0054] Examples of aliphatic polyisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (also known as HMDI), pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

[0055] Examples of the aromatic aliphatic polyisocyanate include ω,ω'-diisocyanate-1,3-dimethylbenzene, ω,ω'-diisocyanate-1,4-dimethylbenzene, ω,ω'-diisocyanate-1,4-diethylbenzene, 1,4-tetramethylxylylene diisocyanate, and 1,3-tetramethylxylylene diisocyanate.

[0056] Alicyclic polyisocyanates include, for example, 3-isocyanatemethyl-3,5,5-trimethylcyclohexyl isocyanate (also known as IPDI, isophorone diisocyanate), 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, and methyl-2,4-cyclohexane diisocyanate. anate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), 1,4-bis(isocyanatemethyl)cyclohexane, and the like.

[0057] The biuret form is a self-condensation product having a biuret bond formed by self-condensation of an isocyanate monomer, for example, a biuret form of hexamethylene diisocyanate.

[0058] The nurate form is a trimer of an isocyanate monomer, such as a trimer of hexamethylene diisocyanate, a trimer of isophorone diisocyanate, or a trimer of tolylene diisocyanate.

[0059] The adduct is a bifunctional or higher isocyanate compound obtained by reacting an isocyanate monomer with a bifunctional or higher low-molecular active hydrogen-containing compound. Examples of the adduct include a compound obtained by reacting trimethylolpropane with hexamethylene diisocyanate, a compound obtained by reacting trimethylolpropane with tolylene diisocyanate, a compound obtained by reacting trimethylolpropane with xylylene diisocyanate, a compound obtained by reacting trimethylolpropane with isophorone diisocyanate, and a compound obtained by reacting 1,6-hexanediol with hexamethylene diisocyanate.

[0060] From the viewpoint of forming a sufficient crosslinked structure, the isocyanate compound (B) is preferably a trifunctional isocyanate compound. The isocyanate compound is more preferably an adduct or nurate, which is a reaction product between an isocyanate monomer and a trifunctional low molecular weight active hydrogen-containing compound. Specifically, the isocyanate compound is preferably a trimethylolpropane adduct of hexamethylene diisocyanate, a nurate of hexamethylene diisocyanate, a trimethylolpropane adduct of tolylene diisocyanate, a nurate of tolylene diisocyanate, a trimethylolpropane adduct of isophorone diisocyanate, or a nurate of isophorone diisocyanate, and more preferably a trimethylolpropane adduct of hexamethylene diisocyanate, a trimethylolpropane adduct of tolylene diisocyanate, or a trimethylolpropane adduct of isophorone diisocyanate. Among these, a trimethylolpropane adduct of tolylene diisocyanate and a nurate of tolylene diisocyanate are preferred from the viewpoint of flexibility.

[0061] The isocyanate compound (B) is preferably contained in an amount of 0.5 to 5 mass % relative to 100 mass % of the copolymer (A), and more preferably contained in an amount of 0.5 to 3 mass %. When the content is 0.5 mass % or more, cohesive strength can be imparted and flexibility can be highly improved. When the content is 5 mass % or less, flexibility can be maintained. Furthermore, the ratio (NCO / OH) of the number of moles of isocyanate groups contained in the isocyanate compound (B) to the number of moles of hydroxyl groups contained in the acrylic copolymer (A) is preferably 0.5 to 3, and more preferably 0.5 to 2. When the ratio is 0.5 or more, sufficient cohesive strength can be obtained, and when it is 3 or less, it is preferable because it is easy to achieve both cohesive strength and flexibility. In general, in adhesives used in image display devices, an isocyanate compound is used to impart cohesiveness, but in order to suppress a decrease in adhesion due to crosslinking, it is common to use only a small amount of isocyanate compound (approximately 0.4 or less in terms of mole ratio). For this reason, it may be difficult to achieve both flexibility and winding properties at a high level. On the other hand, in the adhesive of the present invention, even if a large amount of isocyanate compound is used, it is possible to suppress a decrease in adhesion, so that it is possible to achieve both flexibility and winding properties at a high level due to crosslinking.

[0062] <Metal chelate compounds (C)> The metal chelate compound (C) reacts with a substituent that forms a crosslink with the metal compound contained in the copolymer (A) to improve the cohesive strength of the pressure-sensitive adhesive layer and impart cohesive strength, thereby highly improving the winding property.

[0063] Examples of the metal chelate compound (C) include coordination compounds of polyvalent metals such as aluminum, iron, copper, zinc, titanium, nickel, magnesium, and zirconium with acetylacetone or ethyl acetoacetate. Examples of the metal compounds include aluminum ethyl acetoacetate diisopropylate, aluminum trisacetylacetonate, aluminum bisethyl acetoacetate monoacetylacetonate, aluminum alkyl acetoacetate diisopropylate, iron trisacetylacetonate, copper bisacetylacetonate, zinc bisacetylacetonate, titanium tetraacetylacetonate, nickel bisacetylacetonate, magnesium bisacetylacetonate, and zirconium tetraacetylacetonate. Among these metal chelate compounds (C), aluminum compounds and zinc compounds are preferred from the viewpoint of cohesive strength and coloring, and aluminum ethylacetoacetate diisopropylate, aluminum trisacetylacetonate, and zinc bisacetylacetonate are more preferred.

[0064] The metal chelate compound (C) is preferably contained in an amount of 0.2 to 2 mass% relative to 100 mass% of the copolymer (A), and more preferably contained in an amount of 0.2 to 1.5 mass%. When the content is 0.2 mass% or more, cohesive strength can be imparted, and winding properties can be highly improved. When the content is 2 mass% or less, winding properties can be maintained.

[0065] The pressure-sensitive adhesive of the present invention may further contain a crosslinking agent (D) other than the compounds (B) and (C). By containing the crosslinking agent (D), durability can be improved. Examples of the crosslinking agent (D) include an epoxy compound, an aziridine compound, and a carbodiimide compound.

[0066] Examples of epoxy compounds include glycerin diglycidyl ether, 1,6-hexanediol diglycidyl ether, N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N'-diglycidylaminomethyl)cyclohexane, and N,N,N',N'-tetraglycidylaminophenylmethane.

[0067] Aziridine compounds include, for example, N,N'-diphenylmethane-4,4'-bis(1-aziridinium). lysine carboxylate), tris-2,4,6-(1-aziridinyl)-1,3,5-triazine, 4,4'-bis(ethyleneiminocarbonylamino)diphenylmethane, 2,2-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate], and the like.

[0068] The carbodiimide compound is preferably a high molecular weight polycarbodiimide produced by decarboxylation condensation of a diisocyanate compound in the presence of a carbodiimide catalyst. The commercially available high molecular weight polycarbodiimide is preferably the Carbodilite series from Nisshinbo Industries, Ltd. Among them, Carbodilite V-03, 07, and 09 are preferred because of their excellent compatibility with organic solvents.

[0069] The content of the other crosslinking agent (D) is preferably 0.05 to 2 mass %, more preferably 0.1 to 1 mass %, relative to 100 mass % of the copolymer (A). When the content is 0.05 mass % or more, the cohesive strength is further improved, and when it is 2 mass % or less, the adhesion is further improved.

[0070] <Organosilane compounds> The pressure-sensitive adhesive of the present invention may further contain an organosilane compound. By containing an organosilane, the adhesiveness to an adherend can be improved. Examples of the organic silane compound include alkoxysilane compounds having a (meth)acryloxy group, such as 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropyltripropoxysilane, 3-(meth)acryloxypropyltributoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane; Alkoxysilane compounds having a vinyl group, such as vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane, vinyltributoxysilane, vinylmethyldimethoxysilane, and vinylmethyldiethoxysilane; alkoxysilane compounds having an amino group, such as 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltripropoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane; alkoxysilane compounds having a mercapto group, such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropyltripropoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 3-mercaptopropylmethyldiethoxysilane; alkoxysilane compounds having an epoxy group, such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyltripropoxysilane, 3-glycidoxypropyltributoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane; tetraalkoxysilane compounds such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, and tetrabutoxysilane; Examples of the silane include 3-chloropropyltrimethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, n-decyltrimethoxysilane, n-decyltriethoxysilane, styryltrimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine, 1,3,5-tris(3-trimethoxysilylpropyl)isocyanurate, 3-isocyanatepropyltrimethoxysilane, 3-isocyanatepropyltriethoxysilane, hexamethyldisilazane, and silicone resins having alkoxysilyl groups in the molecule.

[0071] The organosilane compound is preferably used in an amount of 0.01 to 2.0% by mass, more preferably 0.05 to 1.0% by mass, based on 100% by mass of the copolymer (A).

[0072] The pressure-sensitive adhesive of the present invention may contain various resins, oils, softeners, dyes, pigments, antioxidants, UV absorbers, weather stabilizers, plasticizers, fillers, antioxidants, antistatic agents, and the like as optional components, so long as the problem can be solved.

[0073] <Adhesive properties> The pressure-sensitive adhesive of the present invention satisfies all of the following (1) to (3). (1) 3.0×10 4 Pa <G’(-20)<4.0×10 5 Pa (2)5 <G’(-20) / G’(200)<17 (3)2 <tanδ(-20) / tanδ(200)<6 Here, in the above formula, G'(-20) is the storage modulus at -20℃ and 1Hz G'(200) is the storage modulus at 200℃ and 1Hz tanδ(-20) is the loss tangent at -20℃ and 1Hz tanδ(200) is the loss tangent at 200℃ and 1Hz Each refers to:

[0074] <Storage modulus and loss factor> The storage modulus and loss factor of the adhesive are determined by viscoelasticity measurement at a frequency of 1 Hz. The storage modulus corresponds to the energy stored as elastic energy when the material is deformed, and is an index of the degree of hardness. In other words, the higher the storage modulus value, the harder the adhesive is, and the lower the storage modulus value, the softer it is. The loss factor is the value obtained by dividing the loss modulus, which corresponds to the energy diffused to the outside as loss energy when the material is deformed, by the storage modulus, and the higher the loss factor, the higher the stress relaxation property. Details of the measurement method are described in the Examples section.

[0075] The pressure-sensitive adhesive of the present invention has a storage elastic modulus at -20°C and 1 Hz (hereinafter, may be abbreviated as G'(-20)) of 3.0×10 4 Pa < G'(-20) < 4.0×10 5 Pa, and it is preferable that 3.0×10 4 Pa < G'(-20) < 3.0×10 5 Pa. When G'(-20) is greater than 3.0×10 4 Pa, the rigidity at low temperature is improved, and the flexibility and winding property are improved. When G'(-20) is less than 4×10 5 Pa, the adhesiveness is improved, and the flexibility and winding property are improved.

[0076] Also, the pressure-sensitive adhesive of the present invention is a value obtained by dividing the storage elastic modulus at -20°C and 1 Hz (hereinafter, may be abbreviated as G'(-20)) by the storage elastic modulus at 200°C and 1 Hz (hereinafter, may be abbreviated as G'(200)), and G'(-20) / G'(200) is 5 < G'(-20) / G'(200) < 17, and it is preferable that G'(-20) / G'(200) is 5 < G'(-20) / G'(200) < 15. When G'(-20) / G'(200) is greater than 5, the rigidity at low temperature is improved, and when G'(-20) / G'(200) is less than 17, the cohesiveness at high temperature is improved, so durability can be imparted.

[0077] Furthermore, the pressure-sensitive adhesive of the present invention is a value obtained by dividing the loss coefficient at -20°C and 1 Hz (hereinafter, may be abbreviated as tanδ(-20)) by the loss coefficient at 200°C and 1 Hz (hereinafter, may be abbreviated as tanδ(200)), and tanδ(-20) / tanδ(200) is 2 < tanδ(-20) / tanδ(200) < 6, and it is preferable that 2 < tanδ(-20) / tanδ(200) < 5. When tanδ(-20) / tanδ(200) is greater than 2, the stress relaxation property at low temperature is improved, and when tanδ(-20) / tanδ(200) is less than 6, the flexibility at high temperature is improved, so adhesiveness can be imparted.

[0078] The pressure-sensitive adhesive of the present invention has a storage modulus and loss factor within specific ranges, and thereby exhibits the flexibility required for a foldable display and the winding ability required for a rollable display.

[0079] <Gel fraction> The pressure-sensitive adhesive of the present invention preferably has a gel fraction of 60 to 90% by mass, more preferably 60 to 80% by mass. When the gel fraction is 60% by mass or more, the cohesive strength of the pressure-sensitive adhesive is improved, a tough pressure-sensitive adhesive layer is obtained, and durability is improved. When the gel fraction is 90% by mass or less, the stress relaxation property of the pressure-sensitive adhesive is improved. This improves adhesion, resulting in a flexible adhesive layer.

[0080] [Gel fraction measurement method] The gel fraction can be determined as the amount of insoluble matter in a solvent such as ethyl acetate. Specifically, as represented by the following formula 1, the gel fraction is determined as the mass fraction (unit: mass%) of the insoluble matter after the pressure-sensitive adhesive layer is immersed in ethyl acetate at 50° C. for one day relative to the pressure-sensitive adhesive layer before immersion. (Formula 1) Gel fraction (mass%) = (Y / X) x 100 X = mass of adhesive layer before immersion (g) Y = mass of adhesive layer after immersion (g) In general, the gel fraction of a polymer is equal to the degree of crosslinking, and the more crosslinked parts in the polymer, the higher the gel fraction. The gel fraction (amount of crosslinked structure) depends on the method of introducing the crosslinked structure and The amount of the curing agent can be adjusted to a desired range by changing the type and amount of the curing agent.

[0081] "Adhesive sheet" The pressure-sensitive adhesive sheet of the present invention is an adhesive sheet that is preferably used for forming an adhesive layer in a laminate consisting of a light-transmitting substrate and an adhesive layer, i.e., the pressure-sensitive adhesive sheet of the present invention is preferably used for bonding light-transmitting substrates. An example of a schematic cross-sectional view partially illustrating the pressure-sensitive adhesive sheet of the present invention is shown in Fig. 1. In Fig. 1, 1 is a pressure-sensitive adhesive layer 1 and 2 is a release film.

[0082] As shown in FIG. 1, the adhesive sheet of the present invention has a configuration in which release films are formed on both sides of an adhesive layer, and the adhesive layer sandwiched between the release films is an adhesive layer formed from the adhesive of the present invention, which contains an acrylic copolymer (A), an isocyanate compound (B), and a metal compound (C).

[0083] <Release film> The release film is not particularly limited, but a transparent plastic substrate can be suitably used. Examples of the material of the transparent plastic substrate include polyesters such as polyethylene terephthalate (PET), acrylic resins such as polymethyl methacrylate (PMMA), polycarbonate, triacetyl cellulose, polysulfone, polyarylate, polycycloolefin, and other plastic materials. The plastic materials can be used alone or in combination of two or more kinds.

[0084] As the release film, among the above-mentioned transparent plastic substrates, a transparent plastic substrate having excellent heat resistance, i.e., a transparent plastic substrate in which deformation is suppressed or prevented under severe conditions such as high temperature, high temperature and high humidity, can be preferably used. As the transparent plastic substrate, a PET film or sheet is particularly preferable.

[0085] The thickness of the transparent plastic substrate is not particularly limited, and is, for example, preferably from 10 to 200 μm, and more preferably from 25 to 150 μm.

[0086] The release film may have either a single layer or multiple layers. The surface of the transparent substrate may be subjected to an appropriate surface treatment, for example, a physical treatment such as a corona discharge treatment or a plasma treatment, or a chemical treatment such as an undercoat treatment.

[0087] <Manufacturing of adhesive sheets> The pressure-sensitive adhesive sheet of the present invention can be produced by a method for producing a conventional pressure-sensitive adhesive sheet. For example, a pressure-sensitive adhesive is applied to the release-treated surface of a release film so that the thickness after application is a predetermined thickness. or a method in which an adhesive is applied to the release-treated surfaces of two release films so that the adhesive has a specified thickness after application and then dried to form two adhesive layers, and then each adhesive layer is applied.

[0088] The drying conditions can be set depending on the composition and thickness of the raw material composition, the types and amounts of the organic peroxide and curing agent, and the like, and can be, for example, 3 minutes in an atmosphere at 90 to 110°C.

[0089] The thickness of the adhesive layer is not particularly limited and is, for example, preferably 10 to 500 μm, more preferably 50 to 200 μm. When the adhesive layer has a thickness of 10 to 500 μm, sufficient cohesive strength is easily obtained, and heat resistance, moist heat resistance, flexibility, and windability can be highly achieved at the same time, which is preferable.

[0090] When applying the adhesive, a conventional coater such as a gravure roll coater, reverse roll coater, kiss roll coater, dip roll coater, bar coater, knife coater, or spray coater can be used.

[0091] The pressure-sensitive adhesive sheet may be in the form of a rolled pressure-sensitive adhesive tape by cutting the sheet to a suitable width and winding the sheet into a roll.

[0092] "Laminate" The laminate of the present invention comprises a light-transmitting substrate, a pressure-sensitive adhesive layer, and a polarizing plate, and the pressure-sensitive adhesive layer is formed from a cured product of the pressure-sensitive adhesive of the present invention.

[0093] The laminate of the present invention is formed from a pressure-sensitive adhesive sheet having excellent transparency, heat resistance, moist heat resistance, flexibility and windability, and is therefore excellent in transparency, heat resistance, moist heat resistance, flexibility and windability.

[0094] An example of a schematic cross-sectional view partially illustrating a laminate, which is an example of the use of the pressure-sensitive adhesive sheet of the present invention, is shown in Fig. 2. In Fig. 2, 3 is a light-transmitting substrate (cover panel), 1 is a pressure-sensitive adhesive layer, and 1 and 4 are polarizing plates.

[0095] In the laminate shown in Fig. 2, a light-transmitting substrate (cover panel) is attached to a polarizing plate via an adhesive layer made of the adhesive of the present invention. In this manner, the adhesive sheet of the present invention can be used in a form in which a transparent adhesive layer formed from the adhesive is attached to the light-transmitting substrate (cover panel) and the polarizing plate.

[0096] The light-transmitting substrate (cover panel) is not particularly limited, but a transparent plastic substrate can be suitably used. Examples of the material of the transparent plastic substrate include acrylic resins such as polyethylene terephthalate (PET) and polymethyl methacrylate (PMMA), and plastic materials such as polycarbonate, polycycloolefin, and polyimide. The plastic materials can be used alone or in combination of two or more kinds.

[0097] As the light-transmitting substrate (cover panel), among the above-mentioned transparent plastic substrates, a transparent plastic substrate having excellent heat resistance, i.e., a transparent plastic substrate in which deformation is suppressed or prevented under severe conditions such as high temperature, high temperature and high humidity, etc. As the transparent plastic substrate, polyethylene terephthalate (PET), polycycloolefin, and polyimide are particularly suitable.

[0098] The thickness of the light-transmitting substrate (cover panel) is not particularly limited, and is, for example, preferably from 100 to 2000 μm, and more preferably from 200 to 1000 μm.

[0099] "display" The display comprises the laminate of the present invention and an optical element. The optical element is not particularly limited, and examples thereof include a liquid crystal element and an organic EL element.

[0100] The display of the present invention has a laminate excellent in transparency, heat resistance, moist heat resistance, flexibility and winding ability, and is therefore excellent in transparency, heat resistance, moist heat resistance, flexibility and winding ability.

[0101] Fig. 3 shows an example of a schematic cross-sectional view partially illustrating a display, which is an example of the use of the pressure-sensitive adhesive sheet of the present invention. In Fig. 3, 3 is a light-transmitting substrate (cover panel), 1 is a pressure-sensitive adhesive layer 1, 4 is a polarizing plate, 5 is a pressure-sensitive adhesive layer 2, 6 is a barrier layer such as silicon nitride, 7 is an organic EL layer, 8 is a support such as polyimide, and 9 is an organic EL cell. Note that the configuration of the display is not limited to that shown in Fig. 3.

[0102] In the display shown in Fig. 3, a light-transmitting substrate (cover panel) is attached to a polarizing plate via an adhesive layer (adhesive layer 1) made of the adhesive of the present invention, and is further attached to an organic EL cell via an adhesive layer for polarizing plate (adhesive layer 2). In this way, the adhesive sheet of the present invention can be used in a form in which a transparent adhesive layer formed from the adhesive is attached to a light-transmitting substrate (cover panel) and a polarizing plate, and the laminate is further attached to an organic EL cell via an adhesive layer for polarizing plate. For example, in FIG. 3, the pressure-sensitive adhesive of the present invention can be used in both pressure-sensitive adhesive layer 1 and pressure-sensitive adhesive layer 2. In general, when comparing pressure-sensitive adhesive layer 1 and pressure-sensitive adhesive layer 2, the pressure-sensitive adhesive layer 1 has higher quality requirements, and since the pressure-sensitive adhesive of the present invention has good adhesion and bonding properties to the substrate, it is preferably used for pressure-sensitive adhesive layer 1. In this case, the pressure-sensitive adhesive for forming pressure-sensitive adhesive layer 2 may be the pressure-sensitive adhesive of the present invention or a conventionally known pressure-sensitive adhesive.

[0103] There are no particular limitations on the uses of the displays, but examples include OLED televisions, OLED smartphones, OLED tablets, and OLED smartwatches. EXAMPLES

[0104] Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. In the examples, unless otherwise specified, "parts" means "parts by mass", "%" means "% by mass", and "RH" means relative humidity. The blending amounts in the tables are in parts by mass. Note that blanks in the tables indicate that no blending was performed. The method for measuring the weight average molecular weight of the acrylic copolymer (A) and the methods for measuring the storage modulus and loss factor of the pressure-sensitive adhesive are as follows.

[0105] <Measurement of weight average molecular weight> The weight average molecular weight (Mw) of the acrylic copolymer body (A) is measured using a GPC "LC-GPC system" manufactured by Shimadzu Corporation, and the weight average molecular weight (Mw) can be determined by conversion using polystyrene with a known molecular weight as a standard substance. Device name: Shimadzu Corporation, LC-GPC system "Prominence" Column: Four GMHXL columns manufactured by Tosoh Corporation and one HXL-H column manufactured by Tosoh Corporation were connected together. Mobile phase solvent: Tetrahydrofuran Flow rate: 1.0ml / min Column temperature: 40℃

[0106] <Measurement of storage modulus and loss factor> The storage modulus is measured by using a laminate of cured adhesive to a thickness of approximately 1.0 mm as the measurement sample and performing viscoelasticity measurements under the following conditions using a TA Instrument-Waters LLC "Discovery HR-2 (DHR-2)." From the measurement results, the storage modulus and loss factor at 0°C and 150°C can be read. (Measurement conditions) Deformation mode: Torsion Measurement frequency: 1Hz Heating rate: 10℃ / min Jig shape: Parallel plate 8.0mmφ

[0107] <Production Example of Acrylic Copolymer (A)> (Copolymer (A-1)) A reaction vessel (hereinafter simply referred to as the "reaction vessel") equipped with a stirrer, a thermometer, a reflux condenser, a dropping device, and a nitrogen inlet tube was charged with 18 parts of 2-ethylhexyl acrylate (EHA) as monomer (a-1), 1 part of 2-hydroxyethyl acrylate (HEA) as monomer (a-2), 1 part of acrylic acid as monomer (a-3), 80 parts of butyl acrylate as monomer (a-4), 2,2'-azobisisobutyronitrile (hereinafter simply referred to as the "reaction vessel") as an initiator. 0.2 parts of AIBN was charged and the atmosphere in the reaction vessel was replaced with nitrogen gas. The mixture was then heated to 60°C while stirring under a nitrogen atmosphere to initiate the reaction. The reaction solution was then reacted at 60°C for 4 hours. After completion of the reaction, the mixture was cooled and diluted with ethyl acetate to obtain a copolymer (A-1) solution with a non-volatile content of 30%. The weight average molecular weight of the obtained copolymer (A-1) was 1.2 million.

[0108] (Copolymer (A-2~A-12, A'-1~A'-3)) Copolymers (A-2 to A-10, A'-1 to A'-3) were produced in the same manner as in the production of the acrylic copolymer (A-1), except that the compositions and blending amounts (parts by mass) were changed to those shown in Table 1.

[0109] The weight average molecular weights (Mw) of the resulting copolymers (A-1 to 12, A'-1 to 3) are shown in Table 1.

[0110] [Table 1]

[0111] The abbreviations in the table are as follows. (Monomer (a-1)) EHA: 2-ethylhexyl acrylate (alkyl group carbon number: 8) nOA: n-octyl acrylate (alkyl group carbon number: 8) DOA: Dodecyl acrylate (alkyl group carbon number: 12) (Monomer (a-2)) HEA: 2-hydroxyethyl acrylate HEMA: 2-hydroxyethyl methacrylate (Monomer (a-3)) AA: Acrylic acid AAEM: Acetoacetoxyethyl methacrylate (Monomer (a-4)) BA: Butyl acrylate (alkyl group carbon number: 4) MA: Methyl acrylate (alkyl group carbon number 1)

[0112] Example 1 <Preparation of Adhesive> 100 parts of the nonvolatile content of the acrylic copolymer (A-1) were mixed with 1.2 parts of tolylene diisocyanate trimethylolpropane adduct (TDITMP) as the isocyanate compound (B) and 1 part of aluminum ethyl acetoacetate diisopropylate (ALEADI) as the metal compound (C), and stirred to obtain an adhesive.

[0113] <Manufacturing of adhesive sheets> The obtained adhesive was applied onto a 50 μm-thick release film (polyethylene terephthalate (PET), "E7004", silicone-based release layer, manufactured by Toyobo Co., Ltd.) so that the thickness after drying would be 50 μm, and the coating was dried at 100° C. for 3 minutes to form an adhesive layer. Next, one side of a 38 μm-thick release film (polyethylene terephthalate, "SP-PET3811", silicone-based release layer, manufactured by Lintec Corporation) was bonded to this adhesive layer to produce a "release sheet / adhesive layer / release sheet" laminate. Next, the obtained laminate was aged in a 40° C. environment for 3 days to obtain an adhesive sheet.

[0114] (Examples 2 to 18, Comparative Examples 1 to 12) As shown in Tables 2 and 3, pressure-sensitive adhesive sheets were obtained in the same manner as in Example 1, except that the types and amounts (parts by mass) of the copolymer and curing agent were changed.

[0115] [Table 2]

[0116] [Table 3]

[0117] The abbreviations in the table are as follows. <Isocyanate compound (B)> TDITMP: Trimethylolpropane adduct of tolylene diisocyanate TDIIN: Tolylene diisocyanate nurate HDITMP: Hexamethylene diisocyanate trimethylolpropane adduct <Metal chelate compounds (C)> ALEADI: Aluminum ethyl acetoacetate diisopropylate ALTAA: Aluminum trisacetylacetonate ZNBAA: Zinc bisacetylacetonate <Other crosslinks (D)> TGXDA: N,N,N',N'-tetraglycidyl-m-xylylenediamine HMBTAP: 2,2-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate] <Organosilane compounds> GPTMS: 3-glycidoxypropyltrimethoxysilane

[0118] <Measurement and evaluation of physical properties of adhesive sheets> Using the obtained pressure-sensitive adhesive sheet, the storage modulus and loss factor were measured to calculate G'(-20), G'(-20) / G'(200), and tan δ(-20) / tan δ(200), and the gel fraction, transparency, heat resistance, moist heat resistance, dynamic bending resistance, static bending resistance, and winding property were evaluated by the following methods. The results are shown in Tables 2, 3, and 4.

[0119] <Gel fraction> The obtained adhesive sheet was cut into a size of 25 mm wide x 100 mm long. One release film of the cut adhesive sheet was peeled off, and the sheet was attached to a 200 mesh of 50 mm wide x 120 mm long, whose mass had been measured in advance. Next, the other release film was peeled off, and the mesh was folded so that the adhesive was on the inside so that the adhesive was not exposed. The adhesive wrapped in the mesh was immersed in about 50 mL of ethyl acetate at 50 ° C for 1 day, and the sol component of the adhesive was dissolved out of the mesh. After immersion, the adhesive wrapped in the mesh was taken out, dried at 100 ° C for 1 hour, and allowed to cool for about 20 minutes, and then the dry mass was measured. The gel fraction of the adhesive was calculated by the following formula. Gel fraction (mass%) = (Y / X) x 100 X = mass of adhesive layer before immersion (g) Y = mass of adhesive layer after immersion (g)

[0120] <Preparation of test adhesive sheets> The 38 μm-thick release film was peeled off from the obtained adhesive sheet, and the exposed adhesive layer was attached to a 50 μm-thick PET film (T60, manufactured by Toray Industries, Inc.) using a laminator at 23°C and 50% RH to produce a test adhesive sheet consisting of PET film / adhesive layer / release film.

[0121] <Transparency> The test adhesive sheet was cut to a size of 112 mm wide x 200 mm long (equivalent to a 9-inch display). The release film was removed from the cut test adhesive sheet, and the exposed adhesive layer was attached to an alkali-free glass plate (EN-A1: manufactured by Asahi Glass Co., Ltd.) using a laminator in an atmosphere of 25°C and 50% RH, and the haze was measured. The haze was measured using a Turbidimeter NDH5000W manufactured by Nippon Denshoku Industries Co., Ltd. The evaluation criteria were as follows: That is correct. [Evaluation Criteria] ○: Haze is less than 1.0 (good). ×: Haze is 1.0 or more (poor).

[0122] <Heat resistance / humid heat resistance> The release film was peeled off from a test pressure-sensitive adhesive sheet prepared separately, and the exposed pressure-sensitive adhesive layer was attached to a polarizing plate (layer structure: triacetyl cellulose film / polyvinyl alcohol film / cycloolefin film) using a laminator in an atmosphere of 25°C and 50% RH. A test laminate consisting of an ET film / adhesive layer / polarizing plate was obtained. Next, as a heat resistance test, the laminate was left to stand for 500 hours under a condition of 105°C, and then cooled in an atmosphere of 25°C and 50% RH. The generation of air bubbles and the lifting or peeling of the test laminate were visually evaluated under the following conditions. In addition, the humidity and heat resistance The test laminate was left in an atmosphere of 60°C and 95% RH for 500 hours, then cooled in an atmosphere of 25°C and 50% RH, and visually evaluated for the generation of air bubbles and the lifting or peeling of the adhesive sheet under the following conditions. Heat resistance and moist heat resistance were evaluated based on the following three-level evaluation criteria. [Evaluation Criteria] ⊚: No air bubbles, floating or peeling were observed, and there were no problems in practical use. ◯: Air bubbles, lifting, or peeling was observed in less than five places, but this did not cause any problems in practical use. ×: Air bubbles, floating or peeling were observed in 5 or more places, and the product was problematic for practical use.

[0123] <Dynamic flex resistance: flex resistance [1], [2], [3]> The release film was peeled off from a test pressure-sensitive adhesive sheet prepared separately, and the exposed pressure-sensitive adhesive layer was attached to a polarizing plate (layer structure: triacetyl cellulose film / polyvinyl alcohol film / cycloolefin film) using a laminator in an atmosphere of 25°C and 50% RH. A test laminate consisting of ET film / adhesive layer / polarizing plate was obtained. Next, the test laminate was subjected to a normal test of bending resistance at 25°C and 50% RH atmosphere [1], a heat resistance test of bending resistance at 85°C atmosphere [2], and a moist heat resistance test of bending resistance at 60°C and 95% RH atmosphere [3], with the conditions set so that the inner diameter (diameter) when folded was 6 mm using a folding tester (manufactured by Yuasa System Co., Ltd.), and 300,000 cycles were repeated, with folding and opening at 180° as one cycle. The dynamic bending resistance was evaluated based on the appearance after the test from the following perspectives. Appearance: The test laminate was visually inspected for the presence or absence of air bubbles and the presence or absence of lifting or peeling of the adhesive layer under the following conditions. [Evaluation Criteria] ⊚: No air bubbles, floating or peeling were observed, and there were no problems in practical use. ◯: Air bubbles, lifting, or peeling was observed in less than five places, but this did not cause any problems in practical use. ×: Air bubbles, floating or peeling were observed in 5 or more places, and the product was problematic for practical use.

[0124] <Static bending resistance: Flexing resistance [1], [2], [3]> The release film was peeled off from a test pressure-sensitive adhesive sheet prepared separately, and the exposed pressure-sensitive adhesive layer was attached to a polarizing plate (layer structure: triacetyl cellulose film / polyvinyl alcohol film / cycloolefin film) using a laminator in an atmosphere of 25°C and 50% RH. A test laminate consisting of ET film / adhesive layer / polarizing plate was obtained. Next, the test laminate was subjected to bending resistance [1] in a normal state test at 25°C and 50% RH, bending resistance [2] in a heat resistance test at 85°C, and bending resistance [3] in a moist heat resistance test at 60°C and 95% RH, using a planar body no-load U-shaped stretch tester, with the polarizing plate side of the test piece facing inward, bending at a bending radius of 3 mm and a bending angle of 180° for 240 hours. Static bending resistance was evaluated by the appearance after the test from the following viewpoints. Appearance: The test laminate was visually inspected for the presence or absence of air bubbles and the presence or absence of lifting or peeling of the adhesive layer under the following conditions. [Evaluation Criteria] ⊚: No air bubbles, floating or peeling were observed, and there were no problems in practical use. ◯: Air bubbles, lifting, or peeling was observed in less than five places, but this did not cause any problems in practical use. ×: Air bubbles, floating or peeling were observed in 5 or more places, and the product was problematic for practical use.

[0125] <Windability> The release film was peeled off from a test pressure-sensitive adhesive sheet prepared separately, and the exposed pressure-sensitive adhesive layer was attached to a polarizing plate (layer structure: triacetyl cellulose film / polyvinyl alcohol film / cycloolefin film) using a laminator in an atmosphere of 25°C and 50% RH. A test laminate consisting of an ET film / adhesive layer / polarizing plate was obtained. Next, the test laminate was wound up in the long direction around a metal bar with a radius of 3 mm, with the PET side of the test piece facing inward, and then rolled up. After forming the laminate into a roll, it was tied in place with string at three points. For the winding test, the rolled test laminate was kept in an atmosphere of 25°C and 50% RH for 240 hours. The winding property was evaluated based on the appearance after the test from the following perspectives. Appearance: The test laminate was visually inspected for the presence or absence of air bubbles and the presence or absence of lifting or peeling of the adhesive layer under the following conditions. [Evaluation Criteria] ⊚: No air bubbles, floating or peeling were observed, and there were no problems in practical use. ◯: Air bubbles, lifting, or peeling was observed in less than five places, but this did not cause any problems in practical use. ×: Air bubbles, floating or peeling were observed in 5 or more places, and the product was problematic for practical use.

[0126] [Table 4]

[0127] The abbreviations in the table are as follows. Layer structure of test pressure-sensitive adhesive sheet and test laminate [A]: PET film / adhesive layer / glass [B]: PET film / adhesive layer / polarizing plate Test conditions Bending resistance [1]: 25℃, 50% RH atmosphere Bending resistance [2]; 85℃ atmosphere Bending resistance [3]: 60℃, 95% RH atmosphere

[0128] From the results in Table 4, it was confirmed that the pressure-sensitive adhesive sheets of Examples 1 to 18 were excellent in heat resistance, moist heat resistance, flexibility and windability in addition to transparency. As a result, the laminate and display using the pressure-sensitive adhesive sheet of the present invention were excellent in transparency, heat resistance, moist heat resistance and flexibility. Furthermore, the display of the present invention was also excellent in visibility and contrast. On the other hand, the pressure-sensitive adhesive sheets of Comparative Examples 1 to 12 could not satisfy all of the above characteristics. [Explanation of symbols]

[0129] 1 Adhesive layer 1 2 Release film 3. Light-transmitting substrate (cover panel) 4. Polarizing Plate 5 Adhesive layer 2 6 Barrier Layer 7 Organic EL layer 8 Support 9 Organic EL Cell

Claims

1. The composition comprises an acrylic copolymer (A), an isocyanate compound (B) and a metal chelate compound (C), The acrylic copolymer (A) is a copolymer of a monomer mixture containing the following monomers (a-1), (a-2) and (a-3): A pressure-sensitive adhesive characterized by satisfying all of the following (1) to (3): (a-1) (Meth)acrylic acid alkyl ester monomer having an alkyl group with 8 to 12 carbon atoms (a-2) Monomer having a hydroxyl group (a-3) Monomer that forms a chelate crosslink with a metal compound (1) 3.0×10 ４ P<G'(-20)<4.0×10 ５ P (2) 5<G'(-20) / G'(200)<17 (3) 2<tanδ(-20) / tanδ(200)<6 Here, in the above formula, G'(-20) is the storage modulus at -20°C and 1 Hz G'(200) is the storage modulus at 200°C and 1 Hz tan δ(-20) is the loss tangent at -20°C and 1Hz tan δ(200) is the loss tangent at 200° C. and 1 Hz Each refers to:

2. The acrylic copolymer (A) contains, in 100% by mass of the monomer mixture, 20 to 98% by mass of monomer (a-1); 0.2 to 2 mass% of monomer (a-2); The pressure-sensitive adhesive according to claim 1, comprising 0.2 to 5 mass% of monomer (a-3).

3. The pressure-sensitive adhesive according to claim 1, comprising 0.5 to 5 mass% of an isocyanate compound (B) and 0.2 to 2 mass% of a metal chelate compound (C) relative to 100 mass% of the acrylic copolymer (A).

4. The pressure-sensitive adhesive according to claim 1, characterized in that the gel fraction is 60 to 90 mass %.

5. 5. A pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer, the pressure-sensitive adhesive layer being a cured product of the pressure-sensitive adhesive according to claim 1, sandwiched between release films.

6. 5. A laminate comprising a light-transmitting substrate, a pressure-sensitive adhesive layer, and a polarizing plate, the pressure-sensitive adhesive layer being a cured product of the pressure-sensitive adhesive according to claim 1.

7. A display comprising the laminate according to claim 6 and an optical element.

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