Adhesive, adhesive layer formed from said adhesive, adhesive sheet and laminate including said adhesive layer, and display including said laminate

Abstract

To provide an adhesive that can contribute to the conservation of petroleum resources, has both moist heat resistance and heat resistance, and is excellent in corrosion resistance, and to provide an adhesive sheet, a laminate, and a device with an adhesive layer that use the same. [Solution] An adhesive comprising a copolymer or partial copolymer of a monomer mixture containing a nitrogen-containing monomer selected from 2-octyl (meth)acrylate, a cyclic amide-containing monomer, and a monomer containing both a nitrogen atom and a hydroxy group in the molecule, and optionally containing a hydroxy group-containing monomer, a monomer whose homopolymer has a glass transition temperature of -20.1°C or higher, and a carboxy group-containing monomer.

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive, a pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive, a pressure-sensitive adhesive sheet and a laminate comprising the pressure-sensitive adhesive layer, and a display comprising the laminate. [Background technology]

[0002] Because adhesive sheets having an adhesive layer formed from an adhesive are easy to handle, they are used in a wide range of fields, including label applications and medical applications. Furthermore, adhesives have been used to bond components of various devices, such as smartphones and televisions. Among these, adhesives used in applications where long-term use is expected, such as marking films, window films, automotive components, and optical displays, require durability, including heat resistance and moist heat resistance. Furthermore, when adhesive sheets are bonded to metal substrates, corrosion of the substrate due to components contained in the adhesive can cause deterioration of the product, so adhesives with corrosion resistance are in demand.

[0003] Patent Document 1 discloses a technology that suppresses peeling and lifting in high-temperature, high-humidity environments by incorporating a hydroxyl group- and alkylene oxide group-containing acrylic copolymer and a polyfunctional isocyanate curing agent to build an interpenetrating network structure in the cured state. However, the pressure-sensitive adhesive described in Patent Document 1 has the problem that when left in a high-temperature, high-humidity environment for a long period of time, the alkylene oxide groups decompose, causing peeling and lifting.

[0004] Furthermore, Patent Document 2 discloses a technology that prevents lifting and peeling of an adhesive sheet when placed in a high-temperature, high-humidity environment for a long period of time by containing an acrylic copolymer containing hydroxyl groups and carboxyl groups, a mercapto group-containing silane compound, and an alcohol. However, because the adhesive described in Patent Document 2 uses a highly volatile silane compound, when the adhesive is coated and dried, the silane compound volatilizes, and a sufficient amount of the silane compound does not remain in the adhesive layer after coating, resulting in the problem of lifting and peeling.

[0005] In addition to the above-mentioned increasing performance requirements, the depletion of petroleum resources and carbon dioxide emissions from the combustion of petroleum-derived products are becoming issues in the industries in which PSA sheets are used. Therefore, attempts are being made to conserve petroleum resources by using bio-derived materials instead of petroleum-derived materials in a variety of industries, starting with the packaging materials field, as well as in the optical and semiconductor fields. One method for increasing the proportion of biologically derived materials in adhesives whose main component is an acrylic polymer is to obtain an acrylic polymer by copolymerizing a monomer mixture containing a (meth)acrylic acid alkyl ester monomer obtained by esterifying a linear alkyl alcohol produced by living organisms with (meth)acrylic acid. Furthermore, there are also tackifying resins made from naturally derived ingredients, and by selectively using these, it is possible to achieve environmentally friendly products. Increasing the proportion of environmentally friendly materials can contribute to the conservation of petroleum resources, but the current situation is that only limited environmentally friendly materials are used, and there are challenges to putting this into practical use. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-55299 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-59711 Summary of the Invention [Problem to be solved by the invention]

[0007] The problem that the present invention aims to solve is to provide an adhesive that can contribute to the conservation of petroleum resources, that has both moist heat resistance and heat resistance and has excellent corrosion resistance, an adhesive sheet using the same, a laminate, and a display including the laminate. [Means for solving the problem]

[0008] As a result of extensive research, the present inventors have found that the problems of the present invention can be solved by the following aspects, and have thus completed the present invention. That is, the present invention provides a pressure-sensitive adhesive comprising a copolymer (A1) obtained by polymerizing the entire monomer mixture or a partial copolymer (A2) obtained by partially polymerizing the monomer mixture, wherein the monomer mixture comprises the following monomer (a1) and monomer (a2), and optionally the following monomer (a3), monomer (a4), and monomer (a5): (a1) 2-octyl (meth)acrylate (a2) a nitrogen-containing monomer selected from a cyclic amide-containing monomer and a monomer containing both a nitrogen atom and a hydroxy group in the molecule; (a3) Hydroxy group-containing monomers (excluding monomer (a2)) (a4) Monomers whose homopolymer glass transition temperature is -20.1°C or higher (excluding monomers (a2), (a3) ​​and (a5)) (a5) Carboxy group-containing monomer [Effects of the Invention]

[0009] The present invention makes it possible to provide an adhesive that can contribute to the conservation of petroleum resources, has both moist heat resistance and heat resistance, and has excellent corrosion resistance, as well as an adhesive sheet and laminate using the same, and a display including the laminate. [Brief explanation of the drawings]

[0010] [Figure 1]1 is a schematic cross-sectional view partially illustrating a laminate of the present invention. [Figure 2] FIG. 1 is a schematic cross-sectional view partially illustrating a display, which is an example of the use of the laminate of the present invention. [Figure 3] 1 is a schematic cross-sectional view partially illustrating a pressure-sensitive adhesive sheet of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] The pressure-sensitive adhesive, pressure-sensitive adhesive sheet, and device including a pressure-sensitive adhesive layer according to the present disclosure have the following configurations [1] to

[13] .

[0012] [1] A copolymer (A1) obtained by polymerizing the entire monomer mixture or a partial copolymer (A2) obtained by partially polymerizing the monomer mixture, A pressure-sensitive adhesive, wherein the monomer mixture contains the following monomer (a1) and monomer (a2), and optionally contains the following monomer (a3), monomer (a4), and monomer (a5). (a1) 2-octyl (meth)acrylate (a2) a nitrogen-containing monomer selected from a cyclic amide-containing monomer and a monomer containing both a nitrogen atom and a hydroxy group in the molecule; (a3) Hydroxy group-containing monomers (excluding monomer (a2)) (a4) Monomers whose homopolymer glass transition temperature is -20.1°C or higher (excluding monomers (a2), (a3) ​​and (a5)) (a5) Carboxy group-containing monomer [2] The adhesive according to [1], comprising, in 100% by mass of the monomer mixture, 50.1% by mass or more and less than 99.5% by mass of the monomer (a1) and 0.5% by mass or more and less than 49.9% by mass of the monomer (a2). [3] The pressure-sensitive adhesive according to [1] or [2], wherein the monomer (a3) ​​is contained in an amount of 5.1% by mass or more relative to 100% by mass of the monomer mixture. [4] The pressure-sensitive adhesive according to any one of [1] to [3], wherein the monomer (a4) is contained in an amount of 5.1% by mass or more relative to 100% by mass of the monomer mixture. [5] The pressure-sensitive adhesive according to any one of [1] to [4], wherein the monomer (a4) includes a monomer having a glass transition temperature of 0°C or higher. [6] The pressure-sensitive adhesive according to any one of [1] to [5], which contains a partial copolymer (A2) of the monomer mixture and further contains a polyfunctional compound (b) having two or more unsaturated double bond groups. [7] The pressure-sensitive adhesive according to [6], which contains 0.01 to 10 parts by mass of the polyfunctional compound (b) per 100 parts by mass of the partial copolymer (A2). [8] The pressure-sensitive adhesive according to any one of [1] to [7], wherein the gel fraction is 40% by mass or more. [9] The pressure-sensitive adhesive according to any one of [1] to [8], which does not contain a solvent.

[10] A pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive according to any one of [1] to [9].

[11] An adhesive sheet comprising the adhesive layer according to

[10] and a release film.

[12] A laminate comprising the pressure-sensitive adhesive layer according to

[10] and a substrate.

[13] A display comprising the laminate according to

[12] , a polarizing plate, and an optical element.

[0013] The pressure-sensitive adhesive, pressure-sensitive adhesive layer, pressure-sensitive adhesive sheet, laminate and display including the laminate of the present invention will be described below, but the present invention is not limited thereto. In this specification, "(meth)acrylate" collectively refers to acrylate and methacrylate, and "(meth)acryloxy group" collectively refers to acryloxy group and methacryloxy group. A "monomer" is a monomer having one ethylenically unsaturated group. Furthermore, in this specification, a numerical range specified using "to" includes the numerical values ​​before and after "to" as the range of the lower and upper limits. Furthermore, "film" and "sheet" are not distinguished by thickness. In other words, in this specification, "sheet" includes thin film-like products, and "film" in this specification includes thick sheet-like products. Furthermore, the term "adherend" refers to a counterpart to which the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is attached. Unless otherwise noted, the various components appearing in this specification may be used independently either alone or in combination of two or more.

[0014] <Adhesive> The pressure-sensitive adhesive of the present invention contains a copolymer (A1) obtained by polymerizing the entire monomer mixture or a partial copolymer (A2) obtained by partially polymerizing the monomer mixture. In this specification, the copolymer (A1) and the partial copolymer (A2) may be collectively referred to as resin (A). In cases where solvent-free adhesives are required in light of recent global environmental issues and working environments, partial copolymer (A2) may be used as the adhesive. By including partial copolymer (A2), the adhesive can be cured by active energy rays, making it possible to obtain a solvent-free adhesive. In the present invention, "containing no solvent" refers to an embodiment in which no intentionally added solvent is contained.

[0015] <Copolymer (A1)> Copolymer (A1) is a copolymer obtained by polymerizing a monomer mixture containing monomers (a1) and (a2) and optionally containing monomers (a3), (a4), and (a5). Copolymer (A1) obtained by polymerizing the entire monomer mixture can be used substantially alone as a pressure-sensitive adhesive. (a1) 2-octyl (meth)acrylate (a2) a nitrogen-containing monomer selected from a cyclic amide-containing monomer and a monomer containing both a nitrogen atom and a hydroxy group in the molecule (a3) Hydroxy group-containing monomers (excluding monomer (a2)) (a4) Monomers whose homopolymer glass transition temperature is -20.1°C or higher (excluding monomers (a2), (a3) ​​and (a5)) (a5) Carboxy group-containing monomer

[0016] The weight-average molecular weight of the copolymer (A1) is not particularly limited, but is preferably not more than 2,000,000, and more preferably not more than 1,000,000. The weight-average molecular weight is a value measured by gel permeation chromatography (GPC) in terms of polystyrene.

[0017] <Monomer (a1)> The monomer (a1) is a biomass monomer represented by the following general formula (1). (General formula 1) JPEG0007750443000002.jpg54167(R1=H, CH3) The content of 2-octyl (meth)acrylate is not particularly limited, but in order to simultaneously satisfy all evaluations such as moist heat resistance, heat resistance, corrosion resistance, and SUS adhesion strength, it is preferably 30% by mass or more, and more preferably 40% by mass or more. A 2-octyl (meth)acrylate content of 50.1% by mass or more can contribute to the conservation of petroleum resources. Therefore, considering both physical properties and environmental considerations, the 2-octyl (meth)acrylate content is preferably 50.1% by mass or more in 100% by mass of the monomer mixture. Since a higher content of 2-octyl (meth)acrylate, a biomass monomer, contributes to the conservation of petroleum resources, a higher content of 55% by mass or more, 59% by mass or more, or 65% by mass or more is preferable. Furthermore, in relation to the content of monomer (a2), the 2-octyl (meth)acrylate content is preferably less than 99.5% by mass in 100% by mass of the monomer mixture. Depending on the content of monomer (a3), monomer (a4), and monomer (a5), which can be optionally contained in the monomer mixture, the upper limit of the 2-octyl (meth)acrylate content may be 94% by mass or less, or even 89% by mass or less.

[0018] <Monomer (a2)> Monomer (a2) is a nitrogen-containing monomer selected from cyclic amide-containing monomers and monomers containing both a nitrogen atom and a hydroxy group in the molecule. Examples of the cyclic amide-containing monomer (a2) include, but are not limited to, 4-acryloylmorpholine, 1-acryloylpiperidin-2-one, etc. Examples of the monomer containing both a nitrogen atom and a hydroxy group in the molecule include, but are not limited to, N-(2-hydroxymethyl)acrylamide, N-(2-hydroxyethyl)acrylamide, etc. The content of monomer (a2) is not particularly limited, but is preferably 0.5% by mass or more and less than 49.9% by mass, more preferably 0.5% by mass or more and less than 39.9% by mass, even more preferably 0.5% by mass or more and less than 29.9% by mass, particularly preferably 0.5% by mass or more and less than 19.9% ​​by mass, and most preferably 0.5% by mass or more and less than 10.9% by mass in terms of evaluation of moist heat resistance, heat resistance, corrosion resistance, SUS adhesion strength, etc., relative to 100% by mass of the monomer mixture.

[0019] <Monomer (a3)> Monomer (a3) ​​is a monomer having a hydroxy group (excluding monomer (a2)). Monomers that contain a hydroxy group but also a nitrogen atom are classified as monomer (a2). Examples of the monomer (a3) ​​include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Of these, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred from the viewpoints of adhesive strength and resistance to moist heat. Monomer (a3) ​​may or may not be contained in the monomer mixture. If it is contained, it is preferably 5.1% by mass or more, more preferably 7% by mass or more, and even more preferably 9% by mass or more, based on 100% by mass of the monomer mixture. By making the content of monomer (a3) ​​5.1% by mass or more, moist heat resistance can be improved. Furthermore, it is preferably less than 40% by mass, more preferably less than 29% by mass, based on 100% by mass of the monomer mixture. By making the content of monomer (a3) ​​less than 40% by mass, it is possible to reduce the initial haze of the adhesive while maintaining appropriate cohesive strength.

[0020] <Monomer (a4)> The monomer (a4) is a monomer (excluding the monomers (a2), (a3) ​​and (a5)) whose homopolymer has a glass transition temperature of −20.1° C. or higher. The glass transition temperature (°C) of the homopolymer is the value disclosed by the distributor of the various monomers, and if it is unknown, it can be found from the value listed in "Polymer Handbook 3rd Edition" (A Wiley-Interscience Publication, 1989). Examples of monomer (a4) include: Examples of the vinyl acrylate include tetrahydrofurfuryl acrylate, 2-ethylhexyl methacrylate, diethylaminoethyl methacrylate, hexyl methacrylate, isopropyl acrylate, lauryl acrylate, vinyl acetate, acrylamide, N,N-dimethylacrylamide, methacrylonitrile, acrylonitrile, diacetone acrylamide, methyl (meth)acrylate, ethyl methacrylate, ter-butyl methacrylate, sec-butyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, isopropyl methacrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, and phenyl (meth)acrylate. In terms of improving cohesive strength and adhesive strength, it is more preferable to use monomers whose homopolymer glass transition temperatures are 0°C or higher, such as vinyl acetate, acrylamide, N,N-dimethylacrylamide, methacrylonitrile, acrylonitrile, diacetone acrylamide, methyl (meth)acrylate, ethyl methacrylate, ter-butyl methacrylate, sec-butyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, isopropyl methacrylate, stearyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, and phenyl (meth)acrylate. In consideration of the environment, it is more preferable to use, as the monomer (a4), a biomass monomer selected from the group consisting of hexyl methacrylate, lauryl acrylate, isobornyl (meth)acrylate, and stearyl (meth)acrylate.

[0021] Monomer (a4) may or may not be contained in the monomer mixture. If it is contained, it is preferably present in an amount of 5.1% by mass or more, more preferably 10.1% by mass or more, even more preferably 20.1% by mass or more, and even more preferably 30.1% by mass or more, based on 100% by mass of the monomer mixture. By adjusting the content of monomer (a4) to 5.1% by mass or more, cohesive strength and adhesive strength can be increased. Furthermore, it is preferably present in less than 50% by mass, more preferably less than 40% by mass, based on 100% by mass of the monomer mixture. By adjusting the content of monomer (a4) to less than 50% by mass, appropriate cohesive strength can be exerted, and sufficient initial tackiness can be obtained for adhesion to the adherend.

[0022] <Monomer (a5)> The monomer (a5) is a monomer having a carboxy group. The carboxy group-containing monomer is not limited as long as it has a carboxy group in the molecule, and specific examples include (meth)acrylic acid, p-carboxybenzyl acrylate, β-carboxyethyl acrylate, maleic acid, monoethyl maleate, itaconic acid, citraconic acid, and fumaric acid. Of these, (meth)acrylic acid is preferred from the viewpoint of adhesive strength, and acrylic acid is more preferred.

[0023] Monomer (a5) may or may not be contained in the monomer mixture, but if it is contained, the content is preferably less than 3 mass % and more preferably less than 0.5 mass % in 100 mass % of the monomer mixture in order to prevent corrosion of the adherend by acid. By including the monomer (a5), the cohesive strength of the adhesive layer is increased, and the adhesive strength and heat resistance are easily improved. From the viewpoint of imparting cohesive strength and heat resistance, the content is preferably 0.05% by mass or more, and more preferably 0.09% by mass or more.

[0024] <Other monomers> The monomer mixture may contain monomers other than the monomers (a1) to (a5). When other monomers are contained, it is preferable to use biomass monomers in consideration of the environment.

[0025] Examples of other monomers include sec-butyl acrylate, n-octyl methacrylate, phenoxyethyl acrylate, ethyl acrylate, polycaprolactone acrylate, isobutyl acrylate, 2-acryloyloxyethyl succinic acid, n-butyl acrylate, n-heptyl acrylate, 2-ethylhexyl acrylate, 2-methoxyethyl acrylate, vinyl propyl ether, isooctyl acrylate, n-hexyl acrylate, n-nonyl methacrylate, vinyl butyl ether, n-octyl acrylate, lauryl methacrylate, ethyl carbitol acrylate (2-(2-ethoxyethoxy)ethyl)acrylate, n-decyl methacrylate, and butoxytriethylene glycol methacrylate. In terms of versatile use, phenoxyethyl acrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, n-octyl acrylate, and lauryl methacrylate are more preferred, and biomass monomers such as n-heptyl acrylate, n-butyl acrylate, n-octyl acrylate, and lauryl methacrylate are even more preferred.

[0026] The monomer mixture may or may not contain other monomers, but if it does contain other monomers, it is preferable that the amount is less than 25% by mass relative to 100% by mass of the monomer mixture.

[0027] <Method for producing copolymer (A1)> The copolymer (A1) can be produced by known polymerization methods such as solution polymerization, bulk polymerization, emulsion polymerization, and suspension polymerization.

[0028] 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.

[0029] The polymerization initiator used for 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; Cumene hydroperoxide, diisopropylbenzene hydroperoxide, 2,5 -Hydroperoxides such as 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.

[0030] Examples of the azo compound include 2,2'-azobisbutyronitrile such as 2,2'-azobisisobutyronitrile (abbreviation: AIBN) and 2,2'-azobis(2-methylbutyronitrile); 2,2'-azobisvaleronitrile 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'-azobis(cyclohexane-1-carbonitrile).

[0031] The polymerization initiator may be used alone or in combination of two or more kinds, and is preferably used in an amount of 0.01 to 10 parts by mass, more preferably 0.03 to 5 parts by mass, and even more preferably 0.1 to 2 parts by mass, per 100 parts by mass of the monomer mixture.

[0032] <Partial copolymer (A2)> The partial copolymer (A2) is obtained by partially polymerizing a monomer mixture containing the above-mentioned monomers (a1) and (a2) and optionally containing monomers (a3), (a4), and (a5) in the presence of a polymerization initiator by heating, irradiating with radiation, etc. The partial copolymer (A2) can be used alone as an adhesive, but it is preferable to use it in combination with a polyfunctional compound (b) from the viewpoints of adhesive strength and heat resistance.

[0033] <Method for producing partial copolymer (A2)> The partial copolymer (A2) is preferably produced by a curing reaction using a polymerization initiator such as a photopolymerization initiator, with heat or active energy rays (for example, ultraviolet rays).

[0034] Examples of the photopolymerization initiator include benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, and acylphosphine oxide-based photopolymerization initiators. Examples of the benzoin ether-based photopolymerization initiator include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethan-1-one (manufactured by BASF, trade name: Irgacure 651), anisole methyl ether, etc. Examples of the acetophenone-based photopolymerization initiator include 1-hydroxycyclohexyl phenyl ketone (manufactured by BASF, trade name: Irgacure 184), 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one (manufactured by BASF, trade name: Irgacure 2959), 2-hydroxy-2-methyl-1-phenyl-propan-1-one (manufactured by BASF, trade name: Darocure 1173), and methoxyacetophenone. Examples of the α-ketol photopolymerization initiator include 2-methyl-2-hydroxypropiophenone, 1-[4-(2-hydroxyethyl)-phenyl]-2-hydroxy-2-methylpropan-1-one, and the like. Examples of the aromatic sulfonyl chloride photopolymerization initiator include 2-naphthalenesulfonyl chloride. Examples of the photoactive oxime photopolymerization initiator include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. Examples of the benzoin photopolymerization initiator include benzoin. Examples of the benzyl photopolymerization initiator include benzil. Examples of the benzophenone photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexylphenyl ketone, and the like. Examples of the ketal photopolymerization initiator include benzil dimethyl ketal. Examples of the thioxanthone-based photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, and dodecylthioxanthone. Examples of the acylphosphine photopolymerization initiator include bis(2,6-dimethoxybenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)(2,4,4-trimethylpentyl)phosphine oxide, bis(2,6-dimethoxybenzoyl)-n-butylphosphine oxide, bis(2,6-dimethoxybenzoyl)-(2-methylpropan-1-yl)phosphine oxide, bis(2,6-dimethoxybenzoyl)-(1-methylpropan-1-yl)phosphine oxide, bis(2,6-dimethoxybenzyl)-(1-methylpropan-1-yl)phosphine oxide, and bis(2,6-dimethoxybenzyl)phenylphosphine oxide. bis(2,6-dimethoxybenzoyl)-t-butylphosphine oxide, bis(2,6-dimethoxybenzoyl)cyclohexylphosphine oxide, bis(2,6-dimethoxybenzoyl)octylphosphine oxide, bis(2-methoxybenzoyl)(2-methylpropan-1-yl)phosphine oxide, bis(2-methoxybenzoyl)(1-methylpropan-1-yl)phosphine oxide, bis(2,6-diethoxybenzoyl)(2-methylpropan-1-yl)phosphine oxide, bis(2,6-diethoxybenzoyl)(1-methylpropane -1-yl)phosphine oxide, bis(2,6-dibutoxybenzoyl)(2-methylpropan-1-yl)phosphine oxide, bis(2,4-dimethoxybenzoyl)(2-methylpropan-1-yl)phosphine oxide, bis(2,4,6-trimethylbenzoyl)(2,4-dipentoxyphenyl)phosphine oxide, bis(2,6-dimethoxybenzoyl)benzylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2-phenylpropylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2- Phenylethylphosphine oxide, bis(2,6-dimethoxybenzoyl)benzylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2-phenylpropylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2-phenylethylphosphine oxide, 2,6-dimethoxybenzoylbenzylbutylphosphine oxide, 2,6-dimethoxybenzoylbenzyloctylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,5-diisopropylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2-methylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-4-methylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,5-diethylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,3,5,6-tetramethylphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,4-di-n-butoxyphenylphosphine oxide, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis(2,6-dimethoxybenzoyl )-2,4,4-trimethylpentylphosphine oxide, bis(2,4,6-trimethylbenzoyl)isobutylphosphine oxide, 2,6-dimethythoxybenzoyl-2,4,6-trimethylbenzoyl-n-butylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)-2,4-dibutoxyphenylphosphine oxide, 1,10-bis[bis(2,4,6-trimethylbenzoyl)phosphine oxide]decane, tri(2-methylbenzoyl)phosphine oxide, etc.

[0035] The polymerization initiator may be used alone or in combination of two or more kinds, and is preferably used in an amount of 0.01 to 10 parts by mass, more preferably 0.03 to 5 parts by mass, and even more preferably 0.1 to 2 parts by mass, per 100 parts by mass of the monomer mixture.

[0036] When activating the photopolymerization initiator, it is important to irradiate the monomer composition containing the photopolymerization initiator with active energy rays. Examples of such active energy rays include ionizing radiation such as α-rays, β-rays, γ-rays, neutron beams, and electron beams, as well as ultraviolet rays, with ultraviolet rays being particularly preferred. Furthermore, the irradiation energy, irradiation time, and irradiation method of the active energy rays are not particularly limited, and any irradiation method may be used as long as it can activate the photopolymerization initiator and cause a reaction of the monomer components.

[0037] <Polyfunctional compound (b)> Examples of the polyfunctional compound (b) having two or more unsaturated double bond groups include hexanediol di(meth)acrylate, butanediol di(meth)acrylate, nonanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, trimethylolpropane tri(meth)acrylate, tetramethylolmethane tri(meth)acrylate, allyl (meth)acrylate, vinyl (meth)acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, urethane acrylate, etc. The polyfunctional compound (b) may be used alone or in combination of two or more. The polyfunctional compound (b) is preferably a polyfunctional (meth)acrylate, and from the viewpoint of ease of handling, hexanediol di(meth)acrylate, nonanediol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, and trimethylolpropane tri(meth)acrylate are preferred.

[0038] The content of the polyfunctional compound (b) having two or more unsaturated double bond groups is preferably 0.01 to 10 parts by mass, more preferably 0.02 to 5 parts by mass, and even more preferably 0.1 to 3 parts by mass, per 100 parts by mass of the partial copolymer (A2) of the monomer mixture. When the pressure-sensitive adhesive containing the partial copolymer contains the polyfunctional compound (b), the cohesive strength of the pressure-sensitive adhesive layer increases, and the adhesive strength and heat resistance tend to be improved.

[0039] The pressure-sensitive adhesive of the present invention may contain a curing agent as needed, and may also contain additives such as a silane coupling agent, a tackifying resin, and an antioxidant.

[0040] <Curing agent> The pressure-sensitive adhesive of the present invention may contain a curing agent. The curing agent may be any agent that provides a crosslinked structure to the pressure-sensitive adhesive. The addition of a curing agent improves the cohesive strength of the pressure-sensitive adhesive layer, and improves the adhesive strength, heat resistance, and light resistance. The curing agent preferably contains at least one selected from the group consisting of an isocyanate-based curing agent, an epoxy-based curing agent, and an aluminum chelate-based curing agent. The inclusion of at least one of an isocyanate-based curing agent, an epoxy-based curing agent, and an aluminum chelate-based curing agent is preferred in that it can appropriately increase the cohesive strength of the adhesive and is less likely to adversely affect other physical properties. As long as the adhesive contains at least one of an isocyanate-based curing agent, an epoxy-based curing agent, and an aluminum chelate-based curing agent, known curing agents other than an isocyanate-based curing agent, an epoxy-based curing agent, and an aluminum chelate-based curing agent may be used in combination.

[0041] The isocyanate curing agent is an isocyanate having two or more isocyanate groups. Examples of the isocyanate include aromatic polyisocyanates, aliphatic polyisocyanates, araliphatic polyisocyanates, alicyclic polyisocyanates, and their biuret forms, nurate forms, and adduct forms, and from the viewpoint of yellowing resistance, aliphatic polyisocyanates, alicyclic polyisocyanates, and their biuret forms, nurate forms, and adduct forms are more preferred.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] Examples of alicyclic polyisocyanates include 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, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), and 1,4-bis(isocyanatemethyl)cyclohexane.

[0046] The biuret compound is a self-condensation product having a biuret bond formed by self-condensation of an isocyanate monomer, such as a biuret compound of hexamethylene diisocyanate.

[0047] The nurate derivative 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.

[0048] The adduct is a bifunctional or higher isocyanate compound obtained by reacting an isocyanate monomer with a bifunctional or higher low-molecular-weight 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.

[0049] From the viewpoint of forming a sufficient crosslinked structure, the isocyanate compound is preferably a trifunctional isocyanate compound. The isocyanate compound is more preferably an adduct or nurate, which is a reaction product of an isocyanate monomer and a trifunctional low-molecular-weight active hydrogen-containing compound. 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.

[0050] Examples of epoxy curing agents 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.

[0051] The aluminum chelate curing agent is not particularly limited as long as it has a chelating ligand and has the function of forming a crosslinked structure with the crosslinkable resin. The chelating ligand may be a bidentate ligand or a multidentate ligand (e.g., tridentate or higher), and examples thereof include β-diketonates such as acetylacetonate, benzoylacetonate, and methyl acetylacetonate; and β-ketoester anions such as methyl acetoacetate and ethyl acetoacetate.

[0052] Specific examples of aluminum chelate curing agents include aluminum (ethyl acetoacetate) diisopropylate, aluminum tris(acetylacetonate), aluminum tris(ethyl acetoacetate), and aluminum bis(ethyl acetoacetate) mono(acetylacetonate). These aluminum chelate curing agents may be used either individually or in combination of two or more.

[0053] The curing agent is preferably contained in an amount of 0.02 to 4 parts by mass, more preferably 0.04 to 1 part by mass, per 100 parts by mass of resin (A). When the content is 0.02 part by mass or more, the cohesive strength is further improved, and when it is 4 parts by mass or less, it becomes easier to achieve both cohesive strength and flexibility, making it easier to obtain sufficient adhesive strength, heat resistance, and light resistance.

[0054] <Silane coupling agent> The pressure-sensitive adhesive of the present invention may contain a silane coupling agent. By containing a silane coupling agent, adhesive strength, heat resistance, resistance to moist heat whitening, and light resistance can be improved. The silane coupling agent is preferably contained in an amount of 0.05 to 0.2 parts by mass per 100 parts by mass of resin (A). By containing 0.05 to 0.2 parts by mass, moist heat resistance and heat resistance can be imparted.

[0055] Examples of the silane coupling agent include an alkoxysilane compound having a (meth)acryloxy group, an alkoxysilane compound having a vinyl group, an alkoxysilane compound having an amino group, an alkoxysilane compound having a mercapto group, and an alkoxysilane compound having an epoxy group. Specific examples of commercially available products include KBM-403 (3-glycidoxypropyltrimethoxysilane), KBE-403 (3-glycidoxypropyltriethoxysilane), KBM-303 (2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane) (all manufactured by Shin-Etsu Chemical Co., Ltd.), and BYK-325N (polyether-modified polymethylalkylsiloxane) (manufactured by BYK Japan KK).

[0056] <Tackifying resin> The pressure-sensitive adhesive of the present invention may further contain a tackifying resin. Examples of tackifying resins that can be used include aliphatic petroleum resins, aromatic petroleum resins, synthetic hydrocarbon resins, terpene resins, rosin resins (rosin, polymerized rosin, hydrogenated rosin, and their esters with glycerin, pentaerythritol, etc., resin acid dimers, etc.), and acrylic resins. The tackifying resins may be used alone or in combination of two or more.

[0057] Aliphatic petroleum resins include Quinton B170 manufactured by Zeon Corporation, aromatic petroleum resins include Nisseki Neopolymer L-90 manufactured by JXTG, and aliphatic / aromatic petroleum resins. Examples of the rosin derivative include FTR6100 manufactured by Mitsui Chemicals, Inc., and SylvatacRE85 manufactured by Arizona Chemical Company, Inc. and Super Ester A-75 manufactured by Arakawa Chemical Industries, Ltd.

[0058] Examples of synthetic hydrocarbon resins include aliphatic petroleum resins, aromatic petroleum resins, aliphatic / aromatic petroleum resins, hydrogenated petroleum resins, coumarone-indene resins, and phenol resins.

[0059] Examples of terpene resins include α-pinene resins, β-pinene resins, dipentene resins, aromatic modified terpene resins, hydrogenated terpene resins, terpene phenol resins, acid modified terpene resins, styrenated terpene resins, and styrene-aliphatic hydrocarbon copolymer resins. It can be obtained.

[0060] Examples of rosin-based resins include rosin ester, polymerized rosin, hydrogenated rosin, disproportionated rosin, maleic acid-modified rosin, fumaric acid-modified rosin, rosin phenolic resin, and natural rosin.

[0061] The content of the tackifier resin is preferably less than 50 parts by mass, and more preferably 40 parts by mass or less, per 100 parts by mass of resin (A). By including a tackifier resin, the adhesive strength to the adherend can be improved.

[0062] In addition, it is more preferable to use a tackifier resin with a biomass content of 80% or more in consideration of the environment. Furthermore, the softening point of the tackifier resin is preferably a higher softening point grade in terms of improving heat resistance, and is preferably 90°C or higher, more preferably 120°C or higher, and even more preferably 140°C or higher.

[0063] The pressure-sensitive adhesive of the present invention may contain various resins, chlorinated polyolefins described below, oils, softeners, dyes, pigments, antioxidants, and ultraviolet absorbers as optional components, as long as the problem can be solved.

[0064] Examples of chlorinated polyolefins include chlorinated polypropylene, acid-modified chlorinated polypropylene, acrylic-modified chlorinated polypropylene, chlorinated polyethylene, and chlorinated ethylene vinyl acetate copolymer. From the viewpoints of good compatibility with acrylic polymers and the like and effective reduction of polarity, chlorinated polypropylene and chlorinated ethylene vinyl acetate copolymer are preferred. Specific examples of commercially available products include Superchlorine 390S (chlorinated polypropylene, chlorine content 36%) and Superchlorine BX (chlorinated EVA, chlorine content 18%) (both manufactured by Nippon Paper Industries Co., Ltd.).

[0065] The pressure-sensitive adhesive of the present invention preferably has a gel fraction of 40% or more. However, depending on the application, a gel fraction of 40% or less may also be used. The method for measuring the gel fraction will be described in detail in the Examples.

[0066] <Adhesive layer> The pressure-sensitive adhesive layer is a layer formed from the pressure-sensitive adhesive of the present invention. There are no particular restrictions on the method for forming the pressure-sensitive adhesive layer, and it can be the same as the coating method described below in the description of the pressure-sensitive adhesive sheet.

[0067] <Adhesive sheet> The pressure-sensitive adhesive sheet comprises a pressure-sensitive adhesive layer made of the pressure-sensitive adhesive of the present invention and a release film.

[0068] The pressure-sensitive adhesive sheet of the present invention may have a release film formed on one or both sides of the pressure-sensitive adhesive layer. An example of a schematic cross-sectional view partially illustrating the pressure-sensitive adhesive sheet of the present invention is shown in Figure 3. In Figure 3, 3 is a light-transmitting substrate (cover panel), 1 is a pressure-sensitive adhesive layer, and 2 is a release film.

[0069] The adhesive sheet of the present invention preferably has a higher SUS adhesive strength for the purpose of product fixation, etc. Although a lower adhesive strength may be used depending on the product, for versatile use, a peel strength of 8 N / 25 mm or more is preferred. The measurement method is described in detail in the Examples.

[0070] <Release film> The release film is not particularly limited, but a transparent plastic substrate can be suitably used. Examples of materials for the transparent plastic substrate include polyesters such as polyethylene terephthalate (PET), acrylic resins such as polymethyl methacrylate (PMMA), and plastic materials such as polycarbonate, triacetyl cellulose, polysulfone, polyarylate, and polycycloolefin. The plastic materials can be used alone or in combination of two or more.

[0071] Among the transparent plastic substrates described above, a transparent plastic substrate having excellent heat resistance, i.e., a transparent plastic substrate that is suppressed or prevented from deforming under severe conditions such as high temperature, high temperature and high humidity, etc. PET films or sheets are particularly suitable as the transparent plastic substrate.

[0072] The thickness of the release film is preferably less than 200 μm. The thickness should be adjusted depending on the handling of the member to be used, but by being less than 200 μm, the material itself is not too stiff, making it easy to wind into a roll and allowing for comfortable use when laminating sheets or the like.

[0073] The pressure-sensitive adhesive sheet of the present invention has excellent adhesive properties and is therefore suitable as an adhesive for forming optical display components such as display devices such as LCDs and OLEDs, and input devices such as touch panels, or for bonding these components together. Examples of optical components include, but are not limited to, PET films, polarizing plates, retardation plates, elliptically polarizing plates, optical compensation films, brightness-enhancing films, infrared / electromagnetic wave-blocking films, front-surface anti-reflection films, surface protection films, films with an ITO (indium tin oxide) layer, films with a zinc oxide (ZnO) layer, films obtained by coating or printing metal nanoparticles, films obtained by coating or printing a dispersion containing carbon nanotubes, films obtained by coating or printing a dispersion containing graphene, films obtained by coating or printing a dispersion containing a conductive polymer, metal plates made of SUS or the like, metal meshes, and laminates of these.

[0074] The thickness of the transparent plastic substrate is not particularly limited, and is, for example, preferably from 10 to 200 μm, more preferably from 25 to 150 μm.

[0075] When applying the adhesive, the viscosity can be adjusted by adding an appropriate liquid medium. Specific examples include hydrocarbon solvents such as toluene, xylene, hexane, and heptane; ester solvents such as ethyl acetate and butyl acetate; ketone solvents such as acetone and methyl ethyl ketone; halogenated hydrocarbon solvents such as dichloromethane and chloroform; ether solvents such as diethyl ether, methoxytoluene, and dioxane, and other hydrocarbon solvents. However, water and alcohol must be used with caution because they may inhibit the reaction between the resin (A) and the isocyanate curing agent.

[0076] The coating method is not particularly limited, and examples thereof include various coating methods using a Mayer bar, applicator, brush, spray, roller, gravure coater, die coater, lip coater, comma coater, knife coater, reverse coater, spin coater, etc. The drying and curing method is also not particularly limited, and examples thereof include hot air drying, infrared rays, reduced pressure methods, and methods using active energy rays, but hot air or steam heating at 60 to 180°C is preferred from the viewpoint of outgassing resistance.

[0077] The thickness of the adhesive layer is preferably 2 to 1000 μm, more preferably 5 to 500 μm. The adhesive layer may be in the form of a single layer or a laminate of two or more layers.

[0078] <Laminate> The laminate of the present invention includes a substrate and a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer is formed using the pressure-sensitive adhesive sheet of the present invention. Specifically, for example, the release film is peeled off from the pressure-sensitive adhesive sheet of the present invention, and the pressure-sensitive adhesive layer is attached to the substrate to form the laminate.

[0079] <Base material> The substrate refers to the object to which the adhesive layer of the adhesive sheet having an adhesive layer is attached, and is not limited to a specific material. Examples include polyolefins such as polyethylene and polypropylene, acrylic resins such as polymethyl methacrylate (PMMA), resins such as polycarbonate and phenol, metals such as iron, stainless steel (SUS), aluminum and copper, cement, mortar, glass, nonwoven fabric, woven fabric, paper, rubber, foam sheets, and laminates thereof. The adhesive of the present invention exhibits excellent adhesive strength to at least one type of adherend. The thickness of the substrate is not particularly limited, and is, for example, preferably less than 500 μm, more preferably 10 to 200 μm, and even more preferably 25 to 150 μm.

[0080] An example of a schematic cross-sectional view partially showing the laminate of the present invention is shown in Figure 1. In Figure 1, 3 is a light-transmitting substrate (cover panel), 1 is a pressure-sensitive adhesive layer, and 4 is a polarizing plate.

[0081] In the laminate shown in FIG. 1, a light-transmitting substrate (cover panel) is attached to a polarizing plate via an adhesive layer.

[0082] <Production of laminate> The laminate can be produced, for example, by peeling off one release film from a pressure-sensitive adhesive sheet having release films on both sides of the pressure-sensitive adhesive layer and attaching the pressure-sensitive adhesive layer to a substrate. Alternatively, the laminate can be produced by directly forming a pressure-sensitive adhesive layer on a substrate, and then attaching a pressure-sensitive adhesive layer provided on the substrate or another pressure-sensitive adhesive sheet to the pressure-sensitive adhesive layer.

[0083] Display A display includes the laminate of the present invention, a polarizing plate, and an optical element, thereby providing the display with excellent visibility. The optical element is not particularly limited, and examples thereof include a liquid crystal element and an organic EL element.

[0084] Figure 2 shows an example of a schematic cross section partially illustrating a display, which is an example of use of the pressure-sensitive adhesive sheet of the present invention. In Figure 2, 3 is a light-transmitting substrate (cover panel), 1 is pressure-sensitive adhesive layer 1, 4 is a polarizing plate, 5 is 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 Figure 2.

[0085] 2, a light-transmitting substrate (cover panel) is attached to a polarizing plate via the pressure-sensitive adhesive layer of the present invention (pressure-sensitive adhesive layer 1), and is further attached to an organic EL cell via a pressure-sensitive adhesive layer for polarizing plate (pressure-sensitive adhesive layer 2). In this way, the pressure-sensitive adhesive sheet of the present invention can be used in a form in which a transparent pressure-sensitive adhesive layer formed from the pressure-sensitive 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 a pressure-sensitive adhesive layer for polarizing plate. For example, in FIG. 2, the pressure-sensitive adhesive layer of the present invention can be used as either pressure-sensitive adhesive layer 1 or pressure-sensitive adhesive layer 2. Generally, when comparing pressure-sensitive adhesive layer 1 and pressure-sensitive adhesive layer 2, the quality requirements for the pressure-sensitive adhesive layer are higher for pressure-sensitive adhesive layer 1, and the pressure-sensitive adhesive of the present invention has good adhesion and bonding properties to the substrate, so 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.

[0086] There are no particular limitations on the uses of the displays, but examples include OLED televisions, OLED smartphones, OLED tablets, and OLED smartwatches.

[0087] In light of the recent trend toward environmentally friendly materials, the adhesive of the present invention can be made partially or entirely from biologically derived materials by using a biomass monomer as the monomer constituting the resin (A) or by using a biomass tackifier. The biomass ratio is preferably 30% or more. The higher the biomass ratio, more preferably 39% or more, and even more preferably 60% or more, the greater the usefulness as an environmentally friendly material. The method for calculating the biomass ratio is described in the Examples. [Example]

[0088] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples. In the examples, unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass." The blending amounts in the tables are in parts by mass, and all amounts other than the solvent are calculated as non-volatile content. Blank spaces in the tables indicate that no blending was performed.

[0089] <Measurement of weight average molecular weight (Mw)> The weight-average molecular weight (Mw) was measured by gel permeation chromatography (GPC). The instrument used was a GPC instrument manufactured by Shimadzu Corporation: an LC-GPC system "Prominence." The columns used were TSKgel α-M manufactured by Tosoh Corporation, with two columns connected in series. N,N-dimethylformamide (DMF) was used as the eluent, and measurements were carried out at 40°C. Mw was determined by conversion using polystyrene with a known Mw as the standard substance.

[0090] (Production of copolymers of monomer mixtures) Example 1: Preparation of (A1-1) Using a reaction apparatus equipped with a stirrer, a reflux condenser, a nitrogen inlet tube, a thermometer, and a dropping tube, ethyl acetate was added to a reaction vessel as a polymerization solvent, and a monomer mixture of 32.5 parts of 2-octyl acrylate (2-OA), 5 parts of 4-acryloylmorpholine, 7 parts of 2-hydroxyethyl acrylate (HEA), 5 parts of 4-hydroxybutyl acrylate (4HBA), and 0.5 parts of isobutyl methacrylate (iBMA), and 0.04 parts of azobisisobutyronitrile as an initiator was charged into the reaction vessel. A mixture of 32.5 parts of 2-octyl acrylate (2-OA), 5 parts of 4-acryloylmorpholine, 7 parts of 2-hydroxyethyl acrylate (HEA), 5 parts of 4-hydroxybutyl acrylate (4HBA), and 0.5 parts of isobutyl methacrylate (iBMA), ethyl acetate as the polymerization solvent, and 0.02 parts of azobisisobutyronitrile as the initiator, was added dropwise from the dropping tube over approximately 2 hours and polymerized at approximately 80°C for 6 hours under a nitrogen atmosphere. After the reaction was completed, the mixture was cooled and diluted with ethyl acetate to obtain a solution of the copolymer of the monomer mixture. The resulting copolymer of the monomer mixture was designated A1-1. The weight-average molecular weight of A1-1 was approximately 600,000.

[0091] <Examples 2 to 17, Comparative Production Examples 1 to 3: Production of (A1-2 to A1-17, A'-1 to A'-3)> Copolymers of the monomer mixture (A1-2 to A1-17, A'-1 to A'-3) were produced in the same manner as in the production of the copolymer of the monomer mixture (Example 1), except for changing the compositions and blending amounts (parts by mass) to those shown in Tables 1 and 3. The weight-average molecular weight of each copolymer was 500,000 to 800,000.

[0092] (Production of partial copolymer of monomer mixture) Example 18: Preparation of (A2-1) A monomer mixture of 95 parts 2-octyl acrylate (2-OA), 2 parts N-(2-hydroxymethyl)acrylamide, and 3 parts 4-hydroxybutyl acrylate (4HBA) was mixed with 0.04 parts 1-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator, and then irradiated with ultraviolet light until the viscosity (B-type viscometer No. 22 rotor, 12 rpm, measurement temperature: 25°C) reached 1 Pa·s or higher, resulting in a partial copolymer in which some of the above monomer components had polymerized. The resulting partial copolymer of the monomer mixture is designated A2-1.

[0093] <Examples 19 to 25, Comparative Production Examples 4 and 5: Production of (A2-2 to A2-8, A'-4 and A'-5)> Copolymers of the monomer mixture (A2-2 to A2-8, A'-4 to A'-5) were produced in the same manner as the production of the partial copolymer of the monomer mixture (Example 18), except that the compositions and blending amounts (parts by mass) were changed to those shown in Tables 2 and 3.

[0094] [Table 1]

[0095] [Table 2]

[0096] [Table 3]

[0097] The abbreviations are as follows: Regarding biomass content, only confirmed cases are listed. [Monomer (a1): 2-octyl (meth)acrylate] 2-OA: 2-octyl acrylate (Nippon Shokubai Co., Ltd., biomass content 73%) 2-OMA: 2-octyl methacrylate (manufactured by Sanwa Chemifa Co., Ltd., biomass content 67%) [Monomer (a2): Nitrogen-containing monomer selected from cyclic amide-containing monomers and monomers containing both a nitrogen atom and a hydroxy group in the molecule] N-(2-hydroxyethyl)acrylamide N-(2-hydroxymethyl)acrylamide 4-Acryloylmorpholine 1-Acryloylpiperidin-2-one [Monomer (a3): Hydroxy group-containing monomer] HEA: Hydroxyethyl acrylate 4HBA: 4-hydroxy-normal butyl acrylate [Monomer (a4): A monomer having a homopolymer glass transition temperature of -20.1°C or higher] MA: methyl acrylate (Tg: 6°C) iBMA: isobutyl methacrylate (Tg: 48°C) IBXA: Isobornyl acrylate (Osaka Organic Chemical Industry Co., Ltd., biomass content 76%, Tg: 94°C) VAc: vinyl acetate (Tg: 28°C) THFA: tetrahydrofurfuryl acrylate (Osaka Organic Chemical Industry Co., Ltd., biomass content 62%, Tg: -12°C) LA: Lauryl acrylate (Osaka Organic Chemical Industry Co., Ltd., biomass content 80%, Tg: -3°C) [Monomer (a5): Carboxy group-containing monomer] AA: acrylic acid [Other monomers] BA: n-butyl acrylate (manufactured by Sanwa Chemifa Co., Ltd., biomass content 57%, Tg: -48°C) HA: n-heptyl acrylate (manufactured by Sanwa Chemifa Co., Ltd., biomass content 70%, Tg: -57°C)

[0098] <Example 26> A mixture was obtained by blending 0.2 parts of "D-165N" (a biuret of hexamethylene diisocyanate, manufactured by Mitsui Chemicals, Inc.) as a curing agent with 100 parts of copolymer (A1-1) of the monomer mixture. This mixture was applied using a comma coater to a 38 μm thick release liner (SP-PET-O1-BU: manufactured by Mitsui Chemicals Tohcello Co., Ltd.) so that the dry thickness would be 25 μm. After drying at 110 ° C for 3 minutes, a 75 μm thick release liner (SP-PET-O3-B3: manufactured by Mitsui Chemicals Tohcello Co., Ltd.) was laminated to the adhesive layer as a release sheet. The mixture was then aged at 23 ° C for 7 days to obtain a pressure-sensitive adhesive sheet.

[0099] <Examples 27 to 44, Comparative Examples 1 to 3> As shown in Table 4, pressure-sensitive adhesive sheets were obtained in the same manner as in Example 26, except that the type and amount of copolymer in the monomer mixture, the type of curing agent, and the amount of silane coupling agent added were changed.

[0100] Example 45 As shown in Table 4, a pressure-sensitive adhesive sheet was obtained in the same manner as in Example 26, except that copolymer (A1-11) of the monomer mixture was used as the pressure-sensitive adhesive.

[0101] <Example 46> To 100 parts of the partial copolymer (A2-1) of the monomer mixture obtained in Example 18, 0.3 parts of TMPTA (trimethylolpropane triacrylate) as a polyfunctional compound and 1.5 parts of 1-hydroxycyclohexylphenyl ketone as a photopolymerization initiator were added to obtain a mixture. This mixture was coated to a thickness of 25 μm on a 38 μm thick release liner (SP-PET-O1-BU: manufactured by Mitsui Chemicals Tohcello Co., Ltd.) as a release sheet using a comma coater, and a 75 μm thick release liner (SP-PET-O3-B3: manufactured by Mitsui Chemicals Tohcello Co., Ltd.) as another release sheet was laminated to the coated surface. The coating layer was then exposed to an integrated light dose of 1200 mJ / cm. 2 The coating layer was cured by irradiation with ultraviolet light of 1000 kJ / cm 2 to obtain a pressure-sensitive adhesive layer.

[0102] <Examples 47 to 54, Comparative Examples 4 and 5> As shown in Table 4, an adhesive sheet was obtained in the same manner as in Example 46, except that the type of partial copolymer of the monomer mixture, the type and amount of polyfunctional compound, and the amount of silane coupling agent were changed.

[0103] Example 55 As shown in Table 4, an adhesive sheet was obtained in the same manner as in Example 46, except that 0.3 parts of TMPTA (trimethylolpropane triacrylate) as a polyfunctional compound and 0.05 parts of "D-165N" (a biuret form of hexamethylene diisocyanate, manufactured by Mitsui Chemicals, Inc.) as a curing agent were blended with 100 parts of the partial copolymer (A2-7) of the monomer mixture.

[0104] <Gel fraction measurement> The 38 μm release liner was peeled off from the resulting pressure-sensitive adhesive sheet, and the pressure-sensitive adhesive layer was attached to a PET film substrate (Cosmoshine A-4360, 100 μm thick, manufactured by Toyobo Co., Ltd.), which was then cut into a size of 30 mm wide x 100 mm long to prepare a test pressure-sensitive adhesive sheet. The release liner on the other side of the pressure-sensitive adhesive tape was then peeled off to prepare a test specimen, whose weight was measured. The test specimen was immersed in ethyl acetate at 23°C for 24 hours, then removed from the ethyl acetate and dried at 150°C for 30 minutes. The weight of the dried test specimen was measured, and the gel fraction was calculated using the following formula (1). In Table 3, "40%≦" means that the gel fraction was 40% or more, and "40%>" means that the gel fraction was less than 40%. Gel fraction (wt%) = 100 × (W2 − W0) / (W1 − W0) (1) (W0: weight of substrate (PET film), W1: weight of test piece before immersion, W2: weight of test piece after immersion and drying)

[0105] <Biomass ratio calculation> The biomass ratio of the adhesive was calculated using the following formula (2). (In the case of a system consisting of two monomer components (A, B) and one tackifier component (C)) Biomass degree = {(Aw × Ab) + (Bw × Bb) + (Cw × Cb)} / (Aw + Bw + C w) (2) Aw: weight of monomer A, Bw: weight of monomer B, Cw: weight of tackifier Ab: Biomass ratio of monomer A (%), Bb: Biomass ratio of monomer B (%) Cb: Biomass ratio of monomer C (%) When the biomass degree was specified as a range, the minimum value was used in the calculation.

[0106] The materials used in the examples and comparative examples are listed below. <Polyfunctional compound (b)> HDDA: hexanediol diacrylate TMPTA: Trimethylolpropane triacrylate <Curing agent> D-165N: Mitsui Chemicals, hexamethylene diisocyanate biuret Tetrad X: Mitsubishi Gas Chemical Company, multifunctional epoxy resin Aluminum chelate A: Chelate hardener manufactured by Kawaken Fine Chemicals Co., Ltd.

[0107] <Silane coupling agent> KBE-403: (3-glycidoxypropyltriethoxysilane, manufactured by Shin-Etsu Chemical Co., Ltd.)

[0108] The pressure-sensitive adhesive layers obtained in Examples 26 to 55 and Comparative Examples 1 to 5 were evaluated for moist heat resistance, heat resistance, and corrosion resistance by the methods described below. Furthermore, the adhesive strength of the pressure-sensitive adhesive layers to SUS was measured as a basic physical property of the pressure-sensitive adhesive. The results are shown in Table 5.

[0109] <Moisture and heat resistance> The 38 μm release liner was peeled off from the resulting pressure-sensitive adhesive sheet, and the pressure-sensitive adhesive layer was attached to a glass plate using a laminator in an atmosphere of 23 ° C - 50% RH. Next, the other 75 μm release liner was peeled off from the pressure-sensitive adhesive sheet, and the sheet was attached to a glass plate using a laminator in the same manner as above. This was held for 20 minutes under a pressure of 0.5 MPa in an atmosphere of 50 ° C to prepare a test piece laminated in the order of glass plate / pressure-sensitive adhesive layer / glass plate, and then left for 200 hours in an environment of 60 ° C and 90% relative humidity (also referred to as 60 ° C - 90% RH). Each was cooled at 23 ° C - 50% RH for 1 hour to obtain a test piece. Each test piece was visually inspected and evaluated according to the following criteria. [Evaluation criteria] A: 80% or more of the test piece area is transparent: Excellent B: 60% or more but less than 80% of the test piece area is transparent: Good C: 40% or more but less than 60% of the test piece area is transparent: Usable D: Less than 40% of the test piece area is transparent: too cloudy and unusable

[0110] <Heat resistance> After preparing a test piece by cutting the obtained adhesive sheet into a size of 25 mm in width and 100 mm in length, the 38-μm release liner of the test piece was peeled off in an atmosphere of 23°C - 50% RH and then adhered onto SUS. A hand roller weighing 2 kg was reciprocated once for crimping so that the adhesion area was 25 mm in width × 40 mm in length. After standing for 24 hours in an atmosphere of 23°C - 50% RH, a load of 500 g was applied and the test piece was left standing in an 80°C environment for 10 hours. Using a microscope, the displacement of the test piece after 10 hours was measured and evaluated based on the following criteria. A: The displacement of the test piece is less than 0.1 mm: Excellent B: The displacement of the test piece is 0.1 mm or more and less than 0.4 mm: Good C: The displacement of the test piece is 0.4 mm or more and less than 10 mm: Usable D: The displacement of the test piece is 10 mm or more: Unusable

[0111] <Corrosion resistance> After laminating the adhesive sheet onto an aluminum foil, it was left standing for 48 hours under high-temperature and high-humidity conditions of 60°C × 90% RH. Then, the adhesive sheet was peeled off from the aluminum foil, and the surface of the aluminum foil was visually inspected and evaluated according to the following criteria. A: No discoloration was confirmed on the surface of the aluminum foil: Good B: Partial discoloration was confirmed on the surface of the aluminum foil: Usable C: Overall discoloration was confirmed on the surface of the aluminum foil: Unusable

[0112] <Adhesive strength to SUS> The 38-μm release liner of the obtained adhesive sheet was peeled off, and the adhesive layer was laminated onto a PET film (manufactured by Toyobo Co., Ltd., Cosmo Shine A-4360, thickness 100 μm) as a base material. A test adhesive sheet was prepared by cutting it into a size of 25 mm in width × 100 mm in length. The other 75-μm release liner of this test adhesive sheet was peeled off, and in an atmosphere of 23°C - relative humidity 50% (50% RH), the adhesive layer was adhered onto a glass plate and further crimped with a roll according to JIS Z-0237. After 24 hours had elapsed since crimping, the peel strength (peel angle 180°, peel speed 300 mm / min; unit N / 25 mm width) was measured using a tensile testing machine (Tensilon: manufactured by Orientec Co., Ltd.). [Evaluation criteria] A: Peel strength is 15N / 25mm or more: Good B: Peel strength is 8N / 25mm or more, less than 15N / 25mm: Usable C: Peel strength less than 8N / 25mm: Unusable

[0113] [Table 4]

[0114] [Table 5] [Explanation of symbols]

[0115] The symbols in Figures 1, 2 and 3 are explained below. 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 cells

Claims

1. The copolymer (A1) is obtained by polymerizing the entire monomer mixture, or the partial copolymer (A2) is obtained by partially polymerizing the monomer mixture, The monomer mixture contains the following monomer (a1), monomer (a2), and monomer (a3), and optionally contains the following monomer (a4) and monomer (a5), The monomer mixture contains, based on 100% by mass, 50.1 to 94% by mass of the following monomer (a1), 0.5% by mass or more but less than 10.9% by mass of the following monomer (a2), and 5.1% by mass or more but less than 29% by mass of the following monomer (a3), A pressure-sensitive adhesive, in which the content of the following monomer (a4) is less than 40% by mass and the content of the following monomer (a5) is less than 3% by mass, based on 100% by mass of the monomer mixture. (a1) 2-octyl (meth)acrylate (a2) A nitrogen-containing monomer selected from a cyclic amide-containing monomer and a monomer containing both a nitrogen atom and a hydroxy group in the molecule (excluding N-vinyl-2-pyrrolidone). (a3) Hydroxy group-containing monomers (excluding monomer (a2)) (a4) A monomer having a glass transition temperature of -20.1°C or higher as a homopolymer (excluding the monomers (a2), (a3) ​​and (a5)). (a5) Carboxy group-containing monomer

2. In 100% by mass of the monomer mixture, The pressure-sensitive adhesive according to claim 1, comprising 5.1 mass% or more of the monomer (a4).

3. The pressure-sensitive adhesive according to claim 1, wherein the monomer (a4) contains a monomer whose homopolymer has a glass transition temperature of 0°C or higher.

4. The pressure-sensitive adhesive according to claim 1, which comprises a partial copolymer (A2) of the monomer mixture and further comprises a polyfunctional compound (b) having two or more unsaturated double bond groups.

5. The pressure-sensitive adhesive according to claim 4, comprising 0.01 to 10 parts by mass of the polyfunctional compound (b) per 100 parts by mass of the partial copolymer (A2).

6. The pressure-sensitive adhesive according to claim 1, which has a gel fraction of 40% by mass or more.

7. The adhesive according to claim 1, wherein the adhesive does not contain a solvent.

8. A pressure-sensitive adhesive layer formed from the pressure-sensitive adhesive according to any one of claims 1 to 7.

9. A pressure-sensitive adhesive sheet comprising the pressure-sensitive adhesive layer according to claim 8 and a release film.

10. A laminate comprising the pressure-sensitive adhesive layer according to claim 8 and a substrate.

11. A display comprising the laminate according to claim 10, a polarizing plate, and an optical element.

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