Adhesive, adhesive layer formed from the adhesive, adhesive sheet and laminate having the adhesive layer, and display having the laminate

Abstract

To provide an adhesive that can contribute to the conservation of petroleum resources, possessing both moisture and heat resistance, heat resistance, and excellent corrosion resistance, as well as adhesive sheets, laminates, and devices with adhesive layers using the same. [Solution] A sticky adhesive comprising a copolymer or partial copolymer of a monomer mixture containing 2-octyl (meth)acrylate, a nitrogen-containing monomer selected from cyclic amide-containing monomers and monomers containing both a nitrogen atom and a hydroxyl group in the molecule, and optionally containing a hydroxyl group-containing monomer, a monomer whose homopolymer has a glass transition temperature of -20.1°C or higher, and a carboxyl 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 provided with the pressure-sensitive adhesive layer, and a display provided with the laminate. [Background Art]

[0002] Pressure-sensitive adhesive sheets having a pressure-sensitive adhesive layer formed from a pressure-sensitive adhesive are used in a wide range of fields such as labeling applications and medical applications due to their ease of handling. Furthermore, pressure-sensitive adhesives have been used for bonding between members of various devices such as smartphones and televisions. Among these, pressure-sensitive adhesives used in applications expected to be used for a long period of time, such as marking films, window films, automotive members, and optical displays, require durability such as heat resistance and moist heat resistance. Furthermore, in applications where a pressure-sensitive adhesive sheet is bonded to a metal adherend or the like, corrosion of the adherend caused by components contained in the pressure-sensitive adhesive may lead to deterioration of the product, so a pressure-sensitive adhesive having corrosion resistance is desired.

[0003] Patent Document 1 discloses a technique in which an acrylic copolymer containing a hydroxy group and an alkylene oxide group and a polyfunctional isocyanate curing agent are contained to construct an interpenetrating network structure in a cured state, thereby suppressing lifting and peeling under high-temperature and high-humidity environments. However, when the pressure-sensitive adhesive described in Patent Document 1 is left in a high-temperature and high-humidity environment for a long period of time, there is a problem that decomposition of alkylene oxide groups occurs, resulting in lifting and peeling.

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

[0005] In addition to the increasing performance requirements mentioned above, the depletion of petroleum resources and the emission of carbon dioxide from the combustion of petroleum-derived products are becoming serious concerns in industries where adhesive sheets are used. Therefore, starting with the packaging materials sector, and continuing into various industries such as optics and semiconductors, efforts are being made to conserve petroleum resources by using bio-derived materials instead of petroleum-derived materials. In adhesives primarily composed of acrylic polymers, one method for improving the proportion of bio-derived materials is to copolymerize a monomer mixture containing an alkyl (meth)acrylate monomer obtained by esterifying a linear alkyl alcohol produced from a biological source with (meth)acrylic acid to obtain an acrylic polymer. Furthermore, there are adhesive resins made from naturally derived ingredients, and by selectively using these, it is possible to achieve environmentally friendly product development. While increasing the proportion of environmentally friendly materials can contribute to greater conservation of petroleum resources, the current situation is that it poses challenges to practical application because it limits the use of environmentally friendly materials. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2014-55299 [Patent Document 2] Japanese Patent Publication No. 2004-59711 [Overview of the project] [Problems that the invention aims to solve]

[0007] The problem that this invention aims to solve is to provide an adhesive that can contribute to the conservation of petroleum resources, possesses both moisture and heat resistance, heat resistance, and excellent corrosion resistance, as well as an adhesive sheet using the same, a laminate, and a display equipped with the laminate. [Means for solving the problem]

[0008] After diligent research by the inventors, we discovered that the problems of the present invention can be solved in the following embodiment, and thus completed the present invention. In other words, the present invention is an adhesive comprising a copolymer (A1) obtained by the complete polymerization of a monomer mixture or a partially copolymer (A2) obtained by the partial polymerization of a monomer mixture, wherein the monomer mixture comprises 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) Nitrogen-containing monomers selected from cyclic amide-containing monomers and monomers containing both a nitrogen atom and a hydroxyl group in the molecule (a3) Hydroxyl 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 provides an adhesive that can contribute to the conservation of petroleum resources, possessing both moisture and heat resistance, heat resistance, and excellent corrosion resistance, as well as an adhesive sheet using the same, a laminate, and a display equipped with the laminate. [Brief explanation of the drawing]

[0010] [Figure 1]This is a schematic cross-sectional view partially showing the laminate of the present invention. [Figure 2] This is a schematic cross-sectional view partially showing a display, which is an example of the use of the laminate of the present invention. [Figure 3] This is a schematic cross-sectional view showing a portion of the adhesive sheet of the present invention. [Modes for carrying out the invention]

[0011] The device comprising the adhesive, adhesive sheet, and adhesive layer according to this disclosure has the following configurations [1] to

[13] .

[0012] [1] A copolymer (A1) obtained by polymerizing all of the monomer mixture or a partially polymerized copolymer (A2) obtained by partially polymerizing the monomer mixture, An adhesive comprising a monomer mixture containing the following monomers (a1) and (a2), and optionally containing the following monomers (a3), (a4), and (a5). (a1)2-Octyl(meth)acrylate (a2) Nitrogen-containing monomers selected from cyclic amide-containing monomers and monomers containing both a nitrogen atom and a hydroxyl group in the molecule (a3) Hydroxyl 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 50.1% by mass or more and less than 99.5% by mass of monomer (a1) and 0.5% by mass or more and less than 49.9% by mass of monomer (a2) in 100% by mass of the monomer mixture. [3] The adhesive according to [1] or [2], comprising 5.1% by mass or more of monomer (a3) ​​in 100% by mass of the monomer mixture. [4] The adhesive according to any one of [1] to [3], comprising 5.1% by mass or more of monomer (a4) in 100% by mass of the monomer mixture. [5] The pressure-sensitive adhesive according to any one of [1] to [4], wherein the monomer (a4) comprises 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], comprising a partial copolymer (A2) of a monomer mixture, and further comprising a polyfunctional compound (b) having two or more unsaturated double bond groups. [7] The pressure-sensitive adhesive according to [6], comprising 0.01 to 10 parts by mass of the polyfunctional compound (b) relative to 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 is characterized by not containing a solvent.

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

[11] A pressure-sensitive adhesive sheet comprising the pressure-sensitive 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] Hereinafter, the pressure-sensitive adhesive, pressure-sensitive adhesive layer, pressure-sensitive adhesive sheet, laminate, and display comprising the laminate of the present invention will be described, but the present invention is not limited thereto. In this specification, the term "(meth)acrylate" is a generic term collectively referring to acrylate and methacrylate respectively, and the term "(meth)acryloxy group" is a generic term collectively referring to acryloxy group and methacryloxy group respectively. A monomer is a monomer having one ethylenically unsaturated group. In addition, in this specification, a numerical range specified by using "~" shall include the numerical values described before and after "~" as the range of lower limit and upper limit. Furthermore, the terms "film" and "sheet" are not distinguished by thickness. In other words, the term "sheet" in this specification includes thin film-shaped products, and the term "film" in this specification includes thick sheet-shaped products. Furthermore, the adherend refers to a target to which the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheet is attached. Unless otherwise noted, each of the components mentioned herein may be used independently, individually, or in combination of two or more.

[0014] Adhesive The adhesive of the present invention comprises a copolymer (A1) obtained by the complete polymerization of a monomer mixture, or a partially copolymer (A2) obtained by the partial polymerization of a monomer mixture. In this specification, copolymer (A1) and partially copolymer (A2) may be collectively referred to as resin (A). In cases where solvent-free materials are required due to current global environmental concerns or working environment requirements, an adhesive containing a partial copolymer (A2) can be used. Because the adhesive containing a partial copolymer (A2) can be cured by active energy rays, it can be made solvent-free. In this invention, "solvent-free" refers to a configuration in which no solvent has been intentionally added.

[0015] <Copolymer (A1)> Copolymer (A1) is a copolymer obtained by polymerizing all monomer mixtures containing monomers (a1) and (a2), and optionally containing monomers (a3), (a4), and (a5). Copolymer (A1), obtained by polymerizing all monomer mixtures, can be used substantially on its own as an adhesive. (a1)2-Octyl(meth)acrylate (a2) Nitrogen-containing monomers selected from cyclic amide-containing monomers and monomers containing both nitrogen atoms and hydroxyl groups in the molecule (a3) Hydroxyl 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 copolymer (A1) is not particularly limited, but is preferably 2 million or less, and more preferably 1 million or less. The weight-average molecular weight is the polystyrene equivalent value measured by gel permeation chromatography (GPC).

[0017] <Monomer (a1)> Monomer (a1) is a biomass monomer represented by the following general formula (1). (General formula 1) JPEG2026142652000002.jpg54167(R1=H, CH3) The content of 2-octyl(meth)acrylate is not particularly limited, but to achieve a balance of moisture and heat resistance, heat resistance, corrosion resistance, and SUS adhesion strength, it is preferable to have 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 enhances the contribution to petroleum resource conservation. Therefore, considering environmental considerations in addition to physical properties, a 2-octyl(meth)acrylate content of 50.1% by mass or more per 100% by mass of the monomer mixture is preferable. The higher the content of 2-octyl(meth)acrylate, which is a biomass monomer, the greater the contribution to petroleum resource conservation, so higher levels such as 55% by mass or more, 59% by mass or more, and 65% by mass or more are preferable. Furthermore, in relation to the content of monomer (a2), a 2-octyl(meth)acrylate content of less than 99.5% by mass per 100% by mass of the monomer mixture is preferable. Depending on the content of monomers (a3), (a4), and (a5) that can be optionally included in the monomer mixture, the upper limit of the 2-octyl(meth)acrylate content may be 94% by mass or less, or 89% by mass or less.

[0018] <Monomer (a2)> Monomer (a2) is a nitrogen-containing monomer selected from cyclic amide-containing monomers and monomers that contain both a nitrogen atom and a hydroxyl group in their molecule. Examples of monomers containing a cyclic amide (a2) include, but are not limited to, 4-acryloylmorpholine and 1-acryloylpiperidine-2-one. Furthermore, examples of monomers containing both a nitrogen atom and a hydroxyl group in the molecule include, but are not limited to, N-(2-hydroxymethyl)acrylamide and N-(2-hydroxyethyl)acrylamide. The monomer (a2) content is not particularly limited, but is preferably 0.5% by mass or more and less than 49.9% by mass per 100% by mass of the monomer mixture, 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 moisture and heat resistance, heat resistance, corrosion resistance, SUS adhesion strength, etc.

[0019] <Monomer (a3)> Monomer (a3) ​​is a monomer that contains a hydroxyl group (excluding monomer (a2)). Monomers that contain a hydroxyl group but also contain a nitrogen atom are classified as monomer (a2). Examples of monomers (a3) ​​include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and the like. Of these, 2-hydroxyethyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate are preferred from the viewpoint of adhesive strength and resistance to humid heat. The monomer (a3) ​​may or may not be included in the monomer mixture, but if included, 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, of 100% by mass of the monomer mixture. By setting the monomer (a3) ​​content to 5.1% by mass or more, the resistance to humid heat can be improved. Furthermore, it is preferable that the monomer (a3) ​​content be less than 40% by mass, and more preferably less than 29% by mass, of 100% by mass of the monomer mixture. By setting the monomer (a3) ​​content to less than 40% by mass, it is possible to have a moderate cohesive force while keeping the initial heat of the adhesive low.

[0020] <Monomer (a4)> Monomer (a4) is a monomer whose homopolymer glass transition temperature is -20.1°C or higher (excluding monomers (a2), (a3), and (a5)). The glass transition temperature (°C) of homopolymers is the value disclosed by the distributor of each monomer; if it is unknown, it can be found in the value listed in "Polymer Handbook 3rd Edition" (A WILEY-INTERSCIENCE PUBLICATION, 1989). As an example of monomer (a4), Examples 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 cohesiveness and adhesive strength, it is more preferable to use monomers with homopolymer glass transition temperatures of 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. Furthermore, for monomer (a4), it is more preferable to use a monomer selected from the group consisting of biomass monomers: hexyl methacrylate, lauryl acrylate, isobornyl (meth)acrylate, and stearyl (meth)acrylate, in consideration of the environment.

[0021] Monomer (a4) may or may not be included in the monomer mixture. If included, it is preferably 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, per 100% by mass of the monomer mixture. By setting the monomer (a4) content to 5.1% by mass or more, the cohesive force and adhesive force can be increased. Furthermore, it is preferable that the monomer (a4) content be less than 50% by mass, and more preferably less than 40% by mass, per 100% by mass of the monomer mixture. By setting the monomer (a4) content to less than 50% by mass, an appropriate cohesive force can be obtained, and sufficient initial tack for adhesion to the adherend can be obtained.

[0022] <Monomer (a5)> Monomer (a5) is a monomer that has a carboxyl group. The monomers containing a carboxyl group are not limited as long as they have a carboxyl group in their molecule. Specifically, examples include (meth)acrylic acid, p-carboxybenzyl acrylate, β-carboxyethyl acrylate, maleic acid, monoethyl maleic acid, 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] The monomer (a5) may or may not be included in the monomer mixture, but if it is included, the content is preferably less than 3% by mass, and more preferably less than 0.5% by mass, in order to prevent corrosion of the adherend by acid. The inclusion of monomer (a5) enhances the cohesive force of the adhesive layer, making it easier to improve adhesiveness and heat resistance. From the viewpoint of imparting cohesive force and heat resistance, 0.05% by mass or more is preferred, and 0.09% by mass or more is more preferred.

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

[0025] Other examples of 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. Phenoxyethyl acrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, n-octyl acrylate, and lauryl methacrylate are more preferred for their general applicability, and biomass monomers such as n-heptyl acrylate, n-butyl acrylate, n-octyl acrylate, and lauryl methacrylate are even more preferred.

[0026] Other monomers may or may not be included in the monomer mixture, but if included, it is preferable that they be less than 25% by mass of 100% by mass of the monomer mixture.

[0027] <Method for producing copolymer (A1)> Methods for producing copolymer (A1) include known polymerization methods such as solution polymerization, bulk polymerization, emulsion polymerization, and suspension polymerization.

[0028] The solvent used in solution polymerization is preferably acetone, methyl acetate, ethyl acetate, toluene, xylene, anisole, methyl ethyl ketone, or cyclohexanone. 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] For polymerization, radical polymerization initiators are preferred. Common radical polymerization initiators include peroxides and azo compounds. Peroxides include, for example, 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)hexine-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, n-butyl-4,4-bis(t-butylperoxy)barate; 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] Azo compounds include, for example, 2,2'-azobisisobutyronitriles such as 2,2'-azobis(2-methylbutyronitrile) and 2,2'-azobis(2-methylbutyronitrile); 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'-azobis(cyclohexane-1-carbonitride).

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

[0032] <Partial copolymer (A2)> Partial copolymer (A2) is obtained by partially polymerizing a monomer mixture containing the aforementioned monomers (a1) and (a2), and optionally including monomers (a3), (a4), and (a5), in the presence of a polymerization initiator by heating, irradiation, etc. 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 viewpoint of adhesive strength and heat resistance.

[0033] <Method for producing partial copolymer (A2)> The method for producing the partial copolymer (A2) preferably utilizes a curing reaction using heat or active energy rays (e.g., ultraviolet light) with a polymerization initiator such as a photopolymerization initiator.

[0034] Examples of photopolymerization initiators 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 initiators include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2-diphenylethane-1-one [BASF, trade name: Irgacure 651], anisole methyl ether, and the like. Examples of the acetophenone-based photopolymerization initiators include 1-hydroxycyclohexylphenyl ketone [BASF, trade name: Irgacure 184], 4-phenoxydichloroacetophenone, 4-t-butyl-dichloroacetophenone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propane-1-one [BASF, trade name: Irgacure 2959], 2-hydroxy-2-methyl-1-phenyl-propane-1-one [BASF, trade name: Darocure 1173], methoxyacetophenone, and the like. Examples of the α-ketol-based photopolymerization initiators include 2-methyl-2-hydroxypropiophenone and 1-[4-(2-hydroxyethyl)-phenyl]-2-hydroxy-2-methylpropan-1-one. Examples of aromatic sulfonyl chloride-based photopolymerization initiators include 2-naphthalene sulfonyl chloride. Examples of photoactive oxime-based photopolymerization initiators include 1-phenyl-1,1-propanedione-2-(o-ethoxycarbonyl)-oxime. Examples of benzoin-based photopolymerization initiators include benzoin. Examples of benzyl-based photopolymerization initiators include benzyl. Examples of benzophenone-based photopolymerization initiators include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, polyvinylbenzophenone, α-hydroxycyclohexylphenyl ketone. Examples of ketal-based photopolymerization initiators include benzyldimethyl ketal. The thioxanthone-based photopolymerization initiators include, for example, thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, dodecylthioxanthone, and the like. Examples of the acylphosphine-based photopolymerization initiators 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, and bis(2,6-dimethoxybenzoyl)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-methylpropan -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 Examples include )-2,4,4-trimethylpentylphosphine oxide, bis(2,4,6-trimethylbenzoyl)isobutylphosphine oxide, 2,6-dimethitoxybenzoyl-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 types. It is preferable to use 0.01 to 10 parts by mass, more preferably 0.03 to 5 parts by mass, per 100 parts by mass of the monomer mixture. 0.1 to 2 parts by mass is even more preferable.

[0036] When activating a photopolymerization initiator, it is important to irradiate the monomer composition containing the photopolymerization initiator with an active energy ray. Examples of such active energy rays include ionizing radiation such as alpha rays, beta rays, gamma rays, neutron rays, and electron beams, as well as ultraviolet rays, with ultraviolet rays being particularly preferred. Furthermore, there are no particular restrictions on the irradiation energy, irradiation time, or irradiation method of the active energy ray; it is sufficient as long as the photopolymerization initiator is activated and the reaction of the monomer components occurs.

[0037] <Polyfunctional compound (b)> Examples of polyfunctional compounds (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, and the like. Polyfunctional compounds (b) may be used alone or in combination of two or more. As the polyfunctional compound (b), polyfunctional (meth)acrylates are preferred, and due to their 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 polyfunctional compound (b) having two or more unsaturated double bond groups is preferably present in an amount of 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. The inclusion of the polyfunctional compound (b) in the adhesive containing the partial copolymer increases the cohesive force of the adhesive layer, making it easier to improve the adhesive strength and heat resistance.

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

[0040] <Hardening agent> The adhesive of the present invention may contain a curing agent. The curing agent is not particularly limited as long as it provides a cross-linked structure to the adhesive and can be used. The inclusion of a curing agent improves the cohesive strength of the adhesive layer, thereby improving its adhesiveness, heat resistance, and light resistance. The curing agent preferably contains at least one from the group consisting of isocyanate-based curing agents, epoxy-based curing agents, and aluminum chelating curing agents. Including at least one of isocyanate-based curing agents, epoxy-based curing agents, and aluminum chelating curing agents is preferable because it can moderately increase the cohesive force of the adhesive and does not adversely affect other physical properties. As long as at least one of isocyanate-based curing agents, epoxy-based curing agents, and aluminum chelating curing agents is included, other known curing agents besides isocyanate-based curing agents, epoxy-based curing agents, and aluminum chelating curing agents may be used in combination.

[0041] The isocyanate-based curing agent is an isocyanate having two or more isocyanate groups. Preferred isocyanates include aromatic polyisocyanates, aliphatic polyisocyanates, aromatic aliphatic polyisocyanates, alicyclic polyisocyanates, and their burettes, nurates, and adducts. From the viewpoint of resistance to yellowing, aliphatic polyisocyanates, alicyclic polyisocyanates, and their burettes, nurates, and adducts are even more preferred.

[0042] Examples of aromatic polyisocyanates include 1,3-phenylenediisocyanate, 4,4'-diphenyldiisocyanate, 1,4-phenylenediisocyanate, 4,4'-diphenylmethanediisocyanate, 2,4-tolylenediisocyanate, 2,6-tolylenediisocyanate, 4,4'-toluidinediisocyanate, 2,4,6-triisocyanatetoluene, 1,3,5-triisocyanatebenzene, dianisidinediisocyanate, 4,4'-diphenyletherdiisocyanate, and 4,4',4"-triphenylmethanetriisocyanate.

[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 aromatic aliphatic polyisocyanates include ω,ω'-diisocyanate-1,3-dimethylbenzene, ω,ω'-diisocyanate-1,4-dimethylbenzene, ω,ω'-diisocyanate-1,4-diethylbenzene, 1,4-tetramethylxylylenediisocyanate, and 1,3-tetramethylxylylenediisocyanate.

[0045] Alicyclic polyisocyanates include, for example, 3-isocyanate methyl-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(isocyanate methyl)cyclohexane.

[0046] The aforementioned biuret compound is a self-condensate having a biuret bond formed by the self-condensation of isocyanate monomers. An example of a biuret compound is a biuret compound of hexamethylene diisocyanate.

[0047] The aforementioned nurate is a trimer of an isocyanate monomer. Examples include a trimer of hexamethylene diisocyanate, a trimer of isophorone diisocyanate, and a trimer of tolylene diisocyanate.

[0048] The adduct is a bifunctional or greater isocyanate compound obtained by reacting an isocyanate monomer with a bifunctional or greater low molecular weight active hydrogen-containing compound. Examples of adducts include compounds obtained by reacting trimethylolpropane with hexamethylene diisocyanate, compounds obtained by reacting trimethylolpropane with tolylene diisocyanate, compounds obtained by reacting trimethylolpropane with xylylene diisocyanate, compounds obtained by reacting trimethylolpropane with isophorone diisocyanate, and compounds obtained by reacting 1,6-hexanediol with hexamethylene diisocyanate.

[0049] From the viewpoint of forming a sufficient crosslinking structure, trifunctional isocyanate compounds are preferred. More preferably, the isocyanate compounds are adducts and nurates, which are reaction products of an isocyanate monomer and a trifunctional low-molecular-weight active hydrogen-containing compound. The isocyanate compounds are preferably trimethylolpropane adducts of hexamethylene diisocyanate, nurates of hexamethylene diisocyanate, trimethylolpropane adducts of tolylene diisocyanate, nurates of tolylene diisocyanate, trimethylolpropane adducts of isophorone diisocyanate, and nurates of isophorone diisocyanate, and more preferably trimethylolpropane adducts of hexamethylene diisocyanate, trimethylolpropane adducts of tolylene diisocyanate, and trimethylolpropane adducts 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 chelating curing agent is not particularly limited as long as it is an aluminum compound that has a chelating ligand and functions to form a crosslinked structure with a crosslinkable resin. The chelating ligand may be a bidentate ligand or a polydentate ligand with three or more dentates, and examples include β-diketonates such as acetylacetonate, benzoylacetonate, and methylacetylacetonate; β-ketoester anions such as methylacetoacetate and ethylacetoacetate; and so on.

[0052] Specific examples of aluminum chelating curing agents include aluminum (ethyl acetate) diisopropylate, aluminum tris(acetylacetonate), aluminum tris(ethyl acetate), and aluminum bis(ethyl acetate) mono(acetylacetonate). These aluminum chelating hardeners can be used individually or in combination of two or more types.

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

[0054] <Silane coupling agent> The adhesive of the present invention may contain a silane coupling agent. The inclusion of a silane coupling agent can improve adhesive strength, heat resistance, resistance to humid heat whitening, and light resistance. It is preferable to include 0.05 to 0.2 parts by mass of the silane coupling agent per 100 parts by mass of resin (A). Using 0.05 to 0.2 parts by mass allows for improved humid heat resistance and heat resistance.

[0055] Examples of silane coupling agents include alkoxysilane compounds having a (meth)acryloxy group, alkoxysilane compounds having a vinyl group, alkoxysilane compounds having an amino group, alkoxysilane compounds having a mercapto group, or alkoxysilane compounds having an epoxy group. 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 BIC Chemie Japan Co., Ltd.).

[0056] <Adhesive-granting resin> The adhesive of the present invention may further contain a tackifying resin. All existing tackifying resins can be used, including 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 resin may be used alone or in a mixture of two or more.

[0057] As an aliphatic petroleum resin, Quinton B170 manufactured by Nippon Zeon Corporation; as an aromatic petroleum resin, Nisseki Neopolymer L-90 manufactured by JXTG; aliphatic / aromatic petroleum resin Examples include FTR6100 from Mitsui Chemicals, Inc., and rosin derivatives such as SylvatacRE85 from Arizona Chemicals, Inc. and Super Ester A-75 from 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 phenolic resins.

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

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

[0061] The tackifying resin content 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). The inclusion of the tackifying resin improves the adhesive strength to the adherend.

[0062] Furthermore, it is preferable to use a tackifying resin with a biomass content of 80% or more, taking environmental considerations into account. Furthermore, the softening point of the tackifying resin is preferably of a higher softening point grade in order to improve heat resistance, preferably 90°C or higher, more preferably 120°C or higher, and even more preferably 140°C or higher.

[0063] The adhesive of the present invention may also contain various resins, chlorinated polyolefins (described later), oils, softeners, dyes, pigments, antioxidants, and ultraviolet absorbers as optional components, provided that they solve the problem.

[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 viewpoint of good compatibility with acrylic polymers and other materials, and effective reduction of polarity, chlorinated polypropylene or chlorinated ethylene vinyl acetate copolymer are preferred. Examples of commercially available products include Superclon 390S (chlorinated polypropylene, chlorine content 36%) and Superclon BX (chlorinated EVA, chlorine content 18%) (both manufactured by Nippon Paper Industries Co., Ltd.).

[0065] The adhesive of the present invention preferably has a gel fraction of 40% or more. However, depending on the application, it may be used even if the gel fraction is 40% or less. The method for measuring the gel fraction is described in detail in the examples.

[0066] ≪Adhesive layer≫ The adhesive layer is a layer formed from the adhesive of the present invention. There are no particular restrictions on the method of forming the adhesive layer, and it is the same as the coating method described in the description of the adhesive sheet below.

[0067] Adhesive Sheet The adhesive sheet comprises an adhesive layer made of the adhesive of the present invention and a release film.

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

[0069] The adhesive sheet of the present invention preferably has a higher adhesive strength for SUS bonding, which is desirable for product fixation and other purposes. While it may be possible to use a lower adhesive strength depending on the product, for multi-purpose use, a peel strength of 8 N / 25 mm or higher is preferable. The measurement method will be 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 transparent plastic substrate materials include polyesters such as polyethylene terephthalate (PET), acrylic resins such as polymethyl methacrylate (PMMA), polycarbonate, triacetylcellulose, polysulfone, polyarylate, polycycloolefin, and other plastic materials. The plastic materials can be used individually or in combination of two or more types.

[0071] As the release film, among the transparent plastic substrates mentioned above, a transparent plastic substrate with excellent heat resistance, that is, a transparent plastic substrate in which deformation is suppressed or prevented under harsh conditions such as high temperature and high temperature and humidity, can be suitably used. PET film or sheet is 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 materials used, but a thickness of less than 200 μm prevents the material from being too stiff, making it easy to roll up and allowing for comfortable use when laminating with sheets or other materials.

[0073] The adhesive sheet of the present invention has excellent adhesive properties and is therefore suitable as an adhesive for forming optical display components such as LCDs and OLEDs, input devices such as touch panels, and for bonding these components together. The optical components are not particularly limited and include PET films, polarizing plates, phase difference plates, elliptical polarizing plates, optical compensation films, brightness enhancement films, infrared / electromagnetic wave cut films, front anti-reflective films, surface protection films, films having an ITO (indium tin oxide) layer, films having 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 even laminates thereof.

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

[0075] The viscosity of the adhesive can also be adjusted by adding a suitable liquid medium during coating. Specifically, 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; or other hydrocarbon solvents. However, water and alcohol should be used with caution as they may inhibit the reaction between resin (A) and isocyanate-based curing agents.

[0076] There are no particular restrictions on the coating method, and various methods can be used, such as Meyer bar, applicator, brush, spray, roller, gravure coater, die coater, lip coater, comma coater, knife coater, reverse coater, and spin coater. There are also no particular restrictions on the drying and curing method, and methods such as hot air drying, infrared, reduced pressure drying, and active energy ray drying can be used, but from the viewpoint of outgassing resistance, hot air or steam heating at 60 to 180°C is preferred.

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

[0078] ≪Laminated structure≫ The laminate of the present invention comprises a substrate and an adhesive layer. The adhesive layer is formed using the adhesive sheet of the present invention. Specifically, for example, the laminate can be formed by peeling off the release film from the adhesive sheet of the present invention and attaching the adhesive layer to the substrate.

[0079] <Base material> The substrate refers to the object to which the adhesive layer of an adhesive sheet having an adhesive layer is attached, and is not limited to any specific object. 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 and stainless steel (SUS), aluminum and copper, and other materials such as cement, mortar, glass, nonwoven fabrics, woven fabrics, paper, rubber, foam sheets, and laminates thereof. The adhesive of the present invention exhibits excellent adhesive strength to at least one type of substrate. The thickness of the substrate is not particularly limited, but is preferably less than 500 μm, more preferably 10 to 200 μm, and more preferably 25 to 150 μm.

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

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

[0082] <Manufacturing of laminates> One method for manufacturing a laminate is to peel off the release film from one side of an adhesive sheet having release films on both sides of the adhesive layer, and then attach the adhesive layer to a substrate to form a laminate. Alternatively, an adhesive layer can be formed directly on the substrate, and then the adhesive layer of the substrate or another adhesive sheet can be attached to the adhesive layer to form a laminate.

[0083] ≪Display≫ The display comprises the laminate, polarizer, and optical element of the present invention. As a result, the display of the present invention has excellent visibility. The optical element is not particularly limited and examples include liquid crystal elements and organic EL elements.

[0084] Figure 2 shows an example of a schematic cross-sectional view partially illustrating a display, which is an example of the use of the adhesive sheet of the present invention. In Figure 2, 3 is a light-transmitting substrate (cover panel), 1 is adhesive layer 1, 4 is a polarizing plate, 5 is 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 display configuration is not limited to that shown in Figure 2.

[0085] In the display shown in Figure 2, a light-transmitting substrate (cover panel) is attached to a polarizing plate via the adhesive layer of the present invention (adhesive layer 1), and further attached to an organic EL cell via an adhesive layer for the polarizing plate (adhesive layer 2). Thus, 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 via an adhesive layer for the polarizing plate. For example, in Figure 2, the adhesive layer of the present invention can be used in either adhesive layer 1 or adhesive layer 2. Generally, when comparing adhesive layer 1 and adhesive layer 2, the required quality for adhesive layer 1 is higher, and since the adhesive of the present invention has good adhesion and bonding properties to the substrate, it is preferable to use it for adhesive layer 1. In this case, the adhesive used to form adhesive layer 2 may be the adhesive of the present invention or a conventionally known adhesive.

[0086] There are no particular restrictions on the uses of the display, but examples include OLED TVs, 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 bio-derived materials by using biomass monomers as monomers constituting the resin (A) or by using a biomass tackifier. A biomass content of 30% or more is preferable. More preferably 39% or more, and even more preferably 60% or more; the higher the biomass content, the greater the usefulness as an environmentally friendly material. The method for calculating the biomass content is described in the examples. [Examples]

[0088] The present invention will be described 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" refers to "parts by mass" and "%" refers to "mass percent". Also, the blending amounts in the table are in parts by mass, and except for the solvent, the values ​​are calculated on a non-volatile content basis. A blank space in the table indicates that the ingredient was not blended.

[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 Shimadzu Corporation LC-GPC system "Prominence". Two TSKgel α-M columns from Tosoh Corporation were connected in series. N,N-dimethylformamide (DMF) was used as the eluent, and the measurement was performed at 40°C. Mw was determined by conversion using polystyrene, whose Mw is known, as the standard substance.

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

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

[0092] (Production of partial copolymers of monomer mixtures) <Example 18: Manufacturing of (A2-1)> A monomer mixture consisting of 95 parts of 2-octyl acrylate (2-OA), 2 parts of N-(2-hydroxymethyl)acrylamide, and 3 parts of 4-hydroxybutyl acrylate (4HBA) was mixed with 0.04 parts of 1-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator. The mixture was 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, thereby obtaining a partial copolymer in which some of the monomer components had polymerized. The obtained partial copolymer of the monomer mixture was designated A2-1.

[0093] <Examples 19-25, Comparative Manufacturing Examples 4-5: Manufacturing of (A2-2-A2-8, A'-4-A'-5)> The monomer mixture copolymers (A2-2 to A2-8, A'-4 to A'-5) were produced in the same manner as the monomer mixture partial copolymer (Example 18), except that the composition and blending amounts (parts by mass) were changed as 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 information for which it has been confirmed is included. [Monomer (a1): 2-Octyl (meth)acrylate] 2-OA:2-Octylacrylate (manufactured by Nippon Shokubai Co., Ltd., biomass content 73%) 2-OMA:2-Octyl methacrylate (manufactured by Sanwa Chemifah Co., Ltd., biomass content 67%) [Monomer (a2): Nitrogen-containing monomers selected from cyclic amide-containing monomers and monomers containing both nitrogen atoms and hydroxyl groups in the molecule] N-(2-hydroxyethyl)acrylamide N-(2-hydroxymethyl)acrylamide 4-Acryloylmorpholine 1-Acryloylpiperidine-2-one [Monomer (a3): Hydroxyl group-containing monomer] HEA: Hydroxyethyl acrylate 4HBA: 4-Hydroxyn-butyl acrylate [Monomer (a4): Monomers whose homopolymer glass transition temperature is -20.1°C or higher] MA: Methyl acrylate (Tg: 6℃) iBMA: Isobutyl methacrylate (Tg: 48℃) IBXA: Isobornyl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., biomass content 76%, Tg: 94℃) VAc: Vinyl acetate (Tg: 28℃) THFA: Tetrahydrofurfuryl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., biomass content 62%, Tg: -12℃) LA: Lauryl acrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., biomass content 80%, Tg: -3℃) [Monomer (a5): Carboxylate-containing monomer] AA: Acrylic acid [Other monomers] BA: n-butyl acrylate (manufactured by Sanwa Chemifah Co., Ltd., biomass content 57%, Tg: -48℃) HA: n-heptyl acrylate (manufactured by Sanwa Chemifa Co., Ltd., biomass content 70%, Tg: -57℃)

[0098] <Example 26> To 100 parts of a monomer mixture copolymer (A1-1), 0.2 parts of "D-165N" (manufactured by Mitsui Chemicals, a burette of hexamethylene diisocyanate) was added as a curing agent to obtain a mixture. This mixture was coated onto a 38 μm thick release liner (SP-PET-O1-BU: manufactured by Mitsui Chemicals Tohcello Co., Ltd.) using a comma coater to obtain a release sheet with a thickness of 25 μm after drying. 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, and the mixture was aged at 23°C for 7 days to obtain an adhesive sheet.

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

[0100] <Example 45> As shown in Table 4, an adhesive sheet was obtained in the same manner as in Example 26, except that a copolymer of monomer mixtures (A1-11) was used as the 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) was added as a polyfunctional compound and 1.5 parts of 1-hydroxycyclohexyl phenyl ketone was added as a photopolymerization initiator to obtain a mixture. This mixture was coated onto a 38 μm thick release liner (SP-PET-O1-BU: manufactured by Mitsui Chemicals Tohcello Co., Ltd.) using a comma coater to a thickness of 25 μm, and another 75 μm thick release liner (SP-PET-O3-B3: manufactured by Mitsui Chemicals Tohcello Co., Ltd.) was laminated onto the coated surface. Then, the coated layer was exposed to an integrated light intensity of 1200 mJ / cm². 2 The coating layer was cured by irradiating it with ultraviolet light to obtain an adhesive layer.

[0102] <Examples 47-54, Comparative Examples 4-5> 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 the polyfunctional compound, and the amount of the 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) was added as a polyfunctional compound and 0.05 parts of "D-165N" (manufactured by Mitsui Chemicals, a burette of hexamethylene diisocyanate) was added as a curing agent to 100 parts of a partial copolymer of monomer mixture (A2-7).

[0104] <Gel fraction measurement> The 38 μm release liner was peeled off the obtained adhesive sheet, and the adhesive layer was bonded to a PET film substrate (Toyobo Co., Ltd., Cosmo Shine A-4360, 100 μm thick). A test adhesive sheet was then cut to a size of 30 mm wide x 100 mm long. The release liner was then peeled off the other side of the adhesive tape to create a test specimen, and its 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 is 40% or more, and "40%>" means that the gel fraction is less than 40%. Gel fraction (weight %) = 100 × (W2 - W0) / (W1 - W0) ... (1) (W0: Weight of the substrate (PET film), W1: Weight of the test specimen before immersion, W2: Weight of the test specimen after immersion and drying)

[0105] <Calculation of Biomass Content> The biomass content of the adhesive was calculated using the following formula (2). (For a system with two monomer components (A, B) and one tackifier component (C)) Biomass content = {(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 content of monomer A (%), Bb: Biomass content of monomer B (%) Cb: Biomass content of monomer C (%) If the biomass content was specified as a range, the minimum value was used in the above calculation.

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

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

[0108] The moisture and heat resistance, heat resistance, and corrosion resistance of the adhesive layers obtained in Examples 26 to 55 and Comparative Examples 1 to 5 were evaluated using the methods described below. In addition, the SUS adhesion strength of the adhesive layer was measured as a basic physical property of the adhesive. The results are shown in Table 5.

[0109] <Heat and moisture resistance> The 38 μm release liner was peeled off the obtained adhesive sheet, and the adhesive layer was laminated 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 the adhesive sheet, and it was laminated to a glass plate using a laminator in the same manner as above. A test specimen was prepared by applying a pressure of 0.5 MPa in an atmosphere of 50°C and holding it for 20 minutes, resulting in a layered structure of glass plate / adhesive layer / glass plate. This specimen was left for 200 hours in an environment of 60°C and 90% relative humidity (also referred to as 60°C-90%RH). Each specimen was cooled for 1 hour at 23°C-50%RH to obtain test specimens. Each test specimen was visually inspected and evaluated according to the following criteria. [Evaluation Criteria] A: More than 80% of the test specimen area is transparent: Excellent B: 60% to less than 80% of the specimen area is transparent: Good C: 40% to less than 60% of the test specimen area is transparent: Usable D: Less than 40% of the specimen 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 and 50% RH, and the test piece was pressure-bonded onto SUS by reciprocating a 2 kg hand roller once such that the bonding area was 25 mm in width × 40 mm in length. After standing for 24 hours in an atmosphere of 23°C and 50% RH, a load of 500 g was applied and the test piece was stood for 10 hours in an 80°C environment. The displacement of the test piece after 10 hours was measured using a microscope, and evaluation was performed based on the following criteria. A: Displacement of the test piece is less than 0.1 mm: Excellent B: Displacement of the test piece is 0.1 mm or more and less than 0.4 mm: Good C: Displacement of the test piece is 0.4 mm or more and less than 10 mm: Usable D: Displacement of the test piece is 10 mm or more: Unusable

[0111] <Corrosion Resistance> After bonding the adhesive sheet onto an aluminum foil, the sheet was left to stand for 48 hours under a high-temperature and high-humidity condition of 60°C × 90% RH. Thereafter, the adhesive sheet was peeled off from the aluminum foil, the surface of the aluminum foil was visually checked, and evaluation was performed according to the following criteria. A: No discoloration was confirmed on the aluminum foil surface: Good B: Partial discoloration was confirmed on the aluminum foil surface: Usable C: Overall discoloration was confirmed on the aluminum foil surface: Unusable

[0112] <Adhesion Strength to SUS> The 38 μm release liner of the obtained adhesive sheet was peeled off, the pressure-sensitive adhesive layer was bonded to a PET film as a substrate (manufactured by Toyobo Co., Ltd., Cosmoshine A-4360, thickness 100 μm), and cut into a size of 25 mm in width × 100 mm in length to prepare an adhesive sheet for testing. The other 75 μm release liner of this adhesive sheet for testing was peeled off, the pressure-sensitive adhesive layer was bonded to a glass plate in an atmosphere of 23°C and 50% relative humidity (50% RH), and further pressure-bonded with a roll in accordance with JIS Z-0237. After 24 hours had elapsed from pressure bonding, the peel strength (peel angle 180°, peel speed 300 mm / min; unit: N / 25 mm width) was measured using a tensile tester (Tensilon: manufactured by Orientec Co., Ltd.). [Evaluation Criteria] A: Peel strength of 15N / 25mm or higher: Good B: Peel strength of 8N / 25mm or more, and less than 15N / 25mm: Usable C: Peel strength less than 8N / 25mm: Not usable

[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 OLED cells

Claims

1. The monomer mixture comprises a copolymer (A1) obtained by complete polymerization or a partially polymerized copolymer (A2) obtained by partial polymerization of the monomer mixture. An adhesive comprising a monomer mixture containing the following monomers (a1) and (a2), and optionally containing the following monomers (a3), (a4), and (a5). (a1) 2-octyl (meth)acrylate (a2) Nitrogen-containing monomer selected from cyclic amide-containing monomers and monomers containing both a nitrogen atom and a hydroxyl group in the molecule (a3) Hydroxyl 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) Carboxylate group-containing monomers

2. In a monomer mixture of 100% by mass, The monomer (a1) is present in an amount of 50.1% by mass or more and less than 99.5% by mass, The adhesive according to claim 1, comprising monomer (a2) in an amount of 0.5% by mass or more and less than 49.9% by mass.

3. In a monomer mixture of 100% by mass, The adhesive according to claim 1, comprising 5.1% by mass or more of monomer (a3).

4. In a monomer mixture of 100% by mass, The adhesive according to claim 1, comprising 5.1% by mass or more of monomer (a4).

5. The adhesive according to claim 1, wherein the monomer (a4) comprises a monomer whose homopolymer glass transition temperature is 0°C or higher.

6. The adhesive according to claim 1, comprising a partially copolymer of a monomer mixture (A2), and further comprising a polyfunctional compound (b) having two or more unsaturated double bond groups.

7. The adhesive according to claim 6, comprising 0.01 to 10 parts by mass of a polyfunctional compound (b) per 100 parts by mass of a partially copolymer (A2).

8. The adhesive according to claim 1, wherein the gel fraction is 40% by mass or more.

9. The adhesive according to claim 1, characterized in that it does not contain a solvent.

10. An adhesive layer formed from the adhesive described in any one of claims 1 to 9.

11. An adhesive sheet comprising the adhesive layer and release film according to claim 10.

12. A laminate comprising the adhesive layer and substrate according to claim 10.

13. A display comprising the laminate, polarizer, and optical element described in claim 12.

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