Resin composition for adhesives

Abstract

To provide a resin composition for adhesives that can form an adhesive layer excelling in: unevenness followability during bonding; shape retentivity before bonding; and softness during low-temperature use.SOLUTION: A resin composition for adhesives contains a methacrylic copolymer having a macromonomer (A)-derived constitutional unit and a vinyl monomer (B)-derived constitutional unit. The macromonomer (A) has an alkyl methacrylate (a)-derived constitutional unit having a C8-30 alkyl group.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition for a pressure-sensitive adhesive. [Background technology]

[0002] Known adhesives capable of forming adhesive layers with excellent holding power include those containing a (meth)acrylic copolymer with a weight-average molecular weight of 50,000 to 1,000,000, obtained by polymerizing a monomer mixture containing a macromonomer with a number-average molecular weight of 500 or more but less than 6,000 and a vinyl monomer (Patent Document 1).The macromonomer used has a structural unit derived from methyl methacrylate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2015 / 080244 Summary of the Invention [Problem to be solved by the invention]

[0004] When bonding components together via an adhesive layer, for example, an adhesive layer sandwiched between a pair of separate films is prepared, one separate film is peeled off to laminate one component, the other separate film is peeled off to laminate the other component, and the resulting laminate is heated and pressurized. The heating temperature at this time varies depending on the process, but is, for example, about 70°C. When at least one surface of the members to be bonded via the adhesive layer is uneven, the adhesive layer is required to deform to follow the unevenness during bonding. Furthermore, when the adhesive layer is used in a foldable display, it may be bent at low temperatures (e.g., -20°C), and therefore it is required to be flexible when used at low temperatures. However, the pressure-sensitive adhesive containing the (meth)acrylic copolymer described in Patent Document 1 sometimes does not have sufficient conformability to uneven surfaces or softness when used at low temperatures.

[0005] The inventors have found that increasing the molecular weight of the (meth)acrylic copolymer increases the shape retention at room temperature and prevents the adhesive layer from protruding from between the separate films during storage before lamination, but increases in viscosity cause a problem of reduced conformability to irregularities during lamination. Furthermore, in the case of a random copolymer, increasing the molecular weight enough to provide shape retention results in excessively high solution and melt viscosities, making it difficult to transfer the solution on a production line and to form a coating film with a uniform thickness.

[0006] An object of the present invention is to provide a resin composition for adhesives that can form an adhesive layer that is excellent in conformability to irregularities when attached, shape retention when not attached, and softness when used at low temperatures. [Means for solving the problem]

[0007] The present invention has the following aspects. [1] A (meth)acrylic copolymer having a structural unit derived from a macromonomer (A) and a structural unit derived from a vinyl monomer (B), A resin composition for pressure-sensitive adhesives, wherein the macromonomer (A) has a structural unit derived from an alkyl (meth)acrylate (a) having an alkyl group having 8 to 30 carbon atoms. [2] The resin composition for pressure-sensitive adhesives according to [1], wherein the proportion of structural units derived from the alkyl (meth)acrylate (a) relative to 100% by mass of all structural units constituting the macromonomer (A) is 70% by mass or more. [3] The resin composition for pressure-sensitive adhesives according to [1] or [2], wherein the structural unit derived from the alkyl(meth)acrylate (a) comprises a structural unit derived from an alkyl(meth)acrylate (a1) having an alkyl group having 12 to 30 carbon atoms. [4] The resin composition for pressure-sensitive adhesives according to [3], wherein the proportion of structural units derived from the alkyl (meth)acrylate (a1) relative to 100% by mass of all structural units constituting the macromonomer (A) is 40% by mass or more. [5] The resin composition for pressure-sensitive adhesives according to any one of [1] to [4], wherein the structural unit derived from the vinyl monomer (B) contains a structural unit derived from an acrylic (meth)alkylate (b) having an alkyl group having 1 to 4 carbon atoms. [6] The resin composition for pressure-sensitive adhesives according to [5], wherein the proportion of structural units derived from the acrylic (meth)alkylate (b) relative to 100% by mass of all structural units derived from the vinyl monomer (B) is 50% by mass or more. [7] The resin composition for pressure-sensitive adhesives according to any one of [1] to [6] above, wherein the macromonomer (A) has a number average molecular weight of 1,000 to 30,000. [8] The resin composition for pressure-sensitive adhesives according to any one of [1] to [7] above, wherein the (meth)acrylic copolymer has a weight average molecular weight of 50,000 to 2,000,000. [9] The resin composition for pressure-sensitive adhesives according to any one of [1] to [8], wherein the (meth)acrylic copolymer has a deformation of 15% or less in a creep test at 23°C, 100 Pa, and 10 minutes, a deformation of 100% or more in a creep test at 70°C, 1000 Pa, and 1 minute, and a storage modulus G' at -20°C and 1 Hz of 700 kPa or less.

[10] The pressure-sensitive adhesive resin composition according to any one of [1] to [9] above, which is used for bonding a member having an uneven surface to a member having an organic light-emitting diode. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a resin composition for adhesives that can form an adhesive layer that is excellent in conformability to irregularities when attached, shape retention when not attached, and softness when used at low temperatures. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following definitions of terms apply throughout the specification and claims. "(Meth)acrylate" is a general term for acrylate and methacrylate. The same applies to "(meth)acryloyl group," "(meth)acrylic acid," "(meth)acrylonitrile," and "(meth)acrylamide." The term "(meth)acrylic copolymer" refers to a copolymer having structural units derived from (meth)acrylic monomers. The (meth)acrylic copolymer may further have structural units derived from a monomer other than the (meth)acrylic monomer (e.g., styrene). "(Meth)acrylic monomer" means a monomer having a (meth)acryloyl group. "Vinyl monomer" means a compound having an ethylenically unsaturated bond (polymerizable carbon-carbon double bond). The symbol "to" indicating a range of values ​​means that the values ​​before and after it are included as the lower and upper limits.

[0010] [Resin composition for pressure-sensitive adhesive] The resin composition for pressure-sensitive adhesives according to one embodiment of the present invention (hereinafter also referred to as "the resin composition") contains a (meth)acrylic copolymer (hereinafter also referred to as "copolymer (I)"). The copolymer (I) contained in the resin composition may be one type or two or more types. The present resin composition may further contain other components in addition to the copolymer (I), if necessary.

[0011] (Copolymer(I)) The copolymer (I) has a structural unit derived from the macromonomer (A) and a structural unit derived from the vinyl monomer (B).

[0012] <Macromonomer (A)> The macromonomer (A) has a structural unit derived from an alkyl (meth)acrylate (a) having an alkyl group having 8 to 30 carbon atoms. When the alkyl group has 8 to 30 carbon atoms, the resulting adhesive layer has excellent conformability to irregularities during application (for example, at high temperatures of about 70°C), shape retention during storage, and softness when used at low temperatures (for example, -20°C). The alkyl group may be linear or branched, but branched alkyl groups are more preferred. Specific examples of the alkyl (meth)acrylate (a) include octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, hexadecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, icosyl (meth)acrylate, behenyl (meth)acrylate, etc. The alkyl (meth)acrylate (a) may be used alone or in combination of two or more.

[0013] As the alkyl(meth)acrylate (a), from the viewpoint of softness at low temperatures, an alkyl(meth)acrylate (a1) having an alkyl group with 12 to 30 carbon atoms is preferred. The alkyl group in the alkyl(meth)acrylate (a1) preferably has 12 to 18 carbon atoms. The alkyl(meth)acrylate (a1) may be a mixture of a first alkyl(meth)acrylate having an alkyl group with 12 to 30 carbon atoms and a second alkyl(meth)acrylate having an alkyl group with 12 to 30 carbon atoms and a different number of carbon atoms from that of the first alkyl(meth)acrylate. The alkyl(meth)acrylate (a1) may be used in combination with an alkyl(meth)acrylate having an alkyl group having 8 to 11 carbon atoms.

[0014] The alkyl(meth)acrylate (a) is preferably a methacrylate from the viewpoint of polymerizability.

[0015] The macromonomer (A) may further have other structural units in addition to the structural units derived from the alkyl (meth)acrylate (a). Various monomers can be used to form other structural units, and examples thereof include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, isoamyl (meth)acrylate, hexyl (meth)acrylate, 4-t-butylcyclohexyl (meth)acrylate, phenyl (meth)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate, and tetramethyl (meth)acrylate. Trihydrofurfuryl, isobornyl (meth)acrylate, 3,5,5-trimethylcyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, terpene acrylate and its derivatives, hydrogenated rosin acrylate and its derivatives, docosyl (meth)acrylate, glycidyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, (meth)acrylate ) Hydroxyl group-containing (meth)acrylic acid esters such as 2-hydroxybutyl acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and glycerol (meth)acrylate; (meth)acrylic acid, 2-(meth)acryloyloxyethyl hexahydrophthalic acid, 2-(meth)acryloyloxypropyl hexahydrophthalic acid, 2-(meth)acryloyloxyethyl phthalic acid, 2-(meth)acryloyloxypropyl phthalic acid, 2-(meth)acryloyloxyethyl maleic acid, and 2-(meth)acryloyl carboxyl group-containing vinyl monomers such as 2-(meth)acryloyloxypropyl maleate, 2-(meth)acryloyloxyethyl succinate, 2-(meth)acryloyloxypropyl succinate, crotonic acid, fumaric acid, maleic acid, itaconic acid, monomethyl maleate, and monomethyl itaconate; acid anhydride group-containing vinyl monomers such as maleic anhydride and itaconic anhydride; epoxy group-containing vinyl monomers such as glycidyl (meth)acrylate, α-ethyl glycidyl acrylate, and 3,4-epoxybutyl (meth)acrylate; dimethylaminoethyl (meth)acrylate,Vinyl monomers containing an amino group such as diethylaminoethyl (meth)acrylate (meth)acrylic ester; vinyl monomers containing an amide group such as (meth)acrylamide, Nt-butyl (meth)acrylamide, N-methylol (meth)acrylamide, N-isopropylacrylamide, hydroxyethyl acrylamide, N-methoxymethyl (meth)acrylamide, N-butoxymethyl (meth)acrylamide, diacetone acrylamide, maleic acid amide, and maleimide; styrene, α-methylstyrene, vinyltoluene, (meth)acrylamide, Vinyl monomers such as lylonitrile, vinyl chloride, vinyl acetate, and vinyl propionate, divinylbenzene, ethylene glycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, triethylene glycol di(meth)acrylate, tetraethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, allyl (meth)acrylate, and N,N'-methylenebis(meth)acrylamide. Multifunctional vinyl monomers, acryloylmorpholine, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxyethyl (meth)acrylate, ethoxyethyl (meth)acrylate, n-butoxyethyl (meth)acrylate, isobutoxyethyl (meth)acrylate, t-butoxyethyl (meth)acrylate, ethoxyethoxyethyl (meth)acrylate, phenoxyethyl (meth)acrylate, nonylphenoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, acetoacetate (meth)acrylate hydroxyethyl, "Placcel FM" (a caprolactone addition monomer manufactured by Daicel Chemical Industries, Ltd., trade name), "Blenmer PME-100" (a methoxypolyethylene glycol methacrylate (having two ethylene glycol chains) manufactured by NOF Corporation, trade name), "Blenmer PME-200" (a methoxypolyethylene glycol methacrylate (having four ethylene glycol chains) manufactured by NOF Corporation, trade name), "Blenmer PME-400" (a methoxypolyethylene glycol methacrylate (having nine ethylene glycol chains) manufactured by NOF Corporation),"Blemmer 50POEP-800B" (Octoxy polyethylene glycol-polypropylene glycol-methacrylate (8 ethylene glycol chains and 6 propylene glycol chains) manufactured by NOF Corporation, trade name), "Blemmer 20ANEP-600" (Nonylphenoxy (ethylene glycol-polypropylene glycol) monoacrylate manufactured by NOF Corporation, trade name), "Blemmer AME-100" (NOF Corporation, trade name), "Blemmer AME-200" (NOF Corporation, trade name), and " Blenmar 50AOEP-800B (manufactured by NOF Corporation, trade name), Viscoat #150 (manufactured by Osaka Organic Chemical Industry, trade name), Viscoat #190 (manufactured by Osaka Organic Chemical Industry, trade name), Viscoat #230 (manufactured by Osaka Organic Chemical Industry, trade name), 2-methacryloyloxyethyl acid phosphate, Silaplane FM-0711 (manufactured by JNC Corporation, trade name), Silaplane FM-0721 (manufactured by JNC Corporation, trade name), Silaplane FM-0725 (manufactured by JNC Corporation, trade name), Silaplane TM-0701 (manufactured by JNC Corporation, trade name) ), Silaplane TM-0701T (manufactured by JNC Corporation, trade name), X-22-174DX (manufactured by Shin-Etsu Chemical Co., Ltd., trade name), X-22-2426 (manufactured by Shin-Etsu Chemical Co., Ltd., trade name), X-22-2475 (manufactured by Shin-Etsu Chemical Co., Ltd., trade name), silicone monomers such as 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-acryloxypropyl Monomers containing silane coupling agents such as vinyltrimethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane, 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3,3-pentafluorophenyl (meth)acrylate, 2-(perfluorobutyl)ethyl (meth)acrylate, 3-(perfluorobutyl)-2-hydroxypropyl (meth)acrylate, 2-(perfluorohexyl)ethyl (meth)acrylate, and 3-perfluorohexyl-2-hydroxypropyl (meth)acrylate.3-(perfluoro-3-methylbutyl)-2-hydroxypropyl (meth)acrylate, 2,2,3,3-tetrafluoropropyl (meth)acrylate, 1H,1H,5H-octafluoropentyl (meth)acrylate, 1H,1H,5H-octafluoropentyl (meth)acrylate, 1H,1H,2H,2H-tridecafluorooctyl (meth)acrylate, 1H-1-(trifluoromethyl)trifluoroethyl (meth)acrylate, 1H,1H,3H-hexafluorobutyl (meth)acrylate fluorine-containing monomers such as acrylate, 1,2,2,2-tetrafluoro-1-(trifluoromethyl)ethyl (meth)acrylate, monomers having an acetal structure such as 1-butoxyethyl (meth)acrylate, 1-(2-ethylhexyloxy)ethyl (meth)acrylate, 1-(cyclohexyloxy)ethyl (meth)acrylate, and 2-tetrahydropyranyl (meth)acrylate, 4-(meth)acryloyloxybenzophenone, and 2-isocyanatoethyl (meth)acrylate.

[0016] The macromonomer (A) typically has two or more structural units represented by the following formula (a') (hereinafter also referred to as "structural units (a')"), and at least a portion of the two or more structural units (a') are structural units derived from alkyl (meth)acrylate (a). The P's present in the two or more structural units (a') may be the same or different, and the Q's present in the two or more structural units (a') may be the same or different. The macromonomer (A) may further include a structural unit other than the structural unit (a').

[0017] [ka]

[0018] In formula (a'), P represents a hydrogen atom, a methyl group, or CH2OH, Q is selected from the group consisting of OR, OC1CR, halogen, CO2H, COR, CO2R, CN, CONH2, CONHR, CONR2, COOCH(CH3)OR, and R', and R is selected from the group consisting of a hydrogen atom, a substituted and unsubstituted alkyl group, a substituted and unsubstituted cycloalkyl group, a substituted and unsubstituted aryl group, a substituted and unsubstituted heterocyclic group, a substituted and unsubstituted aralkyl group, a substituted and unsubstituted alkaryl group, and a substituted and unsubstituted organosilyl group, and the substituents may be the same or different and may be a carboxylic acid group, a carboxylic acid ester group, an epoxy group, a hydroxy group, an alkoxy group, R' is selected from the aromatic group consisting of substituted and unsubstituted aryl groups and substituted and unsubstituted heteroaryl groups, and the substituents may be the same or different and are selected from the group consisting of carboxylic acid groups, carboxylic acid ester groups, epoxy groups, hydroxy groups, alkoxy groups, primary amino groups, secondary amino groups, tertiary amino groups, isocyanato groups, sulfonic acid groups, substituted and unsubstituted alkyl groups, substituted and unsubstituted aryl groups, substituted and unsubstituted olefinic groups, and halogen atoms.

[0019] The structural unit derived from alkyl(meth)acrylate (a) is a structural unit in which P in formula (a') is a hydrogen atom or a methyl group, Q is CO2R, and R is an alkyl group having 8 to 30 carbon atoms. Examples of the monomer that forms the structural unit (a') other than the alkyl (meth)acrylate (a) and the monomer that forms the other structural unit include the same monomers as described above.

[0020] The proportion of the structural units derived from alkyl (meth)acrylate (a) relative to 100% by mass of all structural units constituting the macromonomer (A) is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and may be 100% by mass.

[0021] The proportion of the structural units derived from alkyl (meth)acrylate (a1) relative to 100% by mass of all structural units constituting the macromonomer (A) is preferably 40% by mass or more, more preferably 60% by mass or more, even more preferably 80% by mass or more, and may be 100% by mass.

[0022] The macromonomer (A) preferably has a methacrylate-derived structural unit as a structural unit constituting the macromonomer (A). The proportion of methacrylate-derived structural units relative to 100% by mass of all structural units constituting the macromonomer (A) is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, and even more preferably 90 to 100% by mass. If the proportion of methacrylate-derived structural units is 50% by mass or more, the molecular weight of the macromonomer (A) can be reduced.

[0023] From the viewpoint of productivity, the proportion of the structural units derived from the carboxyl group-containing monomer relative to 100% by mass of all structural units constituting the macromonomer (A) is preferably 0 to 10% by mass.

[0024] The macromonomer (A) typically has a radical polymerizable group or an addition-reactive functional group such as a hydroxy group, an isocyanate group, an epoxy group, a carboxy group, an amino group, an amide group, or a thiol group. The macromonomer (A) may have either a radical polymerizable group or a functional group, or may have both. When the macromonomer (A) has both a radical polymerizable group and a functional group, the number of radical polymerizable groups and the number of functional groups may be two or more. Among the above, those having a radical polymerizable group are preferred, in particular because they are copolymerizable with the vinyl monomer (B). The macromonomer (A) may have two or more radical polymerizable groups, but preferably has one. When the macromonomer (A) has a functional group, the functional group may also be two or more, but preferably has one.

[0025] The macromonomer (A) preferably has a radical polymerizable group at the end of a main chain containing two or more structural units (a'), and more preferably has a terminal structure of the following formula (1): In formula (1), "..." indicates a main chain portion containing two or more structural units (a').

[0026] [ka]

[0027] In formula (1), R may have the same meaning as R above.

[0028] R may be, for example, a branched or linear alkyl group having 1 to 20 carbon atoms. Specific examples thereof include methyl, ethyl, n-propyl, i-propyl, n-butyl, t-butyl, i-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, and icosyl. Among these, in terms of ease of availability, methyl, ethyl, n-propyl, i-propyl, n-butyl, t-butyl, pentyl, hexyl, heptyl, and octyl are preferred, and methyl, ethyl, n-propyl, i-propyl, n-butyl, and t-butyl are more preferred.

[0029] R may be, for example, a cycloalkyl group having 3 to 20 carbon atoms. Specific examples thereof include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, and an adamantyl group. In view of ease of availability, a cyclopropyl group, a cyclobutyl group, and an adamantyl group are preferred.

[0030] R may be, for example, an aryl group having 6 to 18 carbon atoms, specific examples of which include a phenyl group, a naphthyl group, and a benzophenone structure.

[0031] R may be, for example, a heterocyclic group having 5 to 18 carbon atoms. Specific examples of the heterocyclic group include heteroaryl groups such as a pyridyl group, a γ-butyrolactone group, and an ε-caprolactone group.

[0032] Examples of the substituent that R may have include a group or atom selected from the group consisting of an alkyl group, an aryl group, a carboxy group, an alkoxycarbonyl group (-COOR"), a cyano group, a hydroxy group, an amino group (-NR"R'"), an amide group (-CONR"R'"), a halogen atom, an allyl group, an epoxy group, an alkoxy group (-OR"), a siloxy group, or a group exhibiting hydrophilicity or ionicity. R" and R'" each independently have the same meaning as R.

[0033] The alkoxycarbonyl group of the above substituent includes, for example, a methoxycarbonyl group. Examples of the amino group of the substituent include an amino group, a monomethylamino group, and a dimethylamino group. Examples of the amide group of the above substituent include a carbamoyl group (-CONH2), an N-methylcarbamoyl group (-CONHMe), and an N,N-dimethylcarbamoyl group (dimethylamide group: -CONMe2), where Me represents a methyl group.

[0034] Examples of the halogen atom in the above substituent include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the alkoxy group for the above substituent include alkoxy groups having 1 to 12 carbon atoms, and a specific example is a methoxy group. Examples of the hydrophilic or ionic substituent include an alkali salt of a carboxyl group or an alkali salt of a sulfoxyl group, a poly(alkylene oxide) group such as a polyethylene oxide group or a polypropylene oxide group, and a cationic substituent such as a quaternary ammonium base.

[0035] Z is a terminal group of the macromonomer (A). Examples of the terminal group of the macromonomer (A) include a hydrogen atom and a group derived from a radical polymerization initiator, similar to the terminal groups of polymers obtained by known radical polymerization.

[0036] The macromonomer (A) preferably contains structural units derived from a (meth)acrylic monomer in a proportion of 80% by mass or more relative to 100% by mass of all structural units constituting the macromonomer (A), and is particularly preferably one having a structure of the following formula (2): At least a portion of the structural units derived from the (meth)acrylic monomer are structural units derived from alkyl (meth)acrylate (a).

[0037] [ka]

[0038] In formula (2), n is a natural number between 20,000 and 100,000. n Each of the n R's can be independently the same as the R's described above. n may be the same or different. X n The same P as in the above formula (a') can be used for n X. n may be the same or different. Z is a terminal group. Z may be the same terminal group as Z in formula (1).

[0039] The number average molecular weight (Mn) of the macromonomer (A) is preferably 1,000 to 30,000, more preferably 2,000 to 20,000, and even more preferably 3,000 to 10,000. When the number average molecular weight of the macromonomer (A) is equal to or greater than the lower limit, entanglement between molecules increases, tending to improve holding power. When the number average molecular weight of the macromonomer (A) is equal to or less than the upper limit, unevenness-following ability tends to improve. The number average molecular weight of the macromonomer (A) is a value measured by gel permeation chromatography (GPC) and converted into standard polystyrene.

[0040] The glass transition temperature (hereinafter referred to as "Tg A The Tg is preferably -20°C or lower, more preferably -50°C or lower. A The lower limit of Tg is not particularly limited, but is, for example, -100°C. A When the temperature is equal to or lower than the upper limit, the softness at low temperatures tends to be good. Tg A is the glass transition temperature of a homopolymer of one type of monomer that forms the macromonomer (A), and is a value calculated by Fox's formula when multiple types of monomers form the macromonomer (A). For example, when macromonomer (A) is composed of a structural unit derived from monomer p, a structural unit derived from monomer q, and a structural unit derived from monomer r, the glass transition temperature (unit: ° C.) of macromonomer (A) is determined as Tg calculated from the glass transition temperature and mass fraction of each homopolymer of monomer p, monomer q, or monomer r using the Fox formula below. 1 / (273+Tg)=Σ(Wi / (273+Tgi)) (In the formula, Wi represents the mass fraction of monomer i, and Tgi represents the glass transition temperature (°C) of the homopolymer of monomer i.) The glass transition temperature of the homopolymer of the monomer i can be determined from literature values, such as those listed in the Polymer Handbook (J. Brandrup, Interscience, 1989) or the catalog of the monomer.

[0041] The macromonomer (A) may be one produced by a known method or a commercially available one. Examples of methods for producing the macromonomer (A) having a radically polymerizable group include a method using a cobalt chain transfer agent, a method using an α-substituted unsaturated compound such as α-methylstyrene dimer as a chain transfer agent, a method in which the radically polymerizable group is chemically bonded to a polymer, and a method using thermal decomposition. Among these, the method of producing macromonomer (A) using a cobalt chain transfer agent is preferred because it requires fewer production steps and uses a catalyst with a high chain transfer constant. The structure of macromonomer (A) produced using a cobalt chain transfer agent corresponds to the above formula (1). Examples of methods for producing a macromonomer (A) having a functional group that can be added to a polymer made of a vinyl monomer (B) include a method of copolymerizing a vinyl monomer having the corresponding functional group, a method of introducing a functional group using a chain transfer agent such as thioglycol or thioglycolic acid, and a method of introducing a functional group using an initiator.

[0042] Examples of the polymerization method for producing the macromonomer (A) include bulk polymerization, solution polymerization, suspension polymerization, emulsion polymerization, and other aqueous dispersion polymerization methods. In particular, when a cobalt chain transfer agent is used for production, the aqueous dispersion polymerization method is preferred because of its simple recovery process. Examples of methods for chemically bonding a radically polymerizable group to a polymer include a production method in which the halogen group of a polymer having a halogen group is substituted with a compound having a radically polymerizable carbon-carbon double bond; a method in which a vinyl monomer having an acid group is reacted with a vinyl polymer having an epoxy group; a method in which a vinyl polymer having an epoxy group is reacted with a vinyl monomer having an acid group; and a method in which a vinyl polymer having a hydroxyl group is reacted with a diisocyanate compound to obtain a vinyl polymer having an isocyanate group, and then this vinyl polymer is reacted with a vinyl monomer having a hydroxyl group. Any of these methods may be used for production.

[0043] <Vinyl Monomer (B)> The vinyl monomer (B) may be the same as the monomer used to obtain the macromonomer (A). The vinyl monomer (B) may be one type or a combination of two or more types. The vinyl monomer (B) may be a (meth)acrylic monomer, a non-(meth)acrylic monomer, or a combination of these.

[0044] The vinyl monomer (B) is preferably an acrylic (meth)alkylate (b) having an alkyl group having 1 to 4 carbon atoms. When the structural unit derived from the vinyl monomer (B) contains a structural unit derived from the acrylic (meth)alkylate (b), the copolymer (I) is likely to undergo phase separation, and is likely to exhibit excellent holding power. In addition, the copolymer (I) also has excellent adhesive properties. The alkyl group contained in the acrylic (meth)alkylate (b) may be linear or branched. Specific examples of the acrylic (meth)alkylate (b) include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, and t-butyl (meth)acrylate. The alkyl (meth)acrylate (b) may be used alone or in combination of two or more. The acrylic (meth)alkylate (b) is preferably an acrylate from the viewpoint of polymerizability.

[0045] The acrylic (meth)alkylate (b) may be used in combination with other vinyl monomers. The other vinyl monomer can be appropriately selected from the monomers for obtaining the macromonomer (A) described above, but (meth)acrylic acid, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isobornyl (meth)acrylate, cyclohexyl (meth)acrylate, styrene, etc. are preferred.

[0046] When the macromonomer (A) is added to a polymer composed of a vinyl monomer (B), it is suitable that the vinyl monomer (B) contains a functional group capable of reacting with the functional group of the macromonomer (A).

[0047] The proportion of the structural units derived from the acrylic (meth)alkylate (b) relative to 100% by mass of all structural units derived from the vinyl monomer (B) is preferably 60% by mass or more, more preferably 80% by mass or more, and may be 100% by mass.

[0048] The copolymer (I) has a macromonomer (A) unit and a polymer unit of a vinyl monomer (B). The copolymer (I) may contain at least one selected from the group consisting of a polymer having only structural units derived from the macromonomer (A), a polymer having structural units derived from one or more vinyl monomers (B), and unreacted macromonomer (A) and unreacted vinyl monomer (B). Furthermore, the copolymer (I) may contain at least one selected from the group consisting of a block type having repeating units derived from the macromonomer (A) and the vinyl monomer (B), and a graft type having repeating units derived from the macromonomer (A) in the side chain and a polymer of the vinyl monomer (B) in the main chain.

[0049] In the copolymer (I), the content of the structural unit derived from the macromonomer (A) is preferably 3 to 30% by mass, more preferably 5 to 25% by mass, and even more preferably 10 to 20% by mass, relative to 100% by mass of the copolymer (I). When the content of the structural unit derived from the macromonomer (A) is within the above range, the adhesive layer formed has better conformability to irregularities when attached and better shape retention when not attached. The content of the structural units derived from the vinyl monomer (B) is preferably from 70 to 97% by mass, more preferably from 75 to 95% by mass, and even more preferably from 80 to 90% by mass, relative to 100% by mass of the copolymer (I).

[0050] The weight average molecular weight (Mw) of the copolymer (I) is preferably 50,000 to 2,000,000, more preferably 100,000 to 1,500,000, and even more preferably 300,000 to 1,000,000. When the weight average molecular weight of the copolymer (I) is at least the lower limit, the durability of the adhesive layer tends to be good, and when it is at most the upper limit, the coatability of the resin composition tends to be good. The weight average molecular weight of the copolymer (I) is a value measured by gel permeation chromatography (GPC) and converted into standard polystyrene.

[0051] The copolymer (I) preferably has a deformation amount of 15% or less, more preferably 10% or less, and even more preferably 5% or less, in a creep test under conditions of 23°C, 100 Pa, and 10 minutes (hereinafter also referred to as "deformation amount at 23°C"). The lower limit of the deformation amount at 23°C is not particularly limited, but is, for example, 1%. When the deformation amount at 23°C is equal to or less than the upper limit, the adhesive layer formed has excellent shape retention when not attached, and is less likely to have problems such as the adhesive layer protruding from the separation film during storage while sandwiched between the separation films, adhesive residue when the adhesive layer and the separation film are peeled off, and the inability to re-peel after lamination, resulting in reduced yield. The deformation amount at 23° C. can be adjusted, for example, by the proportion of the structural units derived from alkyl(meth)acrylate (a) in the macromonomer (A) and the molecular weights of the macromonomer and copolymer (I). For example, as the proportion of the structural units derived from alkyl(meth)acrylate (a) in the macromonomer (A) increases, the deformation amount at 23° C. tends to decrease. The detailed method for measuring the amount of deformation in the creep test is as shown in the examples below.

[0052] The copolymer (I) preferably has a deformation amount of 100% or more, more preferably 200% or more, and even more preferably 300% or more, in a creep test under conditions of 70°C, 1000 Pa, and 1 minute (hereinafter also referred to as "deformation amount at 70°C"). The upper limit of the deformation amount at 70°C is not particularly limited, but is, for example, 1000%. If the deformation amount at 70°C is equal to or greater than the lower limit, the formed adhesive layer has excellent irregularity-following ability during lamination, and even if irregularities exist on at least one surface of the members to be laminated, air bubbles are unlikely to remain between the adhesive layer and the irregularities. The deformation amount at 70°C can be adjusted, for example, by the proportion of the structural units derived from alkyl(meth)acrylate (a) in the macromonomer (A) and the molecular weights of the macromonomer and copolymer (I). For example, as the proportion of the structural units derived from alkyl(meth)acrylate (a) in the macromonomer (A) increases, the deformation amount at 70°C tends to increase.

[0053] The storage modulus G' of the copolymer (I) at -20°C and 1 Hz (hereinafter also referred to as "G' at -20°C") is preferably 700 kPa or less, more preferably 400 kPa or less, and even more preferably 200 kPa or less. The lower limit of G' at -20°C is not particularly limited, but is, for example, 10 kPa. When G' at -20°C is the above upper limit or less, the adhesive layer formed will have excellent softness when used at low temperatures. For example, in foldable display applications, members bonded via an adhesive layer may be bent at low temperatures. If the adhesive layer has excellent flexibility when used at low temperatures, the members bonded via the adhesive layer can be protected when bent at low temperatures, and the durability of the adhesive layer itself will also be good. G' at -20°C can be adjusted, for example, by the proportion of structural units derived from alkyl(meth)acrylate (a) in macromonomer (A) and the proportion of macromonomer (A) in copolymer (I). For example, as the proportion of structural units derived from alkyl(meth)acrylate (a) in macromonomer (A) increases, G' at -20°C tends to decrease. The detailed method for measuring the storage modulus G' is as shown in the examples below.

[0054] The copolymer (I) preferably has a deformation of 15% or less at 23° C., a deformation of 100% or more at 70° C., and a G′ of 700 kPa or less at −20° C. More preferred values ​​for the deformation at 70° C., the deformation at 23° C., and the G′ at −20° C. are as described above.

[0055] The melt viscosity of copolymer (I) at 130°C is preferably 20 to 800 Pa·s, more preferably 20 to 600 Pa·s, even more preferably 50 to 600 Pa·s, and particularly preferably 100 to 500 Pa·s. When the melt viscosity of copolymer (I) at 130°C is within the above range, the resin composition can be directly heated and coated by a hot melt method. The melt viscosity can be measured, for example, using a viscoelasticity measuring device Rheosol-G5000 manufactured by UBM Co., Ltd. In the present invention, the viscosity (η*) value measured at 130°C with a 25 mmφ cone plate, a strain of 0.7%, and 0.02 Hz was defined as the melt viscosity value at 130°C.

[0056] The copolymer (I) preferably has a relative dielectric constant of 3.5 or less. If the relative dielectric constant is 3.5 or less, the adhesive layer can be made thinner when mounted on a touch panel, and the responsiveness of the touch panel will be improved.

[0057] The method for producing the copolymer (I) is not particularly limited. For example, when the macromonomer (A) has a radical polymerizable group, a method of polymerizing a monomer mixture containing the macromonomer (A) and a vinyl monomer (B) can be used. The resin composition can be produced by known polymerization methods such as solution polymerization, suspension polymerization, emulsion polymerization, etc. Since the resin composition is used for a pressure-sensitive adhesive, the solution polymerization method is preferred. When the macromonomer (A) has an addition-reactive functional group and at least a portion of the vinyl monomer (B) has a functional group that can react with the functional group of the macromonomer (A), a method can be used in which a polymer of the vinyl monomer (B) is reacted (addition reaction) with the macromonomer (A).

[0058] The content of the copolymer (I) in the present resin composition is preferably 50 to 100 mass %, more preferably 75 to 100 mass %, and even more preferably 90 to 100 mass %, based on 100 mass % of the present resin composition.

[0059] (Other ingredients) The resin composition may contain known components that are typically blended into pressure-sensitive adhesive compositions. For example, fillers can be contained to impart heat resistance, thermal conductivity, flame retardancy, electrical conductivity, etc. Examples of fillers include inorganic fillers such as metal powders such as zinc oxide powder and titanium oxide powder, carbon black such as acetylene black, talc, glass powder, silica powder, conductive particles, and glass powder, and organic fillers such as polyethylene powder, polyester powder, polyamide powder, fluororesin powder, polyvinyl chloride powder, epoxy resin powder, and silicone resin powder. These fillers may be used alone or in combination of two or more.

[0060] In order to form a crosslinked adhesive layer, a functional group may be introduced into the copolymer (I), and a crosslinking agent or a polymerization initiator may be contained in the resin composition. Examples of the crosslinking agent include isocyanate-based, epoxy-based, metal chelate-based, photocurable, melamine-based, aziridine-based, etc. Two or more crosslinking agents can also be used in combination.

[0061] Examples of isocyanate-based crosslinking agents include aromatic polyisocyanates such as xylylene diisocyanate, diphenylmethane diisocyanate, triphenylmethane triisocyanate, and tolylene diisocyanate, aliphatic or alicyclic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, and hydrogenated products of the above-mentioned aromatic polyisocyanates, dimers or trimers of these polyisocyanates, and adducts of these polyisocyanates with polyols such as trimethylolpropane. These may be used alone or in combination of two or more.

[0062] Examples of epoxy crosslinking agents include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, bisphenol A epoxy resin, N,N,N',N'-tetraglycidyl-m-xylylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane, N,N-diglycidylaniline, and N,N-diglycidyltoluidine.

[0063] Examples of metal chelate crosslinking agents include those in which a polyvalent metal is covalently or coordinately bonded to an organic compound. Examples of polyvalent metals include aluminum, nickel, chromium, copper, iron, tin, titanium, zinc, cobalt, manganese, and zirconium. Examples of organic compounds that form covalent or coordinate bonds include those containing oxygen atoms, such as ketone compounds such as acetylacetone, alkyl esters, alcohol compounds, carboxylic acid compounds, and ether compounds.

[0064] Examples of melamine-based crosslinking agents include hexamethoxymethylmelamine, hexaethoxymethylmelamine, hexapropoxymethylmelamine, hexaptoxymethylmelamine, hexapentyloxymethylmelamine, hexahexyloxymethylmelamine, and melamine resins. Examples of aziridine-based crosslinking agents include tetramethylolmethane-tri-β-aziridinylpropionate, trimethylolpropane-tri-β-aziridinylpropionate, N,N'-diphenylmethane-4,4'-bis(1-aziridinecarboxamide), and N,N'-hexamethylene-1,6-bis(1-aziridinecarboxamide).

[0065] The resin composition can be crosslinked by adding a reaction initiator such as a photopolymerization initiator, or by adding at least one selected from a crosslinking agent, a vinyl monomer, an oligomer component, and a reaction initiator such as a photopolymerization initiator, and irradiating it with ultraviolet light or the like.

[0066] Examples of the photopolymerization initiator include 2,2-dimethoxy-1,2-diphenylethan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1-(4-(2-hydroxyethoxy)phenyl)-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-1-[4-{4-(2-hydroxy-2-methyl-propionyl)benzyl}phenyl]-2-methyl-propan-1-one, oligo(2-hydroxy-2-methyl-1-(4-(1-methylvinyl)phenyl)propanone), phenylglyoxylyl Examples of suitable benzophenones include methyl benzoate, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, benzophenone, 4-methyl-benzophenone, 2,4,6-trimethylbenzophenone, 2,4,6-trimethylbenzophenone, 4-phenylbenzophenone, 3,3'-dimethyl-4-methoxybenzophenone, 4-(1,3-acryloyl-1,4,7,10,13-pentaoxotridecyl)benzophenone, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide.

[0067] Examples of crosslinking agents include polyfunctional (meth)acrylates having two or more (meth)acryloyl groups, polyfunctional organic resins having two or more functional groups such as isocyanate groups, epoxy groups, melamine groups, glycol groups, siloxane groups, and amine groups, and organometallic compounds having metal complexes of zinc, aluminum, sodium, zirconium, calcium, etc. Examples of polyfunctional (meth)acrylates include triethylene glycol diacrylate, polyalkylene glycol diacrylate, bisphenol A-ethylene oxide (EO) / propylene oxide (PO)-modified diacrylate, alkoxylated hexanediol diacrylate, polyisobutylene diacrylate, alkoxylated trimethylolpropane triacrylate, pentaerythritol triacrylate, alkoxylated pentaerythritol triacrylate, alkoxylated pentaerythritol tetraacrylate, alkoxylated dipentaerythritol pentaacrylate, and caprolactone-modified dipentaerythritol penta- and hexaacrylate.

[0068] Examples of the vinyl monomer include the same ones as those used in the macromonomer (A).

[0069] Examples of oligomer components include (meth)acrylic, urethane, isoprene, isoprene acrylate, urethane acrylate, polyester acrylate, styrene, epoxy, and olefin, which may have a photopolymerizable reactive group.

[0070] The resin composition may contain various additives, such as a tackifier resin, an antioxidant, a light stabilizer, a metal deactivator, an antiaging agent, a moisture absorbent, a rust inhibitor, and a hydrolysis inhibitor, as needed. The resin composition may also contain a reaction catalyst (such as a tertiary amine compound, a quaternary ammonium compound, or a tin laurate compound).

[0071] Examples of antioxidants include phenol-based, phosphorus-based, hydroxylamine-based, and sulfur-based antioxidants. Among these, phenol-based and phosphoric acid-based antioxidants are preferred because they cause less coloration of the resin after heating. These antioxidants may be used alone or in combination. The content of the antioxidant is preferably in the range of 0.1 to 5 parts by mass per 100 parts by mass of the copolymer (I).

[0072] The present resin composition can be produced, for example, by producing the copolymer (I) as described above and then adding other components as required.

[0073] The resin composition can be formed into a sheet and used as an adhesive sheet. The pressure-sensitive adhesive sheet can be applied in a solution state using a solvent or in a solution state diluted with a low-molecular-weight component in the composition, or can be prepared as a hot-melt pressure-sensitive adhesive composition without using a solvent. A hot-melt pressure-sensitive adhesive composition without using a solvent can be made thicker than a pressure-sensitive adhesive composition using a solvent, and can therefore be made thick enough to fill gaps between components of an image display device, for example. In addition, the pressure-sensitive adhesive sheet can be diluted with other polymerizable components or cross-linking agents and then applied, and then cured by ultraviolet irradiation, heating, etc.

[0074] The pressure-sensitive adhesive sheets obtained from this resin composition can be used to bond various members and exhibit very good adhesive performance. For example, by applying them to transparent plastic films or processing them into adhesive films, they can be used to attach window films for vehicles and buildings, or to attach labels in labeling. Furthermore, by processing them into transparent double-sided pressure-sensitive adhesive sheets, they can be used to attach various panels in image display devices such as liquid crystal panels, or to attach transparent plate materials such as glass.

[0075] Furthermore, when the resin composition is applied in the form of a solution using a solvent or in the form of a solution diluted with a component other than the copolymer (I), it can be used for the same purposes as the pressure-sensitive adhesive sheet.

[0076] The resin composition is excellent in conformity to irregularities when laminated and in shape retention when not laminated, and is therefore useful for laminating components where at least one of the components has irregularities on the surface (uneven component). For example, when an uneven member is bonded to a member having an organic light-emitting diode (OLED) using this resin composition, the resin composition fills the unevenness of the uneven member without any gaps, making the surface on the OLED side smooth and allowing a clear image to be displayed without uneven patterns. In particular, in addition to the above properties, it also has excellent flexibility when used at low temperatures, making it suitable for bonding components that make up foldable displays (OLEDs, protective films, uneven substrates for pressure-sensitive sensors, polarizing plates with camera holes, etc.). [Example]

[0077] The present invention will be described in more detail below with reference to examples and comparative examples. However, the present invention is not limited to these examples. In the examples, "parts" means "parts by mass." Measurements and evaluations in the examples were carried out by the methods shown below.

[0078] (molecular weight of macromonomer) A 0.2% by mass solution of macromonomer (a) in tetrahydrofuran was prepared, and 10 μL of the solution was injected into a GPC system (HLC-8320, manufactured by Tosoh Corporation) equipped with columns manufactured by Tosoh Corporation (TSKgel SuperHZM-M×HZM-M×HZ2000 (4.6 mm ID×15 cm L), TSKguardcolumn SuperHZ-L (4.6 mm ID×2.0 cm L)). GPC was performed under conditions of a flow rate of 0.35 mL / min, eluent: tetrahydrofuran (stabilizer: BHT), and column temperature: 40°C, and the number average molecular weight (Mn) and weight average molecular weight (Mw) were determined in terms of standard polystyrene.

[0079] (Molecular weight of copolymer) A 0.27% by mass solution of copolymer (A) in tetrahydrofuran was prepared, and 10 μL of the solution was injected into a GPC system (HLC-8320, manufactured by Tosoh Corporation) equipped with two Tosoh columns (TSKgel SuperHZMH x 2 (6.0 mm ID x 15 cm L), TSKguardcolumn SuperHZ-H (4.6 mm ID x 3.5 cm L)). GPC was performed at a flow rate of 0.5 mL / min, eluent: tetrahydrofuran (stabilizer: BHT), and column temperature: 40°C, and the number average molecular weight (Mn) and weight average molecular weight (Mw) were determined in terms of standard polystyrene.

[0080] (Creep test) The sample was applied to a separator film and dried under vacuum at 130°C for 6 hours to remove the solvent. The resulting dried sample was subjected to a creep test at 23°C or 70°C using a dynamic viscoelasticity measuring device (Thermo Fisher Scientific, HAAKE MARS 60) to determine the strain (deformation). A cone plate with a diameter of 35 mm and a cone angle of 1° was used for the creep test. In the creep test at 23°C, a constant stress of 100 Pa was applied and the strain was measured after 10 minutes. In the creep test at 70°C, a constant stress of 1000 Pa was applied and the strain was measured after 1 minute. The sample was attached to the cone plate at 130°C. The specified measurement gap for the cone was 0.052 mm, while the trimming gap was 0.1 mm.

[0081] (storage modulus G') The storage modulus G' of dried samples prepared in the same manner as in the creep test was measured at -20°C using a dynamic viscoelasticity measuring device (Thermo Fisher Scientific, HAAKE MARS 60). The storage modulus G' was measured using 20 mm diameter parallel plates with a 1 mm gap, a 1 Hz frequency, and a 0.1% strain. The sample was attached to the parallel plates at 130°C and trimmed with a 1.05 mm gap.

[0082] (Non-volatile content) Approximately 1 g of the sample was placed on an aluminum dish and dried in an oven equipped with a fan at 105°C for 2 hours. The mass before and after drying was measured using an electronic balance, and the nonvolatile content was calculated using the following formula. Nonvolatile content (%) = (mass of sample after drying (g) / mass of sample before drying (g)) x 100

[0083] (B type viscosity) The viscosity was measured using a B-type viscometer (TVB10 type viscometer manufactured by Toki Sangyo Co., Ltd.) with an M4 rotor at a rotation speed of 60 rpm and a measurement temperature of 25°C.

[0084] (Materials used) MMA: methyl methacrylate, manufactured by Mitsubishi Chemical Corporation, trade name: Acryester M. BMA: n-butyl methacrylate, manufactured by Mitsubishi Chemical Corporation, trade name: Acryester B. EHMA: 2-ethylhexyl methacrylate, manufactured by Mitsubishi Chemical Corporation, trade name: Acryester EH. SLMA: a mixture of an alkyl methacrylate having an alkyl group with 12 carbon atoms and an alkyl methacrylate having an alkyl group with 13 carbon atoms, manufactured by Mitsubishi Chemical Corporation, trade name: Acryester SL. iSMA: Isostearyl methacrylate, manufactured by Shin-Nakamura Chemical Co., Ltd., trade name: NK Ester S-1800M. BA: n-butyl acrylate, manufactured by Mitsubishi Chemical Corporation. EHA: 2-ethylhexyl acrylate, manufactured by Mitsubishi Chemical Corporation. AA: acrylic acid, manufactured by Mitsubishi Chemical Corporation. 4HBA: 4-hydroxybutyl acrylate, manufactured by Mitsubishi Chemical Corporation. AMBN: 2,2'-azobis(2-methylbutyronitrile), manufactured by Otsuka Chemical Co., Ltd.

[0085] Example 1 <Production of macromonomers> A four-neck flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet was charged with 100 parts of SLMA, 0.00075 parts of bis[(difluoroboryl)diphenylglyoximate]cobalt(II) as a chain transfer agent, and 58 parts of ethyl acetate. Oxygen was substituted by nitrogen bubbling. Next, 0.4 parts of AMBN as a polymerization initiator and 2 parts of ethyl acetate were added. The external temperature was then raised to 90°C in a water bath, and the reaction was carried out under reflux for 2 hours. Next, 0.2 parts of AMBN and 20 parts of ethyl acetate were added dropwise over 1 hour, and the mixture was then maintained under reflux for another 2 hours. The reaction solution was then cooled to 40°C to obtain a solution containing a macromonomer. Ethyl acetate was added to this solution to adjust the nonvolatile content to 50% by mass.

[0086] <Production of copolymer> A four-neck flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet was charged with 25 parts of ethyl acetate as the solvent, 2 parts of isopropyl alcohol (IPA), and 30 parts of the prepared macromonomer solution (concentration: 50% by mass). The external temperature was raised to 85°C in a water bath under nitrogen gas flow. After the reflux state stabilized, a mixture consisting of 20 parts of ethyl acetate, 85 parts of BA, and 0.13 parts of Niper BK40 MT (manufactured by NOF Corporation) was added dropwise over 4 hours. After holding for 1 hour after the completion of the dropwise addition, a mixture consisting of 0.3 parts of Perocta O (manufactured by NOF Corporation) and 15 parts of ethyl acetate was added over 1 hour. After holding for 2 hours, 0.5 parts of "Irganox 1010" (BASF product name) as an antioxidant and 23 parts of ethyl acetate were added, and the mixture was cooled to room temperature to obtain a resin composition containing a copolymer (BA / SLMA = 85 / 15).

[0087] Example 2 A resin composition containing a copolymer (BA / 4HBA / SLMA=77 / 8 / 15) was obtained in the same manner as in Example 1, except that in <Production of Copolymer> of Example 1, the amount of IPA was changed from 2 parts to 3 parts, and the amount of BA was changed from 85 parts to 77 parts of BA and 4 parts of 4HBA.

[0088] Example 3 A resin composition containing a copolymer (BA / EHA / AA / SLMA=55 / 26 / 4 / 15) was obtained in the same manner as in Example 1, except that in <Production of Copolymer> of Example 1, the 85 parts of BA were changed to 55 parts of BA, 26 parts of EHA, and 4 parts of AA.

[0089] Example 4 A resin composition containing a copolymer (BA / EHMA 85 / 15) was obtained in the same manner as in Example 1, except that in the <Production of macromonomer> of Example 1, SLMA was replaced with EHMA, and in the <Production of copolymer>, the amount of IPA was changed from 2 parts to 1.5 parts.

[0090] Example 5 A resin composition containing a copolymer (BA / EHMA 85 / 15) was obtained in the same manner as in Example 1, except that in <Production of Macromonomer> of Example 1, SLMA was replaced with iSMA.

[0091] Example 6 A resin composition containing a copolymer (BA / SLMA / BMA=85 / 7 / 8) was obtained in the same manner as in Example 1, except that in <Production of Macromonomer> of Example 1, the SLMA was replaced with a mixture of SLMA and BMA (SLMA:BMA=7:8 (mass ratio)).

[0092] Example 7 A resin composition containing a copolymer (BA / SLMA=10 / 90) was obtained in the same manner as in Example 1, except that in <Production of copolymer> of Example 1, the amount of ethyl acetate initially charged was changed from 25 parts to 30 parts, the amount of macromonomer solution was changed from 30 parts to 20 parts, and the amount of BA was changed from 85 parts to 90 parts.

[0093] Example 8 A resin composition containing a copolymer (BA / EHMA / BMA=85 / 11 / 4) was obtained in the same manner as in Example 1, except that in <Production of macromonomer>, SLMA was replaced with a mixture of EHMA and BMA (EHMA:BMA=11:4 (mass ratio)), and in <Production of copolymer>, the amount of IPA was changed from 2 parts to 1.5 parts.

[0094] (Comparative Example 1) Without conducting <Production of Macromonomer>, in <Production of Copolymer>, the initial charged ethyl acetate was changed from 25 parts to 40 parts, and 15 parts of SLMA was further added to the mixture to be dropped. A resin composition containing a copolymer (BA / SLMA = 85 / 15, random copolymer) was obtained in the same manner as in Example 1.

[0095] (Comparative Example 2) <Production of Dispersant 1> Into a polymerization apparatus equipped with a stirrer, a cooling pipe, and a thermometer, 900 parts of deionized water, 60 parts of 2-sulfoethyl methacrylate sodium, 10 parts of potassium methacrylate, and 12 parts of MMA were put and stirred. While purging the inside of the polymerization apparatus with nitrogen, the temperature was raised to 50 °C. 0.08 part of 2,2'-azobis(2-methylpropionamidine) dihydrochloride was added thereto as a polymerization initiator, and the temperature was further raised to 60 °C. After the temperature rise, using a dropping pump, MMA was continuously dropped at a rate of 0.24 part / min for 75 minutes. After holding the reaction solution at 60 °C for 6 hours, it was cooled to room temperature to obtain Dispersant 1 having a solid content of 10% by mass, which was a transparent aqueous solution.

[0096] <Production of MMA Macromonomer> Into a polymerization apparatus equipped with a stirrer, a cooling pipe, and a thermometer, 145 parts of deionized water, 0.1 part of sodium sulfate, and 0.25 part of Dispersant 1 (solid content 10% by mass) were put and stirred to obtain a uniform aqueous solution. Next, 100 parts of MMA, 0.0035 part of cobalt(II) bis[(difluoroboryl)diphenylglyoximate] as a chain transfer agent, and 0,35 part of Perocta O (manufactured by NOF Corporation) as a polymerization initiator were added to obtain an aqueous suspension. Next, the inside of the polymerization apparatus was purged with nitrogen, the temperature was raised to 80 °C and reacted for 1 hour, and further raised to 90 °C and held for 1 hour to increase the polymerization rate. Thereafter, the reaction solution was cooled to 40 °C to obtain an aqueous suspension containing a macromonomer. This aqueous suspension was filtered, the filtrate was washed with deionized water, dehydrated, and dried at 40 °C for 16 hours to obtain an MMA macromonomer. <mm

[0097] <Production of Copolymer> A resin composition containing a copolymer (BA / AA / MMA=81 / 4 / 15) was obtained in the same manner as in Example 1, except that in <Production of Copolymer> of Example 1, the amount of ethyl acetate initially charged was changed from 25 parts to 40 parts, the amount of IPA was changed from 2 parts to 5 parts, the amount of macromonomer solution was changed from 30 parts to 15 parts of the above MMA macromonomer (in a dry state), and the amount of BA was changed from 85 parts to 81 parts of BA and 4 parts of AA.

[0098] (Comparative Example 3) A resin composition containing a copolymer (BA / BMA=85 / 15) was obtained in the same manner as in Example 1, except that in the <Production of macromonomer> of Example 1, SLMA was replaced with BMA, and in the <Production of copolymer>, the amount of IPA was changed from 2 parts to 1.5 parts.

[0099] The composition, physical properties (storage modulus G', creep test strain) and molecular weight (Mn, Mw) of the copolymer contained in the resin composition obtained in each example, the molecular weight (Mn, Mw) and glass transition temperature (Tg) of the macromonomer, and the B-type viscosity of the resin composition are shown in Tables 1 and 2. When measuring the B-type viscosity, the nonvolatile content was adjusted to 50 mass% by adding ethyl acetate to the resin composition as needed.

[0100] [Table 1]

[0101] [Table 2]

[0102] The resin compositions of Examples 1 to 8 had deformations of 15% or less at 23°C, indicating that they are resistant to deformation at room temperature and have excellent shape retention when not laminated. Furthermore, the deformations at 70°C were 100% or more, indicating that they are prone to deformation at high temperatures and have excellent conformability to irregularities when laminated. Furthermore, the storage modulus G' at -20°C was 700 kPa or less, indicating that they are soft when used at low temperatures. On the other hand, the resin composition of Comparative Example 1, which did not use a macromonomer, showed a large amount of deformation at 23°C. The resin composition of Comparative Example 2, which used a macromonomer consisting only of MMA units, had a small deformation amount at 70°C and a high storage modulus G' at -20°C. The resin composition of Comparative Example 3, which used a macromonomer consisting only of BMA units, had a high storage modulus G' at -20°C.

Claims

1. The polymerizable composition includes a (meth)acrylic copolymer having a structural unit derived from a macromonomer (A) and a structural unit derived from a vinyl monomer (B), The resin composition for pressure-sensitive adhesives, wherein the macromonomer (A) has a structural unit derived from an alkyl (meth)acrylate (a) having an alkyl group having 8 to 30 carbon atoms.

2. 2. The pressure-sensitive adhesive resin composition according to claim 1, wherein a ratio of the structural units derived from the alkyl (meth)acrylate (a) to 100% by mass of all structural units constituting the macromonomer (A) is 70% by mass or more.

3. The resin composition for pressure-sensitive adhesives according to claim 1 or 2, wherein the structural unit derived from the alkyl (meth)acrylate (a) comprises a structural unit derived from an alkyl (meth)acrylate (a1) having an alkyl group having 12 to 30 carbon atoms.

4. The pressure-sensitive adhesive resin composition according to claim 3, wherein the proportion of the structural units derived from the alkyl (meth)acrylate (a1) relative to 100% by mass of all structural units constituting the macromonomer (A) is 40% by mass or more.

5. The pressure-sensitive adhesive resin composition according to any one of claims 1 to 4, wherein the structural unit derived from the vinyl monomer (B) comprises a structural unit derived from an acrylic (meth)alkylate (b) having an alkyl group having 1 to 4 carbon atoms.

6. 6. The pressure-sensitive adhesive resin composition according to claim 5, wherein the proportion of structural units derived from the acrylic (meth)alkylate (b) relative to 100% by mass of all structural units derived from the vinyl monomer (B) is 50% by mass or more.

7. 7. The pressure-sensitive adhesive resin composition according to claim 1, wherein the macromonomer (A) has a number average molecular weight of 1,000 to 30,000.

8. 8. The pressure-sensitive adhesive resin composition according to claim 1, wherein the (meth)acrylic copolymer has a weight average molecular weight of 50,000 to 2,000,000.

9. The (meth)acrylic copolymer has a deformation amount of 15% or less in a creep test under conditions of 23°C, 100 Pa, and 10 minutes, a deformation amount of 100% or more in a creep test under conditions of 70°C, 1000 Pa, and 1 minute, and a storage modulus G' at -20°C and 1 Hz of 700 kPa or less.

10. The pressure-sensitive adhesive resin composition according to any one of claims 1 to 9, which is used for bonding a member having an uneven surface to a member having an organic light-emitting diode.

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