Thermosetting acrylic resin composition, and adhesive sheet or adhesive tape

Abstract

Provided is a thermosetting acrylic resin composition in which generation of ultrafine bubbles during curing under heating and pressure is suppressed and which also has excellent adhesiveness. The thermosetting acrylic resin composition contains an acrylic copolymer (A) having a carboxyl group and a phenol resin (B). When the acrylic copolymer (A) is an acrylic copolymer (A-1) having a glass transition temperature of -35°C or lower, it contains an epoxy curing agent (C-1) in a specific content. As the phenol resin (B), it contains a novolak-type phenol resin (B-1) or a self-crosslinking phenol resin (B-2) in a specific content. When the phenol resin (B) contains a novolak-type phenol resin (B-1), it further contains an amine curing agent (C-2) in a specific content. A thermosetting acrylic resin composition.

Description

Technical Field

[0001] The present invention relates to a thermosetting acrylic resin composition, and an adhesive sheet or adhesive tape including an adhesive layer formed of the thermosetting acrylic resin composition.

Background Art

[0002] Generally, for the adhesive applications of electronic components and vehicle parts, thermosetting adhesive compositions that can be cured by heat treatment have been proposed. However, in recent years, electronic devices such as portable electronic information devices have been miniaturized and high-performance, and the electronic components mounted thereon also tend to be miniaturized. Therefore, thermosetting adhesive compositions used for the adhesive fixation of miniaturized electronic components to flexible printed circuits (FPCs), coverlays, and metals have been developed to sufficiently exhibit adhesive strength even in thin films and small areas.

[0003] For example, Patent Document 1 discloses a thermosetting adhesive composition characterized by containing 1 to 60 parts by weight of a phenol resin and 1 to 25 parts by weight of hexamethylenetetramine with respect to 100 parts by weight of a specific acrylic polymer.

[0004] Patent Document 2 discloses an adhesive composition containing an acrylic polymer including two specific acrylic copolymers, a resol-type phenol resin, and an epoxy resin.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] Since the amount of hexamethylenetetramine added to the thermosetting adhesive composition of Patent Document 1 is large, a large amount of ammonia gas is by-produced during the reaction, and there is a possibility that bubbles may be generated. Further, since the amount of hexamethylenetetramine added is large, the reaction tends to proceed, and there is a risk that the storage stability may deteriorate in a high-temperature environment, for example, in summer when the temperature is around 40°C.

[0007] Since the acrylic copolymer containing an epoxy group in the adhesive composition of Patent Document 2 is a special material, it is not easily available, and since it is expensive, the manufacturing cost is also high. Further, since the number of types is small, there is a problem that the material selection options are limited. In addition, since two types of acrylic copolymers having different monomer compositions are used, it is predicted that the compatibility is low, and there is a possibility that an adhesive composition having desired performance cannot be stably manufactured due to changes over time caused by phase separation.

[0008] The inventors of the present invention earnestly studied the performance required for the thermosetting adhesive composition. As a result, it was found that when the thinned adhesive composition (adhesive layer) is cured under heating and pressure, it overflows extremely slightly and flows out from between the adherend and the base material of the adhesive sheet or adhesive tape, and ultrafine bubbles of several μm to several tens of μm are generated. Further, it was found that these ultrafine bubbles are cavities generated in the trace where the adhesive composition flowed out, and the amount of generation thereof affects the degree of flow of the adhesive composition under heating and pressure (for example, the ease of flow due to melting of the resin component) and the amount of gas generated (for example, gas caused by by-products such as ammonia and water). And it was found that in the portion where a large amount of these ultrafine bubbles are generated, the adhesion area decreases and a part of the adhesive sheet or adhesive tape peels off, or water or chemicals invade or leak, which causes defective products.

[0009] An object of the present invention is to provide a thermosetting acrylic resin composition in which the generation of ultrafine bubbles during curing under heating and pressure is suppressed and which is excellent in adhesiveness, and an adhesive sheet or adhesive tape including an adhesive layer formed using the same.

Means for Solving the Problems

[0010] As a result of intensive studies to achieve the above object, the inventors of the present invention have completed the present invention relating to a thermosetting acrylic resin composition containing an acrylic copolymer, a phenol resin, and a curing agent, and an adhesive sheet or an adhesive tape provided with an adhesive layer formed using the same.

[0011] That is, the present invention includes the following aspects. [1] A thermosetting acrylic resin composition containing an acrylic copolymer (A) having a carboxyl group and a phenol resin (B), when the acrylic copolymer (A) is an acrylic copolymer (A-1) having a glass transition temperature of -35°C or lower, it further contains an epoxy curing agent (C-1), and the content of the epoxy curing agent (C-1) is 0.000002 parts by mass or more and 0.4 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer (A-1), when the phenol resin (B) contains a novolac-type phenol resin (B-1), the content of the novolac-type phenol resin (B-1) is 2 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer (A), and further contains an amine curing agent (C-2), and the content of the amine curing agent (C-2) is 0.002 parts by mass or more and 0.9 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer (A), when the phenol resin (B) does not contain the novolac-type phenol Resin (B-1), it contains a self-crosslinking type phenol resin (B-2), and the content of the self-crosslinking type phenol resin (B-2) is 2 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer (A), a thermosetting acrylic resin composition. [2] The thermosetting acrylic resin composition according to [1], wherein the acrylic copolymer (A) is an acrylic copolymer (A-1) having a glass transition temperature of -35°C or lower. [3] The thermosetting acrylic resin composition according to [1], wherein the acrylic copolymer (A) is an acrylic copolymer (A-2) having a glass transition temperature higher than -35°C. [4] The thermosetting acrylic resin composition according to any one of [1] to [3], wherein the phenolic resin (B) contains a novolak-type phenolic resin (B-1). [5] The thermosetting acrylic resin composition according to any one of [1] to [4], wherein the phenolic resin (B) contains a self-crosslinking type phenolic resin (B-2). [6] The phenolic resin (B) does not contain the novolak-type phenolic Resin (B-1), and contains a self-crosslinking type phenolic resin (B-2), the thermosetting acrylic resin composition according to any one of [1] to [3]. [7] Further, containing the amine-based curing agent, The content of the amine-based curing agent is 0.002 parts by mass or more and 0.9 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer (A), the thermosetting acrylic resin composition according to [5]. [8] Further, containing the amine-based curing agent, The content of the amine-based curing agent is 0.002 parts by mass or more and 0.9 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer (A), the thermosetting acrylic resin composition according to [6]. [9] Further, containing a filler, the thermosetting acrylic resin composition according to any one of [1] to [8].

[10] An adhesive sheet or adhesive tape including an adhesive layer formed of the thermosetting acrylic resin composition according to any one of [1] to [9].

[11] An adhesive sheet or adhesive tape including a base material and an adhesive layer formed of the thermosetting acrylic resin composition according to any one of [1] to [9] on at least one surface of the base material. [Advantages of the Invention]

[0012] According to the present invention, it is possible to provide a thermosetting acrylic resin composition in which the generation of ultrafine bubbles during curing under heating and pressure is suppressed and which has excellent adhesiveness, and a thermal adhesive sheet or thermal adhesive tape including an adhesive layer formed using the same. [Brief Description of the Drawings]

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0014] Hereinafter, preferred embodiments of the present invention will be described.

[0015] (Thermosetting Acrylic Resin Composition) The thermosetting acrylic resin composition of the present invention is a thermosetting acrylic resin composition containing an acrylic copolymer (A) having a carboxy group and a phenol resin (B), and as the acrylic copolymer (A), an acrylic copolymer (A-1) having a glass transition temperature (hereinafter referred to as "Tg") of -35°C or lower or an acrylic copolymer (A-2) having a Tg higher than -35°C, and as the phenol resin (B), a novolac type phenol resin (B-1) or a self-crosslinking type phenol resin (B-2) is included. Depending on the selection of the acrylic copolymers (A-1) and (A-2), the thermosetting acrylic resin composition of the present invention can include the following embodiments. The thermosetting acrylic resin composition of the present invention can also include a novolac-type phenol resin (B-1) and a self-crosslinking type phenol resin (B-2) as the phenol resin (B), and can also include other thermosetting resins (D).

[0016] <Embodiment (a): When the phenol resin (B) contains a novolac-type phenol resin (B-1)> Embodiment (a) can include the following embodiments (a1) and (a2). (a1) The acrylic copolymer (A) is an acrylic copolymer (A-1) having a Tg of -35°C or lower, further includes an epoxy-based curing agent (C-1), and the content of the epoxy-based curing agent (C-1) is 0.000002 parts by mass or more and 0.4 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer (A-1), the phenol resin (B) contains a novolac-type phenol resin (B-1), and the content of the novolac-type phenol resin (B-1) is 2 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer (A-1), further includes an amine-based curing agent (C-2), and the content of the amine-based curing agent (C-2) is 0.002 parts by mass or more and 0.9 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer (A). A thermosetting acrylic resin composition.

[0017] (a2) The acrylic copolymer (A) is an acrylic copolymer (A-2) having a Tg higher than -35°C, the phenol resin (B) contains a novolac-type phenol resin (B-1), and the content of the novolac-type phenol resin (B-1) is 2 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer (A-2), Furthermore, it contains an amine-based curing agent (C-2), and the content of the amine-based curing agent (C-2) is 0.002 parts by mass or more and 0.9 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer (A-2), a thermosetting acrylic resin composition.

[0018] <Embodiment (b): When the phenol resin (B) does not contain the novolac-type phenol Resin (B-1)> Embodiment (b) may include the following embodiments (b1) and (b2). (b1) The acrylic copolymer (A) is an acrylic copolymer (A-1) having a Tg of -35°C or lower, furthermore, it contains an epoxy-based curing agent (C-1), and the content of the epoxy-based curing agent (C-1) is 0.000002 parts by mass or more and 0.4 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer (A-1), the phenol resin (B) contains a self-crosslinking type phenol resin (B-2), and the content of the phenol resin (B-2) is 2 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer (A-1), a thermosetting acrylic resin composition.

[0019] (b2) The acrylic copolymer (A) is an acrylic copolymer (A-2) having a Tg higher than -35°C, the phenol resin (B) contains a self-crosslinking type phenol resin (B-2), and the content of the self-crosslinking type phenol resin (B-2) is 2 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer (A-2), a thermosetting acrylic resin composition.

[0020] <Acrylic copolymer (A)> The acrylic copolymer (A) used in the thermosetting acrylic resin composition of the present invention is a copolymer having a carboxy group. Note that "acrylic-based" is a general term including "acrylic" and "methacrylic", and the acrylic copolymer (A) is an acrylic copolymer and / or a methacrylic copolymer. The acid value of the acrylic copolymer (A) is preferably 0.1 mgKOH / g or more and 100 mgKOH / g or less, more preferably 1 mgKOH / g or more and 50 mgKOH / g or less, and even more preferably 4 mgKOH / g or more and 40 mgKOH / g or less. If the acrylic copolymer (A) does not have a carboxyl group, the adhesive strength will not increase sufficiently. When the acid value of the acrylic copolymer is within a predetermined range, ultrafine bubbles can be sufficiently suppressed, and sufficient adhesive strength can be obtained. This acid value is the amount (mg) of KOH required to neutralize 1 g of the acrylic copolymer (A), and can be measured by a method according to JIS K 0070:1992.

[0021] The Tg of the acrylic copolymer (A) is preferably in the range of -100 °C or more and 100 °C or less, and more preferably in the range of -80 or more and 20 °C or less. This Tg is a theoretical value and is a value obtained based on the following FOX equation. 1 / Tg = W1 / Tg1 + W2 / Tg2 + W3 / Tg3 + ··· + W i / Tg i Here, the subscripts 1, 2, 3, ··· i represent the monomer components constituting the copolymer, and W i is the weight fraction of the monomer component i, and Tg i represents the Tg of the homopolymer of the monomer component i. The Tg of the homopolymer can be the value described in Polymer Handbook, 4th Edition, by J. Brandrup, Wiley & Sons, published in 1998.

[0022] When the acrylic copolymer (A) is an acrylic copolymer (A-1) having a Tg of -35 °C or lower, ultrafine bubbles are likely to occur. By using the epoxy curing agent (C-1) in a predetermined content in combination, the generation of ultrafine bubbles can be sufficiently suppressed.

[0023] The acrylic copolymer (A) preferably contains, as units derived from the monomers forming the acrylic copolymer (A), at least the unit of the (meth)acrylic acid alkyl ester (AI) and the unit of the carboxy group-containing monomer (AII), and may further contain units of other monomer components as required. Note that "(meth)acrylic" is a general term encompassing "acrylic" and "methacrylic".

[0024] Examples of the above (meth)acrylic acid alkyl ester (AI) include ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, tridecyl (meth)acrylate, tetradecyl (meth)acrylate, etc. The alkyl group of the (meth)acrylic acid alkyl ester (AI) may be linear or branched. Among these, (meth)acrylic acid alkyl esters having an alkyl group with 2 to 14 carbon atoms are preferred, (meth)acrylic acid alkyl esters with 4 to 12 carbon atoms are more preferred, and n-butyl acrylate and 2-ethylhexyl acrylate are even more preferred. The above (meth)acrylic acid alkyl ester (AI) may be used alone or in combination of two or more.

[0025] (Meth)acrylic acid alkyl ester (AI) is preferably used as a main component for forming acrylic copolymer (A). The content of the unit of (meth)acrylic acid alkyl ester (AI) in acrylic copolymer (A) is preferably 80% by mass or more, more preferably 85% by mass or more, and from the point of containing a sufficient amount of units of carboxy group-containing monomer (AII), it is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 95% by mass or less.

[0026] The above carboxy group-containing monomer (AII) is not particularly limited as long as it is a monomer having a carboxy group. For example, (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, etc. can be mentioned. Also, acid anhydrides of these carboxyl group-containing monomers (for example, acid anhydride group-containing monomers such as maleic anhydride, itaconic anhydride, etc.) can also be used as the carboxy group-containing monomer. Among these, acrylic acid, methacrylic acid, and itaconic acid can be preferably used. Octopus The carboxy group-containing monomer (AII) may be used alone or in combination of two or more.

[0027] By using acrylic copolymer (A) containing units of carboxy group-containing monomer (AII) and using it in combination with epoxy curing agent (C-1), the adhesiveness and meltability of the thermosetting acrylic resin composition can be improved. Also, when the Tg of acrylic copolymer (A) is low (especially when it is -35°C or lower), ultrafine bubbles are likely to be generated during curing under heating and pressure. However, the cross-linking reaction of acrylic copolymer (A) by epoxy curing agent (C-1) makes the resin component less likely to melt, and it becomes possible to suppress ultrafine bubbles. The content rate of the unit of the carboxy group-containing monomer (AII) in the acrylic copolymer (A) is preferably 1% by mass or more, more preferably 2% by mass or more, and still more preferably 3% by mass or more from the viewpoint of sufficiently performing the crosslinking reaction. Although there is no particular limitation on the upper limit value of the content, it is preferably 20% by mass or less, more preferably 15% by mass or less, and still more preferably 10% by mass or less. Further, the content rate of the unit of the carboxy group-containing monomer (AII) in the acrylic copolymer (A) is preferably set so that the acrylic copolymer (A) has the above-described acid value.

[0028] The acrylic copolymer (A) may contain units of other monomers (copolymerizable monomers) copolymerizable with (meth)acrylic acid alkyl ester (AI) and carboxy group-containing monomer (AII) as long as the desired effects are not impaired. Examples of such copolymerizable monomers include (meth)acrylic acid methyl; (meth)acrylic acid pentadecyl, (meth)acrylic acid hexadecyl, (meth)acrylic acid heptadecyl, (meth)acrylic acid octadecyl, (meth)acrylic acid nonadecyl, (meth)acrylic acid eicosyl, etc. of (meth)acrylic acid C 15-20Alkyl esters; non-aromatic ring-containing (meth)acrylic esters such as cycloalkyl (meth)acrylates and isobornyl (meth)acrylate; aromatic ring-containing (meth)acrylic esters such as aryl (meth)acrylates, aryloxyalkyl (meth)acrylates, and arylalkyl (meth)acrylates; epoxy group-containing acrylic monomers such as glycidyl (meth)acrylate and methyl glycidyl (meth)acrylate; vinyl ester monomers such as vinyl acetate and vinyl propionate; styrene monomers such as styrene and α-methylstyrene; hydroxy group-containing monomers such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate; alkoxyalkyl (meth)acrylate monomers such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; aminoalkyl (meth)acrylate monomers such as aminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, and t-butylaminoethyl (meth)acrylate; (N-substituted) amide monomers such as (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, and N-hydroxy(meth)acrylamide; olefin monomers such as ethylene, propylene, isoprene, and butadiene; vinyl ether monomers such as methyl vinyl ether, etc. can be mentioned.

[0029] Also, as copolymerizable monomers, polyfunctional monomers such as hexanediol di(meth)acrylate, butanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, glycerin di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, epoxy acrylate, polyester acrylate, urethane acrylate, and divinylbenzene can also be used.

[0030] The acrylic copolymer (A) can be prepared, for example, by a solution polymerization method, an emulsion polymerization method, a bulk polymerization method, a polymerization method by ultraviolet irradiation, or the like.

[0031] The polymerization initiator, chain transfer agent, solvent, etc. used in the polymerization of the acrylic copolymer (A) are not particularly limited.

[0032] As the polymerization initiator, any initiator that can be usually used in the production of general acrylic copolymers can be used for the polymerization of the acrylic copolymer (A). Examples of the polymerization initiator used for the polymerization of the acrylic copolymer (A) include azo-based polymerization initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis(2,4,4-trimethylpentane), dimethyl-2,2'-azobis(2-methylpropionate); peroxide-based polymerization initiators such as benzoyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, t-butyl peroxybenzoate, dicumyl peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclododecane, etc. The polymerization initiator can be used alone or in combination of two or more. The amount of the polymerization initiator used can be appropriately selected from the range of the usual amounts used.

[0033] As the chain transfer agent, any agent that can be normally used in the production of general acrylic copolymers can be used for the polymerization of the acrylic copolymer (A). Examples of the chain transfer agent used for the polymerization of the acrylic copolymer (A) include 2-mercaptoethanol, lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-ethylhexyl thioglycolate, 2,3-dimethylcapto-1-propanol, dodecanethiol, α-methylstyrene dimer, and the like. The chain transfer agent can be used alone or in combination of two or more. The amount of the chain transfer agent used can be appropriately selected from the range of normal usage amounts.

[0034] In solution polymerization, a solvent, a monomer, a polymerization initiator, and, if necessary, a chain transfer agent are mixed, and polymerization can be carried out by heating with stirring or / and irradiating active energy rays such as ultraviolet rays in a state where the monomer is dissolved in the solvent. In solution polymerization, various common solvents can be used. Such solvents include esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; and organic solvents such as ketones such as methyl ethyl ketone and methyl isobutyl ketone. The solvents can be used alone or in combination of two or more.

[0035] In emulsion polymerization, polymerization is usually carried out in a state where the monomer is dispersed in water in the presence of a surfactant (emulsifier). By adding a polymerization initiator (in the presence of a chain transfer agent if necessary), the polymerization reaction can be started at room temperature or under heating. The type and amount of the surfactant used are not particularly limited. As the surfactant, known anionic surfactants, nonionic surfactants, cationic surfactants, etc. can be used. An anionic or nonionic surfactant is preferred, and a surfactant having a reactive functional group (typically a radically polymerizable functional group) may be used. The surfactants can be used alone or in combination of two or more.

[0036] In bulk polymerization, a monomer, a polymerization initiator, and, if necessary, a chain transfer agent are mixed substantially without using a solvent, and polymerization can be carried out by self-heating or heating under stirring, or / and by irradiating active energy rays such as ultraviolet rays.

[0037] The weight average molecular weight (Mw) of the acrylic copolymer (A) is not particularly limited as long as the desired properties of the thermosetting acrylic resin composition of the present invention can be obtained. For example, an acrylic copolymer (A) having a weight average molecular weight of 100,000 or more and 1,400,000 or less, preferably 200,000 or more and 1,300,000 or less can be used. The weight average molecular weight of the acrylic copolymer (A) can be controlled by the type and amount of the polymerization initiator and chain transfer agent, the temperature and time during polymerization, the monomer concentration, the supply rate of the monomer, etc. Incidentally, the weight average molecular weight of the acrylic copolymer (A) can be measured by gel permeation chromatography (GPC) and obtained as a molecular weight in terms of standard polystyrene.

[0038] <Phenolic resin (B)> The thermosetting acrylic resin composition of the present invention contains a phenolic resin (B). The phenolic resin (B) is a curing component that contributes to the thermosetting property of the thermosetting acrylic resin composition. The phenolic resin (B) may contain a novolak type phenolic resin (B-1) capable of reacting with an amine-based curing agent (C-2), or a self-crosslinking type phenolic resin (B-2) that self-crosslinks and cures by heating, and the type thereof is not particularly limited. By the crosslinking reaction of this phenolic resin (B) with the amine-based curing agent (C-2), or by the self-crosslinking of the self-crosslinking type phenolic resin (B-2), properties such as the adhesiveness and heat resistance of the thermosetting acrylic resin composition are improved.

[0039] Specific examples of the novolak type phenol resin (B-1) include phenol novolak resin, cresol novolak resin, t-butylphenol novolak resin, nonylphenol novolak resin, dicyclopentadiene cresol novolak resin, dicyclopentadiene phenol novolak resin, xylylene-modified phenol novolak resin, naphthol novolak resin, tris-phenol novolak resin, tetrakis-phenol novolak resin, bisphenol F novolak resin, bisphenol A novolak resin, and phenol-modified xylene resin. Examples of the self-crosslinking type phenol resin (B-2) include resol type phenol resins such as liquid resol type phenol resin, solid resol type phenol resin, dimethylene ether resol type phenol resin, and methylol resol type phenol resin. The resol type phenol resin used in the present invention is not particularly limited, and can be appropriately selected from conventionally known resol type phenol resins. For example, phenols such as phenol, p-cresol, xylenol, p-alkylphenol, p-phenylphenol, resorcinol or their derivatives, and aldehydes (such as formaldehyde, acetaldehyde) are reacted in the presence of a basic catalyst (such as sodium hydroxide, potassium hydroxide, calcium hydroxide, etc.), and then, if necessary, a neutralization treatment and / or a reduced pressure dehydration treatment are performed to prepare a resol type phenol resin that can be used. From the viewpoint of comprehensive evaluation, the novolak type phenol resin (B-1) is preferred as the phenol resin (B). Also, from the viewpoint of reactivity, the self-crosslinking type phenol resin (B-2) is preferred. By using (B-1) or (B-2), for example, when bonding FPCs together, both sufficient bonding strength and suppression of ultrafine bubbles can be achieved. The phenol resin (B) may be used alone or in combination of two or more.

[0040] The content of the phenolic resin (B) is 2 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer (A) from the viewpoint of improving properties such as thermosetting property, adhesiveness, heat resistance, etc. If the content of the phenolic resin (B) is too small, a sufficient addition effect cannot be obtained. If the content of the phenolic resin (B) is too large, curing may proceed before sufficient adhesiveness is exhibited, and there is a possibility that sufficient adhesive strength cannot be obtained. The content of the phenolic resin (B) is within the above numerical range whether it is the use of the novolac type phenolic resin (B-1) alone, the use of the self-crosslinking type phenolic resin (B-2) alone, or the combined use of (B-1) and (B-2).

[0041] <Epoxy curing agent (C-1)> The epoxy curing agent (C-1) used in the present invention is a component that reacts with the carboxyl group of the acrylic copolymer (A-1) to form a crosslinked structure, and examples thereof include compounds having two or more epoxy groups in the molecule. Specific examples include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidylaniline, diaminoglycidylamine, N,N,N',N'-tetraglycidyl-m-xylenediamine, 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane. As commercially available products, for example, E-5CM (product name) (1,3-bis(N,N-diglycidylaminomethyl)cyclohexane) manufactured by Soken Chemical & Engineering Co., Ltd., E-5XM (product name) manufactured by Soken Chemical & Engineering Co., Ltd., TEDRAD-C (product name) manufactured by Mitsubishi Gas Chemical Company, Inc., TEDRAD-X (product name) manufactured by Mitsubishi Gas Chemical Company, Inc.

[0042] The content of the epoxy curing agent (C-1) is 0.000002 parts by mass or more and 0.4 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer (A-1) having a Tg of -35°C or lower, and preferably 0.0000025 parts by mass or more and 0.38 parts by mass or less. When the thermosetting acrylic resin composition does not contain the epoxy curing agent (C-1) or contains it in a small amount, the crosslinking of the acrylic copolymer (A-1) is not sufficiently carried out, so the resin component tends to melt easily. Therefore, ultrafine bubbles tend to be generated during curing under heating and pressure. Conversely, when the content is too high, the crosslinking is excessively carried out, so the adhesive strength tends to decrease.

[0043] <amine curing agent (C-2)> The amine curing agent (C-2) used in the present invention is a component that reacts with the carboxyl groups in the phenol resin (B) and the acrylic copolymer (A) to form a crosslinked structure. Specific examples include chain aliphatic amines (such as diethylenetriamine, triethylenetetramine, hexamethylenediamine, N,N-dimethylpropylamine, benzyldimethylamine, 2-(dimethylamino)phenol, 2,4,6-tris(dimethylaminomethyl)phenol, m-xylenediamine, etc.), cyclic aliphatic amines (such as N-aminoethylpiperazine, bis(3-methyl-4-aminocyclohexyl)methane, bis(4-aminocyclohexyl)methane, menthendiamine, isophoronediamine, 1,3-bis(aminomethyl)cyclohexane, etc.), heterocyclic amines (such as hexamethylenetetramine, piperazine, N,N-dimethylpiperazine, triethylenediamine, melamine, guanamine, etc.), aromatic amines (such as metaphenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylsulfone, etc.). The amine curing agent (C-2) may be used alone or in combination of two or more. Among them, hexamethylenetetramine is preferable from the viewpoint of adhesive reliability and the like.

[0044] When the phenol resin (B) of the thermosetting acrylic resin composition of the present invention is a novolac-type phenol resin (B-1), it contains an amine curing agent (C-2). The content of the amine-based curing agent (C-2) is preferably less than 1 part by mass, more preferably 0.002 parts by mass or more and 0.9 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer (A). If the thermosetting acrylic resin composition does not contain the amine-based curing agent (C-2) or contains too little of it, crosslinking is not sufficiently carried out, so the resin component tends to melt easily, and therefore, ultrafine bubbles tend to be generated easily. Conversely, if the content is too high, crosslinking is excessively carried out, so the adhesive strength tends to decrease. When the phenol resin (B) of the thermosetting acrylic resin composition of the present invention is a self-crosslinking type phenol resin (B-2), it is not necessarily required to contain the amine-based curing agent (C-2), but it may contain it. When it is contained for the promotion of crosslinking, it can be set within the above content range.

[0045] <Other thermosetting resin (D)> The thermosetting acrylic resin composition of the present invention may contain a thermosetting resin (D) other than the acrylic copolymer (A) and the phenol resin (B). The thermosetting resin (D) may be a thermosetting resin capable of undergoing a curing reaction with the amine-based curing agent (C-2) or a self-crosslinking type thermosetting resin that self-crosslinks and cures by heating, and its type is not particularly limited. When this thermosetting resin (D) undergoes a curing reaction with the amine-based curing agent (C-2) or when the thermosetting resin (D) is of the self-crosslinking type and self-crosslinks, a crosslinked structure is formed, and properties such as adhesiveness and heat resistance can be improved. Examples of such thermosetting resins include epoxy resins, urea resins, cyanate resins, maleimide resins, acetal resins, phenol aralkyl resins, poly-p-vinylphenol resins, and polyoxystyrenes such as polyparaoxystyrene.

[0046] <Filler (E)> The thermosetting acrylic resin composition of the present invention may further contain a filler (E). By containing the filler (E), it becomes easier to adjust physical properties such as the elastic modulus, dimensional stability, yield point strength, and elongation at break of the thermosetting acrylic resin composition. Representative examples of the filler (E) include inorganic fillers and organic fillers. Representative shapes of the filler include spherical, needle-like, flaky, and the like. One type of filler may be selected and contained, or two or more types of fillers may be contained.

[0047] Examples of the constituent materials of the inorganic filler include crystalline silica, amorphous silica, wollastonite, talc, aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, calcium oxide, magnesium oxide, aluminum oxide, aluminum nitride, aluminum borate whisker, and boron nitride. Other constituent materials of the inorganic filler include, for example, simple metals such as aluminum, gold, silver, copper, and nickel, as well as alloys, amorphous carbon, graphite, and the like. On the other hand, examples of the constituent materials of the organic filler include polymethyl methacrylate (PMMA), polyimide, polyamideimide, polyetheretherketone, polyetherimide, and polyesterimide.

[0048] <Bio-based carbon content> From the viewpoints of saving petroleum resources and reducing carbon dioxide emissions, the thermosetting acrylic resin composition of the present invention preferably has a bio-based carbon content of 20% by mass or more, more preferably 25% by mass or more, and still more preferably 50% by mass or more. The upper limit of this content is 100% by mass. In addition, while carbon derived from living organisms contains a certain proportion of the radioactive isotope (C14), carbon derived from petroleum contains almost no C14. Therefore, the content rate of the above-mentioned carbon derived from living organisms can be calculated by measuring the concentration of C14 contained in the thermosetting acrylic resin composition. Specifically, it can be measured in accordance with ASTM D6866-20 or the ISO international standard ISO16620-2.

[0049] (Adhesive sheet or adhesive tape) The adhesive sheet or adhesive tape according to an embodiment of the present invention is provided with an adhesive layer formed of the thermosetting acrylic resin composition of the above-described embodiment. As one aspect of the adhesive tape or adhesive tape, it can be provided as a so-called "baseless type" consisting only of an adhesive layer. The baseless type adhesive sheet or adhesive tape can be formed, for example, by applying a thermosetting acrylic resin composition on a support such as release paper and then drying it. Furthermore, the adhesive layer can also be in a mode provided with a release liner described later. In this mode, the release liner is arranged so as to contact one or both of the two main surfaces in a form in which the adhesive layer has two main surfaces.

[0050] Also, the adhesive sheet or adhesive tape according to an embodiment of the present invention can be in a mode in which an adhesive layer formed of the thermosetting acrylic resin composition of the above-described embodiment is provided on at least one surface of the base material.

[0051] The adhesive layer formed of the thermosetting acrylic resin composition may be formed on only one surface of the base material, or may be formed on both surfaces of the base material. Also, the adhesive layer may be formed in direct contact with the base material, or an easy-adhesion treatment layer may be provided between the base material and the adhesive layer. The easy-adhesion treatment layer can be formed by performing an easy-adhesion treatment on the surface where the adhesive layer is provided. Examples of the easy-adhesion treatment include primer treatment, corona treatment, etching treatment, plasma treatment, sandblasting treatment, etc., and one kind or a combination of two or more kinds thereof may be used for the treatment.

[0052] The formation of the adhesive layer can be carried out by applying a composition material for layer formation containing a thermosetting acrylic resin composition and a solvent onto a substrate and evaporating the solvent by heating, or further causing a crosslinking reaction in the applied layer. For the formation of the applied layer, general coating devices such as a roll coater, a die coater, and a lip coater can be used, for example. When heating is performed after coating, the solvent in the layer formation material can be removed together with the crosslinking reaction by heating. The adhesive layer can also be provided on the substrate by transfer. In that case, in order to improve the adhesion between the substrate and the adhesive layer, it is preferable to laminate using a heated roll.

[0053] The thickness of the adhesive layer after drying can be set, for example, to 200 μm or less, preferably in the range of 1 μm or more and 150 μm or less, and more preferably 1.5 μm or more and 100 μm or less. The size of the adhesive sheet and the adhesive tape in the planar direction can be appropriately set according to the size of the substrate used during production in the planar direction, or can be cut after production and processed into a desired size, and can also be made into a wound body. In this specification, a wide sheet-like material (and its wound body) is referred to as an adhesive sheet, and a long and narrow tape-like material (and its wound body) is called an adhesive tape.

[0054] FIG. 1 shows a schematic cross-sectional view of a single-sided adhesive sheet or a single-sided adhesive tape having an adhesive layer 12 provided on one side of a substrate 11. FIG. 2 shows a schematic cross-sectional view of a double-sided adhesive sheet or a double-sided adhesive tape having adhesive layers 22 and 23 provided on both sides of a substrate 21. In the single-sided adhesive sheet or the single-sided adhesive tape, the substrate 11 may have a laminated structure, and it is preferable that the layer (outermost layer) on the surface 11B side is a resin layer. In a single-sided adhesive sheet or single-sided adhesive tape, on the surface 11A of the base material 11, if necessary, surface treatment such as an easy-adhesion treatment, for example, corona discharge treatment, may be performed, or an undercoat layer such as an easy-adhesion treatment layer may be provided. By performing the easy-adhesion treatment, the adhesion of the adhesive layer 12 to the base material 11 can be enhanced. On the surface 11B of the base material 11, if necessary, by providing a release agent treatment, for example, a release layer, when the single-sided adhesive sheet or single-sided adhesive tape is wound into a roll, the adhesive composition of the adhesive layer 12 is prevented from adhering to the surface 11B of the base material 11, and the ease of unwinding (pulling out) can be maintained. A release liner described later can be provided on the surface of the adhesive layer 12 (the surface opposite to the base material 11 side).

[0055] In the double-sided adhesive sheet or double-sided adhesive tape shown in FIG. 2, on both surfaces (21A and 21B) or either one of the surfaces of the base material 21, surface treatment such as an easy-adhesion treatment, for example, corona discharge treatment, may be performed, or an undercoat layer such as an easy-adhesion treatment layer may be provided. By performing the easy-adhesion treatment, the adhesion between the adhesive layer 22 or the adhesive layer 23 and the base material 21 can be enhanced. A release liner described later can be provided on the surface of the adhesive layer 22 or / and the adhesive layer 23 (the surface opposite to the base material 21 side).

[0056] The base material is not particularly limited as long as it can function as a support for the adhesive layer, and films, non-woven fabrics, foams, fabrics, papers, and combinations thereof, which are used in general adhesive films or adhesive tapes, can be used. Among these, a film that can easily achieve thickness uniformity is preferred, and particularly, a resin film having heat resistance required in the usage environment is preferred. Specific examples thereof include, for example, polyimide resins such as polyimide (PI) and polyamideimide (PAI), polyamide resins such as polyamide (PA) and polyetheramide, polyether ketone resins such as polyether ketone and polyether ether ketone (PEEK), polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyphenylene sulfide (PPS), polyether sulfone (PES), and resin films such as fluororesins (for example, polytetrafluoroethylene (PTFE), ethylene-polytetrafluoroethylene copolymer (ETFE), perfluoroalkoxy alkane (PFA)). These films can be used as single-layer or multilayer films of two or more layers. The multilayer film may include one or more combinations of a plurality of layers made of different materials. As the heat-resistant resin film, a polyimide film having excellent dimensional stability at high temperatures is particularly preferred.

[0057] The thickness of the base material is not particularly limited, but preferably it can be set to a thickness of 1 μm or more and 200 μm or less, more preferably 2 μm or more and 150 μm or less, and particularly preferably 2.5 μm or more and 125 μm or less.

[0058] An easy adhesion treatment may be applied as needed to the surface of the base material on which the adhesive layer is provided. Examples of the easy adhesion treatment include, for example, primer treatment, corona treatment, etching treatment, plasma treatment, sandblasting treatment, and the like. One type or a combination of two or more types thereof may be used for the treatment.

[0059] The base material may be subjected to surface treatment such as antistatic treatment as required. Examples of the antistatic treatment include treatment with an antistatic agent such as a cationic surfactant, an anionic surfactant, or a nonionic surfactant. Further, the base material may be subjected to a coloring treatment such as printing or kneading as required.

[0060] The base material preferably has a content of bio-derived carbon (bio-based carbon content) of 25% by mass or more, more preferably 40% by mass or more, and still more preferably 50% by mass or more. The upper limit is 100% by mass.

[0061] When the adhesive layer is formed only on one surface of the base material and no release liner is provided, it is preferable that at least the outermost layer on the side opposite to the side where the adhesive layer of the base material is provided is made of a resin material. Further, it is preferable that a release agent treatment is applied to the surface of the base material or the surface of the outermost layer (the side where the adhesive layer is not provided). By applying the release agent treatment, it becomes possible to easily peel off and use the adhesive sheet wound in a roll shape. During production, after winding the adhesive sheet formed by applying the adhesive composition to the base material in a roll shape, the adhesive sheet can be peeled off (unrolled), processed, and rolled up again. As the release agent, an acrylic resin, a fluorine-based resin, an alkyd resin, a mixture of an alkyl resin and an amino resin, a polyvinyl carbamate-based resin, or a silicone-based release agent is preferable.

[0062] (Release liner) As the release liner, ordinary release paper, release film, etc. can be used. The release liner functions as a protective material for the adhesive layer and is peeled off when attached to the adherend. As the release liner, a base material having a release layer, for example, a resin film (e.g., a PET film) or paper or cloth surface-treated with a release agent such as a silicone-based, long-chain alkyl-based, or fluorine-based release agent can be used. Further, a low-adhesion film made of a nonpolar polymer such as a fluorine-based resin (e.g., polytetrafluoroethylene) or an olefin-based resin (e.g., polyethylene, polypropylene, etc.) may be used.

[0063] (Method for manufacturing an adhesive sheet or an adhesive tape) The method for manufacturing the adhesive sheet or the adhesive tape of the present invention is not particularly limited, but it can be manufactured by forming an adhesive layer on at least one surface of a base material. As a general method for forming the adhesive layer, there are a coating method in which the adhesive layer is directly coated on the base material as described below, or a transfer method in which the adhesive layer is formed on the surface of a release liner and the base material is bonded to the adhesive layer side of the release liner on which the adhesive layer is formed.

[0064] Examples of the method for forming the adhesive layer include a method of coating an adhesive composition containing the above-described predetermined components on the surface of a base material (or a release liner). In order to adjust the viscosity of the adhesive composition during coating, a solvent may be added. Specific examples of the solvent include aromatic solvents such as toluene and xylene; aliphatic solvents such as hexane, octane, and isoparaffin; ketone solvents such as methyl ethyl ketone and methyl isobutyl ketone; ester solvents such as ethyl acetate and isobutyl acetate; and ether solvents such as diisopropyl ether and 1,4-dioxane. Examples of the mixing method during the preparation of the adhesive composition include a mechanical kneading and dispersing method and a solvent dispersing method. As the apparatus used for this dispersion, a mixer / kneader, a ball mill, a planetary mixer, a paint conditioner, a three-roll mill, etc. can be used. Two or more of these apparatuses may be used in combination. Examples of the method for coating the adhesive composition on the surface of the base material (or the release liner) include a method using a roll coater or a reverse coater. By the above coating method or the like, the adhesive composition can be coated on the surface of the base material (or the release liner) in one layer or two or more layers, and by heating as necessary, an adhesive layer can be formed on the surface of the base material (or the release liner).

Examples

[0065] Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited to these examples.

[0066] The constituent materials of the prepared curable acrylic resin composition are as follows. (Acrylic copolymer (A)) (A-1) Manufactured by Toray Coating Tex Co., Ltd., product name: R-2000 (containing carboxyl group) (A-2) Manufactured by Toray Coating Tex Co., Ltd., product name: R-6000 (non-containing carboxyl group) (A-2) Manufactured by Toray Coating Tex Co., Ltd., product name: R-9000 (containing carboxyl group) (A-2) Manufactured by Nagase ChemteX Corporation, product name: SG-70L (containing carboxyl group) (A-2) Manufactured by Nagase ChemteX Corporation, product name: WS-023 (containing carboxyl group) (A-2) Manufactured by Nagase ChemteX Corporation, product name: SG-708-6 (containing carboxyl group) (Phenolic resin (B)) (B-1) Manufactured by Arakawa Chemical Industries, Ltd., product name: Tamanol 759 (novolac type) (B-2) Manufactured by Aica Industries Co., Ltd., product names: CKM-908 (resole type), CKS-3898 (resole type) (Epoxy curing agent (C-1)) Manufactured by Soken Chemical & Engineering Co., Ltd., product name: E-5CM (1,3-bis(N,N-diglycidylaminomethyl)cyclohexane) (Amine curing agent (C-2)) Manufactured by Ouchi Shinsei Chemical Industry Co., Ltd., product name: Nocceler H (hexamethylenetetramine)

[0067] (Production of thermosetting acrylic resin composition and adhesive sheet) As shown in Table 1 and Table 2, based on 100 parts by mass of the solid content of the acrylic copolymer (A) (A-1 or A-2), the phenolic resin (B) (B-1 or B-2), the epoxy curing agent (C-1), the amine curing agent (C-2), and ethyl acetate (diluting solvent) were mixed at a predetermined content ratio (by mass) to obtain a thermosetting acrylic resin composition.

[0068] This thermosetting acrylic resin composition was applied to a PET release liner. Subsequently, it was heated at 100 °C to evaporate the solvent, or further a crosslinking reaction was caused in the coating layer to form an adhesive layer. The PET release liner was laminated on the adhesive layer side, and the crosslinking reaction was promoted at 40 °C for 3 days to obtain the target adhesive layer (thickness 15 μm).

[0069] Next, one of the PET release liners on both sides of the adhesive layer was peeled off and removed. On the side of the adhesive layer from which the PET release liner was peeled off and removed, using a desktop laminator, a polyimide film (manufactured by Toray DuPont, product name: Kapton (registered trademark) 100H) was laminated at a temperature of 100 °C to obtain an adhesive sheet having an adhesive layer provided on one side of the polyimide film.

[0070] <Measurement and Evaluation of Adhesion Strength> The obtained adhesive sheet was cut into a width of 20 mm and a length of 125 mm to prepare a sample for evaluation. Then, the sample from which the PET release liner was peeled off and removed was bonded to a copper plate (manufactured by Partec Co., Ltd., product name: C1100P) having a thickness of 0.7 mm, a width of 50 mm, and a length of 125 mm. Next, assuming the hot press during the actual use of the adhesive sheet, a stainless steel (SUS304) plate having a thickness of 2.0 mm, a width of 50 mm, and a length of 125 mm was overlaid on the adhesive sheet side, a 2 kg weight was placed on the stainless steel plate, and it was heat-cured for 1 hour in a dryer set at 180 °C. Next, after allowing it to cool at 23 °C for 1 hour or more, using a tensile testing machine (manufactured by Toyo Seiki Seisakusho Co., Ltd., product name: Strograph E-L), the force (adhesion) required to peel the adhesive sheet from the copper plate was measured under the conditions of an environment at 23 °C, a peeling speed of 300 mm / min, and a peeling angle of 180 °.

[0071] The adhesion when heat-cured was judged according to the following criteria. The results are shown in Table 1. A: The maximum value of the adhesion is 10 N / 20 mm or more (very good) B: The maximum value of the adhesion is 6 N / 20 mm or more and less than 10 N / 20 mm (good) C: The maximum value of the adhesion is less than 6 N / 20 mm (poor)

[0072] <Evaluation Test of Ultrafine Bubble Generation in Adhesive Layer> The prepared adhesive sheet was cut into 10 mm squares and bonded to a glass plate (manufactured by AGC Inc., product name: Float Glass) with a thickness of 2.0 mm, a width of 50 mm, and a length of 125 mm to prepare test pieces. As shown in Fig. 3, the prepared test piece was pressed for 90 seconds using a heated press machine so that the execution temperature was 130°C and the pressure applied to the entire test piece was 2.0 MPa. At the time of this pressing, in order to apply pressure uniformly to the test piece, a silicone rubber sheet (manufactured by Nitta Gomu Co., Ltd., product name: IS-825, hardness 50°) cut into 10 mm squares with a thickness of 2 mm was placed on the test piece, and the entire test piece was pressed from above. In Fig. 3, reference numeral 30 indicates the glass plate, reference numeral 31 indicates the base material (polyimide film), and reference numeral 32 indicates the adhesive layer (thermosetting acrylic resin composition).

[0073] Next, after allowing to cool at 23°C for 1 hour or more, the maximum lengths (L1, L2, L3, L4) and maximum widths (W1, W2, W3, W4) of the ultrafine bubbles observed at approximately the center of each of the four sides of the test piece were measured using a digital microscope (manufactured by Keyence Corporation, product name: VHX-8000). Fig. 4 shows a schematic plan view of the test piece at the time of this measurement. In Fig. 4, reference numeral 30 indicates the glass plate, reference numeral 31 indicates the base material (polyimide film), and reference numeral 32 indicates the adhesive layer (thermosetting acrylic resin composition). The lengths of the bubbles having the maximum length among the ultrafine bubbles observed in each of the first to fourth observation portions are defined as L1, L2, L3, and L4, respectively, and the widths of the bubbles having the maximum width among the ultrafine bubbles observed in each of the first to fourth observation portions are defined as W1, W2, W3, and W4, respectively. The lengths (L1, L2, L3, L4) are the lengths in the direction perpendicular to the end side (boundary line) of the base material from the position of the end side of the base material (the length of the bubble on the base material side). The widths (W1, W2, W3, W4) are the lengths in the direction along the end side (boundary line) of the base material. As the range of the first to fourth observation portions, considering the variation in the generation of ultrafine bubbles, a range of about 1 to 20% of the length of the end side of the base material (including the central portion of the end side) was observed at 200 times magnification. The area index (S), which is an index of the amount of ultrafine bubbles generated, was calculated from the measured values (unit: μm) of these lengths (L1, L2, L3, L4) and widths (W1, W2, W3, W4) according to the following formula, and an evaluation was performed based on the calculation results. The results are shown in Tables 1 and 2. S=L total × W total L total =L1+L2+L3+L4 W total =W1+W2+W3+W4

[0074] The evaluation of the amount of generated ultrafine bubbles was judged based on the area index (S) according to the following criteria. A:S is 10000μm 2 Less than (Very Good) B:S is 10000μm 2 More than 15000μm 2 Less than (good) C:S is 15000μm 2 or more (defect)

[0075] 5 and 6 show digital microscope images of the evaluation test results of the generation of ultrafine bubbles. FIG. 5 shows the evaluation test results of Comparative Example 4 not having the configuration of the present invention, and FIG. 6 shows the evaluation test results of Example 2 according to the present invention. Both images are enlarged images of the vicinity of the edge (boundary) of the substrate (polyimide film) of the adhesive sheet. As is clear from FIG. 5, in the comparative example not having the configuration of the present invention, a large number of ultrafine bubbles are generated near the edge (boundary) of the substrate (polyimide film) of the adhesive sheet (i.e., near the outer peripheral edge of the adhesive sheet). On the other hand, as is clear from FIG. 6, it can be seen that the generation of ultrafine bubbles is suppressed in the examples according to the present invention.

[0076] The overall performance of the adhesive sheet (adhesive strength and generation of ultrafine bubbles) was evaluated according to the following criteria. A: All rated A (very good). B: There is a B rating, but no C rating (good). C: At least one C rating and defective.

[0077]

Table 1

[0078]

Table 2

[0079] As is clear from comparing Example 1 and 2 with Comparative Example 1, it can be seen that when the epoxy curing agent (C-1) is not contained, ultrafine bubbles are likely to be generated, and the generation of ultrafine bubbles can be suppressed by containing the epoxy curing agent (C-1). As is clear from comparing Example 1 and 2 with Comparative Example 2, it can be seen that when the content of the epoxy curing agent (C-1) is too high, the adhesive strength decreases, and sufficient adhesive strength can be obtained by containing a predetermined amount of the epoxy curing agent (C-1).

[0080] As is clear from comparing Example 1 and 2 with Comparative Example 7, it can be seen that when the acrylic copolymer (A) does not have a carboxyl group (when the acid value is 0), ultrafine bubbles are likely to be generated and the adhesive strength does not increase sufficiently, and by using the acrylic copolymer (A) having a carboxyl group, the generation of ultrafine bubbles can be suppressed and sufficient adhesive strength can be obtained.

[0081] As is clear from comparing Example 3 and 4 with Comparative Example 3, it can be seen that when the content of the phenol resin (B) is low, ultrafine bubbles are likely to be generated, and the generation of ultrafine bubbles can be suppressed by sufficiently containing the phenol resin (B). As is clear from comparing Example 3 and 4 with Comparative Example 5, it can be seen that when the content of the phenol resin (B) is too high, the adhesive strength decreases, and sufficient adhesive strength can be obtained by containing a predetermined amount of the phenol resin (B).

[0082] As is clear from comparing Example 5 with Comparative Examples 4 and 6, when the phenolic resin (B) is a novolak-type phenolic resin (B-1), if the content of the amine-based curing agent (C-2) is too small or 0, ultrafine bubbles are likely to occur, and it can be seen that by sufficiently containing the amine-based curing agent (C-2), the generation of ultrafine bubbles can be suppressed. As is clear from comparing Example 5 with Comparative Examples 8 and 9, even if the content of the amine-based curing agent (C-2) is increased, ultrafine bubbles are likely to occur if the epoxy-based curing agent (C-1) is not contained, and it can be seen that by containing a predetermined amount of the amine-based curing agent (C-2) and the epoxy-based curing agent (C-1), the generation of ultrafine bubbles can be effectively suppressed. Also, as is clear from comparing Comparative Example 1 with Comparative Examples 8 and 9, it can be seen that if the content of the amine-based curing agent (C-2) is too high, the adhesive strength tends to decrease.

[0083] As is clear from comparing Examples 6, 7, 8, and 9 with Comparative Example 1, when the acrylic copolymer (A) is an acrylic copolymer (A-1) having a Tg of -35°C or lower, it can be seen that ultrafine bubbles are likely to occur if the epoxy-based curing agent (C-1) is not contained. In this case, it can be seen that by containing a predetermined amount of the epoxy-based curing agent (C-1) as in Examples 1 and 2, the generation of ultrafine bubbles can be suppressed. On the other hand, when using an acrylic copolymer (A-2) having a Tg higher than -35°C as in Examples 6, 7, 8, and 9, it can be seen that the generation of ultrafine bubbles can be suppressed even without containing the epoxy-based curing agent (C-1).

[0084] As in Examples 10 and 11, when the phenolic resin (B) is a self-crosslinking type phenolic resin (B-2) (resole type), it can be seen that the generation of ultrafine bubbles can be suppressed and sufficient adhesive strength can also be obtained even without containing the amine-based curing agent (C-2). As is clear from the comparison between Examples 10 and 11 and Comparative Example 10, even when the phenolic resin (B) is a self-crosslinking phenolic resin (B-2) (resole type), when the acrylic copolymer (A) is an acrylic copolymer (A-1) having a Tg of -35°C or lower, ultrafine bubbles are likely to occur unless an epoxy curing agent (C-1) is contained, and it can be seen that the generation of ultrafine bubbles can be suppressed by containing the epoxy curing agent (C-1). As is clear from the comparison between Examples 10 and 11 and Comparative Example 11, even when the phenolic resin (B) is a self-crosslinking phenolic resin (B-2) (resole type), when the content of the phenolic resin (B) is low, ultrafine bubbles are likely to occur, and it can be seen that the generation of ultrafine bubbles can be suppressed by sufficiently containing the phenolic resin (B).

Industrial Applicability

[0085] When the thermosetting acrylic resin composition of the present invention, the adhesive sheet, and the adhesive tape using the same are cured under heating and pressure, it is possible to achieve both suppression of ultrafine bubbles and excellent adhesiveness. Therefore, it is useful for all applications in fields where such characteristics are required. For example, it is useful for applications such as portable electronic devices such as smartphones, tablets, car navigation systems, cameras, audio-visual equipment, game machines, and information devices, and vehicle applications. Specifically, for example, in electronic devices, it is very useful for joining FPCs within the electronic device. Also, in vehicle applications, for example, it can be used for fixing automobile mechanical parts, automobile exterior parts, or automobile interior parts.

Explanation of Symbols

[0086] 11 Substrate 12 Adhesive layer 21 Substrate 22 Adhesive layer 23 Adhesive layer 30 Glass plate 31 Substrate (polyimide film) 32 Adhesive layer (thermosetting acrylic resin composition)

Claims

1. A thermosetting acrylic resin composition containing an acrylic copolymer (A) having a carboxy group and a phenol resin (B), wherein the acrylic copolymer (A) is an acrylic copolymer (A-1) having a glass transition temperature of -35°C or lower, and further contains an epoxy curing agent (C-1), and the content of the epoxy curing agent (C-1) is 0.000002 parts by mass or more and 0.4 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer (A-1), when the phenol resin (B) contains a novolac-type phenol resin (B-1), the content of the novolac-type phenol resin (B-1) is 2 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer (A), and further contains an amine curing agent (C-2), and the content of the amine curing agent (C-2) is 0.002 parts by mass or more and 0.9 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer (A), when the phenol resin (B) does not contain the novolac-type phenol resin (B-1), it contains a self-crosslinking type phenol resin (B-2), and the content of the self-crosslinking type phenol resin (B-2) is 2 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer (A), A thermosetting acrylic resin composition, wherein the total content of the phenol resin (B) is 2 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer (A).

2. The thermosetting acrylic resin composition according to Claim 1, wherein the phenol resin (B) contains the novolac-type phenol resin (B-1).

3. The thermosetting acrylic resin composition according to Claim 1, wherein the phenol resin (B) contains the self-crosslinking type phenol resin (B-2).

4. The thermosetting acrylic resin composition according to Claim 1, wherein the phenol resin (B) does not contain the novolac-type phenol resin (B-1) and contains the self-crosslinking type phenol resin (B-2).

5. It contains the amine curing agent (C-2), The thermosetting acrylic resin composition according to Claim 3, wherein the content of the amine curing agent (C-2) is 0.002 parts by mass or more and 0.9 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer (A).

6. Furthermore, it contains the amine curing agent (C-2), The thermosetting acrylic resin composition according to claim 4, wherein the content of the amine-based curing agent (C-2) is 0.002 parts by mass or more and 0.9 parts by mass or less with respect to 100 parts by mass of the acrylic copolymer (A).

7. The thermosetting acrylic resin composition according to claim 1, further containing a filler.

8. An adhesive sheet or an adhesive tape including an adhesive layer formed of the thermosetting acrylic resin composition according to any one of claims 1 to 7.

9. An adhesive sheet or an adhesive tape including a base material and an adhesive layer formed of the thermosetting acrylic resin composition according to any one of claims 1 to 7 on at least one surface of the base material.

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