Heat curable acrylic resin composition and adhesive sheet or adhesive tape

Abstract

Provided is a heat-curable acrylic resin composition which is capable of suppressing the generation of ultra-fine bubbles when cured under heat and pressure, and which has excellent adhesiveness. A thermosetting acrylic resin composition which contains (A) an acrylic copolymer having a carboxyl group and (B) a phenolic resin, and which is characterized in that: when the acrylic copolymer (A) is an acrylic copolymer (A-1) having a glass transition temperature of-35 DEG C or less, the phenolic resin (B) is a phenolic resin; the thermosetting acrylic resin composition contains a specific content of an epoxy curing agent (C-1), contains a specific content of a novolac phenolic resin (B-1) or a self-crosslinking phenolic resin (B-2) as the phenolic resin (B), and contains a specific content of a novolac phenolic resin (B-1) or a self-crosslinking phenolic resin (B-2) when the novolac phenolic resin (B-1) is contained as the phenolic resin (B). The thermosetting acrylic resin composition also contains a specific content of an amine curing agent (C-2).

Description

Technical Field

[0001] The present invention relates to thermosetting acrylic resin compositions and adhesive sheets or tapes having an adhesive layer formed from the thermosetting acrylic resin composition. Background Technology

[0002] Typically, thermosetting adhesive compositions that can be cured by heat treatment are proposed for bonding applications of electronic components and vehicle components.

[0003] However, in recent years, the miniaturization and high performance of portable electronic information devices and other electronic equipment have led to a trend towards miniaturization of the electronic components they carry. Therefore, thermosetting adhesive compositions used for bonding and fixing miniaturized electronic components to flexible printed circuits (FPCs), cover layers, and metals are being developed to maximize adhesive strength even in thin films with small areas.

[0004] For example, Patent Document 1 discloses a thermosetting adhesive composition characterized by containing 1 to 60 parts by weight of phenolic resin and 1 to 25 parts by weight of hexamethylenetetramine relative to 100 parts by weight of a specific acrylic polymer.

[0005] Patent Document 2 discloses an adhesive composition comprising an acrylic polymer containing two specific acrylic copolymers, a methyl phenolic resin, and an epoxy resin.

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2010-065078

[0009] Patent Document 2: Japanese Patent Application Publication No. 2007-009057 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] The thermosetting adhesive composition in Patent Document 1 contains a large amount of hexamethylenetetramine, which results in a high amount of ammonia gas produced as a byproduct during the reaction, potentially leading to bubble formation. Furthermore, the high amount of hexamethylenetetramine facilitates the reaction, and its storage stability may deteriorate in high-temperature environments, such as summer conditions around 40°C.

[0012] The adhesive composition in Patent Document 2 has the following problems: Since epoxy-containing acrylic copolymers are special materials, they are not easily obtained; furthermore, their high cost increases manufacturing costs; and the limited variety restricts material selection. Additionally, since two acrylic copolymers with different monomer compositions are used, low compatibility is predicted, and changes over time due to phase separation may prevent the stable manufacture of adhesive compositions with the desired properties.

[0013] The inventors conducted in-depth research on the required properties of thermosetting adhesive compositions and discovered that when the thin-film adhesive composition (adhesive layer) is cured under heat and pressure, a very small amount overflows and flows out from between the adhered material and the substrate of the adhesive sheet or tape, generating ultrafine bubbles of several μm to tens of μm. Furthermore, it is known that these ultrafine bubbles are voids generated in the traces of the adhesive composition flowing out, and their generation affects the flowability of the adhesive composition under heat and pressure (e.g., the ease of flow due to the melting of resin components) and the amount of gas generated (e.g., gas originating from byproducts such as ammonia and water). Moreover, it was found that in areas where a large number of these ultrafine bubbles are generated, the bonding area decreases, parts of the adhesive sheet or tape peel off, or water or chemical infiltration or leakage occurs, leading to defective products.

[0014] The object of the present invention is to provide a thermosetting acrylic resin composition that suppresses the generation of ultrafine bubbles during curing under heat and pressure and has excellent adhesion, as well as an adhesive sheet or adhesive tape having an adhesive layer formed therefrom.

[0015] Methods for solving problems

[0016] In order to achieve the above-mentioned objectives, the inventors conducted in-depth research and as a result completed the present invention, which relates to a thermosetting acrylic resin composition comprising an acrylic copolymer, a phenolic resin and a curing agent, and an adhesive sheet or adhesive tape having an adhesive layer formed therefrom.

[0017] That is, the present invention includes the following methods.

[0018] [1] A thermosetting acrylic resin composition comprising an acrylic copolymer (A) having carboxyl groups and a phenolic resin (B),

[0019] When the acrylic copolymer (A) is an acrylic copolymer (A-1) with a glass transition temperature of -35°C or lower, the thermosetting acrylic resin composition further comprises an epoxy curing agent (C-1), wherein the content of the epoxy curing agent (C-1) is 0.000002 parts by weight or more and 0.4 parts by weight or less per 100 parts by weight of the acrylic copolymer (A-1).

[0020] When the phenolic resin (B) includes a phenolic varnish-type phenolic resin (B-1), the content of the phenolic varnish-type phenolic resin (B-1) is 2 parts by weight or more and 60 parts by weight or less relative to 100 parts by weight of the acrylic copolymer (A). The thermosetting acrylic resin composition further includes an amine curing agent (C-2), and the content of the amine curing agent (C-2) is 0.002 parts by weight or more and 0.9 parts by weight or less relative to 100 parts by weight of the acrylic copolymer (A).

[0021] In the absence of the phenolic resin (B) containing the phenolic varnish-type phenolic resin (B-1), the thermosetting acrylic resin composition includes a self-crosslinking phenolic resin (B-2), wherein the content of the self-crosslinking phenolic resin (B-2) is 2 parts by weight or more and 60 parts by weight or less relative to 100 parts by weight of the acrylic copolymer (A).

[0022] [2] The thermosetting acrylic resin composition according to [1], wherein the acrylic copolymer (A) is an acrylic copolymer (A-1) with a glass transition temperature of -35°C or below.

[0023] [3] The thermosetting acrylic resin composition according to [1], wherein the acrylic copolymer (A) is an acrylic copolymer (A-2) with a glass transition temperature higher than -35°C.

[0024] [4] A thermosetting acrylic resin composition according to any one of [1] to [3], wherein the phenolic resin (B) comprises a phenolic varnish type phenolic resin (B-1).

[0025] [5] A thermosetting acrylic resin composition according to any one of [1] to [4], wherein the phenolic resin (B) comprises a self-crosslinking phenolic resin (B-2).

[0026] [6] A thermosetting acrylic resin composition according to any one of [1] to [3], wherein the phenolic resin (B) does not contain the phenolic varnish type phenolic resin (B-1) but contains a self-crosslinking phenolic resin (B-2).

[0027] [7] The thermosetting acrylic resin composition according to [5] further comprises the amine curing agent.

[0028] The content of the amine curing agent is 0.002 parts by mass and 0.9 parts by mass or more, relative to 100 parts by mass of the acrylic copolymer (A).

[0029] [8] The thermosetting acrylic resin composition according to [6] further comprises the amine curing agent.

[0030] The content of the amine curing agent is 0.002 parts by mass and 0.9 parts by mass or more, relative to 100 parts by mass of the acrylic copolymer (A).

[0031] [9] The thermosetting acrylic resin composition according to any one of [1] to [8] further comprises filler.

[0032]

[10] An adhesive sheet or adhesive tape comprising an adhesive layer formed from any one of the thermosetting acrylic resin compositions described in [1] to [9].

[0033]

[11] An adhesive sheet or adhesive tape comprising a substrate and an adhesive layer formed on at least one surface of the substrate from any one of [1] to [9].

[0034] Invention Effects

[0035] According to the present invention, it is possible to provide a thermosetting acrylic resin composition that suppresses the generation of ultrafine bubbles during curing under heat and pressure and has excellent adhesion, as well as a thermosetting adhesive sheet or thermosetting adhesive tape having an adhesive layer formed therefrom. Attached Figure Description

[0036] Figure 1 This is a schematic cross-sectional view illustrating an example of the layer structure of the adhesive sheet or adhesive tape of the present invention.

[0037] Figure 2 A schematic cross-sectional view illustrating another example of the layer structure of the adhesive sheet or adhesive tape of the present invention.

[0038] Figure 3 It is a schematic cross-sectional view used to illustrate the evaluation test method for the generation of ultrafine bubbles in the adhesive layer of adhesive sheets or tapes.

[0039] Figure 4 It is a schematic top view used to illustrate the evaluation test method for the generation of ultrafine bubbles in the adhesive layer of adhesive sheets or tapes.

[0040] Figure 5 Digital microscopic images of evaluation test results (comparative examples) of ultrafine air bubbles generated in the adhesive layer of adhesive sheets or tapes.

[0041] Figure 6 Digital microscopic images of evaluation test results (examples) of ultrafine bubbles generated in the adhesive layer of adhesive sheets or tapes. Detailed Implementation

[0042] The preferred embodiments of the present invention will be described below.

[0043] (Thermosetting acrylic resin composition)

[0044] The thermosetting acrylic resin composition of the present invention is a thermosetting acrylic resin composition comprising an acrylic copolymer (A) having a carboxyl group and a phenolic resin (B). The acrylic copolymer (A) comprises an acrylic copolymer (A-1) with a glass transition temperature (hereinafter referred to as "Tg") of -35°C or lower, or an acrylic copolymer (A-2) with a Tg higher than -35°C. The phenolic resin (B) comprises a phenolic varnish-type phenolic resin (B-1) or a self-crosslinking phenolic resin (B-2).

[0045] Depending on the selection of acrylic copolymers (A-1) and (A-2), the thermosetting acrylic resin composition of the present invention may include the following embodiments. It should be noted that, in the thermosetting acrylic resin composition of the present invention, the phenolic resin (B) may also include phenolic varnish-type phenolic resin (B-1) and self-crosslinking phenolic resin (B-2), and may also include other thermosetting resins (D).

[0046] <Implementation Method (a): Case where the phenolic resin (B) includes phenolic varnish-type phenolic resin (B-1)>

[0047] Implementation (a) may include the following implementations (a1) and (a2).

[0048] (a1) A thermosetting acrylic resin composition, wherein the acrylic copolymer (A) is an acrylic copolymer (A-1) with a Tg of -35°C or lower, the thermosetting acrylic resin composition further comprises an epoxy curing agent (C-1), wherein 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 relative to 100 parts by mass of the acrylic copolymer (A-1), the phenolic resin (B) comprises a phenolic varnish-type phenolic resin (B-1), wherein the content of the phenolic varnish-type phenolic resin (B-1) is 2 parts by mass or more and 60 parts by mass or less relative to 100 parts by mass of the acrylic copolymer (A-1), the thermosetting acrylic resin composition further comprises an amine curing agent (C-2), 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 relative to 100 parts by mass of the acrylic copolymer (A).

[0049] (a2) A thermosetting acrylic resin composition, wherein the acrylic copolymer (A) is an acrylic copolymer (A-2) with a Tg higher than -35°C, the phenolic resin (B) comprises a phenolic varnish-type phenolic resin (B-1), and the content of the phenolic varnish-type phenolic resin (B-1) is 2 parts by weight or more and 60 parts by weight or less relative to 100 parts by weight of the acrylic copolymer (A-2), and the thermosetting acrylic resin composition further comprises an amine curing agent (C-2), and the content of the amine curing agent (C-2) is 0.002 parts by weight or more and 0.9 parts by weight or less relative to 100 parts by weight of the acrylic copolymer (A-2).

[0050] <Embodiment (b): The phenolic resin (B) does not contain the phenolic varnish-type phenolic resin (B-1)>

[0051] Implementation (b) may include the following implementations (b1) and (b2).

[0052] (b1) A thermosetting acrylic resin composition, wherein the acrylic copolymer (A) is an acrylic copolymer (A-1) with a Tg of -35°C or lower, the thermosetting acrylic resin composition further comprises an epoxy curing agent (C-1), wherein 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 relative to 100 parts by mass of the acrylic copolymer (A-1), and the phenolic resin (B) comprises a self-crosslinking phenolic resin (B-2), wherein the content of the phenolic resin (B-2) is 2 parts by mass or more and 60 parts by mass or less relative to 100 parts by mass of the acrylic copolymer (A-1).

[0053] (b2) A thermosetting acrylic resin composition, wherein the acrylic copolymer (A) is an acrylic copolymer (A-2) with a Tg higher than -35°C, and the phenolic resin (B) comprises a self-crosslinking phenolic resin (B-2), wherein the content of the self-crosslinking phenolic resin (B-2) is more than 2 parts by mass and less than 60 parts by mass relative to 100 parts by mass of the acrylic copolymer (A-2).

[0054] <Acrylic Copolymer (A)>

[0055] The acrylic copolymer (A) used in the thermosetting acrylic resin composition of the present invention is a copolymer having carboxyl groups.

[0056] It should be noted that "acrylic acid" is a general term that includes both "acrylic acid" and "methacrylic acid", and acrylic acid copolymer (A) is an acrylic acid copolymer or / and methacrylic acid copolymer.

[0057] The acid value of the acrylic copolymer (A) is preferably 0.1 mg KOH / g or more and 100 mg KOH / g or less, more preferably 1 mg KOH / g or more and 50 mg KOH / g or less, and even more preferably 4 mg KOH / g or more and 40 mg KOH / g or less.

[0058] If the acrylic copolymer (A) does not have carboxyl groups, the adhesive strength will not increase sufficiently. By keeping the acid value of the acrylic copolymer within a specified range, ultrafine bubbles can be effectively suppressed, and sufficient adhesive strength can be obtained.

[0059] The acid value is the amount (mg) of KOH required to neutralize 1g of acrylic copolymer (A), and can be determined according to the method of JIS K0070:1992.

[0060] The Tg of the acrylic copolymer (A) is preferably in the range of -100°C to 100°C, and more preferably in the range of -80°C to 20°C.

[0061] This Tg value is a theoretical value, calculated based on the following FOX formula.

[0062] 1 / Tg=W1 / Tg1+W2 / Tg2+W3 / Tg3+···+W i / Tg i

[0063] Here, subscripts 1, 2, 3, ... i represent the monomer components that constitute the copolymer, W i Tg represents the weight fraction of monomer component i. i This represents the Tg of the homopolymer of monomer component i. The Tg of the homopolymer can be found in the fourth edition of the Polymer Handbook (J. Brandrup, Wiley, 1998).

[0064] When the acrylic copolymer (A) is an acrylic copolymer (A-1) with a Tg below -35℃, ultrafine bubbles are easily generated. The generation of ultrafine bubbles can be effectively suppressed by using an epoxy curing agent (C-1) at a specified content.

[0065] The acrylic copolymer (A) preferably contains at least units of alkyl (meth)acrylate (AI) and units of carboxyl-containing monomer (AII) as units derived from the monomers forming the acrylic copolymer (A), and may further contain units of other monomer components as needed. It should be noted that "(meth)acrylate" is a general term that includes both "acrylic acid" and "methacrylic acid".

[0066] Examples of the aforementioned alkyl methacrylates (AI) include ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, pentyl methacrylate, isoamyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, isooctyl methacrylate, nonyl methacrylate, isononyl methacrylate, decyl methacrylate, isodecyl methacrylate, undecyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, and tetradecyl methacrylate. The alkyl group in an alkyl methacrylate (AI) can be straight-chain or branched. Preferably, alkyl (meth)acrylates having 2 to 14 carbon atoms are used; more preferably, alkyl (meth)acrylates having 4 to 12 carbon atoms are used; and even more preferably, n-butyl acrylate and 2-ethylhexyl acrylate are used.

[0067] The above-mentioned alkyl methacrylates (AI) can be used alone or in combination with two or more.

[0068] Alkyl methacrylate (AI) is preferably used as a major component in the formation of the acrylic copolymer (A). The content of alkyl methacrylate (AI) units in the acrylic copolymer (A) is preferably 80% by mass or more, more preferably 85% by mass or more, and furthermore, from the viewpoint of containing a sufficient amount of carboxyl-containing monomer (AII) units, it is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 95% by mass or less.

[0069] As for the aforementioned carboxyl-containing monomers (AII), there are no particular limitations on any monomer containing a carboxyl group; examples include (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Furthermore, the anhydrides of these carboxyl-containing monomers (such as maleic anhydride, itaconic anhydride, and other anhydride-containing monomers) can also be used as carboxyl-containing monomers. Among these, acrylic acid, methacrylic acid, and itaconic acid are preferred.

[0070] Carboxyl-containing monomers (AII) can be used alone or in combination of two or more.

[0071] By using an acrylic copolymer (A) containing carboxyl monomer (AII) units and combining it with an epoxy curing agent (C-1), the adhesion and meltability of thermosetting acrylic resin compositions can be improved. Furthermore, when the Tg of the acrylic copolymer (A) is low (especially below -35°C), ultrafine bubbles are easily generated during curing under heat and pressure. However, by utilizing the epoxy curing agent (C-1) to perform a crosslinking reaction on the acrylic copolymer (A), the resin components become less prone to melting, thus suppressing ultrafine bubbles.

[0072] From the perspective of ensuring sufficient cross-linking reaction, the content of carboxyl-containing monomer (AII) units in the acrylic copolymer (A) is preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more. Furthermore, there is no particular upper limit to the content, but it is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less. Additionally, the content of carboxyl-containing monomer (AII) units in the acrylic copolymer (A) is preferably set such that the acrylic copolymer (A) has the aforementioned acid value.

[0073] Acrylic copolymers (A) may contain units of other monomers (copolymeric monomers) that can copolymerize with alkyl (meth)acrylates (AI) and carboxyl-containing monomers (AII) to the extent that the desired effect is not compromised.

[0074] Examples of such copolymerizable monomers include methyl methacrylate; pentadecyl methacrylate, hexadecyl methacrylate, heptadecanyl methacrylate, octadecyl methacrylate, nonadecanyl methacrylate, eicosyl methacrylate, etc. (meth)acrylate C 15-20Alkyl esters; (meth)acrylates containing non-aromatic rings, such as cycloalkyl (meth)acrylates and isobornyl (meth)acrylate; (meth)acrylates containing aromatic rings, such as aryl (meth)acrylates, aryloxyalkyl (meth)acrylates, and arylalkyl (meth)acrylates; epoxy-containing acrylic monomers, such as glycidyl (meth)acrylate and methylglycidyl (meth)acrylate; vinyl ester monomers, such as vinyl acetate and vinyl propionate; styrene monomers, such as styrene and α-methylstyrene; hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate. Hydroxyl-containing monomers such as esters; alkoxyalkyl ester monomers of (meth)acrylate such as methoxyethyl acrylate and ethoxyethyl acrylate; aminoalkyl ester monomers of (meth)acrylate such as aminoethyl acrylate, N,N-dimethylaminoethyl acrylate and tert-butylaminoethyl 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; and vinyl ether monomers such as methyl vinyl ether.

[0075] In addition, as comonomers, multifunctional monomers such as hexanediol di(meth)acrylate, butanediol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, glycerol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, epoxy acrylate, polyester acrylate, urethane acrylate, and divinylbenzene can be used.

[0076] Acrylic copolymers (A) can be prepared, for example, by solution polymerization, emulsion polymerization, bulk polymerization, or polymerization using ultraviolet irradiation.

[0077] There are no particular restrictions on the polymerization initiators, chain transfer agents, solvents, etc. used in the polymerization of acrylic copolymers (A).

[0078] As a polymerization initiator, any polymerization initiator that is commonly used in the manufacture of general acrylic copolymers can be used for the polymerization of acrylic copolymer (A). Examples of polymerization initiators used in the polymerization of acrylic copolymers (A) include azo polymer initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(4-methoxy-2,4-dimethylpentanitrile), 2,2'-azobis(2,4-dimethylpentanitrile), 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carboxylonitrile), 2,2'-azobis(2,4,4-trimethylpentane), and dimethyl-2,2'-azobis(2-methylpropionate); and peroxide polymer initiators such as benzoyl peroxide, tert-butyl hydroperoxide, di-tert-butyl peroxide, tert-butyl peroxide, dicumyl peroxide, 1,1-bis(tert-butylperoxide)-3,3,5-trimethylcyclohexane, and 1,1-bis(tert-butylperoxide)cyclododecane. Polymerization initiators can be used alone or in combination of two or more. The amount of polymerization initiator used can be appropriately selected from the usual range.

[0079] As a chain transfer agent, any chain transfer agent commonly used in the manufacture of acrylic copolymers can be used in the polymerization of acrylic copolymer (A). Examples of chain transfer agents used in the polymerization of acrylic copolymer (A) include 2-mercaptoethanol, lauryl thiol, glycidyl thiol, mercaptoacetic acid, 2-ethylhexyl mercaptoacetic acid, 2,3-dimercapto-1-propanol, dodecyl thiol, and α-methylstyrene dimer. Chain transfer agents can be used alone or in combination of two or more. The amount of chain transfer agent used can be appropriately selected from the usual range.

[0080] In solution polymerization, the solvent, monomer, polymerization initiator and chain transfer agent as needed can be mixed. The monomer is dissolved in the solvent and polymerization is carried out by heating and / or irradiation with active energy rays such as ultraviolet light while stirring.

[0081] Various common solvents can be used in solution polymerization. Examples of 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 ketones such as methyl ethyl ketone and methyl isobutyl ketone. Solvents can be used alone or in combination of two or more.

[0082] In emulsion polymerization, polymerization is typically carried out with the monomer dispersed in water in the presence of a surfactant (emulsifier). By adding a polymerization initiator (or, if necessary, a chain transfer agent), the polymerization reaction can be initiated at room temperature or upon heating. There are no particular limitations on the type or amount of surfactant used. Known anionic, nonionic, and cationic surfactants can be used. Anionic or nonionic surfactants are preferred, but surfactants with reactive functional groups (typically free radical polymerization functional groups) can also be used. Surfactants can be used alone or in combination of two or more.

[0083] In bulk polymerization, monomers can be mixed with polymerization initiators and chain transfer agents as needed without the use of solvents, and polymerization can be carried out by self-heating or heating, and / or irradiation with active energy rays such as ultraviolet light, under stirring.

[0084] The weight-average molecular weight (Mw) of the acrylic copolymer (A) is not particularly limited as long as the desired characteristics 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 1.4 million or less, preferably 200,000 or more and 1.3 million or less, can be used. The weight-average molecular weight of the acrylic copolymer (A) can be controlled by the type or amount of polymerization initiator or chain transfer agent, the temperature or time of polymerization, the monomer concentration, the monomer supply rate, etc.

[0085] It should be noted that the weight-average molecular weight of the acrylic copolymer (A) can be determined by gel permeation chromatography (GPC) and can be obtained in the form of molecular weight converted from standard polystyrene.

[0086] <Phenolic Resin (B)>

[0087] The thermosetting acrylic resin composition of the present invention contains phenolic resin (B). Phenolic resin (B) is a curing component that contributes to the thermosetting properties of the thermosetting acrylic resin composition.

[0088] The phenolic resin (B) can contain either a phenolic varnish-type phenolic resin (B-1) capable of curing with an amine curing agent (C-2), or a self-crosslinking phenolic resin (B-2) that cures through heating; the type is not particularly limited. By allowing the phenolic resin (B) to undergo a crosslinking reaction with the amine curing agent (C-2), or by allowing the self-crosslinking phenolic resin (B-2) to undergo self-crosslinking, the adhesive properties and heat resistance of the thermosetting acrylic resin composition are improved.

[0089] Specific examples of phenolic resins (B-1) of the phenolic varnish type include phenolic varnish resin, cresol varnish resin, tert-butylphenol varnish resin, nonylphenol varnish resin, dicyclopentadiene cresol varnish resin, dicyclopentadiene phenol varnish resin, xylene-modified phenolic varnish resin, naphthol varnish resin, triphenol varnish resin, tetraphenol varnish resin, bisphenol F varnish resin, bisphenol A varnish resin, and phenol-modified xylene resin.

[0090] Examples of self-crosslinking phenolic resins (B-2) include liquid methyl phenolic resins, solid methyl phenolic resins, dimethylene ether methyl phenolic resins, and hydroxymethyl methyl phenolic resins. There are no particular limitations on the methyl phenolic resin used in this invention; it can be appropriately selected from conventionally known methyl phenolic resins. For example, a methyl phenolic resin prepared by reacting phenols such as phenol, p-cresol, xylenol, p-alkylphenol, p-phenylphenol, and resorcinol, or their derivatives, with aldehydes (e.g., formaldehyde, acetaldehyde) in the presence of an alkaline catalyst (e.g., sodium hydroxide, potassium hydroxide, calcium hydroxide, etc.), followed by neutralization and / or vacuum dehydration treatment as needed.

[0091] From a comprehensive evaluation perspective, phenolic varnish-type phenolic resin (B-1) is preferred as the phenolic resin (B). Furthermore, from a reactivity perspective, self-crosslinking type phenolic resin (B-2) is preferred. By using (B-1) or (B-2), for example, when bonding FPCs to each other, sufficient bond strength and suppression of ultrafine bubbles can be achieved simultaneously.

[0092] Phenolic resin (B) can be used alone or in combination with two or more types.

[0093] From the perspective of improving thermosetting properties, adhesion, and heat resistance, the content of phenolic resin (B) should be between 2 and 60 parts by mass relative to 100 parts by mass of acrylic copolymer (A). If the content of phenolic resin (B) is too low, the additive effect cannot be fully achieved; if the content of phenolic resin (B) is too high, curing may occur before sufficient adhesion is fully exhibited, potentially resulting in insufficient adhesive strength. Whether using phenolic varnish-type phenolic resin (B-1) alone, self-crosslinking phenolic resin (B-2) alone, or a combination of (B-1) and (B-2), the content of phenolic resin (B) should remain within the above-mentioned range.

[0094] <Epoxy Curing Agent (C-1)>

[0095] The epoxy curing agent (C-1) used in this invention is a component that reacts with the carboxyl group of an acrylic copolymer (A-1) to form a cross-linked structure. Examples include compounds having two or more epoxy groups in their molecules. Specific examples include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerol diglycidyl ether, glycerol triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diamine glycidyl amine, N,N,N',N'-tetraglycidyl m-phenylenediamine, and 1,3-bis(N,N-diglycidylaminomethyl)cyclohexane. As commercially available products, examples include E-5CM (product name) (1,3-bis(N,N-diglycidylaminomethyl)cyclohexane) manufactured by Soken Chemical Co., Ltd., E-5XM (product name) manufactured by Soken Chemical Co., Ltd., TEDRAD-C (product name) manufactured by Mitsubishi Gas Chemical Co., Ltd., and TEDRAD-X (product name) manufactured by Mitsubishi Gas Chemical Co., Ltd.

[0096] The content of epoxy curing agent (C-1) is 0.000002 parts by mass and less than 0.4 parts by mass, preferably 0.0000025 parts by mass and less than 0.38 parts by mass, relative to 100 parts by mass of acrylic copolymer (A-1) with a Tg of less than -35°C.

[0097] If the thermosetting acrylic resin composition does not contain epoxy curing agent (C-1) or contains a small amount of it, the crosslinking of the acrylic copolymer (A-1) cannot proceed sufficiently. Therefore, the resin components tend to melt easily, and thus tend to generate ultrafine bubbles when cured under heat and pressure. Conversely, if the content is too high, the crosslinking will be excessive, and thus tend to reduce the adhesion.

[0098] <Amine Curing Agent (C-2)>

[0099] The amine curing agent (C-2) used in this invention is a component that reacts with the carboxyl groups in phenolic resin (B) and acrylic copolymer (A) to form a cross-linked 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-phenylenediamine, etc.), cyclic aliphatic amines (such as N-aminoethylpiperazine, bis(3-methyl-4-aminocyclohexyl)methane, bis(4-aminocyclohexyl)methane, menthene diamine, isophorone diamine, 1,3-bis(aminomethyl)cyclohexane, etc.), heterocyclic amines (such as hexamethylenetetramine, piperazine, N,N-dimethylpiperazine, triethylenediamine, melamine, guanidine, etc.), and aromatic amines (such as m-phenylenediamine, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, etc.). Amine curing agents (C-2) can be used alone or in combination with two or more. Among them, hexamethylenetetramine is preferred from the perspective of bonding reliability.

[0100] When the phenolic resin (B) is a phenolic varnish type phenolic resin (B-1), the thermosetting acrylic resin composition of the present invention contains an amine curing agent (C-2).

[0101] The content of amine curing agent (C-2) is preferably less than 1 part by weight relative to 100 parts by weight of acrylic copolymer (A), more preferably 0.002 parts by weight or more and 0.9 parts by weight or less. If the thermosetting acrylic resin composition does not contain amine curing agent (C-2) or contains too little, crosslinking cannot proceed sufficiently, and therefore the resin components tend to melt easily, and thus there is a tendency to generate ultrafine bubbles. Conversely, if the content is too high, crosslinking will occur excessively, and therefore there is a tendency to reduce adhesive strength.

[0102] When the phenolic resin (B) is a self-crosslinking phenolic resin (B-2), the thermosetting acrylic resin composition of the present invention may or may not contain an amine curing agent (C-2), and when it is contained in order to promote crosslinking, the content range described above can be set.

[0103] <Other thermosetting resins (D)>

[0104] The thermosetting acrylic resin composition of the present invention may contain a thermosetting resin (D) other than an acrylic copolymer (A) and a phenolic resin (B). As the thermosetting resin (D), it can be any thermosetting resin capable of curing with an amine curing agent (C-2) or a self-crosslinking thermosetting resin that cures by self-crosslinking upon heating; there is no particular limitation on its type. By curing the thermosetting resin (D) with the amine curing agent (C-2), or by self-crosslinking if the thermosetting resin (D) is self-crosslinking, a crosslinked structure is formed, thereby improving properties such as adhesion and heat resistance. Examples of such thermosetting resins include epoxy resins, urea resins, cyanate ester resins, maleimide resins, acetal resins, phenolic aralkyl resins, poly(p-vinylphenol) resins, poly(p-hydroxystyrene) and other polyoxystyrene resins.

[0105] <Packaging (E)>

[0106] The thermosetting acrylic resin composition of the present invention may further contain filler (E). By containing filler (E), the thermosetting acrylic resin composition can easily adjust its physical properties such as elastic modulus, dimensional stability, yield strength, and elongation at break. Representative examples of filler (E) include inorganic fillers and organic fillers. Representative shapes of fillers include spherical, needle-like, and flake-like shapes. One type of filler may be selected from these, or two or more types of fillers may be included.

[0107] Examples of inorganic filler materials 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 whiskers, and boron nitride. Other inorganic filler materials include alloys, amorphous carbon, and graphite, in addition to elemental metals such as aluminum, gold, silver, copper, and nickel. On the other hand, organic filler materials include polymethyl methacrylate (PMMA), polyimide, polyamide-imide, polyetheretherketone, polyetherimide, and polyesterimide.

[0108] <Bio-based carbon content>

[0109] From the perspective of conserving petroleum resources and reducing carbon dioxide emissions, the bio-derived carbon content (bio-based carbon content) of the thermosetting acrylic resin composition of the present invention is preferably 20% by mass or more, more preferably 25% by mass or more, and even more preferably 50% by mass or more. Furthermore, the upper limit of this content is 100% by mass.

[0110] It should be noted that biologically derived carbon contains a certain proportion of the radioactive isotope C14, while petroleum-derived carbon contains almost no C14. Therefore, the content of biologically derived carbon can be calculated by measuring the C14 concentration in the thermosetting acrylic resin composition. Specifically, this can be determined according to ASTM D 6866-20 or ISO international standard ISO 16620-2.

[0111] (Adhesive sheet or adhesive tape)

[0112] The adhesive sheet or adhesive tape of the present invention is provided with an adhesive layer formed of the thermosetting acrylic resin composition of the above embodiments.

[0113] As a form of adhesive sheet or adhesive tape, a so-called "substrate-free type" can be provided, consisting only of an adhesive layer.

[0114] Substrate-free adhesive sheets or tapes can be formed, for example, by coating a thermosetting acrylic resin composition onto a support such as release paper and then drying it.

[0115] Alternatively, the adhesive layer may include a release liner, which will be described later. In this method, when the adhesive layer has two main surfaces, the release liner is positioned to contact one or both of the two main surfaces.

[0116] In addition, the adhesive sheet or adhesive tape of the embodiments of the present invention may also be provided with an adhesive layer formed of the thermosetting acrylic resin composition of the above embodiments on at least one surface of the substrate.

[0117] The adhesive layer formed from a thermosetting acrylic resin composition can be formed on only one side of the substrate or on both sides of the substrate. Furthermore, the adhesive layer can be formed in direct contact with the substrate, or an easy-bonding treatment layer can be provided between the substrate and the adhesive layer. The easy-bonding treatment layer is formed by performing an easy-bonding treatment on the surface where the adhesive layer is located. Examples of easy-bonding treatments include primer treatment, corona treatment, etching treatment, plasma treatment, and sandblasting treatment; one or more of these treatments can be performed.

[0118] The adhesive layer can be formed as follows: a layer-forming composition material comprising a thermosetting acrylic resin composition and a solvent is coated onto a substrate; the solvent is evaporated by heating, or the coating layer is further subjected to a crosslinking reaction. The coating layer can be formed using conventional coating equipment such as roller coaters, die coaters, or lip coaters. If heating is performed after coating, the solvent in the layer-forming material can be removed along with the heat-based crosslinking reaction.

[0119] The adhesive layer can also be applied to the substrate by transfer printing. In this case, to improve the adhesion between the substrate and the adhesive layer, it is preferable to use heated rollers for lamination.

[0120] The thickness of the adhesive layer after drying can be set to, for example, 200 μm or less, preferably 1 μm or more and 150 μm or less, and more preferably 1.5 μm or more and 100 μm or less.

[0121] The planar dimensions of the adhesive sheets and adhesive tapes can be appropriately set according to the planar dimensions of the substrate used during manufacturing, or they can be cut to the desired dimensions after manufacturing. Alternatively, they can be made into wound bodies. It should be noted that in this specification, wide sheet-like materials (and their wound bodies) are referred to as adhesive sheets, and long, narrow strip-like materials (and their wound bodies) are referred to as adhesive tapes.

[0122] Figure 1 A schematic cross-sectional view showing a single-sided adhesive sheet or single-sided adhesive tape with an adhesive layer 12 provided on one side of a substrate 11. Figure 2 A schematic cross-sectional view showing a double-sided adhesive sheet or double-sided adhesive tape with adhesive layers 22 and 23 on both sides of the substrate 21.

[0123] In a single-sided adhesive sheet or single-sided adhesive tape, the substrate 11 may have a laminated structure, and preferably the outermost layer on the side of surface 11B is a resin layer.

[0124] In single-sided adhesive sheets or tapes, easy-adhesion treatments can be applied to the surface 11A of the substrate 11 as needed, such as surface treatments like corona discharge treatment, or a base coating such as an easy-adhesion treatment layer. By performing easy-adhesion treatments, the adhesion of the adhesive layer 12 to the substrate 11 can be improved.

[0125] By applying a release agent to the surface 11B of the substrate 11 as needed, such as by providing a release layer, the adhesive composition of the adhesive layer 12 can be prevented from adhering to the surface 11B of the substrate 11 when the single-sided adhesive sheet or single-sided adhesive tape is wound into a roll, and the ease of unwinding (pulling out) can be maintained.

[0126] A release liner, described later, may be provided on the surface of the adhesive layer 12 (the side opposite to the substrate 11).

[0127] exist Figure 2 In the double-sided adhesive sheet or double-sided adhesive tape shown, both sides (21A and 21B) or either side of the substrate 21 can be treated for easy adhesion, such as surface treatment like corona discharge treatment, or a base coating such as an easy-adhesion treatment layer can be applied. By performing easy-adhesion treatment, the adhesion between the adhesive layer 22 or adhesive layer 23 and the substrate 21 can be improved.

[0128] A release liner, described later, may be provided on the surface of adhesive layer 22 or / and adhesive layer 23 (the side opposite to the substrate 21 side).

[0129] The substrate is not particularly limited as long as it functions as a support for the adhesive layer; films, nonwoven fabrics, foams, cloths, papers, and combinations thereof commonly used in adhesive films or tapes can be used. Among these, films that readily exhibit uniform thickness are preferred, and resin films possessing the necessary heat resistance under the operating environment are particularly preferred. Specific examples include polyimide resins such as polyimide (PI) and polyamide-imide (PAI), polyamide resins such as polyamide (PA) and polyetheramide, polyetherketone resins such as polyetherketone and polyetheretherketone (PEEK), polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyphenylene sulfide (PPS), polyethersulfone (PES), and fluoropolymers (e.g., polytetrafluoroethylene (PTFE), ethylene-polytetrafluoroethylene copolymer (ETFE), perfluoroalkoxyalkane (PFA)). These films can be used as single-layer or multi-layer laminates. The laminated film can comprise one or more multilayer combinations made of different materials. As a heat-resistant resin film, polyimide film with excellent dimensional stability at high temperatures is particularly preferred.

[0130] There is no particular limitation on the thickness of the substrate, which can be preferably 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.

[0131] The surface of the substrate to which the adhesive layer is applied can be treated for easy adhesion, as needed. Examples of easy adhesion treatments include primer treatment, corona treatment, etching treatment, plasma treatment, and sandblasting treatment. One or more of these treatments can be used in combination.

[0132] Surface treatments such as antistatic treatment can be applied to the substrate as needed. Examples of antistatic treatments include the use of cationic surfactants, anionic surfactants, and nonionic surfactants. Additionally, coloring treatments based on printing, mixing, etc., can be applied to the substrate as required.

[0133] The bio-based carbon content of the substrate is preferably 25% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more. Furthermore, the upper limit is 100% by mass.

[0134] The adhesive layer is formed only on one side of the substrate. Without a release liner, it is preferable that at least the outermost layer of the substrate, on the side opposite to where the adhesive layer is located, is made of a resin material. Furthermore, it is preferable to treat the surface of the substrate or the surface of the outermost layer (the side without the adhesive layer) with a release agent. By applying the release agent, the rolled adhesive sheet can be easily peeled off for use. During manufacturing, the adhesive sheet formed by coating the substrate with the adhesive composition can be rolled into a roll, then peeled off (unwound), processed, and unwound again. Preferably, the release agent is an acrylic resin, a fluoropolymer, an alkyd resin, a mixture of alkyl and amino resins, a polyurethane resin, or a silicone release agent.

[0135] (Peeling off the liner)

[0136] As a release liner, conventional 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 adhered to the substrate. As a release liner, a substrate with a release layer can be used, such as resin films (e.g., PET films), paper, cloth, etc., that have been surface-treated with release agents such as silicone, long-chain alkyl, or fluorinated resins. Alternatively, low-adhesion films formed from nonpolar polymers such as fluoropolymers (e.g., polytetrafluoroethylene) and olefin resins (e.g., polyethylene, polypropylene, etc.) can also be used.

[0137] (Manufacturing method of adhesive sheets or adhesive tapes)

[0138] The manufacturing method of the adhesive sheet or adhesive tape of the present invention is not particularly limited, and it can be manufactured by forming an adhesive layer on at least one surface of a substrate. As a common method, the adhesive layer can be formed by a coating method that directly coats the substrate as described below, or by a transfer method that forms the adhesive layer on the surface of the release liner and adheres the adhesive layer side of the release liner with the adhesive layer to the substrate.

[0139] The formation of the adhesive layer can be exemplified by applying an adhesive composition containing the aforementioned components onto the surface of a substrate (or release liner).

[0140] To adjust the viscosity of the adhesive composition during coating, a solvent can be added. Specific examples of solvents include aromatic solvents such as toluene and xylene; aliphatic solvents such as hexane, octane, and isoparaffins; 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.

[0141] Examples of mixing methods for preparing adhesive compositions include mechanical mixing and dispersion, and solvent dispersion. Apparatus used for this dispersion includes mixers / kneaders, ball mills, planetary mixers, coating mixers, and three-roll mills. Combinations of two or more of these apparatuses can also be used.

[0142] Methods for applying adhesive compositions to the surface of a substrate (or release liner) include, for example, using a roller coater or a reverse coater.

[0143] By means of the above-described coating method, one or more layers of adhesive composition can be applied to the surface of a substrate (or release liner), and heating can be applied as needed to form an adhesive layer on the surface of the substrate (or release liner).

[0144] Example

[0145] The present invention will be described in detail below through embodiments, but the present invention is not limited to these embodiments.

[0146] The constituent materials of the prepared curable acrylic resin composition are as follows.

[0147] (Acrylic copolymer (A))

[0148] (A-1) Manufactured by Toray Coatex, product name: R-2000 (containing carboxyl groups)

[0149] (A-2) Manufactured by Toray Coatex, product name: R-6000 (carboxyl-free)

[0150] (A-2) Manufactured by Toray Coatex, product name: R-9000 (containing carboxyl groups)

[0151] (A-2) Manufactured by Nagase ChemteX, product name: SG-70L (containing carboxyl groups).

[0152] (A-2) Manufactured by Nagase ChemteX, product name: WS-023 (containing carboxyl groups).

[0153] (A-2) Manufactured by Nagase ChemteX, product name: SG-708-6 (containing carboxyl group).

[0154] (Phenolic resin (B))

[0155] (B-1) Manufactured by Arakawa Chemical Industry Co., Ltd., Product Name: TAMANOL 759 (Phenolic Varnish Type)

[0156] (B-2) Manufactured by Aica Kogyo, product names: CKM-908 (Type A), CKS-3898 (Type A)

[0157] (Epoxy curing agent (C-1))

[0158] Manufactured by Zongyan Chemical Co., Ltd., Product Name: E-5CM (1,3-bis(N,N-diglycidylaminomethyl)cyclohexane)

[0159] (Amine curing agent (C-2))

[0160] Manufactured by Ouchi Shinshin Chemical Industry Co., Ltd., product name: NOCCELER H (hexamethylenetetramine).

[0161] <Preparation of Thermosetting Acrylic Resin Compositions and Adhesive Sheets>

[0162] As shown in Tables 1 and 2, a thermosetting acrylic resin composition is obtained by mixing phenolic resin (B) (B-1 or B-2), epoxy curing agent (C-1), amine curing agent (C-2), and ethyl acetate (diluent) in a specified ratio (by weight) relative to 100 parts by weight of the solid content of acrylic copolymer (A) (A-1 or A-2).

[0163] The thermosetting acrylic resin composition was coated onto a PET release liner. Then, it was heated to 100°C to evaporate the solvent, or to further induce a crosslinking reaction in the coating layer, forming an adhesive layer. The PET release liner was then bonded to the adhesive layer, and the crosslinking reaction was accelerated at 40°C for 3 days to obtain the target adhesive layer (15 μm thick).

[0164] Next, one of the PET release liner on each side of the adhesive layer is peeled off. A polyimide film (manufactured by Toray DuPont, product name: Kapton (registered trademark) 100H) is laminated on the side where the PET release liner has been peeled off using a benchtop laminator at a temperature of 100°C, resulting in an adhesive sheet with an adhesive layer on one side of the polyimide film.

[0165] <Determination and Evaluation of Bond Strength>

[0166] The obtained adhesive sheet was cut into 20mm wide and 125mm long pieces to make an evaluation sample. Then, the sample with the PET release liner removed was attached to a copper plate (manufactured by PALTEK Co., Ltd., product name: C1100P) with a thickness of 0.7mm, a width of 50mm, and a length of 125mm.

[0167] Next, imagine the hot pressing of the adhesive sheet in actual use. Overlap a stainless steel (SUS304) plate with a thickness of 2.0 mm, a width of 50 mm, and a length of 125 mm on the side of the adhesive sheet. Place a 2 kg weight on the stainless steel plate and heat it in a dryer set to 180°C for 1 hour.

[0168] Next, after cooling at 23°C for more than 1 hour, the force required to peel the adhesive sheet from the copper plate was measured using a tensile testing machine (manufactured by Toyo Seiki Co., Ltd., product name: Strograph EL) at 23°C, peeling speed of 300 mm / min and peeling angle of 180°.

[0169] The adhesive strength during heat curing was determined according to the following criteria. The results are shown in Table 1.

[0170] A: The maximum adhesive strength is above 10N / 20mm (very good).

[0171] B: The maximum adhesive strength is above 6N / 20mm and less than 10N / 20mm (good).

[0172] C: Maximum adhesive strength is less than 6N / 20mm (poor)

[0173] <Evaluation Test for the Generation of Microbubbles in Adhesive Layers>

[0174] Cut the prepared adhesive sheet into 10mm squares and attach it to a glass plate (manufactured by AGC Company, product name: float glass) with a thickness of 2.0mm, a width of 50mm, and a length of 125mm to make a test piece.

[0175] like Figure 3 As shown, for the prepared test piece, a heated press was used to apply pressure to the entire test piece for 90 seconds at a temperature of 130°C and a pressure of 2.0 MPa. During this pressure application, to ensure uniform pressure, a 10mm square silicone rubber sheet (manufactured by Irumagawa Rubber Co., Ltd., product name: IS-825, hardness 50°) cut to a thickness of 2mm was placed on the test piece, and pressure was applied from it. It should be noted that... Figure 3 In the figure, reference numeral 30 indicates a glass plate, reference numeral 31 indicates a substrate (polyimide film), and reference numeral 32 indicates an adhesive layer (thermosetting acrylic resin composition).

[0176] Next, after cooling at 23°C for more than 1 hour, the maximum length (L1, L2, L3, L4) and the maximum width (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 (KEYENCE Co., Ltd., product name: VHX-8000).

[0177] Figure 4 A schematic top view of the test piece during the measurement. Figure 4 In the figure, reference numeral 30 indicates a glass plate, reference numeral 31 indicates a substrate (polyimide film), and reference numeral 32 indicates an adhesive layer (thermosetting acrylic resin composition).

[0178] The lengths of the longest ultrafine bubbles observed in the first to fourth observation sections are designated as L1, L2, L3, and L4, respectively. The widths of the widest ultrafine bubbles observed in the first to fourth observation sections are designated as W1, W2, W3, and W4, respectively. It should be noted that the lengths (L1, L2, L3, L4) are defined as the lengths perpendicular to the edge (boundary line) of the substrate (the length of the bubble on the substrate side). The widths (W1, W2, W3, W4) are defined as the lengths along the edge (boundary line) of the substrate. Considering the potential deviation in the generation of ultrafine bubbles, the first to fourth observation sections are each observed at 200x magnification, covering approximately 1-2 / 3 of the substrate's edge length (including the central portion of the edge).

[0179] Based on the measured values ​​(in μm) of these lengths (L1, L2, L3, L4) and widths (W1, W2, W3, W4), the area index (S), which serves as an indicator of the amount of ultrafine bubbles generated, is calculated according to the following formula, and the results are evaluated. The results are shown in Tables 1 and 2.

[0180] S=L total ×W total

[0181] L total =L1+L2+L3+L4

[0182] W total =W1+W2+W3+W4

[0183] The evaluation of the amount of ultrafine bubbles generated is based on the area index (S) according to the following criteria.

[0184] A: S is less than 10000μm 2 (Excellent)

[0185] B: S is 10000μm 2Above and below 15000μm 2 (good)

[0186] C: S is 15000μm 2 The above (bad)

[0187] Figure 5 and Figure 6 Digital microscope images representing the evaluation results of ultrafine bubble generation. Figure 5 The evaluation test results of Comparative Example 4, which does not have the structure of the present invention, are as follows. Figure 6 These are the evaluation test results of Embodiment 2 of the present invention. Each image is a magnified view of the area near the end edge (boundary) of the substrate (polyimide film) of the adhesive sheet. Figure 5 It can be seen that in the comparative example without 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 end of the adhesive sheet). On the other hand, by Figure 6 As can be seen, in the embodiments of the present invention, the generation of ultrafine bubbles is suppressed.

[0188] The following criteria shall be used to determine the comprehensive evaluation of the performance of the adhesive sheet (adhesive strength and generation of microbubbles).

[0189] A: All ratings are A (very good).

[0190] B: There is a B rating, but no C rating (good).

[0191] C: If there is at least one C rating, it is considered a defective product.

[0192] Table 1

[0193]

[0194] Table 2

[0195]

[0196] Comparing Examples 1 and 2 with Comparative Example 1, it can be seen that if the epoxy curing agent (C-1) is not present, ultrafine bubbles are easily generated. By including the epoxy curing agent (C-1), the generation of ultrafine bubbles can be suppressed.

[0197] Comparing Examples 1 and 2 with Comparative Example 2, it can be seen that if the content of epoxy curing agent (C-1) is too high, the adhesive strength is reduced. Sufficient adhesive strength can be obtained by including a specified amount of epoxy curing agent (C-1).

[0198] Comparing Examples 1 and 2 with Comparative Example 7, it can be seen that if the acrylic copolymer (A) does not have carboxyl groups (acid value of 0), it is easy to generate ultrafine bubbles and the adhesive force is not sufficiently increased. By using the acrylic copolymer (A) with carboxyl groups, the generation of ultrafine bubbles can be suppressed and sufficient adhesive force can be obtained.

[0199] Comparing Examples 3 and 4 with Comparative Example 3, it can be seen that if the content of phenolic resin (B) is low, ultrafine bubbles are easily generated. By fully containing phenolic resin (B), the generation of ultrafine bubbles can be suppressed.

[0200] Comparing Examples 3 and 4 with Comparative Example 5, it can be seen that if the content of phenolic resin (B) is too high, the adhesive strength is reduced. Sufficient adhesive strength can be obtained by including a specified amount of phenolic resin (B).

[0201] Comparing Example 5 with Comparative Examples 4 and 6, it can be seen that when the phenolic resin (B) is a phenolic varnish type phenolic resin (B-1), if the content of amine curing agent (C-2) is too low or 0, ultrafine bubbles are easily generated. By fully containing amine curing agent (C-2), the generation of ultrafine bubbles can be suppressed.

[0202] Comparing Example 5 with Comparative Examples 8 and 9, it can be seen that even with an increased content of amine curing agent (C-2), microbubbles are easily generated if epoxy curing agent (C-1) is not present. By containing a specified amount of amine curing agent (C-2) and epoxy curing agent (C-1), the generation of microbubbles can be effectively suppressed. Furthermore, comparing Comparative Example 1 with Comparative Examples 8 and 9, it can be seen that if the content of amine curing agent (C-2) is too high, there is a tendency for the adhesive strength to decrease.

[0203] Comparing Examples 6, 7, 8, and 9 with Comparative Example 1, it can be seen that when the acrylic copolymer (A) is an acrylic copolymer (A-1) with a Tg below -35°C, ultrafine bubbles are easily generated if the epoxy curing agent (C-1) is not present. In this case, it can be seen that by including a specified amount of epoxy 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) with a Tg above -35°C as in Examples 6, 7, 8, and 9, the generation of ultrafine bubbles can be suppressed even if the epoxy curing agent (C-1) is not present.

[0204] As shown in Examples 10 and 11, when the phenolic resin (B) is a self-crosslinking phenolic resin (B-2) (Type A), even without the presence of an amine curing agent (C-2), the generation of ultrafine bubbles can be suppressed and sufficient adhesive strength can be obtained.

[0205] Comparing Examples 10 and 11 with Comparative Example 10, it can be seen that when the phenolic resin (B) is a self-crosslinking phenolic resin (B-2) (a type of methyl phenolic resin) and the acrylic copolymer (A) is an acrylic copolymer (A-1) with a Tg of -35°C or lower, ultrafine bubbles are easily generated even without the presence of an epoxy curing agent (C-1). By including an epoxy curing agent (C-1), the generation of ultrafine bubbles can be suppressed.

[0206] Comparing Examples 10 and 11 with Comparative Example 11, it can be seen that when the phenolic resin (B) is a self-crosslinking phenolic resin (B-2) (Type A), if the content of phenolic resin (B) is low, ultrafine bubbles are easily generated. By fully containing phenolic resin (B), the generation of ultrafine bubbles can be suppressed.

[0207] Industrial utilization potential

[0208] The thermosetting acrylic resin composition of the present invention, and the adhesive sheets and tapes using the same, exhibit both suppression of microbubbles and excellent adhesion when cured under heat and pressure. Therefore, they are suitable for all applications requiring such properties. For example, they are suitable for applications in portable electronic devices such as smartphones, tablets, car navigation systems, cameras, audio-visual equipment, game consoles, and information devices, as well as for vehicle applications. Specifically, they are particularly suitable for applications such as bonding FPCs within electronic devices. Furthermore, in vehicle applications, they can be used for fixing automotive structural components, exterior trim, or interior trim.

[0209] Explanation of reference numerals in the attached figures

[0210] 11: Substrate

[0211] 12: Adhesive layer,

[0212] 21: Substrate

[0213] 22: Adhesive layer,

[0214] 23: Adhesive layer,

[0215] 30: Glass plate

[0216] 31: Substrate (polyimide film),

[0217] 32: Adhesive layer (thermosetting acrylic resin composition).

Claims

1. A thermosetting acrylic resin composition comprising an acrylic copolymer (A) having carboxyl groups and a phenolic resin (B), When the acrylic copolymer (A) is an acrylic copolymer (A-1) with a glass transition temperature of -35°C or lower, the thermosetting acrylic resin composition further comprises an epoxy curing agent (C-1), wherein the content of the epoxy curing agent (C-1) is 0.000002 parts by weight or more and 0.4 parts by weight or less per 100 parts by weight of the acrylic copolymer (A-1). When the phenolic resin (B) includes a phenolic varnish-type phenolic resin (B-1), the content of the phenolic varnish-type phenolic resin (B-1) is 2 parts by weight or more and 60 parts by weight or less relative to 100 parts by weight of the acrylic copolymer (A). The thermosetting acrylic resin composition further includes an amine curing agent (C-2), and the content of the amine curing agent (C-2) is 0.002 parts by weight or more and 0.9 parts by weight or less relative to 100 parts by weight of the acrylic copolymer (A). In the absence of the phenolic resin (B) containing the phenolic varnish-type phenolic resin (B-1), the thermosetting acrylic resin composition includes a self-crosslinking phenolic resin (B-2), wherein the content of the self-crosslinking phenolic resin (B-2) is 2 parts by weight or more and 60 parts by weight or less relative to 100 parts by weight of the acrylic copolymer (A).

2. The thermosetting acrylic resin composition according to claim 1, wherein, The acrylic copolymer (A) is an acrylic copolymer (A-1) with a glass transition temperature below -35°C.

3. The thermosetting acrylic resin composition according to claim 1, wherein, The acrylic copolymer (A) is an acrylic copolymer (A-2) with a glass transition temperature higher than -35°C.

4. The thermosetting acrylic resin composition according to claim 1, wherein, The phenolic resin (B) includes phenolic varnish-type phenolic resin (B-1).

5. The thermosetting acrylic resin composition according to claim 1, wherein, The phenolic resin (B) includes a self-crosslinking phenolic resin (B-2).

6. The thermosetting acrylic resin composition according to claim 1, wherein, The phenolic resin (B) does not contain the phenolic varnish-type phenolic resin (B-1) but contains a self-crosslinking phenolic resin (B-2).

7. The thermosetting acrylic resin composition according to claim 5, further comprising the amine curing agent (C-2), The content of the amine curing agent (C-2) is 0.002 parts by mass and less than 0.9 parts by mass relative to 100 parts by mass of the acrylic copolymer (A).

8. The thermosetting acrylic resin composition according to claim 6, further comprising the amine curing agent (C-2), The content of the amine curing agent (C-2) is 0.002 parts by mass and less than 0.9 parts by mass relative to 100 parts by mass of the acrylic copolymer (A).

9. The thermosetting acrylic resin composition according to claim 1, further comprising filler.

10. An adhesive sheet or adhesive tape comprising an adhesive layer formed from any one of the thermosetting acrylic resin compositions of claims 1 to 9.

11. An adhesive sheet or adhesive tape comprising a substrate and an adhesive layer formed on at least one surface of the substrate from a thermosetting acrylic resin composition according to any one of claims 1 to 9.

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