adhesive composition

Abstract

Provided is an adhesive composition from which an adhesive layer having an excellent electrical property and an excellent adhesion (stickiness) after heat and curing can be formed, and with which an adhesion (stickiness) during a laminating process can be further improved, and peeling or lifting of a layer during a temporary fixing or a roll-to-roll operation can be prevented.　The adhesive composition includes: a styrene-based elastomer containing a carboxyl group; a styrene-based elastomer containing no carboxyl group; and an epoxy resin.

Description

[Technical Field]

[0001] The present invention relates to an adhesive composition, and more particularly to an adhesive composition that can be used for bonding electronic components and the like. [Background technology]

[0002] BACKGROUND ART As electronic devices become smaller and lighter, the adhesive applications for electronic components and the like are becoming more diverse, and the demand for laminates with adhesive layers is increasing. Furthermore, flexible printed circuit boards (hereinafter referred to as FPCs), which are one type of electronic component, are required to process large amounts of data at high speed, and progress is being made in supporting higher frequencies.Increasing the frequency of FPCs requires lower dielectric constant components, and low-dielectric substrate films and low-dielectric adhesives are being developed.

[0003] However, because low-dielectric adhesives have low molecular polarity, they are less likely to exhibit adhesion (bonding) with base films, metal layers, and other components related to electronic parts, and low-dielectric base films can also have poor adhesion (bonding) with adhesives. Therefore, in order to meet the demand for high adhesiveness while maintaining good electrical properties (low dielectric constant and low dielectric dissipation factor), a laminate has been proposed which uses an adhesive composition containing a carboxyl group-containing styrene-based elastomer (A) and an epoxy resin (B) and which comprises an adhesive layer made of the adhesive composition and a substrate film (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2016 / 017473 Summary of the Invention [Problem to be solved by the invention]

[0005] However, although the adhesive composition described in Patent Document 1 exhibits high adhesion (bonding properties) after heat curing, it has been found that, for example, when subjected to a lamination process with a short heating time in the manufacturing process of a laminate, the adhesive composition may not adhere sufficiently to the substrate film or other components related to electronic parts. In the lamination process, if the adhesive composition does not adhere sufficiently to the substrate film or other components related to electronic parts, peeling or lifting of layers occurs during temporary fixation when laminating by thermocompression or during roll-to-roll operation in the production of a laminate. This causes various problems in the laminate, such as lamination defects and gaps caused by minute irregularities between layers, which can cause swelling of the layers in the subsequent heating process.

[0006] Therefore, an object of the present invention is to provide an adhesive composition that has excellent electrical properties and is capable of forming an adhesive layer that has excellent adhesion (adhesion) after heat curing, and that can further improve adhesion (adhesion) in the lamination process and prevent peeling or lifting of layers during temporary fixing or roll-to-roll operations. [Means for solving the problem]

[0007] As a result of extensive research into solving the above-mentioned problems, the present inventors discovered that an adhesive composition containing at least three components, i.e., a carboxyl group-containing styrene-based elastomer, a carboxyl group-free styrene-based elastomer, and an epoxy resin, not only exhibits high adhesion (adhesion) to a substrate film after heat curing, but also exhibits sufficient adhesion (adhesion) to a substrate film in a lamination process, thereby solving the above-mentioned problems and completing the present invention.

[0008] The present invention includes the following aspects. [1] An adhesive composition containing a carboxyl group-containing styrene-based elastomer, a carboxyl group-free styrene-based elastomer, and an epoxy resin. [2] The adhesive composition according to [1], wherein the content of the epoxy resin is 1 to 20 parts by mass per 100 parts by mass of the adhesive composition. [3] The adhesive composition according to [1] or [2], wherein the content of the carboxyl group-containing styrene-based elastomer is less than 50 parts by mass per 100 parts by mass of the adhesive composition. [4] The adhesive composition according to any one of [1] to [3], wherein the softening point or melting point of the epoxy resin is 90° C. or lower. [5] The adhesive composition according to any one of [1] to [4], further comprising an organic peroxide. [6] An adhesive layer made of the adhesive composition according to any one of [1] to [5], wherein the storage modulus of the adhesive layer at 120°C before curing is 5 × 10 5 Pa or less, adhesive layer. [7] An adhesive layer made of the adhesive composition according to any one of [1] to [5], wherein the adhesive layer has a storage modulus at 25°C after curing of 8 × 10 7 Pa or more, adhesive layer. [8] An adhesive layer obtained by curing the adhesive composition according to any one of [1] to [5], wherein the adhesive layer has a relative dielectric constant of 3.5 or less and a dielectric loss tangent of 0.01 or less, measured at a frequency of 28 GHz. [9] A base film; A laminate comprising an adhesive layer made of the adhesive composition according to any one of [1] to [5], or an adhesive layer according to any one of [6] to [8].

[10] The laminate according to [9], wherein the substrate film contains polyether ether ketone (PEEK) resin.

[11] A coverlay film with an adhesive layer comprising the laminate according to [9] or

[10] .

[12] A copper-clad laminate comprising the laminate according to [9] or

[10] .

[13] A printed wiring board comprising the laminate according to [9] or

[10] .

[14] A shielding film comprising the laminate according to [9] or

[10] .

[15] A printed wiring board with a shielding film, comprising the laminate according to [9] or

[10] . [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an adhesive composition that has excellent electrical properties and can form an adhesive layer that has excellent adhesion (adhesion) after heat curing, and that can further improve adhesion (adhesion) in the lamination process and prevent peeling or lifting of layers during temporary fixing or roll-to-roll operations. DETAILED DESCRIPTION OF THE INVENTION

[0010] The adhesive composition of the present invention, a laminate including an adhesive layer made of the adhesive composition, and a component related to electronic components including the laminate will be described in detail below. However, the description of the constituent elements described below is an example of one embodiment of the present invention, and the present invention is not limited to these contents.

[0011] (Adhesive composition) The adhesive composition of the present invention contains a carboxyl group-containing styrene-based elastomer, a carboxyl group-free styrene-based elastomer, and an epoxy resin. The adhesive composition of the present invention may contain other components as needed.

[0012] <Carboxy group-containing styrene elastomer> Carboxy group-containing styrene elastomers are effective as a component that imparts electrical properties in addition to adhesive properties and flexibility to the cured product. The adhesive composition contains a carboxyl group-containing styrene elastomer, which allows the flexible adhesive composition to conform sufficiently to the surface of the substrate film, even if the substrate film has good electrical properties and low polarity, allowing the low-polarity skeleton to exhibit adhesion, and even if the substrate film has a metal layer, the highly polar carboxyl group can exhibit adhesion, improving the adhesion of the adhesive layer. Furthermore, because the carboxyl group-containing styrene elastomer is reactive, epoxy curing also improves the heat resistance and chemical resistance of the adhesive layer. The carboxyl group-containing styrene elastomer is a copolymer mainly consisting of block and random structures of a conjugated diene compound and an aromatic vinyl compound, or a hydrogenated product thereof modified with an unsaturated carboxylic acid. Examples of aromatic vinyl compounds include styrene, t-butylstyrene, α-methylstyrene, divinylbenzene, 1,1-diphenylethylene, N,N-diethyl-p-aminoethylstyrene, vinyltoluene, etc. Examples of conjugated diene compounds include butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, etc.

[0013] The modification of a carboxyl group-containing styrene elastomer can be carried out, for example, by copolymerizing an unsaturated carboxylic acid during polymerization of the styrene elastomer, or by heating and kneading the styrene elastomer and the unsaturated carboxylic acid in the presence of an organic peroxide. Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, itaconic acid, fumaric acid, maleic anhydride, and itaconic anhydride. The amount of modification with the unsaturated carboxylic acid is preferably 0.1 to 10% by mass. The acid value of the carboxyl group-containing styrene elastomer is preferably 0.1 to 30 mgKOH / g, and more preferably 0.5 to 25 mgKOH / g. When this acid value is 0.1 mgKOH / g or more, the adhesive composition cures sufficiently, and good adhesion and heat resistance are obtained. On the other hand, when the acid value is 25 mgKOH / g or less, the cohesive strength of the adhesive composition is suppressed, resulting in excellent adhesion and electrical properties.

[0014] The weight-average molecular weight of the carboxyl group-containing styrene elastomer is preferably 10,000 to 500,000, more preferably 30,000 to 300,000, and even more preferably 50,000 to 200,000. If the weight-average molecular weight is equal to or greater than the lower limit, excellent adhesiveness can be exhibited, and the coatability when dissolved in a solvent and applied is also improved. If the weight-average molecular weight is equal to or less than the upper limit, compatibility with epoxy resins is improved. The weight average molecular weight is a value obtained by converting the molecular weight measured by gel permeation chromatography (hereinafter also referred to as "GPC") into polystyrene equivalent.

[0015] Specific examples of carboxy group-containing styrene-based elastomers include those obtained by modifying styrene-butadiene block copolymers, styrene-ethylene propylene block copolymers, styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene block copolymers, styrene-ethylenebutylene-styrene block copolymers, and styrene-ethylenepropylene-styrene block copolymers with unsaturated carboxylic acids. These carboxyl group-containing styrene elastomers may be used alone or in combination of two or more. Among the above copolymers, styrene-ethylenebutylene-styrene block copolymers and styrene-ethylenepropylene-styrene block copolymers are preferred from the viewpoints of adhesiveness and electrical properties. Furthermore, the mass ratio of styrene / ethylenebutylene in the styrene-ethylenebutylene-styrene block copolymer and the mass ratio of styrene / ethylenepropylene in the styrene-ethylenepropylene-styrene block copolymer are preferably 10 / 90 to 50 / 50, and more preferably 20 / 80 to 40 / 60. When the mass ratios are within these ranges, an adhesive composition with excellent adhesive properties can be obtained.

[0016] The content of the carboxyl group-containing styrene elastomer is preferably less than 50 parts by mass per 100 parts by mass of the solid content of the adhesive composition. If the content of the carboxyl group-containing styrene elastomer is too high, it is not possible to improve the adhesion (tackiness) in the lamination step.

[0017] <Carboxy-free styrene elastomer> Compared to the carboxyl group-containing styrene elastomers, the carboxyl group-free styrene elastomers have a lower cohesive strength and a lower modulus of elasticity in the high temperature range above the glass transition point due to the absence of carboxy group interaction. Therefore, by including a carboxyl group-free styrene elastomer in the adhesive composition, the adhesiveness of the adhesive layer is improved, and the adhesiveness (tackiness) in the lamination process in particular can be improved. The carboxy-free styrene-based elastomer is a copolymer of a conjugated diene compound and an aromatic vinyl compound, mainly consisting of block and random structures, and a hydrogenated product thereof. Such elastomers are not modified with an unsaturated carboxylic acid. The types of aromatic vinyl compounds and conjugated diene compounds constituting the styrene-based elastomer, and specific examples of the styrene-based elastomer are as described above in the section <Carboxy group-containing styrene-based elastomer>.

[0018] The content of the carboxy-free styrene-based elastomer is preferably 30 to 70 parts by mass per 100 parts by mass of the solid content of the adhesive composition. If the content of the carboxy-free styrene-based elastomer is equal to or greater than the lower limit, the adhesion (tackiness) of the laminate is improved. On the other hand, if the content is equal to or less than the upper limit, the curable components can be sufficiently blended, ensuring heat resistance.

[0019] <Epoxy resin> The epoxy resin is a component that reacts with the carboxy group in the carboxy group-containing styrene elastomer, thereby imparting high adhesiveness to adherends and heat resistance to the cured adhesive.

[0020] Examples of epoxy resins include bisphenol A type epoxy resins, bisphenol F type epoxy resins, and hydrogenated versions thereof; glycidyl ester-based epoxy resins such as phthalic acid diglycidyl ester, isophthalic acid diglycidyl ester, terephthalic acid diglycidyl ester, p-hydroxybenzoic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, succinic acid diglycidyl ester, adipic acid diglycidyl ester, sebacic acid diglycidyl ester, and trimellitic acid triglycidyl ester; ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, and the like. Examples of epoxy resins that can be used include, but are not limited to, glycidyl ether-based epoxy resins such as glycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, tetraphenylglycidyl ether ethane, triphenylglycidyl ether ethane, sorbitol polyglycidyl ether, and polyglycerol polyglycidyl ether; glycidyl amine-based epoxy resins such as triglycidyl isocyanurate and tetraglycidyldiaminodiphenylmethane; and linear aliphatic epoxy resins such as epoxidized polybutadiene and epoxidized soybean oil. Additionally, novolac-type epoxy resins such as xylene structure-containing novolac epoxy resins, naphthol novolac-type epoxy resins, phenol novolac epoxy resins, o-cresol novolac epoxy resins, and bisphenol A novolac epoxy resins can also be used.

[0021] Further, examples of epoxy resins that can be used include brominated bisphenol A type epoxy resins, phosphorus-containing epoxy resins, fluorine-containing epoxy resins, dicyclopentadiene skeleton-containing epoxy resins, naphthalene skeleton-containing epoxy resins, anthracene type epoxy resins, tertiary butylcatechol type epoxy resins, triphenylmethane type epoxy resins, tetraphenylethane type epoxy resins, biphenyl type epoxy resins, bisphenol S type epoxy resins, etc. These epoxy resins may be used alone or in combination of two or more. Among the above epoxy resins, epoxy resins without hydroxyl groups are preferred because they provide adhesive compositions with excellent electrical properties and have good compatibility with styrene-based elastomers. In particular, novolac epoxy resins and epoxy resins such as those shown in the following structures are more preferred because they have a moderately flexible backbone, making the cured product less susceptible to brittle fracture, improving the stability of the performance of the cured product of the adhesive composition over long-term use, and also improving heat resistance due to their high number of functional groups.

[0022] [ka] (R is a structure containing methylene-aryl-methylene or a structure containing an aliphatic hydrocarbon structure having 6 or more carbon atoms, and examples of aryl include benzene, xylene, naphthalene, and biphenyl, while examples of aliphatic hydrocarbon include hexane, dimethylcyclohexane, and dicyclopentadiene.) Specific examples of novolac epoxy resins include "YX7700" (xylene structure-containing novolac epoxy resin) manufactured by Mitsubishi Chemical Corporation, "NC7000L" (naphthol novolac epoxy resin) manufactured by Nippon Kayaku Co., Ltd., "ESN485" (naphthol novolac epoxy resin) manufactured by Nippon Steel Chemical & Material Co., Ltd., "N-690" (cresol novolac epoxy resin) manufactured by DIC Corporation, and "N-695" (cresol novolac epoxy resin) manufactured by DIC Corporation.

[0023] Furthermore, epoxy resins containing amino groups can improve workability by shortening the curing time and lowering the curing temperature due to the catalytic action of the amino groups. In addition, the inclusion of amine groups improves adhesion to metal layers. In particular, it is more preferable that the epoxy resin is a glycidylamine-type epoxy resin. Glycidylamine-type epoxy resins are multifunctional, allowing them to cure in small amounts, and because they contain amines in their molecular skeleton, they have good compatibility with amino-group-containing styrene-based elastomers and also have a reaction-accelerating effect. Furthermore, because they contain amine groups, they can improve adhesion to metal layers. Specific examples of glycidylamine-type epoxy resins include tetraglycidyldiaminodiphenylmethane, such as "jER604" manufactured by Mitsubishi Chemical Corporation, "Sumiepoxy ELM434" manufactured by Sumitomo Chemical Co., Ltd., "Araldite MY720," "Araldite MY721," "Araldite MY9512," "Araldite MY9612," "Araldite MY9634," and "Araldite MY9663" manufactured by Huntsman Advanced Materials, Inc., and "TETRAD-X" and "TETRAD-C" manufactured by Mitsubishi Gas Chemical Company, Inc.

[0024] The epoxy resin used in the present invention preferably has two or more epoxy groups in one molecule. This is because a crosslinked structure is formed by reaction with the carboxyl group-containing styrene-based elastomer, thereby enabling high heat resistance to be achieved. Furthermore, when an epoxy resin with two or more epoxy groups is used, the degree of crosslinking with the carboxyl group-containing styrene-based elastomer is sufficient, resulting in sufficient heat resistance.

[0025] The content of the epoxy resin is preferably 1 to 20 parts by mass per 100 parts by mass of the solid content of the adhesive composition. If the content of the epoxy resin is equal to or greater than the lower limit, the adhesive composition will cure sufficiently and good heat resistance and chemical resistance can be ensured. On the other hand, if the content of the epoxy resin is high, adhesion will decrease, so if the content is equal to or less than the upper limit, good adhesion can be ensured. If the content of the epoxy resin is high, it will be difficult to improve adhesion (tackiness) during the lamination process.

[0026] The softening point or melting point of the epoxy resin is preferably not more than 90° C. When the softening point or melting point of the epoxy resin is not more than 90° C., the elastic modulus of the adhesive composition before curing in the high temperature range can be reduced, and the elastic modulus of the adhesive composition after curing in the normal temperature range (room temperature) can be increased.

[0027] <Other ingredients> In addition to the above-mentioned carboxyl group-containing styrene-based elastomer, carboxyl group-free styrene-based elastomer, and epoxy resin, the adhesive composition may contain other thermoplastic resins other than the carboxyl group-containing styrene-based elastomer and the carboxyl group-free styrene-based elastomer, tackifiers, flame retardants, curing agents, curing accelerators, coupling agents, heat aging inhibitors, leveling agents, antifoaming agents, inorganic fillers, pigments, solvents, and the like, to the extent that the functionality of the adhesive composition is not affected.

[0028] A more preferred embodiment of the adhesive composition containing other components is, for example, an adhesive composition containing an organic peroxide, which makes it possible to crosslink styrene-based elastomers that do not contain carboxy groups, thereby further improving the heat resistance and chemical resistance of the adhesive layer. As the organic peroxide, those generally known as radical polymerization initiators can be used, and examples thereof include organic peroxides such as benzoyl peroxide, lauroyl peroxide, t-butyl peroxypivalate, t-butylperoxyethylhexanoate, 1,1'-bis-(t-butylperoxy)cyclohexane, t-amylperoxy-2-ethylhexanoate, and t-hexylperoxy-2-ethylhexanoate.

[0029] Among the other components, examples of the other thermoplastic resins include phenoxy resins, polyamide resins, polyester resins, polycarbonate resins, polyphenylene oxide resins, polyurethane resins, polyacetal resins, polyethylene-based resins, polypropylene-based resins, polyvinyl-based resins, etc. These thermoplastic resins may be used alone or in combination of two or more.

[0030] Examples of the tackifier include coumarone-indene resins, terpene resins, terpene-phenol resins, rosin resins, pt-butylphenol-acetylene resins, phenol-formaldehyde resins, xylene-formaldehyde resins, petroleum-based hydrocarbon resins, hydrogenated hydrocarbon resins, turpentine-based resins, etc. These tackifiers may be used alone or in combination of two or more.

[0031] The flame retardant may be either an organic flame retardant or an inorganic flame retardant. Examples of organic flame retardants include phosphorus-based flame retardants such as melamine phosphate, melamine polyphosphate, guanidine phosphate, guanidine polyphosphate, ammonium phosphate, ammonium polyphosphate, ammonium amido phosphate, ammonium amido polyphosphate, carbamate phosphate, carbamate polyphosphate, aluminum trisdiethylphosphinate, aluminum trismethylethylphosphinate, aluminum trisdiphenylphosphinate, zinc bisdiethylphosphinate, zinc bismethylethylphosphinate, zinc bisdiphenylphosphinate, titanyl bisdiethylphosphinate, titanium tetrakisdiethylphosphinate, titanyl bismethylethylphosphinate, titanium tetrakismethylethylphosphinate, titanyl bisdiphenylphosphinate, and titanium tetrakisdiphenylphosphinate; nitrogen-based flame retardants such as triazine-based compounds such as melamine, melam, and melamine cyanurate, cyanuric acid compounds, isocyanuric acid compounds, triazole-based compounds, tetrazole compounds, diazo compounds, and urea; and silicon-based flame retardants such as silicone compounds and silane compounds. Examples of inorganic flame retardants include metal hydroxides such as aluminum hydroxide, magnesium hydroxide, zirconium hydroxide, barium hydroxide, and calcium hydroxide; metal oxides such as tin oxide, aluminum oxide, magnesium oxide, zirconium oxide, zinc oxide, molybdenum oxide, and nickel oxide; zinc carbonate, magnesium carbonate, barium carbonate, zinc borate, and hydrated glass. Two or more of these flame retardants can be used in combination.

[0032] Examples of the curing agent include, but are not limited to, amine-based curing agents and acid anhydride-based curing agents. Examples of the amine-based curing agent include melamine resins such as methylated melamine resin, butylated melamine resin, and benzoguanamine resin, dicyandiamide, and 4,4'-diphenyldiaminosulfone. Examples of the acid anhydride include aromatic acid anhydrides and aliphatic acid anhydrides. These curing agents may be used alone or in combination of two or more. The content of the curing agent is preferably 0.5 to 100 parts by mass, and more preferably 5 to 70 parts by mass, relative to 100 parts by mass of the adhesive composition.

[0033] The curing accelerator is used for the purpose of accelerating the reaction between the carboxyl group-containing styrene-based elastomer and the epoxy resin, and examples of the curing accelerator that can be used include tertiary amine-based curing accelerators, tertiary amine salt-based curing accelerators, and imidazole-based curing accelerators.

[0034] Examples of tertiary amine curing accelerators include benzyldimethylamine, 2-(dimethylaminomethyl)phenol, 2,4,6-tris(dimethylaminomethyl)phenol, tetramethylguanidine, triethanolamine, N,N'-dimethylpiperazine, triethylenediamine, and 1,8-diazabicyclo[5.4.0]undecene.

[0035] Examples of the tertiary amine salt curing accelerator include formate, octylate, p-toluenesulfonate, o-phthalate, phenolate, and phenol novolac resin salt of 1,8-diazabicyclo[5.4.0]undecene; and formate, octylate, p-toluenesulfonate, o-phthalate, phenolate, and phenol novolac resin salt of 1,5-diazabicyclo[4.3.0]nonene.

[0036] Imidazole-based curing accelerators include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-methyl-4-ethylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 2,4-diamino-6-[2'-methylimidazolyl-(1')]ethyl-s-triazine, 2,4-diamino-6-[2' 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, etc. These curing accelerators may be used alone or in combination of two or more.

[0037] When the adhesive composition contains a curing accelerator, the content of the curing accelerator is preferably 0.05 to 10 parts by mass, and more preferably 0.1 to 5 parts by mass, per 100 parts by mass of the adhesive composition. When the content of the curing accelerator is within the above range, the reaction between the carboxyl group-containing styrene-based elastomer and the epoxy resin, and the reaction between epoxy resins themselves, can proceed easily, making it easier to ensure adhesiveness and heat resistance.

[0038] Examples of the coupling agent include silane-based coupling agents such as vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-ureidopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, 3-isocyanatopropyltriethoxysilane, and imidazole silane; titanate-based coupling agents; aluminate-based coupling agents; and zirconium-based coupling agents. These may be used alone or in combination of two or more.

[0039] Examples of the heat aging inhibitor include 2,6-di-tert-butyl-4-methylphenol, n-octadecyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate, tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane, pentaerythritol tetrakis[3-(3,5-di-t-butyl-4-hydroxyphenol], triethylene glycol-bis[3 Examples of antioxidants include phenol-based antioxidants such as 3-(3-t-butyl-5-methyl-4-hydroxyphenyl)propionate, sulfur-based antioxidants such as dilauryl-3,3'-thiodipropionate and dimyristyl-3,3'-dithiopropionate, and phosphorus-based antioxidants such as trisnonylphenyl phosphite and tris(2,4-di-tert-butylphenyl)phosphite. These antioxidants may be used alone or in combination of two or more.

[0040] Examples of the inorganic filler include powders of titanium oxide, aluminum oxide, zinc oxide, carbon black, silica, talc, copper, silver, etc. These may be used alone or in combination of two or more.

[0041] (adhesive layer) The adhesive layer of the present invention comprises the adhesive composition of the present invention. The adhesive composition that forms the adhesive layer is allowed to cure. The curing method is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include thermal curing. The thickness of the adhesive layer is not particularly limited and can be appropriately selected depending on the purpose, but is preferably 3 to 100 μm, more preferably 5 to 70 μm, and even more preferably 10 to 50 μm.

[0042] <Method of manufacturing adhesive layer> An adhesive layer can be produced by forming the adhesive composition into a film. The adhesive composition can be produced by mixing a carboxyl group-containing styrene-based elastomer, a carboxyl group-free styrene-based elastomer, an epoxy resin, and other components. The mixing method is not particularly limited as long as the adhesive composition is homogeneous. Since the adhesive composition is preferably used in the form of a solution or dispersion, a solvent is usually also used. Examples of solvents include alcohols such as methanol, ethanol, isopropyl alcohol, n-propyl alcohol, isobutyl alcohol, n-butyl alcohol, benzyl alcohol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, and diacetone alcohol; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclohexanone, and isophorone; aromatic hydrocarbons such as toluene, xylene, ethylbenzene, and mesitylene; esters such as methyl acetate, ethyl acetate, ethylene glycol monomethyl ether acetate, and 3-methoxybutyl acetate; and aliphatic hydrocarbons such as hexane, heptane, cyclohexane, and methylcyclohexane. These solvents may be used alone or in combination of two or more. When the adhesive composition is a solution or dispersion (resin varnish) containing a solvent, it can be smoothly applied to a substrate film and an adhesive layer can be formed, and an adhesive layer of the desired thickness can be easily obtained. When the adhesive composition contains a solvent, the solid content is preferably 3 to 80% by mass, more preferably 10 to 50% by mass, from the viewpoint of workability including the formation of the adhesive layer. When the solid content is 80% by mass or less, the viscosity of the solution is appropriate, and uniform application is easy. In a more specific embodiment of the method for producing an adhesive layer, a resin varnish containing the adhesive composition and a solvent is applied to the surface of a substrate film to form a resin varnish layer, and then the solvent is removed from the resin varnish layer to form a B-stage adhesive layer. Here, the B-stage adhesive layer refers to an adhesive composition in an uncured state or a semi-cured state in which a portion of the adhesive composition has begun to cure, and refers to a state in which the curing of the adhesive composition progresses further by heating or the like. Here, the method for applying the resin varnish onto the substrate film is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include spraying, spin coating, dipping, roll coating, blade coating, doctor roll method, doctor blade method, curtain coating, slit coating, screen printing, inkjet method, and dispensing method. The adhesive layer in the B-stage state can be further subjected to heating or the like to form a cured adhesive layer.

[0043] <Characteristics of the adhesive layer> The adhesive layer of the present invention has a storage modulus of 1×10 at 120°C before curing. 3 Pa or more 5×10 5 It is preferable that the pressure is 0.01 Pa or less. Storage modulus is 5×10 5 If the elastic modulus is less than 1 Pa, the adhesive layer will be more likely to adhere to the substrate film and other components related to the electronic part because the storage modulus is low at the temperature during the lamination process.

[0044] [Storage modulus (Pa)] The storage modulus of the adhesive layer can be determined, for example, by preparing a 100 μm thick adhesive film from a sample made of the adhesive layer and measuring it using a viscoelasticity measuring device (RSA-G2 manufactured by TA Instruments) under conditions of a measurement frequency of 1 Hz and a temperature rise rate of 5° C. / min in accordance with JIS K7244.

[0045] The adhesive layer of the present invention has a storage modulus of 8×10 at 25° C. after curing. 7 Pa or more 5×10 9 It is preferable that the pressure is 0.01 Pa or less. Storage modulus is 8×10 7 When the storage modulus is at least 1 Pa, the adhesive layer has a high storage modulus at room temperature, and therefore can maintain adhesion to the substrate film and other components related to electronic parts.

[0046] The adhesive layer of the present invention obtained by curing the adhesive composition preferably has a relative dielectric constant (εr) of 3.5 or less and a dielectric loss tangent (tanδ) of 0.01 or less, measured at a frequency of 28 GHz. If the relative dielectric constant is 3.5 or less and the dielectric loss tangent is 0.01 or less, the material can be suitably used in FPC-related products, which have strict requirements for electrical properties.

[0047] [Dielectric constant and dielectric loss tangent] The relative dielectric constant and dielectric tangent of the adhesive layer can be measured using the open resonator method at a temperature of 23°C and a frequency of 28 GHz using a network analyzer MS46122B (manufactured by Anritsu) and an open resonator Fabry-Perot DPS-03 (manufactured by KEYCOM).

[0048] (Laminate) The laminate of the present invention comprises a substrate film and the above-described adhesive layer on at least one surface of the substrate film.

[0049] <Base film> The substrate film used in the present invention can be selected depending on the application of the laminate. For example, when the laminate is used as a coverlay film or a copper-clad laminate (CCL), examples of the substrate film include polyimide film, polyether ether ketone film, polyphenylene sulfide film, aramid film, polyethylene naphthalate film, and liquid crystal polymer film. Among these, polyimide film, polyether ether ketone (PEEK) film, polyethylene naphthalate film, and liquid crystal polymer film are preferred from the viewpoints of adhesiveness and electrical properties.

[0050] Furthermore, when the laminate of the present invention is used as a bonding sheet, the base film must be a release film, such as polyethylene terephthalate film, polyethylene film, polypropylene film, silicone release-treated paper, polyolefin resin-coated paper, TPX (polymethylpentene) film, and fluorine-based resin film.

[0051] When the laminate of the present invention is used as a shielding film, the substrate film must be a film having electromagnetic wave shielding properties, and examples thereof include a laminate of a protective insulating layer and a metal foil.

[0052] (Coverlay film) A preferred embodiment of the laminate according to the present invention is a coverlay film. When manufacturing FPCs, a laminate with an adhesive layer called a "coverlay film" is usually used to protect the wiring. This coverlay film has an insulating resin layer and an adhesive layer formed on its surface. For example, a coverlay film is a laminate in which the adhesive layer is formed on at least one surface of the base film, and peeling of the base film and the adhesive layer is generally difficult. The thickness of the base film included in the coverlay film is preferably 5 to 100 μm, more preferably 5 to 50 μm, and even more preferably 5 to 30 μm. If the thickness of the base film is equal to or less than the upper limit, the coverlay film can be made thinner. If the thickness of the base film is equal to or more than the lower limit, the printed wiring board can be easily designed and handled. As a method for producing a coverlay film, for example, a resin varnish containing the adhesive composition and a solvent is applied to the surface of the base film to form a resin varnish layer, and then the solvent is removed from the resin varnish layer, thereby producing a coverlay film having a B-stage adhesive layer formed thereon. The drying temperature when removing the solvent is preferably 40 to 250°C, more preferably 70 to 170°C. Drying is carried out by passing the laminate coated with the adhesive composition through a furnace in which hot air drying, far infrared heating, high frequency induction heating, or the like is performed. If necessary, a release film may be laminated on the surface of the adhesive layer for storage, etc. As the release film, known films such as polyethylene terephthalate film, polyethylene film, polypropylene film, silicone release-treated paper, polyolefin resin-coated paper, TPX film, and fluorine-based resin film can be used. The coverlay film according to the present invention uses the low-dielectric adhesive composition of the present invention, which enables high-speed transmission in electronic devices and also provides excellent adhesion stability to electronic devices.

[0053] (Bonding sheet) A preferred embodiment of the laminate according to the present invention is a bonding sheet. The bonding sheet is one in which the above-mentioned adhesive layer is formed on the surface of a release film (substrate film). The bonding sheet may also be in a form in which the adhesive layer is provided between two release films. When using the bonding sheet, the release film is peeled off. The release film may be the same as that described above in the (coverlay film) section. The thickness of the substrate film included in the bonding sheet is preferably 5 to 100 μm, more preferably 25 to 75 μm, and even more preferably 38 to 50 μm. If the thickness of the substrate film is within the above range, the bonding sheet is easy to manufacture and easy to handle. A bonding sheet can be produced, for example, by applying a resin varnish containing the adhesive composition and a solvent to the surface of a release film and drying it in the same manner as in the case of the coverlay film. The bonding sheet according to the present invention uses the low-dielectric adhesive composition of the present invention, which enables high-speed transmission in electronic devices and also provides excellent adhesive stability to electronic devices.

[0054] (Copper-clad laminate (CCL)) A preferred embodiment of the laminate according to the present invention is a copper-clad laminate obtained by laminating a copper foil to the adhesive layer in the laminate according to the present invention. A copper-clad laminate is formed by laminating a copper foil to the above-mentioned laminate, and is composed of, for example, a base film, an adhesive layer, and a copper foil in this order. The adhesive layer and the copper foil may be formed on both sides of the base film. The adhesive composition used in the present invention also has excellent adhesion to articles containing copper. The copper-clad laminate of the present invention uses the low-dielectric adhesive composition of the present invention, and therefore enables high-speed transmission in electronic devices and has excellent adhesive stability.

[0055] A method for producing a copper-clad laminate includes, for example, bringing the adhesive layer of the laminate and copper foil into surface contact, performing thermal lamination at 80°C to 150°C, and then curing the adhesive layer by after-curing. The after-curing conditions can be, for example, 100°C to 200°C in an inert gas atmosphere for 30 minutes to 4 hours. The copper foil is not particularly limited, and electrolytic copper foil, rolled copper foil, etc. can be used.

[0056] (Printed wiring board) A preferred embodiment of the laminate of the present invention is a printed wiring board obtained by laminating copper wiring to the adhesive layer in the laminate of the present invention. A printed wiring board can be obtained by forming an electronic circuit on the copper-clad laminate. The printed wiring board is formed by bonding a base film and copper wiring using the laminate, and is composed of the base film, adhesive layer, and copper wiring in that order. The adhesive layer and copper wiring may be formed on both sides of the base film. For example, a printed wiring board is manufactured by using a heat press or the like to attach a coverlay film via an adhesive layer to a surface having wiring portions. The printed wiring board according to the present invention uses the low-dielectric adhesive composition of the present invention, and therefore enables high-speed transmission in electronic devices and has excellent adhesive stability. The printed wiring board according to the present invention can be produced, for example, by contacting the adhesive layer of the laminate with copper wiring, performing thermal lamination at 80°C to 150°C, and then curing the adhesive layer by after-curing. The after-curing conditions can be, for example, 100°C to 200°C and 30 minutes to 4 hours. The shape of the copper wiring is not particularly limited, and may be selected as desired.

[0057] (Shielding film) A preferred embodiment of the laminate according to the present invention is a shielding film. Shielding film is a film used to shield various electronic devices, such as computers, mobile phones, and analytical equipment, in order to cut out electromagnetic noise that can affect these devices and cause them to malfunction. It is also called electromagnetic wave shielding film. The electromagnetic wave shielding film is formed by laminating, for example, an insulating resin layer, a metal layer, and the adhesive layer of the present invention in this order. The shielding film of the present invention uses the low-dielectric adhesive composition of the present invention, which enables high-speed transmission in electronic devices and also provides excellent adhesion stability to electronic devices.

[0058] (Printed wiring board with shielding film) A preferred embodiment of the laminate according to the present invention is a printed wiring board with a shielding film. A printed wiring board with a shielding film is a printed wiring board having a printed circuit provided on at least one surface of the substrate, and the electromagnetic wave shielding film is attached to the printed wiring board. A printed wiring board with a shielding film includes, for example, a printed wiring board, an insulating film adjacent to the surface of the printed wiring board on which the printed circuit is provided, and the electromagnetic wave shielding film. The printed wiring board with a shielding film according to the present invention uses the low-dielectric adhesive composition of the present invention, and therefore enables high-speed transmission in electronic devices and has excellent adhesive stability. [Example]

[0059] The present invention will be described in further detail below with reference to examples, but the scope of the present invention is not limited to these examples. In the following, parts and percentages are by weight unless otherwise specified.

[0060] (Carboxylic group-containing styrene elastomer) We used "Tuftec M1911" (maleic acid-modified styrene-ethylene butylene-styrene block copolymer) manufactured by Asahi Kasei Corporation. The copolymer had an acid value of 2 mg KOH / g, a styrene / ethylene butylene ratio of 30 / 70, and a weight-average molecular weight of 69,000. (Carboxy-free styrene elastomer) The copolymer used was "Tuftec P1500" (hydrogenated styrene-based elastomer) manufactured by Asahi Kasei Corporation. The acid value of this copolymer was 0 mgKOH / g, the styrene / ethylene-butylene ratio was 30 / 70, and the weight-average molecular weight was 67,000. (epoxy resin) The product used was "YX7700" (epoxy resin, softening point 65°C) manufactured by Mitsubishi Chemical Corporation. (Perbutyl E) As the organic peroxide, a peroxyester manufactured by NOF Corporation under the trade name "Perbutyl E" was used. (solvent) A mixed solvent of toluene and methyl ethyl ketone (mass ratio = 90:10) was used. (Base film) As the substrate film, "Shin-Etsu Sepla Film PEEK" (polyether ether ketone, thickness 50 μm) manufactured by Shin-Etsu Polymer Co., Ltd. was used. (electrolytic copper foil) The electrolytic copper foil used was "TQ-M7-VSP" manufactured by Mitsui Mining & Smelting Co., Ltd. (electrolytic copper foil, thickness 12 μm, shiny side Rz 1.27 μm, shiny side Ra 0.197 μm, shiny side Rsm 12.95 μm). The surface roughness of the shiny side was measured using a laser microscope and calculated from the roughness curve in accordance with JIS B 0601:2013 (ISO 4287:1997 Amd.1:2009). (Release film) As the release film, NP75SA (silicone release PET film, 50 μm) manufactured by Panac Corporation was used.

[0061] Example 1 The components constituting the adhesive layer shown in Table 1 were contained in the proportions shown in Table 1, and these components were dissolved in a solvent to prepare a resin varnish with a solid content concentration of 20 mass %. The surface of the substrate film was subjected to a corona treatment. The resin varnish was applied to the surface of a substrate film, dried in an oven at 110°C for 4 minutes, and the toluene was volatilized to form an adhesive layer, resulting in an adhesive-attached substrate film. The adhesive layer of the adhesive laminate was placed in contact with the shiny side of the electrolytic copper foil, and thermal lamination was performed at 120°C to obtain a pre-cured adhesive laminate. The pre-cured adhesive laminate was further after-cured at 150°C for 60 minutes to cure the adhesive layer, resulting in a cured adhesive laminate. The adhesive strength (N / cm) between the electrolytic copper foil and the base film of the adhesive laminate before curing and the adhesive laminate after curing of Example 1 was measured.

[0062] [Adhesion strength (N / cm)] The adhesion strength was measured by cutting the pre-curing adhesive laminate and the post-curing adhesive laminate into 25 mm wide test specimens, and measuring the peel strength when peeling the electrolytic copper foil from the adhesive-attached substrate film fixed to a support at a peel speed of 0.3 m / min and a peel angle of 180° in accordance with JIS Z0237:2009 (Test methods for adhesive tapes and adhesive sheets).

[0063] Furthermore, the storage modulus (Pa) of the adhesive layer of Example 1 at 120°C before curing and at 25°C after curing were also measured.

[0064] [Storage modulus (Pa)] The storage modulus of the adhesive layer was measured using a viscoelasticity measuring device (RSA-G2 manufactured by TA Instruments) at a measurement frequency of 1 Hz and a heating rate of 5°C / min according to JIS K7244. For the measurement sample, a resin varnish was roll-coated onto a release film. The coated film was then placed in an oven and dried at 110°C for 4 minutes to form a B-stage adhesive layer (50 μm thick). The adhesive layers were then thermally laminated at 120°C so that the adhesive surfaces were in contact with each other to form a pre-cured adhesive film (100 μm thick). This pre-cured adhesive film (100 μm thick) was placed in an oven and subjected to a heat-curing treatment at 150°C for 60 minutes to produce a cured adhesive film (100 mm x 100 mm). The release film was then peeled off from the adhesive film, and the storage modulus (Pa) of the adhesive layer was measured.

[0065] The relative permittivity and dielectric loss tangent at a frequency of 28 GHz of the adhesive layer in the laminate of Example 1 were also measured.

[0066] [Dielectric constant and dielectric loss tangent] The dielectric constant and dielectric loss tangent of the adhesive layer were measured using an open-type resonator (open-type resonator) with a network analyzer MS46122B (manufactured by Anritsu) and a Fabry-Perot DPS-03 (manufactured by KEYCOM) at a temperature of 23°C and a frequency of 28 GHz. The measurement sample was prepared by roll-coating a resin varnish onto a release film. The coated film was then placed in an oven and dried at 110°C for 4 minutes to form a B-stage adhesive layer (50 μm thick). The adhesive layers were then thermally laminated at 120°C so that the adhesive surfaces were in contact with each other to form a pre-cured adhesive film (100 μm thick). This pre-cured adhesive film (100 μm thick) was then placed in an oven and heat-cured at 150°C for 60 minutes to produce a cured adhesive film (100 mm x 100 mm). After curing, the release film was peeled off from the adhesive film, and the relative dielectric constant and dielectric loss tangent of the adhesive layer were measured.

[0067] The measurement results are shown in Table 1.

[0068] (Examples 2 to 5) Laminates of Examples 2 to 5 were produced in the same manner as in Example 1, except that the types and amounts of components constituting the adhesive layer in Example 1 were changed as shown in Table 1. The laminate thus produced was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0069] (Comparative Examples 1 to 4) Laminates of Comparative Examples 1 to 4 were prepared in the same manner as in Example 1, except that the types and amounts of components constituting the adhesive layer were changed as shown in Table 1. The laminate thus produced was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0070] [Table 1] As shown in Examples 1 to 5, the adhesive layer made of the adhesive composition of the present invention not only has excellent adhesion (adhesion) after heat curing, but also has excellent adhesion (adhesion) in the lamination process.

[0071] This application claims priority based on Japanese Patent Application No. 2019-230539, filed on December 20, 2019, and incorporates the entire contents of that Japanese Patent Application by reference. [Industrial Applicability]

[0072] Laminates having an adhesive layer made of the adhesive composition of the present invention can be suitably used in the production of FPC-related products for electronic devices such as smartphones, mobile phones, optical modules, digital cameras, game consoles, laptops, and medical devices.

Claims

1. An adhesive composition containing a carboxyl group-containing styrene-based elastomer, a carboxyl group-free styrene-based elastomer, and an epoxy resin, the content of the carboxyl group-containing styrene-based elastomer is less than 50 parts by mass per 100 parts by mass of the solid content of the adhesive composition, the content of the carboxy-free styrene-based elastomer is 30 parts by mass to 70 parts by mass per 100 parts by mass of the solid content of the adhesive composition; The adhesive composition, wherein the content of the epoxy resin is 1 to 20 parts by mass per 100 parts by mass of the solid content of the adhesive composition.

2. 2. The adhesive composition according to claim 1, wherein the softening point or melting point of the epoxy resin is 90°C or lower.

3. The adhesive composition according to any one of claims 1 to 2, further comprising an organic peroxide.

4. An adhesive layer made of the adhesive composition according to any one of claims 1 to 3, wherein the storage modulus of the adhesive layer at 120°C before curing is 5 x 10 ５ The adhesive layer has a viscosity of 0.1 Pa or less.

5. An adhesive layer comprising the adhesive composition according to any one of claims 1 to 3, wherein the adhesive layer is heat-cured at 150°C for 60 minutes, and the storage modulus at 25°C after curing of the adhesive layer measured from a cured adhesive film is 8 x 10 ７ The adhesive layer has a viscosity of 100 Pa or more.

6. An adhesive layer comprising the adhesive composition according to any one of claims 1 to 3, wherein the adhesive layer has a relative dielectric constant of 3.5 or less and a dielectric loss tangent of 0.01 or less at a frequency of 28 GHz, as measured on a cured adhesive film obtained by heat-curing the adhesive layer at 150°C for 60 minutes.

7. A base film; A laminate comprising an adhesive layer made of the adhesive composition according to any one of claims 1 to 3, or the adhesive layer according to any one of claims 4 to 6.

8. The laminate according to claim 7 , wherein the substrate film contains a polyether ether ketone (PEEK) resin.

9. A coverlay film with an adhesive layer, comprising the laminate according to claim 7 or 8.

10. A copper clad laminate comprising the laminate according to claim 7 or 8.

11. A printed wiring board comprising the laminate according to claim 7 or 8.

12. A shielding film comprising the laminate according to claim 7 or 8.

13. A printed wiring board with a shielding film, comprising the laminate according to claim 7 or 8.

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