Adhesive composition, adhesive sheet, and laminate

Abstract

To provide an adhesive composition which has excellent adhesion and, furthermore, maintains superior adhesion even after long-term exposure to a high-temperature and high-humidity environment, and to provide an adhesive sheet and a laminate including the adhesive composition.SOLUTION: An adhesive composition contains a polyester resin (A), an epoxy resin (B) and an isocyanate compound (C), and satisfies the following requirements (1) to (2). (1) A content of a polyester resin (a1) having a glass transition temperature of 50°C or higher in the polyester resin (A) is 30 mass% or more. (2) The epoxy resin (B) contains an epoxy resin (b1) having a nitrogen atom and an epoxy resin (b2) having no nitrogen atom.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an adhesive composition and an adhesive sheet and a laminate using the same, and more particularly to an adhesive composition used for bonding a resin substrate to another resin substrate or a metal substrate. [Background technology]

[0002] In recent years, efforts have been made to increase the range of electric vehicles by installing more batteries in vehicles and increasing battery capacity. To dissipate heat from the batteries, metal components such as aluminum alloys, which act as heat dissipation materials, and insulating resin substrates (e.g., polyethylene terephthalate substrates and polyimide substrates) are bonded together around these batteries. Adhesives are used in this process, and in particular for automotive applications, long-term resistance to humidity and heat is required in addition to adhesive properties.

[0003] Copolymer polyesters are widely used in a variety of applications, including coatings and adhesives, due to the ease of molecular design through the selection and combination of polycarboxylic acids and polyhydric alcohols, and the ability to freely control molecular weight. Adhesives using copolymer polyesters have excellent adhesion (peel strength) to metals, including copper and aluminum alloys, and have been used with a curing agent as an adhesive between metal and polyimide film, such as in adhesives for flexible printed circuit boards (FPCs) (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Tokuhei 6-104813 [Patent Document 2] Patent Publication No. 2021-66865 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the adhesives using the copolymerized polyesters described in Patent Documents 1 and 2 do not have the high adhesiveness and long-term moist heat resistance required for automotive applications.

[0006] The present invention has been made in view of the above-mentioned problems in the prior art. That is, an object of the present invention is to provide an adhesive composition that has excellent adhesive properties and that maintains excellent adhesive properties even after prolonged exposure to a high-temperature, high-humidity environment, as well as an adhesive sheet and a laminate that contain the same. [Means for solving the problem]

[0007] As a result of extensive research, the present inventors have found that the above problems can be solved by the following means, and have arrived at the present invention. That is, the present invention has the following configuration.

[0008] [1] An adhesive composition comprising a polyester resin (A), an epoxy resin (B), and an isocyanate compound (C), and satisfying the following requirements (1) and (2): (1) The content of the polyester resin (a1) having a glass transition temperature of 50°C or higher in the polyester resin (A) is 30% by mass or higher. (2) The epoxy resin (B) contains an epoxy resin (b1) having a nitrogen atom and an epoxy resin (b2) not having a nitrogen atom. [2] The adhesive composition according to [1], wherein the acid value of the polyester resin (A) is 50 eq / t or more and 400 eq / t or less. [3] The adhesive composition according to [1] or [2], wherein the softening point of the epoxy resin (B) is 60°C or lower. [4] The adhesive composition according to any one of [1] to [3], wherein the content of the isocyanate compound (C) is 0.1 to 4 parts by mass per 100 parts by mass of the polyester resin (A). [5] The adhesive composition according to any one of [1] to [4], wherein the isocyanate compound (C) is an isocyanate compound having no aromatic ring. [6] The adhesive composition according to any one of [1] to [5], which contains at least one flame retardant. [7] An adhesive sheet containing the adhesive composition according to any one of [1] to [6]. [8] A laminate comprising the adhesive composition according to any one of [1] to [6]. [Effects of the Invention]

[0009] The adhesive composition of the present invention has excellent peel strength and moist heat resistance, and the storage stability of the semi-cured coating film is also excellent. Therefore, it is suitable for heat dissipation in automotive applications, adhesives around insulating materials, adhesive sheets, and laminates. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will be described in detail below, however, the present invention is not limited to this embodiment and can be practiced in various modified forms within the scope of the description.

[0011] The adhesive composition of the present invention contains a polyester resin (A), an epoxy resin (B), and an isocyanate compound (C), wherein the polyester resin (A) contains 30% by mass or more of a polyester resin (a1) having a glass transition temperature of 50°C or higher, and the epoxy resin (B) contains an epoxy resin (b1) having a nitrogen atom and an epoxy resin (b2) having no nitrogen atom. The adhesive composition of the present invention is characterized by containing a predetermined amount of polyester resin (a1) having a glass transition temperature of 50°C or higher as the polyester resin (A), and using it in combination with three types of curing agents: epoxy resin (b1), epoxy resin (b2), and an isocyanate compound. In adhesives that use a polyester resin as the base resin in combination with a curing agent, there is a trade-off between moist heat resistance and peel strength, making it difficult to achieve both of these performance characteristics at high levels. In the present invention, by using a combination of an epoxy resin (b1) having a nitrogen atom, an epoxy resin (b2) having no nitrogen atom, and an isocyanate compound, it is possible to adjust the reaction rate and thereby adjust the degree of curing when used as an adhesive sheet.

[0012] In this specification, the terms "branch" and "branched structure" refer to a branched structure in a polymer chain, and specifically refer to a structure in which three or more branches (molecular chains) extend from one structural unit that constitutes the molecular chain of a polyester resin. In other words, a polyester resin having a branched structure means, for example, that the polymer molecular chain of the polyester resin has a triester structure, a tetraester structure, or a pentaester structure.

[0013] <Polyester resin (A)> The polyester resin (A) used in the present invention contains 30% by mass or more, preferably 50% by mass or more, more preferably 65% ​​by mass or more, even more preferably 75% by mass or more, and particularly preferably 85% by mass or more, of a polyester resin (a1) having a glass transition temperature of 50° C. or higher. By containing the polyester resin (a1) in the polyester resin (A) of the adhesive composition within the above range, the adhesive composition has good moist heat resistance.

[0014] The glass transition temperature of the polyester resin (a1) is 50°C or higher, preferably 55°C or higher, and more preferably 60°C or higher. It is also preferably 120°C or lower, more preferably 100°C or lower, and even more preferably 90°C or lower. Within the above range, an adhesive composition having excellent adhesion and excellent resistance to moist heat can be obtained. The polyester resin may be either a crystalline resin or an amorphous resin, but is preferably an amorphous resin.

[0015] The polyester resin (A) used in the present invention has a chemical structure obtained by polycondensation of a polycarboxylic acid component and a polyhydric alcohol component, and the polycarboxylic acid component and the polyhydric alcohol component each consist of one or more selected components.

[0016] The polycarboxylic acid component constituting the polyester resin (A) is not limited, but the following polycarboxylic acids or their esters and anhydrides can be used. Specific examples of polycarboxylic acids include aromatic polycarboxylic acids, aliphatic polycarboxylic acids, and alicyclic polycarboxylic acids. Examples of aromatic polycarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid, hexahydrophthalic acid, 2,5-furandicarboxylic acid, 5-sodium sulfodimethylisophthalic acid, and hydrogenated naphthalenedicarboxylic acid. Examples of aliphatic polycarboxylic acids include adipic acid, sebacic acid, dimer acid, succinic acid, fumaric acid, and maleic acid. Examples of alicyclic polycarboxylic acids include 1,3-cyclohexanedicarboxylic acid and 1,4-cyclohexanedicarboxylic acid. Aromatic polycarboxylic acid components are particularly preferred, and aromatic dicarboxylic acids are more preferred. Among these, naphthalenedicarboxylic acid, terephthalic acid, and isophthalic acid are more preferred as aromatic dicarboxylic acids. Use of an aromatic polycarboxylic acid can improve the moist heat resistance of the adhesive composition.

[0017] The polyester resin (A) preferably contains aromatic polycarboxylic acids in an amount of 50 mol % or more, more preferably 65 mol % or more, even more preferably 75 mol % or more, and particularly preferably 85 mol % or more, when the total amount of structural units derived from polyhydric alcohols is 100 mol %.

[0018] The polyhydric alcohol component constituting the polyester resin (A) is not particularly limited, and examples thereof include aliphatic polyhydric alcohols, alicyclic polyhydric alcohols, and aromatic polyhydric alcohols. Examples of the aliphatic polyhydric alcohols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 2-methyl-1,3-hexanediol, 2-methyl-2-ethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, and 2-ethyl-2-n-propyl- Examples of suitable polyhydric alcohols include 1,3-propanediol, 2,2-di-n-propyl-1,3-propanediol, 2-n-butyl-2-ethyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, mannitol, sorbitol, dimer diol, pentaerythritol, and polyalkylene glycols (e.g., polytetramethylene glycol, polyethylene glycol, and polypropylene glycol). Examples of suitable polyhydric alcohols include 1,4-cyclohexanedimethanol, tricyclodecane dimethanol, and α-methylglucose. Examples of suitable polyhydric alcohols include diphenolic acid. One or more of these may be used. Preferred are aliphatic polyhydric alcohols and / or alicyclic polyhydric alcohols, more preferably aliphatic dihydric alcohols and / or alicyclic dihydric alcohols. Preferably, the aliphatic polyhydric alcohol is not a polyalkylene glycol. Among these, preferred aliphatic polyhydric alcohols include ethylene glycol, 1,2-propanediol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, and neopentyl glycol, and preferred alicyclic polyhydric alcohols include 1,4-cyclohexanedimethanol and tricyclodecanedimethanol, and the use of these can improve the moist heat resistance of the adhesive composition.

[0019] The polyhydric alcohol component used in the polyester resin (a1) is preferably an aliphatic polyhydric alcohol and / or an alicyclic polyhydric alcohol, more preferably an aliphatic dihydric alcohol and / or an alicyclic dihydric alcohol, and the aliphatic polyhydric alcohol is preferably not a polyalkylene glycol. Among these, the aliphatic polyhydric alcohols are preferably ethylene glycol, 1,2-propanediol, 2-methyl-1,3-propanediol, 3-methyl-1,5-pentanediol, and neopentyl glycol, and the alicyclic polyhydric alcohols are preferably 1,4-cyclohexanedimethanol and tricyclodecanedimethanol, and the use of these can improve the moist heat resistance of the adhesive composition.

[0020] The aliphatic polyhydric alcohol used in the polyester resin (a1) preferably contains a component having a side chain. An aliphatic dihydric alcohol is more preferred. The side chain is composed of carbon and hydrogen. Examples of the component include 1,2-propylene glycol, 2-methyl-1,3-propanediol, neopentyl glycol, 1,2-butanediol, 1,3-butanediol, 1,4-pentanediol, 1,3-pentanediol, 1,2-hexanediol, 3-methyl-1,5-pentanediol, 2,4-diethyl-1,5-pentanediol, 1-methyl-1,8-octanediol, 3-methyl-1,6-hexanediol, 4-methyl-1,7-heptanediol, 4-methyl-1,8-octanediol, and 4-propyl-1,8-octanediol.

[0021] When the polyester resin (a1) contains the aliphatic polyhydric alcohol having the side chain, the content is preferably 20 mol% or more, more preferably 30 mol% or more, even more preferably 40 mol% or more, and particularly preferably 50 mol% or more, based on 100 mol% of the polyhydric alcohol component, and is preferably 80 mol% or less, more preferably 75 mol% or less, even more preferably 70 mol% or less, and particularly preferably 65 mol% or less.

[0022] As the polyhydric alcohol component used in the polyester resin (a1), it is preferable to use a combination of an aliphatic polyhydric alcohol and an alicyclic polyhydric alcohol, and it is more preferable to use a combination of an aliphatic dihydric alcohol and an alicyclic dihydric alcohol. The alicyclic polyhydric alcohol is preferably contained in an amount of 5 mol% or more, more preferably 10 mol% or more, and even more preferably 20 mol% or more, based on 100 mol% of the polyhydric alcohol component. Furthermore, it is preferably 40 mol% or less, more preferably 35 mol% or less, and even more preferably 30 mol% or less.

[0023] The polyester resin (A) used in the present invention can also be copolymerized with a component having a total of three functional groups per molecule, including hydroxyl and / or carboxyl groups, as structural units. The carboxyl groups may be acid anhydride groups, and acid anhydride groups are counted as bifunctional. The three functional groups may be all carboxyl groups, all hydroxyl groups, or both carboxyl and hydroxyl groups. Examples of such components include trimellitic acid, 4-hydroxyphthalic acid and their anhydrides, diphenolic acid, dimethylolbutanoic acid, dimethylolpropionic acid, trimesic acid, glycerin, trimethylolpropane, and trimethylolethane. Trimellitic acid, 4-hydroxyphthalic acid and their anhydrides, and diphenolic acid are preferred, and copolymerization of these compounds can exhibit excellent moist heat resistance. While the reason for this is unclear, it is believed that introducing branches with trifunctional components into a relatively low-molecular-weight polyester resin results in a cured coating film that can build a high crosslink density, thereby improving moist heat resistance. The trifunctional component is preferably 0.5 mol % or more, more preferably 1 mol % or more, and even more preferably 1.5 mol % or more, when the total amount of all components of the polyester resin (A) is 100 mol %. From the viewpoint of preventing gelation during polymerization, the trifunctional component is preferably 10 mol % or less, more preferably 5 mol % or less, and even more preferably 3 mol % or less.

[0024] The polyester resin (A) used in the present invention can also be copolymerized with a tetrafunctional or higher polycarboxylic acid component and / or a tetrafunctional or higher polyhydric alcohol component. Examples of tetrafunctional or higher polycarboxylic acid components include aromatic carboxylic acids such as pyromellitic acid, benzophenonetetracarboxylic acid, and pyromellitic anhydride (PMDA), and aliphatic carboxylic acids such as 1,2,3,4-butanetetracarboxylic acid, and these can be used alone or in combination of two or more. Examples of tetrahydric or higher polyhydric alcohol components include pentaerythritol, α-methylglucose, mannitol, and sorbitol, and these can be used alone or in combination of two or more. The component used for the purpose of introducing branches is preferably a tetrafunctional or lower component, more preferably a trifunctional component.

[0025] The polyester resin (A) used in the present invention can also be copolymerized with lactone or lactam, for example, ε-caprolactone or ε-caprolactam.

[0026] The polyester resin (A) used in the present invention can be made from raw materials derived from biomass resources. Biomass resources include the stored materials obtained by converting solar energy into starch, cellulose, etc. through photosynthesis in plants, the bodies of animals that grow by eating plants, and products made by processing plants or animals. Among these, plant resources are more preferred, including wood, rice straw, rice husks, rice bran, used rice, corn, sugarcane, cassava, sago palm, soybean pulp, corn cob, tapioca dregs, bagasse, vegetable oil cakes, potatoes, buckwheat, soybeans, oils and fats, waste paper, papermaking residues, seafood residues, livestock excrement, sewage sludge, and food waste. Corn, sugarcane, cassava, and sago palm are even more preferred.

[0027] Examples of methods for the polymerization condensation reaction to produce the polyester resin (A) used in the present invention include: 1) a method in which a polycarboxylic acid and a polyhydric alcohol are heated in the presence of a known catalyst, followed by a dehydration esterification step and then a polyhydric alcohol removal / polycondensation reaction; 2) a method in which an alcohol ester of a polycarboxylic acid and a polyhydric alcohol are heated in the presence of a known catalyst, followed by a transesterification step and then a polyhydric alcohol removal / polycondensation reaction; and 3) a method in which depolymerization is performed. In the methods 1) and 2), part or all of the acid component may be replaced with an acid anhydride.

[0028] When producing the polyester resin (A) used in the present invention, conventional polymerization catalysts can be used, such as titanium compounds such as tetra-n-butyl titanate, tetraisopropyl titanate, titanium oxyacetylcetonate, and tetrabutyl orthotitanate; antimony compounds such as antimony trioxide and tributoxyantimony; germanium compounds such as germanium oxide and tetra-n-butoxygermanium; and acetates of magnesium, iron, zinc, manganese, cobalt, and aluminum. These catalysts can be used alone or in combination. From the standpoint of product hygiene and safety, it is preferable not to use heavy metals, and it is particularly preferable to use titanium compounds such as tetra-n-butyl titanate, tetraisopropyl titanate, titanium oxyacetylcetonate, and tetrabutyl orthotitanate.

[0029] The polyester resin (A) used in the present invention preferably contains a polyester resin having an acid value of 50 eq / t or more, more preferably 70 eq / t or more, and even more preferably 80 eq / t or more. It is also preferably 400 eq / t or less, more preferably 300 eq / t or less, and even more preferably 200 eq / t or less. When the polyester resin (A) of the adhesive composition contains a polyester resin having an acid value equal to or greater than the above-mentioned lower limit, it is possible to form a coating film with a high crosslink density with the epoxy resin (B). When the polyester resin (A) contains a polyester resin having an acid value equal to or less than the above-mentioned upper limit, it is possible to achieve good adhesion and moist heat resistance. Furthermore, when multiple polyester resins are blended, the acid value of the polyester resin (A) is the weighted average of the acid values ​​of the blended polyester resins.

[0030] The polyester resin (a1) used in the present invention preferably contains a polyester resin having an acid value of 50 eq / t or more, more preferably 60 eq / t or more, and even more preferably 70 eq / t or more, and preferably 400 eq / t or less, more preferably 300 eq / t or less, even more preferably 200 eq / t or less, and particularly preferably 150 eq / t or less.

[0031] The polyester resin (A) can be given an acid value by any method. Methods for giving an acid value include a method of adding a compound having a polycarboxylic anhydride group in the molecule in the later stage of polycondensation, and a method of increasing the acid value at the prepolymer (oligomer) stage and then polycondensing this to obtain a polyester resin having an acid value. The former method of adding a compound is preferred because of its ease of operation and the ease of obtaining the target acid value.

[0032] Among the compounds having a polyvalent carboxylic acid anhydride group in the molecule for imparting an acid value to the polyester resin (A), examples of carboxylic acid monoanhydrides include phthalic anhydride, succinic anhydride, maleic anhydride, trimellitic anhydride, itaconic anhydride, and citraconic anhydride. Among these, trimellitic anhydride is preferred from the viewpoints of versatility and economy. Among compounds having a polyvalent carboxylic acid anhydride group in the molecule for imparting an acid value to a polyester resin, examples of carboxylic acid polyanhydrides include pyromellitic anhydride, 1,2,3,4-butanetetracarboxylic acid dianhydride, 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride, 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, ethylene glycol bistrimellitate dianhydride, and 2,2',3,3'-biphenyltetracarboxylic acid dianhydride. Of these, ethylene glycol bistrimellitate dianhydride is preferred from the standpoints of versatility and economy. The carboxylic acid monoanhydrides and carboxylic acid polyanhydrides may be used singly or in combination of two or more kinds.

[0033] The reduced viscosity of the polyester resin (A) of the present invention is preferably from 0.2 to 0.8 dl / g, more preferably from 0.3 to 0.7 dl / g, and even more preferably from 0.4 to 0.6 dl / g.

[0034] The content of polyester resin (A) in the adhesive composition of the present invention is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more, based on 100% by mass of the solid content of the adhesive composition. It is also preferably 99% by mass or less, more preferably 98% by mass or less. A content within the above range is preferred because it results in good adhesion and moist heat resistance.

[0035] <Epoxy resin (B)> The adhesive composition of the present invention contains an epoxy resin (B), which must contain at least one of the following: an epoxy resin (b1) containing a nitrogen atom and an epoxy resin (b2) not containing a nitrogen atom. The term "epoxy resin" is not particularly limited as long as it contains at least one epoxy group in the molecule. The combined use of the epoxy resin (b1) containing a nitrogen atom and the epoxy resin (b2) not containing a nitrogen atom allows for adjustment of the reaction rate, resulting in excellent curing properties with polyester resins and good resistance to moist heat.

[0036] The epoxy resin (B) preferably has a softening point of 60° C. or less, more preferably 50° C. or less, as determined by the ring and ball method of JIS K 7234. When the softening point is within this range, the coating film has excellent flexibility and reactivity with polyester resins, and the adhesion and moist heat resistance are also good.

[0037] <Epoxy resin (b1)> The nitrogen-containing epoxy resin (b1) used in the present invention has a higher reactivity with polyester resins than other epoxy resins because the nitrogen atoms in its skeleton have catalytic activity. This high reactivity allows the adhesive composition to harden to a certain extent when applied to a substrate and dried, preventing resin outflow when the composition is bonded to a substrate or the like. Furthermore, the composition can be hardened with a relatively short curing time after bonding, resulting in good adhesion.

[0038] Specific examples of the nitrogen atom-containing epoxy resin (b1) include glycidylamine-type epoxy resins and triazine derivative epoxy resins, with glycidylamine-type epoxy resins being preferred for achieving the effects of the present invention more significantly. Specific examples of the glycidylamine type epoxy resin include aliphatic glycidylamine type epoxy resins, alicyclic glycidylamine type epoxy resins, and aromatic glycidylamine type epoxy resins. Examples of the alicyclic glycidylamine type epoxy resin include 1,3-bis(diglycidylaminomethyl)cyclohexane, and examples of the aromatic glycidylamine type epoxy resin include N,N-diglycidylaniline, N,N-diglycidyl-o-toluidine, N,N,O-triglycidyl-p-aminophenol, N,N,O-triglycidyl-4-amino-3-methylphenol, N,N,N',N'-tetraglycidyl-(4,4'-methylenebisaniline), N,N,N',N'-tetraglycidyl-2,2'-diethyl-4,4'-methylenedianiline, and N,N,N',N'-tetraglycidyl-m-xylylenediamine. Among these, N,N,N',N'-tetraglycidyl-m-xylylenediamine is preferred.Specific examples of triazine derivative epoxy resins include 1,3,5-triglycidyl isocyanurate.

[0039] The nitrogen-containing epoxy resin (b1) is preferably a trifunctional or higher functional resin, more preferably a tetrafunctional or higher functional resin, and the number of nitrogen atoms in the resin skeleton may be at least one, but may be two or more.

[0040] <Epoxy resin (b2)> The nitrogen-free epoxy resin (b2) used in the present invention is not particularly limited as long as it has an epoxy group in the molecule and does not have a nitrogen atom in its skeleton, but preferably has two or more epoxy groups in the molecule. Specifically, it is not particularly limited, but at least one selected from the group consisting of biphenyl-type epoxy resins, naphthalene-type epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, novolac-type epoxy resins, alicyclic epoxy resins, dicyclopentadiene-type epoxy resins, dimer acid-modified epoxy resins, and epoxy-modified polybutadienes can be used. The inclusion of the nitrogen-free epoxy resin (b2) controls reactivity and allows for a stronger crosslinking structure between the polyester resin and the isocyanate compound (C) than when only the nitrogen-containing epoxy resin (b1) is used as the epoxy resin (B), thereby improving the moist heat resistance of the cured adhesive composition.

[0041] In the adhesive composition of the present invention, the content of the epoxy resin (B) is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, relative to 100 parts by mass of the polyester resin (A). When the content is equal to or greater than the lower limit, a sufficient curing effect can be obtained, and excellent adhesive properties can be exhibited. Furthermore, the content is preferably 20 parts by mass or less, more preferably 10 parts by mass or less. When the content is equal to or less than the upper limit, the moist heat resistance is improved. In other words, by keeping the content within the above range, an adhesive composition with even better adhesive properties and moist heat resistance can be obtained.

[0042] In the adhesive composition of the present invention, the ratio of the epoxy equivalent of the epoxy resin (B) to the acid value of the polyester resin (A) is preferably 0.8 or more, more preferably 1.0 or more, and even more preferably 1.3 or more. It is also preferably 10.0 or less, more preferably 6.0 or less, and even more preferably 5.0 or less. By adjusting the ratio to be equal to or greater than the lower limit, the moist heat resistance is improved. In other words, by adjusting the ratio within the above range, an adhesive composition with better adhesion and moist heat resistance can be obtained.

[0043] The content of the nitrogen-containing epoxy resin (b1) per 100 parts by mass of the epoxy resin (B) is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 45 parts by mass or more, and is preferably 85 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 70 parts by mass or less.

[0044] <Isocyanate compound (C)> The adhesive composition of the present invention must contain an isocyanate compound (C), which reacts with the hydroxyl terminal of the polyester resin to form a stronger coating film with improved adhesion and moist heat resistance.Examples of the isocyanate compound (C) include 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, polymethylene polyphenyl polyisocyanate (also called polymeric MDI or crude MDI), 1,3-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-toluidine diisocyanate, 2, Aromatic diisocyanates such as 4,6-triisocyanate toluene, 1,3,5-triisocyanate benzene, dianisidine diisocyanate, 4,4'-diphenyl ether diisocyanate, 4,4',4"-triphenylmethane triisocyanate, etc.; aromatic aliphatic diisocyanates (aliphatic isocyanates having one or more aromatic rings in the molecule) such as m- or p-xylylene diisocyanate (also known as XDI) and α,α,α',α'-tetramethylxylylene diisocyanate (also known as TMXDI); trimethylene diisocyanate; tetramethylene diisocyanate; Aliphatic diisocyanates such as diisocyanates, hexamethylene diisocyanate (also known as HDI), pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, isophorone diisocyanate (also known as IPDI), 1,3-cyclopentane diisocyanate, 1,3-cyclohexyl Examples of the polyisocyanate include alicyclic diisocyanates such as methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), and 1,4-bis(isocyanatomethyl)cyclohexane; biuret, nurate, adduct, allophanate, carbodiimide-modified, and uretdione-modified products of these diisocyanates; and urethane prepolymers obtained by reacting these polyisocyanates with polyols.Furthermore, blocked isocyanates in which the isocyanate moiety of the isocyanate compound is blocked with a low-molecular-weight compound can also be used. From the viewpoints of reactivity with polyester resins, adhesiveness, and moist heat resistance, blocked isocyanates and those having a structure that does not contain an aromatic ring are preferred. The preferred isocyanate compound (C) is, for example, one or more selected from the group consisting of an adduct of hexamethylene diisocyanate, an isocyanurate of hexamethylene diisocyanate, a biuret of hexamethylene diisocyanate, an adduct of isophorone diisocyanate, an isocyanurate of isophorone diisocyanate, and a biuret of isophorone diisocyanate. Among these, the adduct of hexamethylene diisocyanate, the isocyanurate of hexamethylene diisocyanate, and the biuret of hexamethylene diisocyanate are particularly preferred from the viewpoint of adhesiveness.

[0045] In the adhesive composition of the present invention, the content of the isocyanate compound (C) is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and particularly preferably 1 part by mass or more, relative to 100 parts by mass of the polyester resin (A). By ensuring that the content is at least the above-mentioned lower limit, a sufficient curing effect can be obtained, and excellent adhesion and moist heat resistance can be exhibited. Furthermore, the content is preferably 4 parts by mass or less, more preferably 3.5 parts by mass or less, even more preferably 3 parts by mass or less, and particularly preferably 2.5 parts by mass or less. By ensuring that the content is at most the above-mentioned upper limit, the stability of the adhesive composition is improved, and sufficient performance can be exhibited even after the dried coating film is stored under certain conditions. In other words, by ensuring that the content is within the above range, an adhesive composition can be obtained that has better adhesion, moist heat resistance, and excellent storage stability.

[0046] <Organic solvents> The adhesive composition of the present invention may further contain an organic solvent. The organic solvent used in the present invention is not particularly limited as long as it dissolves the polyester resin, epoxy resin, and isocyanate compound. Specific examples of the organic solvent include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as hexane, heptane, octane, and decane; alicyclic hydrocarbons such as cyclohexane, cyclohexene, methylcyclohexane, and ethylcyclohexane; halogenated hydrocarbons such as trichloroethylene, dichloroethylene, chlorobenzene, and chloroform; alcoholic solvents such as methanol, ethanol, isopropyl alcohol, butanol, pentanol, hexanol, propanediol, and phenol; acetone, methyl isobutyl ketone, methyl ethyl ketone, pentanone, hexanone, cyclohexanone, isophorone, and acetophenone. Ketone solvents, cellosolves such as methyl cellosolve and ethyl cellosolve, ester solvents such as methyl acetate, ethyl acetate, butyl acetate, methyl propionate and butyl formate, glycol ether solvents such as ethylene glycol mono-n-butyl ether, ethylene glycol mono-iso-butyl ether, ethylene glycol mono-tert-butyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-iso-butyl ether, triethylene glycol mono-n-butyl ether and tetraethylene glycol mono-n-butyl ether, and the like, can be used alone or in combination of two or more. Methyl ethyl ketone, toluene and cyclohexanone are particularly preferred from the viewpoint of working environment and drying properties.

[0047] The organic solvent is preferably in the range of 100 to 1000 parts by mass per 100 parts by mass of the total of the polyester resin (A), the epoxy resin (B), and the isocyanate compound (C). By setting the amount to be equal to or greater than the lower limit, the liquid state and pot life are improved. On the other hand, by setting the amount to be equal to or less than the upper limit, it is advantageous in terms of production costs and transportation costs.

[0048] The adhesive composition of the present invention may further contain other components as needed, such as a flame retardant, a tackifier, a filler, and a silane coupling agent.

[0049] <Flame retardant> The adhesive composition of the present invention may optionally contain a flame retardant. Examples of flame retardants include bromine-based, phosphorus-based, nitrogen-based, and metal hydroxide compounds. Phosphorus-based flame retardants are preferred, and known phosphorus-based flame retardants such as phosphate esters (e.g., trimethyl phosphate, triphenyl phosphate, tricresyl phosphate), phosphate salts (e.g., aluminum phosphinate), and phosphazenes can be used. These flame retardants may be used alone or in any combination of two or more. When a flame retardant is added, it is preferably contained in an amount of 1 to 200 parts by mass, more preferably 5 to 150 parts by mass, and most preferably 10 to 100 parts by mass, per 100 parts by mass of the polyester resin (A), epoxy resin (B), and isocyanate compound (C) combined. By maintaining the amount within this range, flame retardancy can be achieved while maintaining adhesion and solder heat resistance.

[0050] <Tackifier> The adhesive composition of the present invention may optionally contain a tackifier. Examples of tackifiers include polyterpene resins, rosin-based resins, aliphatic petroleum resins, alicyclic petroleum resins, copolymerized petroleum resins, styrene resins, and hydrogenated petroleum resins. These tackifiers are used to improve adhesive strength. They may be used alone or in any combination of two or more. When a tackifier is added, it is preferably contained in an amount ranging from 1 to 200 parts by mass, more preferably from 5 to 150 parts by mass, and most preferably from 10 to 100 parts by mass, per 100 parts by mass of the polyester resin (A), epoxy resin (B), and isocyanate compound (C) combined. By using the tackifier within this range, the effects of the tackifier can be exhibited while maintaining adhesion and solder heat resistance.

[0051] <Filler> The adhesive composition of the present invention may contain a filler as needed. Examples of organic fillers include powders of heat-resistant resins such as polyimide, polyamideimide, fluororesin, and liquid crystal polyester. Examples of inorganic fillers include silica (SiO), alumina (AlO), titania (TiO), tantalum oxide (TaO), zirconia (ZrO), silicon nitride (SiN), boron nitride (BN), calcium carbonate (CaCO), calcium sulfate (CaSO), zinc oxide (ZnO), magnesium titanate (MgO·TiO), barium sulfate (BaSO), organic bentonite, clay, mica, aluminum hydroxide, and magnesium hydroxide. Among these, silica is preferred due to its ease of dispersion and improved heat resistance. While hydrophobic and hydrophilic silica are commonly known as silica, hydrophobic silica treated with dimethyldichlorosilane, hexamethyldisilazane, octylsilane, or the like is preferred here for its moisture absorption resistance. When silica is added, the amount is preferably 0.05 to 30 parts by mass per 100 parts by mass of the polyester resin (A), epoxy resin (B), and isocyanate compound (C) combined. By adjusting the amount to above the lower limit, further heat resistance can be achieved. By adjusting the amount to below the upper limit, poor dispersion of the silica and excessively high solution viscosity can be prevented, improving workability.

[0052] <Silane coupling agent> A silane coupling agent may be blended into the adhesive composition of the present invention as needed. The inclusion of a silane coupling agent is highly preferred because it improves adhesion to metals and heat resistance. The silane coupling agent is not particularly limited, but examples include those containing unsaturated groups, epoxy groups, and amino groups. Among these, silane coupling agents containing epoxy groups, such as γ-glycidoxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltriethoxysilane, are more preferred from the perspective of heat resistance. When a silane coupling agent is blended, its amount is preferably 0.5 to 20 parts by mass per 100 parts by mass of the total of the polyester resin (A), epoxy resin (B), and isocyanate compound (C). By using a silane coupling agent within this range, solder heat resistance and adhesion can be improved.

[0053] <Laminate> The laminate of the present invention is a substrate to which an adhesive composition is laminated (a two-layer laminate of substrate / adhesive layer), or a substrate is further attached (a three-layer laminate of substrate / adhesive layer / substrate). Here, the adhesive layer refers to the layer of adhesive composition remaining after the adhesive composition of the present invention is applied to a substrate and dried. The laminate of the present invention can be obtained by applying the adhesive composition of the present invention to various substrates according to a conventional method, drying it, and then laminating another substrate on it.

[0054] <Base material> In the present invention, the substrate is not particularly limited as long as it is possible to apply the adhesive composition of the present invention to the substrate and dry it to form an adhesive layer. Examples of the substrate include resin substrates such as film-like resins, metal substrates such as metal plates and metal foils, and paper.

[0055] Examples of the resin substrate include polyester resin, polyamide resin, polyimide resin, polyamideimide resin, liquid crystal polymer, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resin, and fluorine-based resin. A film-like resin (hereinafter also referred to as a substrate film layer) is preferred.

[0056] Any conventionally known conductive material can be used as the metal substrate. Examples of the material include various metals such as SUS, copper, aluminum, iron, steel, zinc, and nickel, as well as their alloys, plated products, and metals treated with other metals such as zinc or chromium compounds. Copper and aluminum alloys are preferred.

[0057] Examples of the paper include fine paper, kraft paper, roll paper, glassine paper, etc. Examples of the composite material include glass epoxy, etc.

[0058] In terms of adhesive strength with the adhesive composition and durability, the substrate is preferably a polyester resin, a polyamide resin, a polyimide resin, a polyamideimide resin, a liquid crystal polymer, polyphenylene sulfide, syndiotactic polystyrene, a polyolefin resin, a fluorine-based resin, a SUS steel plate, a copper foil, aluminum, or a glass epoxy.

[0059] <Adhesive sheet> In the present invention, the adhesive sheet is formed by laminating the laminate and a release substrate via an adhesive composition. Specific configurations include substrate / adhesive layer / release substrate, or release substrate / adhesive layer / substrate / adhesive layer / release substrate. Laminating the release substrate functions as a protective layer for the substrate. Furthermore, by using a release substrate, the release substrate can be released from the adhesive sheet and the adhesive layer can be transferred to another substrate.

[0060] The adhesive sheet of the present invention can be obtained by applying the adhesive composition of the present invention to various laminates and drying them according to conventional methods. Furthermore, by attaching a release substrate to the adhesive layer after drying, the adhesive can be wound up without causing offset onto the substrate, resulting in excellent operability, and the adhesive layer is protected, resulting in excellent storage stability and ease of use. Furthermore, after application to a release substrate and drying, the adhesive layer itself can be transferred to another substrate by attaching another release substrate as needed.

[0061] <Release base material> The release substrate is not particularly limited, but examples include paper such as fine paper, kraft paper, roll paper, and glassine paper, with coating layers of clay, polyethylene, polypropylene, or other filler on both sides, and then a silicone-based, fluorine-based, or alkyd-based release agent coated on each of these coating layers. Other examples include various olefin films such as polyethylene, polypropylene, ethylene-α-olefin copolymer, and propylene-α-olefin copolymer alone, and films such as polyethylene terephthalate coated with the above-mentioned release agent. Due to factors such as the release force between the release substrate and the adhesive layer and the adverse effect of silicone on electrical properties, it is preferable to use a polypropylene-sealed film on both sides of fine paper and then apply an alkyd-based release agent thereon, or an alkyd-based release agent on polyethylene terephthalate.

[0062] In the present invention, the method for coating the adhesive composition onto a substrate is not particularly limited, but examples include a comma coater and a reverse roll coater. Alternatively, the adhesive layer can be formed directly or by a transfer method, as needed. The thickness of the adhesive layer after drying can be appropriately adjusted as needed, but is preferably in the range of 5 to 200 μm. By making the adhesive film thickness 5 μm or more, sufficient adhesive strength can be obtained. Furthermore, by making it 200 μm or less, it becomes easier to control the amount of residual solvent during the drying process, and blisters are less likely to occur when the film is attached to the substrate. The drying conditions are not particularly limited, but the residual solvent ratio after drying is preferably 1% by mass or less. By making it 1% by mass or less, foaming of the residual solvent is suppressed when the film is attached to the substrate, and blisters are less likely to occur. <Laminate>

[0063] The laminate according to the present invention can be produced, for example, by laminating the adhesive sheet to various substrates. Any lamination method can be used, for example, lamination using a press or roll. The two materials can also be laminated while heating, using a heated press or a heated roll device. Lamination using a roll is preferred to increase productivity. Lamination using a roll requires achieving various performance properties, including peel strength, through pressure bonding in a shorter time than with a press. The adhesive sheet according to the present invention can achieve high peel strength even when laminating using a roll, by adjusting the reactivity depending on the composition of the adhesive composition. [Example]

[0064] The present invention will be described in more detail below with reference to examples. In these examples and comparative examples, "parts" simply refers to parts by mass.

[0065] (Physical property evaluation method) (Measurement of polyester resin composition) A polyester resin sample was dissolved in deuterated chloroform and analyzed using a BRUKER AVANCE-NEO600 nuclear magnetic resonance (NMR) analyzer. 1 H-NMR analysis or 13 C-NMR analysis was performed. The molar ratio was calculated from the ratio of the integral values. In Table 1, when the acid value of the polyester resin was increased by post-acid addition, the molar ratio of each component is shown with the total of the polycarboxylic acid components other than the acid component used in the post-acid addition being set at 100 mol %.

[0066] (Measurement of reduced viscosity (unit: dl / g)) 0.1 g of a polyester resin sample was dissolved in 25 cc of a mixed solvent of phenol / tetrachloroethane (mass ratio 6 / 4), and the viscosity was measured at a measurement temperature of 30°C using an Ubbelohde viscometer.

[0067] (Measurement of glass transition temperature (unit: °C)) Measurement was performed using a differential scanning calorimeter (DSC-200, manufactured by SII Corporation). 5 mg of the sample (polyester resin) was placed in an aluminum container with a lid, sealed, and cooled to -50°C using liquid nitrogen. The sample was then heated to 150°C at a heating rate of 20°C / min. The glass transition temperature was determined as the temperature at the intersection of the extension of the baseline before the endothermic peak (below the glass transition temperature) and the tangent to the endothermic peak (the tangent showing the maximum slope from the rising part of the peak to the peak peak) in the endothermic curve obtained during the heating process.

[0068] (Acid value measurement (unit: eq / t)) 0.2 g of a polyester resin sample was dissolved in 40 ml of chloroform and titrated with 0.01 N potassium hydroxide ethanol solution to obtain 10% of the polyester resin. 6 The equivalent weight per gram (eq / t) was calculated. Phenolphthalein was used as the indicator. The acid value of polyester resin (A) was calculated as the weighted average of the acid values ​​of the polyester resins added.

[0069] (Measurement of softening point (°C) of epoxy resin (B)) The softening point of the epoxy resin (B) was measured by the ring and ball method of JIS K 7234.

[0070] The following describes an example of synthesis of the polyester resin used in the present invention.

[0071] (Production Example of Polyester Resin (A-1)) A reactor equipped with a stirrer, condenser, and thermometer was charged with 211 parts of terephthalic acid, 8 parts of trimellitic anhydride, 462 parts of isophthalic acid, 84 parts of ethylene glycol, 345 parts of neopentyl glycol, 212 parts of 1,4-cyclohexanedimethanol, and 0.025 mol% of tetrabutyl orthotitanate as a catalyst relative to the total polycarboxylic acid components. The temperature was raised from 160°C to 240°C over 4 hours, and an esterification reaction was carried out through a dehydration process. Next, the polycondensation reaction step was carried out by reducing the pressure inside the system to 5 mmHg over 20 minutes and then further increasing the temperature to 250°C. The pressure was then reduced to 0.3 mmHg or less, and the polycondensation reaction was carried out until the desired viscosity was reached. The system was then cooled to 220°C while flowing nitrogen, and 8 parts of trimellitic anhydride were added. The reaction was allowed to proceed for 30 minutes, and the mixture was then removed. Composition analysis of the obtained polyester resin (A-1) by NMR revealed that it was a copolymer polyester with a molar ratio of terephthalic acid / trimellitic anhydride / isophthalic acid / ethylene glycol / neopentyl glycol / 1,4-cyclohexanedimethanol / trimellitic anhydride (post-added) = 31 / 1 / 68 / / 10 / 60 / 30 / / / 1. The glass transition temperature was 64°C, the reduced viscosity was 0.57 dl / g, and the acid value was 85 eq / t.

[0072] (Production Examples of Polyester Resins (A-2) to (A-4)) According to the production example of polyester resin (A-1), polyester resins (A-2) to (A-4) having the compositions shown in Table 1 were synthesized by changing the types and blending ratios of raw materials. The results are shown in Table 1.

[0073] [Table 1]

[0074] The following describes examples of producing adhesive compositions according to the present invention and comparative examples. The epoxy resin (B) and the isocyanate compound (C) used were as follows: Epoxy resin (b1): Glycidylamine type epoxy (Tetrad X (Mitsubishi Gas Chemical Company, Inc.)) Epoxy resin (b2): Phenol novolac epoxy resin (jER (registered trademark) 152 (manufactured by Mitsubishi Chemical Corporation)) Isocyanate compound (C): Aliphatic polyisocyanate (isocyanurate of hexamethylene diisocyanate, Desmodur (registered trademark) N3300 (manufactured by Covestro)

[0075] Example 1 40 parts by mass of the polyester resin (A-1) obtained in the above Synthesis Example was dissolved in 30 parts by mass of methyl ethyl ketone and 30 parts by mass of toluene to prepare a mixed resin varnish of methyl ethyl ketone and toluene with a solids concentration of 40% by mass. Epoxy resin (b1), epoxy resin (b2), and isocyanate compound (C) were blended into this varnish in amounts of 1.1 parts by mass, 0.4 parts by mass, and 1 part by mass, respectively, per 100 parts by mass of the polyester resin (A-1) in total to obtain adhesive composition (S1). The adhesive composition (S1) thus obtained was evaluated for appearance, peel strength, moist heat resistance, and storage stability. The results are shown in Table 2.

[0076] <Examples 2 to 4, Comparative Examples 1 to 5> Adhesive compositions (S2) to (S9) were prepared and evaluated in the same manner as in Example 1, except that the types and amounts of polyester resin, epoxy resin, and isocyanate compound were changed as shown in Table 2. The results are shown in Table 2.

[0077] <Evaluation of Adhesive Composition> (Creating a sample for performance evaluation) The adhesive composition was applied to a 100 μm thick polyimide film (HJA-A4, AS ONE) to a dry thickness of 30 μm, and then dried at 140°C for 3 minutes. The adhesive film (B-stage product) thus obtained was then laminated to a 0.2 mm thick aluminum alloy (A3003, Takeuchi Metal Foil & Powder Co., Ltd.). The lamination was performed using a roll laminator at a roll temperature of 190°C, a roll load of 3 kg / cm, and a pressing speed of 0.5 m / min. The film was then heat-treated at 150°C for 1 hour to cure, yielding a sample for initial performance evaluation.

[0078] (Appearance evaluation) Using the performance evaluation sample, the state of the adhesive layer was visually observed and evaluated. <Evaluation criteria> ◯: The adhesive layer did not flow out and no air bubbles were observed. △: The adhesive layer did not flow out, but fine bubbles were observed. ×: The adhesive layer flows out and air bubbles are observed.

[0079] (Peel strength (adhesion) evaluation) After leaving the performance evaluation sample at rest for 24 hours in a 25°C environment, the peel strength was measured under the conditions of film pulling, tensile speed 100mm / min, and 180° peeling in a 25°C environment. This test indicates the adhesive strength at room temperature. <Evaluation criteria> 〇:18N / cm or more △: 10N / cm or more, less than 18N / cm ×: Less than 10N / cm

[0080] (Heat and humidity resistance evaluation) The performance evaluation sample was subjected to an environmental load of 85°C, 85% RH for 1000 hours, and then left to stand in a 25°C environment for 24 hours. The peel strength measured after 1000 hours was recorded as the peel strength after 1000 hours. The peel strength was measured under conditions of a 25°C environment, film pulling, a tensile speed of 100 mm / min, and 180° peeling. The retention rate of the peel strength after 1000 hours relative to the peel strength before the environmental load was used to evaluate the resistance to moist heat. Retention rate (%) = (peel strength after 1000 hours) ÷ (peel strength before environmental loading) × 100 <Evaluation criteria> ◎: 80% or more ○: 60% or more, less than 80% △: 30% or more, less than 60% ×: Less than 30%

[0081] (Storage stability evaluation) The adhesive composition was applied to a 100 μm thick polyimide film (HJA-A4, AS ONE) to a dry thickness of 30 μm and dried at 140°C for 3 minutes. The adhesive film (B-stage product) obtained in this manner was placed in a 70°C oven for 24 hours and then laminated to a 0.2 mm thick aluminum alloy (A3003, Takeuchi Metal Foil Powder Co., Ltd.). Lamination was performed using a roll laminator at a roll temperature of 190°C, a roll load of 3 kg / cm, and a pressure-bonded material speed of 0.5 m / min. The sample obtained in this manner was left to stand for 24 hours at 25°C, after which the peel strength was measured under the conditions of film pulling, a tensile speed of 100 mm / min, and 180° peeling at 25°C. <Evaluation criteria> 〇:18N / cm or more △: 10N / cm or more, less than 18N / cm ×: Less than 10N / cm

[0082] [Table 2]

[0083] As is clear from Table 2, Examples 1 to 4 contained polyester resin (a1) having a glass transition temperature of 50°C or higher, epoxy resin (b1) having a nitrogen atom, epoxy resin (b2) not having a nitrogen atom, and isocyanate compound (C), and therefore were excellent in all of appearance, peel strength, moist heat resistance, and storage stability. On the other hand, the adhesive compositions of Comparative Examples 1 to 3 and 5 did not contain any of polyester resin (a1) having a glass transition temperature of 50°C or higher, epoxy resin (b1) having a nitrogen atom, epoxy resin (b2) not having a nitrogen atom, and isocyanate compound (C), and therefore were unable to simultaneously satisfy all of the properties of appearance, peel strength, moist heat resistance, and storage stability. Furthermore, Comparative Example 4 did not have satisfactory moist heat resistance due to the low content of polyester resin (a1) having a glass transition temperature of 50°C or higher. [Industrial Applicability]

[0084] The adhesive composition of the present invention has excellent adhesive properties, and furthermore, maintains excellent adhesive properties even after prolonged exposure to a high-temperature, high-humidity environment. Therefore, it is useful as an adhesive for bonding metals with excellent heat dissipation properties to resin substrates with excellent insulation properties, such as those used in the periphery of automobile batteries.

Claims

1. An adhesive composition comprising a polyester resin (A), an epoxy resin (B), and an isocyanate compound (C), and satisfying the following requirements (1) and (2): (1) The content of the polyester resin (a1) having a glass transition temperature of 50° C. or higher in the polyester resin (A) is 30% by mass or higher. (2) The epoxy resin (B) contains an epoxy resin (b1) having a nitrogen atom and an epoxy resin (b2) not having a nitrogen atom.

2. 2. The adhesive composition according to claim 1, wherein the polyester resin (A) has an acid value of 50 eq / t or more and 400 eq / t or less.

3. 2. The adhesive composition according to claim 1, wherein the content of the isocyanate compound (C) is 0.1 to 4 parts by mass per 100 parts by mass of the polyester resin (A).

4. 2. The adhesive composition according to claim 1, wherein the isocyanate compound (C) is an isocyanate compound having no aromatic ring.

5. 10. The adhesive composition of claim 1, further comprising at least one flame retardant.

6. An adhesive sheet comprising the adhesive composition according to any one of claims 1 to 5.

7. A laminate comprising the adhesive composition according to any one of claims 1 to 5.

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