WO2024090291A1

WO2024090291A1 - Adhesive composition, and adhesive sheet, layered body and printed circuit board containing same

Info

Publication number: WO2024090291A1
Application number: PCT/JP2023/037559
Authority: WO
Inventors: 晃一坂本; 哲生川楠
Original assignee: 東洋紡エムシー株式会社
Priority date: 2022-10-27
Filing date: 2023-10-17
Publication date: 2024-05-02

Abstract

Provided are an adhesive composition that has excellent adhesion and solder heat resistance, exerts excellent adhesion even after being exposed to high temperatures for a long period of time, and has good circuit embeddability while suppressing excessive resin flow, and an adhesive sheet, a layered body and a printed circuit board containing the adhesive composition.　The adhesive composition contains a polyester resin (A) and an epoxy resin (B); the epoxy resin (B) contains at least two types of epoxy resins (b) having nitrogen atoms; and one of the two types is the following epoxy resin (b1) and the other is the following epoxy resin (b2). (b1) A resin having a functionality of 3 or less. (b2) A resin having a functionality of 4 or more.

Description

Adhesive composition, and adhesive sheet, laminate, and printed wiring board containing the same

The present invention relates to an adhesive composition. More specifically, the present invention relates to an adhesive composition used for bonding a resin substrate to a resin substrate or a metal substrate. In particular, the present invention relates to an adhesive composition for flexible printed wiring boards (hereinafter abbreviated as FPC), as well as an adhesive sheet, a laminate, and a printed wiring board containing the same.

Flexible printed circuit boards (FPCs) are boards that have electrical circuits formed on a base material made by bonding a thin, soft insulating film, such as polyimide, to a conductive metal, such as copper foil, with an adhesive. Unlike rigid boards, they are extremely thin and flexible, making them suitable for use in small gaps and bending moving parts of electronic devices, and therefore are used in many of the electronic devices around us, such as personal computers and smartphones. Many FPCs are also installed in automobiles, and the adhesives used there often require high long-term heat resistance.

In recent years, the use of power semiconductors that generate high heat has increased along with the spread of electric vehicles, and the printed wiring board materials used to mount these semiconductors are required to have even higher standards of long-term heat resistance than before (for example, Non-Patent Document 1).

　Polyester resins are generally composed of polycarboxylic acids and polyhydric alcohols. They are widely used in a variety of applications, including coatings and adhesives, because of their flexibility and the ability to freely control the molecular weight and the selection and combination of polycarboxylic acids and polyhydric alcohols.

Polyester resins have excellent adhesion to metals, including copper, and have been used as adhesives for FPCs when mixed with a hardener (see, for example, Patent Document 1).

Japanese Patent Publication No. 6-104813

However, the adhesive using the polyester resin described in Patent Document 1 has poor solder heat resistance and does not have the high standard of long-term heat resistance required for modern automotive applications.

Furthermore, FPC adhesives are required to have circuit embedding properties that allow them to conform to the circuit pattern and ensure insulation between wiring. For this reason, when a substrate on which a circuit has been formed and a substrate having an adhesive layer are thermocompression bonded and laminated, a certain degree of flow of the adhesive components in a planar direction (hereafter referred to as resin flow) is necessary. On the other hand, excessive resin flow must be suppressed, as the adhesive components may flow out from between the wiring and cover areas outside the application range, causing problems such as poor conductivity. Improving circuit embedding properties and suppressing resin flow are mutually contradictory requirements, and the problem is that they are difficult to meet simultaneously.

The present invention has been made against the background of such problems in the conventional technology. In other words, the object of the present invention is to provide an adhesive composition that has excellent adhesion and solder heat resistance, and further exhibits excellent adhesion even after being exposed to a high-temperature environment for a long period of time, and that is capable of suppressing excessive resin flow while having good circuit embedding properties, as well as an adhesive sheet, laminate, and printed wiring board that contain the same.

As a result of extensive investigations, the present inventors have found that the above problems can be solved by the means described below, and have arrived at the present invention.
That is, the present invention comprises the following:
(1) An adhesive composition comprising a polyester resin (A) and an epoxy resin (B), the epoxy resin (B) comprising at least two types of epoxy resins (b) having a nitrogen atom, one of which is the following epoxy resin (b1) and the other is the following epoxy resin (b2).
(b1) a resin having three or less functionalities; (b2) a resin having four or more functionalities; (2) an adhesive composition containing a polyester resin (A) and an epoxy resin (B), the epoxy resin (B) containing at least two kinds of epoxy resins (b) having a nitrogen atom, one of the two kinds being the following epoxy resin (b3) and the other being the following epoxy resin (b4).
(b3) A resin having a nitrogen atom that is not contained in an aromatic ring and is not adjacent to an aromatic ring. (b4) A resin having a nitrogen atom excluding (b3). (3) The adhesive composition according to (1) or (2), wherein the epoxy resin having a nitrogen atom (b) contains a glycidyl amine type epoxy resin.
(4) The adhesive composition according to any one of (1) to (3), wherein the content of the epoxy resin (B) is 0.1 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the polyester resin (A).
(5) The adhesive composition according to any one of (1) to (4), further comprising an organic phosphinic acid metal salt (C).
(6) An adhesive sheet having an adhesive layer made of the adhesive composition according to any one of (1) to (5).
(7) A laminate having the adhesive sheet according to (6).
(8) A printed wiring board comprising the laminate according to (7) as a component.

The adhesive composition of the present invention has excellent adhesion, solder heat resistance, and long-term heat resistance, and also satisfies the requirements for circuit embedding and resin flow suppression. For this reason, it is suitable for FPC adhesives, adhesive sheets, laminates, and printed wiring boards for automotive applications.

Below, one embodiment of the present invention is described in detail. However, the present invention is not limited to this.

<Polyester resin (A)>
From the viewpoint of satisfying long-term heat resistance, the present invention uses a polyester resin (A) as the base resin.

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 each of the polycarboxylic acid component and the polyhydric alcohol component is composed of one or more selected components. The polycarboxylic acid component constituting the polyester resin (A) is not particularly limited, but the following polycarboxylic acids or their esters, and polycarboxylic acid anhydrides can be used. Specifically, examples of the polycarboxylic acid include aliphatic polycarboxylic acids, alicyclic polycarboxylic acids, and aromatic polycarboxylic acids. Examples of the aliphatic polycarboxylic acids include adipic acid, sebacic acid, dimer acid, 1,2,3,4-butanetetracarboxylic acid, fumaric acid, maleic acid, and succinic acid. Examples of the alicyclic polycarboxylic acids include 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, tetrahydrophthalic acid, hexahydrophthalic acid, and methyltetrahydrophthalic acid. Examples of the aromatic polycarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, 2,5-furandicarboxylic acid, 5-sodium sulfodimethylisophthalic acid, trimellitic acid, pyromellitic acid, and benzophenonetetracarboxylic acid, as well as esters and acid anhydrides thereof (pyromellitic anhydride (PMDA), etc.). In particular, the polyester resin (A) preferably contains a monomer unit derived from an aromatic polycarboxylic acid, and among these, the aromatic polycarboxylic acid preferably contains naphthalenedicarboxylic acid, terephthalic acid, or isophthalic acid. In 100 mol% of the polycarboxylic acid components constituting the polyester resin (A), the monomer unit derived from the aromatic polycarboxylic acid is preferably 60 mol% or more, more preferably 85 mol% or more, and even more preferably 96 mol% or more, and is preferably 100 mol% or less, and may be 98 mol% or less. The use of an aromatic polycarboxylic acid can improve the solder heat resistance of the adhesive composition.

The polyhydric alcohol constituting the polyester resin (A) is not particularly limited, but examples thereof include aliphatic polyhydric alcohols, alicyclic polyhydric alcohols, aromatic polyhydric alcohols, etc. Examples of 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, 2-ethyl-2-n-propyl-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, polytetramethylene glycol, polypropylene glycol, pentaerythritol, etc.; alicyclic polyhydric alcohols such as 1,4-cyclohexanedimethanol, tricyclodecane dimethanol, α-methylglucose, etc.; and aromatic polyhydric alcohols such as diphenolic acid can be used. In particular, the polyester resin (A) preferably contains a monomer unit derived from a polyhydric alcohol having an alkylene group having 4 or more carbon atoms. Examples of polyhydric alcohols having an alkylene group having 4 or more carbon atoms include 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol, 2-methyl-1,3-hexanediol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, dimer diol, polytetramethylene glycol, and the like. Among these, 1,4-butanediol and dimer diol are more preferable. In 100 mol% of the polyhydric alcohol component constituting the polyester resin (A), the monomer unit derived from a polyhydric alcohol having an alkylene group having 4 or more carbon atoms is preferably 20 to 80 mol%, more preferably 30 to 65 mol%, and even more preferably 40 to 60 mol%. By using a polyhydric alcohol having 4 or more carbon atoms, the adhesive strength of the adhesive composition can be improved.

The polyester resin (A) used in the present invention can also be copolymerized with lactones or lactams. For example, ε-caprolactone or ε-caprolactam can be used.

　The polymerization condensation reaction method for producing the polyester resin (A) used in the present invention includes, for example, 1) a method in which a polycarboxylic acid and a polyhydric alcohol are heated in the presence of a known catalyst, and a dehydration esterification process is performed, followed by 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, and a transesterification reaction is performed, followed by a polyhydric alcohol removal/polycondensation reaction; and 3) a method in which depolymerization is performed. In the above methods 1) and 2), a part or all of the acid component may be replaced with an acid anhydride.

When producing the polyester resin (A) used in the present invention, conventionally known polymerization catalysts such as titanium compounds, antimony compounds, germanium compounds, and metal acetates can be used. For example, titanium compounds such as tetra-n-butyl titanate, tetraisopropyl titanate, and titanium oxyacetylcetonate can be used; antimony compounds such as antimony trioxide and tributoxyantimony can be used; germanium compounds such as germanium oxide and tetra-n-butoxygermanium can be used; and metal acetates such as magnesium, iron, zinc, manganese, cobalt, and aluminum can be used. These catalysts can be used alone or in combination of two or more.

The number average molecular weight of the polyester resin (A) used in the present invention is preferably less than 100,000, more preferably 50,000 or less, and even more preferably 25,000 or less. It is also preferably 3,000 or more, more preferably 5,000 or more, and even more preferably 9,000 or more. If it is within the above range, it is easy to handle when dissolved in a solvent, and an adhesive composition with excellent adhesion can be obtained.

The glass transition temperature of the polyester resin (A) used in the present invention is preferably 0°C or higher, more preferably 10°C or higher, and even more preferably 20°C or higher. It is also preferably 200°C or lower, more preferably 100°C or lower, and even more preferably 50°C or lower. If it is within the above range, an adhesive composition with excellent adhesion can be obtained.

The acid value of the polyester resin (A) used in the present invention is preferably 50 eq/10 ⁶ g or more, more preferably 80 eq/10 ⁶ g or more. By making the acid value 50 eq/10 ⁶ g or more, the number of reaction points with the epoxy resin (B) increases, and a tough adhesive layer with high crosslink density can be formed after curing, resulting in excellent solder heat resistance. The upper limit of the acid value is not particularly limited, but is usually 1000 eq/10 ⁶ g or less, more preferably 500 eq/10 ⁶ g or less, and even more preferably 400 eq/10 ⁶ g or less.

The acid value of the polyester resin (A) can be increased by any of the following methods: (1) adding a polyvalent carboxylic acid having a valence of three or more and/or an anhydride polyvalent carboxylic acid having a valence of three or more after the polycondensation reaction is completed and reacting (acid addition); or (2) intentionally modifying the resin by applying heat, oxygen, water, or the like during the polycondensation reaction. The polyvalent carboxylic acid anhydride used in the acid addition method is not particularly limited, but examples include trimellitic anhydride, pyromellitic anhydride, hexahydrophthalic anhydride, 3,3,4,4-benzophenonetetracarboxylic dianhydride, 3,3,4,4-biphenyltetracarboxylic dianhydride, and ethylene glycol bistrimellitic anhydride. One or more of these can be used. Trimellitic anhydride is preferred.

<Epoxy resin (B)>
The epoxy resin (B) used in the present invention contains an epoxy resin (b) having a nitrogen atom. The term "epoxy resin" is not particularly limited as long as it has one or more epoxy groups in the molecule. By using an epoxy resin having a nitrogen atom, the long-term heat resistance is improved.

The nitrogen atoms in the skeleton of the epoxy resin (b) that contains nitrogen atoms have a catalytic effect, and as a result, it has a higher reactivity with polyester resins than other epoxy resins. Due to this high reactivity, when the adhesive composition is applied to a substrate and dried, curing progresses to a certain extent, and excessive resin flow can be suppressed when the resin is attached to a substrate on which a circuit has been formed.

Specific examples of the epoxy resin (b) having a nitrogen atom include glycidylamine type epoxy resins, triazine derivative epoxy resins, etc., and glycidylamine type epoxy resins are preferred in order to obtain the effects of the present invention more significantly. Specific examples of glycidylamine type epoxy resins include aliphatic glycidylamine type epoxy resins, alicyclic glycidylamine type epoxy resins, and aromatic glycidylamine type epoxy resins. Examples of alicyclic glycidylamine type epoxy resins include 1,3-bis(diglycidylaminomethyl)cyclohexane, and examples of aromatic glycidylamine type epoxy resins 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.

Specific examples of triazine derivative epoxy resins include 1,3,5-triglycidyl isocyanurate.

The adhesive composition of the present invention is characterized by containing at least two types of epoxy resins (b) having nitrogen atoms. By using at least two types of epoxy resins having nitrogen atoms in combination, it is possible to satisfy the requirements for circuit embedding and resin flow suppression without impairing long-term heat resistance.

From the viewpoints of circuit embeddability, resin flow suppression, and long-term heat resistance, it is particularly preferable that one of the two types of nitrogen-atom-containing epoxy resins (b) be a resin with three or fewer functionalities (hereinafter referred to as b1) and the other be a resin with four or more functionalities (hereinafter referred to as b2). Here, the number of functionalities refers to the number of epoxy groups in one molecule. There is a trade-off between circuit embeddability and excessive resin flow suppression, with (b1) alone resulting in poor circuit embeddability and (b2) alone not providing sufficient resin flow suppression. From the viewpoints of circuit embeddability and excessive resin flow suppression, both (b1) and (b2) are blended.

Specific examples of (b1) include N,N-diglycidylaniline, N,N-diglycidyl-o-toluidine, N,N,O-triglycidyl-p-aminophenol, N,N,O-triglycidyl-4-amino-3-methylphenol, and 1,3,5-triglycidyl isocyanurate, while specific examples of (b2) include 1,3-bis(diglycidylaminomethyl)cyclohexane, 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.

When (b1) is used as the epoxy resin (b) having nitrogen atoms, the content of (b1) per 100 parts by mass of the epoxy resin (b) having nitrogen atoms is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 50 parts by mass or more. Also, it is preferably 80 parts by mass or less, more preferably 75 parts by mass or less, and even more preferably 70 parts by mass or less. By keeping it within the above range, a particularly good balance between circuit embedding properties and resin flow suppression is achieved.

When (b2) is used as the epoxy resin (b) having a nitrogen atom, the content of (b2) per 100 parts by mass of the epoxy resin (b) having a nitrogen atom is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 30 parts by mass or more. Also, it is preferably 80 parts by mass or less, more preferably 70 parts by mass or less, and even more preferably 50 parts by mass or less. By keeping it within the above range, a particularly good balance between circuit embedding properties and resin flow suppression is achieved.

The content of (b1) is preferably 20 parts by mass or more and 300 parts by mass or less, more preferably 60 parts by mass or more and 250 parts by mass or less, and even more preferably 120 parts by mass or more and 240 parts by mass or less, per 100 parts by mass of (b2). By keeping it within the above range, a particularly good balance between circuit embedding properties and resin flow suppression is achieved.

The two types of epoxy resins (b) having nitrogen atoms are particularly preferably such that one is a resin having nitrogen atoms that are not contained in an aromatic ring and are not adjacent to an aromatic ring (hereinafter referred to as b3), and the other is a resin having nitrogen atoms other than (b3) (hereinafter referred to as b4), i.e., a resin having nitrogen atoms contained in an aromatic ring or adjacent to an aromatic ring and excluding (b3). The reason for this is unclear, but it is thought that this is due to the fact that the nitrogen atoms in the skeleton of (b3) have a greater catalytic effect than those of (b4), and it is presumed that blending both (b3) and (b4) makes it easier to balance the ability to embed circuits and the suppression of excessive resin flow.

Specific examples of (b3) include 1,3-bis(diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylylenediamine, etc. Specific examples of (b4) 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, 1,3,5-triglycidyl isocyanurate, etc.

When (b3) is used as the epoxy resin (b) having a nitrogen atom, the content of (b3) per 100 parts by mass of the epoxy resin (b) having a nitrogen atom is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 30 parts by mass or more. Also, it is preferably 80 parts by mass or less, more preferably 70 parts by mass or less, and even more preferably 50 parts by mass or less. By keeping it within the above range, a particularly good balance between circuit embedding properties and resin flow suppression is achieved.

When (b4) is used as the epoxy resin (b) having a nitrogen atom, the content of (b4) per 100 parts by mass of the epoxy resin (b) having a nitrogen atom is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 50 parts by mass or more. Also, it is preferably 80 parts by mass or less, more preferably 75 parts by mass or less, and even more preferably 70 parts by mass or less. By keeping it within the above range, a particularly good balance between circuit embedding properties and resin flow suppression is achieved.

The content of (b3) is preferably 20 parts by mass or more and 300 parts by mass or less, more preferably 30 parts by mass or more and 200 parts by mass or less, and even more preferably 40 parts by mass or more and 90 parts by mass or less, per 100 parts by mass of (b4). By keeping it within the above range, a particularly good balance between circuit embedding properties and resin flow suppression is achieved.

Regarding the nitrogen-containing epoxy resin (b), it is particularly preferable from the viewpoint of circuit embedding properties and suppression of resin flow that one of the two types is a resin having two or more nitrogen atoms and the other is a resin having one nitrogen atom. Specific examples of the resin having two or more nitrogen atoms include glycidylamine-type epoxy resins such as 1,3-bis(diglycidylaminomethyl)cyclohexane, 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, and examples of triazine derivative epoxy resins include 1,3,5-triglycidyl isocyanurate. Specific examples of resins having one nitrogen atom include N,N-diglycidylaniline, N,N-diglycidyl-o-toluidine, N,N,O-triglycidyl-p-aminophenol, and N,N,O-triglycidyl-4-amino-3-methylphenol.

When a resin having one nitrogen atom is used as the nitrogen-containing epoxy resin (b), the content of the resin having one nitrogen atom per 100 parts by mass of the nitrogen-containing epoxy resin (b) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 50 parts by mass or more. Also, it is preferably 80 parts by mass or less, more preferably 75 parts by mass or less, and even more preferably 70 parts by mass or less. By keeping it within the above range, a particularly good balance between circuit embedding properties and resin flow suppression is achieved.

When a resin having two or more nitrogen atoms is used as the nitrogen-containing epoxy resin (b), the content of the resin having two or more nitrogen atoms per 100 parts by mass of the nitrogen-containing epoxy resin (b) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 30 parts by mass or more. Also, it is preferably 80 parts by mass or less, more preferably 70 parts by mass or less, and even more preferably 50 parts by mass or less. By keeping it within the above range, a particularly good balance between circuit embedding properties and resin flow suppression is achieved.

The content of the resin having one nitrogen atom is preferably 20 parts by mass or more and 300 parts by mass or less, more preferably 60 parts by mass or more and 250 parts by mass or less, and even more preferably 120 parts by mass or more and 240 parts by mass or less, per 100 parts by mass of the resin having two or more nitrogen atoms. By keeping it within the above range, a particularly good balance between circuit embedding properties and resin flow suppression is achieved.

In the adhesive composition of the present invention, the content of the resin (b) having a nitrogen atom is preferably 40 parts by mass or more per 100 parts by mass of the epoxy resin (B), more preferably 60 parts by mass or more, and even more preferably 70 parts by mass or more, and may be 100 parts by mass. When the content is equal to or more than the lower limit, the long-term heat resistance is particularly good.

The adhesive composition of the present invention may contain an epoxy resin other than the nitrogen-atom-containing epoxy resin (b). The epoxy resin other than the nitrogen-atom-containing epoxy resin (b) is not particularly limited as long as it has an epoxy group in the molecule, but is preferably one having 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 resin, naphthalene-type epoxy resin, bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, novolac-type epoxy resin, alicyclic epoxy resin, dicyclopentadiene-type epoxy resin, dimer acid-modified epoxy resin, and epoxy-modified polybutadiene can be used.

In the adhesive composition of the present invention, the content of epoxy resin (B) is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, per 100 parts by mass of polyester resin (A) in total. If it is equal to or more than the lower limit, a sufficient curing effect can be obtained, and excellent adhesion and solder heat resistance can be exhibited. Also, it is preferably 20 parts by mass or less, more preferably 10 parts by mass or less. If it is equal to or less than the upper limit, long-term heat resistance becomes good. In other words, by keeping it within the above range, an adhesive composition having better adhesion, solder heat resistance, and long-term heat resistance can be obtained.

<Flame retardants>
The adhesive composition of the present invention may contain a flame retardant. The flame retardant is not particularly limited, but may be an organic phosphorus compound or an organic metal phosphinate (C). Since the organic metal phosphinate (C) is particularly effective in achieving both flame retardancy and long-term heat resistance, the organic metal phosphinate (C) is preferred.

Specific examples of organic phosphorus compounds include 9,10-dihydro-10-benzyl-9-oxa-10-phosphaphenanthrene-10-oxide, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, etc.

Specific examples of the organic metal phosphinate include dimethylphosphinate, ethylmethylphosphinate, diethylphosphinate, methyl-n-propylphosphinate, methylphenylphosphinate, diphenylphosphinate, methane di(methylphosphinic acid) salt, and benzene-1,4-di(methylphosphinic acid) salt.
Examples of dimethylphosphinates include magnesium dimethylphosphinate, calcium dimethylphosphinate, zinc dimethylphosphinate, and aluminum dimethylphosphinate. Examples of ethylmethylphosphinates include magnesium ethylmethylphosphinate, calcium ethylmethylphosphinate, zinc ethylmethylphosphinate, and aluminum ethylmethylphosphinate. Examples of diethylphosphinates include magnesium diethylphosphinate, calcium diethylphosphinate, zinc diethylphosphinate, and aluminum diethylphosphinate. Examples of methyl-n-propylphosphinates include magnesium methyl-n-propylphosphinate, calcium methyl-n-propylphosphinate, zinc methyl-n-propylphosphinate, and aluminum methyl-n-propylphosphinate. Examples of methylphenylphosphinates include magnesium methylphenylphosphinate. Examples of diphenylphosphinates that can be used include magnesium diphenylphosphinate, calcium diphenylphosphinate, zinc diphenylphosphinate, and aluminum diphenylphosphinate; examples of methane di(methylphosphinic acid) salts include magnesium methane di(methylphosphinic acid), calcium methane di(methylphosphinic acid), zinc methane di(methylphosphinic acid), and aluminum methane di(methylphosphinic acid); and examples of benzene-1,4-di(methylphosphinic acid) salts include magnesium benzene-1,4-di(methylphosphinic acid), calcium benzene-1,4-di(methylphosphinic acid), zinc benzene-1,4-di(methylphosphinic acid), and aluminum benzene-1,4-di(methylphosphinic acid).

When the adhesive composition of the present invention contains a flame retardant, the content of the flame retardant is preferably 1 to 40 parts by mass, and more preferably 5 to 20 parts by mass, per 100 parts by mass of polyester resin (A) in total. By making the content equal to or greater than the lower limit, an adhesive composition with excellent flame retardancy can be produced, and by making the content equal to or less than the upper limit, it is advantageous in terms of production costs.

<Organic Solvent>
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 (A) and the epoxy resin (B). Specific examples of the organic solvent include aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, halogenated hydrocarbons, alcohol solvents, ketone solvents, ester solvents, and glycol ether solvents. Examples of aromatic hydrocarbons include benzene, toluene, and xylene. Examples of aliphatic hydrocarbons include hexane, heptane, octane, and decane. Examples of alicyclic hydrocarbons include cyclohexane, cyclohexene, methylcyclohexane, and ethylcyclohexane. Examples of halogenated hydrocarbons include trichloroethylene, dichloroethylene, chlorobenzene, and chloroform. Examples of alcohol solvents include methanol, ethanol, isopropyl alcohol, butanol, pentanol, hexanol, propanediol, and phenol. Examples of ketone solvents include acetone and methyl isopropyl alcohol. Examples of the solvents that can be used include isobutyl ketone, methyl ethyl ketone, pentanone, hexanone, cyclohexanone, isophorone, acetophenone, etc., ester solvents include methyl acetate, ethyl acetate, butyl acetate, methyl propionate, butyl formate, etc., and glycol ether solvents include ethylene glycol monomethyl ether, 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, tetraethylene glycol mono n-butyl ether, etc., and these can be used alone or in combination of two or more. In particular, aromatic hydrocarbons or ketone solvents are preferred from the viewpoints of working environment and drying property, and toluene and methyl ethyl ketone are more preferred.

When the adhesive composition of the present invention contains an organic solvent, the content of the organic solvent is preferably in the range of 100 to 1000 parts by mass per 100 parts by mass of polyester resin (A) in total. By making the content equal to or greater than the lower limit, the liquid state and pot life are improved. Furthermore, by making the content equal to or less than the upper limit, it is advantageous in terms of manufacturing costs and transportation costs.

The adhesive composition of the present invention may further contain other components as necessary. Specific examples of such components include a tackifier, a filler, and a silane coupling agent.

<Tackifier>
The adhesive composition of the present invention may contain a tackifier as necessary. Examples of tackifiers include polyterpene resins, rosin resins, aliphatic petroleum resins, alicyclic petroleum resins, copolymerized petroleum resins, styrene resins, and hydrogenated petroleum resins, and are used for the purpose of improving adhesive strength. These may be used alone or in any combination of two or more. When a tackifier is contained, it is preferably contained in a range of 1 to 200 parts by mass, more preferably in a range of 5 to 150 parts by mass, and most preferably in a range of 10 to 100 parts by mass, relative to a total of 100 parts by mass of the polyester resin (A) and the epoxy resin (B). By keeping it within the above range, the effect of the tackifier can be expressed while maintaining adhesion and solder heat resistance.

<Filler>
The adhesive composition of the present invention may contain a filler as necessary. Examples of the filler include organic fillers and inorganic fillers. Examples of the organic fillers include heat-resistant resins such as polyimide, polyamideimide, fluororesin, and liquid crystal polyester powders, and examples of the inorganic fillers include silica (SiO ₂ ), alumina (Al ₂ O ₃ ), titania (TiO ₂ ), tantalum oxide (Ta ₂ O ₅ ), zirconia (ZrO ₂ ), silicon nitride (Si ₃ N ₄ ), boron nitride (BN), calcium carbonate (CaCO ₃ ), calcium sulfate (CaSO ₄ ), zinc oxide (ZnO), magnesium titanate (MgO.TiO ₂ ), barium sulfate (BaSO ₄ ), organic bentonite, clay, mica, aluminum hydroxide, and magnesium hydroxide. Among these, silica is preferred because of its ease of dispersion and its effect of improving solder heat resistance. Generally, hydrophobic silica and hydrophilic silica are known as silica, but in this case, hydrophobic silica treated with dimethyldichlorosilane, hexamethyldisilazane, octylsilane, etc. is better in order to impart moisture absorption resistance. When a filler is blended, the blending amount is preferably 0.05 to 50 parts by mass per 100 parts by mass of the polyester resin (A) and the epoxy resin (B) combined. By making the amount equal to or greater than the lower limit, further solder heat resistance can be achieved. Also, by making the amount equal to or less than the upper limit, poor dispersion of the filler and excessively high solution viscosity can be suppressed, and workability can be improved.

<Silane coupling agent>
The adhesive composition of the present invention may contain a silane coupling agent as necessary. The incorporation of a silane coupling agent is highly preferred because it improves the adhesiveness to metals and solder heat resistance. The silane coupling agent is not particularly limited, but examples include those having an unsaturated group, those having an epoxy group, and those having an amino group. Among these, those having an epoxy group are more preferred from the viewpoint of solder heat resistance, and examples of usable silane coupling agents include γ-glycidoxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltriethoxysilane. When a silane coupling agent is incorporated, the amount of the silane coupling agent is preferably 0.5 to 20 parts by mass per 100 parts by mass of the total of the polyester resin (A) and the epoxy resin (B). By keeping the amount within the above range, the solder heat resistance and adhesiveness can be improved.

<Laminate>
The laminate of the present invention is a laminate of the adhesive composition on a substrate (a two-layer laminate of substrate/adhesive layer), or a three-layer laminate of substrate/adhesive layer/substrate. Here, the adhesive layer refers to a layer of the adhesive composition after the adhesive composition of the present invention is applied to a substrate and dried. The adhesive composition of the present invention can be applied to various substrates according to a conventional method, dried, and then laminated with another substrate to obtain the laminate of the present invention.

<Substrate>
In the present invention, the substrate is not particularly limited as long as it is capable of forming an adhesive layer by applying and drying the adhesive composition of the present invention, and examples of the substrate include resin substrates such as film-like resins, metal substrates such as metal plates and metal foils, papers, etc. In addition, the substrate in the present invention may be made of a composite material.

Examples of resin substrates include polyester resins, polyamide resins, polyimide resins, polyamideimide resins, liquid crystal polymers, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resins, and fluorine resins. A film-like resin (hereinafter also referred to as a substrate film layer) is preferred.

Any conventionally known conductive material that can be used for a circuit board can be used as the metal substrate. Examples of materials 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 and chromium compounds. Metal foil is preferred, and copper foil is more preferred. There is no particular limitation on the thickness of the metal foil, but it is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 10 μm or more. It is also preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less. If the thickness is too thin, it may be difficult to obtain sufficient electrical performance of the circuit, while if the thickness is too thick, the processing efficiency during circuit fabrication may decrease. Metal foil is usually provided in a rolled form. There is no particular limitation on the form of the metal foil used in manufacturing the printed wiring board of the present invention. When a ribbon-shaped metal foil is used, there is no particular limitation on its length. There is also no particular limitation on its width, but it is preferably about 250 to 500 cm. There are no particular limitations on the surface roughness of the substrate, but it is preferably 3 μm or less, more preferably 2 μm or less, and even more preferably 1.5 μm or less. In practical terms, it is preferably 0.3 μm or more, more preferably 0.5 μm or more, and even more preferably 0.7 μm or more.

Examples of paper include fine paper, craft paper, roll paper, glassine paper, etc. Examples of composite materials include glass epoxy, etc.

In terms of adhesion to the adhesive composition and durability, the substrate is preferably polyester resin, polyamide resin, polyimide resin, polyamideimide resin, liquid crystal polymer, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resin, fluorine resin, SUS steel plate, copper foil, aluminum foil, or glass epoxy.

<Adhesive sheet>
In the present invention, the adhesive sheet is a laminate of the substrate and the release substrate via an adhesive composition. Specific configurations include substrate/adhesive layer/release substrate, or release substrate/adhesive layer/substrate/adhesive layer/release substrate. The release substrate functions as a protective layer for the adhesive layer by laminating it. In addition, 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.

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 in the usual manner. Furthermore, by attaching a release substrate to the adhesive layer after drying, it is possible to wind it up without causing offset onto the substrate, which is excellent in operability, and since the adhesive layer is protected, it is excellent in storage stability and easy to use. Furthermore, if a release substrate is attached after application and drying, it is also possible to transfer the adhesive layer itself to another substrate if another release substrate is attached as necessary.

<Release substrate>
The release substrate is not particularly limited, but examples thereof include those in which a coating layer of a filler such as clay, polyethylene, or polypropylene is provided on both sides of paper such as fine paper, craft paper, roll paper, or glassine paper, and a silicone-based, fluorine-based, or alkyd-based release agent is further applied on each coating layer. 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 on which the release agent is applied. Due to 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-filled coating on both sides of fine paper and an alkyd-based release agent thereon, or an alkyd-based release agent on polyethylene terephthalate.

In the present invention, the method of coating the adhesive composition on the substrate is not particularly limited, but examples thereof include a comma coater and a reverse roll coater. Alternatively, if necessary, an adhesive layer can be provided directly or by a transfer method on the rolled copper foil or polyimide film that is the printed wiring board constituent material. The thickness of the adhesive layer after drying can be appropriately changed as necessary, 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. In addition, by making it 200 μm or less, it becomes easier to control the amount of residual solvent in the drying process, and swelling is less likely to occur during pressing in the production of printed wiring boards. The drying conditions are not particularly limited, but the residual solvent rate after drying is preferably 1 mass % or less. By making it 1 mass % or less, foaming of the residual solvent is suppressed during pressing of the printed wiring board, and swelling is less likely to occur.

<Printed Wiring Board>
The printed wiring board in the present invention includes, as a component, a laminate formed from a metal foil forming a conductor circuit and a resin substrate. The printed wiring board is manufactured by a conventionally known method such as a subtractive method using a metal-clad laminate. If necessary, the printed wiring board is a general term for so-called flexible circuit boards (FPC), flat cables, circuit boards for tape automated bonding (TAB), etc., in which a conductor circuit formed by a metal foil is partially or entirely covered with a cover film, screen printing ink, etc.

The printed wiring board of the present invention can have any laminated structure that can be used as a printed wiring board. For example, it can be a printed wiring board consisting of four layers: a base film layer, a metal foil layer, an adhesive layer, and a cover film layer. It can also be a printed wiring board consisting of five layers: a base film layer, an adhesive layer, a metal foil layer, an adhesive layer, and a cover film layer.

Furthermore, if necessary, two or more of the above printed wiring boards can be stacked together.

The adhesive composition of the present invention can be suitably used for each adhesive layer of a printed wiring board. In particular, when the adhesive composition of the present invention is used as an adhesive, it has high adhesion to conventional resin substrates such as polyimide, polyester film, copper foil, and aluminum foil that constitute printed wiring boards, and can provide solder reflow resistance. Therefore, it is suitable as an adhesive composition for use in coverlay films, laminates, resin-coated copper foil, bonding sheets, and reinforcing materials.

In the printed wiring board of the present invention, any resin film that has been conventionally used as a substrate for printed wiring boards can be used as the substrate film. Examples of resins for the substrate film include polyester resins, polyamide resins, polyimide resins, polyamideimide resins, liquid crystal polymers, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resins, and fluorine-based resins.

<Cover film>
As the cover film, any insulating film conventionally known as an insulating film for printed wiring boards can be used. For example, films made of various polymers such as polyimide, polyester, polyphenylene sulfide, polyethersulfone, polyetheretherketone, aramid, polycarbonate, polyarylate, polyamideimide, liquid crystal polymer, syndiotactic polystyrene, and polyolefin resin can be used. More preferably, it is a polyimide film.

The printed wiring board of the present invention can be manufactured using any conventionally known process, except for using the materials for each layer described above.

In a preferred embodiment, a semi-finished product is manufactured in which an adhesive layer is laminated on a cover film layer (hereinafter referred to as a "cover film side semi-finished product"). On the other hand, a semi-finished product is manufactured in which a metal foil layer is laminated on a base film layer to form a desired circuit pattern (hereinafter referred to as a "base film side two-layer semi-finished product"), or a semi-finished product is manufactured in which an adhesive layer is laminated on a base film layer and a metal foil layer is laminated on top of it to form a desired circuit pattern (hereinafter referred to as a "base film side three-layer semi-finished product") (hereinafter, the base film side two-layer semi-finished product and the base film side three-layer semi-finished product are collectively referred to as the "base film side semi-finished product"). By bonding the cover film side semi-finished product thus obtained and the base film side semi-finished product together, a four-layer or five-layer printed wiring board can be obtained.

The semi-finished product on the base film side can be obtained, for example, by a manufacturing method including a process (A) of applying a solution of the resin that will become the base film to the metal foil and initially drying the coating, and a process (B) of heat-treating and drying the laminate of the metal foil and the initially dried coating obtained in (A) (hereinafter referred to as the "heat treatment/solvent removal process").

The formation of the circuit in the metal foil layer can be achieved by a conventional method. Either an additive method or a subtractive method can be used. A subtractive method is preferred.

The obtained semi-finished product on the base film side may be used as is for bonding to the semi-finished product on the cover film side, or it may be used for bonding to the semi-finished product on the cover film side after bonding a release film and storing it.

The cover film side semi-finished product is produced, for example, by applying an adhesive to the cover film. If necessary, a crosslinking reaction can be carried out in the applied adhesive. In a preferred embodiment, the adhesive layer is semi-cured.

The obtained semi-finished product on the cover film side may be used as is for bonding to the semi-finished product on the base film side, or it may be used for bonding to the semi-finished product on the base film side after bonding a release film and storing it.

The semi-finished product on the base film side and the semi-finished product on the cover film side are stored, for example, in the form of a roll, and then laminated together to produce a printed wiring board. Any method can be used for laminating them together, and for example, they can be laminated together using a press or roll. They can also be laminated together while heating them, for example, using a heated press or a heated roll device.

In the case of a reinforcing material that is soft and can be rolled up, such as a polyimide film, the semi-finished reinforcing material is preferably manufactured by applying an adhesive to the reinforcing material. In the case of a reinforcing plate that is hard and cannot be rolled up, such as a metal plate such as SUS or aluminum, or a plate made of glass fiber cured with epoxy resin, it is preferably manufactured by transfer-coating an adhesive that has been applied in advance to a release substrate. If necessary, a crosslinking reaction can be carried out in the applied adhesive. In a preferred embodiment, the adhesive layer is semi-cured.

The obtained semi-finished product on the reinforcing material side may be used as is for bonding to the back surface of a printed wiring board, or it may be used for bonding to the semi-finished product on the base film side after a release film has been applied and stored.

The base film semi-finished product, the cover film semi-finished product, and the reinforcing material semi-finished product are all laminates for printed wiring boards according to the present invention.

This application claims the benefit of priority based on Japanese Patent Application No. 2022-172590, filed on October 27, 2022. The entire contents of the specification of Japanese Patent Application No. 2022-172590, filed on October 27, 2022, are incorporated by reference into this application.

The present invention will be specifically explained below with reference to examples. Note that in these examples and comparative examples, parts simply indicate parts by mass.

(Physical property evaluation method)
(Measurement of composition of polyester resin (A))
A 400 MHz 1H-nuclear magnetic resonance spectrometer (hereinafter sometimes abbreviated as NMR) was used to quantitatively determine the molar ratios of the polyvalent carboxylic acid component and the polyhydric alcohol component constituting the polyester resin (A). Deuterated chloroform was used as the solvent. When the acid value of the polyester resin (A) was increased by post-acid addition, the molar ratios of each component were calculated by taking the total of the acid components other than the acid component used in the post-acid addition as 100 mol %.

(Measurement of Glass Transition Temperature)
Measurement was performed using a differential scanning calorimeter (DSC-200, SII). 5 mg of a sample (polyester resin (A)) was placed in an aluminum container with a lid and sealed, and cooled to -50°C using liquid nitrogen. The temperature was then increased to 150°C at a rate of 20°C/min, and the glass transition temperature (unit: °C) 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 between the rising part of the peak and the apex of the peak) in the endothermic curve obtained during the temperature increase process.

(Measurement of Number Average Molecular Weight)
A sample of polyester resin (A) was dissolved and/or diluted with tetrahydrofuran so that the resin concentration was about 0.5% by mass, and filtered through a polytetrafluoroethylene membrane filter with a pore size of 0.5 μm to prepare a measurement sample. The molecular weight was measured by gel permeation chromatography (GPC) using tetrahydrofuran as the mobile phase and a differential refractometer as the detector. The flow rate was 1 mL/min, and the column temperature was 30° C. The columns used were KF-802, 804L, and 806L manufactured by Showa Denko. Monodisperse polystyrene was used as the molecular weight standard.

The following is a synthesis example of the polyester resin (A) used in the present invention.

(Production Example of Polyester Resin (a1))
A reactor equipped with a stirrer, a condenser, and a thermometer was charged with 20.93 parts of terephthalic acid, 0.81 parts of trimellitic anhydride, 43.25 parts of isophthalic acid, 4.25 parts of sebacic acid, 2.41 parts of diphenolic acid, 24.51 parts of 2-methyl-1,3-propanediol, 13.78 parts of 1,4-cyclohexanedimethanol, 33.11 parts of 1,4-butanediol, and 0.03 mol% of tetrabutyl orthotitanate as a catalyst relative to the total polyvalent carboxylic acid component, and the temperature was raised from 160 ° C. to 220 ° C. over 4 hours, and an esterification reaction was carried out through a dehydration process. Next, in the polycondensation reaction process, the pressure in the system was reduced to 5 mmHg over 20 minutes, and the temperature was further raised to 250 ° C. Next, the pressure was reduced to 0.3 mmHg or less, and polycondensation reaction was carried out for 60 minutes, followed by cooling to 220 ° C., and 0.82 parts of trimellitic anhydride and 0.88 parts of ethylene glycol bistrimellitic anhydride were added, reacted for 30 minutes, and then taken out. As a result of composition analysis by NMR, the obtained polyester resin (a1) was a copolymer polyester having a molar ratio of terephthalic acid / isophthalic acid / sebacic acid / diphenolic acid / trimellitic anhydride / 2-methyl-1,3-propanediol / 1,4-butanediol / 1,4-cyclohexanedimethanol / trimellitic anhydride / ethylene glycol bistrimellitic anhydride = 30 / 62 / 5 / 2 / 1 / 28 / 55 / 17 / 1 / 0.5. In addition, the glass transition temperature was 35 ° C., the acid value was 150 eq / 10 ⁶ g, and the number average molecular weight was 14,200.

(Production Example of Polyester Resin (a2))
A reactor equipped with a stirrer, a condenser, and a thermometer was charged with 54.79 parts of terephthalic acid, 20.60 parts of isophthalic acid, 0.79 parts of trimellitic anhydride, 11.54 parts of ethylene glycol, 45.20 parts of neopentyl glycol, and 0.05 mol% of tetrabutyl orthotitanate as a catalyst relative to the total polyvalent carboxylic acid components, and the temperature was raised from 160°C to 220°C over 4 hours, and an esterification reaction was carried out through a dehydration process. Next, in the polycondensation reaction process, the pressure in the system was reduced to 5 mmHg over 20 minutes, and the temperature was further increased to 250°C. Next, the pressure was reduced to 0.3 mmHg or less, and a polycondensation reaction was carried out for 60 minutes, after which the system was cooled to 220°C, and 0.79 parts of trimellitic anhydride was added, reacted for 30 minutes, and then taken out. The composition of the obtained polyester resin (a2) was analyzed by NMR and found to be a copolymer polyester having a molar ratio of terephthalic acid/isophthalic acid/trimellitic anhydride/ethylene glycol/neopentyl glycol/trimellitic anhydride = 69/30/1/30/70/1, and had a glass transition temperature of 63°C, an acid value of 100 eq/10 ⁶ g, and a number average molecular weight of 10,000.

(Production Example of Polyamideimide (d1))
A four-necked separable flask equipped with a stirrer, a cooling tube, a nitrogen inlet tube and a thermometer was charged with 105.67 g of trimellitic anhydride, 80.09 g of sebacic acid, 175 g of acrylonitrile butadiene rubber (CTBN 1300 x 13, number average molecular weight 3500, proportion of acrylonitrile moiety 26 wt%) with both ends being carboxylic acid, 252.75 g of 4,4'-diphenylmethane diisocyanate, and 526 g of dimethylacetamide, and the mixture was heated to 100 ° C. under a nitrogen stream and reacted for 2 hours. Next, 117 g of dimethylacetamide was added, and the mixture was further reacted at 150 ° C. for 5 hours, after which 439 g of toluene and 146 g of dimethylacetamide were added to dilute the mixture, and the mixture was cooled to room temperature to obtain a brown but completely clear polyamideimide resin solution (d1). In addition, the glass transition temperature was 145 ° C., the acid value was 463 eq / 10 ⁶ g, and the number average molecular weight was 20,000.

(Production Example of Acid-Modified Polypropylene (e1))
In a 1L autoclave, 100 parts by mass of propylene-butene copolymer (Mitsui Chemicals "Tafmer (registered trademark) XM7080"), 150 parts by mass of toluene, 19 parts by mass of maleic anhydride, and 6 parts by mass of di-tert-butyl peroxide were added, and the temperature was raised to 140 ° C., and then the mixture was stirred for another 3 hours. Thereafter, the obtained reaction liquid was cooled and poured into a container containing a large amount of methyl ethyl ketone to precipitate a resin. Thereafter, the liquid containing the resin was centrifuged to separate and purify the acid-modified propylene-butene copolymer in which maleic anhydride was graft-polymerized, (poly)maleic anhydride, and low molecular weight substances. Thereafter, the mixture was dried under reduced pressure at 70 ° C. for 5 hours to obtain a maleic anhydride-modified propylene-butene copolymer (e1). In addition, the acid value was 338 eq / 10 ⁶ g, the number average molecular weight was 25,000, and the melting point was 80 ° C.

The following describes production examples of adhesive compositions according to the present invention and comparative adhesive compositions.
As the epoxy resin (B), the following was used.
EP-3950E: (N,N,O-triglycidyl-p-aminophenol, manufactured by ADEKA Corporation)

TETRAD X: (N,N,N',N'-tetraglycidyl-m-xylylenediamine, manufactured by Mitsubishi Gas Chemical Company, Inc.)

jER604: (N,N,N',N'-tetraglycidyl-(4,4'-methylenebisaniline), manufactured by Mitsubishi Chemical Corporation)

YDCN-700-10: (cresol novolac epoxy, manufactured by Nippon Steel Chemical & Material Co., Ltd.)
The following flame retardants were used:
Exolit (registered trademark) OP-930: (organophosphinic acid metal salt, Clariant) BCA: (organophosphorus compound, 9,10-dihydro-10-benzyl-9-oxa-10-phosphaphenanthrene-10-oxide, Sanko Co., Ltd.)

Example 1
40 parts by mass of the copolymerized polyester (a1) obtained in the above synthesis example was dissolved in toluene to prepare a toluene varnish having a solid content concentration of 40% by mass. EP-3950E and TETRAD X as curing agents and Exolit OP930 as an organic phosphinic acid metal salt were mixed into this varnish in amounts of 2 parts by mass, 1 part by mass, and 10 parts by mass, respectively, per 100 parts by mass of the polyester resin (a1), to obtain an adhesive composition (F1).
The adhesive composition (F1) thus obtained was evaluated for adhesion, solder heat resistance, resin flow, flame retardancy, and long-term heat resistance. The results are shown in Table 1.

(Examples 2 to 9, Comparative Examples 1 to 7)
Adhesive compositions (F2) to (F16) were prepared and evaluated in the same manner as in Example 1, except that the types and amounts of the polyester resin (A) and epoxy resin (B) were changed as shown in Table 1. The results are shown in Table 1.

(Evaluation of Adhesive Compositions)
(Adhesiveness (peel strength))
The adhesive composition was applied to one side of a 12.5 μm thick polyimide film (Apical (registered trademark) manufactured by Kaneka Corporation) so that the thickness after drying was 25 μm, and dried at 130 ° C for 3 minutes. The adhesive film (B stage product) obtained in this way was laminated with a rolled copper foil (ESPANEX series manufactured by Nippon Steel Chemical & Material Co., Ltd.) having a thickness of 18 μm. The laminate was pressed at 170 ° C under a pressure of 2 MPa for 280 seconds so that the glossy side of the rolled copper foil was in contact with the adhesive layer, and the adhesive was bonded. The laminate was then heat-treated at 170 ° C for 3 hours to harden the film, and a sample for peel strength evaluation was obtained. The peel strength was measured under the conditions of 25 ° C, film pulling, tensile speed 50 mm / min, and 90 ° peeling. This test shows the adhesive strength at room temperature.
<Evaluation criteria>
○: 1.0 N/mm or more △: 0.5 N/mm or more and less than 1.0 N/mm ×: Less than 0.5 N/mm

(solder heat resistance)
Samples were prepared in the same manner as above, and a 2.0 cm×2.0 cm sample piece was immersed in a bath of molten solder at 288° C., and the presence or absence of any change in appearance, such as blistering, was confirmed.
<Evaluation criteria>
◎: No swelling for 60 seconds or more ○: Swelling occurs for 30 seconds or more but less than 60 seconds ×: Swelling occurs for less than 30 seconds

(Resin Flow)
The adhesive composition was applied to one side of a 12.5 μm thick polyimide film (Apical (registered trademark), manufactured by Kaneka Corporation) so that the thickness after drying was 25 μm, and dried at 130 ° C for 3 minutes. The adhesive film (B stage product) obtained in this manner was laminated to a substrate in which a circuit was formed at a pitch of 100 μm on a rolled copper foil (ESPANEX series, manufactured by Nippon Steel Chemical & Material Co., Ltd.) having a thickness of 18 μm. The lamination was performed by pressing for 280 seconds at 170 ° C under a pressure of 2 MPa so that the circuit surface was in contact with the adhesive layer. The amount of adhesive flowing out from the lamination surface along the circuit was measured with a microscope. The circuit embedding property and resin flow suppression were evaluated by this test. If the measured value is less than 0.050 mm, the circuit embedding property is not satisfactory. Also, if the measured value is 1.00 mm or more, the resin flow is excessive.
<Evaluation criteria>
◎: 0.10 mm or more and less than 0.30 mm ○: 0.050 mm or more and less than 0.10 mm or 0.30 mm or more and less than 0.50 mm △: 0.50 mm or more and less than 1.00 mm ×: Less than 0.050 mm or 1.00 mm or more

(Flame retardance)
The adhesive composition was applied to both sides of a 12.5 μm thick polyimide film (Apical 12.5NPI, manufactured by Kaneka Corporation) so that the thickness after drying would be 16 μm, and the film was dried at 130° C. for 3 minutes in a fan oven, and then heated and cured at 170° C. for 3 hours to prepare a sample. Flame retardancy was evaluated in accordance with the UL-94 VTM flame retardancy standard.
<Evaluation criteria>
◯: Equivalent to UL94 VTM-0.
×: Does not satisfy UL94 VTM-0.

(Long-term heat resistance (peel strength))
The adhesive composition was applied to one side of a 12.5 μm thick polyimide film (Apical (registered trademark) manufactured by Kaneka Corporation) so that the thickness after drying was 25 μm, and dried at 130 ° C for 3 minutes. The adhesive film (B stage product) obtained in this manner was laminated with a rolled copper foil (ESPANEX series manufactured by Nippon Steel Chemical & Material Co., Ltd.) having a thickness of 18 μm. The laminate was pressed for 280 seconds at 170 ° C under a pressure of 2 MPa so that the glossy side of the rolled copper foil was in contact with the adhesive layer, and the adhesive was bonded. The laminate was then heat-treated at 170 ° C for 3 hours to harden the film, and a peel strength evaluation sample was obtained. The sample was left in an oven at 150 ° C in an air atmosphere for 1000 hours, and the peel strength after 1000 hours was measured. The peel strength was measured under the conditions of 25 ° C, film pulling, tensile speed 50 mm / min, and 90 ° peeling. This test shows the long-term reliability of the adhesive strength.
<Evaluation criteria>
◎: 0.5 N/mm or more ○: 0.2 N/mm or more, less than 0.5 N/mm ×: less than 0.2 N/mm

As is clear from Table 1, Examples 1 to 9 are adhesive compositions containing polyester resin (A) and at least two kinds of epoxy resin (b) having nitrogen atoms, one of the two kinds being (b1) and the other being (b2) or one being (b3) and the other being (b4), and all of them are excellent in adhesion, solder heat resistance, and long-term heat resistance, and also satisfy circuit embedding and resin flow suppression. On the other hand, the adhesive compositions of Comparative Examples 1 to 3 cannot satisfy circuit embedding and resin flow suppression because only one kind of epoxy resin (b) having nitrogen atoms is used, and Comparative Example 4 cannot satisfy long-term heat resistance because it uses cresol novolac type epoxy resin as epoxy resin (B) and does not use epoxy resin (b) having nitrogen atoms. Comparative Example 5 does not contain epoxy resin (B), so it is not satisfactory except for the evaluation of flame retardancy, Comparative Example 6 uses polyamideimide instead of polyester resin (A), and Comparative Example 7 uses acid-modified polypropylene, so it cannot satisfy long-term heat resistance. Thus, Comparative Examples 1 to 7 were unable to simultaneously satisfy all of the following characteristics: adhesion, solder heat resistance, long-term heat resistance, circuit embedding ability, and resin flow inhibition.

The adhesive composition of the present invention has excellent adhesion and solder heat resistance, and also exhibits long-term heat resistance. It also has good circuit embedding properties while suppressing excessive resin flow, making it useful as an adhesive for FPCs in automotive applications.

Claims

An adhesive composition comprising a polyester resin (A) and an epoxy resin (B), the epoxy resin (B) comprising at least two kinds of epoxy resins (b) having a nitrogen atom, one of the two kinds being the following epoxy resin (b1) and the other being the following epoxy resin (b2).
(b1) Resin having 3 or less functional groups (b2) Resin having 4 or more functional groups
An adhesive composition comprising a polyester resin (A) and an epoxy resin (B), the epoxy resin (B) comprising at least two kinds of epoxy resins (b) having a nitrogen atom, one of the two kinds being the following epoxy resin (b3) and the other being the following epoxy resin (b4).
(b3) A resin having a nitrogen atom that is not contained in an aromatic ring and is not adjacent to an aromatic ring. (b4) A resin having a nitrogen atom other than (b3).
The adhesive composition according to claim 1 or 2, wherein the nitrogen-containing epoxy resin (b) includes a glycidyl amine-type epoxy resin.
The adhesive composition according to claim 1 or 2, wherein the content of the epoxy resin (B) is 0.1 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the polyester resin (A).
The adhesive composition according to claim 1 or 2, further comprising an organic phosphinic acid metal salt (C).
An adhesive sheet having an adhesive layer made of the adhesive composition according to claim 1 or 2.
A laminate having the adhesive sheet according to claim 6.
A printed wiring board comprising the laminate according to claim 7 as a component.