WO2025018340A1 - Adhesive composition, and adhesive sheet, multilayer body, and printed wiring board, each of which includes said adhesive composition - Google Patents

Abstract

The present invention provides: an adhesive composition which is excellent in terms of solder heat resistance and bonding strength, and additionally has excellent dielectric characteristics with a low relative dielectric constant and a low dielectric loss tangent; and an adhesive sheet, a multilayer body, and a printed wiring board, each of which includes the adhesive composition.　An adhesive composition according to the present invention includes a polyester resin which has an acid value of 50 eq/10⁶ g to 1,000 eq/10⁶ g inclusive, an oxazoline group-containing polystyrene (A), and an epoxy resin (B). The content of the oxazoline group-containing polystyrene (A) is 12 parts by mass to 1,000 parts by mass inclusive with respect to 100 parts by mass of the polyester resin.

Description

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

The present invention relates to an adhesive composition. More specifically, the present invention relates to an adhesive composition for printed wiring boards 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.

　Since FPCs have excellent flexibility, they can accommodate the multi-functionality and miniaturization of personal computers (PCs) and smartphones, and are often used to incorporate electronic circuit boards into narrow and complex interiors. In recent years, electronic devices have become smaller, lighter, more dense, and more powerful, and the demands for the performance of wiring boards (electronic circuit boards) are becoming increasingly sophisticated. In particular, high-frequency signals are being used to increase transmission speeds. Accordingly, there is an increasing demand for low dielectric properties (low dielectric constant, low dielectric tangent) in the high-frequency range for FPCs. In order to achieve such low dielectric properties, measures have been taken to reduce the dielectric loss of FPC substrates and adhesives, and as for substrates used in FPCs, not only conventional polyimide (PI) and polyethylene terephthalate (PET), but also substrate films such as liquid crystal polymers (LCPs) and fluororesins with low dielectric properties have been proposed. As for adhesives, development of combinations of polyolefin and epoxy (Patent Document 1) and adhesives using polyphenylene ether (Patent Document 2) are being developed.

International Publication No. 2016/047289 International Publication No. 2020/196718

However, the adhesive described in Patent Document 1 is highly polar because it contains an epoxy resin and an epoxy resin curing agent, and does not satisfy the high requirements, particularly for dielectric tangent. The adhesive described in Patent Document 2 cannot be said to have excellent heat resistance as an FPC adhesive, and is also insufficient in terms of dielectric properties.

The present invention was made against the background of such problems in the conventional technology. That is, the object of the present invention is to provide an adhesive composition that has excellent solder heat resistance and adhesive strength, and further has excellent dielectric properties such as low relative dielectric constant and dielectric tangent, as well as an adhesive sheet, laminate, and printed wiring board that contain the same.

As a result of extensive research, the inventors discovered that the above problems could be solved by the means described below, and arrived at the present invention. That is, the present invention has the following configuration.

[1] A polyester resin having an acid value of 50 eq/10 ⁶ g or more and 1000 eq/10 ⁶ g or less, an oxazoline group-containing polystyrene (A), and an epoxy resin (B),
The adhesive composition, wherein the content of the oxazoline group-containing polystyrene (A) is 12 parts by mass or more and 1,000 parts by mass or less relative to 100 parts by mass of the polyester resin.
[2] The adhesive composition according to [1], wherein the polyester resin contains, as a polycarboxylic acid component constituting the polyester resin, at least one polycarboxylic acid selected from an aliphatic polycarboxylic acid, an alicyclic polycarboxylic acid, and an aromatic polycarboxylic acid, an ester of the polycarboxylic acid, or an anhydride of the polycarboxylic acid.
[3] The adhesive composition according to [1] or [2], wherein the polyester resin contains, as a polyhydric alcohol component constituting the polyester resin, at least one polyhydric alcohol selected from an aliphatic polyhydric alcohol, an alicyclic polyhydric alcohol, and an aromatic polyhydric alcohol.
[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 30 parts by mass or less per 100 parts by mass of the oxazoline group-containing polystyrene (A).
[5] The adhesive composition according to any one of [1] to [4], wherein the oxazoline group-containing polystyrene (A) is a resin obtained by copolymerizing a styrene-based monomer and an oxazoline group-containing monomer.
[6] The adhesive composition according to [5], wherein the styrene-based monomer is styrene.
[7] The adhesive composition according to [5] or [6], wherein the oxazoline group-containing monomer is at least one selected from the group consisting of 2-isopropenyl-2-oxazoline, 4,4-dimethyl-2-isopropenyl-2-oxazoline, 4-ethyl-4-hydroxymethyl-2-isopropenyl-2-oxazoline, and 4-ethyl-4-ethoxycarbonylethyl-2-isopropenyl-2-oxazoline.
[8] The adhesive composition according to any one of [1] to [7], wherein the amount of oxazoline groups in the oxazoline group-containing polystyrene (A) is 0.10 to 0.50 mmol/g.
[9] The adhesive composition according to any one of [1] to [8], wherein the weight average molecular weight (Mw) of the oxazoline group-containing polystyrene (A) is 10,000 or more and 1,000,000 or less.
[10] The adhesive composition according to any one of [1] to [9], wherein the epoxy resin (B) is a polyfunctional epoxy resin.
[11] The adhesive composition according to [10], wherein the polyfunctional epoxy resin is one or more glycidyl amine type epoxy resins selected from the group consisting of N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, triglycidyl para-aminophenol, 1,3-bis(diglycidylaminomethyl)cyclohexane, and N,N,N',N'-tetraglycidyl-m-xylylenediamine.
[12] The adhesive composition according to any one of [1] to [11], which is for use in a printed wiring board.
[13] An adhesive sheet obtained by laminating a substrate which is a resin substrate, a metal substrate or a paper substrate and a release substrate via the adhesive composition according to any one of [1] to [12].
[14] A laminate in which the adhesive composition according to any one of [1] to [12] is laminated on a substrate which is a resin substrate, a metal substrate, or a paper substrate.
[15] A printed wiring board comprising the laminate according to [14] as a component.

The adhesive composition of the present invention has excellent solder heat resistance and adhesive strength, as well as excellent dielectric properties. For this reason, it is suitable for use in adhesives, adhesive sheets, laminates, and printed wiring boards for FPCs in the high frequency range.

Below, one embodiment of the present invention is described in detail. However, the present invention is not limited to this embodiment, and can be implemented in various modified forms within the scope described above.

<Adhesive Composition>
The adhesive composition of the present invention comprises a polyester resin having an acid value of 50 eq/ ¹⁰ g or more and 1,000 eq/ ¹⁰ g or less, an oxazoline group-containing polystyrene (A) and an epoxy resin (B), in which the content of the oxazoline group-containing polystyrene (A) is 12 parts by mass or more and 1,000 parts by mass or less per 100 parts by mass of the polyester resin.
In the present invention, by blending a predetermined amount of oxazoline group-containing polystyrene (A) with an adhesive composition containing a polyester resin having a specific acid value and an epoxy resin (B), the carboxy groups in the polyester resin react not only with the epoxy resin (B) but also with the oxazoline group-containing polystyrene (A) to form a high-density crosslinked structure and also suppress the generation of hydroxyl groups, thereby providing an adhesive composition that has excellent solder heat resistance, adhesive strength, and also excellent dielectric properties.

<Oxazoline Group-Containing Polystyrene (A)>
The oxazoline group-containing polystyrene (A) in the present invention is preferably a resin obtained by copolymerizing a styrene-based monomer and an oxazoline group-containing monomer. In other words, the oxazoline group-containing polystyrene (A) is a copolymer having a structural unit derived from a styrene-based monomer and a structural unit derived from an oxazoline group-containing monomer. By containing an oxazoline group, when reacting with a carboxy group of a polyester resin, a highly heat-resistant crosslink can be formed without generating a hydroxyl group that adversely affects the dielectric properties. In addition, since the styrene-based monomer itself has low dielectric properties, by copolymerizing the styrene-based monomer, it is possible to develop excellent dielectric properties even as an adhesive.

As the styrene-based monomer constituting the oxazoline group-containing polystyrene (A), styrene and its derivatives can be used. Specific examples include styrene; alkyl styrenes such as α-methylstyrene, methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene, diethylstyrene, triethylstyrene, propylstyrene, butylstyrene, hexylstyrene, heptylstyrene, and octylstyrene; and halogenated styrenes such as chlorostyrene, fluorostyrene, bromostyrene, dibromostyrene, and iodostyrene. Of these, styrene is preferred.

The oxazoline group-containing monomer constituting the oxazoline group-containing polystyrene (A) is not particularly limited in terms of its skeleton as long as it contains an oxazoline group and is copolymerizable with a styrene-based monomer, but a monomer having an oxazoline group and a vinyl group can be preferably used. Examples of the oxazoline group-containing vinyl monomer include 2-vinyl-2-oxazoline, 5-methyl-2-vinyl-2-oxazoline, 4,4-dimethyl-2-vinyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 4,4-dimethyl-2-isopropenyl-2-oxazoline, 4-ethyl-4-hydroxymethyl-2-isopropenyl-2-oxazoline, 4-ethyl-4-ethoxycarbonylethyl-2-isopropenyl-2-oxazoline, 4-acryloyloxymethyl-2,4-dimethyl-2-oxazoline, 4-methacryloyloxymethyl-2,4-dimethyl-2-oxazoline, 4-methacryloyloxymethyl-2-phenyl-4-methyl-2-oxazoline, and 2-(4-vinylphenyl)-4,4-dimethyl-2-oxazoline. Among these, one or more selected from the group consisting of 2-isopropenyl-2-oxazoline, 4,4-dimethyl-2-isopropenyl-2-oxazoline, 4-ethyl-4-hydroxymethyl-2-isopropenyl-2-oxazoline, and 4-ethyl-4-ethoxycarbonylethyl-2-isopropenyl-2-oxazoline are preferred, with 2-isopropenyl-2-oxazoline being more preferred.

The oxazoline group-containing polystyrene (A) may contain one or more other monomers as its constituents in addition to the styrene monomer and the oxazoline group-containing monomer. The other monomers are not particularly limited as long as they are copolymerizable with these monomers, and examples thereof include (meth)acrylate monomers, (meth)acrylic ester monomers, and (meth)acrylamide monomers. The proportion of other monomers other than the styrene monomer and the oxazoline group-containing monomer is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, relative to 100% by mass of all monomers constituting the oxazoline group-containing polystyrene (A). The lower limit is not particularly limited, but is 0% by mass.

The ratio of each monomer constituting the oxazoline group-containing polystyrene (A) is not particularly limited, but a resin obtained by copolymerizing preferably 5% by mass to 50% by mass, more preferably 10% by mass to 30% by mass of oxazoline group-containing monomers relative to 100% by mass of all monomers constituting the oxazoline group-containing polystyrene (A) is preferred. By using oxazoline group-containing monomers within the above range, sufficient reaction sites are obtained, and the polyester resin and oxazoline group-containing polystyrene (A) can be crosslinked at a high density to obtain good durability.

The oxazoline group-containing polystyrene (A) preferably has at least one oxazoline group per molecule, more preferably two or more. The more oxazoline groups in one molecule, the more likely it is that a high-density crosslinked structure can be formed with the carboxy groups in the polyester resin. The amount of oxazoline groups in the oxazoline group-containing polystyrene (A) is preferably 0.10 to 0.50 mmol/g, more preferably 0.15 to 0.40 mmol/g. If the amount of oxazoline groups is within the above range, the reactions of the polyester resin, the oxazoline group-containing polystyrene (A), and the epoxy resin (B) proceed in a well-balanced manner.

The weight average molecular weight (Mw) of the oxazoline group-containing polystyrene (A) is preferably 10,000 or more and 1,000,000 or less, more preferably 20,000 or more and 500,000 or less, even more preferably 50,000 or more and 400,000 or less, and even more preferably 100,000 or more and 300,000 or less. By setting it below the upper limit, the viscosity of the oxazoline group-containing polystyrene (A) when dissolved in a solvent falls within a range suitable for coating, and excellent coating appearance can be achieved. In addition, by setting it above the lower limit, excellent solder heat resistance can be achieved.

Oxazoline group-containing polystyrene (A) is also available as a commercial product such as "Epocross RPS-1005" (manufactured by Nippon Shokubai).

The content of the oxazoline group-containing polystyrene (A) in the adhesive composition of the present invention is 12 parts by mass or more and 1000 parts by mass or less, more preferably 20 parts by mass or more and 500 parts by mass or less, and even more preferably 50 parts by mass or more and 200 parts by mass or less, per 100 parts by mass of the polyester resin (particularly the solid content of the polyester resin). Outside the above range, crosslinking due to the reaction between the oxazoline group and the carboxy group is insufficient, and the solder heat resistance may deteriorate. Furthermore, when the content of the oxazoline group-containing polystyrene (A) is within the above range, the dielectric tangent tends to be good. In other words, by keeping it within the above upper and lower limit ranges, excellent dielectric properties and solder heat resistance can be exhibited.

<Polyester Resin>
The polyester resin 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 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, benzophenonetetracarboxylic acid, and pyromellitic anhydride (PMDA). As well as esters and acid anhydrides thereof, examples of the aromatic polycarboxylic acids include those that are particularly preferred, and naphthalenedicarboxylic acid and terephthalic acid are more preferred. By using an aromatic polycarboxylic acid, the dielectric properties and solder heat resistance of the adhesive composition can be improved.

The polyhydric alcohol constituting the polyester resin is not particularly limited, but examples thereof include aliphatic polyhydric alcohols, alicyclic polyhydric alcohols, and aromatic polyhydric alcohols, with aliphatic polyhydric alcohols and alicyclic polyhydric alcohols being more preferred. 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, and 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, polyhydric alcohols having an alkylene group having 4 or more carbon atoms are preferred, and examples thereof 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 preferred. By using a polyhydric alcohol having 4 or more carbon atoms, the dielectric properties and adhesive strength of the adhesive composition can be improved. Alicyclic polyhydric alcohols are also preferred, and tricyclodecane dimethanol is particularly preferred. As the polyhydric alcohol constituting the polyester resin, aliphatic polyhydric alcohols and/or aromatic polyhydric alcohols are preferred, and aliphatic polyhydric alcohols and aromatic polyhydric alcohols are more preferred.

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

The polyester used in the present invention may be copolymerized with a trivalent or higher polyvalent carboxylic acid component and/or a trivalent or higher polyhydric alcohol component. Examples of trivalent or higher polyvalent carboxylic acid components include aromatic carboxylic acids such as trimellitic acid, pyromellitic acid, benzophenonetetracarboxylic acid, trimesic acid, trimellitic anhydride (TMA), and pyromellitic anhydride (PMDA), and aliphatic carboxylic acids such as 1,2,3,4-butanetetracarboxylic acid, and one or more of these can be used. Examples of trivalent or higher polyhydric alcohol components include glycerin, trimethylolpropane, trimethylolethane, pentaerythritol, α-methylglucose, mannitol, and sorbitol, and one or more of these can be used. However, if the copolymerization amount of trivalent or higher polyvalent carboxylic acid components and/or trivalent or higher polyhydric alcohol components is large, the dielectric properties of the polyester may deteriorate, which is not preferable. When a trivalent or higher polyvalent carboxylic acid component and/or a trivalent or higher polyhydric alcohol component are copolymerized, the amount is preferably 8 mol% or less, more preferably 6 mol% or less, out of a total of 100 mol% of all constituent components, and although there is no lower limit, is 0.5 mol% or more.

　The polymerization condensation reaction method for producing the polyester resin 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 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 acetates of magnesium, iron, zinc, manganese, cobalt, and aluminum can be used. These catalysts can be used alone or in combination of two or more.

The weight average molecular weight of the polyester resin used in the present invention is preferably 1,000,000 or less, and more preferably 500,000 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 used in the present invention is preferably 0°C or higher, and more preferably 10°C or higher. It is also preferably 200°C or lower, and more preferably 100°C or lower. If it is within the above range, it can be an adhesive composition with excellent adhesion.

The acid value of the polyester resin used in the present invention is 50 eq/10 ⁶ g or more, more preferably 80 eq/10 ⁶ g or more, and even more preferably 100 eq/10 ⁶ g or more. By making the acid value 50 eq/10 ⁶ g or more, the reaction points with the oxazoline group-containing polystyrene (A) and the epoxy resin (B) are increased, and a tough adhesive layer with high crosslink density can be formed after curing, and the solder heat resistance is excellent. The upper limit of the acid value of the polyester resin is 1000 eq/10 ⁶ g or less, more preferably 700 eq/10 ⁶ g or less, and even more preferably 500 eq/10 ⁶ g or less. By making the acid value 1000 eq/10 ⁶ g or less, the adhesiveness and low dielectric properties become better.

　Methods for increasing the acid value of the polyester used in the present invention include, for example, (1) a method of 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 completion of the polycondensation reaction and reacting (acid addition), and (2) a method of intentionally modifying the resin by applying heat, oxygen, water, etc. during the polycondensation reaction, and these can be performed arbitrarily. The polyvalent carboxylic acid anhydride used for acid addition 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 bisanhydrotrimellitate, and these can be used alone or in combination of two or more. Trimellitic anhydride is preferable.

The polyester resin of the present invention preferably has a relative dielectric constant (εc) of 2.9 or less at a frequency of 10 GHz. More preferably, it is 2.8 or less, and even more preferably, it is 2.7 or less. There is no particular lower limit, but in practical use, it is 2.0. Furthermore, the relative dielectric constant (εc) over the entire frequency range of 1 GHz to 60 GHz is preferably 2.9 or less, more preferably 2.8 or less, and even more preferably 2.7 or less.

The polyester resin of the present invention preferably has a dielectric loss tangent (tan δ) of 0.005 or less at a frequency of 10 GHz. More preferably, it is 0.003 or less, and even more preferably, it is 0.002 or less. There is no particular lower limit, but in practical use, it is 0.0001 or more. Furthermore, the dielectric loss tangent (tan δ) over the entire frequency range of 1 GHz to 60 GHz is preferably 0.005 or less, more preferably 0.003 or less, and even more preferably 0.002 or less.

The content of polyester resin in the adhesive composition of the present invention is preferably 5% by mass or more, more preferably 20% by mass or more, and even more preferably 30% 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 95% by mass or less, even more preferably 90% by mass or less, and even more preferably 80% by mass or less. If it is within the above range, it is preferable because it provides good adhesion and heat resistance.

<Epoxy resin>
The adhesive composition of the present invention contains an epoxy resin (B). The epoxy resin used in the present invention is not particularly limited as long as it has an epoxy group in the molecule, but is preferably a multifunctional epoxy resin having two or more, more preferably three or more, epoxy groups in the molecule. Specifically, it is not particularly limited, but includes 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, glycidylamine type epoxy resin, epoxy modified polybutadiene, etc., among which biphenyl type epoxy resin, novolac type epoxy resin, dicyclopentadiene type epoxy resin, glycidylamine type epoxy resin, epoxy modified polybutadiene, glycidyl group-containing isocyanuric acid (e.g., diallyl monoglycidyl isocyanurate, diglycidyl monoallyl isocyanurate, etc.) is preferable, and glycidylamine type epoxy resin is more preferable. Examples of the glycidylamine type epoxy resin include N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, triglycidyl para-aminophenol, 1,3-bis(diglycidylaminomethyl)cyclohexane, N,N,N',N'-tetraglycidyl-m-xylylenediamine, and the like. Of these, triglycidyl para-aminophenol and N,N,N',N'-tetraglycidyl-m-xylylenediamine are preferred, and triglycidyl para-aminophenol is more preferred.

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 0.5 parts by mass or more, and even more preferably 1 part by mass or more, relative to 100 parts by mass of polyester resin. By making it 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 10 parts by mass or less, more preferably 5 parts by mass or less. By making it equal to or less than the upper limit, the pot life and low dielectric properties become good. In other words, by making it within the above range, an adhesive composition having excellent low dielectric properties in addition to adhesion and solder heat resistance can be obtained.

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 0.5 parts by mass or more, and even more preferably 1.0 parts by mass or more, relative to 100 parts by mass of the oxazoline group-containing polystyrene (A). Also, it is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less. If the content of the epoxy resin (B) relative to the oxazoline group-containing polystyrene (A) is within the above range, the oxazoline group-carboxy group and the epoxy group-carboxy group will each react sufficiently, suppressing the remaining of unreacted functional groups, increasing the crosslinking density, and improving the solder heat resistance. Also, by making it equal to or more than the lower limit, the adhesion will be good, and by making it equal to or less than the upper limit, the solder heat resistance will be good.

<Polycarbodiimide>
The adhesive composition of the present invention may contain polycarbodiimide. The polycarbodiimide is not particularly limited as long as it has two or more carbodiimide bonds in the molecule. By using polycarbodiimide, the carboxy group of the polyester resin or the epoxy group of the epoxy resin (B) reacts with the carbodiimide bond, thereby improving heat resistance and adhesiveness.

In the adhesive composition of the present invention, the content of polycarbodiimide is preferably 1 part by mass or more, more preferably 3 parts by mass or more, per 100 parts by mass of polyester resin. By making it equal to or more than the lower limit, the crosslinking density can be increased, and solder heat resistance is improved. Also, it is preferably 20 parts by mass or less, more preferably 10 parts by mass or less. By making it equal to or less than the upper limit, excellent solder heat resistance and low dielectric properties can be achieved. In other words, by making it within the above range, an adhesive composition having excellent solder heat resistance and low dielectric properties can be obtained.

<Unsaturated Hydrocarbons>
The adhesive composition of the present invention may contain an unsaturated hydrocarbon having a terminal unsaturated hydrocarbon group and a 5% weight loss temperature of 260°C or higher. When the unsaturated hydrocarbon contains the terminal unsaturated hydrocarbon group, the crosslink density can be increased by a curing reaction caused by radicals generated by using a radical initiator or the like, thereby improving the solder heat resistance. In addition, since no hydroxyl groups that deteriorate the dielectric properties are generated after the reaction, an adhesive having better dielectric properties can be obtained. It is preferable that one molecule has two or more terminal unsaturated hydrocarbon groups, since this can further increase the crosslink density.

The 5% weight loss temperature of the unsaturated hydrocarbon must be 260°C or higher. It is preferably 270°C or higher, more preferably 280°C or higher, and even more preferably 290°C or higher. By having a 5% weight loss temperature above this value, soldering can be performed without causing appearance defects even at temperatures exceeding the melting point of the solder. There is no particular upper limit, but 500°C is practical.

The unsaturated hydrocarbon preferably has an aromatic ring structure or an alicyclic structure as a structural unit. By having an aromatic ring structure or an alicyclic structure as a structural unit, the solder heat resistance can be improved and the dielectric properties are also excellent. In particular, it is preferable for the unsaturated hydrocarbon to have an aromatic ring structure or an alicyclic structure as the skeleton, and polyphenylene ether or phenol resin is preferable. Specific examples of polyphenylene ethers having terminal unsaturated hydrocarbon groups include SA-9000 from SABIC and OPE-2St from Mitsubishi Gas Chemical Company. In addition, an example of a phenol resin having terminal unsaturated hydrocarbon groups is Resitop FTC-809AE from Gun-ei Chemical Industry Co., Ltd.

The number average molecular weight of the unsaturated hydrocarbon is preferably 500 or more, and more preferably 1,000 or more. It is also preferably 100,000 or less, more preferably 10,000 or less, and even more preferably 5,000 or less. If it is within the above range, it has good solubility in solvents and can form a uniform adhesive coating.

The content of unsaturated hydrocarbons in the adhesive composition of the present invention is preferably 1 part by mass or more, and more preferably 2 parts by mass or more, per 100 parts by mass of polyester resin. Also, it is preferably 100 parts by mass or less, and more preferably 50 parts by mass or less. Within the above range, both excellent adhesion and solder heat resistance can be achieved.

<Radical Generator>
The adhesive composition of the present invention preferably contains a radical generator. The radicals generated by the radical generator efficiently react the terminal unsaturated hydrocarbon groups of the unsaturated hydrocarbon with each other, increasing the crosslinking density, thereby improving the solder heat resistance and dielectric properties. The radical generator is not particularly limited, but it is preferable to use an organic peroxide. The organic peroxide is not particularly limited, but examples thereof include peroxides such as di-tert-butyl peroxyphthalate, tert-butyl hydroperoxide, dicumyl peroxide, benzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxypivalate, methyl ethyl ketone peroxide, di-tert-butyl peroxide, and lauroyl peroxide; and azonitriles such as azobisisobutyronitrile and azobisisopropionitrile.

The one-minute half-life temperature of the radical generator used in the present invention is preferably 140°C or higher. By setting the temperature at 140°C or higher, the initiation of a radical reaction can be prevented when the solvent of the adhesive composition varnish is volatilized to prepare the adhesive sheet, and excellent adhesive properties can be achieved.

The amount of the radical generator used in the present invention is preferably 0.1 parts by mass or more, and more preferably 1 part by mass or more, per 100 parts by mass of the unsaturated hydrocarbon. Also, it is preferably 50 parts by mass or less, and more preferably 10 parts by mass or less. By keeping it within the above range, an optimal crosslink density can be achieved, and both adhesion and solder heat resistance can be achieved.

<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, the oxazoline group-containing polystyrene (A) and the epoxy resin (B). Specifically, for example, aromatic hydrocarbons such as benzene, toluene, xylene, etc.; aliphatic hydrocarbons such as hexane, heptane, octane, decane, etc.; alicyclic hydrocarbons such as cyclohexane, cyclohexene, methylcyclohexane, ethylcyclohexane, etc.; halogenated hydrocarbons such as trichloroethylene, dichloroethylene, chlorobenzene, chloroform, etc.; alcohol solvents such as methanol, ethanol, isopropyl alcohol, butanol, pentanol, hexanol, propanediol, phenol, etc.; acetone, methyl isobutyl ketone, methyl ethyl ketone, pentanone, hexanone, cyclohexanone, isophorone, acetophenone, etc. ketone-based solvents, cellosolves such as methyl cellosolve and ethyl cellosolve, ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, methyl propionate and butyl formate, glycol ether-based 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 of these. In particular, methylcyclohexane and toluene are preferred from the viewpoints of working environment and drying properties.

The organic solvent is preferably in the range of 100 to 1000 parts by mass per 100 parts by mass of the solid content of the adhesive composition. By making it equal to or greater than the lower limit, the liquid state and pot life will be good. In addition, by making it equal to or less than the upper limit, it will be 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 flame retardants, tackifiers, fillers, antioxidants, silane coupling agents, etc.

<Flame retardants>
The adhesive composition of the present invention may contain a flame retardant as necessary. Examples of flame retardants include bromine-based, phosphorus-based, nitrogen-based, and metal hydroxide compounds. Among them, phosphorus-based flame retardants are preferred, and known phosphorus-based flame retardants such as phosphate esters, for example, trimethyl phosphate, triphenyl phosphate, and tricresyl phosphate, phosphate salts, for example, aluminum phosphinate, and phosphazenes can be used. These may be used alone or in any combination of two or more. When a flame retardant is contained, it is preferable to contain the flame retardant in a range 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, the oxazoline group-containing polystyrene (A), and the epoxy resin (B) in total. By keeping the amount within the above range, flame retardancy can be expressed while maintaining adhesion, solder heat resistance, and electrical properties.

<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, per 100 parts by mass of the total of the polyester resin, the oxazoline group-containing polystyrene (A), and the epoxy resin (B). By keeping it within the above range, the effect of the tackifier can be expressed while maintaining the adhesiveness, solder heat resistance, and electrical properties.

<Filler>
The adhesive composition of the present invention may contain a filler as necessary. 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 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 heat resistance improvement effect.

Hydrophobic silica and hydrophilic silica are generally known as silica, but in this case, hydrophobic silica treated with dimethyldichlorosilane, hexamethyldisilazane, octylsilane, etc. is better for imparting moisture absorption resistance. When silica is added, the amount of silica added is preferably 0.05 to 30 parts by mass per 100 parts by mass of polyester resin, oxazoline group-containing polystyrene (A), and epoxy resin (B) combined. By adding an amount equal to or greater than the lower limit, further heat resistance can be achieved. By adding an amount equal to or less than the upper limit, poor dispersion of silica and excessively high solution viscosity can be prevented, improving workability.

<Antioxidants>
The adhesive composition of the present invention may contain an antioxidant as necessary. By adding an antioxidant, it is possible to suppress the deterioration of properties such as adhesion and dielectric properties even when the adhesive composition is used in a high-temperature environment exposed to air, which is preferable. The antioxidant is not particularly limited, but examples thereof include phenol-based antioxidants, amine-based antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants. These may be used alone or in combination of two or more.

If the adhesive composition contains an antioxidant, the content is preferably 0.5 to 5 parts by mass, and more preferably 1 to 3 parts by mass, per 100 parts by mass of the solid content of the adhesive composition. If the content of the antioxidant is within the above range, it is possible to prevent deterioration of properties such as adhesion and dielectric properties even when the adhesive composition is used in a high-temperature environment exposed to air.

<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 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, silane coupling agents having an epoxy group such as γ-glycidoxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltriethoxysilane are more preferred from the viewpoint of heat resistance. 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, the oxazoline group-containing polystyrene (A), and the epoxy resin (B). By keeping the amount within the above range, solder heat resistance and adhesiveness can be improved.

<Laminate>
The laminate of the present invention is a laminate in which an adhesive composition is laminated on a substrate, specifically, a laminate in which an adhesive composition is laminated 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. Examples of the substrate include resin substrates such as film-like resins, metal substrates such as metal plates and metal foils, and papers.

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 substrate 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 properties and easy to use. Furthermore, if a release substrate is applied and dried, and then another release substrate is attached as necessary, it becomes possible to transfer the adhesive layer itself to another substrate.

<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 includes a comma coater, a reverse roll coater, a die coater, etc. 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 blisters are 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 blisters are less likely to occur.

<Printed Wiring Board>
The printed wiring board in the present invention includes, as a component, a laminate formed of 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 not only to conventional polyimide, polyester film, and copper foil that constitute printed wiring boards, but also to low-polarity resin substrates such as LCP, and can provide solder reflow resistance, and the adhesive layer itself has excellent low dielectric properties. Therefore, it is suitable as an adhesive composition for use in coverlay films, laminates, resin-coated copper foil, and bonding sheets.

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. In particular, the film has excellent adhesion to low-polarity substrates such as liquid crystal polymers, polyphenylene sulfide, syndiotactic polystyrene, and polyolefin 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 or a liquid crystal polymer 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 preferable.

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 bonded together to produce a printed wiring board. Any method can be used to bond them together, and for example, they can be bonded together using a press or roll. They can also be bonded together while heating them, for example, using a hot press or a hot 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. 2023-118371, filed on July 20, 2023. The entire contents of the specification of Japanese Patent Application No. 2023-118371, filed on July 20, 2023, 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>
(Acid value measurement)
In the present invention, the acid value (equivalent/10 ⁶ g) was measured by dissolving the polyester resin in toluene and titrating it with a methanol solution of sodium methoxide using phenolphthalein as an indicator.

(Weight average molecular weight (Mw))
The weight average molecular weight in the present invention is measured by gel permeation chromatography (hereinafter, GPC, standard substance: polystyrene resin, mobile phase: tetrahydrofuran, column: Shodex KF-802 + KF-804L + KF-806L, column The values were measured using a temperature of 30° C., a flow rate of 1.0 ml/min, and a detector: an RI detector.

(Measurement of Glass Transition Temperature)
Measurement was performed using a differential scanning calorimeter (DSC-200, SII). 5 mg of the sample 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.

Below are examples of the production of adhesive compositions that serve as examples of the present invention, and comparative examples of adhesive compositions.

The polyester resin was prepared as follows.
(Production Example 1)
In a reaction vessel equipped with a stirrer, a condenser, and a thermometer, 223 parts of dimethyl naphthalene dicarboxylate, 390 parts of dimer diol, 90 parts of tricyclodecane dimethanol, and 0.03 mol% of tetrabutyl orthotitanate as a catalyst were charged relative to the total 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 raised 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 9 parts of trimellitic anhydride were added, and the reaction was carried out at 220°C for 30 minutes to carry out post-acid addition, and the product was taken out. As a result of composition analysis by NMR, the obtained polyester resin had a molar ratio of naphthalene dicarboxylic acid/dimer diol/tricyclodecane dimethanol/trimellitic anhydride = 100/45/50/10 [molar ratio]. The glass transition temperature was 25° C., the acid value was 360 eq/10 ⁶ g, and the weight average molecular weight was 50,000.

As the oxazoline group-containing polystyrene (A), the following was used.
Oxazoline group-containing polystyrene: EPOCROS RPS-1005 (manufactured by Nippon Shokubai, weight average molecular weight 160,000, oxazoline group amount 0.27 mmol/g)

As the epoxy resin (B), the following was used.
Epoxy resin: EP-3950E (manufactured by ADEKA, triglycidyl paraaminophenol)

Example 1
60 parts of the oxazoline group-containing polystyrene (A), 40 parts of the polyester resin, and 1 part of the epoxy resin (B) were mixed and dissolved in toluene to a solids concentration of 30%, to obtain a toluene adhesive composition (S1).
The adhesive composition (S1) thus obtained was evaluated for its relative dielectric constant, dielectric loss tangent, peel strength, and solder heat resistance. The results are shown in Table 1.

<Examples 2 to 3, Comparative Examples 1 to 5>
Adhesive compositions (S2) to (S8) were prepared and evaluated in the same manner as in Example 1, except that the types and amounts of each component of the adhesive composition were changed as shown in Tables 1 and 2. The results are shown in Tables 1 and 2.

<Evaluation of Adhesive Composition>
(Dielectric constant (εc) and dielectric tangent (tan δ))
The adhesive composition was applied to a 100 μm thick Teflon (registered trademark) sheet so that the thickness after drying was 25 μm, and dried at 130 ° C for 3 minutes. Then, after hardening by heat treatment at 180 ° C for 3 hours, the Teflon (registered trademark) sheet was peeled off to obtain an adhesive resin sheet for testing. The obtained adhesive resin sheet for testing was then cut into a rectangular sample of 8 cm × 3 mm to obtain a test sample. The relative dielectric constant (εc) and dielectric loss tangent (tan δ) were measured using a network analyzer (manufactured by Anritsu Corporation) by a cavity resonator perturbation method at a temperature of 23 ° C and a frequency of 10 GHz.
<Evaluation criteria for dielectric constant>
○: Less than 2.5 △: 2.5 or more and 2.7 or less ×: More than 2.7 <Evaluation criteria for dielectric tangent>
○: 0.002 or less △: More than 0.002 and 0.003 or less ×: More than 0.003

(Peel strength (adhesiveness))
The adhesive composition was applied to 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) thus obtained 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 surface of the rolled copper foil was in contact with the adhesive layer, and the adhesive was bonded. The laminate was then heat-treated at 180 ° C for 3 hours to harden the film, and a peel strength evaluation sample 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 △: 0.7 N/mm or more but less than 1.0 N/mm ×: Less than 0.7 N/mm

(solder heat resistance)
An evaluation sample was prepared in the same manner as for measuring the peel strength described above, and a 2.0 cm x 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

As is clear from Table 1, Examples 1 to 3 are excellent in dielectric properties, peel strength, and solder heat resistance. Furthermore, a comparison of Examples 1 to 3 shows that the dielectric properties, peel strength, and solder heat resistance can be changed by adjusting the content ratio of polyester resin, oxazoline group-containing polystyrene (A), and epoxy resin (B).

On the other hand, in Comparative Example 1, since the oxazoline group-containing polystyrene (A) was not contained, crosslinking was not sufficiently formed, and the dielectric tangent and solder heat resistance were deteriorated.
In Comparative Example 2, since a larger amount of epoxy resin (B) is contained compared to Comparative Example 1, the solder heat resistance is excellent. On the other hand, since a larger amount of hydroxyl groups is generated, the dielectric tangent is deteriorated.
In Comparative Example 3, since the epoxy resin (B) was not contained as compared with Example 1, the number of polar groups that interact with the acid-modified resin base material was small, and the peel strength and solder heat resistance were deteriorated.
In Comparative Example 4, the amount of the oxazoline group-containing polystyrene (A) relative to the polyester resin was too small, so that crosslinking was not sufficiently formed, and the dielectric loss tangent and solder heat resistance were deteriorated.
In Comparative Example 5, the amount of oxazoline group-containing polystyrene (A) relative to the polyester resin was too large, so that the polar groups interacting with the acid-modified resin base material were relatively small, and the peel strength and solder heat resistance were deteriorated.

The adhesive composition of the present invention has excellent solder heat resistance and adhesive strength, as well as a good dielectric constant and dielectric tangent. Therefore, it is useful as an adhesive or adhesive sheet for FPCs in the high frequency range.

Claims (15)

The composition comprises a polyester resin having an acid value of 50 eq/10 ⁶ g or more and 1000 eq/10 ⁶ g or less, an oxazoline group-containing polystyrene (A), and an epoxy resin (B),
The adhesive composition, wherein the content of the oxazoline group-containing polystyrene (A) is 12 parts by mass or more and 1,000 parts by mass or less relative to 100 parts by mass of the polyester resin. The adhesive composition according to claim 1, wherein the polyester resin contains, as a polycarboxylic acid component constituting the polyester resin, at least one polycarboxylic acid selected from an aliphatic polycarboxylic acid, an alicyclic polycarboxylic acid, and an aromatic polycarboxylic acid, an ester of the polycarboxylic acid, or an anhydride of the polycarboxylic acid. The adhesive composition according to claim 1 or 2, wherein the polyester resin contains at least one polyhydric alcohol selected from aliphatic polyhydric alcohols, alicyclic polyhydric alcohols, and aromatic polyhydric alcohols as a polyhydric alcohol component constituting the polyester 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 30 parts by mass or less per 100 parts by mass of the oxazoline group-containing polystyrene (A). The adhesive composition according to claim 1 or 2, wherein the oxazoline group-containing polystyrene (A) is a resin obtained by copolymerizing a styrene-based monomer and an oxazoline group-containing monomer. The adhesive composition according to claim 5, wherein the styrene-based monomer is styrene. The adhesive composition according to claim 5, wherein the oxazoline group-containing monomer is at least one selected from the group consisting of 2-isopropenyl-2-oxazoline, 4,4-dimethyl-2-isopropenyl-2-oxazoline, 4-ethyl-4-hydroxymethyl-2-isopropenyl-2-oxazoline, and 4-ethyl-4-ethoxycarbonylethyl-2-isopropenyl-2-oxazoline. The adhesive composition according to claim 1 or 2, wherein the amount of oxazoline groups in the oxazoline group-containing polystyrene (A) is 0.10 to 0.50 mmol/g. The adhesive composition according to claim 1 or 2, wherein the weight average molecular weight (Mw) of the oxazoline group-containing polystyrene (A) is 10,000 or more and 1,000,000 or less. The adhesive composition according to claim 1 or 2, wherein the epoxy resin (B) is a multifunctional epoxy resin. The adhesive composition according to claim 10, wherein the multifunctional epoxy resin is one or more glycidylamine type epoxy resins selected from the group consisting of N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, triglycidyl paraaminophenol, 1,3-bis(diglycidylaminomethyl)cyclohexane, and N,N,N',N'-tetraglycidyl-m-xylylenediamine. The adhesive composition according to claim 1 or 2, which is for use on printed wiring boards. An adhesive sheet in which a substrate, which is a resin substrate, a metal substrate, or a paper substrate, and a release substrate are laminated via the adhesive composition according to claim 1 or 2. A laminate in which the adhesive composition according to claim 1 or 2 is laminated onto a substrate that is a resin substrate, a metal substrate, or a paper substrate. A printed wiring board comprising the laminate according to claim 14 as a component.