WO2025142569A1 - Adhesive composition, bonding film, laminate with adhesive layer, and laminate - Google Patents

Abstract

This adhesive composition (100) contains: a base material resin (A) which contains at least one resin that is selected from the group consisting of a polyamide resin and a polyurethane resin; an epoxy compound (B) in an amount of 1 part by mass to 50 parts by mass inclusive relative to 100 parts by mass of the base material resin (A); a triazine compound (C) in an amount of 10 parts by mass to 70 parts by mass inclusive relative to 100 parts by mass of the base material resin (A); and a metal phosphinate (D) in an amount of 0.5 part by mass to 50 parts by mass inclusive relative to 100 parts by mass of the base material resin (A). The triazine compound (C) contains a specific structure in the molecular structure thereof.

Description

Adhesive composition, bonding film, laminate with adhesive layer, and laminate

The present invention relates to an adhesive composition, a bonding film, a laminate with an adhesive layer, and a laminate.

Flexible printed circuit boards (hereafter referred to as "FPCs") are capable of three-dimensional, high-density mounting even in limited spaces, and so their uses are expanding. In recent years, as electronic devices have become smaller and lighter, FPC-related products have become more diverse and demand is increasing.

　Products related to such FPCs include, for example, flexible copper-clad laminates made by bonding polyimide film and copper foil together, flexible printed wiring boards in which electronic circuits are formed on flexible copper-clad laminates, flexible printed wiring boards with reinforcement plates made by bonding flexible printed wiring boards and reinforcement plates together, multilayer boards made by stacking and bonding flexible copper-clad laminates or flexible printed wiring boards, and flexible flat cables (hereinafter also referred to as "FFCs") in which copper wiring is bonded to a base film, and adhesives are usually used when manufacturing these.

When manufacturing FPCs or FPC-related products, a laminate with an adhesive layer called a "coverlay film" may be used to protect the wiring. A coverlay film comprises an insulating base film and an adhesive layer formed on its surface, with polyimide resin being widely used as the material for the base film. A flexible printed wiring board is then manufactured by, for example, attaching the coverlay film via the adhesive layer to the surface having the wiring using a heat press or the like.

Furthermore, as a type of printed wiring board, a build-up type multilayer printed wiring board is known in which conductor layers and organic insulating layers are alternately laminated on the surface of a substrate. In a multilayer printed wiring board, an insulating adhesive layer is interposed between the conductor layer and the organic insulating layer, and the conductor layer and the organic insulating layer are bonded via the insulating adhesive layer. A sheet made of an adhesive in an uncured or semi-cured state, known as a "bonding film," is used to form the insulating adhesive layer.

For example, Patent Document 1 describes an adhesive composition used in FPCs and FPC-related products, which contains (A) a thermoplastic resin, (B) a phosphorus-containing phenoxy resin, (C) a phosphorus-containing epoxy resin, and (D) a hardener. In addition, phosphorus compounds such as triphenyl phosphate may be added to this type of adhesive composition as a flame retardant.

JP 2003-298230 A

However, the cured product of the adhesive composition in Patent Document 1 has the problem that its heat resistance is easily reduced when it absorbs moisture.

The present invention was made in consideration of these problems, and aims to provide an adhesive composition capable of forming a cured product that exhibits excellent heat resistance even in a hygroscopic state, as well as a bonding film, a laminate with an adhesive layer, and a laminate made using this adhesive composition.

A first aspect of the present invention resides in an adhesive composition according to the following items [1] to [6].
[1] A base resin (A) containing at least one resin selected from the group consisting of polyamide-based resins and polyurethane-based resins;
an epoxy compound (B) of 1 part by mass or more and 50 parts by mass or less per 100 parts by mass of the base resin (A);
a triazine-based compound (C) of 10 parts by mass or more and 70 parts by mass or less per 100 parts by mass of the base resin (A);
and a metal phosphinate (D) in an amount of 0.5 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the base resin (A),
The adhesive composition, wherein the triazine compound (C) contains, in its molecular structure, one or more structures selected from a structure represented by the following general formula (C1) and a structure represented by the following structural formula (C2):

In the general formula (C1), R ¹ to R ³ each independently represent an amino group, a hydroxyl group, a thiol group, a methyl group, or a phenyl group.

[2] The adhesive composition according to [1], in which the triazine compound (C) contains a structure represented by the following structural formula (C3) in its molecular structure.

[3] The adhesive composition according to [1] or [2], wherein the triazine compound (C) has a volume-based median diameter of 10 μm or less.
[4] The adhesive composition according to any one of [1] to [3], wherein the base resin (A) contains a polyester polyamide as a polyamide-based resin.
[5] The adhesive composition according to any one of [1] to [4], wherein the base resin (A) contains a polyester polyurethane as a polyurethane-based resin.
[6] The adhesive composition according to any one of [1] to [5], wherein the base resin (A) contains a polyurethane resin having a polyphenylene ether skeleton containing a plurality of phenylene groups and ether bonds bonding the phenylene groups to each other.

A second aspect of the present invention is a bonding film according to the following item [7].
[7] an adhesive layer;
A release film provided on one or both sides of the adhesive layer and configured to be peelable from the adhesive layer,
A bonding film, wherein the adhesive layer is composed of the adhesive composition according to any one of [1] to [6] or a semi-cured product obtained by partially curing the adhesive composition.

A third aspect of the present invention is a laminate with an adhesive layer according to the following item [8].
[8] an adhesive layer;
A substrate layer adhered to at least one surface of the adhesive layer,
A laminate with an adhesive layer, wherein the adhesive layer is composed of the adhesive composition according to any one of [1] to [6] or a semi-cured product obtained by partially curing the adhesive composition.

A fourth aspect of the present invention is a laminate according to the following item [9].
[9] A laminate comprising a cured layer made of a cured product of the adhesive composition according to any one of [1] to [6].

The adhesive composition contains the base resin (A), the epoxy compound (B), the triazine compound (C), and the metal phosphinate (D) in the specific ratio. The cured product of the adhesive composition having such a composition has good heat resistance even when it absorbs moisture.

Furthermore, both the bonding film and the laminate with the adhesive layer have an adhesive layer made of the adhesive composition or a semi-cured product thereof. Therefore, by producing a laminate using these materials, the adhesive state of each layer constituting the laminate can be maintained even when the laminate in a hygroscopic state is heated.

The laminate also has a cured layer made of the cured product of the adhesive composition. Therefore, even if the laminate is heated in a hygroscopic state, the adhesive state of each layer constituting the laminate can be maintained.

As described above, according to the above-mentioned aspect, it is possible to provide an adhesive composition capable of forming a cured product that exhibits excellent heat resistance even in a hygroscopic state, a bonding film made using this adhesive composition, a laminate with an adhesive layer, and a laminate.

FIG. 1 is a partial cross-sectional view of a test piece A for evaluating flame retardancy in the examples. FIG. 2 is a partial cross-sectional view of bonding film B in the embodiment. FIG. 3 is a partial cross-sectional view of a test piece C for evaluating adhesiveness in the examples.

(Adhesive Composition)
[Base resin (A)]
The adhesive composition contains at least one resin selected from the group consisting of polyamide resins and polyurethane resins as the base resin (A). In this specification, the polyamide resin refers to a resin containing an amide portion in which a plurality of repeating units are bonded via amide bonds. That is, the polyamide resin may be, for example, a polyamide in which one or more types of repeating units are bonded via amide bonds. In addition, the polyamide resin may be, for example, a resin containing an amide bond and a bond other than an amide bond as a bond group that bonds the repeating units. Examples of such resins include polyester polyamides containing an amide bond and an ester bond as a bond group. The polyamide resin may have a linear molecular structure or a molecular structure containing a branched chain.

In addition, in this specification, a polyurethane-based resin refers to a resin containing a polyurethane portion in which multiple repeating units are bonded via urethane bonds. That is, the polyurethane-based resin may be, for example, a polyurethane in which one or more types of repeating units are bonded via urethane bonds. The polyurethane-based resin may be, for example, a resin containing a urethane bond and a bonding group other than a urethane bond as a bonding group that bonds the repeating units together. Examples of such resins include polyester polyurethanes containing a urethane bond and an ester bond as a bonding group. The polyurethane-based resin may have a linear molecular structure or a molecular structure containing a branched chain. Furthermore, the polyurethane-based resin may have a polyphenylene ether skeleton containing multiple phenylene groups and ether bonds that bond the phenylene groups together.

From the viewpoint of more reliably improving the heat resistance of the cured product in a hygroscopic state, it is preferable that the base resin (A) contains one or more resins selected from the group consisting of polyester polyamide, polyester polyurethane, and the polyurethane-based resin having a polyphenylene ether skeleton. From the same viewpoint, it is more preferable that the base resin (A) is any one resin selected from the group consisting of polyester polyamide, polyester polyurethane, and the polyurethane-based resin having a polyphenylene ether skeleton.

The weight average molecular weight of the base resin (A) is preferably 5,000 or more and 150,000 or less. In this case, the heat resistance of the cured product in a hygroscopic state can be improved more reliably. From the same viewpoint, the number average molecular weight of the base resin (A) is preferably 1,500 or more and 100,000 or less. The number average molecular weight and weight average molecular weight of the base resin (A) are polystyrene-equivalent values obtained by gel permeation chromatography (hereinafter also referred to as "GPC") using polystyrene as the standard substance.

Specific measurement conditions for GPC are, for example, as follows.
Equipment: Tosoh Corporation "HLC-8320"
Column: Tosoh Corporation "TSKgel SuperMultiporeHZ-M" x 4 Solvent: Tetrahydrofuran Column temperature: 40°C
Detector: RI
Flow rate: 600μL/min

From the viewpoint of adhesion and heat resistance, the content of the base resin (A) in the adhesive composition is preferably 5% by mass or more and 90% by mass or less, more preferably 10% by mass or more and 80% by mass or less, even more preferably 20% by mass or more and 75% by mass or less, and particularly preferably 30% by mass or more and 70% by mass or less, based on the total solid content of the adhesive composition.

Polyamide The polyamide-based resin used in the base resin (A) may be a polyamide. The adhesive composition may contain one type of polyamide, or may contain two or more types of polyamide.

Polyamides have repeating units derived from polycarboxylic acids having two or more carboxy groups, repeating units derived from amines having two or more amino groups, and amide bonds linking these together. Polyamides may have a linear molecular structure, or may have a molecular structure including a branched chain. From the viewpoint of improving processability in heat press processing and heat lamination processing, it is preferable that polyamides have a linear molecular structure. From the same viewpoint, it is preferable that polyamides do not have aromatic rings in their molecular structure.

The polyamide preferably has a repeating unit derived from a dicarboxylic acid and a repeating unit derived from a diamine. The polyamide may also have a repeating unit having a carboxy group and a functional group other than a carboxy group, such as a hydroxycarboxylic acid or sulfocarboxylic acid.

Dicarboxylic acids used in polyamides include chain aliphatic dicarboxylic acids, alicyclic dicarboxylic acids, and aromatic dicarboxylic acids. Chain aliphatic carboxylic acids used in polyamides include, for example, succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, and dimer acid. From the viewpoint of more reliably improving the heat resistance of the cured material in a hygroscopic state, it is preferable that the polyamide contains repeating units derived from one or two chain aliphatic dicarboxylic acids selected from azelaic acid and dimer acid, and it is more preferable that the polyamide contains repeating units derived from azelaic acid.

Examples of alicyclic dicarboxylic acids used in polyamides include 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, and anhydrides of 1,2-cyclohexanedicarboxylic acid.

Aromatic dicarboxylic acids used in polyamides include, for example, aromatic dicarboxylic acids that do not have a sulfonic acid group or a sulfonate salt group, such as terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, biphenyldicarboxylic acid, and 5-hydroxyisophthalic acid; aromatic sulfodicarboxylic acids, such as sulfoterephthalic acid, 5-sulfoisophthalic acid, 4-sulfophthalic acid, 4-sulfonaphthalene-2,7-dicarboxylic acid, and 5-(4-sulfophenoxy)isophthalic acid; metal salts of aromatic sulfodicarboxylic acids; and ammonium salts of aromatic sulfodicarboxylic acids.

The polyamide preferably contains repeating units derived from one or more dicarboxylic acids selected from the group consisting of chain aliphatic dicarboxylic acids having 6 to 22 carbon atoms (excluding dimerized aliphatic diacids), aromatic dicarboxylic acids having 6 to 22 carbon atoms, alicyclic dicarboxylic acids having 6 to 22 carbon atoms (excluding dimerized aliphatic diacids), and dimerized aliphatic diacids having 20 to 48 carbon atoms. More specifically, the polyamide may contain repeating units derived from one or more dicarboxylic acids selected from the group consisting of the chain aliphatic dicarboxylic acids, aromatic dicarboxylic acids, and alicyclic dicarboxylic acids, and repeating units derived from the dimerized aliphatic diacids, or may contain repeating units derived from one or more dicarboxylic acids selected from the group consisting of the chain aliphatic dicarboxylic acids, aromatic dicarboxylic acids, and alicyclic dicarboxylic acids, or may contain repeating units derived from the dimerized aliphatic diacids.

From the viewpoint of further improving the heat resistance of the cured product in a hygroscopic state, it is more preferable that the polyamide contains repeating units derived from one or more dicarboxylic acids selected from the group consisting of the chain aliphatic dicarboxylic acid, the alicyclic dicarboxylic acid, and the dimerized aliphatic diacid, and it is even more preferable that the polyamide contains repeating units derived from azelaic acid. Furthermore, the number of carbon atoms of the chain aliphatic dicarboxylic acid, aromatic dicarboxylic acid, and alicyclic dicarboxylic acid contained in the polyamide is preferably 6 to 12, and more preferably 8 to 10. The number of carbon atoms of the dimerized aliphatic diacid contained in the polyamide portion is preferably 30 to 48, and more preferably 32 to 40.

Polyamines used in polyamides include diamines and aminocarboxylic acids. Diamines used in polyamides include diaminocyclohexane, piperidine, isophoronediamine, 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, o-(or m-, p-)phenylenediamine, o-(or m-, p-)xylenediamine, 3,3'-(or 3,4'-)diaminodiphenylene ether, 4,4'-diaminodiphenyl ether, 3,3'-(or 3,4'-)diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,3'-(or 3,4'-, 4,4'-)diaminodiphenyl difluoromethane, 3,3'-(or 3,4'-, 4,4'-)diaminodiphenyl sulfone, 3,3'-(or 3,4'-, 4,4'-)diaminodiphenyl sulfide, 3,3'-(or 3,4'-, 4,4'-)diaminodiphenyl ketone, 2,2-bis (3-aminophenyl)propane, 2,2'-(3,4'-diaminodiphenyl)propane, 2,2-bis(4-aminophenyl)propane, 2,2-bis(3-aminophenyl)hexafluoropropane, 2,2-(3,4'-diaminodiphenyl)hexafluoropropane, 2,2-bis(4-aminophenyl)hexafluoropropane, 1,3-(or 1,4-)bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 3,3'-( Examples include 1-phenylenebis(1-methylethylidene))bisaniline, 3,4'-(1,4-phenylenebis(1-methylethylidene))bisaniline, 4,4'-(1,4-phenylenebis(1-methylethylidene))bisaniline, 2,2-bis(4-(3-aminophenoxy)phenyl)propane, 2,2-bis(4-(4-aminophenoxy)phenyl)propane, and 2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane.

From the viewpoint of further improving the heat resistance of the cured product in a hygroscopic state, the polyamide preferably contains one or more repeating units selected from the group consisting of aromatic diamines having 6 to 44 carbon atoms and diamines having an alicyclic skeleton having 6 to 44 carbon atoms, more preferably contains repeating units derived from diamines having an alicyclic skeleton having 6 to 44 carbon atoms, and particularly preferably contains isophoronediamine. The carbon number of the diamine is preferably 8 to 30, more preferably 10 to 24.

From the same viewpoint, the polyamide preferably contains repeating units derived from one or more dicarboxylic acids selected from the group consisting of chain aliphatic dicarboxylic acids having 6 to 22 carbon atoms (excluding dimerized aliphatic diacids), aromatic dicarboxylic acids having 6 to 22 carbon atoms, alicyclic dicarboxylic acids having 6 to 22 carbon atoms (excluding dimerized aliphatic diacids), and dimerized aliphatic diacids having 20 to 48 carbon atoms, and repeating units derived from one or more diamines selected from the group consisting of aromatic diamines having 6 to 44 carbon atoms and diamines having an alicyclic skeleton having 6 to 44 carbon atoms, and more preferably contains repeating units derived from one or more dicarboxylic acids selected from the group consisting of the chain aliphatic dicarboxylic acids, the alicyclic dicarboxylic acids, and the dimerized aliphatic diacids, and repeating units derived from the diamines having an alicyclic skeleton.

The polyamide may also have a repeating unit derived from a polycarboxylic acid having three or more carboxy groups. In this case, a branched chain can be introduced into the polyamide. Also, by introducing a branched chain into the polyamide, the end group concentration (i.e., the reaction points) of the resin can be increased. Therefore, for example, by reacting a polyamide into which a branched chain has been introduced with a curing agent, a cured layer with a high crosslink density can be obtained.

The content of repeating units derived from polycarboxylic acids having three or more carboxy groups is preferably 0.1 mol% or more and 5 mol% or less, and more preferably 0.1 mol% or more and 3 mol% or less, relative to all repeating units in the polyamide.

Examples of polycarboxylic acids having three or more carboxy groups include trimellitic acid, trimesic acid, ethylene glycol bis(anhydrotrimellitate), glycerol tris(anhydrotrimellitate), trimellitic anhydride, pyromellitic anhydride (PMDA), oxydiphthalic dianhydride (ODPA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride (BTDA), 3,3',4,4'-diphenyl tetracarboxylic dianhydride (BPDA), 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride (DSDA), 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), and 2,2'-bis[(dicarboxyphenoxy)phenyl]propane dianhydride (BSAA).

The method for producing polyamide is not particularly limited, and known methods can be used. For example, the polycarboxylic acid, polyamine, and other compounds used as necessary may all be placed in a reaction vessel and then reacted, or raw materials such as polycarboxylic acid may be placed in the reaction vessel in stages as the reaction progresses.

The polycondensation reaction of polycarboxylic acid and polyamine may be carried out in the presence of a solvent or without the use of a solvent. Examples of the solvent include ester-based solvents such as ethyl acetate, butyl acetate, and ethyl butyrate; ether-based solvents such as dioxane, tetrahydrofuran, and diethyl ether; ketone-based solvents such as cyclohexanone, methyl ethyl ketone, and methyl isobutyl ketone; aromatic hydrocarbon-based solvents such as benzene, toluene, and xylene, and mixtures of these solvents. From the viewpoint of reducing the environmental load, it is preferable to use ethyl acetate or methyl ethyl ketone as the solvent. The reaction apparatus in which the polycondensation reaction is carried out may be a reaction vessel equipped with a stirrer, or a mixing and kneading apparatus such as a kneader or a twin-screw extruder.

When producing polyamide, a catalyst used to promote amidation reactions, such as tetrabutoxytitanate, can be used as needed to promote the amidation reaction. In addition, when producing polyamide, a condensing agent, etc. can be used as needed.

Polyester polyamide The polyamide resin used in the base resin (A) may be a polyester polyamide. The adhesive composition may contain one type of polyester polyamide, or may contain two or more types of polyester polyamide.

　Polyester polyamide has a polyester portion in which multiple repeating units are bonded via ester bonds, and an amide portion in which multiple repeating units are bonded via amide bonds. The polyester portion may have two or more ester bonds. The polyamide portion may have two or more amide bonds. The polyester portion and the polyamide portion may be bonded via ester bonds or amide bonds.

The polyester polyamide is preferably a resin having a polyester chain and two or more amide bonds, a resin having a polyamide chain and two or more ester bonds, or a resin having a polyester chain and a polyamide chain. The weight average molecular weight of the polyester chain may be 1,000 or more. The weight average molecular weight of the polyamide chain may be 1,000 or more. The upper limit of the weight average molecular weight of each of the polyester chain and the polyamide chain is not particularly limited, but may be, for example, 150,000 or less.

The polyester polyamide may have a linear molecular structure, or may have a molecular structure including a branched chain. From the viewpoint of improving processability in heat press processing and heat lamination processing, it is preferable that the polyester polyamide has a linear molecular structure. From the same viewpoint, it is preferable that the polyester polyamide does not have an aromatic ring in its molecular structure.

The polyester polyamide has, for example, a repeating unit derived from a polycarboxylic acid, a repeating unit derived from a polyol, and a repeating unit derived from a polyamine. It is preferable that the polyester polyamide has a repeating unit derived from a dicarboxylic acid, a repeating unit derived from a diol, and a repeating unit derived from a diamine.

More specifically, the polyester portion of the polyester polyamide has a repeating unit derived from a polycarboxylic acid and a repeating unit derived from a polyol. Examples of polycarboxylic acids used in the polyester portion include dicarboxylic acids similar to those used in the polyamides described above, polycarboxylic acids having three or more carboxy groups, hydroxycarboxylic acids, and sulfocarboxylic acids. From the viewpoint of further improving the heat resistance of the cured product in a hygroscopic state, the polyester portion of the polyester polyamide preferably contains a repeating unit derived from one or more dicarboxylic acids selected from the group consisting of chain aliphatic dicarboxylic acids having 6 to 22 carbon atoms, aromatic dicarboxylic acids having 6 to 22 carbon atoms, and alicyclic dicarboxylic acids having 6 to 22 carbon atoms, and more preferably contains a repeating unit derived from a chain aliphatic dicarboxylic acid having 6 to 22 carbon atoms and an alicyclic dicarboxylic acid having 6 to 22 carbon atoms.

The polyol used in the polyester portion may be a diol or a polyol having three or more hydroxyl groups. Examples of diols include chain aliphatic diols, alicyclic diols, aromatic diols, and ether bond-containing diols. From the viewpoint of solder heat resistance and adhesion, the polyester polyamide preferably contains repeating units derived from one or more diols selected from the group consisting of chain aliphatic diols having 2 to 54 carbon atoms, aromatic diols having 2 to 54 carbon atoms, and alicyclic diols having 2 to 54 carbon atoms, and more preferably contains any one of repeating units derived from a chain aliphatic diol having 2 to 54 carbon atoms, repeating units derived from an aromatic diol having 2 to 54 carbon atoms, or repeating units derived from an alicyclic diol having 2 to 54 carbon atoms.

Examples of chain aliphatic diols include ethylene glycol, 1,2-propylene diol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, 2-butyl-2-ethyl-1,3-propanediol, hydroxypivalic acid neopentyl glycol ester, dimethylol heptane, and 2,2,4-trimethyl-1,3-pentanediol.

Examples of alicyclic diols include 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, tricyclodecanediol, tricyclodecanedimethylol, spiroglycol, hydrogenated bisphenol A, ethylene oxide adduct of hydrogenated bisphenol A, and propylene oxide adduct of hydrogenated bisphenol A.

Aromatic diols include, for example, benzenedimethanols such as 1,2-benzenedimethanol, 1,3-benzenedimethanol, and 1,4-benzenedimethanol; 2-(4-hydroxyphenyl)ethanol; bisphenols such as bisphenol A; ethylene oxide adducts of bisphenols; and propylene oxide adducts of bisphenols.

Examples of ether bond-containing diols include diethylene glycol, triethylene glycol, dipropylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, neopentyl glycol ethylene oxide adduct, and neopentyl glycol propylene oxide adduct.

From the viewpoint of compatibility with the epoxy compound (B) and the like and solution stability, it is preferable that the polyester portion contains a repeating unit derived from a diol having a side chain. The side chain of the diol is preferably an alkyl group, more preferably an alkyl group having 1 to 5 carbon atoms. Examples of diols having a side chain include neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, and 2,2-dimethylolpropionic acid.

From the viewpoint of solder heat resistance and adhesiveness, the polyester portion of the polyester polyamide preferably contains repeating units derived from one or more diols selected from the group consisting of chain aliphatic diols having 2 to 54 carbon atoms, aromatic diols having 2 to 54 carbon atoms, and alicyclic diols having 2 to 54 carbon atoms, and more preferably contains any one of repeating units derived from chain aliphatic diols having 2 to 54 carbon atoms, repeating units derived from aromatic diols having 2 to 54 carbon atoms, or repeating units derived from alicyclic diols having 2 to 54 carbon atoms.

The polyester portion of the polyester polyamide may have a repeating unit derived from a polycarboxylic acid having three or more carboxy groups and/or a repeating unit derived from a polyol having three or more hydroxy groups. In this case, a branched chain can be introduced into the polyester portion. Also, by introducing a branched chain into the polyester portion, the end group concentration of the resin (i.e., the reaction points) can be increased. Therefore, for example, by reacting a polyester polyamide into which a branched chain has been introduced with a curing agent, a cured layer with a high crosslink density can be obtained.

Examples of polycarboxylic acids having three or more carboxy groups include the polycarboxylic acids having three or more carboxy groups used in the polyamides described above.

Examples of polyols having three or more hydroxyl groups include glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol.

The sum of the content of repeating units derived from polycarboxylic acids having three or more carboxy groups and the content of repeating units derived from polyols having three or more hydroxyl groups is preferably 0.1 mol% or more and 5 mol% or less, and more preferably 0.1 mol% or more and 3 mol% or less, relative to all repeating units in the polyester portion.

More specifically, the polyamide portion in the polyester polyamide has a repeating unit derived from a polycarboxylic acid and a repeating unit derived from a polyamine. It is preferable that the polyamide portion in the polyester polyamide has a repeating unit derived from a dicarboxylic acid and a repeating unit derived from a diamine. The polyamide portion may also have a repeating unit having a carboxy group and a functional group other than a carboxy group, such as a hydroxycarboxylic acid or sulfocarboxylic acid.

Examples of polycarboxylic acids used in the polyamide portion include dicarboxylic acids similar to those used in the polyamides described above, polycarboxylic acids having three or more carboxy groups, hydroxycarboxylic acids, and sulfocarboxylic acids. From the viewpoint of further improving the solder heat resistance and adhesion, it is preferable that the polyamide portion contains repeating units derived from one or more dicarboxylic acids selected from the group consisting of chain aliphatic dicarboxylic acids having 6 to 22 carbon atoms (excluding dimerized aliphatic diacids), aromatic dicarboxylic acids having 6 to 22 carbon atoms, alicyclic dicarboxylic acids having 6 to 22 carbon atoms (excluding dimerized aliphatic diacids), and dimerized aliphatic diacids having 20 to 48 carbon atoms. More specifically, the polyamide portion may contain repeating units derived from one or more dicarboxylic acids selected from the group consisting of the chain aliphatic dicarboxylic acid, the aromatic dicarboxylic acid, and the alicyclic dicarboxylic acid, and repeating units derived from the dimerized aliphatic diacid, may contain repeating units derived from one or more dicarboxylic acids selected from the group consisting of the chain aliphatic dicarboxylic acid, the aromatic dicarboxylic acid, and the alicyclic dicarboxylic acid, and may contain repeating units derived from the dimerized aliphatic diacid.

From the viewpoint of further improving the solder heat resistance and adhesion, it is more preferable that the polyamide portion contains repeating units derived from one or more dicarboxylic acids selected from the group consisting of the chain aliphatic dicarboxylic acid, the alicyclic dicarboxylic acid, and the dimerized aliphatic diacid, and it is even more preferable that the polyamide portion contains repeating units derived from azelaic acid. Furthermore, the number of carbon atoms of the chain aliphatic dicarboxylic acid, aromatic dicarboxylic acid, and alicyclic dicarboxylic acid contained in the polyamide portion is preferably 6 to 12, and more preferably 8 to 10. The number of carbon atoms of the dimerized aliphatic diacid contained in the polyamide portion is preferably 30 to 48, and more preferably 32 to 40.

Polyamines used in the polyamide portion of polyester polyamides include diamines and aminocarboxylic acids similar to the polyamines used in the polyamides described above.

From the viewpoint of further improving the heat resistance of the cured product in a hygroscopic state, the polyamide portion preferably contains one or more repeating units selected from the group consisting of aromatic diamines having 6 to 44 carbon atoms and diamines having an alicyclic skeleton having 6 to 44 carbon atoms, more preferably contains repeating units derived from diamines having an alicyclic skeleton having 6 to 44 carbon atoms, and particularly preferably contains isophoronediamine. The carbon number of the diamine is preferably 8 to 30, more preferably 10 to 24.

From the same viewpoint, the polyamide portion in the polyester polyamide preferably contains repeating units derived from one or more dicarboxylic acids selected from the group consisting of chain aliphatic dicarboxylic acids having 6 to 22 carbon atoms (excluding dimerized aliphatic diacids), aromatic dicarboxylic acids having 6 to 22 carbon atoms, alicyclic dicarboxylic acids having 6 to 22 carbon atoms (excluding dimerized aliphatic diacids), and dimerized aliphatic diacids having 20 to 48 carbon atoms, and repeating units derived from one or more diamines selected from the group consisting of aromatic diamines having 6 to 44 carbon atoms and diamines having an alicyclic skeleton having 6 to 44 carbon atoms, and more preferably contains repeating units derived from one or more dicarboxylic acids selected from the group consisting of the chain aliphatic dicarboxylic acids, the alicyclic dicarboxylic acids, and the dimerized aliphatic diacids, and the diamines having an alicyclic skeleton.

The polyester polyamide further comprises a polyester portion including a repeating unit derived from one or more dicarboxylic acids selected from the group consisting of a chain aliphatic dicarboxylic acid having from 6 to 22 carbon atoms, an aromatic dicarboxylic acid having from 6 to 22 carbon atoms, and an alicyclic dicarboxylic acid having from 6 to 22 carbon atoms, and a polyester portion including a repeating unit derived from one or more diols selected from the group consisting of a chain aliphatic diol having from 2 to 54 carbon atoms, an aromatic diol having from 2 to 54 carbon atoms, and an alicyclic diol having from 2 to 54 carbon atoms;
It is preferable that the polyester polyamide has a polyamide portion containing a repeating unit derived from one or more dicarboxylic acids selected from the group consisting of chain aliphatic dicarboxylic acids having 6 to 22 carbon atoms (excluding dimerized aliphatic diacids), aromatic dicarboxylic acids having 6 to 22 carbon atoms, alicyclic dicarboxylic acids having 6 to 22 carbon atoms (excluding dimerized aliphatic diacids), and dimerized aliphatic diacids having 20 to 48 carbon atoms, and a polyamide portion containing a repeating unit derived from one or more diamines selected from the group consisting of aromatic diamines having 6 to 44 carbon atoms and diamines having an alicyclic skeleton having 6 to 44 carbon atoms. With such a polyester polyamide having a polyester portion and a polyamide portion, an adhesive composition having low water absorption and excellent long-term moist heat resistance can be easily obtained.

From the viewpoint of adhesion and heat resistance, the glass transition temperature of the polyester portion in the polyester polyamide is preferably 40°C or higher and 150°C or lower, more preferably 45°C or higher and 120°C or lower, even more preferably 50°C or higher and 90°C or lower, and particularly preferably 60°C or higher and 70°C or lower.

In addition, from the viewpoint of adhesion and heat resistance, the glass transition temperature of the polyester polyamide is preferably 30°C or higher and 150°C or lower, more preferably 40°C or higher and 140°C or lower, even more preferably 50°C or higher and 90°C or lower, and particularly preferably 60°C or higher and 70°C or lower.

From the viewpoint of heat resistance, the weight average molecular weight of the polyester polyamide is preferably 5,000 or more and 150,000 or less, more preferably 10,000 or more and 100,000 or less, even more preferably 30,000 or more and 80,000 or less, and particularly preferably 40,000 or more and 60,000 or less. From the same viewpoint, the number average molecular weight of the polyester polyamide is preferably 1,500 or more and 50,000 or less, more preferably 10,000 or more and 25,000 or less, and even more preferably 13,000 or more and 20,000 or less.

From the viewpoint of adhesion, the amine value of the polyester polyamide is preferably 1.0 mgKOH/g or more and 12.0 mgKOH/g or less, more preferably 3.0 mgKOH/g or more and 11.0 mgKOH/g or less, even more preferably 6.0 mgKOH/g or more and 10.0 mgKOH/g or less, and particularly preferably 7.0 mgKOH/g or more and 8.0 mgKOH/g or less. The amine value of the resin in this specification is a value measured and calculated by potentiometric measurement in accordance with JIS K 7237 (1995).

The method for producing polyester polyamide is not particularly limited, and known methods can be used. For example, the polycarboxylic acid, polyol, polyamine, and other compounds used as necessary may all be placed in a reaction vessel and then reacted, or raw materials such as polycarboxylic acid may be placed in the reaction vessel in stages as the reaction progresses. In the polycondensation of polyester polyamide, the amounts of polycarboxylic acid, polyol, and polyamine added may be set so that the ratio of the total amount of carboxyl groups to the sum of the total amount of hydroxyl groups and the total amount of amino groups is preferably 0.9 to 1.1, more preferably 0.98 to 1.02, and particularly preferably 1.

The polycondensation reaction may be carried out in the presence of a solvent or without the use of a solvent. As the solvent, the same solvent as that used in the polycondensation reaction of polyamide described above can be used. From the viewpoint of reducing the environmental load, it is preferable to use ethyl acetate or methyl ethyl ketone as the solvent. As the reaction apparatus in which the polycondensation reaction is carried out, a reaction vessel equipped with a stirring device, a kneader, a mixing and kneading device such as a twin-screw extruder, etc. can be used.

When producing polyester polyamide, a catalyst used to promote esterification and/or amidation reactions, such as tetrabutoxytitanate, can be used as needed to promote the esterification reaction or amidation reaction. In addition, when producing polyester polyamide, a condensation agent, a chain extender, etc. can also be used as needed.

When producing polyester polyamide, a chain extender may be used as necessary. Examples of chain extenders that can be used include the above-mentioned diols, compounds having one carboxy group and two hydroxy groups such as dimethylolpropionic acid and dimethylolbutanoic acid, and polyamines.

The chain extender is preferably a diol, more preferably a diol having a side chain, and even more preferably a diol having a branched chain. More specifically, the chain extender is preferably at least one compound selected from the group consisting of neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, and 2,2-dimethylolpropionic acid, and particularly preferably contains at least one compound selected from the group consisting of neopentyl glycol and 2-butyl-2-ethyl-1,3-propanediol, and 2,2-dimethylolpropionic acid.

When producing polyester polyamide, acid addition may be carried out as necessary for the purpose of introducing carboxy groups into the polyester polyamide. The amount of carboxy groups introduced by acid addition may be, for example, within the range of 0.1 mol % to 10 mol % relative to the total of the repeating units derived from carboxylic acid and the repeating units derived from alcohol contained in the polyester polyamide. If a monocarboxylic acid, dicarboxylic acid or polyfunctional carboxylic acid compound is used when acid addition is carried out on polyester polyamide, there is a risk of a decrease in molecular weight due to ester exchange. Therefore, when acid addition is carried out on polyester polyamide, it is preferable to use an acid anhydride.

Examples of acid anhydrides include succinic anhydride, maleic anhydride, orthophthalic acid, 2,5-norbornene dicarboxylic anhydride, tetrahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride (PMDA), oxydiphthalic dianhydride (ODPA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), 3,3',4,4'-diphenyltetracarboxylic dianhydride (BPDA), 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA), 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), and 2,2'-bis[(dicarboxyphenoxy)phenyl]propane dianhydride (BSAA).

The method of acid addition is not particularly limited, and examples include a method in which acid addition is performed in bulk after the polycondensation of polyester polyamide is completed, and a method in which acid addition is performed after the polyester polyamide is put into solution. When acid addition is performed in bulk, there is an advantage that the reaction rate is fast. On the other hand, when acid addition is performed in bulk, gelation is more likely to occur if a large amount of acid is added. In addition, when acid addition is performed in bulk, the reaction temperature becomes high, and the polyester polyamide is easily oxidized. Therefore, when acid addition is performed in bulk, care must be taken to prevent oxidation by blocking oxygen gas. When acid addition is performed in solution, the reaction is slow, but a large number of carboxy groups can be stably introduced into the polyester polyamide.

Polyurethane The polyurethane-based resin used in the base resin (A) may be a polyurethane. The adhesive composition may contain one type of polyurethane, or may contain two or more types of polyurethane.

Polyurethane has repeating units derived from a polyol having two or more hydroxyl groups, repeating units derived from a polyisocyanate having two or more isocyanate groups, and urethane bonds connecting these. Polyurethane may have two or more urethane bonds. Polyurethane may have repeating units derived from a diol and repeating units derived from a diisocyanate.

Polyurethane may contain repeating units derived from one type of polyisocyanate, or may contain repeating units derived from two or more types of polyisocyanates. It is preferable that polyurethane contains repeating units derived from diisocyanates. Furthermore, polyurethane may contain repeating units derived from polyisocyanates having three or more isocyanates, in addition to repeating units derived from diisocyanates.

Examples of diisocyanates include aromatic diisocyanates, aralkyl diisocyanates, chain aliphatic diisocyanates, alicyclic diisocyanates, and derivatives of these diisocyanates. From the viewpoint of suppressing yellowing of polyurethane, it is preferable that the polyurethane contains repeating units derived from one or more diisocyanates selected from the group consisting of chain aliphatic diisocyanates and alicyclic diisocyanates, and it is more preferable that the polyurethane contains repeating units derived from alicyclic diisocyanates.

Examples of aromatic diisocyanates include 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 2,2'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 4,4'-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, 2,6-naphthalene diisocyanate, 3,3'-dimethoxy-4,4'-biphenylene diisocyanate, and diphenyl ether-4,4'-diisocyanate.

Examples of aralkyl diisocyanates include m-xylylene diisocyanate, p-xylylene diisocyanate, and tetramethyl-m-xylylene diisocyanate.

Examples of chain aliphatic diisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 1,3-butylene diisocyanate, 2,3-butylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate.

Examples of alicyclic diisocyanates include 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, 1-methylcyclohexane-2,4-diisocyanate, 1-methylcyclohexane-2,6-diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, 1,3-bis(isocyanatomethyl)cyclohexane, triethyl)cyclohexane, 1,4-bis(isocyanatoethyl)cyclohexane, 4,4'-methylenebis(cyclohexylisocyanate), norbornane-2,5-diyldiisocyanate, norbornane-2,6-diyldiisocyanate, norbornane-2,5-diylbis(methylene)diisocyanate, norbornane-2,6-diylbis(methylene)diisocyanate, isophorone diisocyanate, etc.

Examples of diisocyanate derivatives include isocyanates having a uretdione group obtained by cyclizing and dimerizing two isocyanate groups; isocyanates having an isocyanurate group or an iminooxadiazinedione group obtained by cyclizing and trimerizing three isocyanate groups; and isocyanates having a biuret group obtained by reacting three isocyanate groups with one molecule of water.

Polyurethane may contain repeating units derived from one type of polyol, or may contain repeating units derived from two or more types of polyols. Examples of polyols used in polyurethanes include the diols used in the polyester polyamides described above and polyols having three or more hydroxy groups. The polyols used in polyurethanes may also be diols having a functional group other than a hydroxy group. Examples of such diols include diols having one carboxy group, such as 2,2-bis(hydroxymethyl)propionic acid and 2,2-bis(hydroxymethyl)butanoic acid, and diols having one amino group, such as 2-amino-1,3-propanediol. By using these diols, polyurethanes having functional groups other than hydroxy groups in the side chains can be obtained.

The polyol used in the polyurethane may be a polymer having two or more hydroxy groups, such as a polycarbonate polyol, a polyolefin polyol, or a polyether polyol.

Examples of polycarbonate polyols used in polyurethanes include polycarbonate polyols obtained by a dealcoholization reaction or a dephenolization reaction between a carbonate compound and a polyol.

Examples of carbonate compounds used in polycarbonate polyols include alkylene carbonates, dialkyl carbonates, and diaryl carbonates. Examples of alkylene carbonates include ethylene carbonate, trimethylene carbonate, 1,2-propylene carbonate, 1,2-butylene carbonate, 1,3-butylene carbonate, and 1,2-pentylene carbonate. Examples of dialkyl carbonates include dimethyl carbonate, diethyl carbonate, and dipropyl carbonate. Examples of diaryl carbonates include diphenyl carbonate. Polycarbonate polyols may contain repeating units derived from one of these carbonate compounds, or may contain repeating units derived from two or more carbonate compounds.

Polyols used in polycarbonate polyols include, for example, ethylene glycol, 1,3-propanediol, propylene glycol, 1,3-butylene glycol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,4-cyclohexanedimethanol, 3,3'-dimethylolheptane, diethylene glycol, 1,4-bis(hydroxymethyl)cyclohexane, Examples of such polyols include diols such as 1,4-bis(hydroxyethyl)benzene and 2,2-bis(4,4'-hydroxycyclohexyl)propane; triols such as glycerin, trimethylolethane, trimethylolpropane, and 1,2,6-hexanetriol; and polyols having four or more hydroxy groups such as pentaerythritol, diglycerin, α-methylglucoside, sorbitol, xylitol, mannitol, dipentaerythritol, glucose, fructose, and sucrose. The polycarbonate polyol may contain repeating units derived from one of these polyols, or may contain repeating units derived from two or more polyols.

The number average molecular weight of the polycarbonate polyol is preferably 600 or more, more preferably 600 to 30,000, even more preferably 800 to 10,000, and particularly preferably 1,000 to 5,000.

Examples of polyolefin polyols used in polyurethanes include polybutadiene polyols (e.g., diols in which hydroxy groups have been introduced to both molecular ends of polybutadiene), hydrogenated polybutadiene polyols (e.g., diols in which hydroxy groups have been introduced to both molecular ends of hydrogenated polybutadiene), polyisoprene polyols (e.g., diols in which hydroxy groups have been introduced to both molecular ends of polyisoprene), and hydrogenated polyisoprene polyols (e.g., diols in which hydroxy groups have been introduced to both molecular ends of hydrogenated polyisoprene).

The number average molecular weight of the polyolefin polyol is preferably 600 or more, more preferably 600 to 30,000, even more preferably 800 to 10,000, and particularly preferably 1,000 to 5,000.

Examples of polyether polyols include aliphatic polyether diols and polyphenylene ether polyols.

Examples of aliphatic polyether diols include polyalkylene ether glycols such as polyethylene glycol, polypropylene glycol, polybutylene glycol, and polytetramethylene ether glycol. The number average molecular weight of the aliphatic polyether diol is preferably 600 or more, more preferably 600 to 30,000, even more preferably 800 to 10,000, and particularly preferably 1,000 to 5,000.

In this specification, polyphenylene ether polyol refers to a compound having a polyphenylene ether skeleton consisting of multiple phenylene groups and ether bonds bonding these phenylene groups together, and two or more hydroxy groups bonded to the phenylene groups in the polyphenylene ether. The hydroxy groups in the polyphenylene ether polyol may be bonded to the phenylene groups at the ends of the polyphenylene ether skeleton, or to phenylene groups other than those at the ends. By using such polyphenylene ether polyol, a polyphenylene ether skeleton containing multiple phenylene groups and ether bonds bonding the phenylene groups together can be introduced into polyurethane.

As the polyphenylene ether polyol, a polyphenylene ether diol having two hydroxy groups bonded to a polyphenylene ether skeleton, a polyphenylene ether triol having three hydroxy groups bonded, a polyphenylene ether polyol having four or more hydroxy groups bonded, etc. can be used. Among these, the polyphenylene ether polyol is preferably a polyphenylene ether diol having two hydroxy groups bonded to a polyphenylene ether skeleton.

The polyphenylene ether skeleton contains one or more phenylene groups selected from the group consisting of unsubstituted o-phenylene groups (1,2-phenylene groups), substituted o-phenylene groups, unsubstituted m-phenylene groups (1,3-phenylene groups), substituted m-phenylene groups, unsubstituted p-phenylene groups (1,4-phenylene groups), and substituted p-phenylene groups. The phenylene groups in the polyphenylene ether skeleton are preferably unsubstituted or substituted p-phenylene groups.

The substituent of the phenylene group may be, for example, a linear or branched alkyl group having 1 to 4 carbon atoms. The substituent of the phenylene group is preferably a methyl group or an ethyl group, and more preferably a methyl group.

The phenylene groups in the polyphenylene ether polyol may all have the same structure, or the structure of some of the phenylene groups may be different from the structure of the other phenylene groups.

There is no restriction on the molecular weight of the polyphenylene ether polyol. For example, the number average molecular weight of the polyphenylene ether polyol is preferably 500 or more and 10,000 or less, more preferably 700 or more and 8,000 or less, and even more preferably 1,000 or more and 6,000 or less.

The polyphenylene ether polyol may have, for example, a phenylene oxide in which the phenylene is substituted with two alkyl groups as a constituent unit. In this case, the alkyl groups in the molecule may all have the same structure, or the structure of some of the alkyl groups may be different from the structure of the other alkyl groups. The alkyl groups are preferably linear or branched alkyl groups having 1 to 4 carbon atoms.

More specifically, the polyphenylene ether polyol may have, for example, 2,6-dialkyl-1,4-phenylene oxide as a constituent unit. The polyphenylene ether polyol may also have, for example, phenylene oxide in which the phenylene is substituted with two methyl groups (i.e., dimethylphenylene oxide) as a constituent unit. The polyphenylene ether polyol may also have, for example, 2,6-dimethyl-1,4-phenylene oxide as a constituent unit.

The polyphenylene ether polyol may be, for example, a compound represented by the following general formula (A1):

In the general formula (A1), L represents a single bond or a divalent linking group, ^R4 represents a hydrogen atom or an alkyl group, and m and n each independently represent an integer of 1 or more. In the general formula (A1), ^R4 may be all the same, or some of ^R4 may be different from other ^R4 .

In the general formula (A1), examples of the divalent linking group represented by L include an oxygen atom and -C(R ⁵ )(R ⁶ )-. Here, R ⁵ and R ⁶ each independently represent a hydrogen atom, a linear or branched alkyl group having 1 to 6 carbon atoms, or a phenyl group. The hydrogen atom of the alkyl group and the phenyl group may be substituted with a halogen atom (e.g., a fluorine atom). R ⁵ and R ⁶ may be linked to each other to form a ring.

Specific examples of --C(R ⁵ )(R ⁶ )-- are listed below, but --C(R ⁵ )(R ⁶ )-- is not limited to these. In the following structural formulas, "*" indicates the linking position to the phenylene group.

^R4 in the general formula (A1) is preferably a hydrogen atom or a linear or branched alkyl group having 1 to 4 carbon atoms, more preferably a hydrogen atom, a methyl group, or an ethyl group, and even more preferably a hydrogen atom or a methyl group. The sum of m and n in the general formula (A1) is preferably a number corresponding to the number average molecular weight described above.

The polyphenylene ether polyol may be a compound represented by the following general formula (A2): Specific embodiments of R ⁴ , L, m, and n in the following general formula (A2) are the same as those of R ⁴ , L, m, and n in the general formula (A1).

^R4 in the general formula (A2) is preferably a linear or branched alkyl group having 1 to 4 carbon atoms, more preferably a methyl group or an ethyl group, and even more preferably a methyl group. The sum of m and n in the general formula (A2) is preferably a number corresponding to the number average molecular weight described above.

The polyphenylene ether polyol may be a compound represented by the following general formula (A3):

In the general formula (A3), p and q each independently represent an integer of 1 or more. The sum of p and q in the general formula (A3) is preferably a number corresponding to the number average molecular weight described above. An example of the compound represented by the general formula (A3) is "Noryl (registered trademark) SA90" manufactured by SABIC.

The content of repeating units derived from the polyphenylene ether polyol in a polyurethane having a polyphenylene ether skeleton is preferably 30% by mass or more, more preferably 50% by mass or more, and even more preferably 70% by mass or more, based on all repeating units contained in the polyurethane. In this case, the glass transition temperature of the polyurethane can be increased, the heat resistance can be further improved, and the water absorption rate of the polyurethane can be further reduced.

On the other hand, from the viewpoint of increasing the flexibility of the polyurethane, the content of repeating units derived from the polyphenylene ether polyol in the polyurethane having a polyphenylene ether skeleton is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less, based on all repeating units contained in the polyurethane.

When determining the preferred range of the content of the repeating units derived from the polyphenylene ether polyol, the upper and lower limits of the content of the repeating units derived from the polyphenylene ether polyol described above can be combined in any manner. For example, the preferred range of the content of the repeating units derived from the polyphenylene ether polyol may be 30% by mass or more and 95% by mass or less, 50% by mass or more and 90% by mass or less, or 70% by mass or more and 80% by mass or less.

In addition, when the polyurethane has a polyphenylene ether skeleton, it is preferable that the polyurethane further contains a repeating unit derived from a polymer polyol other than polyphenylene ether polyol. The content of the repeating unit derived from the polymer polyol is preferably 1 part by mass or more and 120 parts by mass or less, more preferably 10 parts by mass or more and 100 parts by mass or less, and even more preferably 20 parts by mass or more and 80 parts by mass or less, per 100 parts by mass of the repeating unit derived from polyphenylene ether polyol.

In addition, when the polyurethane has a polyphenylene ether skeleton, it is preferable that the polyurethane further contains a repeating unit derived from a diol having a functional group other than a hydroxy group. The content of the repeating unit derived from a diol having a functional group other than a hydroxy group is preferably 0.1 parts by mass or more and 30 parts by mass or less, more preferably 0.5 parts by mass or more and 20 parts by mass or less, and even more preferably 1 part by mass or more and 5 parts by mass or less, per 100 parts by mass of the repeating unit derived from the polyphenylene ether polyol.

More specifically, the polyurethane may contain, for example, a repeating unit derived from a polyphenylene ether polyol and a repeating unit derived from a diol having a carboxy group. In this case, the content of the diol having a carboxy group is preferably 0.1 parts by mass or more and 20 parts by mass or less, more preferably 0.5 parts by mass or more and 10 parts by mass or less, and even more preferably 1 part by mass or more and 5 parts by mass or less, per 100 parts by mass of the repeating units derived from the polyphenylene ether polyol.

The polyurethane may also contain, for example, repeating units derived from polyphenylene ether polyol and repeating units derived from diol having an amino group. In this case, the content of the repeating units derived from diol having an amino group is preferably 0.1 parts by mass or more and 20 parts by mass or less, more preferably 0.5 parts by mass or more and 10 parts by mass or less, and even more preferably 1 part by mass or more and 5 parts by mass or less, per 100 parts by mass of repeating units derived from polyphenylene ether polyol.

Polyurethane may contain a structural unit derived from a chain extender as necessary. By using a chain extender, for example, it is possible to impart properties to the polyurethane according to the application of the polyurethane, or to introduce a side chain into the polyurethane. As the chain extender, for example, one or more compounds selected from known compounds used as chain extenders for polyurethanes can be used. In addition, the chain extender may be a monomer or a polymer.

The chain extender used in polyurethane is preferably a compound having no functional groups other than hydroxyl groups, more preferably a polyol having no functional groups other than hydroxyl groups, and even more preferably a diol having no functional groups other than hydroxyl groups.

When the compound, polyol, or diol used as a chain extender that has no functional groups other than hydroxyl groups is a polymer, its number average molecular weight is preferably 500 or less, more preferably 400 or less, even more preferably 300 or less, and particularly preferably 50 or less.

Furthermore, when the compound, polyol, and diol that does not have any functional groups other than hydroxyl groups used as a chain extender are monomers, their molecular weight is preferably 500 or less, more preferably 400 or less, even more preferably 300 or less, and particularly preferably 50 or less.

Examples of chain extenders include diols such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,4-cyclohexanedimethanol, 2-butyl-2-ethyl-1,3-propanediol, and 1,4-bis(2-hydroxyethoxy)benzene; and triols such as glycerin, trimethylolethane, trimethylolpropane, and 1,2,6-hexanetriol.

The content of the structural units derived from the chain extender is not particularly limited, but may be, for example, 1 part by mass or more and 30 parts by mass or less, 3 parts by mass or more and 25 parts by mass or less, or 5 parts by mass or more and 20 parts by mass or less, per 100 parts by mass of the structural units derived from the polyphenylene ether polyol.

The glass transition temperature of polyurethane is preferably 100°C or higher, more preferably 110°C or higher, and even more preferably 120°C or higher. In this case, the heat resistance of polyurethane can be further improved. The upper limit of the glass transition temperature of polyurethane is usually 200°C.

The glass transition temperature of polyurethane is a value determined by dynamic viscoelasticity measurement. More specifically, a dried polyurethane film is used as a test piece, and dynamic viscoelasticity measurement of the test piece is performed in tensile mode under conditions of a heating rate of 2°C/min and a frequency of 1 Hz, and the maximum value of the loss tangent of the obtained curve is taken as the glass transition temperature.

From the viewpoint of processability, the weight average molecular weight of the polyurethane is preferably 30,000 or more, more preferably 50,000 or more, and even more preferably 70,000 or more. Furthermore, from the viewpoint of solubility in organic solvents, the weight average molecular weight of the polyurethane is preferably 200,000 or less.

From the viewpoint of processability, the number average molecular weight of the polyurethane is preferably 5,000 or more, more preferably 8,000 or more, and even more preferably 10,000 or more. Furthermore, from the viewpoint of solubility in organic solvents, the number average molecular weight of the polyurethane is preferably 40,000 or less.

From the viewpoint of solubility in organic solvents, the acid value of polyurethane is preferably 0 mgKOH/g or more and 30 mgKOH/g or less, more preferably 1 mgKOH/g or more and 20 mgKOH/g or less, and even more preferably 2 mgKOH/g or more and 10 mgKOH/g or less. The acid value of polyurethane is a value measured by neutralization titration of a sample with potassium hydroxide benzyl alcohol solution using a phenolphthalein solution as an indicator.

The method for producing the polyurethane is not particularly limited, and known methods can be used. For example, the polyol, polyisocyanate, and other compounds used as necessary may all be placed in a reaction vessel and then reacted, or raw materials such as polyol may be added to the reaction vessel in stages as the reaction progresses. In the polycondensation of polyester polyurethane, the amounts of raw materials added may be set so that the ratio of the total amount of isocyanate groups to the total amount of hydroxyl groups is preferably 0.9 to 1.1, more preferably 0.98 to 1.02, and particularly preferably 1.

The polycondensation reaction may be carried out in the presence of a solvent inactive to isocyanate groups, or may be carried out without using a solvent. As the solvent, the same solvent as that used in the polyamide polycondensation reaction described above can be used. From the viewpoint of reducing the environmental load, it is preferable to use ethyl acetate or methyl ethyl ketone as the solvent. As the reaction apparatus in which the polycondensation reaction is carried out, a reaction vessel equipped with a stirring device, a kneader, a mixing and kneading device such as a twin-screw extruder, etc. can be used.

When producing polyurethane, a catalyst for accelerating the urethanization reaction can be used as necessary to accelerate the urethanization reaction. Examples of this type of catalyst include tin-based catalysts such as trimethyltin laurate, dimethyltin dilaurate, trimethyltin hydroxide, dimethyltin dihydroxide, and stannous octoate; lead-based catalysts such as red oleate and red 2-ethylhexoate; and amine-based catalysts such as triethylamine, tributylamine, morpholine, diazabicyclooctane, and diazabicycloundecene.

Polyester Polyurethane The polyurethane resin used in the base resin (A) may be a polyester polyurethane. The adhesive composition may contain one type of polyester polyurethane, or may contain two or more types of polyester polyurethane.

The polyester polyurethane has a polyester portion in which multiple repeating units are bonded via ester bonds, and a polyurethane portion in which multiple repeating units are bonded via urethane bonds. The polyester portion may have two or more ester bonds. The polyurethane portion may have two or more urethane bonds. The polyester portion and the polyurethane portion may be bonded via ester bonds or urethane bonds.

The polyester polyurethane has, for example, a repeating unit derived from a polycarboxylic acid, a repeating unit derived from a polyol, and a repeating unit derived from a polyisocyanate. The polyester polyurethane may have, for example, a repeating unit derived from a dicarboxylic acid, a repeating unit derived from a diol, and a repeating unit derived from a diisocyanate.

In addition, the polyester polyurethane may contain repeating units derived from a polyester polyol, repeating units derived from a polyisocyanate, and a structure derived from a chain extender, or may contain repeating units derived from a polyester polyol, repeating units derived from a polyisocyanate, and a structure derived from a diol compound as a chain extender.

More specifically, the polyester portion of the polyester polyurethane has repeating units derived from polycarboxylic acid and repeating units derived from polyol. The number average molecular weight of the polyester portion of the polyester polyurethane is preferably 1,000 to 50,000, more preferably 2,000 to 40,000, even more preferably 3,000 to 30,000, particularly preferably 8,000 to 30,000, and most preferably 15,000 to 30,000. In this case, the heat resistance of the cured product in a hygroscopic state can be further improved.

Polycarboxylic acids used in the polyester portion include dicarboxylic acids similar to the polycarboxylic acids used in the polyamides described above, polycarboxylic acids having three or more carboxy groups, hydroxycarboxylic acids, and sulfocarboxylic acids.

The polyester portion of the polyester polyurethane preferably contains 30 mol% or more of repeating units derived from aromatic carboxylic acids, more preferably 45 mol% or more of repeating units derived from aromatic carboxylic acids, and even more preferably 60 mol% or more of repeating units derived from aromatic carboxylic acids, based on the total amount of repeating units derived from polycarboxylic acids contained in the polyester portion. In this case, the adhesive composition can have further improved adhesion, heat resistance, and moist heat resistance. Examples of aromatic carboxylic acids include aromatic polycarboxylic acids, aromatic sulfocarboxylic acids, and aromatic oxycarboxylic acids. From the viewpoint of further improving the adhesiveness of the adhesive composition, it is preferable that the polyester portion contains repeating units derived from one or two aromatic carboxylic acids selected from terephthalic acid and isophthalic acid. From the same viewpoint, it is more preferable that the aromatic carboxylic acid contained in the polyester portion is terephthalic acid and/or isophthalic acid.

The polyol used in the polyester portion may be the same diol or polyol as the polyol used in the polyamide described above. From the viewpoint of compatibility with the epoxy compound (B) and the like and solution stability, it is preferable that the polyester portion contains a repeating unit derived from a diol having a side chain. The side chain of the diol is preferably an alkyl group, more preferably an alkyl group having 1 to 5 carbon atoms. Examples of diols having a side chain include neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, and 2,2-dimethylolpropionic acid.

Furthermore, it is preferable that the polyester portion contains a repeating unit derived from a diol. In this case, the heat resistance of the cured product in a hygroscopic state can be further improved. From the viewpoint of obtaining such an effect more reliably, it is preferable that the polyester portion contains a repeating unit derived from a diol having a hydrocarbon group with 5 to 32 carbon atoms, more preferably contains a repeating unit derived from a diol having a hydrocarbon group with 5 to 16 carbon atoms, and particularly preferably contains a repeating unit derived from a diol having a hydrocarbon group with 7 to 12 carbon atoms.

From the same viewpoint, the repeating unit derived from the diol in the polyester portion preferably has a hydrocarbon group having 5 to 32 carbon atoms and has an alicyclic structure or two or more side chains, more preferably has two or more side chains, and particularly preferably has two side chains. The repeating unit derived from the diol described above may be contained in the polyester portion or in the polyurethane portion as described below, but from the viewpoint of more reliably obtaining the above-mentioned effect, it is preferable that the repeating unit derived from the diol described above is contained in the polyurethane portion.

The polyester portion of the polyester polyurethane may have a repeating unit derived from a polycarboxylic acid having three or more carboxy groups and/or a repeating unit derived from a polyol having three or more hydroxy groups. In this case, a branched chain can be introduced into the polyester portion. Also, by introducing a branched chain into the polyester portion, the end group concentration of the resin (i.e., the reaction points) can be increased. Therefore, for example, by reacting a polyester polyurethane into which a branched chain has been introduced with a curing agent, a cured layer with a high crosslink density can be obtained.

The sum of the content of repeating units derived from polycarboxylic acid and the content of repeating units derived from polyol is preferably 0.1 mol% or more and 5 mol% or less, and more preferably 0.1 mol% or more and 3 mol% or less, based on all repeating units in the polyester portion.

The polyurethane portion of the polyester polyurethane preferably contains repeating units derived from a diisocyanate, and more preferably contains repeating units derived from a diisocyanate having a hydrocarbon group with 8 to 14 carbon atoms. The methylene groups in the hydrocarbon group of the diisocyanate may be replaced with non-reactive bonds such as -O-, -S-, -CO-, -COO-, and -OCO-.

From the viewpoint of further improving the heat resistance of the cured product after moisture absorption, the number of carbon atoms in the hydrocarbon group in the diisocyanate is more preferably 8 to 12, and even more preferably 8 to 10. From the same viewpoint, it is preferable that the diisocyanate has an alicyclic structure.

The content of the repeating units derived from the diisocyanate in the polyurethane portion is preferably 70 mol% or more, more preferably 90 mol% or more, and even more preferably 100 mol% of the content of all repeating units derived from diisocyanates contained in the polyester polyurethane.

In addition, from the viewpoint of further improving the adhesiveness of the adhesive composition, the content of repeating units derived from diisocyanate in the polyester polyurethane is preferably 5 molar equivalents or more and 50 molar equivalents or less per 1 molar equivalent of the polyester portion. In other words, it is preferable that the polyester polyurethane has urethane bonds derived from diisocyanate in an amount of 10 molar equivalents or more and 100 molar equivalents or less per 1 molar equivalent of the polyester portion.

The polyurethane portion of polyester polyurethane may contain repeating units derived from monoisocyanates and repeating units derived from polyisocyanates having three or more isocyanates, in addition to repeating units derived from diisocyanates.

The polyisocyanate used in the polyurethane portion may be a diisocyanate similar to the polyisocyanate used in the polyurethane described above, or a polyisocyanate having three or more isocyanate groups. The polyurethane portion preferably contains repeating units derived from one or more isocyanates selected from the group consisting of chain aliphatic diisocyanates and alicyclic diisocyanates, and more preferably contains repeating units derived from alicyclic diisocyanates. In this case, the cured product of the adhesive composition can be made transparent. Also, in this case, the heat resistance of the cured product in a hygroscopic state can be further improved.

Furthermore, from the viewpoint of ease of availability, it is more preferable that the polyurethane portion contains repeating units derived from one or more isocyanates selected from the group consisting of 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, methylene bis(4-cyclohexyl diisocyanate), and norbornane diisocyanate, and it is particularly preferable that the polyurethane portion contains repeating units derived from 1,3-bis(isocyanatomethyl)cyclohexane.

The polyurethane portion may contain a repeating unit derived from a polyol. Examples of polyols used in the polyurethane portion include diols similar to the alcohols used in the polyester polyamides described above, and polyols having three or more hydroxyl groups. The polyurethane portion preferably contains a repeating unit derived from a diol having a side chain. The side chain of the diol is preferably an alkyl group, more preferably an alkyl group having 1 to 5 carbon atoms.

The polyurethane portion preferably contains a repeating unit derived from a diol. In this case, the heat resistance of the cured product in a hygroscopic state can be further improved. From the viewpoint of obtaining such an effect more reliably, the polyurethane portion preferably contains a repeating unit derived from a diol having a hydrocarbon group with 5 to 32 carbon atoms, more preferably contains a repeating unit derived from a diol having a hydrocarbon group with 5 to 16 carbon atoms, and particularly preferably contains a repeating unit derived from a diol having a hydrocarbon group with 7 to 12 carbon atoms.

From a similar perspective, the repeating unit derived from the diol in the polyurethane portion preferably has a hydrocarbon group having 5 to 32 carbon atoms and also has an alicyclic structure or two or more side chains, more preferably has two or more side chains, and particularly preferably has two side chains.

Chain extenders used in polyester polyurethanes include diols similar to those used in the polyester portion, and compounds with one carboxy group and two hydroxy groups, such as dimethylolpropionic acid and dimethylolbutanoic acid.

From the viewpoint of further improving the dispersibility of the filler, the chain extender is preferably a diol. In addition to the above effect, from the viewpoint of further improving compatibility with the epoxy compound (B) and the like and solution stability, the chain extender is more preferably a diol having a side chain, and particularly preferably a diol having a branched chain. The side chain of the diol is preferably an alkyl group, and more preferably an alkyl group having 1 to 5 carbon atoms. More specifically, the chain extender preferably contains at least one compound selected from the group consisting of neopentyl glycol, 2-butyl-2-ethyl-1,3-propanediol, and 2,2-dimethylolpropionic acid, and particularly preferably contains at least one compound selected from the group consisting of neopentyl glycol and 2-butyl-2-ethyl-1,3-propanediol, and 2,2-dimethylolpropionic acid.

Also, polyamines can be used as chain extenders. In this case, urea bonds are formed in the polyester polyurethane, but in some cases, it may be preferable for the polyester polyurethane to not contain urea bonds.

From the viewpoint of adhesion and heat resistance, the glass transition temperature of the polyester portion of the polyester polyurethane is preferably 40°C or higher and 150°C or lower, more preferably 45°C or higher and 120°C or lower, even more preferably 50°C or higher and 90°C or lower, and particularly preferably 60°C or higher and 70°C or lower.

In addition, from the viewpoint of adhesion and heat resistance, the glass transition temperature of the polyester polyurethane is preferably 30°C or higher and 150°C or lower, more preferably 40°C or higher and 140°C or lower, even more preferably 50°C or higher and 90°C or lower, and particularly preferably 60°C or higher and 70°C or lower.

From the viewpoint of heat resistance, the number average molecular weight of the polyester polyurethane is preferably 5,000 or more and 100,000 or less, more preferably 10,000 or more and 80,000 or less, even more preferably 20,000 or more and 60,000 or less, and particularly preferably 25,000 or more and 50,000 or less.

From the viewpoint of heat resistance, the molecular weight per urethane bond in polyester polyurethane is preferably 200 to 8,000, more preferably 200 to 5,000, even more preferably 300 to 2,000, particularly preferably 400 to 1,500, and most preferably 700 to 1,000. The molecular weight per urethane bond is obtained by dividing the number average molecular weight of polyester polyurethane by the number of urethane bonds per molecule. The number of urethane bonds per molecule can also be calculated, for example, based on the amount of raw material used in the synthesis of polyester polyurethane. More specifically, when polyester polyol and isocyanate are used in the synthesis of polyester polyurethane, the number of moles of isocyanate groups reacted with 1 mole of polyester polyol can be regarded as the "number of urethane bonds per molecule."

The method for producing polyester polyurethane is not particularly limited, and known methods can be used. For example, the above-mentioned polyester polyol, isocyanate, and other compounds used as necessary may all be placed in a reaction vessel and then reacted, or raw materials such as polyester polyol may be added to the reaction vessel in stages as the reaction progresses. In the polycondensation of polyester polyurethane, the amounts of raw materials added may be set so that the ratio of the total amount of isocyanate groups to the total amount of hydroxyl groups is preferably 0.9 to 1.1, more preferably 0.98 to 1.02, and particularly preferably 1.

The polycondensation reaction may be carried out in the presence of a solvent inactive to isocyanate groups, or may be carried out without using a solvent. As the solvent, the same solvent as that used in the polyurethane polycondensation reaction described above can be used. From the viewpoint of reducing the environmental load, it is preferable to use ethyl acetate or methyl ethyl ketone as the solvent. As the reaction apparatus in which the polycondensation reaction is carried out, a reaction vessel equipped with a stirring device, a kneader, a mixing and kneading device such as a twin-screw extruder, etc. can be used.

When producing polyester polyurethane, a catalyst used to promote the urethane reaction can be used as necessary to promote the urethane reaction. Examples of this type of catalyst include the same catalysts used for polyurethanes as described above.

When producing polyester polyurethane, acid addition may be carried out as necessary in order to introduce carboxy groups into the polyester polyurethane. The amount of carboxy groups introduced by acid addition may be, for example, within the range of 0.1 mol % to 10 mol % relative to the repeating units derived from carboxylic acid and the repeating units derived from alcohol contained in the polyester polyurethane. If a monocarboxylic acid, dicarboxylic acid or polyfunctional carboxylic acid compound is used in acid addition to polyester polyurethane, there is a risk of a decrease in molecular weight due to ester exchange. Therefore, when acid addition is carried out on polyester polyurethane, it is preferable to use an acid anhydride. Examples of acid anhydrides used in acid addition to polyester polyurethane include the same acid anhydrides as those used in acid addition to polyester polyamide.

[Epoxy compound (B)]
The adhesive composition contains 1 part by mass or more and 50 parts by mass or less of epoxy compound (B) per 100 parts by mass of base resin (A). The epoxy compound (B) has the effect of imparting adhesiveness to the adhesive composition and improving the heat resistance of the cured product of the adhesive composition. By making the content of the epoxy compound (B) 1 part by mass or more, preferably 5 parts by mass or more, more preferably 10 parts by mass or more per 100 parts by mass of base resin (A), the adhesiveness of the adhesive composition can be increased and the heat resistance of the cured product can be improved. If the content of the epoxy compound (B) is less than 1 part by mass per 100 parts by mass of base resin (A), the adhesiveness of the adhesive composition and the heat resistance of the cured product may be reduced.

On the other hand, if the content of the epoxy compound (B) is excessively high, the epoxy compound (B) may react easily with other functional groups in the adhesive composition, which may result in a decrease in storage stability. By setting the content of the epoxy compound (B) to 50 parts by mass or less, preferably 40 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 25 parts by mass or less, and particularly preferably 20 parts by mass or less, per 100 parts by mass of the base resin (A), such problems can be easily avoided.

When determining the preferred range of the content of the epoxy compound (B), the upper and lower limits of the content of the epoxy compound (B) described above can be combined in any way. For example, the preferred range of the content of the epoxy compound (B) may be 5 parts by mass or more and 40 parts by mass or less, 5 parts by mass or more and 30 parts by mass or less, 5 parts by mass or more and 25 parts by mass or less, or 10 parts by mass or more and 20 parts by mass or less, relative to 100 parts by mass of the base resin (A).

The adhesive composition may contain one type of epoxy compound (B), or may contain two or more types of epoxy compounds (B) having different structures. It is preferable that the epoxy compound (B) has two or more epoxy groups per molecule.

Examples of the epoxy compound (B) include glycidyl esters, glycidyl ethers, and epoxy resins. Examples of the glycidyl esters include orthophthalic acid diglycidyl ester, isophthalic acid diglycidyl ester, terephthalic acid diglycidyl ester, p-hydroxybenzoic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, succinic acid diglycidyl ester, adipic acid diglycidyl ester, sebacic acid diglycidyl ester, and trimellitic acid triglycidyl ester.

Examples of glycidyl ethers include diglycidyl ether of bisphenol A and its oligomers, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol tetraglycidyl ether, tetraphenylglycidyl ether ethane, triphenylglycidyl ether ethane, polyglycidyl ether of sorbitol, polyglycidyl ether of polyglycerol, etc.

Examples of epoxy resins include novolac type epoxy resins such as phenol novolac epoxy resin, o-cresol novolac epoxy resin, bisphenol A novolac epoxy resin, brominated bisphenol A type epoxy resin, phosphorus-containing epoxy resin, trisphenolmethane skeleton-containing epoxy resin, dicyclopentadiene skeleton-containing epoxy resin, naphthalene skeleton-containing epoxy resin, anthracene type epoxy resin, tertiary butyl catechol type epoxy resin, biphenyl type epoxy resin, and bisphenol S type epoxy resin.

From the viewpoint of adhesion and solder heat resistance, it is preferable that the adhesive composition contains a trisphenolmethane skeleton-containing epoxy resin as the epoxy compound (B).

From the viewpoint of further improving the heat resistance of the cured product of the adhesive composition, it is preferable that the epoxy compound (B) contains a compound having three or more epoxy groups in one molecule. By using such a compound, the crosslinking reactivity with the base resin (A) is increased, and the heat resistance of the cured product can be further improved.

From the viewpoint of further enhancing the effect of improving heat resistance, the content of the compound having three or more epoxy groups in one molecule is preferably 15% by mass or more, more preferably 20% by mass or more, and particularly preferably 25% by mass or more, based on the total mass of the epoxy compound (B).

[Triazine Compound (C)]
The adhesive composition contains 10 parts by mass or more and 70 parts by mass or less of a triazine-based compound (C) relative to 100 parts by mass of a base resin (A). The triazine-based compound (C) contains, in its molecular structure, one or more structures selected from a structure represented by the following general formula (C1) and a structure represented by the following structural formula (C2). The adhesive composition may contain one type of triazine-based compound (C), or may contain two or more types of triazine-based compounds (C).

In the general formula (C1), R ¹ to R ³ each independently represent an amino group, a hydroxyl group, a thiol group, a methyl group, or a phenyl group.

The triazine-based compound (C) containing the partial structure represented by the general formula (C1) or the partial structure represented by the structural formula (C2) is used in combination with the metal phosphinate (D) to not only improve the heat resistance of the cured product, but also to improve the heat resistance of the cured product in a hygroscopic state. Therefore, by setting the content of the triazine-based compound (C) containing the specific partial structure within the specific range, the heat resistance of the cured product in a hygroscopic state can be improved.

From the viewpoint of obtaining the above-mentioned effect more reliably, the content of the triazine-based compound (C) is preferably 13 parts by mass or more per 100 parts by mass of the base resin (A), more preferably 15 parts by mass or more, and even more preferably 17 parts by mass or more. If the content of the triazine-based compound (C) is less than 10 parts by mass per 100 parts by mass of the base resin (A), the above-mentioned effect will be reduced, and there is a risk of the heat resistance of the cured product in a moisture-absorbed state being reduced.

On the other hand, if the content of the triazine-based compound (C) is excessively high, the content of the triazine-based compound (C) will be excessive relative to the amount of the metal phosphinate (D), and it may be difficult to obtain the above-mentioned effect. In this case, the proportion of the base resin (A) will be relatively small, and there is a risk of causing a decrease in initial adhesion. By setting the content of the triazine-based compound (C) to 70 parts by mass or less, preferably 50 parts by mass or less, more preferably 40 parts by mass or less, even more preferably 30 parts by mass or less, and particularly preferably 25 parts by mass or less, per 100 parts by mass of the base resin (A), the balance between the triazine-based compound (C) and the metal phosphinate (D) can be maintained within an appropriate range, and the above-mentioned effect can be obtained more reliably.

When determining the preferred range of the content of the triazine-based compound (C), the upper and lower limits of the content of the triazine-based compound (C) described above can be combined in any way. For example, the preferred range of the content of the triazine-based compound (C) may be 13 parts by mass or more and 50 parts by mass or less, 15 parts by mass or more and 40 parts by mass or less, 15 parts by mass or more and 30 parts by mass or less, 15 parts by mass or more and 25 parts by mass or less, or 17 parts by mass or more and 25 parts by mass or less.

The triazine-based compound (C) may be a compound represented by the general formula (C1) or structural formula (C2), or may be a salt of these compounds. More specifically, examples of the triazine-based compound (C) include melamine, acetoguanamine, benzoguanamine, trithiocyanuric acid, cyanuric acid, and isocyanuric acid. The triazine-based compound (C) may also be a salt of a compound represented by the general formula (C1) or structural formula (C2), such as melamine phosphate, melamine polyphosphate, and melamine cyanurate.

From the viewpoint of further improving the heat resistance of the cured product in a hygroscopic state, it is preferable that the triazine-based compound (C) contains a structure represented by the following structural formula (C3) in its molecular structure. In other words, it is preferable that the triazine-based compound (C) is one or more compounds selected from the group consisting of melamine and salts of melamine.

The volumetric median diameter of the triazine compound (C) is preferably 10 μm or less. In this case, the dispersibility of the triazine compound (C) in the adhesive composition is improved, and the heat resistance of the cured product in a hygroscopic state can be further improved.

The median diameter of the triazine compound (C) is a value calculated based on the volumetric particle size distribution obtained by measuring the triazine compound (C) using a laser diffraction/scattering particle size distribution measuring device (for example, "LS 13320" manufactured by Beckman Coulter, Inc.) with a Tornado dry powder sample module. More specifically, the median diameter of the triazine compound (C) indicates the particle size at which the integrated volume of the particles, calculated from the fine particle side, is 50% by volume in the volumetric particle size distribution.

[Metal phosphinate (D)]
The adhesive composition contains 0.5 parts by mass or more and 50 parts by mass or less of the phosphinic acid metal salt (D) relative to 100 parts by mass of the base resin (A). The adhesive composition may contain one type of the phosphinic acid metal salt (D), or may contain two or more types of the phosphinic acid metal salt (D). By setting the content of the phosphinic acid metal salt (D) in the adhesive composition within the specific range, the flame retardancy of the cured product of the adhesive composition can be improved. In addition, by using the phosphinic acid metal salt (D) in combination with the triazine compound (C), the heat resistance of the cured product in a hygroscopic state can be improved.

From the viewpoint of obtaining the above-mentioned effect more reliably, the content of the metal phosphinate (D) is preferably 1 part by mass or more per 100 parts by mass of the base resin (A), more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more. If the content of the metal phosphinate (D) is less than 0.5 parts by mass per 100 parts by mass of the base resin (A), this may lead to a decrease in the flame retardancy of the cured product.

On the other hand, the metal phosphinate (D) has a tendency to easily absorb moisture. Therefore, if the content of the metal phosphinate (D) is excessively high relative to the amount of the triazine-based compound (C), the effect of moisture absorption by the metal phosphinate (D) becomes large, and the heat resistance of the cured product in a hygroscopic state may decrease. By setting the content of the metal phosphinate (D) to 50 parts by mass or less, preferably 40 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 25 parts by mass or less, and particularly preferably 20 parts by mass or less, relative to 100 parts by mass of the base resin (A), the balance between the triazine-based compound (C) and the metal phosphinate (D) can be maintained within an appropriate range, and the above-mentioned effects can be obtained more reliably.

When determining the preferred range of the content of the metal phosphinate (D), the upper and lower limits of the content of the metal phosphinate (D) described above can be combined in any way. For example, the preferred range of the content of the metal phosphinate (D) may be 1 part by mass or more and 40 parts by mass or less, 3 parts by mass or more and 30 parts by mass or less, 3 parts by mass or more and 25 parts by mass or less, or 5 parts by mass or more and 20 parts by mass or less.

As the metal phosphinate, for example, a compound represented by the following general formula (D1) can be used.

In the general formula (D1), ^R7 and ^R8 each independently represent an unsubstituted aliphatic hydrocarbon group, a substituted aliphatic hydrocarbon group, an unsubstituted aromatic hydrocarbon group, or a substituted aromatic hydrocarbon group, n represents an integer of 1 or more and 4 or less, and M represents an n-valent metal.

The aliphatic hydrocarbon group used as ^R7 and ^R8 may be, for example, an unsubstituted alkyl group, an alkyl group having a substituent, an unsubstituted alkenyl group, an alkenyl group having a substituent, an unsubstituted alkynyl group, or an alkynyl group having a substituent. Examples of the substituent include a halogen atom, a hydroxyl group, a carboxyl group, an alkoxy group, a cyano group, and an aromatic hydrocarbon group. The aromatic hydrocarbon group as the substituent is the same as the aromatic hydrocarbon group as ^R7 and ^R8 described below.

The number of carbon atoms in the portion excluding the substituents in the aliphatic hydrocarbon group is not particularly limited, but may be 1 to 10, 1 to 5, or 1 to 3. In addition, the total number of carbon atoms in the aliphatic hydrocarbon group, that is, the total number of carbon atoms in the portion excluding the substituents and the number of carbon atoms in the substituents, may be 1 to 30, 3 to 20, or 6 to 15.

The aliphatic hydrocarbon group used as ^R7 and ^R8 is preferably an unsubstituted or substituted alkyl group, more preferably an unsubstituted or substituted ethyl group, and even more preferably an unsubstituted ethyl group.

The aromatic hydrocarbon group used as ^R7 and ^R8 may be, for example, an unsubstituted phenyl group, a phenyl group having a substituent, an unsubstituted naphthyl group, or a naphthyl group having a substituent. Examples of the substituent include a halogen atom, a hydroxyl group, a carboxyl group, an alkoxy group, a cyano group, and an aliphatic hydrocarbon group. The aliphatic hydrocarbon group as the substituent is the same as the aliphatic hydrocarbon group as ^R7 and ^R8 described above.

The number of carbon atoms in the portion excluding the substituents in the aromatic hydrocarbon group is not particularly limited, but may be 6 to 12, or 6 to 8. In addition, the total number of carbon atoms in the aliphatic hydrocarbon group, that is, the total number of carbon atoms in the portion excluding the substituents and the number of carbon atoms in the substituents, may be 1 to 30, or 3 to 20, or 6 to 15.

The metal M in the general formula (D1) may be, for example, lithium, sodium, potassium, calcium, magnesium, aluminum, titanium, or zinc. M in the general formula (D1) is preferably aluminum. Furthermore, n in the general formula (D1) is preferably 2 or more and 4 or less, and more preferably 3.

As the metal phosphinate (D), for example, commercially available products such as "Exolit (registered trademark) OP930", "Exolit OP935", "Exolit OP945", and "Exolit OP1230" manufactured by Clariant can also be used.

[Inorganic filler]
The adhesive composition may further contain an inorganic filler. In this case, the solder heat resistance of the adhesive composition can be further improved. The content of the inorganic filler is preferably 10 parts by mass or more and 350 parts by mass or less per 100 parts by mass of the total content of the base resin (A), the epoxy compound (B), and the triazine compound (C).

Examples of inorganic fillers include non-conductive inorganic fillers such as calcium carbonate particles, titanium oxide particles, aluminum oxide particles, zinc oxide particles, talc particles, and silica particles, and conductive inorganic fillers such as carbon black particles and conductive metal particles.

[Imidazole silane (E)]
The adhesive composition may contain imidazole silane (E) having one or more imidazole ring structures and one or more silane structures. By blending imidazole silane (E) in the adhesive composition, the adhesiveness to metal, particularly to gold-plated copper foil, can be improved. This is considered to be because the silane structure and imidazole ring structure in imidazole silane (E) show high affinity with the metal surface. It is also presumed that imidazole silane (E) acts as a curing agent for epoxy compound (B). Therefore, it is presumed that the adhesive composition can maintain its adhesiveness-improving effect even when the adhesive composition or its cured product is heated, for example, in a reflow process.

The silane structure in the imidazole silane (E) is preferably a silyl group, and more preferably an alkoxysilyl group. In this case, the solder heat resistance of the adhesive composition can be further improved.

The imidazole ring structure in the imidazole silane (E) may have an imidazole ring having a substituent such as a saturated hydrocarbon group or an unsaturated hydrocarbon group. More specifically, the imidazole ring structure may include an imidazole ring, a 2-alkylimidazole ring, a 2,4-dialkylimidazole ring, a 4-vinylimidazole ring, etc.

From the viewpoint of further enhancing the adhesiveness of the adhesive composition, it is more preferable that the imidazole silane (E) is a compound represented by the following general formula (E1) or an acid adduct thereof.

R ⁹ and R ¹⁰ in the general formula (E1) each independently represent a hydrogen atom, a saturated hydrocarbon group, an unsaturated hydrocarbon group, or an aryl group. The saturated hydrocarbon group, the unsaturated hydrocarbon group, and the aryl group in R ⁹ and R ¹⁰ may have a substituent. R ¹¹ and R ¹² in the general formula (E1) each independently represent a hydrogen atom or an alkyl group. At least one of R ¹¹ is an alkyl group. n is an integer of 1 to 3. The number of carbon atoms in the alkyl groups in R ⁹ to R ¹² is preferably 1 to 3. The alkyl groups in R ¹¹ and R ¹² may have a substituent.

R ¹³ in the general formula (E1) represents an alkylene group or a group in which an alkylene group is partially substituted with one or more divalent organic groups represented by the following structural formulas (E2) to (E5): The number of carbon atoms in the alkylene group in ^{R 13} is preferably 1 to 10, and more preferably 3 to 7.

In the structural formula (E2), R ¹⁴ represents a hydrogen atom or a hydroxyl group. In the structural formula (E3), R ¹⁵ represents a hydrogen atom, an alkyl group, or an aryl group. In the structural formula (E5), R ¹⁶ and R ¹⁷ each independently represent a hydrogen atom, an alkyl group, or an aryl group. The alkyl group and the aryl group in R ¹⁵ , R ¹⁶ , and R ¹⁷ may have a substituent.

Imidazole silane (E) can be suitably synthesized, for example, by reacting an imidazole compound with a 3-glycidoxyalkylsilane compound or the like. In addition, imidazole silane (E) may have a silanol group generated by hydrolysis of an alkoxysilyl group, or may have a polyorganosiloxane structure generated by a dehydration condensation reaction of a silanol group. In addition, imidazole silane (E) may have both a silanol group and a polyorganosiloxane structure.

Examples of the acid to be added to the compound represented by the general formula (E1) include acetic acid, lactic acid, salicylic acid, benzoic acid, adipic acid, phthalic acid, citric acid, tartaric acid, maleic acid, trimellitic acid, phosphoric acid, and isocyanuric acid. These acids may be used alone or in combination of two or more kinds.

From the viewpoint of adhesion, it is more preferable that the imidazole silane (E) is a compound represented by the following general formula (E6) or general formula (E7), or an acid adduct thereof.

R ⁹ and R ¹⁰ in the general formula (E6) and general formula (E7) each independently represent a hydrogen atom, a saturated hydrocarbon group, an unsaturated hydrocarbon group, or an aryl group. The saturated hydrocarbon group, the unsaturated hydrocarbon group, and the aryl group in R ⁹ and R ¹⁰ may have a substituent. R ¹¹ and R ¹² in the general formula (E6) and general formula (E7) each independently represent a hydrogen atom or an alkyl group. At least one of R ¹¹ is an alkyl group. n is an integer of 1 to 3. The number of carbon atoms of the alkyl group in R ⁹ to R ¹² is preferably 1 to 3. The alkyl group in ^{R 11} and R ¹² may have a substituent.

In the general formulae (E6) and (E7), R ^13′ represents an alkylene group. The number of carbon atoms in the alkylene group in R ^13′ is preferably 1 to 10, and more preferably 3 to 7. In the general formulae (E6) and (E7), R ¹⁴ represents a hydrogen atom or a hydroxyl group.

More specifically, examples of imidazole silane (E) include 1-(2-hydroxy-3-trimethoxysilylpropoxypropyl)imidazole, 1-(2-hydroxy-3-triethoxysilylpropoxypropyl)imidazole, 1-(2-hydroxy-3-tripropoxysilylpropoxypropyl)imidazole, 1-(2-hydroxy-3-tributoxysilylpropoxypropyl)imidazole, 1-(2-hydroxy-3-triethoxysilylpropoxypropyl)imidazole, 1-(2-hydroxy-3-triethoxysilylpropoxypropyl)-2-methylimidazole, 1-(2-hydroxy-3-triethoxysilylpropoxypropyl)-4-methylimidazole, 1-(3-oxo-4-trimethoxysilylpropoxypropyl)imidazole, and 1-(3-trimethoxysilylpropylamino)imidazole.

From the viewpoint of further improving the solubility of the adhesive composition in a solvent and further improving the heat resistance of the cured product of the adhesive composition, it is more preferable that the imidazole silane (E) is an acid adduct of the compound represented by the general formula (E6) above.

The compound represented by the general formula (E6) can be easily obtained by reacting an imidazole compound with a 3-glycidoxypropylsilane compound. Examples of the imidazole compound include imidazole, 2-alkylimidazole, 2,4-dialkylimidazole, and 4-vinylimidazole. Examples of the 3-glycidoxypropylsilane compound include 3-glycidoxypropyltrialkoxysilane, 3-glycidoxypropyldialkoxyalkylsilane, and 3-glycidoxypropylalkoxydialkylsilane. Among these, it is particularly preferable that the compound represented by the general formula (E6) is a reaction product of imidazole and 3-glycidoxypropyltrimethoxysilane.

The compound represented by the general formula (E7) can be easily obtained by reacting an imidazole compound with 3-methacryloyloxypropyltrimethoxysilane or the like.

The adhesive composition may contain one type of imidazole silane (E) or may contain two or more types of imidazole silane (E). From the viewpoint of adhesion, the content of imidazole silane (E) is preferably 0.05 parts by mass or more and 20 parts by mass or less, more preferably 0.1 parts by mass or more and 10 parts by mass or less, and particularly preferably 1 part by mass or more and 5 parts by mass or less, relative to 100 parts by mass of the total of the content of base resin (A) and the content of epoxy compound (B).

[Organic filler]
The adhesive composition may further contain an organic filler. By blending the organic filler in the adhesive composition, the solder heat resistance and the moist heat resistance can be further improved. In addition, since the organic filler has excellent compatibility with the base resin (A) and the like, by blending the organic filler in the liquid adhesive composition, the stability of the liquid can be improved.

Examples of organic fillers include (meth)acrylic resin particles, polybutadiene particles, nylon particles, polyolefin particles, polyester particles, polycarbonate particles, polyvinyl alcohol particles, polyvinyl ether particles, polyvinyl butyral particles, silicone rubber particles, polyurethane particles, phenolic resin particles, and polytetrafluoroethylene particles. The adhesive composition may contain one type of organic filler among these organic fillers, or may contain two or more types of organic fillers. From the viewpoint of further enhancing the above-mentioned effects, it is more preferable that the organic filler is one or two or more types of particles selected from the group consisting of silicone particles, polybutadiene particles, (meth)acrylic resin particles, and polyurethane particles.

The median diameter of the organic filler on a volume basis is not particularly limited, but from the viewpoint of improving the applicability and making it easier to adjust the coating thickness, it is preferably 0.5 μm or more and 50 μm or less, and more preferably 1 μm or more and 30 μm or less.

From the viewpoint of adhesion and curability, the content of the organic filler is preferably 1 part by mass or more and 50 parts by mass or less, more preferably 5 parts by mass or more and 40 parts by mass or less, and particularly preferably 10 parts by mass or more and 20 parts by mass or less, relative to 100 parts by mass of the total content of the base resin (A), the epoxy compound (B), and the triazine compound (C).

[Additives]
The adhesive composition may contain additives other than the above-mentioned components within a range that does not impair the above-mentioned effects. Examples of additives include thermoplastic resins other than the base resin (A), tackifiers, flame retardants, curing agents, curing accelerators, coupling agents, heat aging inhibitors, leveling agents, defoamers, and solvents.

Thermoplastic resins that may be included in the adhesive composition include, for example, phenoxy resins, polyamide resins, polycarbonate resins, polyphenylene oxide resins, polyester resins, polyacetal resins, polyethylene-based resins, polypropylene-based resins, and polyvinyl-based resins. The adhesive composition may contain one type of thermoplastic resin among these thermoplastic resins, or may contain two or more types of thermoplastic resins.

Examples of tackifiers include coumarone-indene resins, terpene resins, terpene-phenol resins, rosin resins, p-t-butylphenol-acetylene resins, phenol-formaldehyde resins, xylene-formaldehyde resins, petroleum-based hydrocarbon resins, hydrogenated hydrocarbon resins, and turpentine-based resins. The adhesive composition may contain one of these tackifiers, or may contain two or more tackifiers.

As the flame retardant, organic flame retardants and inorganic flame retardants can be used. Examples of organic flame retardants include phosphorus-based flame retardants other than metal phosphinate salts (D), such as guanidine phosphate, guanidine polyphosphate, ammonium phosphate, ammonium polyphosphate, ammonium amide phosphate, ammonium amide polyphosphate, carbamate phosphate, and carbamate polyphosphate; nitrogen-based flame retardants other than triazine-based compounds (C), such as triazole compounds, tetrazole compounds, diazo compounds, and urea; and silicon-based flame retardants such as silicone compounds and silane compounds.

Examples of inorganic flame retardants include metal hydroxides such as aluminum hydroxide, magnesium hydroxide, zirconium hydroxide, barium hydroxide, and calcium hydroxide; metal oxides such as tin oxide, aluminum oxide, magnesium oxide, zirconium oxide, zinc oxide, molybdenum oxide, and nickel oxide; metal carbonates such as zinc carbonate, magnesium carbonate, calcium carbonate, and barium carbonate; metal borides such as zinc borate; and hydrated glass. The adhesive composition may contain one type of these flame retardants, or may contain two or more types of flame retardants.

The curing agent is used to form a crosslinked structure by reaction with the epoxy compound (B). Examples of the curing agent include acid-based curing agents, basic active hydrogen-based curing agents, polymercaptan-based curing agents, novolac resin-based curing agents, urea resin-based curing agents, and melamine resin-based curing agents. Examples of the acid-based curing agent include amine-based curing agents (e.g., chain aliphatic diamines, chain aliphatic polyamines, alicyclic diamines, and aromatic diamines), polyamidoamine-based curing agents, chain aliphatic polycarboxylic acids, alicyclic polycarboxylic acids, aromatic polycarboxylic acids, and their acid anhydrides.

Examples of chain aliphatic diamine curing agents include ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, hexamethylenediamine, polymethylenediamine, polyetherdiamine, 2,5-dimethylhexamethylenediamine, and trimethylhexamethylenediamine.

Examples of chain aliphatic polyamine curing agents include diethylenetriamine, iminobis(hexamethylene)triamine, trihexatetramine, tetraethylenepentamine, aminoethylethanolamine, tri(methylamino)hexane, dimethylaminopropylamine, diethylaminopropylamine, and methyliminobispropylamine.

Examples of alicyclic diamine curing agents include benzenediamine, isophoronediamine, bis(4-amino-3-methyldicyclohexyl)methane, diaminodicyclohexylmethane, bis(aminomethyl)cyclohexane, N-ethylaminopiperazine, 3,9-bis(3-aminopropyl)2,4,8,10-tetraoxaspiro[5.5]undecane, and hydrogenated metaxylylenediamine.

Examples of aromatic diamine curing agents include metaphenylenediamine, diaminodiphenylmethane, diaminodiphenylsulfone, diaminodiethyldiphenylmethane, and metaxylylenediamine.

Examples of chain aliphatic polycarboxylic acid-based hardeners and acid anhydride-based hardeners include succinic acid, adipic acid, dodecenyl succinic anhydride, polyadipic anhydride, polyazelaic anhydride, and polysebacic anhydride.

Examples of alicyclic polycarboxylic acid-based hardeners and acid anhydride-based hardeners include methyltetrahydrophthalic acid, methylhexahydrophthalic acid, methylhimic acid, hexahydrophthalic acid, tetrahydrophthalic acid, trialkyltetrahydrophthalic acid, methylcyclodicarboxylic acid, and their acid anhydrides.

Aromatic polycarboxylic acid-based hardeners and acid anhydride-based hardeners include, for example, phthalic acid, trimellitic acid, pyromellitic acid, benzophenone tetracarboxylic acid, ethylene glycol glycol bistrimellitic acid, glycerol tristrimellitic acid, and their acid anhydrides.

Basic active hydrogen curing agents include, for example, dicyandiamide and organic acid dihydrazides. Polymercaptan curing agents include, for example, mercaptoated epoxy resins and mercaptopropionic acid esters. Novolac resin curing agents include, for example, phenol novolac curing agents and cresol novolac curing agents.

The adhesive composition may contain one type of the curing agent described above, or may contain two or more types of curing agents. From the viewpoint of further improving adhesion and heat resistance, the functional group equivalent of the curing agent in the adhesive composition is preferably 0.2 molar equivalents or more and 2.5 molar equivalents or less relative to 1 molar equivalent of the epoxy group of the epoxy compound (B), and more preferably 0.4 molar equivalents or more and 2.0 molar equivalents or less.

The curing accelerator is a component used to accelerate the reaction of the epoxy compound (B). As the curing accelerator, a tertiary amine curing accelerator, a tertiary amine salt curing accelerator, an imidazole curing accelerator, etc. can be used.

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

Tertiary amine salt curing accelerators include, for example, the formate, octylate, p-toluenesulfonate, o-phthalate, phenol salt, or phenol novolac resin salt of 1,8-diazabicyclo[5.4.0]undecene, and the formate, octylate, p-toluenesulfonate, o-phthalate, phenol salt, or phenol novolac resin salt of 1,5-diazabicyclo[4.3.0]nonene.

Examples of imidazole-based curing accelerators include 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-methyl-4-ethylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, '-undecylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-ethyl-4'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine isocyanuric acid adduct, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, and 2-phenyl-4-methyl-5-hydroxymethylimidazole.

The adhesive composition may contain one type of the curing accelerators described above, or may contain two or more types of curing accelerators. From the viewpoints of adhesion and heat resistance, the content of the curing accelerator is preferably 1 part by mass or more and 10 parts by mass or less, and more preferably 2 parts by mass or more and 5 parts by mass or less, per 100 parts by mass of the epoxy compound (B).

Examples of coupling agents include silane coupling agents, titanate coupling agents, aluminate coupling agents, and zirconium coupling agents. Examples of silane coupling agents include vinyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, p-styryltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, 3-ureidopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, bis(triethoxysilylpropyl)tetrasulfide, 3-isocyanatopropyltriethoxysilane, and imidazole silane. The adhesive composition may contain one of these coupling agents, or may contain two or more of these coupling agents.

Heat aging inhibitors include, for example, phenol-based antioxidants, sulfur-based antioxidants, and phosphorus-based antioxidants. Phenol-based antioxidants include, for example, 2,6-di-tert-butyl-4-methylphenol, n-octadecyl-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate, and tetrakis[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane.

Examples of sulfur-based antioxidants include dilauryl-3,3'-thiodipropionate and dimyristyl-3,3'-dithiopropionate. Examples of phosphorus-based antioxidants include trisnonylphenyl phosphite and tris(2,4-di-tert-butylphenyl)phosphite. The adhesive composition may contain one of these heat aging inhibitors, or may contain two or more types of heat aging inhibitors.

The adhesive composition preferably further contains a solvent. In this case, a liquid adhesive composition can be obtained. By making the adhesive composition liquid, application to the adherend and formation of the adhesive layer can be smoothly performed, and an adhesive layer of the desired thickness can be easily formed. More specifically, the liquid adhesive composition may be a solution in which solids are dissolved in a solvent, or a dispersion in which solids are dispersed in a solvent.

Solvents include, for example, alcohol-based solvents, ketone-based solvents, aromatic hydrocarbon-based solvents, ester-based solvents, and aliphatic hydrocarbon-based solvents. Alcohol-based solvents include, for example, methanol, ethanol, isopropyl alcohol, n-propyl alcohol, isobutyl alcohol, n-butyl alcohol, benzyl alcohol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, and diacetone alcohol.

Examples of ketone-based solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclohexanone, and isophorone. Examples of aromatic hydrocarbon-based solvents include toluene, xylene, ethylbenzene, and mesitylene. Examples of ester-based solvents include methyl acetate, ethyl acetate, ethylene glycol monomethyl ether acetate, and 3-methoxybutyl acetate. Examples of aliphatic hydrocarbon-based solvents include hexane, heptane, cyclohexane, and methylcyclohexane. The adhesive composition may contain one of these solvents, or two or more of them.

The base resin (A) has the property of being easily soluble in protic solvents. Therefore, from the viewpoint of dissolving the base resin (A) in a solvent more easily, it is preferable that the adhesive composition contains an alcohol-based solvent. When the adhesive composition contains a solvent, from the viewpoint of workability including film-forming ability, the solids concentration of the adhesive composition is preferably 3% by mass or more and 80% by mass or less, and more preferably 10% by mass or more and 50% by mass or less.

[Method of using the adhesive composition]
The method of using the adhesive composition is not particularly limited, and the adhesive composition can be used in various modes. For example, the adhesive composition can be used as an adhesive for bonding two adherends. In addition, for example, the adhesive composition can be applied to the surface of an adherend and then cured to obtain a laminate containing a cured product of the adhesive composition. The adherend to which the adhesive composition is applied may be composed of a metal material such as copper, aluminum, and stainless steel, or may be composed of a polymer material such as a polyimide resin, a polyether ether ketone resin, a polyphenylene sulfide resin, a modified polyimide resin, and a liquid crystal polymer. In addition, the shape of the adherend is not particularly limited, and can take various forms. In addition, more detailed uses of the adhesive composition will be described later.

(Bonding film)
A bonding film can be obtained by providing an uncured product of the adhesive composition or a semi-cured product obtained by partially curing the adhesive composition on a release film. The bonding film has an adhesive layer and a release film provided on one or both sides of the adhesive layer and configured to be peelable from the adhesive layer. The adhesive layer in the bonding film is composed of the adhesive composition or a semi-cured product obtained by partially curing the adhesive composition.

The bonding film has an adhesive layer composed of an uncured adhesive composition or a semi-cured product of the adhesive composition. The adhesive layer is provided on a release film. Therefore, after the adhesive layer is applied to an adherend, the release film can be peeled off from the adhesive layer, and another adherend can be applied onto the adhesive layer. Furthermore, since the adhesive layer is composed of an uncured or semi-cured product of the adhesive composition, the curing reaction can be further promoted by heating or the like. Therefore, the two adherends can be bonded by curing the adhesive layer with the adhesive layer interposed between them.

Also, as mentioned above, the cured product of the adhesive composition exhibits excellent heat resistance even when hygroscopic, and is able to prevent peeling of the adherend after heating. Therefore, with the bonding film, even when two adherends are bonded together when the adherends or adhesive layer are not sufficiently dry, peeling of the cured product from the adherend when heated can be prevented. A bonding film with such properties is suitable for the manufacture of FPCs and FPC-related products.

The release film in the bonding film is configured so that it can be peeled off from the adhesive layer without damaging the adhesive layer. Examples of release films include polyethylene terephthalate film, polyethylene film, polypropylene film, silicone release treated paper, polyolefin resin coated paper, polymethylpentene (TPX) film, and fluorine-based resin film. The thickness of the release film is preferably 20 μm or more and 100 μm or less.

The thickness of the adhesive layer is preferably 5 μm or more and 100 μm or less, more preferably 5 μm or more and 70 μm or less, even more preferably 5 μm or more and 50 μm or less, and particularly preferably 10 μm or more and 40 μm or less. The adhesive layer preferably does not substantially contain any solvent. The "adhesive layer does not substantially contain any solvent" state includes a state in which the adhesive layer does not contain any solvent at all, and a state in which the adhesive layer contains a solvent to the extent that it does not interfere with maintaining the shape of the adhesive layer and attachment to the adherend.

The method for producing the bonding film is not particularly limited, and known methods can be appropriately adopted. For example, when producing a bonding film using an adhesive composition containing a solvent, the adhesive composition is applied to the surface of a release film, and then at least a portion of the solvent is removed from the adhesive composition on the release film to form an adhesive layer on the release film, thereby obtaining a bonding film. As a method for applying the adhesive composition to a release film, an appropriate method may be selected from known application methods such as gravure coating, kiss coating, die coating, lip coating, comma coating, blade coating, roll coating, knife coating, spray coating, bar coating, spin coating, and dip coating.

The method for removing the solvent from the adhesive composition is not particularly limited, but for example, the adhesive composition can be dried by various heating methods such as hot air drying, far-infrared heating, and high-frequency induction. In this case, the drying temperature for the adhesive composition is preferably 40°C or higher and 250°C or lower, and more preferably 70°C or higher and 170°C or lower.

(Laminate with adhesive layer)
A laminate with an adhesive layer can be obtained by providing an uncured or semi-cured product of the adhesive composition on a substrate layer. The laminate with an adhesive layer has an adhesive layer and a substrate layer adhered to at least one surface of the adhesive layer. The adhesive layer in the laminate with an adhesive layer is composed of the adhesive composition or a semi-cured product obtained by partially curing the adhesive composition.

The laminate with the adhesive layer has an adhesive layer composed of an uncured adhesive composition or a semi-cured product of the adhesive composition. The adhesive layer is provided on a substrate layer. Therefore, after the adhesive layer is applied to the adherend, the adhesive layer can be further cured to bond the laminate with the adhesive layer to the adherend.

Also, as mentioned above, the adhesive composition can suppress peeling of the adherend after heating even if the adherend is not sufficiently dried. Therefore, with the laminate with the adhesive layer, even if the adherend is bonded in a state where the adherend or the adhesive layer is not sufficiently dried, peeling of the adherend from the cured product when the cured product is heated can be suppressed. A laminate with an adhesive layer having such properties is suitable for the manufacture of FPCs and FPC-related products.

The base layer in the laminate with the adhesive layer is preferably a resin film, more preferably a resin film having electrical insulation. Examples of resins that can be used for the resin film include polyimide resin, modified polyimide resin, mixed resin of polyimide resin and modified polyimide resin, liquid crystal polymer, and fluororesin. The resin that can be used for the resin film is preferably polyimide resin, modified polyimide resin, or mixed resin of polyimide resin and modified polyimide resin, more preferably polyimide resin. The resin film may contain additives as necessary. The surface of the base layer to which the adhesive layer is attached may be surface-treated. A laminate with an adhesive layer having an electrically insulating resin film and an electrically insulating adhesive layer provided on the resin film may be called a coverlay film.

The thickness of the base layer and the thickness of the adhesive layer in the laminate with an adhesive layer may be set appropriately depending on the application of the laminate with an adhesive layer. For example, from the viewpoint of improving the electrical properties of the laminate with an adhesive layer, it is preferable to make the thickness of the base layer thin. For example, it is preferable that the thickness of the base layer is 3 μm or more and 125 μm or less.

The thickness of the adhesive layer in the laminate with the adhesive layer is preferably 5 μm or more and 100 μm or less, more preferably 5 μm or more and 70 μm or less, even more preferably 5 μm or more and 50 μm or less, and particularly preferably 10 μm or more and 40 μm or less.

The ratio of the thickness of the adhesive layer to the thickness of the base layer is preferably 1 or more and 10 or less, and more preferably 1 or more and 5 or less. Furthermore, it is preferable that the thickness of the adhesive layer is thicker than the thickness of the base layer.

The laminate with the adhesive layer may have a release film on the adhesive layer, if necessary. The release film provided on the adhesive layer is the same as the release film used in the bonding film described above.

The method for producing a laminate with an adhesive layer is the same as the method for producing a bonding film described above. That is, for example, when a laminate with an adhesive layer is produced using an adhesive composition containing a solvent, the adhesive composition is applied to the surface of the base layer, and then at least a portion of the solvent is removed from the adhesive composition on the base layer to form an adhesive layer on the base layer, thereby obtaining a laminate with an adhesive layer.

(Laminate)
The adhesive composition can also be used to prepare a laminate containing a cured product of the adhesive composition. The laminate has a cured product layer made of the cured product of the adhesive composition. The thickness of the cured product layer can be appropriately set depending on the application of the laminate. The thickness of the cured product layer is preferably 5 μm or more and 100 μm or less, more preferably 5 μm or more and 70 μm or less, even more preferably 5 μm or more and 50 μm or less, and particularly preferably 10 μm or more and 40 μm or less.

The laminate may be a flexible copper-clad laminate comprising a resin film, a cured layer provided on at least one side of the resin film, and copper foil provided on the cured layer. The adhesive composition has excellent adhesion to copper-containing articles. Therefore, the flexible copper-clad laminate obtained using the adhesive composition has excellent durability and the copper foil is less likely to peel off.

The resin film in the flexible copper-clad laminate may be composed of, for example, polyimide resin, modified polyimide resin, a mixed resin of polyimide resin and modified polyimide resin, liquid crystal polymer, and fluororesin. Of these resins, the resin film is preferably composed of polyimide resin, modified polyimide resin, or a mixed resin of polyimide resin and modified polyimide resin. The copper foil in the flexible copper-clad laminate may be electrolytic copper foil or rolled copper foil. The copper foil may also be plated with other metals or alloys. The thickness of the cured layer in the flexible copper-clad laminate is preferably 5 μm or more and 50 μm or less, and more preferably 10 μm or more and 40 μm or less.

The method for producing the laminate is not particularly limited, and known methods can be appropriately adopted. For example, when a laminate including a first adherend and a second adherend is produced using an adhesive composition containing a solvent, the adhesive composition is applied to the surface of the first adherend, and then the adhesive composition is dried to form an adhesive layer on the first adherend. Next, the surface of the adhesive layer is brought into surface contact with the second adherend, and lamination is performed at a temperature of, for example, 80°C to 150°C. This makes it possible to obtain a laminate having the first adherend, the adhesive layer provided on the first adherend, and the second adherend provided on the adhesive layer.

Then, the laminate can be pressed while being heated to harden the adhesive layer to form a hardened layer. The conditions for performing the heat press are not particularly limited as long as they are capable of bonding the adhesive layer to the adherend. For example, the heating temperature in the heat press can be appropriately set within the range of 150°C or more and 200°C or less. The pressure in the heat press can be appropriately set within the range of 1 MPa or more and 3 MPa or less. The pressing time in the heat press can be appropriately set within the range of 1 minute or more and 60 minutes or less.

Furthermore, after the heat pressing, the laminate can be heated as necessary to perform an after-cure, thereby further hardening the adhesive layer. The heating temperature during the after-cure can be appropriately set, for example, within the range of 100°C or more and 200°C or less. The heating time during the after-cure can be appropriately set, for example, within the range of 30 minutes or more and 4 hours or less.

An example of the adhesive composition is described below. In this example, the adhesive composition was made using the following raw materials.

(Base resin (A))
In this example, polyamide a1, polyester polyamide a2, polyester polyurethane a3, a4, and polyurethane a5, a6 were used as the base resin (A). The preparation method of these is as follows.

[Polyamide a1]
In a flask equipped with a stirrer, a reflux dehydration device and a distillation tube, 485 parts by mass of dimer acid, 100 parts by mass of hexamethylenediamine and 120 parts by mass of distilled water were placed. The flask was heated to raise the temperature of the contents to 120°C to distill off water. The temperature of the contents was then raised to 240°C at a heating rate of 20°C/hour. This temperature was maintained for 3 hours to continue the reaction, thereby obtaining pellet-shaped polyamide a1. The amine value of polyamide a1 was 4.5 mgKOH/g. The amine value of polyamide was measured and calculated by potentiometric measurement in accordance with JIS K 7237 (1995).

[Polyester polyamide a2]
In a flask equipped with a stirrer, a reflux dehydration device, and a distillation tube, 7 parts by mass of dimer acid, 406 parts by mass of azelaic acid, 364 parts by mass of isophorone diamine, and 120 parts by mass of distilled water were placed. The flask was heated to raise the temperature of the contents to 120°C to distill off water. The flask was then further heated to raise the temperature of the contents to 240°C at a heating rate of 20°C/hour. After maintaining this temperature for 1 hour, 200 parts by mass of azelaic acid, 125 parts by mass of neopentyl glycol, and 2.1 parts by mass of tetrabutoxy titanate as an esterification catalyst were added to the reaction product in the flask. The temperature of the contents of the flask was lowered to 150°C by adding these raw materials.

The flask was then heated again to raise the temperature of the contents to 220°C. This temperature was maintained and the reaction continued until the amine value reached 7.6 mgKOH/g. As a result, polyester polyamide a2 in pellet form was obtained. The acid value of polyester polyamide a2 was 1.3 mgKOH/g. The acid value of the resin in this example was measured and calculated by potentiometric titration in accordance with JIS K 2501 (2003).

[Polyester polyurethane a3]
Into a flask equipped with a stirrer, a reflux dehydration apparatus, and a distillation tube, 600 parts by mass of a polyester adhesive ("PES-360HVXM30" manufactured by Toagosei Co., Ltd.), 100 parts by mass of toluene, and 20 parts by mass of neopentyl glycol were placed. The flask was heated to raise the temperature of the contents to 120°C, and 100 parts by mass of the solvent containing water were distilled off, and then the temperature of the contents was lowered to 105°C. Thereafter, 0.4 parts by mass of 2,2-dimethylolpropionic acid was added to the flask and dissolved in the contents.

Next, 34 parts by mass of hexamethylene diisocyanate was added to the flask. 30 minutes after the addition of hexamethylene diisocyanate, 0.2 parts by mass of dibutyltin dilaurate was added to the flask, and the reaction was continued for 6 hours. The contents of the flask were then diluted with toluene and 2-propanol to adjust the solids concentration to 30% by mass. As a result, a solution containing polyester polyurethane a3 was obtained. The number average molecular weight of polyester polyurethane a3 was 36,000, and the acid value was 2 mgKOH/g.

[Polyester polyurethane a4]
In a flask equipped with a stirrer, a reflux dehydration device, and a distillation tube, 600 parts by mass of a polyester adhesive ("PES-360HVXM30" manufactured by Toagosei Co., Ltd.), 100 parts by mass of toluene, and 30 parts by mass of 2-butyl-2-ethyl-1,3-propanediol were placed. The flask was heated to raise the temperature of the contents to 120°C, and 100 parts by mass of the solvent containing water were distilled off, and then the temperature of the contents was lowered to 105°C. Thereafter, 0.4 parts by mass of 2,2-bis(hydroxymethyl)propionic acid was added to the flask and dissolved in the contents.

Next, 42 parts by mass of norbornane diisocyanate ("Cosmonate (registered trademark) NBDI (registered trademark)" manufactured by Mitsui Chemicals, Inc.) was added to the flask, and 30 minutes after the addition of norbornane diisocyanate, 0.2 parts by mass of dibutyltin dilaurate was added to the flask. The reaction was then continued until a predetermined molecular weight was reached, and the contents of the flask were then diluted with toluene and 2-propanol to adjust the solids concentration to 30% by mass. As a result, a solution containing polyester polyurethane a4 was obtained. The number average molecular weight of polyester polyurethane a4 was 35,000, and the acid value was 2 mgKOH/g.

[Polyurethane a5]
Into a flask equipped with a stirrer, a reflux dehydration apparatus, and a distillation tube, 100 parts by mass of polyphenylene ether diol ("Noryl SA90" manufactured by SABIC), 8 parts by mass of 2-butyl-2-ethyl-1,3-propanediol, and 230 parts by mass of toluene were placed. The flask was heated to raise the temperature of the contents to 120°C, and 100 parts by mass of the solvent containing water was distilled off, and then the temperature of the contents was lowered to 105°C. Thereafter, 0.8 parts by mass of 2,2-bis(hydroxymethyl)propionic acid was added to the flask and dissolved in the contents.

Next, 22 parts by mass of 1,3-bis(isocyanatomethyl)cyclohexane were added to the flask. 30 minutes after the addition of 1,3-bis(isocyanatomethyl)cyclohexane, 0.1 parts by mass of dibutyltin dilaurate was added to the flask, and the reaction was continued for 12 hours. The contents of the flask were then diluted with a mixed solvent of 30 parts by mass of toluene, 30 parts by mass of methyl ethyl ketone, and 15 parts by mass of 2-propanol. As a result, a solution containing polyurethane a5 was obtained. Polyurethane a5 had a weight average molecular weight of 77,000, a number average molecular weight of 13,000, and an acid value of 2.6 mgKOH/g.

[Polyurethane a6]
Into a flask equipped with a stirrer, a reflux dehydration apparatus, and a distillation tube, 90 parts by mass of polyphenylene ether diol ("Noryl SA90" manufactured by SABIC), 10 parts by mass of polycarbonate diol ("ETERNACOLL (registered trademark) UH-100" manufactured by UBE Corporation), 8 parts by mass of 2-butyl-2-ethyl-1,3-propanediol, and 230 parts by mass of toluene were placed. The flask was heated to increase the temperature of the contents to 120°C, and 100 parts by mass of the solvent containing water was distilled off, and then the temperature of the contents was lowered to 105°C. Thereafter, 0.8 parts by mass of 2,2-bis(hydroxymethyl)propionic acid was added to the flask and dissolved in the contents.

Next, 22 parts by mass of 1,3-bis(isocyanatomethyl)cyclohexane were added to the flask. 30 minutes after the addition of 1,3-bis(isocyanatomethyl)cyclohexane, 0.1 parts by mass of dibutyltin dilaurate was added to the flask, and the reaction was continued for 12 hours. The contents of the flask were then diluted with a mixed solvent of 30 parts by mass of toluene, 30 parts by mass of methyl ethyl ketone, and 15 parts by mass of 2-propanol. In this way, polyurethane a6 was obtained. The weight average molecular weight of polyurethane a6 was 83,000, the number average molecular weight was 11,000, and the acid value was 2.6 mgKOH/g.

(Epoxy compound (B))
The epoxy compound (B) used in this example is as follows.
Epoxy compound b1: Trisphenolmethane type epoxy resin ("jER (registered trademark) 1032H60" manufactured by Mitsubishi Chemical Corporation)
Epoxy compound b2: bisphenol A novolac type epoxy resin ("EPICLON (registered trademark) N-865" manufactured by DIC Corporation)
Epoxy compound b3: bisphenol A type epoxy resin ("jER 1055" manufactured by Mitsubishi Chemical Corporation)
Epoxy compound b4: Cresol novolac type epoxy resin ("EPICLON N-665-EXP" manufactured by DIC Corporation)

(Triazine Compound (C))
The triazine-based compound (C) used in this example is as follows.
Triazine compound c1: Melamine-melam-melem polyphosphate double salt ("PHOSMEL (registered trademark)-200" manufactured by Nissan Chemical Industries, Ltd.)
Triazine-based compound c2: Melamine polyphosphate ("MPP-A" manufactured by Sanwa Chemical Co., Ltd.)
Triazine compound c3: Melamine cyanurate ("MC-6000" manufactured by Nissan Chemical Industries, Ltd.)

Triazine-based compound C4: Melamine Triazine-based compound C5: Cyanuric acid Triazine-based compound C6: Acetoguanamine Triazine-based compound C7: Benzoguanamine Triazine-based compound C8: Trithiocyanuric acid

The median diameter on a volume basis of the triazine compound (C) used in this example is as shown in Tables 1 and 2.

(Metal Phosphinate (D))
The metal phosphinate (D) used in this example is as follows:
Phosphinic acid metal salt d1: "Exolit OP935" manufactured by Clariant

(Other compounds)
Phosphazene: "SPB-100" manufactured by Otsuka Chemical Co., Ltd.

(Examples 1 to 21 and Comparative Examples 1 to 4)
The above raw materials were added to a flask equipped with a stirrer in the ratios shown in Tables 1 and 2, and a mixed solvent of toluene, methyl ethyl ketone, and isopropanol was added to the flask so that the solid content of the contents was about 20 mass%. The blending amount of the base resin (A) in Tables 1 and 2 is the solid content, that is, the amount of the base resin (A) excluding the solvent. The ratio of toluene, methyl ethyl ketone, and isopropanol in the mixed solvent was appropriately adjusted depending on the solubility of the base resin (A).

Then, the flask was heated to raise the temperature of the contents to 60°C. The contents of the flask were stirred for 6 hours while maintaining the temperature, to disperse the base resin (A) and the epoxy compound (B) in the solvent, as well as the triazine compound (C) and the metal phosphinate (D). In this way, a liquid adhesive composition was prepared. In Tables 1 and 2, the "Phosphorus Atom Content" column shows the solid content of the adhesive composition, that is, the ratio of the mass of phosphorus atoms contained in the adhesive composition to the total amount of the base resin (A), the epoxy compound (B), the triazine compound (C), the metal phosphinate (D), and the phosphazene (unit: mass%).

Next, using the adhesive compositions of the examples and comparative examples, a test piece A for evaluating flame retardancy (hereinafter referred to as "test piece A"), a bonding film B, and a test piece C for evaluating adhesion (hereinafter referred to as "test piece C") were prepared by the following method.

[Flame retardancy evaluation test piece A]
1, the test piece A for evaluating flame retardancy has a cured material layer 1 made of a cured product of an adhesive composition, and polyimide films 2 (2a, 2b) laminated on both sides of the cured material layer 1. The cured material layer 1 has a thickness of 15 μm, and the polyimide film 2 has a thickness of 25 μm.

The method for preparing test piece A is as follows. First, the adhesive composition was applied to the surface of the first polyimide film 2a of the two polyimide films 2 using a roll coater. The adhesive composition on the polyimide film 2a was then dried for 3 minutes in an oven set at a temperature of 100°C, producing a coverlay film having a polyimide film 2a and an adhesive layer laminated on the polyimide film 2a.

Next, a second polyimide film 2b was superimposed on the adhesive layer of the coverlay film, and a thermal lamination process was performed. The heating temperature in the thermal lamination process was 120°C, the pressure was 0.4 MPa, and the lamination speed was 0.5 m/min. The laminate of the coverlay film and polyimide film 2b was then subjected to a heat press process under conditions of a temperature of 170°C, a pressure of 3 MPa, and a heating time of 30 minutes, thereby hardening the adhesive layer to form a cured layer 1 and bonding the cured layer 1 to the polyimide film 2b. The laminate thus obtained was cut to a specified size to obtain test piece A.

[Bonding film B]
As shown in Fig. 2, the bonding film B has a release film 3 and an adhesive layer 10 provided on the release film 3. The release film 3 is made of polyethylene terephthalate. The release film 3 has a thickness of 35 µm. The adhesive layer 10 has a thickness of 25 µm. The adhesive layer 10 is made of an adhesive composition 100 or a semi-cured product thereof.

Bonding film B is obtained by applying the adhesive composition onto release film 3 with a roll coater and then drying it at 100°C for 3 minutes.

[Test piece C for evaluating adhesion]
As shown in FIG. 3, the adhesiveness evaluation test piece C has a copper-clad laminate 4 consisting of a polyimide film 41 and a copper foil 42 laminated on the polyimide film 41, a cured product layer 1 provided on the polyimide film 41 of the copper-clad laminate 4, and a copper foil 5 provided on the cured product layer 1. The polyimide film 41 and the copper foil 5 of the copper-clad laminate 4 are bonded via the cured product layer 1. The thickness of the polyimide film 41 constituting the copper-clad laminate 4 is 25 μm, and the thickness of the copper foil 42 is 18 μm. The thickness of the cured product layer 1 is 15 μm. A rolled copper foil having a thickness of 35 μm was used as the copper foil 5.

The method for preparing test piece C is as follows. First, the adhesive composition was applied to the polyimide film 41 of the copper-clad laminate 4 using a roll coater. The adhesive composition on the copper-clad laminate 4 was then dried for 3 minutes in an oven set at a temperature of 100°C, forming an adhesive layer on the polyimide film 41.

Then, copper foil 5 was superimposed on the adhesive layer and subjected to a thermal lamination process. The heating temperature in the thermal lamination process was 120°C, the pressure was 0.4 MPa, and the lamination speed was 0.5 m/min. The laminate of the copper-clad laminate 4, the adhesive layer, and the copper foil 5 was then subjected to a thermal press process under conditions of a temperature of 170°C, a pressure of 3 MPa, and a heating time of 30 minutes, thereby hardening the adhesive layer to form a hardened layer 1 and bonding the hardened layer 1 to the copper foil 5. The flexible copper-clad laminate thus obtained was cut to a specified size to obtain test piece C.

The test pieces A and C obtained in the above manner were used to evaluate the various properties shown in Tables 1 and 2. The evaluation methods for each property were as follows.

(peel adhesion strength)
The peel adhesion strength was measured using the test piece C shown in FIG. 3. The peel adhesion strength was measured in accordance with JIS C 6481 "Test method for copper-clad laminates for printed wiring boards". In this example, the peel adhesion strength of the test piece C in the initial state was measured. More specifically, in the measurement of the peel adhesion strength in the initial state, the test piece C prepared by the above-mentioned method was used, and the 180° peel adhesion strength (unit: N/cm) when the copper foil 5 was peeled off from the copper-clad laminate 4 was measured. The temperature during the measurement was 23° C., and the pulling speed was 50 mm/min. The peel adhesion strength of the test piece C in the initial state was as shown in Tables 1 and 2.

(heat resistance)
The heat resistance was evaluated based on the peel adhesive strength after preparing test pieces C with different moisture absorption states and heating these test pieces. Specifically, test pieces C in the initial state were prepared as test pieces C in a state in which moisture was not absorbed. In addition, two types of test pieces were prepared as test pieces in a moisture-absorbed state: test piece C that was stored in a thermo-hygrostat chamber at a temperature of 40° C. and a relative humidity of 90% RH for 24 hours to absorb moisture, and test piece C that was stored in a thermo-hygrostat chamber at a temperature of 40° C. and a relative humidity of 90% RH for 72 hours to absorb moisture.

These three types of test specimens C were heated for 10 minutes in a drying oven at 260°C. After heating was completed, the peel adhesion strength of the test specimens C taken out of the oven was measured using the same method as that for measuring the peel adhesion strength of the initial test specimens C. Then, using the peel adhesion strength of the initial test specimens C and the peel adhesion strength of the test specimens C after heating, the peel adhesion strength retention rates after heating were calculated for the initial test specimens C, the test specimens C after absorbing moisture for 24 hours, and the test specimens C after absorbing moisture for 72 hours. Specifically, the peel adhesion strength retention rate after heating is the ratio, expressed as a percentage, of the peel adhesion strength of the test specimens C after heating to the peel adhesion strength of the initial test specimens C.

In the "Heat resistance" columns of Tables 1 and 2, the symbol "A" is entered if the peel adhesion strength retention rate of each test piece C was 80% or more, the symbol "B" is entered if it was 60% or more but less than 80%, the symbol "C" is entered if it was 30% or more but less than 60%, and the symbol "D" is entered if it was less than 30%.

(Flame retardant)
Test piece A shown in Figure 1 was used to evaluate flame retardancy according to a method in accordance with UL 94. In the "Flame Retardancy" column of Tables 1 and 2, "Good" is entered when the flame retardancy based on UL 94 was judged to be VTM-0, and "Poor" is entered when it was judged to be VTM-1 or less.

As shown in Tables 1 and 2, the adhesive compositions of Examples 1 to 21 contain the base resin (A), epoxy compound (B), triazine compound (C), and metal phosphinate (D) in the specific ratios described above. Therefore, the cured products of these adhesive compositions exhibit high heat resistance even when humidified, and were able to suppress a decrease in peel adhesive strength even when heated after humidifying for 24 hours or after humidifying for 72 hours.

Furthermore, among Examples 1 to 21, when comparing Examples 8 to 21, which have roughly the same composition except that the base resin (A) is polyamide a2 and the type of triazine-based compound (C) is different, the peel adhesion strength retention rate after 24 hours of moisture absorption in Examples 8 to 14 is higher than that of Examples 15 to 21. From these comparisons, it can be seen that by using a triazine-based compound (C) that contains melamine in its molecular structure and has a median diameter of 10 μm or less, the heat resistance of the cured material in a moisture-absorbed state can be further improved.

In contrast, the adhesive composition of Comparative Example 1 does not contain the triazine compound (C) or the metal phosphinate (D). Therefore, the cured product of the adhesive composition of Comparative Example 1 has poor heat resistance after moisture absorption, and the peel bond strength retention rate after 24 hours and 72 hours of moisture absorption is low.

The content of the triazine compound (C) in the adhesive composition of Comparative Example 2 is less than the specific range. In addition, the adhesive composition of Comparative Example 2 does not contain a metal phosphinate (D). Therefore, the cured product of the adhesive composition of Comparative Example 2 has poor heat resistance after moisture absorption, and has low peel adhesion strength retention after moisture absorption for 24 hours and 72 hours.

In the adhesive composition of Comparative Example 3, although the metal phosphinate (D) is contained, the content of the triazine compound (C) is less than the specific range. Therefore, the cured product of the adhesive composition of Comparative Example 3 has poor heat resistance after moisture absorption, and the peel bond strength retention rate after 24 hours and 72 hours of moisture absorption is low.

The adhesive composition of Comparative Example 4 contains phosphazene instead of metal phosphinate (D). Therefore, the cured product of the adhesive composition of Comparative Example 4 has excellent flame retardancy but poor heat resistance after moisture absorption, and the peel bond strength retention rate after moisture absorption for 24 hours and 72 hours is low.

　The above describes the adhesive composition, bonding film, laminate with adhesive layer, and laminate based on the examples, but the specific aspects of the adhesive composition etc. according to the present invention are not limited to those in the examples, and the configuration can be changed as appropriate within the scope of the spirit of the present invention.

Claims (9)

A base resin (A) containing at least one resin selected from the group consisting of polyamide-based resins and polyurethane-based resins;
an epoxy compound (B) of 1 part by mass or more and 50 parts by mass or less per 100 parts by mass of the base resin (A);
a triazine-based compound (C) of 10 parts by mass or more and 70 parts by mass or less per 100 parts by mass of the base resin (A);
and 0.5 parts by mass or more and 50 parts by mass or less of a metal phosphinate (D) relative to 100 parts by mass of the base resin (A),
The adhesive composition, wherein the triazine compound (C) contains, in its molecular structure, one or more structures selected from a structure represented by the following general formula (C1) and a structure represented by the following structural formula (C2):

(In the above general formula (C1), R ¹ to R ³ each independently represent an amino group, a hydroxyl group, a thiol group, a methyl group, or a phenyl group.)

The adhesive composition according to claim 1 , wherein the triazine compound (C) contains a structure represented by the following structural formula (C3) in its molecular structure.

The adhesive composition according to claim 1, wherein the triazine compound (C) has a volumetric median diameter of 10 μm or less. The adhesive composition according to claim 1, wherein the base resin (A) contains a polyester polyamide as a polyamide-based resin. The adhesive composition according to claim 1, wherein the base resin (A) contains a polyester polyurethane as a polyurethane-based resin. The adhesive composition according to claim 1, wherein the base resin (A) comprises a polyurethane resin having a polyphenylene ether skeleton containing a plurality of phenylene groups and ether bonds connecting the phenylene groups together. An adhesive layer;
A release film provided on one or both sides of the adhesive layer and configured to be peelable from the adhesive layer,
A bonding film, wherein the adhesive layer is composed of the adhesive composition according to any one of claims 1 to 6 or a semi-cured product obtained by partially curing the adhesive composition. An adhesive layer;
A substrate layer adhered to at least one surface of the adhesive layer,
A laminate with an adhesive layer, wherein the adhesive layer is composed of the adhesive composition according to any one of claims 1 to 6 or a semi-cured product obtained by partially curing the adhesive composition. A laminate comprising a cured layer made of the cured product of the adhesive composition according to any one of claims 1 to 6.

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