JP7707914B2 - Polyolefin-based adhesive composition - Google Patents

Description

The present invention relates to a polyolefin-based adhesive composition. More specifically, the present invention relates to a polyolefin-based adhesive composition used for bonding a resin substrate to a resin substrate or a metal substrate. In particular, the present invention relates to an adhesive composition for flexible printed wiring boards (hereinafter abbreviated as FPC), and a cover film, a laminate, a resin-coated copper foil, and a bonding sheet each containing the same.

Flexible printed circuit boards (FPCs) have excellent flexibility and can accommodate the multi-functionality and miniaturization of personal computers (PCs) and smartphones, and are therefore often used to incorporate electronic circuit boards into narrow and complex interiors. In recent years, electronic devices have become smaller, lighter, more dense, and more powerful, and these trends have led to increasingly higher requirements for the performance of wiring boards (electronic circuit boards). In particular, with the increase in the speed of transmission signals in FPCs, signals are becoming increasingly high frequency. Accordingly, there is an increasing demand for low dielectric properties (low dielectric constant, low dielectric tangent) in the high frequency range for FPCs. In order to achieve such low dielectric properties, measures have been taken to reduce the dielectric loss of FPC substrates and adhesives. As adhesives, a combination of acid-modified polyolefin and epoxy resin (Patent Document 1), a combination of acid-modified polyolefin and polyfunctional isocyanate compound (Patent Document 2), and a thermosetting adhesive composition containing acid-modified polyolefin, carbodiimide resin, polyfunctional epoxy resin, and filler have been developed (Patent Document 3).

WO2016/047289 publication WO2015/046378 publication JP 2019-127501 A

However, it has been found that although polyolefins modified with maleic anhydride have carboxylic anhydride groups immediately after production, they have a problem in that they absorb moisture over time, causing the carboxylic anhydride rings to open. Therefore, as in Patent Documents 1 to 3, if they are used without taking any measures against moisture absorption, it has been found that their adhesiveness, solder heat resistance, dielectric properties (relative dielectric constant, dielectric loss tangent) and pot life are insufficient.

As a result of extensive investigations aimed at solving the above-mentioned problems, the present invention has discovered that an adhesive composition comprising an acid-modified polyolefin having a predetermined ratio of carboxylic acid anhydride groups, and further containing one or more compounds selected from the group consisting of an epoxy resin, an isocyanate compound, and a carbodiimide compound, exhibits excellent adhesion between a resin substrate and a metal substrate, solder heat resistance, and low dielectric properties (dielectric constant, dielectric tangent), and further has excellent pot life after blending with a curing agent, which has led to the completion of the present invention.

That is, an object of the present invention is to provide an adhesive composition that has good adhesion to both various resin substrates, such as not only polyimide (PI) but also liquid crystal polymer (LCP), and metal substrates, and that also has excellent solder heat resistance, dielectric properties, and pot life.

The adhesive composition contains an acid-modified polyolefin (A) that satisfies the following (1) to (3), and further contains one or more compounds selected from the group consisting of an epoxy resin (B1), an isocyanate compound (B2), and a carbodiimide compound (B3).
(1) The acid value is 5 to 50 mgKOH/g. (2) The bonding ratio (molar ratio) of the carboxylic anhydride group represented by formula (a1) to the carboxylic acid group represented by formula (a2) is formula (a1)/formula (a2)=100/0 to 50/50. (3) When the total acid component bonded to the acid-modified polyolefin (A) is taken as 100 mol %, the total amount of the formulas (a1) and (a2) is 90 mol % or more.
[In formula (a1) and formula (a2), * represents a bond bonded to the acid-modified polyolefin (A).]

The epoxy resin (B1) is preferably a mixture containing a glycidylamine type epoxy resin (B11) and further containing at least one selected from the group consisting of a glycidyl ether type resin (B12) and an alicyclic type epoxy resin (B13).

The isocyanate compound (B2) is preferably a polyfunctional isocyanate compound.

The carbodiimide compound (B3) is preferably a polyfunctional carbodiimide compound.

It is preferable that the composition further contains an oligophenylene ether (C), and it is preferable that the composition further contains an organic solvent.

An adhesive composition having a relative dielectric constant (ε _c ) of 3.0 or less and a dielectric loss tangent (tan δ) of 0.02 or less at 1 GHz. An adhesive sheet or laminate containing said adhesive composition. A printed wiring board including said laminate as a component. A cover film including said printed wiring board as a component.

The adhesive composition of the present invention has good adhesion to both metal substrates and various resin substrates, such as not only polyimide but also liquid crystal polymers, and is excellent in solder heat resistance, low dielectric properties, and pot life.

<Acid-modified polyolefin (A)>
The acid-modified polyolefin (A) (hereinafter, also simply referred to as component (A)) used in the present invention satisfies the following requirements (1) to (3).

<Requirement (1)>
The acid value of the acid-modified polyolefin (A) must be 5 mgKOH/g or more in terms of solder heat resistance and adhesion to resin substrates and metal substrates. The acid value is preferably 6 mgKOH/g or more, more preferably 7 mgKOH/g or more, and even more preferably 8 mgKOH/g or more, because the compatibility with the epoxy resin (B1), the isocyanate compound (B2) and the carbodiimide compound (B3) is good, excellent adhesive strength can be expressed, and the crosslinking density is high and solder heat resistance is good. The acid value must be 50 mgKOH/g or more in the upper limit. The acid value is preferably 40 mgKOH/g or less, more preferably 30 mgKOH/g or less, and even more preferably 20 mgKOH/g or less, because the adhesiveness and solder heat resistance are good, and the viscosity and stability of the solution are good, and excellent pot life can be expressed. If it is within the above range, the production efficiency is also improved.

<Requirement (2)>
The bonding ratio (molar ratio) of the carboxylic anhydride group represented by formula (a1) to the carboxylic acid group represented by formula (a2) must be (a1)/(a2)=100/0 to 50/50.
[In formula (a1) and formula (a2), * represents a bond bonded to the acid-modified polyolefin (A).]

In order to improve adhesion, solder heat resistance, and pot life, it is preferable that formula (a1) is in excess over formula (a2). Formula (a1)/formula (a2)=less than 100/more than 0 to more than 50/less than 50 is preferable, more preferably 99/1 to 55/45, even more preferably 97/3 to 60/40, still more preferably 95/5 to 65/35, particularly preferably 93/7 to 70/30, and most preferably 91/9 to 75/25.

Although the acid-modified polyolefin (A) has a carboxylic anhydride group, it gradually absorbs moisture during the production, packaging and storage of the acid-modified polyolefin, and the carboxylic anhydride group is opened to form a carboxylic acid group. Therefore, in order to make the bond ratio of the carboxylic anhydride group represented by formula (a1) and the carboxylic acid group represented by formula (a2) within the above range, it is preferable to perform a dehydration condensation reaction in an organic solvent such as toluene again after the production of the acid-modified polyolefin (A), or to perform dehydration condensation at high temperature without a solvent.

The bond ratio (molar ratio) of formula (a1)/formula (a2) can be measured by IR. Specifically, a calibration curve is prepared using maleic anhydride (hereinafter also referred to as maleic anhydride) as a standard substance, and the bond ratio can be determined from the absorbance of the carbonyl (C═O) bond (near 1780 cm ⁻¹ ) derived from the carboxylic anhydride group and the absorbance of the carbonyl (C═O) bond (near 1730 cm ⁻¹ ) derived from the carboxylic acid group.

<Requirement (3)>
When the total acid component bonded to the acid-modified polyolefin (A) is taken as 100 mol%, the total amount of formula (1) and formula (2) must be 90 mol% or more. In order to improve the adhesiveness, solder heat resistance and pot life, it is preferably 92 mol% or more, more preferably 95 mol% or more, even more preferably 98 mol% or more, and particularly preferably 99 mol% or more, and it may be 100 mol%.

The acid-modified polyolefin (A) is preferably one obtained by grafting at least one of maleic acid and maleic anhydride to a polyolefin resin. The polyolefin resin refers to a polymer mainly composed of a hydrocarbon skeleton, such as a homopolymer of an olefin monomer exemplified by ethylene, propylene, butene, butadiene, isoprene, etc., or a copolymer with other monomers, and a hydrogenated or halogenated product of the obtained polymer. That is, the acid-modified polyolefin is preferably one obtained by grafting at least one of maleic acid and maleic anhydride to at least one of polyethylene, polypropylene, and propylene-α-olefin copolymer.

A propylene-α-olefin copolymer is a copolymer of propylene as a main component with an α-olefin. As the α-olefin, for example, one or more of ethylene, 1-butene, 1-heptene, 1-octene, 4-methyl-1-pentene, vinyl acetate, etc. can be used. Among these α-olefins, ethylene and 1-butene are preferred, and 1-butene is more preferred. The ratio of the propylene component to the α-olefin component in the propylene-α-olefin copolymer is not limited, but the propylene component is preferably 50 mol % or more, and more preferably 70 mol % or more.

Examples of the carboxylic acid component other than maleic acid and maleic anhydride include itaconic acid, citraconic acid and their acid anhydrides, acrylic acid, methacrylic acid, etc. Specific examples of the acid-modified polyolefin (A) include maleic anhydride-modified polypropylene, maleic anhydride-modified propylene-ethylene copolymer, maleic anhydride-modified propylene-butene copolymer, maleic anhydride-modified propylene-ethylene-butene copolymer, etc., and these acid-modified polyolefins can be used alone or in combination of two or more. Among them, maleic anhydride-modified propylene-butene copolymer is preferred.

The number average molecular weight (Mn) of the acid-modified polyolefin (A) is preferably in the range of 10,000 to 50,000. More preferably, it is in the range of 15,000 to 45,000, even more preferably in the range of 20,000 to 40,000, and particularly preferably in the range of 22,000 to 38,000. By making it equal to or greater than the lower limit, the cohesive force is good and excellent adhesiveness can be exhibited. In addition, by making it equal to or less than the upper limit, excellent flowability and operability can be obtained.

The weight average molecular weight (Mw) of the acid-modified polyolefin (A) is preferably in the range of 40,000 to 180,000. More preferably, it is in the range of 50,000 to 160,000, even more preferably in the range of 60,000 to 150,000, particularly preferably in the range of 70,000 to 140,000, and most preferably in the range of 80,000 to 130,000. By making it equal to or greater than the lower limit, the cohesive force is improved and excellent adhesiveness can be exhibited. In addition, by making it equal to or less than the upper limit, excellent flowability and operability are achieved.

The acid-modified polyolefin (A) is preferably a crystalline acid-modified polyolefin. The term "crystalline" as used herein refers to a polyolefin that shows a clear melting peak during heating from -100°C to 250°C at a rate of 20°C/min using a differential scanning calorimeter (DSC).

The melting point (Tm) of the acid-modified polyolefin (A) is preferably in the range of 50°C to 120°C. More preferably, it is in the range of 60°C to 100°C, and most preferably, it is in the range of 70°C to 90°C. By making it equal to or higher than the lower limit, the cohesive force derived from crystals becomes good, and excellent adhesiveness and solder heat resistance can be exhibited. In addition, by making it equal to or lower than the upper limit, excellent solution stability and flowability are obtained, and operability during adhesion is good.

The heat of fusion (ΔH) of the acid-modified polyolefin (A) is preferably in the range of 5 J/g to 60 J/g. More preferably, it is in the range of 10 J/g to 50 J/g, and even more preferably, it is in the range of 20 J/g to 40 J/g. By making it equal to or greater than the lower limit, the cohesive force derived from crystals becomes good, and excellent adhesiveness and solder heat resistance can be exhibited. In addition, by making it equal to or less than the upper limit, excellent solution stability and flowability are obtained, and operability during adhesion is good.

The method for producing the acid-modified polyolefin (A) is not particularly limited, and examples thereof include a radical graft reaction (i.e., a reaction in which radical species are generated on a polymer that becomes a main chain, and an unsaturated carboxylic acid and an acid anhydride are graft polymerized using the radical species as a polymerization initiation point).

The radical generator is not particularly limited, but it is preferable to use an organic peroxide. Examples of the organic peroxide include, but are not particularly limited to, peroxides such as di-tert-butyl peroxyphthalate, tert-butyl hydroperoxide, dicumyl peroxide, benzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxypivalate, methyl ethyl ketone peroxide, di-tert-butyl peroxide, and lauroyl peroxide; and azonitriles such as azobisisobutyronitrile and azobisisopropionitrile.

<Epoxy resin (B1)>
The epoxy resin (B1) (hereinafter, also simply referred to as component (B1)) used in the present invention is not particularly limited as long as it has a glycidyl group in the molecule, but preferably has two or more glycidyl groups in the molecule.

The content of the epoxy resin (B1) is preferably 0.5 parts by mass or more relative to 100 parts by mass of the acid-modified polyolefin (A). Since a sufficient curing effect can be obtained and excellent adhesiveness and solder heat resistance can be expressed, it is more preferably 1 part by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 10 parts by mass or more. In addition to adhesiveness, solder heat resistance and pot life, it has excellent low dielectric properties, so it is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 40 parts by mass or less, and particularly preferably 35 parts by mass or less.

The epoxy equivalent of the epoxy resin (B1) is preferably 50 g/eq or more, more preferably 100 g/eq or more, and even more preferably 150 g/eq or more. Also, it is preferably 400 g/eq or less, more preferably 350 g/eq or less, and even more preferably 300 g/eq or less. By setting it within the above range, excellent solder heat resistance can be exhibited.

From the viewpoints of adhesiveness and solder heat resistance, the epoxy resin (B1) used in the present invention is preferably a mixture of one or more selected from the group consisting of a glycidylamine type epoxy resin (B11) and a glycidyl ether type resin (B12) and an alicyclic type epoxy resin (B13). That is, it is preferably a mixture of (B11) and (B12), a mixture of (B11) and (B13), or a mixture of (B11), (B12) and (B13).

<Glycidylamine-type epoxy resin (B11)>
The glycidylamine type epoxy resin (B11) is not particularly limited as long as it is an amine type epoxy resin having one or more glycidyl groups per molecule. It is preferable that the epoxy resin has two or more glycidyl groups per molecule, more preferably three or more glycidyl groups per molecule, and even more preferably four or more glycidyl groups per molecule.

In addition, the glycidylamine type epoxy resin (B11) is preferably one that contains a compound represented by the following general formula (b1), since the adhesiveness can be further improved by using the compound represented by the following general formula (b1).
In the general formula (b1), R is an aryl group which may have a substituent, preferably a phenyl group which may have a substituent. The substituent of the aryl group is not particularly limited, but may include an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a hydroxyl group, an amino group, a glycidyl group, a glycidylamino group, or a glycidyl ether group. X1 and X2 are each independently a linear alkylene group which may have a substituent having 1 to 5 carbon atoms, and preferably has 4 or less carbon atoms, more preferably 3 or less, and even more preferably 2 or less. The substituent of the alkylene group is not particularly limited, but may include an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, or an amino group. m is 1 or 2, and n is 1 or 2. Preferably, either m or n is 2, and more preferably, both m and n are 2.

Specific examples of the glycidylamine type epoxy resin (B11) include, but are not limited to, glycidylamines such as tetraglycidyldiaminodiphenylmethane, triglycidyl paraaminophenol, tetraglycidylbisaminomethylcyclohexanone, and N,N,N',N'-tetraglycidyl-m-xylylenediamine. Among these, N,N,N',N'-tetraglycidyl-m-xylylenediamine is preferred. These glycidylamine type epoxy resins (B11) can be used alone or in combination of two or more.

The amount of the glycidylamine type epoxy resin (B11) is preferably 0.01 parts by mass or more, more preferably 0.03 parts by mass or more, even more preferably 0.05 parts by mass or more, particularly preferably 0.08 parts by mass or more, and most preferably 0.1 parts by mass or more, relative to 100 parts by mass of the acid-modified polyolefin (A), because the catalytic action is expressed and the adhesiveness and solder heat resistance are good. Also, because the pot life is good, the amount is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 40 parts by mass or less, even more preferably 30 parts by mass or less, particularly preferably 20 parts by mass or less, and most preferably 15 parts by mass or less.

<Glycidyl ether type epoxy resin (B12)>
The glycidyl ether type epoxy resin (B12) is not particularly limited as long as it is an epoxy resin having a glycidyl ether group in the molecule. It is preferably an epoxy resin having two or more glycidyl groups in one epoxy resin molecule, and more preferably an epoxy resin having two or more glycidyl groups in one epoxy resin molecule and not containing a nitrogen atom.

The amount of the glycidyl ether type epoxy resin (B12) is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, particularly preferably 4 parts by mass or more, and most preferably 5 parts by mass or more, relative to 100 parts by mass of the acid-modified polyolefin (A). Also, it is preferably 20 parts by mass or less, more preferably 18 parts by mass or less, even more preferably 16 parts by mass or less, particularly preferably 14 parts by mass or less, and most preferably 12 parts by mass or less. By setting it in the above range, excellent adhesiveness and solder heat resistance can be exhibited.

Specific examples of the glycidyl ether type epoxy resin (B12) include, but are not limited to, phenol novolac type epoxy resin and cresol novolac type epoxy resin, which are preferred from the viewpoint of adhesion to metal substrates. These glycidyl ether type epoxy resins (B12) can be used alone or in combination of two or more kinds.

<Alicyclic epoxy resin (B13)>
The alicyclic epoxy resin (B13) is not particularly limited as long as it is an epoxy resin having an alicyclic skeleton in the molecule. It is preferably an alicyclic epoxy resin having two or more glycidyl groups in one epoxy resin molecule, and more preferably an alicyclic epoxy resin having two or more glycidyl groups in one epoxy resin molecule.

The amount of the alicyclic epoxy resin (B13) is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, particularly preferably 4 parts by mass or more, and most preferably 5 parts by mass or more, relative to 100 parts by mass of the acid-modified polyolefin (A). Also, it is preferably 20 parts by mass or less, more preferably 18 parts by mass or less, even more preferably 16 parts by mass or less, particularly preferably 14 parts by mass or less, and most preferably 12 parts by mass or less. By setting it in the above range, excellent adhesiveness and solder heat resistance can be exhibited.

Specific examples of the alicyclic epoxy resin (B13) include, but are not limited to, dicyclopentadiene skeleton-containing epoxy resins, hexahydrophthalic acid glycidyl ester, 3,4-epoxycyclohexylmethyl carboxylate, etc. Among these, dicyclopentadiene skeleton-containing epoxy resins are preferred. These alicyclic epoxy resins (B13) can be used alone or in combination of two or more.

By using the glycidylamine type epoxy resin (B11) in combination with one or more selected from the group consisting of the glycidyl ether type resin (B12) and the alicyclic epoxy resin (B13), excellent adhesiveness can be achieved. That is, the glycidylamine type epoxy resin (B11) has a reaction and curing action between the acid-modified polyolefin (A) and the glycidyl ether type epoxy resin (B12) and/or the alicyclic epoxy resin (B13). Furthermore, the glycidylamine type epoxy resin (B11) has a reaction and curing catalyst action between the acid-modified polyolefin (A) and the glycidylamine type epoxy resin (B11), between the glycidylamine type epoxy resins (B11), between the glycidyl ether type epoxy resins (B12), between the alicyclic epoxy resins (B13), and between the glycidylamine type epoxy resin (B11) and the glycidyl ether type epoxy resin (B12) and/or the alicyclic epoxy resin (B13). Therefore, excellent adhesion can be achieved not only to polyimide, but also to non-polar resin substrates such as liquid crystal polymers and metal substrates.

When the glycidyl amine type epoxy resin (B11) is used in combination with one or more selected from the group consisting of the glycidyl ether type epoxy resin (B12) and the alicyclic type epoxy resin (B13), the total content thereof is preferably 2 to 60 parts by mass, more preferably 5 to 40 parts by mass, and further preferably 10 to 20 parts by mass, per 100 parts by mass of the acid-modified polyolefin (A), from the viewpoints of adhesiveness, solder heat resistance, and pot life.

The content of the glycidylamine type epoxy resin (B11) is preferably 1 to 50 mass % of the total epoxy resin (B1), more preferably 2 to 30 mass %, and most preferably 3 to 10 mass %. By making it equal to or more than the lower limit, the catalytic action is exerted, and the adhesiveness and solder heat resistance become good, and by making it equal to or less than the upper limit, the crosslinking reaction does not proceed excessively, and the rigidity is not too high, and the adhesiveness becomes good. Furthermore, the crosslinking reaction does not proceed excessively during storage of the adhesive composition in solution, and the pot life is also good.

Other epoxy resins can also be used as the epoxy resin (B1) used in the present invention, such as biphenyl type epoxy resins, naphthalene type epoxy resins, bisphenol A type epoxy resins, bisphenol F type epoxy resins, glycidyl ester types such as dimer acid glycidyl ester, triglycidyl isocyanurate, epoxidized polybutadiene, epoxidized soybean oil, and other alicyclic or aliphatic epoxides, which may be used alone or in combination of two or more.

<Isocyanate compound (B2)>
The isocyanate compound (B2) (hereinafter, also simply referred to as component (B2)) used in the present invention is preferably a polyfunctional isocyanate compound having two or more isocyanate groups in one molecule. Compounds derived from polyfunctional isocyanate compounds can also be used.

The content of the isocyanate compound (B2) is preferably 0.5 parts by mass or more relative to 100 parts by mass of the acid-modified polyolefin (A). Since a sufficient curing effect can be obtained and excellent adhesiveness and solder heat resistance can be expressed, it is more preferably 1 part by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 10 parts by mass or more. In addition to adhesiveness, solder heat resistance, and pot life, it has excellent low dielectric properties, so it is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 40 parts by mass or less, and particularly preferably 35 parts by mass or less.

The isocyanate compound (B2) may be any of an aromatic isocyanate compound, an alicyclic isocyanate compound, and an aliphatic isocyanate compound, which may be used alone or in combination of two or more. Among these, an aliphatic isocyanate compound is preferred, and an aliphatic diisocyanate compound is more preferred. Examples of aromatic isocyanate compounds include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 1,3-xylylene diisocyanate, 1,4-naphthalene diisocyanate, 1,5-naphthalene diisocyanate, 1,8-naphthalene diisocyanate, 3,3'-biphenyl diisocyanate, 4,4'-biphenyl diisocyanate, 3,3'-dimethyl-4,4'-biphenyl diisocyanate, diphenylmethane-3,3'-diisocyanate, diphenylmethane-4,4'-diisocyanate, and 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate. These can be used alone or in combination of two or more. Among these, 3,3'-dimethyl-4,4'-biphenyl diisocyanate is preferred. Examples of the alicyclic isocyanate compound include isophorone diisocyanate, norbornene diisocyanate, 1,2-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, etc., which can be used alone or in combination of two or more. The aliphatic isocyanate compound can be either a linear or branched aliphatic isocyanate. Preferred are linear aliphatic diisocyanate compounds, and specific examples thereof include 1,3-propane diisocyanate, 1,4-tetramethylene diisocyanate, 1,5-pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,7-heptamethylene diisocyanate, 1,8-octamethylene diisocyanate, and 1,9-nonamethylene diisocyanate, which can be used alone or in combination of two or more. Of these, 1,6-hexamethylene diisocyanate is preferred.

The isocyanate compound (B2) may be an isocyanurate, adduct, biuret, uretdione, or allophanate of the isocyanate compound. These compounds may be used alone or in combination of two or more. Among them, the isocyanurate or biuret is preferred.

<Carbodiimide compound (B3)>
The carbodiimide compound (B3) used in the present invention (hereinafter also simply referred to as component (B3)) is preferably a polyfunctional carbodiimide compound having two or more carbodiimide groups in one molecule. By using the carbodiimide compound (B3), the carboxylic anhydride group of the acid-modified polyolefin reacts with the carbodiimide, enhancing the interaction between the adhesive composition and the substrate, and improving the adhesiveness and solder heat resistance.

The content of the carbodiimide compound (B3) is preferably 0.5 parts by mass or more relative to 100 parts by mass of the acid-modified polyolefin (A). Since a sufficient curing effect can be obtained and excellent adhesiveness and solder heat resistance can be expressed, it is more preferably 1 part by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 10 parts by mass or more. In addition to adhesiveness, solder heat resistance, and pot life, it has excellent low dielectric properties, so it is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 40 parts by mass or less, and particularly preferably 35 parts by mass or less.

The carbodiimide compound (B3) may be any of an aromatic carbodiimide compound, an alicyclic carbodiimide compound, and an aliphatic carbodiimide compound, which may be used alone or in combination of two or more. Examples of the aromatic carbodiimide compound include poly-m-phenylene carbodiimide, poly-p-phenylene carbodiimide, polytolylene carbodiimide, poly(diisopropylphenylene carbodiimide), poly(methyldiisopropylphenylene carbodiimide), and poly(4,4'-diphenylmethane carbodiimide). Examples of the alicyclic carbodiimide compound include poly-m-cyclohexylcarbodiimide, poly-p-cyclohexylcarbodiimide, poly(4,4'-dicyclohexylmethanecarbodiimide, poly(3,3'-dicyclohexylmethanecarbodiimide, etc. The aliphatic carbodiimide compound may be either a linear or branched aliphatic carbodiimide compound. A linear aliphatic carbodiimide compound is preferred, and specific examples thereof include polymethylenecarbodiimide, polyethylenecarbodiimide, polypropylenecarbodiimide, polybutylenecarbodiimide, polypentamethylenecarbodiimide, polyhexamethylenecarbodiimide, etc. These may be used alone or in combination of two or more. Among these, an aromatic carbodiimide or an alicyclic carbodiimide is preferred.

<Oligophenylene ether (C)>
By incorporating an oligophenylene ether (C) in the adhesive composition of the present invention, it is possible to achieve even better solder heat resistance. The oligophenylene ether (C) (hereinafter also simply referred to as component (C)) used in the present invention is not particularly limited, but is preferably a compound having a structural unit represented by the following general formula (c1) and/or a structural unit represented by the following general formula (c2).

In the general formula (c1), R ₁ , R ₂ , R ₃ , and R ₄ are each preferably independently a hydrogen atom, an optionally substituted alkyl group, an optionally substituted alkenyl group, an optionally substituted alkynyl group, an optionally substituted aryl group, an optionally substituted aralkyl group, or an optionally substituted alkoxy group. The "alkyl group" of the optionally substituted alkyl group is, for example, a linear or branched alkyl group having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms. More specifically, examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, and a hexyl group, and more preferably a methyl group or an ethyl group. Examples of the "alkenyl group" of the optionally substituted alkenyl group include, for example, an ethenyl group, a 1-propenyl group, a 2-propenyl group, a 3-butenyl group, a pentenyl group, a hexenyl group, and the like, with an ethenyl group or a 1-propenyl group being more preferred. Examples of the "alkynyl group" of the optionally substituted alkynyl group include, for example, an ethynyl group, a 1-propynyl group, a 2-propynyl (propargyl) group, a 3-butynyl group, a pentynyl group, a hexynyl group, and the like, with an ethynyl group, a 1-propynyl group, or a 2-propynyl (propargyl) group being more preferred. Examples of the "aryl group" of the optionally substituted aryl group include, for example, a phenyl group, a naphthyl group, and the like, with a phenyl group being more preferred. Examples of the "aralkyl group" of the aralkyl group which may be substituted include a benzyl group, a phenethyl group, a 2-methylbenzyl group, a 4-methylbenzyl group, an α-methylbenzyl group, a 2-vinylphenethyl group, a 4-vinylphenethyl group, and the like, with a benzyl group being more preferred. The "alkoxy group" of the alkoxy group which may be substituted is, for example, a linear or branched alkoxy group having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms. Examples include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, and the like, with a methoxy group or an ethoxy group being more preferred. When the above alkyl group, aryl group, alkenyl group, alkynyl group, aralkyl group, and alkoxy group are substituted, they may have one or more substituents. Examples of such a substituent include halogen atoms (e.g., fluorine, chlorine, and bromine atoms), alkyl groups having 1 to 6 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, and hexyl), aryl groups (e.g., phenyl and naphthyl), alkenyl groups (e.g., ethenyl, 1-propenyl, and 2-propenyl), alkynyl groups (e.g., ethynyl, 1-propynyl, and 2-propynyl), aralkyl groups (e.g., benzyl and phenethyl), and alkoxy groups (e.g., methoxy and ethoxy). Of these, it is preferable that R ₁ and R ₄ are methyl groups and R ₂ and R ₃ are hydrogen.

In the general formula (c2), R ₁₁ , R ₁₂ , R ₁₃ , R ₁₄ , R ₁₅ , R ₁₆ , R ₁₇ , and _{R 18 are} each preferably independently a hydrogen atom, an optionally substituted alkyl group, an optionally substituted alkenyl group, an optionally substituted alkynyl group, an optionally substituted aryl group, an optionally substituted aralkyl group, or an optionally substituted alkoxy group. The definition of each substituent is as described above. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, and a hexyl group, and a methyl group is preferable. Among them, it is preferable that R ₁₃ , R ₁₄ , R ₁₇ , and R ₁₈ are a methyl group, and _{R 11 ,} R ₁₂ , R ₁₅ , and R ₁₆ are hydrogen. In addition, -A- is preferably a linear, branched or cyclic divalent hydrocarbon group having 20 or less carbon atoms, or oxygen. The number of carbon atoms in A is more preferably 1 to 15, and even more preferably 2 to 10. In addition, examples of the divalent hydrocarbon group in A include a methylene group, an ethylene group, an n-propylene group, an n-butylene group, a cyclohexylene group, and a phenylene group, and among these, a phenylene group is preferable. Oxygen is particularly preferable.

The oligophenylene ether (C) may be a modified oligophenylene ether in which a part or all of the oligophenylene ether is functionalized with an ethylenically unsaturated group such as a vinylbenzyl group, an epoxy group, an amino group, a hydroxy group, a mercapto group, a carboxyl group, or a silyl group. Furthermore, it is preferable that both ends have a hydroxy group, an epoxy group, or an ethylenically unsaturated group. Examples of the ethylenically unsaturated group include alkenyl groups such as ethenyl groups, allyl groups, methacrylic groups, propenyl groups, butenyl groups, hexenyl groups, and octenyl groups, cycloalkenyl groups such as cyclopentenyl groups and cyclohexenyl groups, and alkenylaryl groups such as vinylbenzyl groups and vinylnaphthyl groups. In addition, both ends may be the same functional group or different functional groups. From the viewpoint of highly controlling the balance between low dielectric tangent and reduction of resin residue, it is preferable that both ends are hydroxy groups or vinylbenzyl groups, and it is more preferable that both ends are hydroxy groups or vinylbenzyl groups.

As the compound having a structural unit represented by general formula (c1), a compound represented by general formula (c3) is particularly preferable.
In formula (c3), n is preferably 3 or more, more preferably 5 or more, and is preferably 23 or less, more preferably 21 or less, and even more preferably 19 or less.

Moreover, as the compound having a structural unit represented by general formula (c2), a compound represented by general formula (c4) is particularly preferable.
In formula (c4), n is preferably 2 or more, more preferably 4 or more, and is preferably 23 or less, more preferably 20 or less, and even more preferably 18 or less.

The number average molecular weight of the oligophenylene ether (C) is preferably 3000 or less, more preferably 2700 or less, and even more preferably 2500 or less. The number average molecular weight of the oligophenylene ether (C) is preferably 500 or more, and more preferably 700 or more. By setting the number average molecular weight of the oligophenylene ether (C) to the lower limit or more, the flexibility of the obtained adhesive layer can be improved. On the other hand, by setting the number average molecular weight of the oligophenylene ether (C) to the upper limit or less, the solubility in organic solvents can be improved.

The content of the oligophenylene ether (C) is preferably 0.05 parts by mass or more relative to 100 parts by mass of the acid-modified polyolefin (A). Since excellent solder heat resistance can be exhibited, it is more preferably 1 part by mass or more, and even more preferably 5 parts by mass or more. In addition, it is preferably 200 parts by mass or less. Since excellent adhesiveness and solder heat resistance can be exhibited, it is more preferably 150 parts by mass or less, even more preferably 100 parts by mass or less, and particularly preferably 50 parts by mass or less.

<Adhesive Composition>
The adhesive composition of the present invention is a composition containing an acid-modified polyolefin (A) that satisfies the above-mentioned specific requirements, and further containing at least one selected from the group consisting of an epoxy resin (B1), an isocyanate compound (B2) and a carbodiimide compound (B3), and preferably further containing the above-mentioned oligophenylene ether (C). The adhesive composition of the present invention has excellent adhesion not only to polyimides but also to low-polarity resin substrates such as liquid crystal polymers and metal substrates, and can further exhibit solder heat resistance, pot life and electrical properties (low dielectric properties). That is, the adhesive composition is applied to a substrate, and the adhesive coating film (adhesive layer) after curing can exhibit excellent low dielectric properties.

The total amount of maleic acid and maleic anhydride contained in the adhesive composition is preferably 1 mass% or less. In order to improve adhesion, solder heat resistance, and pot life, it is more preferably 0.8 mass% or less, even more preferably 0.6 mass% or less, and particularly preferably 0.4 mass% or less. The smaller the total amount of maleic anhydride and maleic acid, the better, but from an industrial standpoint, it is sufficient to have it be 0.01 mass% or more, and it is acceptable to have it be 0.1 mass% or more.

The adhesive composition according to the present invention preferably has a relative dielectric constant (ε _c ) of 3.0 or less at a frequency of 1 GHz. More preferably, it is 2.6 or less, and even more preferably, it is 2.3 or less. There is no particular lower limit, but in practical use, it is 2.0. Furthermore, the relative dielectric constant (ε _c ) over the entire frequency range from 1 GHz to 60 GHz is preferably 3.0 or less, more preferably 2.6 or less, and even more preferably 2.3 or less.

The adhesive composition according to the present invention preferably has a dielectric loss tangent (tan δ) of 0.02 or less at a frequency of 1 GHz. More preferably, it is 0.01 or less, and even more preferably, it is 0.008 or less. There is no particular lower limit, but in practical use, it is 0.0001. Furthermore, the dielectric loss tangent (tan δ) over the entire frequency range of 1 GHz to 60 GHz is preferably 0.02 or less, more preferably 0.01 or less, and even more preferably 0.008 or less.

In the present invention, the dielectric constant (ε _c ) and the dielectric loss tangent (tan δ) can be measured as follows. That is, the adhesive composition is applied to a release substrate so that the thickness after drying is 25 μm, and dried at about 130° C. for about 3 minutes. Then, the adhesive composition is cured by heat treatment at about 140° C. for about 4 hours, and the cured adhesive composition layer (adhesive layer) is peeled off from the release film. The dielectric constant (ε _c ) and the dielectric loss tangent (tan δ) of the adhesive composition layer at a frequency of 1 GHz after peeling are measured. Specifically, the dielectric constant (ε _c ) and the dielectric loss tangent (tan δ) can be calculated from the measurement by the cavity resonator perturbation method.

<Organic solvent>
The adhesive composition of the present invention may further contain an organic solvent. The organic solvent used in the present invention is not particularly limited as long as it dissolves the acid-modified polyolefin (A), the epoxy resin (B1), the isocyanate compound (B2), the carbodiimide compound (B3) and the oligophenylene ether (C). Specifically, for example, aromatic hydrocarbons such as benzene, toluene, xylene, etc., aliphatic hydrocarbons such as hexane, heptane, octane, decane, etc., alicyclic hydrocarbons such as cyclohexane, cyclohexene, methylcyclohexane, ethylcyclohexane, etc., halogenated hydrocarbons such as trichloroethylene, dichloroethylene, chlorobenzene, chloroform, etc., alcohol solvents such as methanol, ethanol, isopropyl alcohol, butanol, pentanol, hexanol, propanediol, phenol, etc., acetone, methyl isobutyl ketone, methyl ethyl ketone, pentanone, hexanone, cyclohexanone, isophorone, acetophenone, etc. ketone-based solvents, cellosolves such as methyl cellosolve and ethyl cellosolve, ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, methyl propionate and butyl formate, glycol ether-based solvents such as ethylene glycol mono n-butyl ether, ethylene glycol mono iso-butyl ether, ethylene glycol mono tert-butyl ether, diethylene glycol mono n-butyl ether, diethylene glycol mono iso-butyl ether, triethylene glycol mono n-butyl ether and tetraethylene glycol mono n-butyl ether, and the like can be used alone or in combination of two or more of these. In particular, methylcyclohexane and toluene are preferred from the viewpoints of working environment and drying properties.

The organic solvent is preferably in the range of 100 to 1000 parts by mass, more preferably in the range of 200 to 900 parts by mass, and most preferably in the range of 300 to 800 parts by mass, relative to 100 parts by mass of the acid-modified olefin (A). By setting it to the lower limit or more, the liquid state and pot life are improved. Also, by setting it to the upper limit or less, it is advantageous in terms of production costs and transportation costs.

From the viewpoint of the solution state and pot life of the adhesive composition, the organic solvent is preferably a mixture of one or more solvents (D1) selected from the group consisting of aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, and halogenated hydrocarbons, and one or more solvents (D2) selected from the group consisting of alcohol-based solvents, ketone-based solvents, ester-based solvents, and glycol ether-based solvents. The mixing ratio is preferably solvent (D1)/solvent (D2)=50-97/50-3 (mass ratio), more preferably 55-95/45-5 (mass ratio), even more preferably 60-90/40-10 (mass ratio), and particularly preferably 70-80/30-20 (mass ratio). By keeping it within the above range, the solution state and pot life of the adhesive composition are improved. In addition, it is particularly preferable that the solvent (D1) is an aromatic hydrocarbon or an alicyclic hydrocarbon, and the solvent (D2) is a ketone-based solvent.

The adhesive composition of the present invention may further contain other components as necessary within the range that does not impair the effects of the present invention. Specific examples of such components include a flame retardant, a tackifier, a filler, and a silane coupling agent.

<Flame retardants>
The adhesive composition of the present invention may contain a flame retardant as necessary within a range that does not impair the effects of the present invention. Examples of flame retardants include bromine-based, phosphorus-based, nitrogen-based, and metal hydroxide compounds. Among them, phosphorus-based flame retardants are preferred, and known phosphorus-based flame retardants such as phosphate esters, for example, trimethyl phosphate, triphenyl phosphate, and tricresyl phosphate, phosphate salts, for example, aluminum phosphinate, and phosphazenes can be used. These may be used alone or in any combination of two or more. When a flame retardant is contained, it is preferably contained in a range of 1 to 200 parts by mass, more preferably in a range of 5 to 150 parts by mass, and most preferably in a range of 10 to 100 parts by mass, relative to 100 parts by mass of the total of components (A) to (C). By making it equal to or more than the lower limit, the flame retardancy is improved. Furthermore, by making it equal to or less than the upper limit, the adhesiveness, solder heat resistance, electrical properties, and the like are not reduced.

<Tackifier>
The adhesive composition of the present invention may contain a tackifier as necessary within a range that does not impair the effects of the present invention. Examples of tackifiers include polyterpene resins, rosin resins, aliphatic petroleum resins, alicyclic petroleum resins, copolymerized petroleum resins, styrene resins, and hydrogenated petroleum resins, and are used for the purpose of improving adhesive strength. These may be used alone or in any combination of two or more. When a tackifier is contained, it is preferably contained in a range of 1 to 200 parts by mass, more preferably in a range of 5 to 150 parts by mass, and most preferably in a range of 10 to 100 parts by mass, relative to a total of 100 parts by mass of components (A) to (C). By making it equal to or greater than the lower limit, the effect of the tackifier can be achieved. In addition, by making it equal to or less than the upper limit, the adhesiveness, solder heat resistance, electrical properties, etc. are not reduced.

<Filler>
The adhesive composition of the present invention may contain a filler such as silica as necessary within a range that does not impair the effects of the present invention. The incorporation of silica is highly preferable because it improves the solder heat resistance properties. Hydrophobic silica and hydrophilic silica are generally known as silica, but here, hydrophobic silica treated with dimethyldichlorosilane, hexamethyldisilazane, octylsilane, or the like is preferable in order to impart moisture absorption resistance. When silica is contained, the content is preferably in the range of 0.05 to 30 parts by mass with respect to 100 parts by mass of the total of components (A) to (C). By making the content equal to or greater than the lower limit, the effect of improving the solder heat resistance can be achieved. In addition, by making the content equal to or less than the upper limit, there is no poor dispersion of silica, and the solution viscosity is good, resulting in good workability. In addition, the adhesiveness is not reduced.

<Silane coupling agent>
The adhesive composition of the present invention may contain a silane coupling agent as necessary, as long as the effect of the present invention is not impaired. The incorporation of a silane coupling agent is highly preferred because it improves the adhesiveness to metals and solder heat resistance. The silane coupling agent is not particularly limited, but examples include those having an unsaturated group, those having a glycidyl group, and those having an amino group. Among these, silane coupling agents having a glycidyl group, such as γ-glycidoxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltriethoxysilane, are more preferred from the viewpoint of solder heat resistance. When a silane coupling agent is contained, the content is preferably in the range of 0.5 to 20 parts by mass with respect to 100 parts by mass of the total of the components (A) to (C). By making it 0.5 parts by mass or more, excellent solder heat resistance is obtained. On the other hand, by making it 20 parts by mass or less, solder heat resistance and adhesiveness are improved.

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

<Base material>
In the present invention, the substrate is not particularly limited as long as it is capable of forming an adhesive layer by applying and drying the adhesive composition of the present invention. Examples of the substrate include resin substrates such as film-like resins, metal substrates such as metal plates and metal foils, and papers.

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

As the metal substrate, any conventionally known conductive material usable for a circuit board can be used. Examples of materials include various metals such as SUS, copper, aluminum, iron, steel, zinc, and nickel, as well as their alloys, plated products, and metals treated with other metals such as zinc and chromium compounds. Metal foil is preferred, and copper foil is more preferred. There is no particular limitation on the thickness of the metal foil, but it is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 10 μm or more. It is also preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less. If the thickness is too thin, it may be difficult to obtain sufficient electrical performance of the circuit, while if the thickness is too thick, the processing efficiency during circuit fabrication may decrease. Metal foil is usually provided in a rolled form. The form of the metal foil used in manufacturing the printed wiring board of the present invention is not particularly limited. When a ribbon-shaped metal foil is used, its length is not particularly limited. In addition, its width is also not particularly limited, but it is preferably about 250 to 500 cm.

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

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

<Adhesive sheet>
In the present invention, the adhesive sheet is a laminate of the laminate and a release substrate with an adhesive composition interposed therebetween. Specific configurations include laminate/adhesive layer/release substrate, or release substrate/adhesive layer/laminate/adhesive layer/release substrate. The release substrate functions as a protective layer for the substrate by being laminated. In addition, by using a release substrate, the release substrate can be released from the adhesive sheet and the adhesive layer can be transferred to another substrate.

The adhesive composition of the present invention can be applied to various laminates and dried in a conventional manner to obtain the adhesive sheet of the present invention. After drying, a release substrate is attached to the adhesive layer, which allows winding without causing offset onto the substrate, resulting in excellent operability, and the adhesive layer is protected, resulting in excellent storage stability and ease of use. After application to a release substrate and drying, the adhesive layer itself can be transferred to another substrate by attaching another release substrate as necessary.

<Release base material>
The release substrate is not particularly limited, but examples thereof include those in which a coating layer of a filler such as clay, polyethylene, or polypropylene is provided on both sides of paper such as fine paper, craft paper, roll paper, or glassine paper, and a silicone-based, fluorine-based, or alkyd-based release agent is further applied on each coating layer. Other examples include various olefin films such as polyethylene, polypropylene, ethylene-α-olefin copolymer, and propylene-α-olefin copolymer alone, and films such as polyethylene terephthalate on which the release agent is applied. Due to the release force between the release substrate and the adhesive layer, and the adverse effect of silicone on electrical properties, it is preferable to use a polypropylene-filled coating on both sides of fine paper and an alkyd-based release agent thereon, or an alkyd-based release agent on polyethylene terephthalate.

In the present invention, the method of coating the adhesive composition on the substrate is not particularly limited, but includes a comma coater, a reverse roll coater, and the like. Alternatively, if necessary, the adhesive layer can be provided directly or by a transfer method on the rolled copper foil or polyimide film, which is a printed wiring board constituent material. The thickness of the adhesive layer after drying is appropriately changed as necessary, but is preferably in the range of 5 to 200 μm. If the adhesive film thickness is less than 5 μm, the adhesive strength is insufficient. If it is 200 μm or more, there is a problem that the drying is insufficient, the residual solvent increases, and blisters occur during pressing in the production of printed wiring boards. The drying conditions are not particularly limited, but the residual solvent rate after drying is preferably 1 mass % or less. If it exceeds 1 mass %, there is a problem that the residual solvent foams during pressing of the printed wiring board, causing blisters.

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

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

Furthermore, if necessary, two or more of the above printed wiring boards may be laminated.

The adhesive composition of the present invention can be suitably used for each adhesive layer of a printed wiring board. In particular, when the adhesive composition of the present invention is used as an adhesive, it has high adhesion to not only conventional polyimide, polyester film, and copper foil constituting a printed wiring board, but also low polarity resin substrates such as LCP, and can obtain solder reflow resistance, and the adhesive layer itself has excellent low dielectric properties. Therefore, it is suitable as an adhesive composition used for cover films, laminates, resin-coated copper foils, and bonding sheets.

In the printed wiring board of the present invention, any resin film that has been conventionally used as a substrate for a printed wiring board can be used as the substrate film. Examples of the resin of the substrate film include polyester resin, polyamide resin, polyimide resin, polyamideimide resin, liquid crystal polymer, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resin, and fluorine resin. In particular, the substrate film has excellent adhesion to low polar substrates such as liquid crystal polymer, polyphenylene sulfide, syndiotactic polystyrene, and polyolefin resin.

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

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

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

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

The formation of the circuit in the metal foil layer can be performed by a conventionally known method. Either an active method or a subtractive method can be used. The subtractive method is preferable.

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

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

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

The substrate film-side semi-finished product and the cover film-side semi-finished product are stored, for example, in the form of a roll, and then laminated together to produce a printed wiring board. Any method can be used as a lamination method, and for example, they can be laminated together using a press or roll. In addition, they can be laminated together while heating them by a method using a hot press or a hot roll device.

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

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

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

<Example>
The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the examples. In the examples and comparative examples, parts simply indicate parts by mass. Examples 2, 3, 15, 16, 26, and 27 are reference examples.

(Physical property evaluation method)

(1) Acid value (mgKOH/g)
The acid value (mg KOH/g) in the present invention was measured by dissolving the acid-modified polyolefin in toluene and titrating it with a methanol solution of sodium methoxide using phenolphthalein as an indicator.

(2) Number average molecular weight (Mn), weight average molecular weight (Mw)
The number average molecular weight in the present invention is a value measured by gel permeation chromatography (hereinafter, referred to as GPC, standard substance: polystyrene resin, mobile phase: tetrahydrofuran, column: Shodex KF-802 + KF-804L + KF-806L, column temperature: 30°C, flow rate: 1.0 ml/min, detector: RI detector) manufactured by Shimadzu Corporation.

(3) Measurement of Melting Point (Tm) and Heat of Fusion (ΔH) The melting point and heat of fusion in the present invention are values measured using a differential scanning calorimeter (hereinafter, abbreviated as DSC, manufactured by TA Instruments Japan, Q-2000) from the top temperature and area of the melting peak when the material is heated and melted at a rate of 20° C./min, cooled to form a resin, and then heated and melted again.

(4) Measurement of the binding ratio of carboxylic anhydride group (a1) to carboxylic acid group (a2) [Preparation of calibration curve solution]
Weigh out 0.050±0.001 g of maleic anhydride, dissolve it in chloroform, and adjust the volume to 50 ml to prepare a 1.000 g/l solution A. Dilute solution A two-fold to prepare a 0.500 g/l solution B. Dilute solution B four-fold to prepare a 0.125 g/l solution C. [Creating a calibration curve]
Using an infrared spectrophotometer (FT-IR8200PC, manufactured by Shimadzu Corporation), the absorption spectrum (Abs) is measured for the blank solution (chloroform), followed by solution C, solution B, and solution A. The maximum absorption intensity in the vicinity of 1780 cm ^-1 of each spectrum is read, and a calibration curve is prepared with the maleic anhydride concentration on the vertical axis and the intensity on the horizontal axis, and the slope (1/a) is calculated.
[Preparation of sample solution and measurement]
A sample (0.50±0.01 g of acid-modified polyolefin (A)) is weighed out and dissolved in 6.7 ml of chloroform to prepare a sample solution. The absorption spectrum (Abs) of the sample solution is measured using an infrared spectrophotometer. The maximum absorption intensities of the absorption spectrum near 1780 cm ^-1 (carboxylic anhydride group (a1)) and near 1730 cm ^-1 (carboxylic acid group (a2)) are read, and the contents (mmol/g) of (a1) and (a2) per 1 g of resin are calculated from the calibration curve.
[Calculation]
Calculation formula 1: Carboxylic acid anhydride group (a1) content (mmol/g)=H1×(1/a)/C÷99×1000
Calculation formula 2: Carboxylic acid group (a2) content (mmol/g) = H2 x 2.08 x (1/a)/C ÷ 117 x 1000
H1: maximum absorption intensity (Abs) near 1780 ^cm
H2: maximum absorption intensity (Abs) near 1730 ^cm
2.08: Conversion coefficient for converting the absorption of maleic acid to the absorption of maleic anhydride; 1/a: Slope of the calibration curve; C: Concentration (mass%) of the acid-modified polyolefin (A) in the sample solution

(5) Measurement of the total amount of (a1) and (a2) in the total acid components bonded to the acid-modified polyolefin (A) The molar ratios of the carboxylic anhydride group (a1), the carboxylic acid group ( ^a2 ) and other acids (acrylic acid, etc.) in the acid-modified polyolefin (A) were determined using ^a 400 MHz 1H-nuclear magnetic resonance spectrometer (1H-NMR). Deuterated chloroform was used as the solvent.

(6) Peel strength (adhesion)
The adhesive composition described below was applied to a 12.5 μm thick polyimide film (Apical (registered trademark) manufactured by Kaneka Corporation) or a 25 μm thick LCP film (Vexstar (registered trademark) manufactured by Kuraray Co., Ltd.) so that the thickness after drying was 25 μm, and dried at 130 ° C for 3 minutes. The adhesive film (B stage product) obtained in this way was laminated to a rolled copper foil (BHY series manufactured by JX Metals Corporation) having a thickness of 18 μm. The laminate was pressed for 30 seconds at 160 ° C under a pressure of 40 kgf / cm ² so that the shiny surface of the rolled copper foil was in contact with the adhesive layer. The laminate was then heat-treated at 140 ° C for 4 hours to harden the film, and a sample for evaluating peel strength was obtained. The peel strength was measured by performing a 90 ° peel test at 25 ° C, pulling the film and pulling at a tensile speed of 50 mm / min. This test indicates the adhesive strength at room temperature.
<Evaluation criteria>
◎: 1.0 N/mm or more ○: 0.8 N/mm or more and less than 1.0 N/mm △: 0.5 N/mm or more and less than 0.8 N/mm ×: Less than 0.5 N/mm

(7) Solder Heat Resistance Samples were prepared in the same manner as above, and a 2.0 cm × 2.0 cm sample piece was aged at 23° C. for 2 days, floated in a molten solder bath at 280° C. for 10 seconds, and the presence or absence of any change in appearance, such as blistering, was confirmed.
<Evaluation criteria>
◎: No blistering ○: Some blistering △: Many blistering ×: Blistering and discoloration

(8) Dielectric constant (ε _c ) and dielectric tangent (tan δ)
The adhesive composition described below was applied to a 100 μm thick Teflon (registered trademark) sheet so that the thickness after drying and curing was 25 μm, and dried at 130 ° C for 3 minutes. Then, after curing by heat treatment at 140 ° C for 4 hours, the Teflon (registered trademark) sheet was peeled off to obtain a test adhesive resin sheet. The obtained test adhesive resin sheet was cut into a rectangular sample of 8 cm × 3 mm to obtain a test sample. The relative dielectric constant (ε _c ) and dielectric loss tangent (tan δ) were measured using a network analyzer (manufactured by Anritsu Corporation) by a cavity resonator perturbation method under conditions of a temperature of 23 ° C and a frequency of 1 GHz. The obtained relative dielectric constant and dielectric loss tangent were evaluated as follows.
<Evaluation criteria for dielectric constant>
◎: 2.3 or less ○: More than 2.3 and less than 2.6 △: More than 2.6 and less than 3.0 ×: More than 3.0 <Evaluation criteria for dielectric loss tangent>
◎: 0.008 or less ○: More than 0.008 and 0.01 or less △: More than 0.01 and 0.02 or less ×: More than 0.02

(9) Pot life The pot life refers to the stability of a resin solution (varnish) prepared by mixing component (A), component (B), and, if necessary, component (C), and a mixed solvent of methylcyclohexane, methyl ethyl ketone, and toluene (methylcyclohexane/methyl ethyl ketone/toluene=72/8/20 (v/v)) to a solids concentration of 20% by mass, and the stability of the varnish immediately after mixing or after a certain period of time has elapsed since mixing. When the pot life is good, the viscosity of the varnish increases little and it can be stored for a long period of time, and when the pot life is poor, the viscosity of the varnish increases (thickening), and in severe cases, it causes a gelling phenomenon, making it difficult to apply to a substrate and impossible to store for a long period of time.
The dispersion viscosity of the varnishes prepared according to the ratios in Tables 2 to 4 was measured at 25° C. using a Brookfield viscometer (rotor No. 2, rotation speed 60 rpm) to determine the initial dispersion viscosity ηB0. The varnishes were then stored at 25° C. for 7 days, and the dispersion viscosity ηB was measured at 25° C. The varnish viscosity was calculated using the following formula and evaluated as follows:
Solution viscosity ratio = solution viscosity ηB/solution viscosity ηB0
<Evaluation criteria>
◎: 0.5 or more and less than 1.5 ○: 1.5 or more and less than 2.0 △: 2.0 or more and less than 3.0 ×: 3.0 or more, or viscosity measurement impossible due to purinization

(Acid-modified polyolefin (A))
Production Example 1 (Production of acid-modified polyolefins PO-1a and PO-1b)
Propylene-butene copolymer (Mitsui Chemicals, Inc. "Tafmer (registered trademark) XM7080") 100 parts by mass, maleic anhydride 20 parts by mass, di-tert-butyl peroxide 6 parts by mass were kneaded and reacted using a twin-screw extruder with the maximum temperature of the cylinder set to 170 ° C. Thereafter, degassing was performed under reduced pressure in the extruder, and the remaining unreacted material was removed to obtain a maleic anhydride-modified propylene-butene copolymer (PO-1a, acid value 25 mg KOH / g, number average molecular weight 25,000, weight average molecular weight 80,000, Tm 75 ° C., ΔH 30 J / g, carboxylic anhydride group (a1) / carboxylic acid group bond ratio (a2) = 89 / 11, total amount of (a1) and (a2) in the total acid component 100 mol%) was obtained.
Next, PO-1a was left to stand in a desiccator in an environment of 30° C. and RH 70% for one week to obtain P0-1b, which had a carboxylic anhydride group (a1)/carboxylic acid group (a2) bond ratio of 15/85.

Production Example 2 (Production of Acid-Modified Polyolefins PO-2a and PO-2b)
The same procedures as in Production Example 1 were carried out except that the amount of maleic anhydride charged was changed to 25 parts by mass, thereby obtaining a maleic anhydride-modified propylene-butene copolymer (PO-2a, acid value 48 mg KOH/g, number average molecular weight 17,000, weight average molecular weight 50,000, Tm 75° C., ΔH 25 J/g, bonding ratio (a1)/carboxylic acid group (a2)=88/12, total amount of (a1) and (a2) in the total acid components 100 mol%).
Next, PO-2a was left to stand in a desiccator under an environment of 30° C. and RH 70% for one week to obtain P0-2b, which had a carboxylic anhydride group (a1)/carboxylic acid group (a2) bond ratio of 13/87.

Production Example 3 (Production of acid-modified polyolefins PO-3a and PO-3b)
The same procedures as in Production Example 1 were carried out except that the amount of maleic anhydride charged was changed to 6 parts by mass, thereby obtaining a maleic anhydride-modified propylene-butene copolymer (PO-3a, acid value 7 mg KOH/g, number average molecular weight 35,000, weight average molecular weight 130,000, Tm 82° C., ΔH 25 J/g, bonding ratio (a1)/carboxylic acid group (a2)=90/10, total amount of (a1) and (a2) in the total acid components 100 mol%).
Next, PO-3a was left to stand in a desiccator under an environment of 30° C. and RH 70% for one week to obtain P0-3b, which had a carboxylic anhydride group (a1)/carboxylic acid group bonding ratio (a2) of 17/83.

Production Example 4 (Production of acid-modified polyolefins PO-4a and PO-4b)
The same procedures as in Production Example 1 were carried out except that the amount of maleic anhydride charged was changed to 30 parts by mass, thereby obtaining a maleic anhydride-modified propylene-butene copolymer (PO-4a, acid value 55 mg KOH/g, number average molecular weight 13,000, weight average molecular weight 40,000, Tm 70° C., ΔH 25 J/g, bonding ratio (a1)/carboxylic acid group (a2)=88/12, total amount of (a1) and (a2) in the total acid components 100 mol%).
Next, PO-4b was left to stand in a desiccator in an environment of 30° C. and RH 70% for one week to obtain P0-4b, which had a carboxylic anhydride group (a1)/carboxylic acid group (a2) bond ratio of 12/88.

Production Example 5 (Production of acid-modified polyolefins PO-5a and PO-5b)
The same procedures as in Production Example 1 were carried out except that the amounts of maleic anhydride and di-tert-butyl peroxide were changed to 2 parts by mass and 0.5 parts by mass, respectively, to obtain a maleic anhydride-modified propylene-butene copolymer (PO-5a, acid value 3 mg KOH/g, number average molecular weight 60,000, weight average molecular weight 200,000, Tm 80° C., ΔH 25 J/g, carboxylic anhydride group (a1)/carboxylic acid group bond ratio (a2)=90/10, total amount of (a1) and (a2) in the total acid components 100 mol%).
Next, PO-5a was left to stand in a desiccator at 30° C. and RH 70% for one week to obtain P0-5b, which had a carboxylic anhydride group (a1)/carboxylic acid group (a2) bond ratio of 18/82.

Production Example 6 (Production of acid-modified polyolefin PO-6a)
Propylene-butene copolymer (Mitsui Chemicals, Inc. "Tafmer (registered trademark) XM7080") 100 parts by mass, maleic anhydride 20 parts by mass, acrylic acid 5 parts by mass, di-tert-butyl peroxide 6 parts by mass were kneaded and reacted using a twin-screw extruder with the maximum temperature of the cylinder set to 170 ° C. Thereafter, degassing was performed under reduced pressure in the extruder, and the remaining unreacted material was removed to obtain a maleic anhydride acrylic acid modified propylene-butene copolymer (PO-6a, acid value 30 mg KOH / g, number average molecular weight 25,000, weight average molecular weight 80,000, Tm 75 ° C., ΔH 30 J / g, carboxylic anhydride group (a1) / carboxylic acid group bond ratio (a2) = 89 / 11, total amount of (a1) and (a2) in the total acid component 70 mol%) was obtained.
Next, PO-6a was left to stand in a desiccator under an environment of 30° C. and RH 70% for one week to obtain P0-6b, which had a carboxylic anhydride group (a1)/carboxylic acid group (a2) bond ratio of 14/86.

Preparation Example 1 (Cyclization reaction of acid-modified polyolefin PO-1c1)
In a four-neck flask equipped with a Dean-Stark apparatus and a stirrer, 100 parts by mass of PO-1b and 500 parts by mass of toluene were charged and reacted under reflux for 5 hours. After cooling, the mixture was poured into a container containing a large amount of methyl ethyl ketone to precipitate a resin (PO-1c1). PO-1c1 had an acid value of 25 mg KOH/g, a number average molecular weight of 25,000, a weight average molecular weight of 80,000, a Tm of 75°C, a ΔH of 30 J/g, a bond ratio (a2) of carboxylic anhydride group (a1)/carboxylic acid group of 100/0, and a total amount of (a1) and (a2) in the total acid components of 100 mol%.

Preparation Examples 2 to 9 (Cyclization reaction of acid-modified polyolefins PO-1c2 to PO-6c1)
Preparation Examples 2 to 9 were carried out in the same manner as Preparation Example 1, except that the type of acid-modified polyolefin and the reflux time were changed as shown in Table 1. The physical properties are shown in Table 1.

Example 1
An adhesive composition was obtained by blending 100 parts by mass of PO-1c1 as the component (A), 0.1 parts by mass of B11-1, 8 parts by mass of B12-1 as the component (B1), and 432 parts by mass (solid content concentration: 20% by mass) of an organic solvent (methylcyclohexane/methyl ethyl ketone/toluene=72/8/20 (v/v)). The blending amounts, adhesive strength, solder heat resistance, pot life, and electrical properties are shown in Table 1.

Examples 2 to 35, Comparative Examples 1 to 15
The amounts of components (A) to (C) were changed as shown in Tables 2 to 4, and Examples 2 to 35 and Comparative Examples 1 to 15 were carried out in the same manner as in Example 1. The evaluation results of adhesive strength, solder heat resistance, electrical properties, and pot life are shown in Tables 2 to 4. The organic solvent (methylcyclohexane/methyl ethyl ketone/toluene=72/8/20 (v/v)) was adjusted so that the solids concentration was 20 mass %.

The epoxy resin (B1), isocyanate compound (B2), carbodiimide compound (B3), and oligophenylene ether (C) used in Tables 2 to 4 are as follows.
<Epoxy resin (B1)>
<Glycidylamine-type epoxy resin (B11)>
B11-1: N,N,N',N'-tetraglycidyl-m-xylylenediamine: TETRAD (registered trademark)-X (manufactured by Mitsubishi Gas Chemical Company, Inc.)
<Glycidyl ether type epoxy resin (B12)>
B12-1: Phenol novolac type epoxy resin: jER (registered trademark) 152 (manufactured by Mitsubishi Chemical Corporation)
B12-2: o-cresol novolac type epoxy resin: YDCN-700-3 (manufactured by Nippon Steel Sumikin Chemical Co., Ltd.)
<Alicyclic epoxy resin (B13)>
B13-1: Dicyclopentadiene type epoxy resin: HP-7200H (manufactured by DIC Corporation, epoxy equivalent: 278 g/eq)
<Isocyanate compound (B2)>
B21: Isocyanurate of hexamethylene diisocyanate: Sumidur (registered trademark) N-3300 (manufactured by Bayer)
B22: Biuret form of hexamethylene diisocyanate: Duranate (registered trademark) 24A-100 (manufactured by Asahi Kasei Chemicals Corporation)
<Carbodiimide compound (B3)>
B31: Multifunctional carbodiimide: Carbodilite (registered trademark) V-09 (manufactured by Nisshinbo Chemical Co., Ltd.)
B32: Multifunctional carbodiimide: Carbodilite (registered trademark) V-03 (manufactured by Nisshinbo Chemical Co., Ltd.)
<Oligophenylene ether (C)>
C1: Modified oligophenylene ether styrene: OPE-2St 2200 (manufactured by Mitsubishi Gas Chemical Company, Inc., a compound having the structure of general formula (4) of Mn2000)
C2: Oligophenylene ether: SA90 (a compound having the structure of general formula (3) of Mn1800 manufactured by SABIC Corporation)

As is clear from Tables 2 to 4, in Examples 1 to 35, all of the adhesiveness, solder heat resistance, pot life, and dielectric properties are good. In contrast, in Comparative Examples 1, 6, and 11, the ratio of carboxylic anhydride group (a1)/carboxylic acid group (a2) was low, so the adhesiveness between the liquid crystal polymer and the copper foil, the solder heat resistance, and the pot life were reduced. In Comparative Examples 2, 7, and 12, the acid value of the acid-modified polyolefin (A) was high, so the solder heat resistance and the pot life were reduced. In Comparative Examples 3, 8, and 13, the acid value of the acid-modified polyolefin (A) was low, so the adhesiveness between the liquid crystal polymer and the copper foil and the solder heat resistance were reduced. In Comparative Examples 4, 9, and 14, the total amount of the carboxylic anhydride group (a1) and the carboxylic acid group (a2) was low, so the solder heat resistance and the pot life were reduced. In Comparative Examples 5, 10, and 15, since none of the epoxy resin (B1), the isocyanate compound (B2), and the carbodiimide compound (B3) was contained, the solder heat resistance was reduced.

The adhesive composition of the present invention has excellent adhesion not only to polyimide but also to non-polar resin substrates such as liquid crystal polymers and metal substrates such as copper foil. It also has excellent solder heat resistance and low dielectric properties, and is excellent in pot life. The adhesive composition of the present invention can be used to obtain an adhesive sheet and a laminate bonded therewith. Due to the above characteristics, it is useful for flexible printed wiring board applications, particularly FPC applications requiring low dielectric properties (low dielectric constant, low dielectric tangent) in the high frequency range.

Claims (11)

An adhesive composition for printed wiring boards comprising an acid-modified polyolefin (A) that satisfies the following (1) to (3), and further comprising at least one selected from the group consisting of an epoxy resin (B1), an isocyanate compound (B2) and a carbodiimide compound (B3) ,
The adhesive composition for printed wiring boards is prepared by blending a mixed solvent of methylcyclohexane, methyl ethyl ketone, and toluene (methylcyclohexane/methyl ethyl ketone/toluene=72/8/20 (v/v)) to a solid content concentration of 20% by mass,
When the solution viscosity was measured at 25° C. using a Brookfield viscometer (rotor No. 2, rotation speed 60 rpm),
An adhesive composition for printed wiring boards, in which ηB/ηB0 is 0.5 or more and less than 3.0, where ηB0 is the solution viscosity immediately after blending and ηB is the solution viscosity after 7 days of storage .
(1) The acid value is 5 to 50 mgKOH/g. (2) The bonding ratio (molar ratio) of the carboxylic anhydride group represented by formula (a1) to the carboxylic acid group represented by formula (a2) is formula (a1)/formula (a2)=100/0 to 91/9 . (3) When the total acid component bonded to the acid-modified polyolefin (A) is taken as 100 mol %, the total amount of the formulas (a1) and (a2) is 90 mol % or more.
[In formula (a1) and formula (a2), * represents a bond bonded to the acid-modified polyolefin (A).] 2. The adhesive composition for printed wiring boards according to claim 1, wherein the epoxy resin (B) is a mixture containing a glycidyl amine type epoxy resin (B1) and further containing one or more resins selected from the group consisting of a glycidyl ether type resin (B2) and an alicyclic type epoxy resin (B3). 2. The adhesive composition for printed wiring boards according to claim 1, wherein the isocyanate compound (B2) is a polyfunctional isocyanate compound. 2. The adhesive composition for printed wiring boards according to claim 1, wherein the carbodiimide compound (B3) is a polyfunctional carbodiimide compound. The adhesive composition for printed wiring boards according to any one of claims 1 to 4, further comprising an oligophenylene ether (C). The adhesive composition for printed wiring boards according to any one of claims 1 to 5, further comprising an organic solvent. 7. The adhesive composition for printed wiring boards according to claim 1, which has a relative dielectric constant (εc) of 3.0 or less and a dielectric loss tangent (tan δ) of 0.02 or less at 1 GHz. 8. An adhesive sheet for printed wiring boards, comprising the adhesive composition for printed wiring boards according to claim 1. A laminate for printed wiring boards , comprising the adhesive composition for printed wiring boards according to any one of claims 1 to 7. A printed wiring board comprising the laminate for printed wiring boards according to claim 9 as a component. A cover film containing the printed wiring board according to claim 10 as a component.