JP7707912B2 - 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 widely 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 relative dielectric constant, low dielectric loss 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 an adhesive, a combination of polyimide and epoxy resin using dimer diamine has been developed (Patent Document 1).

JP 2018-44136 A

However, terminals such as smartphones are used in humid environments, and it has been found that in an adhesive using polyimide as in Patent Document 1, polyimide absorbs moisture over time, and the dielectric tangent in a hygroscopic state deteriorates. Therefore, as in Patent Document 1, it has been found that if a resin has high hygroscopicity, the adhesive properties, solder heat resistance, dielectric properties (relative dielectric constant, dielectric tangent), and dielectric tangent after moisture absorption (hereinafter also referred to as saturated water absorption) of an adhesive containing that resin are insufficient.

Means for Solving the Problems As a result of extensive research into solving the above problems, the present inventors have found that an adhesive composition containing an acid-modified polyolefin (a) and an epoxy resin (b) exhibits excellent adhesion between a resin substrate and a metal substrate, solder heat resistance, and low dielectric properties (dielectric constant, dielectric tangent), and further exhibits excellent dielectric tangent after moisture absorption (saturation water absorption), 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 is also excellent in solder heat resistance, dielectric properties, and dielectric tangent after moisture absorption (saturated water absorption).

An adhesive composition comprising an acid-modified polyolefin (a) and an epoxy resin (b), the adhesive composition satisfying the following (1) and (2):
(1) The cured product of the adhesive composition has a relative dielectric constant (ε _c 1) of 3.0 or less and a dielectric loss tangent (tan δ1) of 0.02 or less at 1 GHz immediately after curing. (2) The change in the dielectric loss tangent (tan δ1) at 1 GHz immediately after curing of the cured product of the adhesive composition and the dielectric loss tangent (tan δ2) at 1 GHz after immersion in water at 25° C. for 24 hours is 0.01 or less.

The acid-modified polyolefin (a) preferably has an acid value of 5 to 40 mgKOH/g. The acid-modified polyolefin (a) preferably contains 1 to 40 parts by mass of an epoxy resin (b) relative to 100 parts by mass of the acid-modified polyolefin (a), and further preferably contains an oligophenylene ether (c) and/or a carbodiimide compound (d).

An adhesive sheet or laminate having a layer containing the adhesive composition. A printed wiring board comprising the laminate as a component.

The adhesive composition of the present invention has good adhesion to both various resin substrates, such as not only polyimide but also liquid crystal polymers, and metal substrates, and is stable with solder heat resistance, low dielectric properties, and little change in dielectric tangent after moisture absorption (saturation water absorption).

<Acid-modified polyolefin (a)>
The acid-modified polyolefin (a) (hereinafter also simply referred to as component (a)) used in the present invention is not limited, but is preferably one obtained by grafting at least one of α,β-unsaturated carboxylic acid and its acid 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. In other words, the acid-modified polyolefin is preferably one obtained by grafting at least one of α,β-unsaturated carboxylic acid and its acid 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. 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 at least one of α,β-unsaturated carboxylic acids and their acid anhydrides include maleic acid, itaconic acid, citraconic acid, and their acid anhydrides. Among these, acid anhydrides are preferred, and maleic anhydride is more preferred. Specific examples include maleic anhydride-modified polypropylene, maleic anhydride-modified propylene-ethylene copolymer, maleic anhydride-modified propylene-butene copolymer, maleic anhydride-modified propylene-ethylene-butene copolymer, and the like. These acid-modified polyolefins can be used alone or in combination of two or more.

From the viewpoint of heat resistance and adhesion to resin substrates and metal substrates, the acid value of the acid-modified polyolefin (a) is preferably 5 mgKOH/g or more, more preferably 6 mgKOH/g or more, and even more preferably 7 mgKOH/g or more. By making it equal to or greater than the lower limit, compatibility with the epoxy resin (b) is improved, and excellent adhesive strength can be exhibited. In addition, the crosslinking density is high and heat resistance is good. Furthermore, the dielectric tangent after moisture absorption (saturation water absorption) hardly increases. The upper limit is preferably 40 mgKOH/g or less, more preferably 35 mgKOH/g or less, and even more preferably 30 mgKOH/g or less. By making it equal to or less than the upper limit, adhesion and dielectric tangent after saturated water absorption are improved.

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 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 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 most 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 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 is to become 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 (b)>
The epoxy resin (b) (hereinafter, also simply referred to as component (b)) used in the present invention is not particularly limited as long as it has an epoxy group in the molecule, but preferably has two or more glycidyl groups in the molecule. Specifically, although not particularly limited, at least one selected from the group consisting of biphenyl type epoxy resin, naphthalene type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, novolac type epoxy resin, alicyclic epoxy resin, dicyclopentadiene type epoxy resin, tetraglycidyl diaminodiphenylmethane, triglycidyl paraaminophenol, tetraglycidyl bisaminomethylcyclohexanone, N,N,N',N'-tetraglycidyl-m-xylylenediamine, and epoxy-modified polybutadiene can be used. Preferably, it is a biphenyl type epoxy resin, a novolac type epoxy resin, a dicyclopentadiene type epoxy resin, or an epoxy-modified polybutadiene. More preferably, it is a dicyclopentadiene type epoxy resin.

The epoxy equivalent of the epoxy resin (b) 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 keeping it within the above range, excellent solder heat resistance can be exhibited.

In the adhesive composition of the present invention, the content of the epoxy resin (b) is preferably 0.5 parts by mass or more, 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, relative to 100 parts by mass of the acid-modified polyolefin (a). By making it equal to or more than the lower limit, a sufficient curing effect can be obtained, and excellent adhesiveness and solder heat resistance can be expressed. In addition, 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. By making it equal to or less than the upper limit, the dielectric properties of the adhesive composition become good. That is, by making it within the above range, an adhesive composition having excellent adhesiveness, solder heat resistance, low dielectric properties, and dielectric loss tangent after saturated water absorption can be obtained.

<Adhesive Composition>
The adhesive composition of the present invention is a composition containing at least an acid-modified polyolefin (a) and an epoxy resin (b), and preferably further contains an oligophenylene ether (c) and/or a carbodiimide compound (d). 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 is also excellent in solder heat resistance, electrical properties (low dielectric properties), and dielectric loss tangent after moisture absorption (saturated water absorption). That is, the adhesive composition is applied to a substrate, and the adhesive coating film (adhesive layer) after curing can exhibit excellent electrical properties.

The adhesive composition according to the present invention has a relative dielectric constant (ε _c 1) at a frequency of 1 GHz immediately after curing of 3.0 or less, preferably 2.6 or less, and more preferably 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 1) 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 has a dielectric loss tangent (tan δ1) at a frequency of 1 GHz immediately after curing of 0.02 or less. It is preferably 0.01 or less, and more preferably 0.008 or less. There is no particular lower limit, but in practical use it is 0.0001. Furthermore, the dielectric loss tangent (tan δ1) 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 1) at a frequency of 1 GHz of the adhesive composition layer after peeling is measured. Specifically, the dielectric constant (ε _c 1) and the dielectric loss tangent (tan δ1) can be calculated from the measurement by the cavity resonator perturbation method. Here, "immediately after curing" means within 30 minutes after heat treatment curing.

The adhesive composition according to the present invention shows almost no increase in dielectric tangent even after the cured product of the adhesive composition is allowed to absorb moisture (saturated water absorption). Specifically, the change between the dielectric tangent (tan δ1) at 1 GHz immediately after curing and the dielectric tangent (tan δ2) at 1 GHz of the cured product after immersion in water at 25°C for 24 hours after curing is 0.01 or less. It is preferably 0.008 or less, and more preferably 0.005 or less. The lower limit may be industrially 0.0001 or more, and may be 0.001 or more. The change is the difference between (tan δ1) and (tan δ2), and can be calculated by the change=|(tan δ1)-(tan δ2)|.

It is preferable that the adhesive composition according to the present invention shows almost no increase in the dielectric constant even after the cured product of the adhesive composition is allowed to absorb moisture (saturated water absorption). Specifically, it is preferable that the dielectric constant (ε _c 2) at a frequency of 1 GHz after the cured product of the adhesive composition is allowed to absorb moisture (saturated water absorption) is 3.0 or less. It is more preferable that it is 2.6 or less, and even more preferable that it is 2.3 or less. There is no particular restriction on the lower limit, but in practical use it is 2.0. Moreover, it is preferable that the dielectric constant (ε _c 2) in the entire frequency range of 1 GHz to 60 GHz is 3.0 or less, more preferably 2.6 or less, and even more preferably 2.3 or less.

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.

<Oligophenylene ether (c)>
By including the oligophenylene ether (c) in the adhesive composition of the present invention, it is possible to achieve even better solder heat resistance. Furthermore, by including the oligophenylene ether (c), it is possible to suppress an increase in the dielectric tangent after moisture absorption. 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 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 polyphenylene 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.

When the oligophenylene ether (c) is contained, its content 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.

<Carbodiimide Compound (d)>
The carbodiimide compound (d) used in the present invention (hereinafter also simply referred to as component (d)) is preferably a polyfunctional carbodiimide compound having two or more carbodiimide groups in one molecule. By using the carbodiimide compound (d), 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.

When the carbodiimide compound (d) is contained, its content 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 1.5 parts by mass or more, and particularly preferably 2 parts by mass or more. In addition to adhesiveness and solder heat resistance, it has excellent low dielectric properties, so it is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less.

The carbodiimide compound (d) 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 compound or an alicyclic carbodiimide compound is preferred.

<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 (b), the oligophenylene ether (c) and the carbodiimide compound (d). Specific examples of such solvents include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as hexane, heptane, octane, and decane; alicyclic hydrocarbons such as cyclohexane, cyclohexene, methylcyclohexane, and ethylcyclohexane; halogenated hydrocarbons such as trichloroethylene, dichloroethylene, chlorobenzene, and chloroform; alcohol-based solvents such as methanol, ethanol, isopropyl alcohol, butanol, pentanol, hexanol, propanediol, and phenol; ketone-based solvents such as acetone, methyl isobutyl ketone, methyl ethyl ketone, pentanone, hexanone, cyclohexanone, isophorone, and acetophenone; cellosolves such as methyl cellosolve and ethyl cellosolve; ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, methyl propionate, and butyl formate; ethylene glycol mono-n-butyl ether, ethylene glycol mono-iso-butyl ether, ethylene glycol mono-tert-butyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-iso-butyl ether, triethylene glycol mono-n-butyl ether, tetraethylene glycol mono-n-butyl ether, One or more of these may be used in combination. Methylcyclohexane and toluene are particularly preferred from the viewpoints of work 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 (e1) selected from the group consisting of aromatic hydrocarbons, aliphatic hydrocarbons, alicyclic hydrocarbons, and halogenated hydrocarbons, and one or more solvents (e2) 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 (e1)/solvent (e2)=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 (e1) is an aromatic hydrocarbon or an alicyclic hydrocarbon, and the solvent (e2) 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 two or more may be used in any combination. 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 (d). 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 (d). 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 relative to 100 parts by mass of the total of components (a) to (d). 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 thereof 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 (d). 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 according to 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.

(Physical property evaluation method)

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.

Number average molecular weight (Mn)
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.

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.

(1) 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

(2) 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 and then floated in a molten solder bath at 280° C. for 10 seconds to check for any changes in appearance, such as blistering.
<Evaluation criteria>
◎: No blistering ○: Some blistering △: Many blistering ×: Blistering and discoloration

(3) Dielectric constant (ε _c 1) and dielectric tangent (tan δ 1) immediately after curing
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 x 3 mm to obtain a test sample. The relative dielectric constant (ε _c 1) and dielectric loss tangent (tan δ1) 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 measurement was performed within 1 hour after the heat treatment and curing. 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 (4) Dielectric tangent (tan δ2) after saturation water absorption
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. Next, the test adhesive resin sheet was immersed in water at 25 ° C and left for 24 hours. Thereafter, the moisture on the surface was wiped off, and the obtained test adhesive resin sheet was cut into a rectangular sample of 8 cm x 3 mm to obtain a test sample. The relative dielectric constant (ε _c 2) and dielectric loss tangent (tan δ2) were measured using a network analyzer (manufactured by Anritsu Corporation) by a cavity resonator perturbation method at a temperature of 23 ° C and a frequency of 1 GHz. The change in the dielectric loss tangent (tan δ1) immediately after curing and the dielectric loss tangent (tan δ2) after saturated water absorption were calculated and evaluated by the following formula.
Amount of change=|(tan δ1)-(tan δ2)|
<(Evaluation Criteria for Dielectric Tangent Change)>
◎: 0.002 or less 〇: More than 0.002 and 0.005 or less △: More than 0.005 and 0.01 or less ×: More than 0.01

Example 1
A mixed solution was obtained by mixing 100 parts by mass of CO-1, 10 parts by mass of epoxy resin HP-7200H, and 440 parts by mass (solid content concentration: 20% by mass) of an organic solvent (methylcyclohexane/methyl ethyl ketone/toluene=72/8/20 (v/v)). The mixing amounts, adhesive strength, solder heat resistance, electrical properties immediately after curing, and rate of change in dielectric tangent after saturated water absorption are shown in Table 1.

Examples 2 to 16
Examples 2 to 16 were carried out in the same manner as Example 1, except that the blending amounts of components (a) to (d) were changed as shown in Table 1. The adhesive strength, solder heat resistance, electrical properties immediately after curing, and change in dielectric tangent after saturated water absorption are shown in Table 1. The organic solvent (methylcyclohexane/methyl ethyl ketone/toluene=72/8/20 (v/v)) was adjusted so that the solids concentration was 20 mass %.

Comparative Examples 1 to 3
The amounts of components (a) to (d) were changed as shown in Table 1, and Comparative Examples 1 to 3 were carried out in the same manner as in Example 1. Table 1 shows the adhesive strength, solder heat resistance, electrical properties immediately after curing, and rate of change in dielectric tangent after saturation water absorption.

The acid-modified polyolefin (a), epoxy resin (b), oligophenylene ether (c) and carbodiimide compound (d) used in Table 1 are as follows.
(Epoxy resin (b))
Dicyclopentadiene type epoxy resin: HP-7200 (manufactured by DIC Corporation, epoxy equivalent: 259 g/eq)
Dicyclopentadiene type epoxy resin: HP-7200H (manufactured by DIC Corporation, epoxy equivalent: 278 g/eq)
Cresol novolac epoxy resin: jER-152 (manufactured by Mitsubishi Chemical, epoxy equivalent: 177 g/eq.
Epoxy-modified polybutadiene resin: JP-100 (manufactured by Nippon Soda Co., Ltd., epoxy equivalent: 200 g/eq)
(Oligophenylene ether (c))
Modified oligophenylene ether styrene: OPE-2St 1200 (manufactured by Mitsubishi Gas Chemical Company, Inc., Mn1000, compound having the structure of general formula (c4))
Modified oligophenylene ether styrene: OPE-2St 2200 (manufactured by Mitsubishi Gas Chemical Company, Inc., Mn2000, compound having the structure of general formula (c4))
Oligophenylene ether: SA90 (a compound having the structure of general formula (c3) of Mn1800 manufactured by SABIC Corporation)
(Carbodiimide Compound (d))
Carbodiimide resin: V-09GB (manufactured by Nisshinbo Chemical Co., Ltd., carbodiimide equivalent: 216 g/eq)
Carbodiimide resin: V-03 (manufactured by Nisshinbo Chemical Co., Ltd., carbodiimide equivalent: 209 g/eq)

(Acid-modified polyolefin (a))
Production Example 1
In a 1L autoclave, 100 parts by mass of propylene-butene copolymer (Mitsui Chemicals "Tafmer (registered trademark) XM7080"), 150 parts by mass of toluene, 19 parts by mass of maleic anhydride, and 6 parts by mass of di-tert-butyl peroxide were added, and the temperature was raised to 140 ° C., and then the mixture was stirred for another 3 hours. Thereafter, the resulting reaction liquid was cooled and poured into a container containing a large amount of methyl ethyl ketone to precipitate a resin. Thereafter, the liquid containing the resin was centrifuged to separate and purify the acid-modified propylene-butene copolymer in which maleic anhydride was graft-polymerized, (poly)maleic anhydride, and low molecular weight substances. Thereafter, the mixture was dried under reduced pressure at 70 ° C. for 5 hours to obtain a maleic anhydride-modified propylene-butene copolymer (CO-1, acid value 19 mg KOH / g, number average molecular weight 25,000, Tm 80 ° C., ΔH 35 J / g).

Production Example 2
A maleic anhydride-modified propylene-butene copolymer (CO-2, acid value 14 mgKOH/g, number average molecular weight 30,000, Tm 78°C, ΔH 25 J/g) was obtained in the same manner as in Production Example 1, except that the amount of maleic anhydride added was changed to 14 parts by mass.

Production Example 3
A maleic anhydride-modified propylene-butene copolymer (CO-3, acid value 11 mgKOH/g, number average molecular weight 33,000, Tm 80°C, ΔH 25 J/g) was obtained in the same manner as in Production Example 1, except that the amount of maleic anhydride added was changed to 11 parts by mass.

Production Example 4
A maleic anhydride-modified propylene-butene copolymer (CO-4, acid value 7 mgKOH/g, number average molecular weight 35,000, Tm 82°C, ΔH 25 J/g) was obtained in the same manner as in Production Example 1, except that the amount of maleic anhydride added was changed to 6 parts by mass.

Production Example 5
A maleic anhydride-modified propylene-butene copolymer (CO-5, acid value 4 mg KOH/g, number average molecular weight 37,000, Tm 84°C, ΔH 25 J/g) was obtained in the same manner as in Production Example 1, except that the amount of maleic anhydride added was changed to 3 parts by mass.

As is clear from Table 1, in Examples 1 to 16, the adhesiveness, solder heat resistance, electrical properties immediately after curing, and the amount of change in dielectric tangent after saturation water absorption were all good. In contrast, in Comparative Example 1, the dielectric tangent immediately after curing and the amount of change in dielectric tangent after saturation water absorption were poor. This is thought to be due to the high ratio of epoxy resin (b). In Comparative Example 2, since it does not contain acid-modified polyolefin (a), the electrical properties immediately after curing and the amount of change in dielectric tangent after saturation water absorption were poor. In Comparative Example 3, since it does not contain epoxy resin (b), 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 dielectric tangent after saturated water absorption. 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 relative dielectric constant, low dielectric tangent) in the high frequency range.

Claims (5)

An adhesive composition comprising an acid-modified polyolefin (a) and an epoxy resin (b),
The acid value of the acid-modified polyolefin (a) is 5 to 40 mgKOH/g;
The epoxy resin (b) is contained in an amount of 0.5 parts by mass or more and 60 parts by mass or less relative to 100 parts by mass of the acid-modified polyolefin (a),
Further containing an oligophenylene ether (c),
An adhesive composition that satisfies the following (1) and (2):
(1) The cured product of the adhesive composition has a relative dielectric constant (εc1) of 3.0 or less and a dielectric loss tangent (tan δ1) of 0.02 or less at 1 GHz immediately after curing. (2) The change between the dielectric loss tangent (tan δ1) at 1 GHz immediately after curing of the cured product of the adhesive composition and the dielectric loss tangent (tan δ2) at 1 GHz after immersion in water at 25° C. for 24 hours is 0.01 or less. The adhesive composition according to claim 1 , further comprising a carbodiimide compound (d) . An adhesive sheet having a layer containing the adhesive composition according to claim 1 or 2 . A laminate having a layer containing the adhesive composition according to claim 1 or 2 . A printed wiring board comprising the laminate according to claim 4 as a component.