TWI846969B - Polyolefin adhesive composition - Google Patents

Abstract

An adhesive composition is provided which has high adhesion between a non-polar resin substrate like a liquid crystal polymer and a metal substrate, solder heat resistance, and low dielectric properties, and also has excellent dielectric tangent after saturated water absorption.

Description

Polyolefin adhesive composition

The present invention relates to a polyolefin adhesive composition. More specifically, it relates to a polyolefin adhesive composition used for bonding between resin substrates or metal substrates. In particular, it relates to an adhesive composition for a flexible printed circuit board (hereinafter referred to as FPC), and a cover film, a laminate, a copper foil with a resin, and a bonding sheet containing the same.

Flexible printed circuit boards (FPCs) have excellent flexibility and can cope with the multifunctionality and miniaturization of personal computers (PCs) and smart phones. Therefore, they are frequently used to embed electronic circuit boards into narrow and complex interiors. In recent years, electronic equipment has been miniaturized, lightweight, high-density, and high-power. Due to their popularity, the performance requirements of wiring boards (electronic circuit boards) have gradually increased. In particular, with the increase in the speed of FPC transmission signals, the frequency of signals has increased. Along with this, the requirements for low dielectric properties (low relative dielectric constant, low dielectric tangent) of FPC in the high-frequency region have increased. In this way, in order to achieve low dielectric properties, strategies have been adopted to reduce the dielectric loss of the FPC base material and adhesive. As for adhesives, a combination of polyimide using dimer diamine and epoxy resin has been developed (Patent Document 1). [Prior Art Document] [Patent Document]

[Patent Document 1] Japanese Patent Application Publication No. 2018-44136

[The problem that the invention wants to solve]

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

The present invention has been studied to solve the above problems. As a result, it is found that the adhesive composition containing acid-modified polyolefin (a) and epoxy resin (b) exhibits excellent adhesion between the resin substrate and the metal substrate, solder heat resistance, and low dielectric properties (relative dielectric constant, dielectric tangent), and the dielectric tangent after moisture absorption (saturated water absorption) is also excellent, thereby completing the present invention.

That is, the purpose of the present invention is to provide an adhesive composition having good adhesion to various resin substrates such as liquid crystal polymer (LCP) and metal substrates, and having excellent solder heat resistance, dielectric properties, and dielectric tangent after moisture absorption (saturated water absorption). [Means for solving the problem]

An adhesive composition comprising an acid-modified polyolefin (a) and an epoxy resin (b) is characterized by satisfying the following (1)-(2): (1) the relative dielectric constant (ε _c 1) of the cured adhesive composition at 1 GHz is less than 3.0 and the dielectric tangent (tan δ1) is less than 0.02 when the cured adhesive composition is just cured; (2) the change in the dielectric tangent (tan δ1) of the cured adhesive composition at 1 GHz when the cured adhesive composition is just cured and the dielectric tangent (tan δ2) at 1 GHz after immersion in water at 25°C for 24 hours is less than 0.01.

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

An adhesive sheet or laminate having a layer containing the above-mentioned adhesive composition. A printed circuit board including the above-mentioned laminate as a constituent element. [Effect of the invention]

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

<Acid-modified polyolefin (a)> The acid-modified polyolefin (a) (hereinafter, also referred to as component (a)) used in the present invention is not limited, and is preferably obtained by grafting at least one of α,β-unsaturated carboxylic acid and its anhydride to a polyolefin resin. The so-called polyolefin resin refers to a polymer with a hydrocarbon skeleton as the main component, such as ethylene, propylene, butene, butadiene, isoprene, etc., obtained by single polymerization or copolymerization with other monomers, and hydrogenated products, halogenated products, etc. of the obtained polymer. That is, the acid-modified polyolefin is preferably obtained by grafting at least one of α,β-unsaturated carboxylic acid and its anhydride onto at least one of polyethylene, polypropylene and propylene-α-olefin copolymer.

Propylene-α-olefin copolymer is a copolymer made of propylene as the main component and α-olefin. As for α-olefin, 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 particularly preferred. The ratio between the propylene component and the α-olefin component of 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.

As for at least one of the α,β-unsaturated carboxylic acids and their anhydrides, maleic acid, itaconic acid, liconaconic acid and their anhydrides can be cited. Among these, the anhydrides are particularly preferred, and maleic anhydride is more preferred. Specifically, maleic anhydride-modified polypropylene, maleic anhydride-modified propylene-ethylene copolymer, maleic anhydride-modified propylene-butene copolymer, maleic anhydride-modified propylene-ethylene-butene copolymer, etc. can be cited. One of these acid-modified polyolefins can be used or two or more of them can be used in combination.

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, from the viewpoint of heat resistance, adhesion to resin substrates, and adhesion to metal substrates. If it is above the above lower limit, the compatibility with the epoxy resin (b) will be good, and excellent bonding strength can be exhibited. In addition, the crosslinking density will be higher and the heat resistance will be good. Then, the dielectric tangent after moisture absorption (saturated water absorption) will hardly increase. 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. If it is below the above upper limit, the adhesion and the dielectric tangent after saturated water absorption will be good.

The number average molecular weight (Mn) of the acid-modified polyolefin (a) is preferably in the range of 10,000 to 50,000. The range of 15,000 to 45,000 is more preferred, the range of 20,000 to 40,000 is even more preferred, and the range of 22,000 to 38,000 is particularly preferred. If it is above the lower limit, the cohesion will be good and excellent adhesion can be exhibited. If it is below the upper limit, the fluidity will be excellent and the workability will be good.

The acid-modified polyolefin (a) is preferably a crystalline acid-modified polyolefin. The so-called crystalline in the present invention means that when the temperature is raised from -100°C to 250°C at 20°C/min using a differential scanning calorimeter (DSC), a clear melting peak is displayed during the temperature rise process.

The melting point (Tm) of the acid-modified polyolefin (a) is preferably in the range of 50°C to 120°C. The range of 60°C to 100°C is more preferably, and the range of 70°C to 90°C is most preferably. If it is above the lower limit, the cohesion from the crystallization will be good, and excellent adhesion and heat resistance can be exhibited. If it is below the upper limit, the solution stability and fluidity will be excellent, and the workability during bonding will be 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. The range of 10 J/g to 50 J/g is more preferably, and the range of 20 J/g to 40 J/g is most preferably. If it is above the lower limit, the cohesive force derived from the crystallization will be good, and excellent adhesion and heat resistance can be exhibited. If it is below the upper limit, the solution stability and fluidity will be excellent, and the workability during bonding will be good.

There is no particular limitation on the method for producing the acid-modified polyolefin (a), and examples thereof include free radical grafting reaction (i.e., a reaction in which free radical species are generated for a polymer that becomes a main chain, and the free radical species are used as a polymerization starting point to carry out graft polymerization with an unsaturated carboxylic acid or anhydride).

The free radical initiator is not particularly limited, and an organic peroxide is preferably used. The organic peroxide is not particularly limited, and examples thereof include peroxides such as di-tert-butyl peroxyphthalate, tert-butyl alcohol peroxide, diisopropylbenzene peroxide, benzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxy-2-ethylhexanoate, tert-butyl peroxypivalate, methyl ethyl ketone peroxide, di-tert-butyl peroxide, and lauryl peroxide; and azonitriles such as azobisisobutylonitrile and azobisisopropionitrile.

<Epoxy resin (b)> The epoxy resin (b) (hereinafter also 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, without particular limitation, 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, tetracyclyl diamino diphenyl methane, tricyclyl p-aminophenol, tetracyclyl diamino methyl cyclohexanone, N,N,N',N'-tetracyclyl-m-xylene diamine, and epoxy-modified polybutadiene can be used. Preferably, the epoxy resin is a biphenyl type epoxy resin, a novolac type epoxy resin, a dicyclopentadiene type epoxy resin or an epoxy-modified polybutadiene. More preferably, the epoxy resin 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. Furthermore, it is preferably 400 g/eq or less, more preferably 350 g/eq or less, and even more preferably 300 g/eq or less. When it is 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, 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). If it is above the above lower limit, a sufficient curing effect can be obtained, and excellent adhesion and solder heat resistance can be exhibited. In addition, it is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and particularly preferably 35 parts by mass or less. If it is below the above upper limit, the dielectric properties of the adhesive composition will become good. That is, if it is within the above range, an adhesive composition having excellent adhesion, solder heat resistance, low dielectric properties, and dielectric 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 contains oligophenylene ether (c) and/or a carbodiimide compound (d). The adhesive composition of the present invention has excellent adhesion to low-polarity resin substrates such as liquid crystal polymers of polyimide and metal substrates, and also has excellent solder heat resistance, electrical properties (low dielectric properties) and dielectric tangent after moisture absorption (saturated water absorption). That is, the adhesive film (adhesive layer) formed after the adhesive composition is applied to the substrate and cured can exhibit excellent electrical properties.

The adhesive composition of the present invention has a relative dielectric constant (ε _c 1) of 3.0 or less at a frequency of 1 GHz when it is just cured. It is preferably 2.6 or less, and more preferably 2.3 or less. The lower limit is not particularly limited, and is 2.0 in practical use. Moreover, the relative dielectric constant (ε _c 1) in the entire frequency range of 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 of the present invention has a dielectric tangent (tanδ1) of 0.02 or less at a frequency of 1 GHz when it is just cured. It is preferably 0.01 or less, and more preferably 0.008 or less. The lower limit is not particularly limited, and is 0.0001 in practical use. Moreover, the dielectric tangent (tanδ1) in 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 relative dielectric constant (ε _c ) and the dielectric tangent (tan δ) can be measured in the following manner. That is, the adhesive composition can be applied to the release substrate in such a manner that the thickness after drying is 25 μm, and dried at about 130° C. for about 3 minutes. Then, it is hardened by heat treatment at about 140° C. for about 4 hours, and the hardened adhesive composition layer (adhesive layer) is peeled off from the release film. The relative dielectric constant (ε _c 1) of the adhesive composition layer after peeling is measured at a frequency of 1 GHz. Specifically, the relative dielectric constant (ε _c 1) and the dielectric tangent (tan δ1) can be calculated from the measurement using the cavity resonator perturbation method. Here, the so-called just-hardened period refers to within 30 minutes after heat treatment hardening.

The adhesive composition of the present invention hardly shows an increase in dielectric tangent even after the cured adhesive composition is allowed to absorb moisture (saturated water absorption). Specifically, the change in dielectric tangent (tanδ1) at 1 GHz just after curing and the dielectric tangent (tanδ2) at 1 GHz after immersion in water at 25°C for 24 hours after curing is less than 0.01. It is more ideal to be less than 0.008, and more ideal to be less than 0.005. From an industrial point of view, as long as the lower limit is more than 0.0001, it does not matter even if it is more than 0.001. The above-mentioned change refers to the difference between (tanδ1) and (tanδ2), which can be obtained by change = |(tanδ1)-(tanδ2)|.

It is ideal that the relative dielectric constant of the adhesive composition of the present invention is hardly observed to increase even after the cured adhesive composition is allowed to absorb moisture (saturated water absorption). Specifically, it is ideal that the relative dielectric constant (ε _c 2) at a frequency of 1 GHz after the cured adhesive composition is allowed to absorb moisture (saturated water absorption) is 3.0 or less. It is more ideal that it is 2.6 or less, and it is even more ideal that it is 2.3 or less. The lower limit is not particularly limited, and it is 2.0 in practical use. Moreover, it is ideal that the relative dielectric constant (ε _c 2) in the entire frequency range of 1 GHz to 60 GHz is 3.0 or less, 2.6 or less, and 2.3 or less is even more ideal.

The total amount of maleic acid and maleic anhydride contained in the adhesive composition is preferably 1% by mass or less. From the perspective of improving adhesion, solder heat resistance and shelf life, it is more preferably 0.8% by mass or less, more preferably 0.6% by mass or less, and particularly preferably 0.4% by mass or less. The lower the total amount of maleic anhydride and maleic acid, the better. Industrially, it only needs to be 0.01% by mass or more, but even 0.1% by mass or more is not a problem.

＜Oligophenyl ether (c)＞ The adhesive composition of the present invention can exhibit better solder heat resistance by containing oligophenyl ether (c). In addition, by containing oligophenyl ether (c), the increase of dielectric tangent after moisture absorption can be suppressed. The oligophenyl ether (c) used in the present invention (hereinafter, also simply referred to as component (c)) is not particularly limited, and a compound having a structural unit represented by the following general formula (c1) and/or a structural unit of the general formula (c2) is more ideal. [Chemistry 1]

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

[Chemistry 2] In the general formula (c2), R ₁₁ , R ₁₂ , R ₁₃ , R ₁₄ , R ₁₅ , R ₁₆ , R ₁₇ , and R ₁₈ are each 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 definitions of the substituents are as described above. As for the alkyl group, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, hexyl, etc. can be listed, and methyl is preferably used. Among them, R ₁₃ , R ₁₄ , R ₁₇ and R ₁₈ are methyl groups, and R ₁₁ , R ₁₂ , R ₁₅ and R ₁₆ are preferably hydrogen. In addition, -A- is preferably a linear, branched or cyclic divalent alkyl group with a carbon number of 20 or less, or oxygen. The carbon number of A is more preferably 1 to 15, and more preferably 2 to 10. In addition, as for the divalent alkyl group of A, there can be listed methylene, ethyl, n-propyl, n-butyl, cyclohexyl, phenylene, etc., among which phenylene is particularly preferred. It is particularly preferred to be oxygen.

The oligophenylene ether (c) may be a modified polyphenylene ether partially or completely functionalized with ethylenically unsaturated groups such as vinylbenzyl, epoxy, amine, hydroxyl, thiol, carboxyl, and silyl. It is also preferred that both ends have hydroxyl, epoxy, or ethylenically unsaturated groups. As for the ethylenically unsaturated groups, there may be listed alkenyl groups such as vinyl, allyl, methacrylic, propenyl, butenyl, hexenyl, and octenyl, cycloalkenyl groups such as cyclopentenyl and cyclohexenyl, and alkenylaryl groups such as vinylbenzyl and vinylnaphthyl. Furthermore, both ends may have the same functional group or different functional groups. From the viewpoint of balancing the high degree of control over the low dielectric tangent and the reduction of the resin residue, it is more preferable that both terminals are hydroxyl groups or vinyl benzyl groups, and it is even more preferable that both terminals are hydroxyl groups or vinyl benzyl groups.

Among the compounds having the structural unit represented by the general formula (c1), the compounds of the general formula (c3) are particularly preferred. In the general formula (c3), n is preferably 3 or more, more preferably 5 or more; preferably 23 or less, more preferably 21 or less, and even more preferably 19 or less.

Furthermore, among the compounds having the structural unit represented by the general formula (c2), the compounds of the general formula (c4) are particularly preferred. In the general formula (c4), n is preferably 2 or more, more preferably 4 or more; 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 even more preferably 700 or more. By making the number average molecular weight of the oligophenylene ether (c) above the lower limit, the flexibility of the adhesive layer obtained can be improved. On the other hand, by making the number average molecular weight of the oligophenylene ether (c) below the upper limit, the solubility in organic solvents can be improved.

When 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). From the viewpoint of exhibiting excellent solder heat resistance, it is more preferably 1 part by mass or more, and even more preferably 5 parts by mass or more. Furthermore, it is more preferably 200 parts by mass or less. From the viewpoint of exhibiting excellent adhesion and solder heat resistance, 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 can react with the carbodiimide, thereby improving the interaction between the adhesive composition and the substrate, and improving the adhesion 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). From the viewpoint of obtaining a sufficient curing effect and exhibiting excellent adhesion and solder heat resistance, 1 part by mass or more is more preferably, 1.5 parts by mass or more is more preferably, and 2 parts by mass or more is particularly preferably. Furthermore, from the viewpoint of having excellent low dielectric properties in addition to adhesion and solder heat resistance, 20 parts by mass or less is more preferably, 15 parts by mass or less is more preferably, 10 parts by mass or less is more preferably, and 5 parts by mass or less is particularly preferably.

The carbodiimide compound (d) may be any one of an aromatic carbodiimide compound, an alicyclic carbodiimide compound or an aliphatic carbodiimide compound, and any of these 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), poly(m-phenylene carbodiimide), poly(diisopropylphenylene carbodiimide), poly(methyl diisopropylphenylene carbodiimide), and poly(4,4'-diphenylmethane carbodiimide). Examples of the alicyclic carbodiimide compound include poly(m-cyclohexyl carbodiimide), poly(p-cyclohexyl carbodiimide), poly(4,4'-dicyclohexyl methane carbodiimide), and poly(3,3'-dicyclohexyl methane carbodiimide). As for the aliphatic carbodiimide compound, any of the linear or branched aliphatic carbodiimide compounds may be used. The linear aliphatic carbodiimide compound is more preferable, and specifically, polymethylene carbodiimide, polyethylene carbodiimide, polypropylene carbodiimide, polybutylene carbodiimide, polypentyl carbodiimide, polyhexyl carbodiimide, etc. can be listed. These can be used alone or in combination of two or more. Among them, aromatic carbodiimide compounds or alicyclic carbodiimide compounds are particularly preferable.

<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 can dissolve the acid-modified polyolefin (a), epoxy resin (b), oligophenylene ether (c) and carbodiimide compound (d). Specifically, 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 solvents such as methanol, ethanol, isopropanol, butanol, pentanol, hexanol, propylene glycol, and phenol, and ketones such as acetone, methyl isobutyl ketone, methyl ethyl ketone, pentanone, hexanone, cyclohexanone, isophorone, and acetophenone can be used. Solvents, cellosolves such as methyl cellosolve and ethyl cellosolve, ester solvents such as methyl acetate, ethyl acetate, butyl acetate, methyl propionate, butyl formate, ethylene glycol mono-n-butyl ether, ethylene glycol mono-isobutyl ether, ethylene glycol mono-tert-butyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-isobutyl ether, triethylene glycol mono-n-butyl ether, tetraethylene glycol mono-n-butyl ether, etc., glycol ether solvents, etc., can be used alone or in combination of two or more. Considering the working environment and dryness, methylcyclohexane and toluene are particularly ideal.

The organic solvent is preferably in the range of 100 to 1000 parts by mass relative to 100 parts by mass of the acid-modified olefin (a), 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. If it is above the lower limit, it can be in a good liquid state and the usability will be good. If it is below the upper limit, it will be advantageous in terms of manufacturing cost and transportation cost.

The organic solvent is preferably a mixed solution 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 solvents, ketone solvents, ester solvents and glycol ether solvents, from the viewpoint of the solution state and the use period of the adhesive composition. As for the mixing ratio, solvent (e1)/solvent (e2) = 50~97/50~3 (mass ratio) is more ideal, 55~95/45~5 (mass ratio) is more ideal, 60~90/40~10 (mass ratio) is even more ideal, and 70~80/30~20 (mass ratio) is particularly ideal. If it is within the above range, the solution state and the shelf life of the adhesive composition will become good. In addition, it is particularly ideal that the solvent (e1) is an aromatic hydrocarbon or an alicyclic hydrocarbon, and the solvent (e2) is a ketone solvent.

Furthermore, the adhesive composition of the present invention may contain other components as needed within the scope that does not impair the effects of the present invention. Specific examples of such components include flame retardants, adhesives, fillers, and silane coupling agents.

<Flame retardant> The adhesive composition of the present invention may be mixed with a flame retardant as needed within the scope of not impairing the effect of the present invention. As for flame retardants, bromine-based, phosphorus-based, nitrogen-based, metal hydroxides, etc. can be listed. Among them, phosphorus-based flame retardants are particularly ideal, and phosphoric acid esters such as trimethyl phosphate, triphenyl phosphate, and tricresyl phosphate can be used; phosphates such as aluminum phosphite; and known phosphorus-based flame retardants such as phosphazenes can be used. They can be used alone, or two or more types can be used in combination. When a flame retardant is contained, it is preferably contained in a range of 1 to 200 parts by mass relative to 100 parts by mass of the total of components (a) to (d), 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. If it is above the lower limit, the flame retardancy will be good. If it is below the upper limit, the adhesion, solder heat resistance, and electrical characteristics will not be reduced.

<Binder> The adhesive composition of the present invention may contain a binder as needed within the range that does not impair the effect of the present invention. Examples of binders include polyterpene resins, rosin resins, aliphatic petroleum resins, alicyclic petroleum resins, copolymerized petroleum resins, styrene resins, and hydrogenated petroleum resins, which are used for the purpose of improving the bonding strength. These may be used alone or in combination of two or more. When the binder is contained, it is preferably contained in a range of 1 to 200 parts by mass relative to 100 parts by mass of the total of the components (a) to (d), 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. If it is above the lower limit, the effect of the binder can be exerted. If it is below the upper limit, the adhesion, solder heat resistance, and electrical characteristics will not be reduced.

<Filler> In the adhesive composition of the present invention, fillers such as silica may be blended as needed within a range that does not impair the effects of the present invention. It is very desirable that the blending of silica improves the heat resistance of the solder. As for silica, hydrophobic silica and hydrophilic silica are generally known, but in order to impart moisture absorption resistance, hydrophobic silica treated with dimethyldichlorosilane, hexamethyldisilazane, octylsilane, etc. is preferred. When silica is contained, it is more desirable that its content falls within the range of 0.05 to 30 parts by mass relative to 100 parts by mass of the total of components (a) to (d). If it is above the above lower limit, the effect of improving the heat resistance of the solder can be exerted. If the content is below the upper limit, poor dispersion of silicon dioxide will not occur, the solution viscosity will be good, the workability will be good, and the adhesiveness will not be reduced.

<Silane coupling agent> In the adhesive composition of the present invention, a silane coupling agent may be mixed as needed within the range that does not impair the effect of the present invention. Mixing a silane coupling agent is very desirable because it improves the adhesion to metal and the heat resistance of solder. The silane coupling agent is not particularly limited, and examples thereof include those having an unsaturated group, those having an epoxypropyl group, and those having an amine group. Among them, from the viewpoint of solder heat resistance, silane coupling agents having a glycidyl group such as γ-glycidoxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltriethoxysilane are more preferable. When a silane coupling agent is contained, it is more preferable that the content thereof falls within the range of 0.5 to 20 parts by mass relative to 100 parts by mass of the total of components (a) to (d). If the content is 0.5 parts by mass or more, excellent solder heat resistance will be improved. On the other hand, if the content is 20 parts by mass or less, solder heat resistance and adhesion will be improved.

<Laminated body> The laminated body of the present invention is formed by laminating the adhesive composition on a substrate (substrate/adhesive layer two-layer laminated body), or by bonding the substrates (substrate/adhesive layer/substrate three-layer laminated body). Here, the adhesive layer refers to the layer of the adhesive composition after applying the adhesive composition of the present invention on a substrate and then drying it. The laminated body of the present invention can be obtained by applying the adhesive composition of the present invention on various substrates, drying it, and then laminating it with other substrates according to general methods.

<Substrate> The substrate in the present invention is not particularly limited as long as it can form an adhesive layer after the adhesive composition of the present invention is applied and dried, and examples thereof include resin substrates such as film-like resins, metal substrates such as metal plates and metal foils, and paper.

Examples of the resin substrate include polyester resins, polyamide resins, polyimide resins, polyamide imide resins, liquid crystal polymers, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resins, and fluorine resins. Preferably, the resin is in a film state (hereinafter, also referred to as a substrate film layer).

As for the metal substrate, any previously known conductive material that can be used for a circuit board can be used. As for the material, various metals such as SUS, copper, aluminum, iron, steel, zinc, nickel, and their alloys, plated products, and metals treated with other metals such as zinc and chromium compounds can be exemplified. Metal foil is more ideal, and copper foil is more ideal. The thickness of the metal foil is not particularly limited, and 1 μm or more is more ideal, 3 μm or more is more ideal, and 10 μm or more is more ideal. In addition, 50 μm or less is more ideal, 30 μm or less is more ideal, and 20 μm or less is more ideal. If the thickness is too thin, it may be difficult to obtain sufficient electrical performance of the circuit. On the other hand, if the thickness is too thick, the processing efficiency during circuit manufacturing may be reduced. Metal foil is usually provided in a roll form. The form of the metal foil used in the manufacture of the printed circuit board of the present invention is not particularly limited. When a strip-shaped metal foil is used, its length is not particularly limited. In addition, its width is not particularly limited, and it is preferably about 250 to 500 cm.

Examples of paper include high-quality paper, kraft paper, roll paper, and glass paper. Examples of composite materials include glass epoxy resin.

Considering the adhesion and durability between the adhesive components, polyester resin, polyamide resin, polyimide resin, polyamide imide resin, liquid crystal polymer, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resin, fluorine resin, SUS steel plate, copper foil, aluminum foil, or glass epoxy resin is more ideal as the base material.

<Adhesive sheet> In the present invention, the so-called adhesive sheet refers to the above-mentioned laminated body and the release substrate laminated with the adhesive composition interposed therebetween. As for the specific configuration, it can be listed as laminated body/adhesive layer/release substrate, or release substrate/adhesive layer/laminated body/adhesive layer/release substrate. By laminating the release substrate, it can function as a protective layer for the substrate. In addition, by using the release substrate, the release substrate can be demolded from the adhesive sheet, and then the adhesive layer can be transferred to another substrate.

By applying the adhesive composition of the present invention on various laminated bodies and drying them according to a general method, the adhesive sheet of the present invention can be obtained. After drying, if a release substrate is bonded to the adhesive layer, it can be rolled up without causing back printing on the substrate, and the workability is excellent. At the same time, because the adhesive layer is protected, the storage is excellent and it is easy to use. After applying and drying on the release substrate, if other release substrates are bonded as needed, the adhesive layer can also be transferred to other substrates.

<Release substrate> There is no particular limitation on the release substrate, and examples thereof include a coating layer of a filler such as clay, polyethylene, or polypropylene on both sides of a paper such as high-quality paper, kraft paper, roll paper, or glassine paper, and then a release agent of a silicone, fluorine, or alkyd resin is applied on each coating layer. In addition, examples thereof include various olefin films such as polyethylene, polypropylene, ethylene-α-olefin copolymer, propylene-α-olefin copolymer, and the like, and the above-mentioned release agent is applied on a film such as polyethylene terephthalate. Considering the reasons of adversely affecting the release force between the release substrate and the adhesive layer, and the electrical properties of silicone, it is more ideal to treat both sides of the high-quality paper with polypropylene filler and use an alkyd release agent on it, or to use an alkyd release agent on polyethylene terephthalate.

Furthermore, the method of coating the adhesive composition on the substrate in the present invention is not particularly limited, and examples thereof include a double-roll coater, a reverse roll coater, and the like. Alternatively, as needed, the adhesive layer can be disposed directly or by transfer on a rolled copper foil or polyimide film that is a constituent material of a printed circuit board. The thickness of the adhesive layer after drying can be appropriately changed as needed, and it is ideal to fall within the range of 5 to 200 μm. If the thickness of the adhesive film is less than 5 μm, the bonding strength is insufficient. If it is more than 200 μm, the drying is insufficient, and problems such as an increase in residual solvent and bulging during pressing in the manufacture of printed circuit boards can be cited. Drying conditions are not particularly limited, but the residual solvent rate after drying is preferably less than 1% by mass. If it exceeds 1% by mass, the residual solvent may cause foaming and swelling during the pressing of printed circuit boards.

<Printed Circuit Board> The "printed circuit board" in the present invention includes a laminated body formed by a metal foil forming a conductive circuit and a resin substrate as a constituent element. The printed circuit board is manufactured by a conventionally known method such as a metal laminated body by a subtractive method. If necessary, the conductive circuit formed by the metal foil is partially or fully covered with a covering film, screen printing ink, etc., and is collectively referred to as a so-called flexible printed circuit (FPC), flat cable, tape automated bonding (TAB) circuit board, etc.

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

Then, if necessary, two or three or more printed circuit boards may be stacked to form a structure.

The adhesive composition of the present invention can be ideally used in various adhesive layers of printed circuit boards. In particular, if the adhesive composition of the present invention is used as an adhesive, in addition to the known polyimide, polyester film, and copper foil constituting the printed circuit board, it also has high adhesion to 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 ideal as an adhesive composition for use in covering films, laminates, copper foils with resins, and adhesive sheets.

In the printed circuit board of the present invention, any resin film that has been used as a substrate of a printed circuit board can be used as the substrate film. As the resin of the substrate film, there can be exemplified polyester resins, polyamide resins, polyimide resins, polyamide imide resins, liquid crystal polymers, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resins, and fluorine resins. In particular, the present invention has excellent adhesion even to low-polarity substrates such as liquid crystal polymers, polyphenylene sulfide, syndiotactic polystyrene, and polyolefin resins.

<Coating film> As for the covering film, any insulating film known in the past can be used as the insulating film for the printed circuit board. For example, films made of various polymers such as polyimide, polyester, polyphenylene sulfide, polyether sulfide, polyether ether ketone, aromatic polyamide, polycarbonate, polyarylate, polyamide imide, liquid crystal polymer, syndiotactic polystyrene, and polyolefin resin can be used. Polyimide film or liquid crystal polymer film is more ideal.

The printed circuit board of the present invention can be manufactured using any conventionally known process, in addition to using the above-mentioned materials for each layer.

In a more ideal implementation, a semi-finished product is manufactured in which an adhesive layer is stacked on a covering film layer (hereinafter referred to as a "covering film side semi-finished product"). On the other hand, a semi-finished product is manufactured in which a metal foil layer is stacked on a base film layer to form a desired circuit pattern (hereinafter referred to as a "base film side 2-layer semi-finished product"); or a semi-finished product is manufactured in which an adhesive layer is stacked on a base film layer and a metal foil layer is stacked thereon to form a desired circuit pattern (hereinafter referred to as a "base film side 3-layer semi-finished product") (hereinafter, the base film side 2-layer semi-finished product and the base film side 3-layer semi-finished product are collectively referred to as the "base film side semi-finished product"). By bonding the cover film side semi-finished product obtained in this way to the substrate film side semi-finished product, a 4-layer or 5-layer printed circuit board can be obtained.

The substrate film semi-finished product can be obtained, for example, by a manufacturing method comprising the following steps: (A) coating a resin solution as a substrate film on the above-mentioned metal foil and subjecting the coating to an initial drying step, and (B) subjecting the laminate of the metal foil obtained in (A) and the initially dried coating to a heat treatment and drying step (hereinafter referred to as a "heat treatment and desolventizing step").

The circuit in the metal foil layer can be formed by a conventionally known method. The additive method or the subtractive method can be used. The subtractive method is preferred.

The obtained substrate film side semi-finished product can be used in its original state for bonding with the cover film side semi-finished product, or can be used for bonding with the cover film side semi-finished product after being bonded with a release film and stored.

The semi-finished product on the covering film side is manufactured, for example, by applying an adhesive to the covering film. If necessary, a crosslinking reaction may be performed in the applied adhesive. In a more ideal implementation, the adhesive layer is semi-hardened.

The obtained semi-finished product on the covering film side can be used in its original state for bonding with the semi-finished product on the base film side, or can be used for bonding with the semi-finished product on the base film side after being bonded with a release film and stored.

The so-called substrate film side semi-finished product and the cover film side semi-finished product are stored in the form of rolls, for example, and then bonded to produce a printed circuit board. As for the bonding method, any method can be used, for example, pressing or rolling can be used for bonding. In addition, the two can be bonded while heating by using a heat press or a heating roll device.

The semi-finished product of the reinforcing material side is preferably manufactured by coating the reinforcing material with an adhesive in the case of a soft and reelable reinforcing material such as a polyimide film. Also, in the case of a reinforcing plate that is hard and cannot be reeled, such as a metal plate such as SUS, aluminum, or a plate obtained by curing glass fiber with epoxy resin, it is more ideal to manufacture it by transfer-coating the adhesive pre-coated on the demoulding substrate. Furthermore, if necessary, a crosslinking reaction can be performed in the coated adhesive. In a more ideal implementation, the adhesive layer is semi-cured.

The obtained reinforcing material side semi-finished product can be used in its original state for bonding to the back side of a printed circuit board, or can be used for bonding to the substrate film side semi-finished product after being bonded with a release film and stored.

Any of the substrate film side semi-finished product, the cover film side semi-finished product, and the reinforcing material side semi-finished product is a laminate for a printed circuit board of the present invention.

<Examples> The following is a more detailed description of the present invention by way of examples. However, the present invention is not limited to the examples. In the examples and comparative examples, "parts" are simply recorded to indicate parts by mass.

(Physical property evaluation method)

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

Number average molecular weight (Mn) The number average molecular weight of the present invention is a value measured by a gel permeation chromatograph manufactured by Shimadzu Corporation (hereinafter referred to as GPC; standard material: 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).

Determination of melting point (Tm) and heat of fusion (ΔH) The melting point and heat of fusion of the present invention are measured by using a differential scanning calorimeter (hereinafter referred to as DSC; manufactured by TA Instruments Japan; Q-2000), heating and melting at a rate of 20°C/min, and cooling and resinization, and the values are measured from the top temperature and area of the melting peak when the temperature is raised and melted again.

(1) Peel strength (adhesion) The following adhesive composition was applied to a 12.5 μm thick polyimide film (manufactured by Kaneka Corporation, APICAL (registered trademark)) or a 25 μm thick LCP film (manufactured by Kuraray Co., Ltd., Vecstar (registered trademark)) so that the thickness after drying was 25 μm, and dried at 130°C for 3 minutes. The adhesive film (stage B product) obtained in this manner was bonded to a 18 μm thick rolled copper foil (manufactured by JX Metal Co., Ltd., BHY series). The bonding is carried out by pressing at 160°C and under a pressure of 40kgf/ ^cm2 for 30 seconds in such a way that the glossy surface of the rolled copper foil contacts the adhesive layer. Then, the foil is hardened by heat treatment at 140°C for 4 hours to obtain a sample for peel strength evaluation. The peel strength is measured by stretching the film at 25°C and performing a 90° peel test at a stretching speed of 50mm/min. This test shows the bonding strength at room temperature. <Evaluation Criteria> ◎: 1.0N/mm or more ○: 0.8N/mm or more and less than 1.0N/mm △: 0.5N/mm or more and less than 0.8N/mm ×: less than 0.5N/mm

(2) Solder heat resistance The samples were prepared in the same way as above. The 2.0 cm × 2.0 cm sample pieces were aged at 23°C for 2 days and floated in a solder bath melted at 280°C for 10 seconds to check for any changes in appearance such as bulging. <Evaluation criteria> ◎: No bulging ○: Partial bulging △: Extensive bulging ×: Bulging and discoloration

(3) Relative dielectric constant (ε _c 1) and dielectric tangent (tan δ1) just after curing The following adhesive composition was applied to a Teflon (registered trademark) sheet with a thickness of 100 μm so that the thickness after drying and curing was 25 μm, and dried at 130°C for 3 minutes. After heat treatment at 140°C for 4 hours to cure it, the Teflon (registered trademark) sheet was peeled off to obtain an adhesive resin sheet for testing. The obtained adhesive resin sheet for testing was cut into a strip of 8 cm × 3 mm to obtain a test specimen. The relative dielectric constant (ε _c 1) and dielectric tangent (tan δ1) were measured using Network Analyzers (manufactured by ANRITSU) using the cavity resonator perturbation method at a temperature of 23°C and a frequency of 1 GHz. The measurement was performed within 1 hour after heat treatment and hardening. The relative dielectric constant and dielectric tangent obtained were evaluated as follows. <Evaluation criteria for relative 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 tangent> ◎: 0.008 or less ○: More than 0.008 and less than 0.01 △: More than 0.01 and less than 0.02 ×: More than 0.02 (4) Dielectric tangent after saturated water absorption (tanδ2) The following adhesive composition was applied to a Teflon (registered trademark) sheet with a thickness of 100 μm in such a manner that the thickness after drying and curing was 25 μm, and dried at 130°C for 3 minutes. After hardening by heat treatment at 140°C for 4 hours, the Teflon (registered trademark) sheet was peeled off to obtain the test adhesive resin sheet. The test adhesive resin sheet was then immersed in 25°C water and left for 24 hours. After that, the surface moisture was wiped off and the obtained test adhesive resin sheet was cut into 8cm×3mm strips to obtain test samples. The relative dielectric constant (ε _c 2) and dielectric tangent (tanδ2) were measured using Network Analyzers (manufactured by ANRITSU) using the cavity resonator perturbation method at a temperature of 23°C and a frequency of 1GHz. The changes in dielectric tangent (tanδ1) just before hardening and dielectric tangent (tanδ2) after saturated water absorption were calculated and evaluated using the following formula. Change = |(tanδ1)-(tanδ2)| <Evaluation criteria for dielectric tangent change> ◎: 0.002 or less ○: More than 0.002 and less than 0.005 △: More than 0.005 and less than 0.01 ×: More than 0.01

Example 1 100 parts by mass of CO-1, 10 parts by mass of epoxy resin HP-7200H and 440 parts by mass (solid content concentration is 20% by mass) of organic solvent (methylcyclohexane/methylethylketone/toluene = 72/8/20 (v/v)) were mixed to obtain a mixed solution. The mixing amount, bonding strength, solder heat resistance, electrical properties just after hardening and dielectric tangent change after saturated water absorption are shown in Table 1.

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

[Table 1]

Comparative Examples 1-3 The blending amounts of components (a)-(d) were changed as shown in Table 1, and comparative examples 1-3 were carried out in the same manner as Example 1. The bonding strength, solder heat resistance, electrical properties just after curing, and dielectric tangent change after saturated water absorption are shown in Table 1.

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 epoxy resin: HP-7200 (manufactured by DIC Corporation, epoxy equivalent: 259 g/eq) Dicyclopentadiene epoxy resin: HP-7200H (manufactured by DIC Corporation, epoxy equivalent: 278 g/eq) Cresol novolac epoxy resin: jER-152 (manufactured by Mitsubishi Chemical Corporation, epoxy equivalent: 177 g/eq) Epoxy-modified polybutadiene resin: JP-100 (manufactured by Nippon Soda Co., Ltd., epoxy equivalent: 200 g/eq) (Oligophenyl ether (c)) Oligophenyl ether styrene-modified product: OPE-2St 1200 (Mitsubishi Gas Chemical Co., Ltd., Mn1000 compound with the structure of general formula (c4)) Polyphenylene ether styrene modified product: OPE-2St 2200 (Mitsubishi Gas Chemical Co., Ltd., Mn2000 compound with the structure of general formula (c4)) Polyphenylene ether: SA90 (SABIC Co., Ltd., Mn1800 compound with the structure of general formula (c3)) (Carbodiimide compound (d)) Carbodiimide resin: V-09GB (Nisshinbo Chemical Co., Ltd., carbodiimide equivalent: 216 g/eq) Carbodiimide resin: V-03 (Nisshinbo Chemical Co., Ltd., carbodiimide equivalent: 209 g/eq)

(Acid-modified polyolefin (a)) Production Example 1 100 parts by mass of propylene-butene copolymer ("TAFMER (registered trademark) XM7080" manufactured by Mitsui Chemicals Co., Ltd.), 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 to a 1L autoclave, heated to 140°C, and stirred for 3 hours. After that, the obtained reaction liquid was cooled and poured into a container containing a large amount of methyl ethyl ketone to precipitate the resin. Thereafter, the acid-modified propylene-butene copolymer grafted with maleic anhydride was separated and purified from the (poly)maleic anhydride and low molecular weight substances by centrifugal separation of the liquid containing the resin. Thereafter, the mixture was dried at 70°C for 5 hours under reduced pressure to obtain a maleic anhydride-modified propylene-butene copolymer (CO-1, acid value 19 mgKOH/g, number average molecular weight 25,000, Tm 80°C, ΔH 35 J/g).

Preparation Example 2 Except that the feed amount of maleic anhydride was changed to 14 parts by mass, 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 Preparation Example 1.

Preparation Example 3 Except that the feed amount of maleic anhydride was changed to 11 parts by mass, 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 Preparation Example 1.

Preparation Example 4 Except that the feed amount of maleic anhydride was changed to 6 parts by mass, 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 Preparation Example 1.

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

As can be seen from Table 1, in Examples 1 to 16, the adhesion, solder heat resistance, electrical properties just after curing, and dielectric tangent change after saturated water absorption are all good. In contrast, in Comparative Example 1, the dielectric tangent just after curing and the dielectric tangent change after saturated water absorption are poor. It is believed that this is because the proportion of epoxy resin (b) is high. In Comparative Example 2, because it does not contain acid-modified polyolefin (a), the electrical properties just after curing and the dielectric tangent change after saturated water absorption are poor. In Comparative Example 3, because it does not contain epoxy resin (b), the solder heat resistance is reduced. [Industrial Utilization]

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 the dielectric tangent after saturated water absorption is also excellent. The adhesive composition of the present invention can obtain an adhesive sheet and a laminated body bonded therewith. The above characteristics are helpful in the use of flexible printed circuit boards, especially in the use of FPCs that seek low dielectric properties (low relative dielectric constant, low dielectric tangent) in high frequency areas.

Claims (6)

An adhesive composition comprises an acid-modified polyolefin (a) and an epoxy resin (b), wherein the acid value of the acid-modified polyolefin (a) is 5-40 mgKOH/g and the following (1)-(2) are satisfied: (1) the relative dielectric constant (εc1) of the cured adhesive composition at 1 GHz is less than 3.0 and the dielectric tangent (tanδ1) is less than 0.02 when the cured adhesive composition is just cured; (2) the change in dielectric tangent (tanδ1) of the cured adhesive composition at 1 GHz when the cured adhesive composition is just cured and the dielectric tangent (tanδ2) at 1 GHz after immersion in water at 25°C for 24 hours is less than 0.01. The adhesive composition of claim 1 contains 1 to 40 parts by weight of epoxy resin (b) relative to 100 parts by weight of acid-modified polyolefin (a). The adhesive composition of claim 1 or 2 further contains oligophenylene ether (c) and/or carbodiimide compound (d). An adhesive sheet having a layer containing an adhesive composition as described in any one of claims 1 to 3. A laminate having a layer containing an adhesive composition as described in any one of claims 1 to 3. A printed circuit board comprising a laminate as claimed in claim 5 as a constituent element.