TWI851851B - Adhesive films, laminates, and printed wiring boards - Google Patents

Abstract

The subject of the present invention is to provide an adhesive film having high adhesion to resin substrates such as polyimide and metal substrates, high solder heat resistance, low dielectric properties, and excellent film operability. The solution to this problem is an adhesive film, which is characterized by containing: acid-modified polyolefin (a), oligophenylene ether (b) with a number average molecular weight of less than 3000, epoxy resin (c), and carbodiimide compound (d); and the content of organic solvent (e) is 1 to 8 mass % relative to the adhesive film.

Description

Adhesive films, laminates, and printed wiring boards

The present invention relates to an adhesive film. More specifically, it relates to an adhesive film used for bonding a resin substrate to another resin substrate or a metal substrate. In particular, it relates to an adhesive film for a flexible printed wiring board (hereinafter referred to as FPC), and to a cover film, a laminate, a copper foil with a resin, and an adhesive sheet including the adhesive film.

Flexible printed circuit boards (FPCs) are often used to fit electronic circuit boards into small and complex interiors because they have excellent flexibility and can accommodate the multifunctionality and miniaturization of personal computers (PCs) and smart phones. In recent years, electronic equipment has been miniaturized, lightweight, high-densified, and high-output, and their popularity has led to an increasing demand for the performance of wiring boards (electronic circuit boards). In particular, with the increase in the speed of transmission signals in FPCs, the frequency of signals is increasing. Along with this, the demand for low dielectric properties (low dielectric constant, low dielectric loss tangent) in the high-frequency region of FPCs has increased. In order to achieve such low dielectric properties, there are methods for reducing the dielectric loss of the FPC base material and adhesive. As for adhesives, development of a combination of polyolefins and epoxides (Patent Document 1) is in progress. [Prior Art Document] [Patent Document]

[Patent Document 1] WO2016/047289

[The problem that the invention wants to solve]

However, the heat resistance of the adhesive used in the reinforcing plate and between the layers in Patent Document 1 is not good. In addition, the amount of solvent in the adhesive film is not considered, and there is a problem of insufficient film handling. In addition, the adhesive film using acid-modified polyolefin with high crystallinity tends to be difficult to fill in the unevenness of the circuit wiring pattern.

The present invention is based on in-depth research to solve the above-mentioned problems. The result is that an adhesive film with a specific composition has high adhesion to resin substrates such as polyimide films or metal substrates such as copper foils, solder heat resistance, and excellent film operability, thereby completing the present invention.

That is, the purpose of the present invention is to provide an adhesive film having good adhesion to both resin substrates such as polyimide films and metal substrates, excellent solder heat resistance, and excellent film operability such as adhesion after drying and circuit embedding properties. [Means for solving the problem]

An adhesive film characterized by containing: acid-modified polyolefin (a), oligophenylene ether with a number average molecular weight of less than 3000 (b), epoxy resin (c), and carbodiimide compound (d); and the content of organic solvent (e) is 1 to 8% by mass relative to the mass of the adhesive film.

The acid value of the acid-modified polyolefin (a) is preferably 5 to 40 mgKOH/g, and the oligophenylene ether (b) having a number average molecular weight of 3000 or less preferably has a structural unit of the general formula (1) and/or a structural unit of the general formula (2). In addition, the organic solvent (e) is preferably one or more organic solvents selected from the group consisting of methyl ethyl ketone, methylcyclohexane and toluene. [Chemistry 1] In the general formula (1), R ₁ , R ₂ , R ₃ , and R ₄ each independently represent 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. [Chemistry 2] In the general formula (2), _R11 , _R12 , _R13 , _R14 , _R15 , _R16 , _R17 , and _R18 each independently represent 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. A is a linear, branched, or cyclic divalent hydrocarbon group having 20 or less carbon atoms, or an oxygen atom.

The adhesive film preferably contains 5-100 parts by weight of oligophenylene ether (b) having a number average molecular weight of 3000 or less, 5-60 parts by weight of epoxy resin (c) and 0.5-20 parts by weight of carbodiimide compound (d) relative to 100 parts by weight of acid-modified polyolefin (a). The relative dielectric constant (ε _c ) of the cured adhesive film at 1 GHz is preferably 3.0 or less, and the dielectric loss tangent (tan δ) is preferably 0.02 or less.

A laminated body is formed using the aforementioned adhesive film. A printed wiring board contains the aforementioned laminated body as a constituent element. [Effect of the invention]

The adhesive film of the present invention has good adhesion to various resin substrates such as polyimide films and metal substrates, and has excellent solder heat resistance. In addition, the film has excellent operability such as adhesion after drying and circuit filling properties.

<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. Polyolefin resin refers to a polymer having a hydrocarbon skeleton as a main body, such as a homopolymer of an olefin monomer exemplified by ethylene, propylene, butylene, butadiene, isoprene, etc., or a copolymer with other monomers, and a hydrogenate, halogenide, 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 to at least one of polyethylene, polypropylene, and propylene-α-olefin copolymer.

The propylene-α-olefin copolymer is a copolymer made of propylene as the main component and α-olefin copolymerized thereon. The α-olefin may be, for example, one or more of ethylene, 1-butene, 1-heptene, 1-octene, 4-methyl-1-pentene, vinyl acetate, etc. Among these α-olefins, ethylene and 1-butene are preferred. The ratio of the propylene component to 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.

At least one of the α,β-unsaturated carboxylic acids and their anhydrides can be exemplified by maleic acid, itaconic acid, liraconic acid and their anhydrides. Among them, anhydrides are 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 exemplified. These acid-modified polyolefins can be used alone or in combination of two or more.

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 and adhesion to resin substrates and metal substrates. By setting it to above the aforementioned lower limit, the compatibility with the epoxy resin (c) can be improved, and excellent bonding strength can be exhibited. In addition, the crosslinking density is high and the solder heat resistance is improved. The upper limit is preferably 40 mgKOH/g or less, more preferably 30 mgKOH/g or less, and even more preferably 20 mgKOH/g or less. By setting it to below the aforementioned upper limit, the adhesion will be improved.

The number average molecular weight (Mn) of the acid-modified polyolefin (a) is preferably in the range of 10,000 to 50,000. It is more preferably in the range of 15,000 to 45,000, more preferably in the range of 20,000 to 40,000, and particularly preferably in the range of 22,000 to 38,000. By setting it to be above the aforementioned lower limit, the cohesive force can be improved and excellent adhesion can be exhibited. In addition, by setting it to be below the aforementioned upper limit, the fluidity is excellent and the workability during bonding is good.

The acid-modified polyolefin (a) is preferably a crystalline acid-modified polyolefin. The term "crystalline" as used in the present invention means that the polyolefin exhibits a clear melting peak during the temperature rise from -100°C to 250°C at 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. It is more preferably in the range of 60°C to 100°C, and most preferably in the range of 70°C to 90°C. By setting it to be above the aforementioned lower limit, the cohesive force derived from crystallization can be improved, and excellent adhesion and solder heat resistance can be exhibited. In addition, by setting it to be below the aforementioned upper limit, the solution stability and fluidity are excellent, and the workability during bonding 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. It is more preferably in the range of 10 J/g to 50 J/g, and most preferably in the range of 20 J/g to 40 J/g. By setting it to be above the aforementioned lower limit, the cohesive force derived from crystallization can be improved, and excellent adhesion and solder heat resistance can be exhibited. In addition, by setting it to be below the aforementioned upper limit, the solution stability and fluidity are excellent, and the workability during bonding is good.

The method for producing the acid-modified polyolefin (a) is not particularly limited, and examples thereof include free radical grafting reaction (i.e., a free radical species is generated for a polymer as a main chain, and the free radical species is used as a polymerization starting point to carry out graft polymerization of an unsaturated carboxylic acid and anhydride).

There is no particular restriction on the free radical generator, but organic peroxides are preferably used. There is no particular restriction on the organic peroxide, and examples thereof include: di(tertiary butyl) peroxyphthalate, tertiary butyl hydroperoxide, diisopropylbenzene peroxide, benzoyl peroxide, tertiary butyl peroxybenzoate, tertiary butyl peroxy-2-ethylhexanoate, tertiary butyl peroxytrimethylacetate, methyl ethyl ketone peroxide, di(tertiary butyl) peroxide, lauryl peroxide and other peroxides; azo nitriles such as azobisisobutylonitrile and azobisisopropionitrile, etc.

<Oligopylenol ether (b)> The oligopylenol ether (b) (hereinafter also referred to as component (b)) used in the present invention has a mesh average molecular weight (Mn) of 3000 or less, and preferably a compound having a structural unit represented by the following general formula (1) and/or a structural unit represented by the general formula (2) can be used.

[Chemistry 1] In the general formula (1), R ₁ , R ₂ , R ₃ , and R ₄ are preferably independently a hydrogen atom, an alkyl group which may be substituted, an alkenyl group which may be substituted, an alkynyl group which may be substituted, an aryl group which may be substituted, an aralkyl group which may be substituted, or an alkoxy group which may be substituted. The "alkyl" of the alkyl group which may be substituted is, for example, a group having 1 to 6 carbon atoms, and is preferably a linear or branched alkyl group having 1 to 3 carbon atoms. More specifically, the group includes methyl, ethyl, propyl, isopropyl, butyl, isobutyl, dibutyl, tertiary butyl, pentyl, hexyl, etc., and is more preferably methyl or ethyl. The "alkenyl" of the alkenyl group which may be substituted is, for example, a vinyl group, a 1-propenyl group, a 2-propenyl group, a 3-butenyl group, a pentenyl group, a hexenyl group, etc., and is more preferably a vinyl group or a 1-propenyl group. Examples of the "alkynyl" of the alkynyl group which may be substituted include ethynyl, 1-propynyl, 2-propynyl (propargyl), 3-butynyl, pentynyl, hexynyl, etc., preferably ethynyl, 1-propynyl or 2-propynyl (propargyl). Examples of the "aryl" of the aryl group which may be substituted include phenyl, naphthyl, etc., preferably phenyl. Examples of the "aralkyl" of the aralkyl group which may be substituted include benzyl, phenethyl, 2-methylbenzyl, 4-methylbenzyl, α-methylbenzyl, 2-vinylphenethyl, 4-vinylphenethyl, etc., preferably benzyl. Examples of the "alkoxy" of the alkoxy group which may be substituted include a linear or branched alkoxy group having 1 to 6 carbon atoms, preferably 1 to 3 carbon atoms. Examples include methoxy, ethoxy, propoxy, isopropoxy, butoxy, di-butoxy, tertiary 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. Examples of such substituents 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, di-butyl, tertiary 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 preferred that _R1 and _R4 are methyl groups, and _R2 and _R3 are hydrogen atoms.

[Chemistry 2] In the general formula (2), R ₁₁ , R ₁₂ , R ₁₃ , R ₁₄ , R ₁₅ , R ₁₆ , R ₁₇ , and R ₁₈ are preferably independently a hydrogen atom, an alkyl group which may be substituted, an alkenyl group which may be substituted, an alkynyl group which may be substituted, an aryl group which may be substituted, an aralkyl group which may be substituted, or an alkoxy group which may be substituted. In addition, the definitions of each substituent are as described above. The alkyl group may be exemplified by methyl, ethyl, propyl, isopropyl, butyl, isobutyl, dibutyl, tertiary butyl, pentyl, hexyl, etc., preferably a methyl group. Among them, preferably R ₁₃ , R ₁₄ , R ₁₇ and R ₁₈ are methyl groups, and R ₁₁ , R ₁₂ , R ₁₅ and R ₁₆ are hydrogen atoms. In addition, -A- is preferably a linear, branched or cyclic divalent alkyl group having 20 or less carbon atoms, or an oxygen atom. The carbon number of A is more preferably 1 to 15, and even more preferably 2 to 10. In addition, the divalent alkyl group of A can be exemplified by methylene, ethylene, n-propylene, n-butylene, cyclohexylene, phenylene, etc., among which phenylene is preferred. It is particularly preferred to be an oxygen atom.

In component (b), part or all of the component may be functionalized with ethylenically unsaturated groups such as vinylbenzyl, epoxy, amino, hydroxyl, alkyl, carboxyl, and silyl to form a modified oligophenylene ether. In addition, both ends preferably have hydroxyl, epoxy, or ethylenically unsaturated groups. Ethylenically unsaturated groups include: vinyl, allyl, methacrylic, propenyl, butenyl, hexenyl, octenyl and other alkenyl groups; cycloalkenyl groups such as cyclopentenyl and cyclohexenyl; alkenylaryl groups such as vinylbenzyl and vinylnaphthyl. In addition, both ends may have the same functional group or different functional groups. From the viewpoint of achieving a balance between high control of low dielectric loss tangent and reduction of resin residue, both ends are preferably hydroxyl groups or vinylbenzyl groups, and both ends are more preferably hydroxyl groups or vinylbenzyl groups.

The compound having the structural unit represented by the general formula (1) is particularly preferably a compound of the general formula (3). In the general formula (3), 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.

Furthermore, the compound having the structural unit represented by the general formula (2) is particularly preferably a compound of the general formula (4). In the general formula (4), 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 component (b) needs to be 3000 or less, preferably 2700 or less, and even more preferably 2500 or less. In addition, the number average molecular weight of the component (b) is preferably 500 or more, and more preferably 700 or more. By setting the number average molecular weight of the component (b) to be above the lower limit, the flexibility of the adhesive film can be improved. On the other hand, by setting the number average molecular weight of the component (b) to be below the upper limit, the solubility in organic solvents can be improved.

The content of component (b) is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, and even more preferably 10 parts by mass or more, relative to 100 parts by mass of component (a). Furthermore, it is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 60 parts by mass or less, and particularly preferably 50 parts by mass or less. By setting it within the above range, an adhesive film having excellent adhesion, solder heat resistance, and circuit embedding properties can be obtained.

<Epoxy resin (c)> The epoxy resin (c) (hereinafter also referred to as component (c)) used in the present invention is not particularly limited as long as it has an epoxy group in the molecule, but it is preferably a molecule having two or more glycidyl groups in the molecule. Specifically, 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, but the present invention is not particularly limited. 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 (c) is preferably 50 g/eq or more, more preferably 100 g/eq or more, and even more preferably 150 g/eq or more. Also, it is preferably 400 g/eq or less, more preferably 350 g/eq or less, and even more preferably 300 g/eq or less. By setting it within the above range, excellent solder heat resistance can be exhibited.

The content of component (c) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more relative to 100 parts by mass of component (a). In addition, it is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 45 parts by mass or less. By setting it within the above range, an adhesive film having a sufficient curing effect, good adhesion and solder heat resistance, and excellent low dielectric properties can be obtained.

<Carbodiimide compound (d)> The carbodiimide compound (d) (hereinafter also referred to as component (d)) used in the present invention is not particularly limited as long as it has a carbodiimide group in the molecule. It is preferably a polycarbodiimide having two or more carbodiimide groups in the molecule. By using polycarbodiimide, the carboxyl group of the acid-modified polyolefin (a) reacts with the carbodiimide group, which can enhance the interaction between the adhesive composition and the substrate and improve the adhesion.

The content of component (d) is preferably 0.5 parts by mass or more, preferably 1 part by mass or more, and more preferably 2 parts by mass or more relative to 100 parts by mass of component (a). By setting it above the aforementioned lower limit, the interaction with the substrate will be exhibited, and the adhesion will become good. In addition, it is preferably 20 parts by mass or less, preferably 15 parts by mass or less, and more preferably 10 parts by mass or less. By setting it below the aforementioned upper limit, excellent dielectric properties can be exhibited. That is, by setting it within the above range, an adhesive film having excellent low dielectric properties in addition to adhesion and solder heat resistance can be obtained.

<Organic solvent (e)> The adhesive film of the present invention must contain 1 to 8 mass % of an organic solvent (e) in the film. Considering good circuit filling properties, it is preferably 2 mass % or more, and more preferably 3 mass % or more. In addition, considering good viscosity, solder heat resistance and electrical properties, it is preferably 7 mass % or less, and more preferably 6 mass % or less. That is, by setting it within the above range, an adhesive film with excellent solder heat resistance, film handling (circuit filling properties and viscosity), and electrical properties can be obtained. The content of the organic solvent is appropriately adjusted depending on the type of organic solvent, film thickness, drying temperature, and drying time.

The organic solvent (e) is preferably one that can dissolve the acid-modified polyolefin (a), the oligophenylene ether (b), the epoxy resin (c) and the carbodiimide compound (d). Specifically, for example, 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, amyl alcohol, hexanol, propanediol and phenol; acetone, methyl isobutyl ketone, methyl ethyl ketone, amyl ketone, hexanone, cyclohexanone, isobutyl ketone, etc. Ketone solvents such as phorone and acetophenone; cellulosides such as methyl cellulosides and ethyl cellulosides; ester solvents such as methyl acetate, ethyl acetate, butyl acetate, methyl propionate, butyl formate; glycol ether solvents such as ethylene glycol mono-n-butyl ether, ethylene glycol mono-isobutyl ether, ethylene glycol mono-tertiary 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., and these can be used alone or in combination of two or more. In particular, considering the working environment and dryness, it is preferable to use one or more selected from the group consisting of methyl ethyl ketone, methylcyclohexane and toluene.

The content of organic solvent (e) in the adhesive film can be calculated as follows. First, weigh the mass of the adhesive film (A). Then, use a dryer to dry the adhesive film at 200°C for 10 minutes, and then weigh the mass after drying (B). The amount of organic solvent (e) can be calculated by the following formula. Organic solvent (e) (mass %) = (1-B/A) × 100

The organic solvent (e) contained in the adhesive film may be a residue of an organic solvent contained in a varnish used in preparing the adhesive film, or may be an organic solvent added after the adhesive film is prepared. Preferably, it is a residue of an organic solvent contained in a varnish.

<Adhesive film> The adhesive film of the present invention is an adhesive film containing an acid-modified polyolefin (a), an oligophenylene ether (b) having a number average molecular weight of less than 3000, an epoxy resin (c), and a carbodiimide compound (d), and containing 1 to 8% by mass of an organic solvent (e). By containing the aforementioned components (a) to (e), it is possible to exhibit excellent adhesion to low-polarity resin substrates such as polyimide films and liquid crystal polymers (LCP), and metal substrates, solder heat resistance, electrical properties (low dielectric properties), and film operability.

The adhesive film can be obtained by applying a varnish (hereinafter also referred to as varnish) which is the source of the adhesive film to a substrate and drying it, and then peeling off the aforementioned substrate. The varnish refers to a product obtained by dissolving or dispersing the aforementioned components (a) to (d) in an organic solvent. The organic solvent contained in the varnish 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 polyolefin (a). By setting it within the aforementioned range, the coating stability is good and it is also advantageous in terms of cost. The organic solvent contained in the varnish is preferably the same as the aforementioned organic solvent (e).

The thickness of the adhesive film is not particularly limited, but is preferably 5 to 200 μm. In view of improving the adhesive strength, it is preferably 10 μm or more, more preferably 15 μm or more, and particularly preferably 20 μm or more. In view of making it easier to control the content of the organic solvent (e) in the drying step, it is preferably 150 μm or less, even more preferably 100 μm or less, and particularly preferably 50 μm or less.

With respect to the adhesive film of the present invention, the relative dielectric constant (ε _c ) of the adhesive film at a frequency of 1 GHz after curing is preferably 3.0 or less. It is more preferably 2.6 or less, and even more preferably 2.3 or less. The lower limit is not particularly limited, and is 2.0 in practical use. Furthermore, the dielectric constant (ε) in the entire frequency range of 1 GHz to 30 GHz is preferably 3.0 or less, more preferably 2.6 or less, and even more preferably 2.3 or less.

With respect to the adhesive film of the present invention, the dielectric loss tangent (tanδ) of the adhesive film at a frequency of 1 GHz after curing is preferably 0.02 or less. It is more preferably 0.01 or less, and even more preferably 0.008 or less. The lower limit is not particularly limited, and is 0.0001 in practical use. Furthermore, the dielectric loss tangent (tanδ) in the entire frequency range of 1 GHz to 30 GHz is preferably 0.02 or less, more preferably 0.01 or less, and even more preferably 0.05 or less.

In the present invention, the relative dielectric constant (ε _c ) and the dielectric loss tangent (tan δ) can be measured as follows. That is, the adhesive film is heat-treated at about 140°C for about 4 hours to harden it (hereinafter also referred to as hardening treatment), and the relative dielectric constant (ε _c ) of the hardened adhesive film at a frequency of 1 GHz is measured. Specifically, a metal layer can be formed on both sides of the adhesive film by a thin film method such as evaporation or sputtering, or by coating a conductive paste, to form a capacitor, and the electrostatic capacitance is measured, and the relative dielectric constant (ε _c ) and the dielectric loss tangent (tan δ) are calculated from the thickness and area. Furthermore, when the adhesive film and the substrate (release substrate) form a laminate, the adhesive film may be hardened only after the substrate is peeled off, or the laminate may be hardened directly before the substrate is peeled off.

Furthermore, the adhesive film of the present invention may contain other components as needed. Specific examples of such components include flame retardants, adhesives, fillers, and silane coupling agents. When the adhesive film contains the aforementioned other components, it is preferable to contain them in advance in the varnish that is the source of the adhesive film.

<Flame retardant> The adhesive film of the present invention may also be blended with a flame retardant as needed. Examples of flame retardants include: bromine-based, phosphorus-based, nitrogen-based, metal hydroxide compounds, etc. Among them, phosphorus-based flame retardants are preferred, and known phosphorus-based flame retardants such as phosphate esters (such as trimethyl phosphate, triphenyl phosphate, tricresol phosphate, etc.), phosphates (such as aluminum hypophosphite, etc.), and phosphazenes can be used. They can be used alone or in any combination of two or more. When containing a flame retardant, the content of the flame retardant is preferably in the range of 1 to 200 parts by mass, preferably in the range of 5 to 150 parts by mass, and most preferably in the range of 10 to 100 parts by mass, relative to a total of 100 parts by mass of components (a) to (d). By setting it within the above range, adhesion, solder heat resistance and electrical properties can be maintained, and flame retardancy can be exhibited.

<Adhesive> The adhesive film of the present invention may also be mixed with an adhesive as needed. Examples of adhesives include polyterpene resins, rosin resins, aliphatic petroleum resins, alicyclic petroleum resins, copolymerized petroleum resins, styrene resins, and hydrogenated petroleum resins, which can be used to improve the bonding strength. They can be used alone or in any combination of two or more. When an adhesive is contained, the content of the adhesive is preferably in the range of 1 to 200 parts by mass, more preferably in the range of 5 to 150 parts by mass, and most preferably in the range of 10 to 100 parts by mass, relative to 100 parts by mass of the total of components (a) to (d). By setting it within the above range, the adhesiveness, solder heat resistance and electrical properties can be maintained, and the adhesive effect can be exhibited.

<Filler> The adhesive film of the present invention can also be blended with fillers such as silica as needed. By blending silica, the heat resistance characteristics will be improved, which is very ideal. Silica is generally known to have hydrophobic silica and hydrophilic silica. In terms of imparting moisture absorption resistance, hydrophobic silica treated with dimethyldichlorosilane, hexamethyldisilazane, octylsilane, etc. is preferred. When blending silica, the blending amount is preferably 0.05 to 30 parts by mass relative to 100 parts by mass of the total of components (a) to (d). By setting it above the above lower limit, further heat resistance can be exhibited. Furthermore, by setting the content to be equal to or less than the above upper limit, poor dispersion of the varnish due to silica or excessive increase in solution viscosity can be suppressed, thereby improving workability.

<Silane coupling agent> The adhesive film of the present invention can also be mixed with a silane coupling agent as needed. By mixing with a silane coupling agent, the adhesion to metal or the heat resistance characteristics are improved, which is very ideal. There is no particular limitation on the silane coupling agent, and examples include: those with unsaturated groups, those with glycidyl groups, those with amino groups, etc. Among them, considering the viewpoint of heat resistance, silane coupling agents with glycidyl groups such as γ-glycidoxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, or β-(3,4-epoxycyclohexyl)ethyltriethoxysilane are more preferred. When the silane coupling agent is added, the amount thereof is preferably 0.5 to 20 parts by weight relative to 100 parts by weight of the total of the components (a) to (d). By setting the amount within the above range, the heat resistance and adhesion of the solder can be improved.

<Laminated body> The laminated body of the present invention is formed by laminating an adhesive film on a substrate (substrate/adhesive film two-layer laminated body), or further laminating a substrate (substrate/adhesive film/substrate three-layer laminated body). The laminated body of the present invention can be obtained by applying the varnish of the present invention, which is the source of the adhesive film, to various substrates according to the conventional method and drying, and further laminating another substrate. Alternatively, it can be obtained by laminating an adhesive film on a substrate and laminating.

<Substrate> The substrate in the present invention is not particularly limited as long as it can be laminated with the adhesive film of the present invention, or can be coated with a varnish that is the source of the adhesive film and dried to form an adhesive film layer. Examples include resin substrates such as film-like resins, metal substrates such as metal plates or metal foils, and paper.

Examples of the resin substrate include polyester resins, polyamide resins, polyimide resins, polyamide imide resins, liquid crystal polymers, polyphenylene sulfide, para-polystyrene, polyolefin resins, and fluorine resins, etc. The resin substrate is preferably a film-like resin (hereinafter also referred to as a substrate film layer).

The metal substrate can use any known conductive material that can be used for circuit boards. Examples of the material include: various metals such as SUS, copper, aluminum, iron, steel, zinc, nickel, and metals treated with other metals such as respective alloys, platings, zinc or chromium compounds, etc. It is preferably a metal foil, and copper foil is more preferred. The thickness of the metal foil is not particularly limited, and is preferably 1 μm or more, preferably 3 μm or more, and more preferably 10 μm or more. In addition, it is preferably 50 μm or less, preferably 30 μm or less, and more preferably 20 μm or less. When the thickness is too thin, sometimes it is difficult for the circuit to obtain sufficient electrical performance. On the other hand, when the thickness is too thick, sometimes the processing efficiency when manufacturing the circuit is reduced. The metal foil is usually provided in a roll form. The form of the metal foil used in manufacturing the printed wiring board of the present invention is not particularly limited. When the metal foil in the form of a strip is used, its length is not particularly limited. In addition, its width is not particularly limited, and is preferably about 250 to 500 cm.

Examples of paper include high-quality paper, kraft paper, paper rolls, and cellophane. Examples of composite materials include glass epoxy resins and the like.

Considering the adhesion and durability of the adhesive film, the substrate is preferably polyester resin, polyamide resin, polyimide resin, polyamide imide resin, liquid crystal polymer, polyphenylene sulfide, para-polystyrene, polyolefin resin, fluorine resin, SUS steel plate, copper foil, aluminum foil, or glass epoxy resin.

<Adhesive sheet> In the present invention, the adhesive sheet is a laminate of the aforementioned laminate and release substrate via an adhesive film. Specific configurations may be listed as: laminate/adhesive film layer/release substrate, or release substrate/adhesive film layer/laminate/adhesive film layer/release substrate. By laminating the release substrate, it functions as a protective layer for the substrate. Furthermore, by using the release substrate, the release substrate can be demolded from the adhesive sheet, and then the adhesive film layer can be transferred to another substrate.

The adhesive sheet of the present invention can be obtained by laminating the laminate of the present invention and a substrate, or by applying a varnish, which is the source of the adhesive film, to various laminates according to a conventional method and drying. Furthermore, if a release substrate is attached to the adhesive film layer after drying, it can be rolled up without causing back printing to the substrate, and the workability is excellent. At the same time, the adhesive film layer is protected, so the storage is excellent and it is easy to use. Furthermore, if it is applied to a release substrate and dried, it is attached to another release substrate as needed, and the adhesive film layer itself can be transferred to other substrates.

<Release substrate> The release substrate is not particularly limited. Examples include those obtained by providing a coating layer of a filler such as clay, polyethylene, or polypropylene on both sides of high-quality paper, kraft paper, paper roll, or cellophane, and then applying a silicone-based, fluorine-based, or alkyd-based release agent on each coating layer. Examples include: polyethylene, polypropylene, ethylene-α-olefin copolymer, propylene-α-olefin copolymer, and other olefin films alone; and those obtained by applying the above-mentioned release agent on a film such as polyethylene terephthalate. Considering the release force of the release substrate and the adhesive layer, and the adverse effects of silicone on electrical properties, it is advisable to perform polypropylene leveling treatment on both sides of high-quality paper and use an alkyd release agent on it, or to use an alkyd release agent on polyethylene terephthalate.

In addition, there is no particular limitation on the method of applying the varnish, which is the source of the adhesive film in the present invention, to the substrate, and examples thereof include: dot coating, reverse roll coating, etc. Alternatively, as required, an adhesive film layer may be directly provided on a rolled copper foil, which is a material constituting a printed wiring board, or on a polyimide film, or by a transfer method. The thickness of the adhesive layer after drying is appropriately varied as required, and is preferably in the range of 5 to 200 μm. By setting the thickness of the adhesive film to be 5 μm or more, sufficient bonding strength can be obtained. Furthermore, by setting it to less than 200 μm, the amount of residual solvent in the drying step can be easily controlled. The drying conditions are not particularly limited as long as they are appropriately adjusted so that the content of the organic solvent (e) becomes 1 to 8 mass %.

<Printed wiring board> The "printed wiring board" in the present invention includes a laminate formed of a metal foil forming a conductive circuit and a resin substrate as a constituent element. The printed wiring board is manufactured by using a known method such as a metal-clad laminate and a subtractive method. The so-called flexible printed circuit (FPC), flat cable, tape automated bonding (TAB) circuit board, etc. are generally referred to as the conductive circuit formed by the metal foil, which is partially or completely covered with a covering film, screen printing ink, etc. as needed.

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

Furthermore, a structure in which two or three or more of the above-mentioned printed wiring boards are stacked can be produced as needed.

The adhesive film of the present invention can be ideally used as the adhesive layer of a printed wiring board. In particular, when the adhesive film of the present invention is used, it not only has high adhesion to the known polyimide, polyester film, and copper foil constituting the printed wiring board, but also has high adhesion to the resin substrate with low polarity such as LCP, and can obtain solder reflow resistance. The adhesive layer itself has excellent low dielectric properties. Therefore, it is suitable as an adhesive film used for a cover film, a laminate, and a copper foil with a resin.

In the printed wiring board of the present invention, the base film can use any resin film that has been used as a base material of the printed wiring board in the past. Examples of the resin of the base film include polyester resin, polyamide resin, polyimide resin, polyamide imide resin, liquid crystal polymer, polyphenylene sulfide, para-polystyrene, polyolefin resin, and fluorine resin. In particular, it has excellent adhesion to low-polarity base materials such as liquid crystal polymer, polyphenylene sulfide, para-polystyrene, and polyolefin resin.

<Coating film> The covering film may be any insulating film known as an insulating film for printed wiring boards. 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, para-polystyrene, and polyolefin resin may be used. Polyimide film or liquid crystal polymer film is more preferred.

In addition to using the above-mentioned materials for each layer, the printed wiring board of the present invention can also be manufactured using any known process.

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

The substrate film-side semi-finished product can be obtained, for example, by a manufacturing method comprising the steps of (A) applying a resin solution to become a substrate film to the aforementioned metal foil and subjecting the coating to initial drying, and (B) heat treating and drying the laminate of the metal foil obtained in (A) and the initial dried coating (hereinafter referred to as "heat treatment-desolventizing step").

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

The obtained semi-finished product on the substrate film side can be directly used for bonding with the semi-finished product on the covering film side, or can be bonded with a release film and stored before being used for bonding with the semi-finished product on the covering film side.

The semi-finished product on the covering film side is manufactured by, for example, applying a varnish, which is the source of the adhesive film, to the covering film. The adhesive film layer can be cured as needed. In an ideal embodiment, the adhesive film layer is semi-cured.

The obtained semi-finished product on the covering film side can be directly used for bonding with the semi-finished product on the substrate film side, or can be bonded with a release film and stored before being used for bonding with the semi-finished product on the substrate film side.

The semi-finished product on the substrate film side and the semi-finished product on the cover film side are stored in the form of rolls, for example, and then bonded together to produce a printed wiring board. The bonding method can be any method, for example, bonding by pressing or rolling. Alternatively, the two can be bonded together while applying heat by using a heating pressing method or a heating roll device.

In the case of a soft and rollable reinforcing material such as a polyimide film, the semi-finished product of the reinforcing material side is preferably manufactured by applying a varnish, which is the source of the adhesive film, to the reinforcing material. In the case of a hard and non-rollable reinforcing plate such as a metal plate such as SUS, aluminum, or a plate made by hardening glass fiber with epoxy resin, it is preferably manufactured by previously transferring and coating an adhesive film provided with a release substrate. In addition, the adhesive film layer can be hardened as needed. In an ideal implementation, the adhesive film layer is semi-hardened.

The obtained semi-finished product on the side of the reinforcing material can be directly used for bonding with the back of the printed wiring board, or can be stored after bonding with a release film and then used for bonding with the semi-finished product on the side of the base film.

The semi-finished product on the substrate film side, the semi-finished product on the cover film side, and the semi-finished product on the reinforcing material side are all laminated bodies for printed wiring boards in the present invention.

<Example> The present invention is described in more detail below with reference to an example. However, the present invention is not limited to the example. In the example and comparative example, parts by mass are generally expressed in parts.

(Physical property evaluation method)

[Acid value (a) component: acid-modified polyolefin] The acid value (mgKOH/g) in the present invention is obtained by dissolving the acid-modified polyolefin in toluene and titrating the 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 using 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 and Heat of Fusion] The melting point and heat of fusion in 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, cooling and resinization, and then measuring the peak temperature and area of the melting peak when heating and melting again.

(1) Adhesion after drying The varnish to be described later as the source of the adhesive film was applied to a 12.5 μm thick polyimide film (manufactured by Kaneka Co., Ltd., APICAL (registered trademark)) and dried to a film thickness of 25 μm and a predetermined residual solvent amount. After adjusting to 25°C, a 12.5 μm thick polyimide film (manufactured by Kaneka Co., Ltd., APICAL (registered trademark)) was lightly pressed against the adhesive film surface of the obtained adhesive film with a substrate, and the adhesion was evaluated. The evaluation criteria are as follows. ＜Evaluation criteria＞ ◎: No adhesion ○: Partial adhesion △: A lot of adhesion ×: Strong adhesion and not easy to peel off

(2) Circuit embedding properties A varnish, which will be described later as the source of the adhesive film, was applied to a 12.5 μm thick polyimide film (manufactured by Kaneka Co., Ltd., APICAL (registered trademark)) and dried to a film thickness of 25 μm and a predetermined residual solvent amount. The obtained adhesive film with a substrate was bonded to a single-sided copper-clad laminate (copper thickness 12 μm, polyimide film thickness 25 μm, L (line: wiring width)/S (spacing: spacing width) = 10/10 μm) on which a fine circuit with a comb pattern was formed. The lamination was performed by heating at 5kgf/ ^cm2 , 80℃, 1 minute, 1Torr, and then flattened by using a hot plate press at 10kgf/ ^cm2 , 90℃, 1 minute. After lamination, air entered the boundary between the line and the space, and checked 100 places through the carrier film to see if there were bubbles (voids) in the resin layer. The evaluation criteria are as follows. <Evaluation Criteria> ◎: No voids were found. ○: 1 to 2 voids were found. △: 3 to 5 voids were found. ×: 6 or more voids were found.

(3) Peel strength (adhesion) A varnish which will be the source of the adhesive film described below is applied to a polyimide film having a thickness of 12.5 μm (manufactured by Kaneka Co., Ltd., APICAL (registered trademark)) and dried to a film thickness of 25 μm and a predetermined residual solvent amount. The obtained adhesive film with a substrate is bonded to a rolled copper foil having a thickness of 18 μm (manufactured by JX Metal Co., Ltd., BHY series). The bonding is performed in such a way that the glossy surface of the rolled copper foil is in contact with the adhesive film, and the bonding is performed by pressing at 160°C and a pressure of 40 kgf/ ^cm2 for 30 seconds. Then, heat-treat at 140℃ for 4 hours to harden it, and obtain a sample for peel strength evaluation. The peel strength is measured by stretching the polyimide film at 25℃, performing a 90° peel test at a stretching speed of 50mm/min, and measuring the peel strength. This test represents the adhesive 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

(4) Solder heat resistance The samples were prepared in the same way as the peel strength test. The 2.0 cm × 2.0 cm sample pieces were aged at 23°C for 2 days and then floated in a solder bath melted at 280°C for 10 seconds to check for any changes in appearance such as swelling. <Evaluation criteria> ◎: No swelling ○: Some swelling △: A lot of swelling ×: Swelling and discoloration

(5) Relative dielectric constant (ε _c ) and dielectric loss tangent (tan δ) The adhesive composition described below was applied to a Teflon (registered trademark) sheet having a thickness of 100 μm and dried to a thickness of 25 μm after drying and hardening, and to a predetermined residual solvent amount. Then, after hardening by heat treatment at 140°C for 4 hours, the Teflon (registered trademark) sheet was peeled off to obtain a test adhesive resin sheet (adhesive film). The sample was cut into a strip of 8 cm × 3 mm to obtain a test sample. The dielectric constant (ε _c ) and dielectric loss tangent (tan δ) were measured using a Network Analyzer (manufactured by Anritsu Corporation) by the resonant cavity perturbation method at a temperature of 23°C and a frequency of 1 GHz. The relative dielectric constant and dielectric loss 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 loss 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

[Example 1] 80 parts by mass of CO-1, 20 parts by mass of OPE-2St 1200, 17 parts by mass of epoxy resin HP-7200, 5 parts by mass of polycarbodiimide V-09GB, 288 parts by mass of methylcyclohexane, 39 parts by mass of methyl ethyl ketone, and 11 parts by mass of toluene were mixed, and 94 parts by mass of methylcyclohexane was added as an additional solvent and uniformly dissolved to prepare a varnish as a source of an adhesive film. APICAL12.5NPI (trade name, manufactured by Kaneka Co., Ltd.) of a polyimide film with a thickness of 12.5 μm was used as the support film, and the varnish was applied and dried. The coating and drying were carried out in such a way that the film thickness became 25μm and the residual solvent amount became 3 mass %, and an adhesive film with a substrate was obtained. The viscosity, circuit filling property, bonding strength, solder heat resistance, and electrical properties after drying are shown in Table 1.

[Examples 2 to 15] Examples 2 to 15 were carried out in the same manner as Example 1 with modifications as shown in Table 1. The viscosity, circuit filling properties, bonding strength, solder heat resistance, and electrical properties after drying are shown in Table 1.

[Comparative Examples 1 to 7] Comparative Examples 1 to 7 were carried out in the same manner as Example 1 with modifications as shown in Table 1. The viscosity, circuit filling properties, bonding strength, solder heat resistance, and electrical properties after drying are shown in Table 1.

[Table 1] Embodiment Embodiment Embodiment Embodiment Embodiment Embodiment Embodiment Embodiment Embodiment Embodiment Embodiment Embodiment Embodiment Embodiment Embodiment Comparison Example Comparison Example Comparison Example Comparison Example Comparison Example Comparison Example Comparison Example 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1 2 3 4 5 6 7 Acid-modified polyolefin (a) (wt.%) CO-1 (Tm80℃) 80 CO-2 (Tm78℃) 80 CO-3 (Tm80℃) 80 80 70 80 80 80 80 80 80 80 60 90 100 80 100 80 80 80 CO-4 (Tm82℃) 80 Oligophenylene ether (b) (wt.%) OPE-2St 1200 20 OPE-2St 2200 20 20 20 20 30 20 20 20 20 20 20 20 40 10 20 100 20 20 20 PPO powder 20 Epoxy resin (c) (mass percentage) HP-7200 17 17 17 17 17 16 34 17 17 17 17 17 17 HP-7200H 17 twenty two 17 17 17 17 17 17 Carbodiimide compound (d) (parts by mass) V-09GB 5 5 5 5 5 5 5 5 5 2 20 5 5 5 5 5 5 5 5 5 V-03 5 Solvent (mass) Methylcyclohexane 288 288 288 288 288 252 288 288 288 288 288 288 288 216 324 360 288 0 360 288 288 288 Methyl Ethyl Ketone 39 39 39 39 39 35 47 39 41 39 39 39 39 31 43 47 39 7 40 39 39 39 Toluene 11 11 11 11 11 17 11 11 11 11 11 11 11 twenty three 6 0 11 56 11 11 11 11 Total solid content (weight) 122 122 122 122 122 121 139 122 127 119 137 122 122 122 122 122 117 122 125 122 122 122 Total solvent amount (parts by mass) 339 339 339 339 339 304 346 339 341 339 339 339 339 270 373 407 339 64 411 339 339 339 Solid content concentration before adjustment (wt%) 26.5 26.5 26.5 26.5 26.5 28.5 28.7 26.5 27.2 26.0 28.8 26.5 26.5 31.1 24.7 23.0 25.7 65.8 23.3 26.5 26.5 26.5 Solvent additional ingredients (mass fraction) Methylcyclohexane 94.0 94.0 94.0 94.0 94.0 125.3 147.0 94.0 109.6 83.4 147.2 94.0 94.0 162.8 59.6 25.3 76.3 369.0 31.9 94.0 94.0 94.0 Adjusted solid content concentration (wt%) twenty two twenty two twenty two twenty two twenty two twenty two twenty two twenty two twenty two twenty two twenty two twenty two twenty two twenty two twenty two twenty two twenty two twenty two twenty two twenty two twenty two twenty two Residual solvent (e) (wt%) 3 3 3 3 3 3 3 3 3 3 3 3 6 3 3 3 3 3 3 3 0.5 10 Stickiness after drying Reviews ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ◎ △ ○ ○ ○ ○ Poor dissolution, therefore unable to measure ◎ × Circuit filling Reviews ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ △ ◎ ○ ○ × ○ × ◎ Adhesion strength (PI/Ad/Cu) Reviews △ ◎ △ ○ △ ◎ △ △ △ △ ◎ △ △ ◎ △ ◎ × × △ △ △ Solder heat resistance (PI/Ad/Cu) Reviews △ ◎ ○ ◎ △ ◎ △ △ △ △ △ △ △ ◎ △ × △ △ × ○ × Electrical properties Dielectric constant ○ ◎ ◎ ◎ ○ △ ○ ○ ○ ○ × ○ △ △ ◎ ◎ ◎ ○ ◎ ◎ × Dielectric loss tangent ○ ◎ ◎ ◎ ○ ○ ○ ○ ○ ○ × ○ △ △ ◎ ◎ ◎ ○ ◎ ◎ ×

The acid-modified polyolefin (a), oligophenylene ether (b), epoxy resin (c), and carbodiimide compound (d) used in Table 1 are as follows. (Oligophenyl ether (b)) Oligophenyl ether styrene modified product: OPE-2St 1200 (Mn1000 compound with the structure of general formula (4) manufactured by Mitsubishi Gas Chemical Co., Ltd.) Oligophenyl ether styrene modified product: OPE-2St 2200 (Mn2000 compound with the structure of general formula (4) manufactured by Mitsubishi Gas Chemical Co., Ltd.) Oligophenyl ether: PPO resin powder (Mn20000 compound with the structure of general formula (3) manufactured by SABIC) (Epoxy resin (c)) 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 278g/eq) (Carbodiimide compound (d)) Carbodiimide resin: V-09GB (manufactured by Nisshinbo Chemical Co., Ltd. Carbodiimide equivalent 216g/eq) Carbodiimide resin: V-03 (manufactured by Nisshinbo Chemical Co., Ltd. Carbodiimide equivalent 209g/eq)

(Acid-modified polyolefin (a)) [Production Example 1] In a 1L high temperature and high pressure autoclave, 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(tertiary)butyl peroxide were added, and the temperature was raised to 140°C, and then stirred for 3 hours. Thereafter, the obtained reaction solution was cooled and poured into a container containing a large amount of methyl ethyl ketone to precipitate the resin. Thereafter, by centrifuging the liquid containing the resin, the acid-modified propylene-butene copolymer grafted with maleic anhydride, (poly)maleic anhydride, and low molecular weight substances were separated and purified. Thereafter, by drying at 70°C for 5 hours under reduced pressure, 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) was obtained.

[Production Example 2] The same procedure as in Production Example 1 was followed except that the amount of maleic anhydride fed was changed to 14 parts by mass, thereby obtaining 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).

[Production Example 3] The same procedure as in Production Example 1 was followed except that the amount of maleic anhydride fed was changed to 11 parts by mass, thereby obtaining 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).

[Production Example 4] The same procedure as in Production Example 1 was followed except that the amount of maleic anhydride fed was changed to 6 parts by mass, thereby obtaining 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).

As can be seen from Table 1, in Examples 1 to 15, as far as the adhesive film is concerned, the film operability such as adhesion after drying and circuit embedding property is excellent, and it has excellent adhesion and solder heat resistance with polyimide film and copper foil. In addition, in Example 11, the amount of carbodiimide compound (d) mixed is large, so the electrical properties are poor, but the film operability, adhesion and solder heat resistance are good. In contrast, in Comparative Example 1, oligophenylene ether (b) is not mixed, so the solder heat resistance is poor. In Comparative Example 2, carbodiimide compound (d) is not mixed, so the adhesion is poor. In Comparative Example 3, acid-modified polyolefin (a) is not mixed, so the adhesion and circuit embedding property are poor. In Comparative Example 4, epoxy resin (c) is not mixed, so the solder heat resistance is poor. In Comparative Example 5, the number average molecular weight of oligophenylene ether is large, so it is not dissolved in the organic solvent, and the adhesive film cannot be prepared. In Comparative Example 6, the content of solvent (e) (residual solvent) is small, so the circuit filling property is poor. In Comparative Example 7, the content of solvent (e) (residual solvent) is high, so the viscosity and solder heat resistance after drying are poor. [Industrial Utilization]

The adhesive film of the present invention has high adhesion to resin substrates such as polyimide and metal substrates such as copper foil, and can obtain high solder heat resistance. In addition, by adjusting the amount of carbodiimide compound (d) mixed, excellent low dielectric properties can be exhibited. In addition, since the film operation after drying, such as adhesion and circuit filling properties, is excellent, productivity is excellent. The adhesive film of the present invention can obtain an adhesive sheet and a laminated body bonded using the adhesive sheet. Due to the above characteristics, it is effective in the use of flexible printed wiring boards, especially in FPC uses that require low dielectric properties (low dielectric constant, low dielectric loss tangent) in the high-frequency region.

Claims (8)

An adhesive film, characterized by containing: acid-modified polyolefin (a), oligophenylene ether (b) with a number average molecular weight of less than 3000, epoxy resin (c), and carbodiimide compound (d); and the content of organic solvent (e) is 1-8% by weight relative to the mass of the adhesive film, and relative to 100 parts by weight of acid-modified polyolefin (a), it contains 5-100 parts by weight of oligophenylene ether (b) with a number average molecular weight of less than 3000 and 15-60 parts by weight of epoxy resin (c). As in the adhesive film of claim 1, the acid value of the acid-modified polyolefin (a) is 5-40 mgKOH/g. The adhesive film of claim 1 or 2, wherein the oligophenylene ether (b) having a number average molecular weight of 3000 or less has a structural unit of the general formula (1) and/or a structural unit of the general formula (2);

In the general formula (1), R ₁ , R ₂ , R ₃ and R ₄ each independently represent 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;

In the general formula (2), _R11 , _R12 , _R13 , _R14 , _R15 , _R16 , _R17 and _R18 each independently represent a hydrogen atom, an alkyl group which may be substituted, an alkenyl group which may be substituted, an alkynyl group which may be substituted, an aryl group which may be substituted, an aralkyl group which may be substituted or an alkoxy group which may be substituted; and A is a linear, branched or cyclic divalent hydrocarbon group having not more than 20 carbon atoms, or an oxygen atom. The adhesive film of claim 1 or 2, wherein the film contains 0.5 to 20 parts by mass of a carbodiimide compound (d) relative to 100 parts by mass of the acid-modified polyolefin (a). The adhesive film of claim 1 or 2 has a relative dielectric constant (ε _c ) of less than 3.0 and a dielectric loss tangent (tan δ) of less than 0.02 at 1 GHz after curing. As in the adhesive film of claim 1 or 2, the organic solvent (e) is one or more organic solvents selected from the group consisting of methyl ethyl ketone, methyl cyclohexane and toluene. A laminated body formed using an adhesive film as described in any one of claims 1 to 6. A printed wiring board comprising a laminate as claimed in claim 7 as a constituent element.