Adhesive agent composition, and adhesive sheet, laminated body, and printed wiring board that contain adhesive agent composition

Abstract

The present invention provides: an adhesive agent composition which has excellent solder heat resistance and adhesive strength, and which also has excellent dielectric characteristics including low relative permittivity and low dielectric loss tangent; and an adhesive sheet, a laminated body, and a printed wiring board that contain the adhesive agent composition.　An adhesive agent composition according to the present invention contains: a polyimide resin having an acid value of 10-1000 equivalent / 106g, an oxazoline group-containing polystyrene (A), and an epoxy resin (B). The amount of the oxazoline group-containing polystyrene (A) contained with respect to 100 parts by mass of the polyimide resin is 12-1000 parts by mass.

Description

Adhesive composition, and adhesive sheet, laminate and printed wiring board containing the same

[0001] The present invention relates to an adhesive composition. More specifically, it relates to an adhesive composition for printed wiring boards used for bonding a resin substrate to a resin substrate or a metal substrate. In particular, it relates to an adhesive composition for flexible printed wiring boards (hereinafter abbreviated as FPC), and to adhesive sheets, laminates, and printed wiring boards containing the same.

[0002] FPCs have excellent flexibility, allowing them to accommodate the increasing functionality and miniaturization of personal computers (PCs) and smartphones. They are widely used to incorporate electronic circuit boards into narrow, complex interior spaces. In recent years, electronic devices have become smaller, lighter, more dense, and more powerful, resulting in increasingly demanding performance requirements for wiring boards (electronic circuit boards). In particular, high-frequency signals are increasingly being used to increase transmission speeds. Accordingly, there is a growing demand for FPCs with low dielectric properties (low dielectric constant, low dielectric dissipation factor) in the high-frequency range. To achieve such low dielectric properties, measures have been taken to reduce the dielectric loss of FPC substrates and adhesives. For FPC substrates, in addition to conventional polyimide (PI) and polyethylene terephthalate (PET), substrate films with low dielectric properties, such as liquid crystal polymers (LCPs) and fluororesins, have been proposed. Development of adhesives, such as a combination of polyolefin and epoxy (Patent Document 1) and adhesives using polyphenylene ether (Patent Document 2), has been promoted.

[0003] International Publication No. WO 2016 / 047289 International Publication No. WO 2020 / 196718

[0004] However, the adhesive described in Patent Document 1 contains an epoxy resin and an epoxy resin curing agent, and therefore has high polarity, and is unable to satisfy high requirements, particularly for dielectric loss tangent. The adhesive described in Patent Document 2 cannot be said to have excellent heat resistance as an FPC adhesive, and is also insufficient in terms of dielectric properties.

[0005] The present invention has been made in view of the above-mentioned problems in the prior art. That is, an object of the present invention is to provide an adhesive composition that has excellent solder heat resistance and adhesive strength, and also has excellent dielectric properties such as low relative dielectric constant and dielectric loss tangent, as well as an adhesive sheet, a laminate, and a printed wiring board that contain the same.

[0006] As a result of extensive research, the present inventors have found that the above problems can be solved by the following means, and have arrived at the present invention. That is, the present invention has the following configuration.

[0007] [1] Acid value is 10 equivalents / 10 6 g or more 1000 equivalents / 10 6An adhesive composition comprising a polyimide resin having a viscosity of 10 ... [5] The adhesive composition according to [3] or [4], wherein the oxazoline group-containing monomer is one or more selected from the group consisting of 2-isopropenyl-2-oxazoline, 4,4-dimethyl-2-isopropenyl-2-oxazoline, 4-ethyl-4-hydroxymethyl-2-isopropenyl-2-oxazoline, and 4-ethyl-4-ethoxycarbonylethyl-2-isopropenyl-2-oxazoline. [6] The adhesive composition according to any one of [1] to [5], wherein the oxazoline group content of the oxazoline group-containing polystyrene (A) is 0.10 to 0.50 mmol / g. [7] The adhesive composition according to any one of [1] to [6], wherein the oxazoline group-containing polystyrene (A) has a weight average molecular weight (Mw) of 10,000 or more and 1,000,000 or less. [8] The adhesive composition according to any one of [1] to [7], wherein the epoxy resin (B) is a polyfunctional epoxy resin. [9] The adhesive composition according to [8], wherein the polyfunctional epoxy resin is one or more glycidylamine-type epoxy resins selected from the group consisting of N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, triglycidyl para-aminophenol, 1,3-bis(diglycidylaminomethyl)cyclohexane, and N,N,N',N'-tetraglycidyl-m-xylenediamine.

[10] The adhesive composition according to any one of [1] to [9], which is for use on a printed wiring board.

[11] An adhesive sheet obtained by laminating a substrate that is a resin substrate, a metal substrate, or a paper substrate and a release substrate via the adhesive composition described in any one of [1] to

[10] .

[12] A laminate obtained by laminating a substrate that is a resin substrate, a metal substrate, or a paper substrate with the adhesive composition described in any one of [1] to

[10] .

[13] A printed wiring board that includes the laminate described in

[12] as a component.

[0008] The adhesive composition of the present invention has excellent solder heat resistance, adhesive strength, and also excellent dielectric properties, making it suitable for use in FPC adhesives, adhesive sheets, laminates, and printed wiring boards in the high frequency range.

[0009] An embodiment of the present invention will be described in detail below, however, the present invention is not limited to this embodiment and can be practiced in various modified forms within the scope of the above description.

[0010] <Adhesive Composition> The adhesive composition of the present invention has an acid value of 10 equivalents / 10 6 g or more 1000 equivalent / 10 6 The adhesive composition according to the present invention comprises a polyimide resin having a specific acid value of 0.1 g or less, an oxazoline group-containing polystyrene (A), and an epoxy resin (B), wherein the content of the oxazoline group-containing polystyrene (A) is 12 parts by mass or more and 1,000 parts by mass or less per 100 parts by mass of the polyimide resin. In the present invention, by blending a predetermined amount of the oxazoline group-containing polystyrene (A) with an adhesive composition containing a polyimide resin having a specific acid value and an epoxy resin (B), carboxy groups in the polyimide resin (generally derived from terminal carboxy groups, terminal acid anhydride groups, etc.) react not only with the epoxy resin (B) but also with the oxazoline group-containing polystyrene (A), forming a high-density crosslinked structure and suppressing the generation of hydroxy groups, thereby providing an adhesive composition that has excellent solder heat resistance, adhesive strength, and dielectric properties.

[0011] <Oxazoline Group-Containing Polystyrene (A)> The oxazoline group-containing polystyrene (A) in the present invention is preferably a resin obtained by copolymerizing a styrene-based monomer and an oxazoline group-containing monomer. In other words, the oxazoline group-containing polystyrene (A) is a copolymer having a structural unit derived from a styrene-based monomer and a structural unit derived from an oxazoline group-containing monomer. By containing an oxazoline group, when reacting with a carboxy group of a polyimide resin, a highly heat-resistant crosslink can be formed without generating a hydroxyl group that adversely affects the dielectric properties. In addition, since a styrene-based monomer itself has low dielectric properties, copolymerizing a styrene-based monomer makes it possible to exhibit excellent dielectric properties even as an adhesive.

[0012] The styrene-based monomer constituting the oxazoline group-containing polystyrene (A) can be styrene or a derivative thereof. Specific examples include styrene; alkylstyrenes such as α-methylstyrene, methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene, diethylstyrene, triethylstyrene, propylstyrene, butylstyrene, hexylstyrene, heptylstyrene, and octylstyrene; and halogenated styrenes such as chlorostyrene, fluorostyrene, bromostyrene, dibromostyrene, and iodostyrene. Among these, styrene is preferred.

[0013] The oxazoline group-containing monomer constituting the oxazoline group-containing polystyrene (A) is not particularly limited in terms of its skeleton as long as it contains an oxazoline group and is copolymerizable with a styrene-based monomer, but a monomer having an oxazoline group and a vinyl group (terminal ethylenically unsaturated group) can be preferably used. Examples of the oxazoline group-containing vinyl monomer include 2-vinyl-2-oxazoline, 5-methyl-2-vinyl-2-oxazoline, 4,4-dimethyl-2-vinyl-2-oxazoline, 2-isopropenyl-2-oxazoline, 4,4-dimethyl-2-isopropenyl-2-oxazoline, 4-ethyl-4-hydroxymethyl-2-isopropenyl-2-oxazoline, 4-ethyl-4-ethoxycarbonylethyl-2-isopropenyl-2-oxazoline, 4-acryloyloxymethyl-2,4-dimethyl-2-oxazoline, 4-methacryloyloxymethyl-2,4-dimethyl-2-oxazoline, 4-methacryloyloxymethyl-2-phenyl-4-methyl-2-oxazoline, and 2-(4-vinylphenyl)-4,4-dimethyl-2-oxazoline. Among these, one or more selected from the group consisting of 2-isopropenyl-2-oxazoline, 4,4-dimethyl-2-isopropenyl-2-oxazoline, 4-ethyl-4-hydroxymethyl-2-isopropenyl-2-oxazoline, and 4-ethyl-4-ethoxycarbonylethyl-2-isopropenyl-2-oxazoline are preferred, and 2-isopropenyl-2-oxazoline is more preferred.

[0014] The oxazoline group-containing polystyrene (A) may contain one or more other monomers as its constituents in addition to the styrene-based monomer and the oxazoline group-containing monomer. The other monomers are not particularly limited as long as they are copolymerizable with these monomers, and examples thereof include (meth)acrylate monomers, (meth)acrylic ester monomers, and (meth)acrylamide monomers. The proportion of other monomers other than the styrene-based monomer and the oxazoline group-containing monomer is preferably 20% by mass or less, more preferably 10% by mass or less, and even more preferably 5% by mass or less, relative to 100% by mass of all monomers constituting the oxazoline group-containing polystyrene (A). The lower limit is not particularly limited, but is 0% by mass.

[0015] Although the proportion of each monomer constituting the oxazoline group-containing polystyrene (A) is not particularly limited, a resin obtained by copolymerizing preferably 5% by mass to 50% by mass, more preferably 10% by mass to 30% by mass of oxazoline group-containing monomers relative to 100% by mass of all monomers constituting the oxazoline group-containing polystyrene (A) is preferred. By using oxazoline group-containing monomers within the above range, sufficient reactive sites are obtained, allowing the polyimide resin and the oxazoline group-containing polystyrene (A) to be crosslinked at a high density, thereby achieving good durability.

[0016] The oxazoline group-containing polystyrene (A) preferably has at least one oxazoline group per molecule, more preferably two or more oxazoline groups. The greater the number of oxazoline groups per molecule, the more likely it is that a high-density crosslinked structure can be formed with the carboxy groups in the polyimide resin. The amount of oxazoline groups in the oxazoline group-containing polystyrene (A) is preferably 0.10 to 0.50 mmol / g, more preferably 0.15 to 0.40 mmol / g. When the amount of oxazoline groups is within the above range, the reactions of the polyimide resin, the oxazoline group-containing polystyrene (A), and the epoxy resin (B) proceed in a well-balanced manner.

[0017] The weight average molecular weight (Mw) of the oxazoline group-containing polystyrene (A) is preferably 10,000 or more and 1,000,000 or less, more preferably 20,000 or more and 500,000 or less, even more preferably 50,000 or more and 400,000 or less, and even more preferably 100,000 or more and 300,000 or less. By setting it to the upper limit or less, the viscosity when the oxazoline group-containing polystyrene (A) is dissolved in a solvent becomes in a range suitable for coating, and excellent coating appearance can be achieved. Furthermore, by setting it to the lower limit or more, excellent solder heat resistance can be achieved.

[0018] The oxazoline group-containing polystyrene (A) is also available as a commercial product such as "Epocross RPS-1005" (manufactured by Nippon Shokubai).

[0019] The content of the oxazoline group-containing polystyrene (A) in the adhesive composition of the present invention is 12 to 1000 parts by mass, more preferably 20 to 500 parts by mass, and even more preferably 50 to 200 parts by mass, per 100 parts by mass of the polyimide resin (particularly the solid content of the polyimide resin). Outside this range, crosslinking due to the reaction between the oxazoline group and the carboxy group is insufficient, which may result in poor solder heat resistance. Furthermore, when the content of the oxazoline group-containing polystyrene (A) is within the above range, the dielectric loss tangent tends to be good. In other words, by keeping the content within the above upper and lower limits, excellent dielectric properties and solder heat resistance can be achieved.

[0020] <Polyimide Resin> The polyimide resin of the present invention is a polymer having an imide bond in the main chain, and is produced by a method of producing it from a carboxylic acid anhydride component and an isocyanate component (isocyanate method), a method of synthesizing an amic acid by reacting a polycarboxylic acid component with an amine component and then ring-closing the amic acid (direct method), a method of reacting a compound having a carboxylic acid anhydride and an acid chloride with a diamine, etc. The direct method is advantageous in terms of the wide range of options for monomer components.

[0021] The polyimide resin of the present invention may also contain bond species formed by reactions other than imidization, such as amide bonds, ester bonds, and urethane bonds. The inclusion of these bond species can impart flexibility to the resin, enabling the formation of a flexible cured coating film. Meanwhile, imide bonds, due to their symmetric structure, partially cancel out polarity, which is advantageous for achieving low dielectric properties. Therefore, it is preferable to minimize the content of bond species such as amide bonds, ester bonds, and urethane bonds. To further improve low dielectric properties, the amount of imide bonds is preferably 50 mol% or more, more preferably 70 mol% or more, and even more preferably 80 mol% or more, when the total amount of imide bonds, amide bonds, ester bonds, and urethane bonds is taken as 100 mol%, and even 100 mol% is acceptable.

[0022] The carboxylic acid anhydride component constituting the polyimide resin in the present invention is not particularly limited, and examples thereof include pyromellitic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 4,4'-oxydiphthalic dianhydride, 1,1,1,3,3,3-hexafluoro-2,2-bis(2,3- or 3,4-dicarboxyphenyl)propanhydride, and the like. Examples of the tetrabasic acid dianhydride include tetrabasic acid dianhydrides having an aromatic ring, such as 2,2-bis(2,3- or 3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis[4-(2,3- or 3,4-dicarboxyphenoxy)phenyl]propane dianhydride, aliphatic tetrabasic acid dianhydrides such as meso-butane-1,2,3,4-tetracarboxylic acid dianhydride and pentane-1,2,4,5-tetracarboxylic acid dianhydride, and alicyclic tetrabasic acid dianhydrides such as cyclobutane tetracarboxylic acid dianhydride, cyclopentane tetracarboxylic acid dianhydride, dicyclohexyl-3,3',4,4'-tetracarboxylic acid dianhydride, and hydrogenated products of the above-mentioned tetrabasic acid dianhydrides having an aromatic ring. Alternatively, trimellitic anhydride or a trimellitic anhydride derivative such as an alkylene glycol bisanhydrotrimellitate, such as ethylene glycol bisanhydrotrimellitate, propylene glycol bisanhydrotrimellitate, or 1,4-butanediol bisanhydrotrimellitate, may be used. These may be used alone or in combination. From the viewpoint of dielectric properties, tetrabasic acid dianhydrides having an aromatic ring and alicyclic tetrabasic acid dianhydrides are preferred, and 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride and 2,2-bis[4-(2,3- or 3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA) are more preferred.

[0023] The isocyanate component constituting the polyimide resin in the present invention is not particularly limited, and examples of diisocyanates having an aromatic ring include tolylene diisocyanate (TDI), 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate and its structural isomers, 3,3'-diethyldiphenylmethane-4,4'-diisocyanate and its structural isomers, diphenylmethane-4,4'-diisocyanate, diphenylmethane-3,3'-diisocyanate, diphenylmethane-3,4'-diisocyanate, and diphenylmethane-2,4'-diisocyanate. Examples of suitable diisocyanates include diphenylmethane-2,2'-diisocyanate, diphenylether-4,4'-diisocyanate, benzophenone-4,4'-diisocyanate, diphenylsulfone-4,4'-diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, naphthalene-2,6-diisocyanate, 3,3'- or 2,2'-dimethylbiphenyl-4,4'-diisocyanate, 3,3'- or 2,2'-diethylbiphenyl-4,4'-diisocyanate, and 3,3'-dimethoxybiphenyl-4,4'-diisocyanate. Among these, diphenylmethane-4,4'-diisocyanate (MDI) and 3,3'-dimethylbiphenyl-4,4'-diisocyanate (TODI) are preferred from the viewpoint of polymerizability. These may be used alone or in combination.

[0024] In addition to the diisocyanates having an aromatic ring as already mentioned, aliphatic or alicyclic diisocyanates can also be used, such as diisocyanates obtained by hydrogenating any of the components mentioned in the previous section. Other examples include isophorone diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, ethylene diisocyanate, propylene diisocyanate, and hexamethylene diisocyanate.

[0025] The amine component constituting the polyimide resin in the present invention is not particularly limited, and examples thereof include dimer diamine, m-phenylenediamine, 2,5-diethyl-6-methyl-1,3-benzenediamine, p-phenylenediamine, 2,5-dimethyl-1,4-phenylenediamine, 2,3,5,6-tetramethyl-1,4-phenylenediamine, etc. Among these, dimer diamine is preferred from the viewpoint of low dielectric properties.

[0026] The polyimide resin of the present invention may contain components other than the carboxylic acid anhydride component, isocyanate component, and amine component described above. Examples include aromatic dicarboxylic acid components, aliphatic dicarboxylic acid components, and diol components. Examples of aromatic dicarboxylic acid components include, but are not limited to, terephthalic acid, isophthalic acid, orthophthalic acid, 4,4'-dicarboxybiphenyl, 5-sodium sulfoisophthalic acid, naphthalenedicarboxylic acid, and esters thereof. Examples of aliphatic dicarboxylic acids include, but are not limited to, dimer acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, tetrahydrophthalic acid, methyltetrahydrophthalic acid, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, and hydrogenated naphthalenedicarboxylic acid. Dimer acid is preferred, as it exhibits excellent dielectric properties. The diol component is not particularly limited, but examples thereof include decanediol, dimer diol, polybutadiene with hydroxyl groups at both ends, hydrogenated polybutadiene with hydroxyl groups at both ends, polyisoprene with hydroxyl groups at both ends, polyolefin with hydroxyl groups at both ends, etc. Among these, polybutadiene with hydroxyl groups at both ends is preferred because of its excellent dielectric properties.

[0027] The number average molecular weight (Mn) of the polyimide resin in the present invention is preferably in the range of 10,000 to 50,000. More preferably, it is in the range of 15,000 to 45,000, and even more preferably, it is in the range of 20,000 to 40,000. By making it equal to or greater than the lower limit, the cohesive strength is improved and excellent adhesive properties can be exhibited. Furthermore, by making it equal to or less than the upper limit, excellent flowability and operability can be achieved.

[0028] The polyimide resin in the present invention preferably has a carboxy group, and the lower limit of the acid value of the polyimide resin is 10 equivalents / 10 from the viewpoint of heat resistance and adhesiveness to a resin substrate or a metal substrate. 6 g or more, more preferably 100 equivalents / 10 6 g or more, and more preferably 150 equivalents / 10 6 When the molecular weight is equal to or greater than the above value, the compatibility with the epoxy resin (B) is improved, the adhesive strength is improved, and the crosslinking density is increased, so that the heat resistance can also be improved. The upper limit is 1000 equivalents / 10 6 g or less, and more preferably 700 equivalents / 10 6 g or less, and more preferably 500 equivalents / 10 6 When the thickness is equal to or less than the above value, the adhesiveness and low dielectric properties are improved.

[0029] The glass transition temperature of the polyimide resin in the present invention is preferably −20° C. or higher, more preferably 0° C. or higher, and even more preferably 20° C. or higher. When the glass transition temperature is equal to or higher than the lower limit, solder heat resistance can be improved. There is no particular upper limit to the glass transition temperature, but in practice it is 300° C. or lower, and it may be 200° C. or lower.

[0030] The polyimide resin in the present invention preferably has a relative dielectric constant (εc) of 3.0 or less at a frequency of 10 GHz. It is more preferably 2.8 or less, and even more preferably 2.6 or less. There is no particular lower limit, but in practice it is 2.0. Furthermore, the relative dielectric constant (εc) over the entire frequency range of 1 GHz to 60 GHz is preferably 3.0 or less, more preferably 2.8 or less, and even more preferably 2.6 or less.

[0031] The polyimide resin in the present invention preferably has a dielectric loss tangent (tan δ) of 0.005 or less at a frequency of 10 GHz. It is more preferably 0.004 or less, and even more preferably 0.003 or less. There is no particular lower limit, but in practice it is 0.0001 or more. Furthermore, the dielectric loss tangent (tan δ) over the entire frequency range of 1 GHz to 60 GHz is preferably 0.005 or less, more preferably 0.004 or less, and even more preferably 0.003 or less.

[0032] Polyimide resins can be obtained, for example, by dissolving a carboxylic acid anhydride component and an isocyanate component or an amine component in a solvent and heating the resulting mixture. In this case, the molar ratio of the acid anhydride groups of the carboxylic acid anhydride component to the isocyanate groups of the isocyanate component or the amino groups of the amine component is preferably 100:91 to 100:109. Outside this range, the molecular weight may not increase sufficiently, resulting in insufficient mechanical strength or gelation during polymerization. Furthermore, from the perspective of resin and resin varnish stability, it is preferable that the imide ring moiety of the polyimide resin be 90% or more ring-closed. To achieve this, sufficient reaction is required during polyimide polymerization, and methods such as increasing the reaction temperature or adding a catalyst are available.

[0033] Examples of solvents that can be used in the polymerization of the polyimide resin of the present invention include N-methyl-2-pyrrolidone, γ-butyrolactone, dimethylimidazolidinone, dimethyl sulfoxide, dimethylformamide, N-ethyl-2-pyrrolidone, dimethylacetamide, cyclohexanone, cyclopentanone, tetrahydrofuran, and methylcyclohexane. Among these, cyclohexanone is preferred from the viewpoint of polymerizability. After polymerization, the nonvolatile content and solution viscosity can be adjusted by diluting the solution with the solvent used in the polymerization or another low-boiling solvent.

[0034] Examples of low-boiling point solvents include aromatic solvents such as toluene and xylene, aliphatic solvents such as hexane, heptane and octane, alcohol solvents such as methanol, ethanol, propanol, butanol and isopropanol, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and cyclopentanone, ether solvents such as diethyl ether and tetrahydrofuran, and ester solvents such as ethyl acetate, butyl acetate and isobutyl acetate.

[0035] In order to promote the reaction, a catalyst such as alkali metals such as sodium fluoride, potassium fluoride, and sodium methoxide, amines such as triethylenediamine, triethylamine, diethanolamine, 1,8-diazabicyclo[5,4,0]-7-undecene, and 1,5-diazabicyclo[4,3,0]-5-nonene, or dibutyltin dilaurate can be used.

[0036] The content of the polyimide resin in the adhesive composition of the present invention is preferably 5% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, based on 100% by mass of the solid content of the adhesive composition. It is also preferably 99% by mass or less, more preferably 95% by mass or less, even more preferably 90% by mass or less, and even more preferably 80% by mass or less. A content within the above range is preferred because it results in good adhesion and heat resistance.

[0037] <Epoxy Resin> The adhesive composition of the present invention contains an epoxy resin (B). The epoxy resin used in the present invention is not particularly limited as long as it has an epoxy group in the molecule, but is preferably a multifunctional epoxy resin having two or more, more preferably three or more, epoxy groups in the molecule. Specific examples include, but are not particularly limited to, biphenyl-type epoxy resins, naphthalene-type epoxy resins, bisphenol A-type epoxy resins, bisphenol F-type epoxy resins, novolac-type epoxy resins, alicyclic epoxy resins, dicyclopentadiene-type epoxy resins, glycidylamine-type epoxy resins, and epoxy-modified polybutadienes. Among these, biphenyl-type epoxy resins, novolac-type epoxy resins, dicyclopentadiene-type epoxy resins, glycidylamine-type epoxy resins, epoxy-modified polybutadienes, and glycidyl group-containing isocyanuric acids (e.g., diallyl monoglycidyl isocyanurate, diglycidyl monoallyl isocyanurate, etc.) are preferred, and glycidylamine-type epoxy resins are more preferred. Examples of glycidylamine type epoxy resins include N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, triglycidyl para-aminophenol, 1,3-bis(diglycidylaminomethyl)cyclohexane, and N,N,N',N'-tetraglycidyl-m-xylylenediamine, of which triglycidyl para-aminophenol and N,N,N',N'-tetraglycidyl-m-xylylenediamine are preferred, and triglycidyl para-aminophenol is more preferred.

[0038] In the adhesive composition of the present invention, the content of the epoxy resin (B) is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1 part by mass or more, relative to 100 parts by mass of the polyimide resin. By setting the content at or above the lower limit, a sufficient curing effect can be obtained, and excellent adhesion and solder heat resistance can be exhibited. Furthermore, the content is preferably 10 parts by mass or less, more preferably 5 parts by mass or less. By setting the content at or below the upper limit, the pot life and low dielectric properties can be improved. In other words, by setting the content within the above range, an adhesive composition having excellent adhesion, solder heat resistance, and low dielectric properties can be obtained.

[0039] In the adhesive composition of the present invention, the content of the epoxy resin (B) is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 1.0 parts by mass or more, relative to 100 parts by mass of the oxazoline group-containing polystyrene (A). It is also preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less. When the content of the epoxy resin (B) relative to the oxazoline group-containing polystyrene (A) is within the above range, the oxazoline group-carboxy group and the epoxy group-carboxy group are sufficiently reacted, suppressing the remaining unreacted functional groups, increasing the crosslink density, and improving solder heat resistance. Furthermore, by setting the content at or above the lower limit, good adhesion is achieved, and by setting the content at or below the upper limit, good solder heat resistance is achieved.

[0040] <Polycarbodiimide> The adhesive composition of the present invention may contain a polycarbodiimide. The polycarbodiimide is not particularly limited as long as it has two or more carbodiimide bonds in the molecule. By using a polycarbodiimide, the carboxy group of the polyimide resin or the epoxy group of the epoxy resin (B) reacts with the carbodiimide bond, thereby improving heat resistance and adhesiveness.

[0041] In the adhesive composition of the present invention, the content of polycarbodiimide is preferably 1 part by mass or more, more preferably 3 parts by mass or more, per 100 parts by mass of polyimide resin. By making the content equal to or greater than the lower limit, the crosslink density can be increased, resulting in good solder heat resistance. Furthermore, the content is preferably 20 parts by mass or less, more preferably 10 parts by mass or less. By making the content equal to or less than the upper limit, excellent solder heat resistance and low dielectric properties can be achieved. In other words, by making the content within the above range, an adhesive composition having excellent solder heat resistance and low dielectric properties can be obtained.

[0042] <Unsaturated Hydrocarbon> The adhesive composition of the present invention may contain an unsaturated hydrocarbon having a terminal unsaturated hydrocarbon group and a 5% weight loss temperature of 260°C or higher. When the unsaturated hydrocarbon contains a terminal unsaturated hydrocarbon group, the crosslink density can be increased by a curing reaction caused by radicals generated by using a radical initiator or the like, thereby improving solder heat resistance. Furthermore, since hydroxyl groups that deteriorate dielectric properties are not generated after the reaction, an adhesive with better dielectric properties can be obtained. It is preferable that one molecule contains two or more terminal unsaturated hydrocarbon groups, as this further increases the crosslink density.

[0043] The 5% weight loss temperature of the unsaturated hydrocarbon must be 260°C or higher. It is preferably 270°C or higher, more preferably 280°C or higher, and even more preferably 290°C or higher. When the 5% weight loss temperature is above this value, soldering can be performed without causing poor appearance even at temperatures exceeding the melting point of the solder. There is no particular upper limit, but 500°C is practical.

[0044] The unsaturated hydrocarbon preferably has an aromatic ring structure or an alicyclic structure as a structural unit. Having an aromatic ring structure or an alicyclic structure as a structural unit can improve solder heat resistance and also provide excellent dielectric properties. Among these, an aromatic ring structure or an alicyclic structure is preferred as the skeleton of the unsaturated hydrocarbon, and polyphenylene ether or phenol resin is preferred. Specific examples of polyphenylene ethers having terminal unsaturated hydrocarbon groups include SA-9000 from SABIC Corporation and OPE-2St from Mitsubishi Gas Chemical Company, Inc. Another example of a phenol resin having terminal unsaturated hydrocarbon groups is Resitop FTC-809AE from Gunei Chemical Industry Co., Ltd.

[0045] The number average molecular weight of the unsaturated hydrocarbon is preferably 500 or more, more preferably 1,000 or more. Also, it is preferably 100,000 or less, more preferably 10,000 or less, and even more preferably 5,000 or less. Within the above range, the solubility in solvents is good, and a uniform adhesive coating film can be formed.

[0046] The content of the unsaturated hydrocarbon in the adhesive composition of the present invention is preferably 1 part by mass or more, more preferably 2 parts by mass or more, per 100 parts by mass of the polyimide resin. The content is preferably 100 parts by mass or less, more preferably 50 parts by mass or less. Within this range, both excellent adhesive properties and solder heat resistance can be achieved.

[0047] <Radical Generator> The adhesive composition of the present invention preferably contains a radical generator. The radicals generated by the radical generator efficiently react the terminal unsaturated hydrocarbon groups of the unsaturated hydrocarbon, increasing the crosslink density and thereby improving solder heat resistance and dielectric properties. The radical generator is not particularly limited, but an organic peroxide is preferably used. Examples of organic peroxides include, but are not limited to, peroxides such as di-tert-butyl peroxyphthalate, tert-butyl hydroperoxide, dicumyl peroxide, benzoyl peroxide, tert-butyl peroxybenzoate, tert-butylperoxy-2-ethylhexanoate, tert-butyl peroxypivalate, methyl ethyl ketone peroxide, di-tert-butyl peroxide, and lauroyl peroxide; and azonitriles such as azobisisobutyronitrile and azobisisopropionitrile.

[0048] The one-minute half-life temperature of the radical generator used in the present invention is preferably 140° C. or higher. By setting the temperature to 140° C. or higher, the initiation of a radical reaction can be prevented when the solvent of the adhesive composition varnish is volatilized to produce an adhesive sheet, and excellent adhesiveness can be achieved.

[0049] The amount of the radical generator used in the present invention is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, per 100 parts by mass of the unsaturated hydrocarbon. The amount is preferably 50 parts by mass or less, more preferably 10 parts by mass or less. By adjusting the amount within the above range, an optimal crosslink density can be achieved, and both adhesiveness and solder heat resistance can be achieved.

[0050] <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 polyimide resin, the oxazoline group-containing polystyrene (A), and the epoxy resin (B). Specific examples include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as hexane, heptane, octane, and decane; alicyclic hydrocarbons such as cyclohexane, cyclohexene, methylcyclohexane, and ethylcyclohexane; halogenated hydrocarbons such as trichloroethylene, dichloroethylene, chlorobenzene, and chloroform; alcoholic solvents such as methanol, ethanol, isopropyl alcohol, butanol, pentanol, hexanol, propanediol, and phenol; acetone, methyl isobutyl ketone, methyl ethyl ketone, pentanone, hexanone, cyclohexanone, isophorone, and acetophenone. ketone-based solvents, cellosolves such as methyl cellosolve and ethyl cellosolve, ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, methyl propionate and butyl formate, glycol ether-based solvents such as ethylene glycol mono-n-butyl ether, ethylene glycol mono-iso-butyl ether, ethylene glycol mono-tert-butyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-iso-butyl ether, triethylene glycol mono-n-butyl ether and tetraethylene glycol mono-n-butyl ether, and the like, can be used alone or in combination of two or more thereof. Methylcyclohexane and toluene are particularly preferred from the viewpoint of working environment and drying properties.

[0051] The organic solvent is preferably in the range of 100 to 1,000 parts by mass per 100 parts by mass of the solid content of the adhesive composition. By setting the amount to be equal to or greater than the lower limit, the liquid state and pot life are improved. Furthermore, by setting the amount to be equal to or less than the upper limit, it is advantageous in terms of production costs and transportation costs.

[0052] The adhesive composition of the present invention may further contain other components as needed, such as a flame retardant, a tackifier, a filler, an antioxidant, and a silane coupling agent.

[0053] <Flame Retardant> The adhesive composition of the present invention may optionally contain a flame retardant. Examples of flame retardants include bromine-based, phosphorus-based, nitrogen-based, and metal hydroxide compounds. Phosphorus-based flame retardants are preferred, and known phosphorus-based flame retardants such as phosphate esters (e.g., trimethyl phosphate, triphenyl phosphate, tricresyl phosphate), phosphate salts (e.g., aluminum phosphinate), and phosphazenes can be used. These flame retardants may be used alone or in any combination of two or more. When a flame retardant is added, it is preferably contained in an amount of 1 to 200 parts by mass, more preferably 5 to 150 parts by mass, and most preferably 10 to 100 parts by mass, per 100 parts by mass of the polyimide resin, oxazoline group-containing polystyrene (A), and epoxy resin (B) combined. By keeping the amount within this range, flame retardancy can be achieved while maintaining adhesion, solder heat resistance, and electrical properties.

[0054] <Tackifier> The adhesive composition of the present invention may contain a tackifier as needed. Examples of tackifiers include polyterpene resins, rosin-based resins, aliphatic petroleum resins, alicyclic petroleum resins, copolymerized petroleum resins, styrene resins, and hydrogenated petroleum resins, and are used to improve adhesive strength. These may be used alone or in any combination of two or more. When a tackifier is added, it is preferably added in an amount of 1 to 200 parts by mass, more preferably 5 to 150 parts by mass, and most preferably 10 to 100 parts by mass, per 100 parts by mass of the polyimide resin, oxazoline group-containing polystyrene (A), and epoxy resin (B) combined. By keeping the amount within this range, the effects of the tackifier can be exerted while maintaining adhesion, solder heat resistance, and electrical properties.

[0055] <Filler> The adhesive composition of the present invention may contain a filler as needed. Examples of organic fillers include powders of heat-resistant resins such as polyimide, polyamideimide, fluororesin, and liquid crystal polyester. Examples of inorganic fillers include silica (SiO), alumina (AlO), titania (TiO), tantalum oxide (TaO), zirconia (ZrO), silicon nitride (SiN), boron nitride (BN), calcium carbonate (CaCO), calcium sulfate (CaSO), zinc oxide (ZnO), magnesium titanate (MgO.TiO), barium sulfate (BaSO), organic bentonite, clay, mica, aluminum hydroxide, and magnesium hydroxide. Among these, silica is preferred due to its ease of dispersion and improved heat resistance.

[0056] Hydrophobic silica and hydrophilic silica are generally known as silica, but in this case, hydrophobic silica treated with dimethyldichlorosilane, hexamethyldisilazane, octylsilane, or the like is preferred in order to impart moisture absorption resistance. When silica is added, the amount is preferably 0.05 to 30 parts by mass per 100 parts by mass of the polyimide resin, oxazoline group-containing polystyrene (A), and epoxy resin (B) combined. By adjusting the amount to above the lower limit, further heat resistance can be achieved. Furthermore, by adjusting the amount to below the upper limit, poor dispersion of the silica and excessively high solution viscosity can be suppressed, improving workability.

[0057] <Antioxidant> The adhesive composition of the present invention may contain an antioxidant as needed. The incorporation of an antioxidant is preferred because it can prevent deterioration of properties such as adhesiveness and dielectric properties even when the adhesive composition is used in a high-temperature environment exposed to air. The antioxidant is not particularly limited, but examples include phenol-based antioxidants, amine-based antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants. These may be used alone or in combination of two or more.

[0058] When the adhesive composition contains an antioxidant, the content thereof is preferably 0.5 to 5 parts by mass, and more preferably 1 to 3 parts by mass, per 100 parts by mass of the solid content of the adhesive composition. When the content of the antioxidant is within the above range, deterioration of properties such as adhesiveness and dielectric properties can be suppressed even when the adhesive composition is used in a high-temperature environment where it is exposed to air.

[0059] <Silane Coupling Agent> The adhesive composition of the present invention may contain a silane coupling agent as needed. The inclusion of a silane coupling agent is highly preferred because it improves adhesion to metals and heat resistance. Silane coupling agents are not particularly limited, but examples include those containing unsaturated groups, epoxy groups, and amino groups. Among these, silane coupling agents containing epoxy groups, such as γ-glycidoxypropyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and β-(3,4-epoxycyclohexyl)ethyltriethoxysilane, are more preferred from the perspective of heat resistance. When a silane coupling agent is included, the amount is preferably 0.5 to 20 parts by mass per 100 parts by mass of the total of the polyimide resin, oxazoline group-containing polystyrene (A), and epoxy resin (B). By using a silane coupling agent within this range, solder heat resistance and adhesion can be improved.

[0060] <Laminate> The laminate of the present invention is a laminate in which an adhesive composition is laminated on a substrate, specifically, a laminate in which the adhesive composition is laminated on a substrate (a two-layer laminate of substrate / adhesive layer), or a laminate in which a substrate is further attached (a three-layer laminate of substrate / adhesive layer / substrate). Here, the adhesive layer refers to the layer of the adhesive composition of the present invention after the adhesive composition of the present invention is applied to a substrate and dried. The laminate of the present invention can be obtained by applying the adhesive composition of the present invention to various substrates according to a conventional method, drying it, and then laminating another substrate on it.

[0061] <Substrate> In the present invention, the substrate is not particularly limited as long as it is possible to form an adhesive layer by applying and drying the adhesive composition of the present invention, and examples thereof include resin substrates such as film-like resins, metal substrates such as metal plates and metal foils, and paper.

[0062] Examples of the resin substrate include polyimide resin, polyamide resin, polyimide resin, polyamideimide resin, liquid crystal polymer, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resin, and fluorine-based resin. A film-like resin (hereinafter also referred to as a substrate film layer) is preferred.

[0063] Any conventionally known conductive material usable for circuit boards can be used as the metal substrate. Examples of materials include various metals such as SUS, copper, aluminum, iron, steel, zinc, and nickel, as well as their alloys, plated products, and metals treated with other metals such as zinc or chromium compounds. Metal foil is preferred, and copper foil is more preferred. The thickness of the metal foil is not particularly limited, but is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 10 μm or more. It is also preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 20 μm or less. If the thickness is too thin, it may be difficult to obtain sufficient electrical performance of the circuit, while if the thickness is too thick, processing efficiency during circuit fabrication may be reduced. 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 a ribbon-shaped metal foil is used, its length is not particularly limited. Its width is also not particularly limited, but is preferably about 250 to 500 cm. The surface roughness of the substrate is not particularly limited, but is preferably 3 μm or less, more preferably 2 μm or less, and even more preferably 1.5 μm or less. In practical terms, it is preferably 0.3 μm or more, more preferably 0.5 μm or more, and even more preferably 0.7 μm or more.

[0064] Examples of the paper include fine paper, kraft paper, roll paper, glassine paper, etc. Examples of the composite material include glass epoxy, etc.

[0065] In terms of adhesive strength with the adhesive composition and durability, the substrate is preferably a polyimide resin, a polyamide resin, a polyimide resin, a polyamideimide resin, a liquid crystal polymer, polyphenylene sulfide, syndiotactic polystyrene, a polyolefin resin, a fluorine-based resin, an SUS steel plate, a copper foil, an aluminum foil, or a glass epoxy.

[0066] <Adhesive Sheet> In the present invention, the adhesive sheet is formed by laminating the substrate and a release substrate via an adhesive composition. Specific configurations include substrate / adhesive layer / release substrate, or release substrate / adhesive layer / substrate / adhesive layer / release substrate. Laminating the release substrate functions as a protective layer for the substrate. Furthermore, by using a release substrate, the release substrate can be released from the adhesive sheet and the adhesive layer can be transferred to another substrate.

[0067] The adhesive sheet of the present invention can be obtained by applying the adhesive composition of the present invention to various laminates and drying them according to conventional methods. Furthermore, by attaching a release substrate to the adhesive layer after drying, the adhesive can be wound up without causing offset onto the substrate, resulting in excellent operability, and the adhesive layer is protected, resulting in excellent storage stability and ease of use. Furthermore, after application to a release substrate and drying, the adhesive layer itself can be transferred to another substrate by attaching another release substrate as needed.

[0068] <Release Substrate> The release substrate is not particularly limited, but examples include paper such as fine paper, kraft paper, roll paper, and glassine paper, on both sides of which a coating layer of a filler such as clay, polyethylene, or polypropylene is provided, and each of these coating layers is further coated with a silicone-based, fluorine-based, or alkyd-based release agent. Other examples include various olefin films such as polyethylene, polypropylene, ethylene-α-olefin copolymer, and propylene-α-olefin copolymer alone, and films such as polyethylene terephthalate coated with the above-mentioned release agent. Due to factors such as the release force between the release substrate and the adhesive layer and the adverse effect of silicone on electrical properties, it is preferable to use a polypropylene-sealed film on both sides of fine paper and then apply an alkyd-based release agent thereon, or a polyethylene terephthalate film on which an alkyd-based release agent is applied.

[0069] In the present invention, the method for coating the adhesive composition on a substrate is not particularly limited, but examples include a comma coater, reverse roll coater, die coater, etc. Alternatively, if necessary, an adhesive layer can be applied directly or by transfer method to rolled copper foil or polyimide film, which are components of printed wiring boards. The thickness of the adhesive layer after drying can be adjusted as needed, but is preferably in the range of 5 to 200 μm. By making the adhesive film thickness 5 μm or more, sufficient adhesive strength can be obtained. Furthermore, by making the thickness 200 μm or less, it is easier to control the amount of residual solvent during the drying process, and blisters are less likely to occur during pressing in the production of printed wiring boards. While the drying conditions are not particularly limited, a residual solvent ratio of 1% by mass or less after drying is preferred. By making the residual solvent thickness 1% by mass or less, blisters due to residual solvent are suppressed during pressing of the printed wiring board, making blisters less likely to occur.

[0070] <Printed Wiring Board> The printed wiring board of the present invention includes, as a component, a laminate formed from a metal foil forming a conductor circuit and a resin substrate. The printed wiring board is manufactured by a conventionally known method such as a subtractive method using a metal-clad laminate, for example. The term "printed wiring board" collectively refers to so-called flexible circuit boards (FPCs), flat cables, circuit boards for tape automated bonding (TAB), etc., in which a conductor circuit formed from metal foil is partially or entirely covered with a cover film, screen printing ink, etc., as necessary.

[0071] The printed wiring board of the present invention can have any laminated structure that can be used as a printed wiring board. For example, it can be a printed wiring board consisting of four layers: a base film layer, a metal foil layer, an adhesive layer, and a cover film layer. Alternatively, it can be a printed wiring board consisting of five layers: a base film layer, an adhesive layer, a metal foil layer, an adhesive layer, and a cover film layer.

[0072] Furthermore, if necessary, two or more of the above printed wiring boards may be stacked.

[0073] The adhesive composition of the present invention can be suitably used in each adhesive layer of a printed wiring board. In particular, when the adhesive composition of the present invention is used as an adhesive, it exhibits high adhesion not only to conventional polyimide, polyester film, and copper foil constituting printed wiring boards, but also to low-polarity resin substrates such as LCP, and can achieve solder reflow resistance, and the adhesive layer itself has excellent low dielectric properties. Therefore, it is suitable as an adhesive composition for use in coverlay films, laminates, resin-coated copper foils, and bonding sheets.

[0074] In the printed wiring board of the present invention, any resin film conventionally used as a substrate for printed wiring boards can be used as the substrate film. Examples of resins for the substrate film include polyimide resins, polyamide resins, polyimide resins, polyamideimide resins, liquid crystal polymers, polyphenylene sulfide, syndiotactic polystyrene, polyolefin-based resins, and fluorine-based resins. In particular, the film has excellent adhesion to low-polarity substrates such as liquid crystal polymers, polyphenylene sulfide, syndiotactic polystyrene, and polyolefin-based resins.

[0075] <Cover film> As the cover film, any insulating film conventionally known as an insulating film for printed wiring boards can be used. For example, films made from various polymers such as polyimide, polyester, polyphenylene sulfide, polyethersulfone, polyetheretherketone, aramid, polycarbonate, polyarylate, polyamideimide, liquid crystal polymer, syndiotactic polystyrene, and polyolefin resin can be used. Polyimide film or liquid crystal polymer film is more preferred.

[0076] The printed wiring board of the present invention can be manufactured by any conventionally known process, except for using the materials for each layer described above.

[0077] In a preferred embodiment, a semi-finished product is produced in which an adhesive layer is laminated on a cover film layer (hereinafter referred to as a "cover film side semi-finished product"). On the other hand, a semi-finished product is produced in which a metal foil layer is laminated on a base film layer to form a desired circuit pattern (hereinafter referred to as a "base film side two-layer semi-finished product"), or a semi-finished product is produced in which an adhesive layer is laminated on a base film layer and a metal foil layer is laminated on top of it to form a desired circuit pattern (hereinafter referred to as a "base film side three-layer semi-finished product"). The thus obtained cover film side semi-finished product and the base film side semi-finished product are bonded together to obtain a four-layer or five-layer printed wiring board.

[0078] The substrate film-side semi-finished product can be obtained, for example, by a manufacturing method including: (A) a step of applying a solution of a resin that will become the substrate film to the metal foil and initially drying the coating film; and (B) a step of heat-treating and drying the laminate of the metal foil and the initially dried coating film obtained in (A) (hereinafter referred to as the "heat treatment / solvent removal step").

[0079] The circuit can be formed on the metal foil layer by a conventionally known method. Either an additive method or a subtractive method may be used. The subtractive method is preferred.

[0080] The obtained semi-finished product on the base film side may be used as it is for bonding to the semi-finished product on the cover film side, or may be used for bonding to the semi-finished product on the cover film side after a release film has been attached and stored.

[0081] The cover film semi-finished product is produced, for example, by applying an adhesive to the cover film. If necessary, a crosslinking reaction can be carried out in the applied adhesive. In a preferred embodiment, the adhesive layer is semi-cured.

[0082] The obtained cover film side semi-finished product may be used as it is for bonding to the base film side semi-finished product, or may be used for bonding to the base film side semi-finished product after a release film has been attached and stored.

[0083] The substrate film-side semi-finished product and the cover film-side semi-finished product are stored, for example, in the form of a roll, and then bonded together to produce a printed wiring board. Any bonding method can be used, and for example, they can be bonded together using a press or a roll. They can also be bonded together while heating them using a heat press or a heat roll device.

[0084] For example, in the case of a reinforcing material that is soft and can be wound up, such as a polyimide film, the reinforcing material semi-finished product is preferably produced by applying an adhesive to the reinforcing material. Furthermore, in the case of a reinforcing plate that is hard and cannot be wound up, such as a metal plate such as SUS or aluminum, or a plate made of glass fiber cured with an epoxy resin, it is preferably produced by transfer coating an adhesive that has been applied in advance to a release substrate. If necessary, a crosslinking reaction can be carried out in the applied adhesive. In a preferred embodiment, the adhesive layer is semi-cured.

[0085] The obtained semi-finished product on the reinforcing material side may be used as it is for bonding to the rear surface of a printed wiring board, or may be used for bonding to a semi-finished product on the base film side after a release film has been attached and stored.

[0086] The base film side semi-finished product, the cover film side semi-finished product, and the reinforcing material side semi-finished product are all laminates for printed wiring boards of the present invention.

[0087] This application claims the benefit of priority based on Japanese Patent Application No. 2023-118372, filed on July 20, 2023. The entire contents of the specification of Japanese Patent Application No. 2023-118372, filed on July 20, 2023, are incorporated herein by reference.

[0088] The present invention will be described in more detail below with reference to examples. In these examples and comparative examples, "parts" simply refers to parts by mass.

[0089] <Physical Property Evaluation Method> (Acid Value Measurement) 0.2 g of a polyimide resin sample was dissolved in 40 ml of chloroform, and titrated with a 0.01 N potassium hydroxide ethanol solution to obtain 10% of the polyimide resin. 6 Equivalents per g (equivalents / 10 6 g) was determined. Phenolphthalein was used as the indicator.

[0090] (Measurement of Glass Transition Temperature) Measurement was performed using a differential scanning calorimeter (SII, DSC-200). 5 mg of a sample was placed in an aluminum container with a lid, sealed, and cooled to -50°C using liquid nitrogen. The sample was then heated to 150°C at a heating rate of 20°C / min. The endothermic curve obtained during the heating process was analyzed to determine the glass transition temperature (unit: °C) as the temperature at the intersection of an extension of the baseline before the endothermic peak appears (below the glass transition temperature) and a tangent to the endothermic peak (a tangent showing the maximum slope from the rising part of the peak to the peak apex).

[0091] The following describes examples of producing adhesive compositions according to the present invention and comparative examples.

[0092] The polyimide resin was produced as follows. (Production Example 1) 53 parts of 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 185.5 parts of cyclohexanone, and 37.1 parts of methylcyclohexane were charged into a four-necked flask equipped with a thermometer, a condenser, and a nitrogen gas inlet tube, and the solution was heated to 60°C. Next, 85.4 parts of dimer diamine (PRIAMINE 1075, manufactured by Croda) was added dropwise, and an imidization reaction was carried out at 140°C for 1 hour to obtain a polyimide resin solution (glass transition temperature 70°C, acid value 146 equivalents / 10 6 The dielectric constant was 2.6 and the dielectric loss tangent was 0.0019.

[0093] The following oxazoline group-containing polystyrene (A) was used: Oxazoline group-containing polystyrene: EPOCROS RPS-1005 (manufactured by Nippon Shokubai, weight average molecular weight 160,000, oxazoline group amount 0.27 mmol / g)

[0094] The following epoxy resin (B) was used: Epoxy resin: EP-3950E (manufactured by ADEKA, triglycidyl paraaminophenol)

[0095] Example 1: 60 parts of oxazoline group-containing polystyrene (A), 40 parts of the polyimide resin, and 1 part of epoxy resin (B) were blended and dissolved in toluene to a solids concentration of 30% to obtain a toluene adhesive composition (S1). The obtained adhesive composition (S1) was evaluated for its dielectric constant, dielectric loss tangent, peel strength, and solder heat resistance. The results are shown in Table 1.

[0096] Examples 2 and 3, Comparative Examples 1 to 5 Adhesive compositions (S2) to (S8) were prepared and evaluated in the same manner as in Example 1, except that the types and amounts of each component of the adhesive composition were changed as shown in Tables 1 and 2. The results are shown in Tables 1 and 2.

[0097] <Evaluation of Adhesive Composition> (Dielectric Constant (εc) and Dielectric Loss Tangent (tanδ)) The adhesive composition was applied to a 100 μm thick Teflon (registered trademark) sheet so that the thickness after drying was 25 μm, and then dried at 130°C for 3 minutes. The composition was then cured by heat treatment at 180°C for 3 hours, and the Teflon (registered trademark) sheet was peeled off to obtain an adhesive resin sheet for testing. The obtained adhesive resin sheet for testing was then cut into strips measuring 8 cm x 3 mm to obtain test samples. The dielectric constant (εc) and dielectric loss tangent (tanδ) were measured using a network analyzer (manufactured by Anritsu Corporation) by a cavity resonator perturbation method at a temperature of 23°C and a frequency of 10 GHz. <Evaluation criteria for relative dielectric constant> ○: Less than 2.5 △: 2.5 to 2.7 ×: More than 2.7 <Evaluation criteria for dielectric loss tangent> ○: 0.002 or less △: More than 0.002 to 0.003 ×: More than 0.003

[0098] (Peel Strength (Adhesion)) The adhesive composition was applied to a 12.5 μm thick polyimide film (Apical (registered trademark), manufactured by Kaneka Corporation) so that the dried thickness would be 25 μm, and then dried at 130°C for 3 minutes. The adhesive film (B-stage product) thus obtained was then bonded to an 18 μm thick rolled copper foil (ESPANEX series, manufactured by Nippon Steel Chemical & Material Co., Ltd.). The bonding was performed by pressing the rolled copper foil with the shiny side in contact with the adhesive layer at 170°C under a pressure of 2 MPa for 280 seconds to bond the foil. The foil was then heat-treated at 180°C for 3 hours to cure the film, and a sample for peel strength evaluation was obtained. The peel strength was measured at 25°C, with a film pull speed of 50 mm / min and a 90° peel angle. This test indicates the adhesive strength at room temperature. <Evaluation criteria> ○: 1.0 N / mm or more △: 0.7 N / mm or more and less than 1.0 N / mm ×: Less than 0.7 N / mm

[0099] (Soldering heat resistance) Evaluation samples were prepared in the same manner as for measuring peel strength, and 2.0 cm x 2.0 cm sample pieces were immersed in a solder bath molten at 288°C, and the presence or absence of changes in appearance such as blistering was confirmed. <Evaluation criteria> ○: No blistering for 60 seconds or more △: Blistering for 30 seconds or more but less than 60 seconds ×: Blistering for less than 30 seconds

[0100]

[0101]

[0102] As is clear from Table 1, Examples 1 to 3 are excellent in dielectric properties, peel strength, and solder heat resistance. Furthermore, a comparison of Examples 1 to 3 shows that the dielectric properties, peel strength, and solder heat resistance can be changed by adjusting the content ratio of the polyimide resin, the oxazoline group-containing polystyrene (A), and the epoxy resin (B).

[0103] On the other hand, in Comparative Example 1, the absence of oxazoline group-containing polystyrene (A) resulted in insufficient crosslinking, resulting in poor dielectric dissipation factor and poor soldering heat resistance. Comparative Example 2 contained a larger amount of epoxy resin (B) than Comparative Example 1, resulting in excellent soldering heat resistance, but on the other hand, the generation of more hydroxyl groups resulted in poor dielectric dissipation factor. Comparative Example 3 contained less epoxy resin (B) than Example 1, resulting in fewer polar groups interacting with the acid-modified resin substrate, resulting in poor peel strength and soldering heat resistance. In Comparative Example 4, the ratio of oxazoline group-containing polystyrene (A) to the polyimide resin was too low, resulting in insufficient crosslinking, resulting in poor dielectric dissipation factor and poor soldering heat resistance. In Comparative Example 5, the ratio of oxazoline group-containing polystyrene (A) to the polyimide resin was too high, resulting in relatively few polar groups interacting with the acid-modified resin substrate, resulting in poor peel strength and soldering heat resistance.

[0104] The adhesive composition of the present invention has excellent solder heat resistance and adhesive strength, and a good dielectric constant and dielectric loss tangent, and is therefore useful as an adhesive or adhesive sheet for FPCs in the high frequency range.

Claims

1. Acid value is 10 equivalents / 10 6 g or more 1000 equivalents / 10 6 1. An adhesive composition comprising a polyimide resin having a molecular weight of 100 g or less, an oxazoline group-containing polystyrene (A) and an epoxy resin (B), wherein a content of the oxazoline group-containing polystyrene (A) is 12 parts by mass or more and 1,000 parts by mass or less per 100 parts by mass of the polyimide resin.

2. The adhesive composition according to claim 1, wherein the content of the epoxy resin (B) is 0.1 parts by mass or more and 30 parts by mass or less per 100 parts by mass of the oxazoline group-containing polystyrene (A).

3. The adhesive composition according to claim 1 or 2, wherein the oxazoline group-containing polystyrene (A) is a resin obtained by copolymerizing a styrene-based monomer with an oxazoline group-containing monomer.

4. The adhesive composition according to claim 3, wherein said styrene-based monomer is styrene.

5. The adhesive composition according to claim 3, wherein the oxazoline group-containing monomer is at least one member selected from the group consisting of 2-isopropenyl-2-oxazoline, 4,4-dimethyl-2-isopropenyl-2-oxazoline, 4-ethyl-4-hydroxymethyl-2-isopropenyl-2-oxazoline and 4-ethyl-4-ethoxycarbonylethyl-2-isopropenyl-2-oxazoline.

6. The adhesive composition according to claim 1 or 2, wherein the amount of oxazoline groups in the oxazoline group-containing polystyrene (A) is 0.10 to 0.50 mmol / g.

7. The adhesive composition according to claim 1 or 2, wherein the weight average molecular weight (Mw) of the oxazoline group-containing polystyrene (A) is 10,000 or more and 1,000,000 or less.

8. The adhesive composition according to claim 1 or 2, wherein the epoxy resin (B) is a multifunctional epoxy resin.

9. The adhesive composition according to claim 8, wherein the multifunctional epoxy resin is one or more glycidyl amine type epoxy resins selected from the group consisting of N,N,N',N'-tetraglycidyl-4,4'-diaminodiphenylmethane, triglycidyl para-aminophenol, 1,3-bis(diglycidylaminomethyl)cyclohexane and N,N,N',N'-tetraglycidyl-m-xylylenediamine.

10. The adhesive composition according to claim 1 or 2, which is for use on a printed wiring board.

11. An adhesive sheet comprising a resin substrate, a metal substrate or a paper substrate and a release substrate laminated together via the adhesive composition according to claim 1 or 2.

12. A laminate in which the adhesive composition according to claim 1 or 2 is laminated to a substrate which is a resin substrate, a metal substrate or a paper substrate.

13. A printed wiring board comprising the laminate according to claim 12 as a component.

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