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

Abstract

The purpose of the present invention is to provide: an adhesive composition that has a good appearance and exhibits excellent adhesiveness and excellent low-dielectric characteristics even after a long-term heat resistance test at 125°C for 1,000 h; and an adhesive sheet, a laminate, and a printed wiring board containing the same.　This adhesive composition is characterized by comprising a polyimide resin, an antioxidant (A), a heavy metal deactivator (B), and an epoxy resin (C), wherein the antioxidant (A) content is 1.0 parts by mass or less and the heavy metal deactivator (B) content is 1.0 parts by mass or less relative to 100 parts by mass of the polyimide resin.

Description

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

[0001] The present invention relates to an adhesive composition, and more particularly to an adhesive composition for printed wiring boards used for bonding to substrates.

[0002] In recent years, electronic devices have become smaller, lighter, more dense, and more powerful, and the performance requirements for printed wiring boards (electronic circuit boards) have become increasingly stringent. In particular, high-frequency signals have come to be used to increase transmission speeds, and printed wiring boards are increasingly required to have low dielectric properties (low dielectric constant, low dielectric loss tangent) in the high-frequency range. In order to achieve such low dielectric properties, new substrates and adhesive compositions for printed wiring boards have been developed.

[0003] For rigid circuit board materials, low-dielectric resins such as fluororesins are increasingly being used instead of conventional Flame Retardant Type 4 (FR-4), and for flexible printed circuit boards (FPCs), films with low dielectric properties, such as liquid crystal polymers (LCPs) and fluororesins, are increasingly being used instead of conventional polyimide films.As adhesive compositions for laminating these low-dielectric resins and copper-clad laminates (CCLs) containing them, development is underway for adhesive compositions that combine polypropylene-based resins and epoxy resins (Patent Document 1) and adhesive compositions containing styrene-based elastomers (Patent Document 2).

[0004] JP 2022-164870 A JP 2023-032287 A

[0005] Recently, the development of autonomous vehicles has become more active. Millimeter-wave radar, one of the core sensors for autonomous driving, is known for its ability to measure the distance, speed, angle, etc., of distant objects. Because high-frequency signals are used around millimeter-wave radar antennas, adhesive compositions for printed wiring boards are strongly required to have low dielectric properties to reduce transmission loss. Furthermore, for applications requiring high reliability, such as automotive millimeter-wave radar antennas, adhesive compositions are required to maintain their adhesiveness and low dielectric properties even after being placed in harsh environments such as high-temperature environments (125°C) and high-temperature, high-humidity environments (85°C, 85% RH) for 1,000 hours or more.

[0006] In this regard, the present inventors have investigated adhesive compositions containing polypropylene-based resins and styrene-based elastomers disclosed in Patent Documents 1 and 2, and have found that these resins undergo oxidative degradation when placed in a high-temperature environment for a period of time, resulting in various problems, such as a significant decrease in peel strength in the adhesive composition and deterioration of dielectric properties (dielectric constant, etc.) due to an increase in highly polar groups. In particular, adhesive compositions for printed wiring boards come into contact with metal substrates such as copper foil, and the generation of heavy metal ions, such as copper ions, accelerates the oxidative degradation of the resin. Furthermore, when compared between placement in a high-temperature environment (125°C) for 1000 hours or more and placement in a high-temperature, high-humidity environment (85°C, 85% RH) for 1000 hours or more, the resin is more likely to oxidize in the former environment, which can be considered a more severe test for adhesive compositions. Demand for highly reliable electronic devices continues to increase, and adhesive compositions that can withstand more severe tests are needed.

[0007] 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 exhibits good appearance, excellent adhesion, and excellent low dielectric properties even after a long-term heat resistance test at 125°C for 1000 hours, as well as an adhesive sheet, a laminate, and a printed wiring board that contain the same.

[0008] 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.

[0009] [1] An adhesive composition comprising a polyimide resin, an antioxidant (A), a heavy metal deactivator (B), and an epoxy resin (C), wherein the content of the antioxidant (A) is 1.0 part by mass or less and the content of the heavy metal deactivator (B) is 1.0 part by mass or less per 100 parts by mass of the polyimide resin. [2] The adhesive composition according to [1], wherein the heavy metal deactivator (B) comprises at least one of a hydrazine-based heavy metal deactivator and a phosphite-based heavy metal deactivator. [3] The adhesive composition according to [1] or [2], wherein the heavy metal deactivator (B) has a chemical structure represented by formula (II) in its molecule. [In formula (II), * represents a bond, and R 4 ~R 6 are each independently a hydrogen atom or C 1-10 represents an alkyl group.] [4] The adhesive composition according to any one of [1] to [3], wherein the content of the heavy metal deactivator (B) is 1 to 200 parts by mass per 100 parts by mass of the antioxidant (A). [5] The adhesive composition according to any one of [1] to [4], wherein the content of the heavy metal deactivator (B) is 0.01 parts by mass or more per 100 parts by mass of the polyimide resin. [6] The adhesive composition according to any one of [1] to [5], wherein the antioxidant (A) is one or more selected from the group consisting of phenol-based antioxidants, sulfur-based antioxidants, amine-based antioxidants, and phosphorus-based antioxidants. [7] The adhesive composition according to any one of [1] to [6], wherein the antioxidant (A) has a chemical structure represented by formula (I) in its molecule. [In formula (I), * represents a bond, R 1 ~R 3 are each independently a hydrogen atom or C 1-10 [8] The adhesive composition according to any one of [1] to [7], wherein the epoxy resin (C) is a polyfunctional epoxy resin. [9] The epoxy value of the epoxy resin (C) is 5,000 to 12,000 equivalents / 10 6g.

[10] The adhesive composition according to any one of [1] to [9], wherein the epoxy resin (C) is at least one selected from the group consisting of glycidylamine-type epoxy resins, glycidyl group-containing isocyanuric acid resins, and alicyclic epoxy resins.

[11] The adhesive composition according to any one of [1] to

[10] , which is for use on printed wiring boards.

[12] An adhesive sheet in which the adhesive composition according to any one of [1] to

[10] is laminated on a release substrate.

[13] A laminate in which the adhesive composition according to any one of [1] to

[10] is laminated on a substrate which is a resin substrate, a metal substrate, paper, or an inorganic non-metallic substrate.

[14] A printed wiring board comprising the laminate according to

[13] as a component.

[0010] According to the present invention, an adhesive composition is provided that exhibits good appearance, excellent adhesion, and excellent low dielectric properties even after a long-term heat resistance test at 125°C for 1,000 hours. Furthermore, the adhesive composition of the present invention is also excellent in solder heat resistance, adhesion, and initial low dielectric properties. Therefore, the adhesive composition is suitable for use in adhesive compositions for printed wiring boards in the high-frequency range, as well as adhesive sheets, laminates, and printed wiring boards containing the same.

[0011] <Adhesive Composition> The present invention relates to an adhesive composition comprising a polyimide resin, an antioxidant (A), a heavy metal deactivator (B), and an epoxy resin (C), wherein the content of the antioxidant (A) is 1.0 part by mass or less and the content of the heavy metal deactivator (B) is 1.0 part by mass or less, relative to 100 parts by mass of the polyimide resin. In the present invention, by incorporating the antioxidant (A) and the heavy metal deactivator (B) in the adhesive composition and setting their contents to predetermined amounts or less, degradation of the polyimide resin due to oxidation is suppressed, and an adhesive composition is provided that exhibits good appearance, excellent adhesion, and excellent low dielectric properties even after a long-term heat resistance test at 125°C for 1,000 hours.

[0012] <Polyimide Resin> The polyimide resin in the present invention is a polymer having an imide bond in the main chain, and is produced by a method such as a method of producing 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), or a method of reacting a compound having a carboxylic acid anhydride and an acid chloride with a diamine. The direct method is advantageous in terms of the wide range of options for monomer components.

[0013] 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.

[0014] 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 of two or more. From the viewpoint of dielectric properties, tetrabasic acid dianhydrides having an aromatic ring and alicyclic tetrabasic acid dianhydrides are preferred, with 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride and 2,2-bis[4-(2,3- or 3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA) being more preferred.

[0015] 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 of two or more.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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 preferably 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 increases, the adhesive strength improves, and the crosslink density increases, thereby improving the heat resistance. The upper limit is preferably 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.

[0021] 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.

[0022] The polyimide resin in the present invention preferably has a relative dielectric constant (εc) of 3.0 or less at a frequency of 40 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.

[0023] The polyimide resin in the present invention preferably has a dielectric loss tangent (tan δ) of 0.005 or less at a frequency of 40 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] The polyimide resin is preferably contained as a main component in the adhesive composition. In this specification, the main component in the adhesive composition specifically refers to the component with the highest content in the solid content of the adhesive composition. 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, even more preferably 30% by mass or more, even more preferably 40% by mass or more, and particularly preferably 50% by mass or more, based on 100% by mass of the solid content of the adhesive composition. Furthermore, the content is preferably 99.5% by mass or less, more preferably 99.0% by mass or less, and even more preferably 98.5% by mass or less. Being within the above range is preferable because it results in good adhesion and heat resistance.

[0029] <Antioxidant (A)> The adhesive composition of the present invention contains an antioxidant (A). By containing the antioxidant (A), thermal degradation of the polyimide resin can be suppressed even in a high-temperature environment in the presence of oxygen, and changes in adhesion and low dielectric properties can be suppressed after a long-term heat resistance test.

[0030] The antioxidant (A) is not particularly limited as long as it can suppress thermal degradation of the polyimide resin, and examples thereof include phenol-based antioxidants, sulfur-based antioxidants, amine-based antioxidants, phosphorus-based antioxidants, etc. These can be used alone or in combination of two or more kinds.

[0031] Examples of phenolic antioxidants include 2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diyl)bis(2-methylpropane-2,1-diyl)bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propanoate], 2,6-di-tert-butyl-p-cresol, 2,4,6-tri-tert-butylphenol, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propanoate ... diphenyl)propionate, ethylene glycol bis[3,3-bis(3-tert-butyl-4-hydroxyphenyl)butyrate], 2,6-di-tert-butyl-4-hydroxymethylphenol, 2,5-di-tert-butylhydroquinone, 2,2'-methylene-bis-(4-methyl-6-tert-butylphenol), 2,2'-methylene-bis-(4-ethyl-6-tert-butylphenol), 2,2'-methylene bis(4-methyl-6-cyclohexylphenol), 2,2'-methylenebis(4-methyl-6-nonylphenol), 4,4'-isopropylidenebisphenol, 4,4'-butylidene-bis(3-methyl-6-tert-butylphenol), 1,1-bis-(4-hydroxy-phenyl)cyclohexane, 4,4'-methylenebis-(2,6-di-tert-butylphenol), 2,6-bis(2'-hydroxy-3' 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, tetrakis[methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate]methane, and the like.

[0032] Examples of sulfur-based antioxidants include pentaerythritol tetrakis-(3-laurylthiopropionate), dilaurylthiodipropionate, dimyristylthiodipropionate, distearylthiodipropionate, and bis(2-hydroxy-1-naphthyl)sulfide.

[0033] Examples of the amine antioxidant include 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, phenyl-α-naphthylamine, phenyl-β-naphthylamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-β-naphthyl-p-phenylenediamine, N-cyclohexyl-N'-phenyl-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, aldol-α-naphthylamine, a polymer of 2,2,4-trimethyl-1,2-dihydroquinone, and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline.

[0034] Examples of phosphorus-based antioxidants include 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, triphenyl phosphite, 2-ethylhexyl acid phosphate, dilauryl phosphite, tri-iso-octyl phosphite, tris(2,4-di-tert-butylphenyl)phosphite, trilauryl phosphite, trilauryl-di-thiophosphite, trilauryl-tri-thiophosphite, trisnonylphenyl phosphite, distearyl pentaerythritol diphosphite, tris(mononylphenyl)phosphite, tris(dinonylphenyl)phosphite, trioctadecyl phosphite, 1,1,3-tris(2-methyl-di-tridecylphosphite-5-tert-butylphenyl)butane, 4,4'-butylidene-bis(3-methyl-6-tert-butyl)tridecyl sil phosphite, 4,4'-butylidene-bis(3-methyl-6-tert-butyl-di-tridecyl) phosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol-di-phosphite, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol-di-phosphite, tetrakis(2,4-di-tert-butylphenyl)4,4'-bisphenylene diphosphite, distearyl pentaerythritol diphosphite, tridecyl phosphite, tristearyl phosphite, 2,2'-methylenebis(4,6-di-tert-butylphenyl)octyl phosphite, sorbitol-tris-phosphite-distearyl-mono-C30-diol ester, bis(2,4,6-tri-tert-butylphenyl)pentaerythritol diphosphite, and the like.

[0035] From the viewpoint of long-term heat resistance, the antioxidant (A) preferably contains at least one of a phenol-based antioxidant and a sulfur-based antioxidant, and more preferably contains both a phenol-based antioxidant and a sulfur-based antioxidant.

[0036] The antioxidant (A) (preferably a phenolic antioxidant) is preferably one having a chemical structure represented by formula (I) in the molecule. [In formula (I), * represents a bond, R1 ~R 3 are each independently a hydrogen atom or C 1-10 represents an alkyl group.]

[0037] R 1 ~R 3 C in 1-10 Alkyl group (-C n H 2n+1 , where n is an integer of 1 to 10) may be linear or branched, and is preferably C 1-6 alkyl group, more preferably C 1-4 It is preferably an alkyl group, more preferably a methyl group, an ethyl group, or a tert-butyl group. From the viewpoint of suppressing deterioration of the polyimide resin, R 1 ~R 3 Among them, R 1 ~R 2 is a hydrogen atom, and R 3 is C 1-10 An embodiment in which the group is an alkyl group is more desirable.

[0038] The content of the antioxidant (A) is 1.0 part by mass or less, more preferably 0.9 part by mass or less, even more preferably 0.8 part by mass or less, and even more preferably 0.7 part by mass or less, per 100 parts by mass of the polyimide resin. If the content exceeds the upper limit, the dielectric properties may deteriorate after a long-term heat resistance test. The content of the antioxidant (A) is preferably 0.01 part by mass or more, more preferably 0.05 part by mass or more, and even more preferably 0.1 part by mass or more, per 100 parts by mass of the polyimide resin. If the content is equal to or greater than the lower limit, degradation due to oxidation of the polyimide resin is suppressed, and the adhesive composition exhibits a good appearance, excellent adhesion, and excellent low dielectric properties even after a long-term heat resistance test.

[0039] <Heavy Metal Deactivator (B)> The adhesive composition of the present invention contains a heavy metal deactivator (B). In a high-temperature environment in the presence of oxygen, heavy metal ions such as copper ions are generated from metal substrates such as copper foil with which the adhesive composition comes into contact, regardless of humidity conditions. The generated heavy metal ions accelerate the oxidation of the polyimide resin, resulting in thermal degradation. Since the heavy metal deactivator (B) can trap the generated copper ions, the addition of the heavy metal deactivator (B) can suppress thermal degradation of the polyimide resin.

[0040] The heavy metal deactivator (B) is not particularly limited as long as it can trap heavy metal ions, and may be, for example, one that can form a chelate with heavy metal ions. Examples of heavy metal deactivators (B) include hydrazine-based heavy metal deactivators, phosphite-based heavy metal deactivators, dibasic acid-based heavy metal deactivators, amino acid-based heavy metal deactivators, and triazole-based heavy metal deactivators. These may be used alone or in combination of two or more.

[0041] Hydrazine-based heavy metal deactivators are heavy metal deactivators that have a hydrazine structure (*-NH-NH-*) in the molecule. Hydrazine-based heavy metal deactivators include hydrazine derivatives and those obtained by dehydration condensation of hydrazine derivatives with oxoacids, specifically N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, 1,2-bis(3,5-di-tert-butyl-4-hydroxyhydrocinnamoyl)hydrazine, bis(2-phenoxypropionylhydrazine) isophthalate, bis(salicyloylhydrazine), and decamethylenedicarboxylic acid. Examples thereof include disalicyloyl hydrazide, isophthalic acid bis(2-phenoxypropionyl hydrazide), N'1,N'12-bis(2-hydroxybenzoyl)dodecane dihydrazide, decamethylenedicarboxylic acid bis(N'-salicyloyl hydrazide), oxalic acid bis(benzylidene hydrazide), thiodipropionic acid bis(benzylidene hydrazide), isophthalic acid bis(2-phenoxypropionyl hydrazide), and the like.

[0042] Examples of phosphite-based heavy metal deactivators include a reaction product of 2,2'-di-tert-butyl-5,5'-dimethyl-4,4'-sulfanediyldiphenol and phosphorus trichloride, bis[2-tert-butyl-4-thio(2'-methyl-4'-hydroxy-5'-tert-butylphenyl)-5-methylphenyl]-pentaerythritol-diphosphite, tetrakis[2-tert-butyl-4-thio(2'-methyl-4'-hydroxy-5'-tert-butylphenyl)-5-methylphenyl]-1,6-hexamethylene-bis(N-hydroxyethyl-N-methylsemicarbazide)-diphosphite, and tetrakis[2-tert-butyl-4-thio(2'-methyl-4'-hydroxy-5'-tert-butylphenyl)-5-methylphenyl]-N,N'-bis(hydroxyethyl)oxamide-diphosphite.

[0043] Examples of dibasic acid heavy metal deactivators include ethylenediaminetetraacetic acid.

[0044] Examples of amino acid-based heavy metal deactivators include 2-hydroxy-N-1H-1,2,4-triazol-3-ylbenzoamide, N,N-diethyl-N',N'-diphenyloxamide, N,N'-diethyl-N,N'-diphenyloxamide, N,N'-bis[2-[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxy]ethyl]oxamide, 2,4,6-triamino-1,3,5-triazine, and 3,9-bis[2-(3,5-diamino-2,4,6-triazaphenyl)ethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane.

[0045] Examples of triazole-based heavy metal deactivators include benzotriazole and 3-salicyloylamino-1,2,4-triazole.

[0046] From the viewpoint of low dielectric properties and long-term heat resistance, it is more preferable that the heavy metal deactivator (B) contains at least one of a hydrazine-based heavy metal deactivator and a phosphite-based heavy metal deactivator, and a hydrazine-based heavy metal deactivator is even more preferable.

[0047] The heavy metal deactivator (B) (preferably a hydrazine-based heavy metal deactivator) is also preferably one having a chemical structure represented by formula (II) in the molecule. [In formula (II), * represents a bond, and R 4 ~R 6 are each independently a hydrogen atom or C 1-10 represents an alkyl group.]

[0048] R 4 ~R 6 C in 1-10 Alkyl group (-C n H 2n+1 , where n is an integer of 1 to 10) may be linear or branched, and is preferably C 1-6 alkyl group, more preferably C 1-4 It is preferably an alkyl group, more preferably a methyl group, an ethyl group, or a tert-butyl group. From the viewpoint of suppressing deterioration of the polyimide resin, R 4 ~R 6 Among them, R 4 is a hydrogen atom, and R 5 ~R 6 Either one of them is C 1-10 An embodiment in which one is an alkyl group and the other is a hydrogen atom is more desirable.

[0049] The content of the heavy metal deactivator (B) is 1.0 part by mass or less, more preferably 0.9 part by mass or less, even more preferably 0.8 part by mass or less, and even more preferably 0.7 part by mass or less, per 100 parts by mass of the polyimide resin. If the content exceeds the upper limit, the dielectric properties may deteriorate after a long-term heat resistance test. The content of the heavy metal deactivator (B) is preferably 0.01 part by mass or more, more preferably 0.04 part by mass or more, and even more preferably 0.08 part by mass or more, per 100 parts by mass of the polyimide resin. If the content is equal to or greater than the lower limit, deterioration due to oxidation of the adhesive composition, particularly the polyimide resin, is suppressed, and the adhesive composition exhibits a good appearance, excellent adhesion, and excellent low dielectric properties even after a long-term heat resistance test.

[0050] The content of the heavy metal deactivator (B) is preferably 1 to 200 parts by mass, more preferably 5 to 100 parts by mass, even more preferably 10 to 70 parts by mass, and still more preferably 13 to 50 parts by mass, relative to 100 parts by mass of the antioxidant (A). By adjusting the content within this range, the adhesive composition can exhibit excellent low dielectric properties even after a long-term heat resistance test.

[0051] <Epoxy Resin (C)> The adhesive composition of the present invention contains an epoxy resin. The epoxy resin is not particularly limited as long as it is a multifunctional epoxy resin having two or more glycidyl groups in the molecule. By using an epoxy resin, the carboxyl group and the glycidyl group of the polyimide resin react to form a crosslinked structure, thereby improving the solder heat resistance and adhesiveness of the adhesive composition.

[0052] The epoxy value of the epoxy resin (C) is preferably 5,000 to 12,000 equivalents / 10 from the viewpoint of heat resistance and adhesion to resin substrates and metal substrates. 6 g, more preferably 6,000 to 11,000 equivalents / 10 6 g, more preferably 7,000 to 10,000 equivalents / 10 6 g. When the epoxy value is equal to or greater than the lower limit, the adhesive strength is improved, and the crosslinking density is increased, thereby improving heat resistance. When the epoxy value is equal to or less than the upper limit, the adhesiveness and low dielectric properties are improved. The epoxy value can be evaluated in accordance with the provisions of JIS K7236 (the same applies hereinafter).

[0053] The epoxy resin (C) is not particularly limited, but examples include 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, glycidyl ether-type epoxy resins, epoxy-modified polybutadiene, and glycidyl group-containing isocyanuric acid. These can be used alone or in combination of two or more. Among these, from the viewpoints of solder heat resistance and low dielectric properties, glycidylamine-type epoxy resins, glycidyl group-containing isocyanuric acid, and alicyclic epoxy resins are preferred, and glycidylamine-type epoxy resins and alicyclic epoxy resins are more preferred.

[0054] Specifically, a glycidylamine-type epoxy resin refers to an epoxy resin containing a glycidylamino group in which one or two glycidyl groups are bonded to an amino group within the molecule. More preferably, the glycidylamine-type epoxy resin includes at least one of an epoxy resin represented by formula (CA) (hereinafter sometimes simply referred to as epoxy resin (CA)) and an epoxy resin represented by formula (CB) (hereinafter sometimes simply referred to as epoxy resin (CB)). Because epoxy resins (CA) to (CB) contain two or more epoxy groups, they are advantageous for forming a high-density crosslinked structure. Furthermore, because the number of carbon atoms between the nitrogen atom and the epoxy group indirectly bonded thereto is small, epoxy resins (CA) to (CB) have a structure with significant steric hindrance and poor mobility. Such a structure with significant steric hindrance can suppress atomic movement, making it ideal for obtaining an adhesive composition with a low dielectric loss tangent.

[0055] [In formula (CA), R 11 ~R 15 are each independently a hydrogen atom, C 1-10 represents an alkyl group or a glycidyloxy group.]

[0056] [In formula (CB), R 16 ~R 23 are each independently a hydrogen atom, C 1-10represents an alkyl group or a glycidyloxy group. 24 ~R 25 are each independently a hydrogen atom or C 1-10 represents an alkyl group.]

[0057] R 11 ~R 25 C in 1-10 Alkyl group (-C n H 2n+1 , where n is an integer of 1 to 10) may be linear or branched. 1-10 The alkyl group is preferably C 1-6 alkyl group, more preferably C 1-3 It is an alkyl group, and even more preferably a methyl group or an ethyl group.

[0058] In formula (CA), R 11 and R 15 At least one of them is C 1-10 It is preferably an alkyl group. 11 and R 15 At least one of them is C 1-10 Alkyl groups act as steric hindrances that can inhibit the movement of polar groups, and are therefore effective in obtaining an adhesive composition with a low dielectric loss tangent. 11 ~R 15 Among them, R 11 and R 15 At least one of them is C 1-10 When it is an alkyl group, the C 1-10 Any group other than the alkyl group is preferably a hydrogen atom.

[0059] In formula (CB), R 16 ~R 23 Among these, preferably 3 or more, more preferably 5 or more, even more preferably 7 or more, and most preferably all 8 are hydrogen atoms. 24 ~R 25 At least one of these is preferably a hydrogen atom, and more preferably both of these are hydrogen atoms.

[0060] Examples of glycidylamine type epoxy resins include N,N-diglycidylaniline, N,N-(diglycidyl)-O-toluidine, N,N-(diglycidyl)-m-toluidine, N,N-(diglycidyl)-p-toluidine, N,N-diglycidyl-4-glycidyloxyaniline, N,N-(diglycidyl)-4-glycidyloxy-O-toluidine, and N,N-(diglycidyl)-4-glycidyloxy. Preferred are N,N-(diglycidyl)-4-glycidyloxy-m-toluidine, N,N-(diglycidyl)-4-glycidyloxy-p-toluidine, and 4,4'-methylenebis(N,N-diglycidylaniline), and more preferred are N,N-(diglycidyl)-O-toluidine, N,N-(diglycidyl)-m-toluidine, N,N-(diglycidyl)-p-toluidine, and 4,4'-methylenebis(N,N-diglycidylaniline).

[0061] Specifically, alicyclic epoxy resins refer to epoxy resins having reactive epoxy groups on an alicyclic skeleton, such as 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate.

[0062] The content of the epoxy resin (C) is preferably 0.01 parts by mass or more, more preferably 0.1 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 it to the lower limit or more, a sufficient curing effect can be obtained, and excellent adhesiveness and solder heat resistance can be exhibited. Also, it is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 6 parts by mass or less. By setting it to the upper limit or less, the pot life and low dielectric properties become good.

[0063] <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 reacts with the carbodiimide bond, thereby improving heat resistance and adhesiveness.

[0064] 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.

[0065] <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 generator 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.

[0066] 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.

[0067] 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 provides excellent dielectric properties. Among these, an unsaturated hydrocarbon preferably has an aromatic ring structure or an alicyclic structure as its skeleton, and polyphenylene ether or a cycloolefin polymer is preferable. 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. Furthermore, cycloolefin polymers having terminal unsaturated hydrocarbon groups can be obtained by copolymerizing an olefin monomer having an unsaturated bond with an alicyclic olefin monomer.

[0068] The number average molecular weight of the unsaturated hydrocarbon is preferably at least 500, more preferably at least 1000. Also, it is preferably at most 100,000, more preferably at most 10,000, and even more preferably at most 5,000. Within the above ranges, the solubility in solvents is good, and a uniform adhesive coating film can be formed.

[0069] 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 polyimide resin. It is also preferably 1,000 parts by mass or less, more preferably 500 parts by mass or less, even more preferably 200 parts by mass or less, and even more preferably 100 parts by mass or less. When a polyphenylene ether having a terminal unsaturated hydrocarbon group is used as the unsaturated hydrocarbon, it is preferably 200 parts by mass or less, more preferably 100 parts by mass or less, per 100 parts by mass of polyimide resin. Within the above ranges, excellent adhesion, compatibility with organic solvents, and solder heat resistance can all be achieved.

[0070] <Radical Generator> The adhesive composition of the present invention can contain a radical generator. Radicals generated by the radical generator efficiently react terminal unsaturated hydrocarbon groups of unsaturated hydrocarbons with each other, increasing crosslink density and improving solder heat resistance and dielectric properties. The radical generator is not particularly limited, but it is preferable to use an organic peroxide. 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.

[0071] 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 in the adhesive composition varnish is volatilized to produce an adhesive sheet, and excellent adhesiveness can be achieved.

[0072] 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 this range, an optimal crosslink density can be achieved, and both adhesiveness and solder heat resistance can be achieved.

[0073] <Organic Solvent> The adhesive composition of the present invention can 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, antioxidant (A), and heavy metal deactivator (B). When the adhesive composition of the present invention contains an organic solvent, it is desirable that the polyimide resin, antioxidant (A), and heavy metal deactivator (B) are uniformly dissolved in the organic solvent.

[0074] Specific examples of organic solvents include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as hexane, heptane, octane, and decane; alicyclic hydrocarbons such as cyclohexane, cyclohexene, methylcyclohexane, and ethylcyclohexane; halogenated hydrocarbons such as trichloroethylene, dichloroethylene, chlorobenzene, and chloroform; 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 such as methyl cellosolve and ethyl cellosolve, cellosolves such as methyl acetate, ethyl acetate, butyl acetate, methyl propionate, and butyl formate, and 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 can be used alone or in combination of two or more. In particular, methyl ethyl ketone, methylcyclohexane, and toluene are preferred in terms of working environment and drying properties.

[0075] 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.

[0076] 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.

[0077] <Flame Retardant> The adhesive composition of the present invention may contain a flame retardant as needed. Examples of flame retardants include bromine-based, phosphorus-based, nitrogen-based, and metal hydroxide compounds. Among these, phosphorus-based flame retardants are preferred, and phosphorus-based flame retardants such as phosphate esters, phosphate salts, and phosphine oxides can be used. These flame retardants can be used alone or in combination of two or more. When a flame retardant is contained, it is preferably contained in an amount of 1 to 70 mass%, more preferably 5 to 60 mass%, and most preferably 10 to 50 mass%, based on 100 mass% of the solids content of the adhesive composition. By keeping the amount within this range, flame retardancy can be achieved while maintaining adhesion, solder heat resistance, and electrical properties.

[0078] <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 can be used alone or in combination of two or more. When a tackifier is added, it is preferably contained in an amount of 1 to 70% by mass, more preferably 5 to 60% by mass, and most preferably 10 to 50% by mass, based on 100% by mass of the solids content of the adhesive composition. By keeping the amount within this range, the effects of the tackifier can be exerted while maintaining adhesion, solder heat resistance, and electrical properties.

[0079] <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.

[0080] While hydrophobic silica and hydrophilic silica are commonly known as silica, hydrophobic silica treated with dimethyldichlorosilane, hexamethyldisilazane, octylsilane, or the like is preferred here in order to impart moisture absorption resistance. When silica is added, the amount is preferably 1 to 50 mass% and more preferably 30 to 50 mass% based on 100 mass% of the solids content of the adhesive composition. By adjusting the amount to be equal to or greater than the lower limit, further heat resistance can be achieved. Furthermore, by adjusting the amount to be equal to or less than the upper limit, poor dispersion of silica and excessively high solution viscosity can be prevented, improving workability.

[0081] From the viewpoint of long-term heat resistance, a small magnesium hydroxide content is desirable, and the magnesium hydroxide content is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, even more preferably 3 parts by mass or less, still more preferably 0.5 parts by mass or less, and most preferably 0 part by mass, per 100 parts by mass of polyimide resin.

[0082] <Silane Coupling Agent> The adhesive composition of the present invention may contain a silane coupling agent, if necessary. 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, its amount is preferably 0.5 to 20% by mass based on 100% by mass of the solids content of the adhesive composition. By using a silane coupling agent within this range, solder heat resistance and adhesion can be improved.

[0083] <Long-term heat resistance> The adhesive composition of the present invention exhibits excellent low dielectric properties even after a long-term heat resistance test at 125°C for 1000 hours. For example, the adhesive composition of the present invention is heat-cured at 180°C for 3 hours, and the cured product is exposed to an air atmosphere at 125°C for 1000 hours. The dielectric loss tangent (tanδ) measured at a temperature of 23°C and a frequency of 40 GHz is preferably less than 0.005, more preferably 0.004 or less, and even more preferably 0.003 or less. Details of the measurement method are described in the "(relative dielectric constant (ε r In the present invention, since a polyimide resin is used, the adhesive composition is more likely to exhibit low dielectric properties after a long-term heat resistance test compared to an adhesive composition whose main component is an epoxy resin.

[0084] The adhesive composition of the present invention exhibits excellent adhesion even after a long-term heat resistance test at 125°C for 1000 hours. For example, the peel strength of a cured product obtained by heating and curing the adhesive composition of the present invention at 180°C for 90 minutes and then exposing it to an air atmosphere at 125°C for 1000 hours is preferably 0.5 N / mm or more, more preferably 1.0 N / mm or more, and even more preferably 1.2 N / mm or more, with an upper limit of 5 N / mm, although not particularly limited. For details of the measurement method, please refer to the "(High temperature and high humidity resistance)" section in the Examples section.

[0085] <Laminate> In the present invention, a laminate refers to a substrate to which the adhesive composition of the present invention is laminated, specifically a substrate to which the adhesive composition is laminated (a two-layer laminate of substrate / adhesive layer), or a substrate to which another substrate is 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 remaining 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 and drying them according to a conventional method, and then laminating another substrate on top of it.

[0086] The laminate of the present invention includes a laminate in which the adhesive composition of the present invention is laminated on a substrate such as a resin substrate, a metal substrate, paper, or an inorganic non-metallic substrate, as described below, and a laminate (adhesive sheet) in which the adhesive composition of the present invention is laminated on a release substrate. Examples of the laminate of the present invention include copper-clad laminates (CCLs), resin-coated metal foils, coverlay films, bonding sheets, etc.

[0087] <Substrate> The substrate in the present invention 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, paper, inorganic non-metallic substrates, and release substrates.

[0088] Examples of materials for the resin substrate include epoxy resin, polyester resin, polyamide resin, aramid resin, polyimide resin, polyamideimide resin, liquid crystal polymer, polyphenylene sulfide, polyphenylene ether, polyether sulfone, polyether ether ketone, polycarbonate, polyarylate, syndiotactic polystyrene, polyolefin resin, and fluorine-based resin. The form of the resin substrate is not particularly limited, but examples include a film made of the above resin and glass cloth (FR-4) impregnated with the above resin. The resin may contain a filler such as silica.

[0089] 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 0.1 μm or more, more preferably 0.2 μm or more, and even more preferably 0.3 μm or more.

[0090] Examples of papers include fine paper, kraft paper, roll paper, and glassine paper.

[0091] Examples of inorganic non-metallic substrates include glass and ceramic.

[0092] The release substrate is not particularly limited, but examples include those in which a coating layer of a filler such as clay, polyethylene, or polypropylene is provided on both sides of paper such as fine paper, kraft paper, roll paper, or glassine paper, and a silicone-based, fluorine-based, or alkyd-based release agent is further applied to each of the coating layers.Further 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 release agent.

[0093] In the present invention, the method for coating the adhesive composition onto 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, which is a printed wiring board constituent material, or the resin substrate. The thickness of the adhesive layer after drying can be appropriately 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 it 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. The drying conditions are not particularly limited, but a residual solvent ratio after drying of 1% by mass or less is preferred. By making it 1% by mass or less, foaming of the residual solvent during pressing of the printed wiring board is suppressed, making blisters less likely to occur.

[0094] <Copper-clad laminate (CCL)> In the present invention, a copper-clad laminate (CCL) is a laminate in which the metal foil is laminated on one or both sides of the resin substrate. The resin substrate and the metal foil may be laminated via the adhesive composition of the present invention, or the resin substrate and the metal foil may be laminated by thermocompression bonding without the adhesive composition of the present invention. Specific configurations of copper-clad laminates (CCLs) include a metal foil layer / adhesive layer / resin substrate layer / adhesive layer / metal foil layer, etc. The metal foil layer can be etched to form a circuit pattern, making it usable as a laminate material for printed wiring boards.

[0095] <Resin-Coated Metal Foil> In the present invention, a resin (adhesive)-coated metal foil is a metal foil having an adhesive layer, which is a cured product of the adhesive composition of the present invention, laminated on one side thereof. Specific configurations include a metal foil layer / adhesive layer or a metal foil layer / adhesive layer / release substrate. The metal foil is preferably a copper foil. Since the adhesive layer in the resin-coated metal foil can be laminated with the resin substrate, the resin-coated metal foil can be used as a material for producing the CCL.

[0096] <Coverlay Film> In the present invention, a coverlay film is a laminate of the resin substrate and the release substrate via the adhesive composition of the present invention. The resin substrate in the coverlay film can be any insulating film conventionally known as an insulating film for printed wiring boards. Resins constituting the resin substrate are preferably polyester resins, aramid resins, polyimide resins, polyamideimide resins, liquid crystal polymers, polyphenylene sulfide, polyethersulfone, polyetheretherketone, polycarbonate, polyarylate, syndiotactic polystyrene, polyolefin-based resins, etc., and more preferably films composed of polyimide resins, liquid crystal polymers, fluorine-based resins, etc. The coverlay film can be produced by applying the adhesive composition of the present invention to the resin substrate, drying it, and then laminating the release substrate thereon.

[0097] <Bonding Sheet> In the present invention, the bonding sheet refers to the adhesive composition of the present invention laminated onto the release substrate. Specific configurations include release substrate / adhesive layer / release substrate, or release substrate / adhesive layer / substrate (excluding the release substrate) / adhesive layer / release substrate. By laminating the release substrate, it functions as a protective layer for the substrate. Furthermore, by using a release substrate, the release substrate can be peeled from the bonding sheet and used to bond other substrates. As for the release substrate in the bonding sheet, from the viewpoint of visibility during the production of printed wiring boards, it is preferable that the release substrate on at least one side of the release substrate laminated on the outermost side of the bonding sheet is opaque.

[0098] <Printed wiring board> The adhesive composition of the present invention is preferably used for printed wiring boards. The printed wiring board of the present invention comprises, as a constituent element, a laminate having the metal substrate (metal foil) and the resin base material that form a conductor circuit. The printed wiring board of the present invention collectively refers to so-called rigid substrates, flexible printed wiring boards (FPCs), flat cables, circuit boards for tape automated bonding (TAB), etc.

[0099] The printed wiring board of the present invention can have any laminate structure that can be used as a printed wiring board. The printed wiring board of the present invention preferably includes, as a component, a laminate in which the adhesive composition of the present invention is laminated on a substrate that is a resin substrate, a metal substrate, paper, or an inorganic non-metallic substrate. If necessary, two or more of the above-described printed wiring boards can be laminated. If necessary, two or more layers other than the protective layer of the printed wiring board can be laminated with bonding sheets, and a protective layer such as a coverlay film or solder resist can be provided thereon. For example, using a laminate such as the CCL, a printed wiring board can be formed that has four layers, such as a resin substrate layer / adhesive layer / metal foil layer / coverlay film layer or a resin substrate layer / metal foil layer / adhesive layer / coverlay film layer. Alternatively, a printed wiring board can be formed that has five layers, such as a resin substrate layer / adhesive layer / metal foil layer / adhesive layer / coverlay film layer.

[0100] The formation of a circuit on a metal substrate (metal foil layer) can be performed by a conventionally known method. An additive method or a subtractive method may be used. A subtractive method is preferred.

[0101] The printed wiring board of the present invention can be manufactured using any conventionally known process, except for using the materials for each layer described above. For example, a circuit pattern is formed on a three-layer CCL using an adhesive or a two-layer CCL without an adhesive, and then laminated to another CCL using a bonding sheet or prepreg and thermally cured. After drilling, through-hole plating, copper foil patterning, etc., a protective layer such as a coverlay film or solder resist is formed on the outermost layer, and then a surface treatment is performed to obtain a multilayer printed wiring board.

[0102] The adhesive composition of the present invention can be suitably used in the production of printed wiring boards, and specifically, can be suitably used for each adhesive layer of a printed wiring board. In particular, when the adhesive composition of the present invention is used as an adhesive, it can bond not only conventional substrates constituting printed wiring boards, such as polyimide film, polyester film, and FR-4, but also low-adhesion substrates such as liquid crystal polymers and fluororesin-impregnated glass cloth to low-roughness copper foil. Furthermore, because it has high adhesion to low-polarity resin substrates such as liquid crystal polymers, polyphenylene sulfide, syndiotactic polystyrene, and polyolefin resins, it can achieve solder reflow resistance. The adhesive layer itself also has excellent low dielectric properties, allowing for printed wiring boards with excellent high-frequency characteristics.

[0103] This application claims the benefit of priority based on Japanese Patent Application No. 2024-052227, filed on March 27, 2024. The entire contents of the specification of Japanese Patent Application No. 2024-052227, filed on March 27, 2024, are incorporated herein by reference.

[0104] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples, and can of course be practiced with appropriate modifications within the scope of the above and below-described aims, all of which are included within the technical scope of the present invention. In the following, unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass."

[0105] <Evaluation of Physical Properties> (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.

[0106] (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).

[0107] <Evaluation of Adhesive Composition> (Dielectric Constant (ε r ) and dielectric loss tangent (tan δ). The adhesive composition was applied to a 100 μm thick Teflon (registered trademark) sheet so that the thickness after drying would be 25 μm, and then dried at 100°C for 2 minutes. Next, another Teflon sheet was placed over the applied adhesive composition surface, and the adhesive composition was cured by heat treatment at 180°C for 3 hours, after which the Teflon sheets on both sides were peeled off to obtain an adhesive resin sheet. The obtained sheet was cut into 10 cm x 10 cm strips to obtain a sample for initial characteristic evaluation. Furthermore, after curing by heat treatment in the same manner as above, only one Teflon sheet was peeled off to obtain an adhesive resin sheet with a Teflon sheet. The obtained sheet was left to stand in an oven at 125°C under an air atmosphere for 1,000 hours, and then cut into 10 cm x 10 cm strips to obtain a sample for long-term heat resistance evaluation. r The dielectric constant (R) and dielectric loss tangent (tan δ) were measured using a network analyzer (manufactured by Anritsu Corporation) by the cavity resonance method at a temperature of 23°C and a frequency of 40 GHz. The measurement conditions for the sample for initial characteristic evaluation and the sample for long-term heat resistance evaluation were the same. <Evaluation criteria for relative dielectric constant> ○: Less than 2.6 ×: 2.6 or more <Evaluation criteria for dielectric loss tangent> ○: Less than 0.005 ×: 0.005 or more

[0108] (Peel Strength (Adhesion)) The adhesive composition was applied to a 100 μm thick surface-treated PTFE film (Yodoflon (registered trademark), manufactured by Yodogawa Hutech Co., Ltd.) so that the thickness after drying would be 25 μm, and then dried at 100°C for 2 minutes. The adhesive film (B-stage product) thus obtained was bonded to an 18 μm thick electrolytic copper foil (T9DA-SV-18, manufactured by Fukuda Metal Foil Powder Co., Ltd.). The bonding was performed with the matte side of the copper foil in contact with the adhesive layer, by raising the temperature from 35°C to 180°C at a rate of 4°C per minute under a pressure of 2 MPa, and after reaching 180°C, by heat treatment for 90 minutes to cure, to obtain a sample for peel strength evaluation. Peel strength was measured at 25°C, with film pulling, a tensile speed of 50 mm / min, and 90° peeling. <Evaluation Criteria> ○: 1.0 N / mm or more ×: less than 1.0 N / mm

[0109] (Soldering heat resistance) Evaluation samples were prepared in the same manner as for measuring peel strength, and sample pieces cut to 2.0 cm x 2.0 cm were immersed in a solder bath, and the upper limit temperature at which no change in appearance such as swelling occurred was recorded. <Evaluation criteria> ○: No change in appearance at 290°C or higher ×: Change in appearance at temperatures below 290°C

[0110] (Long-term heat resistance) Evaluation samples were prepared in the same manner as for measuring peel strength, and the samples were placed in an oven at 125°C for 1000 hours, after which the appearance of the samples was observed. The peel strength after the long-term heat resistance test was measured in the same manner as for measuring peel strength. <Evaluation criteria> ○: No abnormality in appearance, peel strength of 1.0 N / mm or more △: Slight discoloration, peel strength less than 1.0 N / mm ×: Substrate peeling and discoloration

[0111] <Production of Adhesive Composition> Hereinafter, examples of the production of adhesive compositions will be described as examples of the present invention and comparative examples.

[0112] The polyimide resin was produced as follows. 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-neck 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 the mixture was subjected to an imidization reaction 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.

[0113] The following epoxy resin (C) was used: 4,4'-methylenebis(N,N-diglycidylaniline) (manufactured by Mitsubishi Chemical Corporation, "jER604", epoxy value 8547 equivalents / 10 6 g)

[0114] The following antioxidants were used as the antioxidant (A): a1: a phenol-based antioxidant (Sumitomo Chemical Co., Ltd.'s "Sumilizer (registered trademark) GA-80," 2,4,8,10-tetraoxaspiro[5.5]undecane-3,9-diyl)bis(2-methylpropane-2,1-diyl)bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propanoate]), and a2: a sulfur-based antioxidant (Sumitomo Chemical Co., Ltd.'s "Sumilizer (registered trademark) TP-D," pentaerythritol tetrakis-(3-laurylthiopropionate).

[0115] The following heavy metal deactivators (B) were used: b1: Hydrazine-based heavy metal deactivator (ADEKA CORPORATION's "ADEKA STAB (registered trademark) CDA-10", N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine) b2: Phosphite-based heavy metal deactivator (Clariant Corporation's "HOSTANOX (registered trademark) OSP1", reaction product of 2,2'-di-tert-butyl-5,5'-dimethyl-4,4'-sulfanediyldiphenol and phosphorus trichloride)

[0116] Example 1 100 parts of polyimide resin, 2.4 parts of epoxy resin, 0.09 parts of antioxidant a1, 0.21 parts of antioxidant a2, and 0.10 parts of heavy metal deactivator b1 were blended and dissolved in toluene to a solids concentration of 40%, to obtain an adhesive composition (S1). The obtained adhesive composition (S1) was subjected to various adhesive composition evaluations. The results are shown in Table 1.

[0117] Examples 2 to 4, Comparative Examples 1 to 5 Adhesive compositions (S2) to (S9) 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.

[0118]

[0119]

[0120] As shown in Examples 1 to 4, adhesive compositions containing predetermined amounts of antioxidant (A) and heavy metal deactivator (B) exhibited good appearance and excellent adhesion even after a long-term heat resistance test at 125°C for 1,000 hours. They also exhibited excellent low dielectric properties after the long-term heat resistance test. Furthermore, as shown in Examples 1 to 4, adhesive compositions containing predetermined amounts of antioxidant (A) and heavy metal deactivator (B) also exhibited excellent solder heat resistance, adhesion, and initial low dielectric properties.

[0121] In particular, as shown by a comparison of Examples 1 to 4, the appearance, adhesiveness, and dielectric properties after a long-term heat resistance test can be varied by changing the content ratio and type of heavy metal deactivator (B). Furthermore, a comparison of Example 2 and Example 4 shows that using a hydrazine-based heavy metal deactivator as the heavy metal deactivator (B) is effective in obtaining an adhesive composition that has excellent appearance, adhesiveness, and dielectric properties after a long-term heat resistance test.

[0122] The adhesive composition of Comparative Example 1 did not contain the heavy metal deactivator (B), and therefore exhibited poor appearance and adhesion after the long-term heat resistance test. Similarly, the adhesive composition of Comparative Example 2 did not contain the antioxidant (A), and therefore exhibited poor appearance, adhesion, and dielectric properties after the long-term heat resistance test. The adhesive compositions of Comparative Examples 3 and 4 contained large amounts of the antioxidant (A) or the heavy metal deactivator (B), and therefore exhibited poor dielectric properties after the long-term heat resistance test. Furthermore, the adhesive compositions of Comparative Examples 3 and 4 did not exhibit sufficient effects in terms of solder heat resistance and initial dielectric properties. The adhesive composition of Comparative Example 5 did not contain the epoxy resin (C), and therefore curing was insufficient, and therefore the appearance and adhesion after the long-term heat resistance test were poor. Furthermore, the adhesive composition of Comparative Example 5 did not exhibit sufficient effects in terms of solder heat resistance and adhesion.

[0123] The adhesive composition of the present invention exhibits a good appearance, excellent adhesion, and excellent low dielectric properties even after a long-term heat resistance test at 125°C for 1,000 hours. The adhesive composition of the present invention also has excellent solder heat resistance, adhesion, and initial low dielectric properties. Therefore, the adhesive composition of the present invention is useful as an adhesive composition for printed wiring boards in the high-frequency range, as well as an adhesive sheet, laminate, and printed wiring board containing the same.

Claims

1. An adhesive composition comprising a polyimide resin, an antioxidant (A), a heavy metal deactivator (B), and an epoxy resin (C), wherein the content of the antioxidant (A) is 1.0 part by mass or less and the content of the heavy metal deactivator (B) is 1.0 part by mass or less per 100 parts by mass of the polyimide resin.

2. The adhesive composition according to claim 1, wherein the heavy metal deactivator (B) comprises at least one of a hydrazine-based heavy metal deactivator and a phosphite-based heavy metal deactivator.

3. The adhesive composition according to claim 1, wherein the heavy metal deactivator (B) has a chemical structure represented by formula (II) in the molecule. [In formula (II), * represents a bond, and R 4 ~R 6 are each independently a hydrogen atom or C 1-10 represents an alkyl group.] 4. The adhesive composition according to claim 1, wherein the content of the heavy metal deactivator (B) is 1 to 200 parts by mass per 100 parts by mass of the antioxidant (A).

5. The adhesive composition according to claim 1, wherein the content of the heavy metal deactivator (B) is 0.01 parts by mass or more per 100 parts by mass of the polyimide resin.

6. The adhesive composition according to claim 1, wherein the antioxidant (A) is at least one selected from the group consisting of phenol-based antioxidants, sulfur-based antioxidants, amine-based antioxidants, and phosphorus-based antioxidants.

7. The adhesive composition according to claim 1, wherein the antioxidant (A) has a chemical structure represented by formula (I) in the molecule. [In formula (I), * represents a bond, R 1 ~R 3 are each independently a hydrogen atom or C 1-10 represents an alkyl group.] 8. The adhesive composition according to claim 1, wherein the epoxy resin (C) is a multifunctional epoxy resin.

9. The epoxy value of the epoxy resin (C) is 5,000 to 12,000 equivalents / 10 6 2. The adhesive composition according to claim 1, wherein the viscosity is 100 MPa.

10. The adhesive composition according to claim 1, wherein the epoxy resin (C) is at least one selected from the group consisting of glycidylamine-type epoxy resins, glycidyl group-containing isocyanuric acid resins, and alicyclic epoxy resins.

11. The adhesive composition according to any one of claims 1 to 10, which is used for printed wiring boards.

12. An adhesive sheet comprising a release substrate and the adhesive composition according to any one of claims 1 to 10 laminated thereon.

13. A laminate in which the adhesive composition according to any one of claims 1 to 10 is laminated on a substrate which is a resin substrate, a metal substrate, paper, or an inorganic non-metallic substrate.

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

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