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

Abstract

The present invention provides: an adhesive composition that has excellent solder heat resistance and adhesive strength, and also has excellent dielectric characteristics with low relative permittivity and low loss tangent; and an adhesive sheet, a laminate, and a printed wiring board each containing the adhesive composition.　The adhesive composition according to the present invention comprises a polyimide resin and an epoxy resin (E), and is characterized in that: the epoxy resin (E) includes an epoxy resin (A) represented by formula (I); and the content of a glycidyl ether-type epoxy resin (B) contained as the epoxy resin (E) is 5 parts by mass or less with respect to 100 parts by mass of the polyimide resin. In formula (I), R1 to R5 each independently represent a hydrogen atom or a C1-10 alkyl group.

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] Furthermore, the reaction between the general epoxy resin and carboxyl group-containing resin described in Patent Document 1 is slow, and when an adhesive sheet is produced by applying the adhesive to a substrate and then evaporating the solvent by low-temperature heating, the curing reaction hardly progresses. As a result, when the adhesive sheet is used, the resin flow (i.e., the fluidity of the resin during lamination) becomes extremely large, hindering circuit continuity and creating problems with precise control.

[0006] The present invention has been made in view of the above-mentioned problems in the prior art. That is, a first 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.

[0007] In addition to the first object described above, a second object of the present invention is to provide an adhesive composition in which the degree of curing can be controlled, as well as an adhesive sheet, a laminate, and a printed wiring board containing the same.

[0008] The present invention is sufficient if it can achieve either the first object or the second object, and it is even more preferable if it can achieve both the first object and the second object.

[0009] 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.

[0010] [1] An adhesive composition comprising a polyimide resin and an epoxy resin (E), wherein the epoxy resin (E) comprises an epoxy resin (A) represented by formula (I), and the content of a glycidyl ether epoxy resin (B) contained as the epoxy resin (E) is 5 parts by mass or less per 100 parts by mass of the polyimide resin. [In formula (I), R 1 ~R 5 are each independently a hydrogen atom or C 1-10[2] The adhesive composition according to [1], wherein the content of the epoxy resin (A) is 0.01 parts by mass or more and 20 parts by mass or less relative to 100 parts by mass of the polyimide resin. [3] The acid value of the polyimide resin is 10 equivalents / 10 6 g or more 1000 equivalent / 10 6 g or less. [4] The adhesive composition according to any one of [1] to [3], wherein the ratio represented by (total epoxy value of the epoxy resin (E) / total acid value of the polyimide resin) is 0.5 or more and 10.0 or less. [5] The adhesive composition according to any one of [1] to [4], wherein the content of the epoxy resin (A) is 70 mass% or more based on 100 mass% of the epoxy resin (E). [6] The adhesive composition according to any one of [1] to [5], wherein the content of the epoxy resin (B) is 25 mass% or less based on 100 mass% of the epoxy resin (E). [7] In the formula (I), R 1 and / or R 5 is C 1-10 [8] The adhesive composition according to any one of [1] to [7], wherein the epoxy resin (A) and the glycidyl ether type epoxy resin (B) account for 50 mass% or more of the total amount of the epoxy resin (E) relative to 100 mass% of the epoxy resin (E). [9] The adhesive composition according to any one of [1] to [8], wherein the glycidyl ether type epoxy resin (B) is an epoxy resin having a chemical structure represented by formula (II) or formula (III) in the molecule. [In formula (II), R 6 ~R 9 are each independently a hydrogen atom or C 1-10 represents an alkyl group. * represents a bond.] [In formula (III), R 26 ~R 29 are each independently a hydrogen atom or C 1-10represents an alkyl group. * represents a bond.]

[10] The adhesive composition according to any one of [1] to [9], which does not contain the glycidyl ether type epoxy resin (B).

[11] The adhesive composition according to any one of [1] to [9], which contains the glycidyl ether type epoxy resin (B), and the content of the glycidyl ether type epoxy resin (B) is 0.5 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the polyimide resin.

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

[11] , which has a chlorine concentration of 0.01 to 300 ppm in the solid content of the adhesive composition.

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

[12] , which is for use in printed wiring boards.

[14] An adhesive sheet obtained by laminating a substrate which is a resin substrate, a metal substrate, or a paper substrate and a release substrate via the adhesive composition according to any one of [1] to

[12] .

[15] The adhesive sheet according to

[14] , wherein the rate of change of dielectric loss tangent calculated based on the following formula is 8 to 70%. Ｂ -T Ｃ ) / T Ｂ ×100 (in the above formula, T Ｂ : Dielectric loss tangent of a B-stage product obtained by applying the adhesive composition to a 100 μm thick Teflon (registered trademark) sheet so that the thickness after drying would be 25 μm and drying at 130° C. for 3 minutes Ｃ (The dielectric loss tangent of the C-stage product obtained by heat-treating the B-stage product at 180°C for 3 hours for curing is 100%)

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

[12] is laminated on a substrate that is a resin substrate, a metal substrate, or a paper substrate.

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

[16] as a component.

[0011] The adhesive composition of the present invention has excellent solder heat resistance, adhesive strength, and dielectric properties. Furthermore, the degree of curing of the adhesive composition of the present invention can be controlled. Therefore, the adhesive composition is suitable for use in adhesives for FPCs, adhesive sheets, laminates, and printed wiring boards in the high-frequency range.

[0012] 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.

[0013] <Adhesive composition> The adhesive composition of the present invention is an adhesive composition containing a polyimide resin and an epoxy resin (E), wherein the epoxy resin (E) contains an epoxy resin (A) represented by formula (I), and the content of the glycidyl ether epoxy resin (B) contained as the epoxy resin (E) is 5 parts by mass or less relative to 100 parts by mass of the polyimide resin. [In formula (I), R 1 ~R 5 are each independently a hydrogen atom or C 1-10 represents an alkyl group.]

[0014] In the present invention, by blending an epoxy resin (A) represented by formula (I) with a polyimide resin and setting the content of a glycidyl ether type epoxy resin (B) to a predetermined amount or less, when the carboxy groups in the polyimide resin react with the epoxy resin (E), a high-density crosslinked structure is formed, and the movement of the by-produced hydroxyl groups is suppressed in the crosslinked structure, thereby providing an adhesive composition that has excellent solder heat resistance, adhesive strength, and also excellent dielectric properties.

[0015] <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.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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, 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, and even more preferably 90% by mass or less. A content within the above range is preferable because it results in good adhesion and heat resistance.

[0032] <Epoxy Resin (E)> The adhesive composition of the present invention contains an epoxy resin (A) represented by formula (I) as the epoxy resin (E). Because the epoxy resin (A) has two epoxy groups, it is advantageous for forming a high-density crosslinked structure. Epoxy resins containing three or more epoxy groups are not preferred because some of the epoxy groups may not react and remain, resulting in a poor dielectric loss tangent. Furthermore, because the number of carbon atoms between the nitrogen atom and the epoxy group indirectly bonded to it is small, the epoxy resin (A) has a large steric hindrance and a structure with poor mobility. Such a structure with large steric hindrance can suppress atomic movement, making it ideal for obtaining an adhesive composition with a low dielectric loss tangent.

[0033] Furthermore, as the atomic movement of epoxy resin (A) is suppressed after curing, the dielectric dissipation factor of the semi-cured product (B-stage product) decreases as curing progresses. Additionally, epoxy resin (A) reacts more quickly with polyimide resins than general epoxy resins (except epoxy resin (A)). Therefore, the curing reaction gradually progresses when the adhesive composition is applied to a substrate and the solvent is evaporated by low-temperature heating. As a result, the dielectric dissipation factor of the adhesive composition of the present invention significantly decreases from the B-stage product to the C-stage product. By utilizing this characteristic, the decrease in the dielectric dissipation factor of the adhesive composition after application can be monitored, and the degree of curing (degree of reaction) of the adhesive composition can be determined from the obtained dielectric dissipation factor. The degree of curing of the adhesive composition is related to resin flow, solder heat resistance, and other properties that are closely related to the crosslinking state. Therefore, understanding the degree of curing of the adhesive composition leads to precise control of these properties. [In formula (I), R 1 ~R 5 are each independently a hydrogen atom or C 1-10 represents an alkyl group.]

[0034] C in formula (I) 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 1-6alkyl group, more preferably C 1-3 It is an alkyl group, and even more preferably a methyl group or an ethyl group.

[0035] In formula (I), R 1 ~R 5 Of these, 0 to 3 are C 1-10 The alkyl group 1-10 Preferably, the group other than the alkyl group is a hydrogen atom, and R 1 ~R 5 Of these, 0 to 1 are C 1-10 The alkyl group 1-10 It is more preferable that the group other than the alkyl group is a hydrogen atom.

[0036] In formula (I), at least R 1 and / or R 5 is C 1-10 It is preferably an alkyl group. 1 and / or R 5 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.

[0037] Examples of the epoxy resin (A) include N,N-diglycidylaniline, N,N-(diglycidyl)-o-toluidine, N,N-(diglycidyl)-m-toluidine, and N,N-(diglycidyl)-p-toluidine, and preferred are N,N-(diglycidyl)-o-toluidine, N,N-(diglycidyl)-m-toluidine, and N,N-(diglycidyl)-p-toluidine.

[0038] The epoxy value of the epoxy resin (A) 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 6g. When the epoxy value is equal to or greater than the above value, 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 above value, 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).

[0039] The content of epoxy resin (A) 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 polyimide resin. By setting it to the lower limit or more, a sufficient curing effect can be obtained, and excellent adhesion and solder heat resistance can be exhibited. Furthermore, 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 can be improved. In other words, by setting it within the above range, an adhesive composition having excellent adhesion, solder heat resistance, and low dielectric properties can be obtained.

[0040] The content of the epoxy resin (A) is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more, based on 100% by mass of the epoxy resin (E) contained in the adhesive composition of the present invention. By making it equal to or greater than the lower limit, the dielectric properties become extremely good. The upper limit is not particularly limited, but it may be 100% by mass, and 95% by mass is also acceptable.

[0041] The adhesive composition of the present invention may contain a small amount of a glycidyl ether-type epoxy resin (B) as the epoxy resin (E). The glycidyl ether-type epoxy resin (B) specifically refers to an epoxy resin containing a glycidyl ether group in the molecule, in which a glycidyl group and an ether group are bonded. The glycidyl ether group has little steric hindrance and a structure with high local mobility. Furthermore, while the epoxy resin (A) has two glycidyl groups bonded to one nitrogen atom, the glycidyl ether group has only one glycidyl group bonded to one oxygen atom, resulting in fewer reaction sites. Due to these factors, if the content of the epoxy resin (B) exceeds a predetermined amount, it becomes difficult to obtain an adhesive composition with a low dielectric loss tangent. Therefore, even if the adhesive composition of the present invention contains an epoxy resin (B), it is desirable that the amount be small or that the epoxy resin (B) be absent, even if it does contain one.

[0042] The epoxy resin (B) is preferably an epoxy resin (B) having a chemical structure represented by formula (II) or formula (III) in the molecule. [In formula (II), R 6 ~R 9 are each independently a hydrogen atom or C 1-10 represents an alkyl group. * represents a bond.] [In formula (III), R 26 ~R 29 are each independently a hydrogen atom or C 1-10 represents an alkyl group. * represents a bond.]

[0043] As the epoxy resin (B), an epoxy resin represented by formula (II-A), formula (II-B) or formula (III-A) is preferred, and from the viewpoint of low dielectric properties and solder heat resistance, an epoxy resin represented by formula (II-A) or formula (III-A) is more preferred. [In formula (II-A), R 6 ~R 9 is the same as above.] [In formula (II-B), R 6 ~R 9 is the same as above. 10 ~R 15 are each independently a hydrogen atom or C 1-10 represents an alkyl group.] [In formula (III-A), R 26 ~R 29 is the same as above.]

[0044] C in formula (II), formula (III), formula (II-A), formula (II-B) and formula (III-A) 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.

[0045] Examples of such epoxy resins (B) include the following:

[0046] The epoxy value of the epoxy resin (B) is preferably 3,000 to 13,000 equivalents / 10 from the viewpoint of heat resistance and adhesion to resin substrates and metal substrates. 6 g, more preferably 4,000 to 12,000 equivalents / 10 6 g, more preferably 5,000 to 11,000 equivalents / 10 6 When the viscosity is equal to or greater than the above value, the adhesive strength is improved and the crosslink density is increased, thereby improving the heat resistance. When the viscosity is equal to or less than the above value, the adhesiveness and low dielectric properties are improved.

[0047] The content of the epoxy resin (B) is 5 parts by mass or less, preferably 1 part by mass or less, and more preferably 0 parts by mass, per 100 parts by mass of the polyimide resin. By setting the content below the upper limit, the number of hydroxyl groups derived from glycidyl ether groups can be reduced, resulting in good low dielectric properties. That is, by using the epoxy resin (A) and an epoxy resin (B) of which the content is below the upper limit, an adhesive composition having excellent low dielectric properties in addition to adhesion and solder heat resistance can be obtained. When the adhesive resin composition of the present invention contains the epoxy resin (B), the content of the epoxy resin (B) is preferably 0.5 parts by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, per 100 parts by mass of the polyimide resin.

[0048] The content of the epoxy resin (B) is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less, based on 100% by mass of the epoxy resin (E) contained in the adhesive composition of the present invention. By setting it to the upper limit or less, the dielectric properties become extremely good. The lower limit is not particularly limited, but it may be 0% by mass, and 5% by mass is also acceptable.

[0049] The adhesive composition of the present invention may contain, as the epoxy resin (E), an epoxy resin other than the above-mentioned epoxy resin (A) and the above-mentioned epoxy resin (B). The epoxy resin other than the above-mentioned epoxy resin (A) and the above-mentioned epoxy resin (B) 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 epoxy groups in the molecule. Specific examples include, but are not 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, epoxy-modified polybutadiene, and glycidyl group-containing isocyanuric acid.

[0050] In the adhesive composition of the present invention, the total amount of the epoxy resin (A) and the epoxy resin (B) is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 90% by mass or more, and even more preferably 95% by mass or more, based on 100% by mass of the epoxy resin (E). By keeping the total amount of the epoxy resin (A) and the epoxy resin (B) within the above range, it is possible to improve the solder heat resistance, adhesive strength, and dielectric properties.

[0051] The total amount of epoxy resin (E) contained in the adhesive composition of the present invention is preferably 0.01 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 2 parts by mass or more, relative to 100 parts by mass of polyimide resin. By adjusting it to be equal to or greater than the lower limit, a sufficient curing effect can be obtained, and excellent adhesion and solder heat resistance can be exhibited. Furthermore, it is preferably 25 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 7 parts by mass or less. By adjusting it to be equal to or less than the upper limit, the pot life and low dielectric properties can be improved. In other words, by adjusting it within the above range, an adhesive composition having excellent adhesion, solder heat resistance, and low dielectric properties can be obtained.

[0052] In the adhesive composition of the present invention, it is preferable to adjust the balance between the acid value of the polyimide resin and the epoxy value of the epoxy resin (E) from the viewpoint of improving heat resistance. Specifically, the ratio (hereinafter sometimes referred to as "E / A") expressed as (total epoxy values ​​of epoxy resin (E) / total acid values ​​of polyimide resin) is preferably 0.5 or more and 10.0 or less, more preferably 1.0 or more and 5.0 or less, even more preferably 1.5 or more and 4.0 or less, even more preferably 1.8 or more and 3.5 or less, and particularly preferably 1.9 or more and 3.3 or less. By setting the ratio at or above the lower limit, the crosslink density can be increased, resulting in good solder heat resistance. By setting the ratio at or below the upper limit, the polar groups in the adhesive can be reduced, resulting in good dielectric properties. In other words, by setting the epoxy group value / acid value within the above range, an adhesive composition with a good balance between solder heat resistance and low dielectric properties can be obtained.

[0053] When epoxy resin (E) is blended, the adhesive composition may contain by-products generated during the production of epoxy resin (E). Examples of such by-products include chlorine-containing substances with hydrolyzable chlorine groups that could not be ring-closed with NaOH. The present inventors conducted extensive research focusing on the chlorine content in the adhesive composition and found that, in the adhesive composition of the present invention containing a polyimide resin, reducing the chlorine content in the adhesive composition leads to an improvement in dielectric loss tangent, in particular. It is generally believed that reducing the chlorine concentration in an adhesive composition leads to the suppression of ionic migration, which in turn contributes to improved insulation reliability. However, it was not widely known that the chlorine concentration in an adhesive composition affects dielectric properties such as the dielectric constant and dielectric loss tangent, which are not related to ionic migration. In the frequency band of several tens of GHz, reducing the number of highly polar functional groups is effective in lowering the dielectric constant and dielectric loss tangent. However, when considering the chlorine concentration, even if the chlorine concentration is low, an adhesive composition with a high concentration of highly polar functional groups may be able to improve insulation reliability by suppressing ion migration, but may not be able to improve dielectric properties. In other words, focusing on the chlorine concentration is extremely effective from the perspective of improving dielectric properties. The chlorine concentration contained in the adhesive composition of the present invention is, for example, preferably 0.01 to 300 ppm, more preferably 0.1 to 140 ppm, and even more preferably 1 to 100 ppm, based on the solid content of the adhesive composition. By keeping the chlorine concentration within this range, the influence of chlorine-containing substances can be reduced, resulting in extremely good dielectric properties (particularly dielectric loss tangent).

[0054] Methods for reducing the chlorine concentration in adhesive compositions include, for example, using epoxy resins (E) synthesized by oxidation without using chlorine-containing substances, or using distilled and purified epoxy resins (E). Using epoxy resins (E) synthesized by oxidation is particularly advantageous because it allows for the production of adhesive compositions with a chlorine concentration of approximately 0 ppm in the solids. On the other hand, using epoxy resins (E) synthesized by oxidation can result in the inclusion of low-molecular-weight allyl group-containing substances as impurities, which may adversely affect the dielectric properties. Therefore, from the perspective of improving dielectric properties, an adhesive composition with a chlorine concentration of 0 ppm is ideal. However, in reality, epoxy resins (E) that can achieve this contain low-molecular-weight allyl group-containing substances. Therefore, adhesive compositions that do not contain low-molecular-weight allyl group-containing substances are preferred, even if the chlorine concentration exceeds 0 ppm. Furthermore, distillation methods for epoxy resins (E) include rotary evaporation, vacuum fractional distillation, short-path distillation, packed column distillation, spinning band distillation, falling-film distillation, wiper-type thin-film distillation, and vacuum distillation including steam distillation.

[0055] <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 (E) reacts with the carbodiimide bond, thereby improving heat resistance and adhesiveness.

[0056] 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.

[0057] <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.

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] <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.

[0063] 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.

[0064] 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.

[0065] <Organic Solvent> The adhesive composition of the present invention may further contain an organic solvent. The organic solvent used in the present invention is not particularly limited as long as it dissolves the polyimide resin and the epoxy resin (E). 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.

[0066] 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.

[0067] 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.

[0068] <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. 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 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 and epoxy resin (E) combined. By keeping the amount within this range, flame retardancy can be achieved while maintaining adhesion, solder heat resistance, and electrical properties.

[0069] <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 and epoxy resin (E) 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.

[0070] <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.

[0071] 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 1 to 100 parts by mass per 100 parts by mass of the polyimide resin and epoxy resin (E) combined. 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.

[0072] <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.

[0073] When the adhesive composition contains an antioxidant, the content thereof is preferably 0.01 to 5 parts by mass, and more preferably 0.1 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 adhesion and dielectric properties can be suppressed even when the adhesive composition is used in a high-temperature environment where it is exposed to air.

[0074] <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 polyimide resin and epoxy resin (E) combined. By using a silane coupling agent within this range, solder heat resistance and adhesion can be improved.

[0075] <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.

[0076] <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.

[0077] Examples of the resin substrate include polyester resin, polyamide resin, polyimide resin, polyamideimide resin, liquid crystal polymer, polyphenylene sulfide, syndiotactic polystyrene, polyolefin resin, and fluorine-based resin. A film-like resin (hereinafter also referred to as a substrate film layer) is preferred.

[0078] 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.

[0079] Examples of the paper include fine paper, kraft paper, roll paper, glassine paper, etc. Examples of the composite material include glass epoxy, etc.

[0080] In view of adhesive strength with the adhesive composition and durability, the substrate is preferably a polyester resin, a polyamide resin, a polyimide resin, a polyamideimide resin, a liquid crystal polymer, polyphenylene sulfide, syndiotactic polystyrene, a polyolefin resin, a fluorine-based resin, an SUS steel plate, a copper foil, an aluminum foil, or a glass epoxy.

[0081] <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.

[0082] 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.

[0083] The adhesive composition of the present invention preferably has a rate of change in dielectric loss tangent calculated, for example, by the following formula: 8 to 70%, more preferably 20 to 65%, and even more preferably 30 to 60%. Because the adhesive composition of the present invention contains the epoxy resin (A), the dielectric loss tangent can be significantly reduced from the B-stage product to the C-stage product. Rate of change in dielectric loss tangent (%) = (T Ｂ -T Ｃ ) / T Ｂ ×100 (in the above formula, T Ｂ : Dielectric loss tangent of a B-stage product obtained by applying the adhesive composition to a 100 μm thick Teflon (registered trademark) sheet so that the thickness after drying would be 25 μm and drying at 130° C. for 3 minutes Ｃ: Dielectric loss tangent of a C-stage product obtained by heat-treating the B-stage product at 180°C for 3 hours to harden it.

[0084] <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.

[0085] 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.

[0086] <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.

[0087] 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.

[0088] Furthermore, if necessary, two or more of the above printed wiring boards may be stacked.

[0089] 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.

[0090] 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 polyester resins, polyamide resins, polyimide resins, polyamideimide resins, liquid crystal polymers, polyphenylene sulfide, syndiotactic polystyrene, polyolefin 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 resins.

[0091] <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, polyether sulfone, polyether ether ketone, aramid, polycarbonate, polyarylate, polyamide imide, liquid crystal polymer, syndiotactic polystyrene, and polyolefin resin can be used. Polyimide film or liquid crystal polymer film is more preferred.

[0092] 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.

[0093] 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.

[0094] 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").

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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 (E), it is preferably produced by transfer-coating an adhesive that has been applied in advance to a release substrate. Furthermore, if necessary, a crosslinking reaction can be carried out in the applied adhesive. In a preferred embodiment, the adhesive layer is semi-cured.

[0101] 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.

[0102] 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.

[0103] This application claims the benefit of priority based on Japanese Patent Application No. 2023-187159, filed on October 31, 2023. The entire contents of the specification of Japanese Patent Application No. 2023-187159, filed on October 31, 2023, are incorporated herein by reference.

[0104] 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.

[0105] <Method for Evaluating Physical Properties> (Acid Value Measurement) The acid value (equivalent / 10 6 In g), the polyimide resin was dissolved in toluene and titrated with a methanol solution of sodium methoxide using phenolphthalein as an 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] (Measurement of chlorine concentration in epoxy resin) 1 g of the epoxy resin used in the examples was dissolved in 25 ml of ethylene glycol monobutyl ether. 25 ml of a 1 N propylene glycol solution of potassium hydroxide was added to the solution, and the mixture was boiled for 20 minutes. The total amount of chlorine in the epoxy resin was then titrated with an aqueous silver nitrate solution to determine the chlorine concentration in the epoxy resin.

[0108] (Measurement of the Amount of Allyl Group-Containing Substances in Epoxy Resins) The amount of allyl group-containing substances in the epoxy resins used in the examples was measured using gas chromatography (Shimadzu Corporation, GC-2010Plus).

[0109] The following describes examples of producing adhesive compositions according to the present invention and comparative examples.

[0110] 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.

[0111] The following epoxy resins were used as the epoxy resin (A): Epoxy resin a1: EP-3980S (manufactured by ADEKA Corporation, N,N-(diglycidyl)-O-toluidine, epoxy value 8696 equivalents / 10 6 g, chlorine 700 ppm, allyl group-containing substances 0%)

[0112] The following epoxy resins were used as the epoxy resin (B): Epoxy resin b1: EP-3900S (manufactured by ADEKA Corporation, epoxy value 10,000 equivalents / 10 6 g, chlorine 1200 ppm, allyl group-containing substances 0%) Epoxy resin b2: YL980 (manufactured by Mitsubishi Chemical Corporation, epoxy value 5376 equivalents / 10 6 g, chlorine 300 ppm, allyl group-containing substances 0%)

[0113] The other components used were as follows: c1: Silica ("GT3SDC" manufactured by Denka Co., Ltd.) c2: Phosphine oxide flame retardant ("PQ-60" manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) c3: Phosphorus-based antioxidant ("HOSTANOX (registered trademark) P-EPQ" manufactured by Clariant)

[0114] Example 1: 100 parts of the polyimide resin and 4 parts of the epoxy resin (A) 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.

[0115] Examples 2 to 6, Comparative Examples 1 to 3 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.

[0116] <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 would be 25 μm, and dried at 130°C for 3 minutes (B-stage product). 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 (C-stage product). 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. After the measurement, the dielectric loss tangent T Ｂ , dielectric loss tangent T of C stage product Ｃ The rate of change in dielectric loss tangent was calculated based on the following formula: Rate of change in dielectric loss tangent (%) = (T Ｂ -T Ｃ ) / T Ｂ ×100 <Evaluation criteria for relative dielectric constant> ○: Less than 2.5 △: 2.5 or more and 2.7 or less ×: More than 2.7 <Evaluation criteria for dielectric loss tangent> ○: 0.002 or less △: More than 0.002 and 0.005 or less ×: More than 0.005

[0117] (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

[0118] (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

[0119]

[0120]

[0121] As is clear from Table 1, Examples 1 to 6 are excellent in dielectric properties, peel strength, and solder heat resistance. Comparing Examples 1 to 3, it is clear that the dielectric properties can be changed by changing the content ratio and type of epoxy resin (B).

[0122] On the other hand, Comparative Example 1 contained only epoxy resin (B) without containing epoxy resin (A), and therefore the dielectric loss tangent deteriorated. Comparative Example 2 contained no epoxy resin (A) and a smaller amount of epoxy resin (B) than Comparative Example 1, and therefore the dielectric loss tangent improved, but the crosslink density decreased and the solder heat resistance deteriorated. Comparative Example 3 contained epoxy resin (A), but contained a large amount of epoxy resin (B), and therefore the dielectric properties deteriorated.

[0123] It is also clear that the dielectric loss tangent of the adhesive compositions of Examples 1 and 4 to 6, which contain epoxy resin (A), drops significantly from the B-stage product to the C-stage product. On the other hand, the adhesive compositions of Comparative Examples 1 and 2, which do not contain epoxy resin (A), and the adhesive composition of Comparative Example 3, which contains a high content of epoxy resin (B), do not fully exhibit the effect of the epoxy resin (A), and therefore there was almost no change in the dielectric loss tangent of the B-stage product and the C-stage product.

[0124] 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. An adhesive composition comprising a polyimide resin and an epoxy resin (E), wherein the epoxy resin (E) comprises an epoxy resin (A) represented by formula (I), and the content of a glycidyl ether type epoxy resin (B) contained as the epoxy resin (E) is 5 parts by mass or less per 100 parts by mass of the polyimide resin. [In formula (I), R 1 ~R 5 Each independently represents a hydrogen atom or C 1-10 represents an alkyl group.

2. The adhesive composition according to claim 1, wherein the content of the epoxy resin (A) is 0.01 parts by mass or more and 20 parts by mass or less per 100 parts by mass of the polyimide resin.

3. The acid value of the polyimide resin is 10 equivalents / 10 6 g or more 1000 equivalents / 10 6 2. The adhesive composition according to claim 1, wherein the viscosity is 0.1 g or less.

4. An adhesive composition according to claim 1, in which the ratio represented by (total epoxy value of said epoxy resin (E) / total acid value of said polyimide resin) is 0.5 or more and 10.0 or less.

5. An adhesive composition according to claim 1, wherein the content of the epoxy resin (A) is 70 mass% or more in 100 mass% of the epoxy resin (E).

6. The adhesive composition according to claim 1, wherein the content of the epoxy resin (B) is 25 mass% or less in 100 mass% of the epoxy resin (E).

7. In the formula (I), R 1 and / or R 5 C 1-10 2. The adhesive composition according to claim 1, wherein the alkyl group is an alkyl group.

8. An adhesive composition according to claim 1, wherein the total amount of the epoxy resin (A) and the glycidyl ether type epoxy resin (B) is 50 mass% or more in 100 mass% of the epoxy resin (E).

9. The adhesive composition according to claim 1, wherein the glycidyl ether type epoxy resin (B) is an epoxy resin having a chemical structure represented by formula (II) or formula (III) in the molecule. [In formula (II), R 6 ~R 9 Each independently represents a hydrogen atom or C 1-10 represents an alkyl group. * represents a bond. [In formula (III), R 26 ~R 29 Each independently represents a hydrogen atom or C 1-10 represents an alkyl group. * represents a bond.

10. The adhesive composition according to claim 1, which does not contain the glycidyl ether type epoxy resin (B).

11. The adhesive composition according to claim 1, which contains the glycidyl ether type epoxy resin (B), and the content of the glycidyl ether type epoxy resin (B) is 0.5 parts by mass or more and 5 parts by mass or less per 100 parts by mass of the polyimide resin.

12. The adhesive composition according to claim 1, wherein the chlorine concentration is 0.01 to 300 ppm based on the solid content of the adhesive composition.

13. The adhesive composition according to any one of claims 1 to 12, which is for use on a printed wiring board.

14. 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 any one of claims 1 to 12.

15. The adhesive sheet according to claim 14, wherein the rate of change in dielectric tangent calculated based on the following formula is 8 to 70%. Ｂ -T Ｃ ) / T Ｂ ×100 (in the above formula, T Ｂ : Dielectric tangent of a B-stage product obtained by applying the adhesive composition to a Teflon (registered trademark) sheet having a thickness of 100 μm so that the thickness after drying is 25 μm and drying at 130° C. for 3 minutes Ｃ : Dielectric loss tangent of a C-stage product obtained by heat-treating the B-stage product at 180°C for 3 hours to harden it.

16. A laminate in which the adhesive composition according to any one of claims 1 to 12 is laminated to a substrate which is a resin substrate, a metal substrate or a paper substrate.

17. A printed wiring board comprising the laminate according to claim 16 as a component.

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