Bismaleimide-based adhesive compositions, cured products, adhesive sheets, and flexible printed circuit boards

Abstract

To provide a bismaleimide-based adhesive composition which has low dielectric characteristics and excellent adhesiveness to substrates such as a copper foil and a polyimide sheet.SOLUTION: The bismaleimide-based adhesive composition contains: a bismaleimide resin (A) obtained by reacting aromatic tetracarboxylic acids (a1), a dimer diamine (a2), and maleic anhydride (a3); and an inorganic filler (B). The bismaleimide resin (A) has a weight average molecular weight of 7,000-25,000. The content of the inorganic filler (B) is 10-55 mass% based on the total solid content of the adhesive composition.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a bismaleimide-based adhesive composition, a cured product, an adhesive sheet, and a flexible printed wiring board. More specifically, the present invention relates to a novel bismaleimide-based adhesive composition having excellent low dielectric properties and further having high adhesiveness to substrates such as copper foil and polyimide sheet.

Background Art

[0002] Flexible printed wiring boards (hereinafter abbreviated as "FPC") and multilayer wiring boards using FPC are used in products such as mobile communication devices such as mobile phones and smartphones, their base station devices, network-related electronic devices such as server routers, and large computers.

[0003] In recent years, in those products, high-frequency electrical signals are used to transmit and process a large amount of information at high speed. However, since high-frequency signals are very likely to attenuate, measures to suppress transmission loss are also required for the above FPC and multilayer wiring boards.

[0004] Transmission loss can be distinguished into "dielectric loss" derived from the dielectric, that is, the insulating material around the conductor (copper circuit), and "conductor loss" derived from the copper circuit itself, and it is necessary to suppress both.

[0005] Dielectric loss depends on the frequency, the dielectric constant, and the dielectric tangent of the insulating material around the copper circuit. And the higher the frequency, the more necessary it is to use a material having a low dielectric constant and a low dielectric tangent as the insulating material.

[0006] On the other hand, conductor loss is caused by the skin effect, that is, the phenomenon that the alternating current density on the surface of the copper circuit increases and its resistance increases, and becomes prominent when the frequency exceeds 1 GHz. The main measure to suppress conductor loss is to smooth the surface of the copper circuit.

[0007] To suppress dielectric loss, as mentioned above, it is best to use a material with low dielectric constant and low dielectric loss as the insulating material, and conventionally, certain polyimides have been used as such materials (see Patent Documents 1 and 2). [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2009-299040 [Patent Document 2] Japanese Patent Publication No. 2014-045076 [Overview of the initiative] [Problems that the invention aims to solve]

[0009] However, the insulating materials mentioned above have the problem of not adhering well to smooth copper circuits because they either do not have polar groups, i.e., functional groups such as hydroxyl groups, carboxyl groups, and nitrile groups, or only have a small amount of them. Conversely, materials that have many such functional groups tend to have high dielectric constant and dielectric loss tangent, even if they have high adhesion to smooth copper circuits.

[0010] Therefore, the main objective of the present invention is to provide a novel bismaleimide adhesive that has low dielectric constant and dielectric loss tangent (hereinafter, both may be collectively referred to as "dielectric properties") and good adhesion to copper and polyimide films, particularly copper having a smooth surface.

[0011] In other words, the present invention aims to provide a bismaleimide-based adhesive composition that has low dielectric properties and excellent adhesion to substrates such as copper foil and polyimide sheets. The present invention also aims to provide cured products, adhesive sheets, and flexible printed circuit boards using the above-mentioned bismaleimide-based adhesive composition. [Means for solving the problem]

[0012] As a result of diligent research to solve the above problems, the present inventors have found that a bismaleimide adhesive composition comprising a bismaleimide resin (A) obtained by reacting aromatic tetracarboxylic acids (a1), dimer amine (a2), and maleic anhydride (a3), and an inorganic filler (B), wherein the content of the inorganic filler (B) is within a predetermined range, has excellent low dielectric properties and further exhibits high adhesion to substrates such as copper foil and polyimide sheets, thus completing the present invention.

[0013] In other words, the present invention provides the following inventions. [1] A bismaleimide adhesive composition comprising a bismaleimide resin (A) obtained by reacting aromatic tetracarboxylic acids (a1), a dimer amine (a2), and maleic anhydride (a3), and an inorganic filler (B), wherein the content of the inorganic filler (B) is 5 to 55% by mass based on the total solid content of the adhesive composition. [2] The bismaleimide adhesive composition according to [1] above, wherein the aromatic tetracarboxylic acid (a1) is pyromellitic anhydride or a compound represented by the following general formula (1). [ka] [In formula (1), X represents a single bond or at least one group selected from the following group.] [ka] [3] The bismaleimide adhesive composition according to [1] or [2] above, wherein the dimer amine (a2) is a compound represented by the following general formula (2) and / or general formula (2'). [ka] [ka] [In Formulas (2) and (2’), m, n, p, and q each represent an integer of 1 or more selected such that m + n = 6 to 17 and p + q = 8 to 19, and the bond shown by a broken line means a carbon-carbon single bond or a carbon-carbon double bond. However, when the bond shown by a broken line is a carbon-carbon double bond, Formulas (2) and (2’) have a structure in which the number of hydrogen atoms bonded to each carbon atom constituting the carbon-carbon double bond is reduced by one from the numbers shown in Formulas (2) and (2’).] [4] The bismaleimide-based adhesive composition according to any one of [1] to [3] above, wherein the weight average molecular weight of the above bismaleimide resin (A) is 3,000 to 25,000. [5] The bismaleimide-based adhesive composition according to any one of [1] to [4] above, wherein the above inorganic filler is silica. [6] The bismaleimide-based adhesive composition according to any one of [1] to [5] above, further comprising a polymerization initiator (D). [7] The bismaleimide-based adhesive composition according to [6] above, wherein the above polymerization initiator (D) is at least one selected from the group consisting of an organic peroxide, an imidazole compound, a phosphine compound, and a phosphonium salt compound. [8] The bismaleimide-based adhesive composition according to any one of [1] to [7] above, wherein the average particle diameter of the above inorganic filler (B) is 100 nm to 10 μm. [9] The bismaleimide-based adhesive composition according to any one of [1] to [8] above, wherein the average particle diameter of the above inorganic filler (B) is 200 nm to 1.0 μm.

[10] The bismaleimide-based adhesive composition according to any one of [1] to [9] above, wherein the content of the above inorganic filler (B) is 5 to 25% by mass based on the total solid content of the adhesive composition.

[11] A cured product obtained by curing the bismaleimide-based adhesive composition according to any one of [1] to

[10] above.

[12] An adhesive sheet obtained by applying the bismaleimide-based adhesive composition according to any one of [1] to

[10] above to a sheet substrate and drying it.

[13] A laminate obtained by further thermocompression bonding a sheet substrate to the adhesive surface of the adhesive sheet according to

[12] above.

[14] A laminate obtained by further heating the laminate described in

[13] above.

[15] A flexible printed wiring board using the laminate described in

[14] above.

Advantages of the Invention

[0014] According to the present invention, it is possible to provide a bismaleimide-based adhesive composition having low dielectric characteristics and excellent adhesiveness to substrates such as copper foil and polyimide sheet, a cured product using the same, an adhesive sheet, and a flexible printed wiring board.

[0015] The adhesive composition of the present invention not only has excellent low dielectric characteristics in the high frequency band but also has excellent adhesiveness to substrates such as copper foil and polyimide sheet. Further, the cured product (adhesive layer) obtained from the adhesive composition has low tack, a high 5% weight loss temperature, little outgas, and a low coefficient of linear expansion (CTE). Therefore, it is not only useful as an adhesive for manufacturing printed circuit boards (build-up boards, flexible printed wiring boards, etc.) and copper-clad boards for flexible printed wiring boards, but also as an electrical insulating material such as a semiconductor interlayer material, a coating agent, a resist ink, and a conductive paste.

Modes for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described in detail.

[0017] <Bismaleimide-based Adhesive Composition> The bismaleimide adhesive composition of this embodiment comprises a bismaleimide resin (A) (hereinafter also referred to as "component (A)") obtained by reacting aromatic tetracarboxylic acids (a1) (hereinafter also referred to as "component (a1)"), dimer amine (a2) (hereinafter also referred to as "component (a2)"), and maleic anhydride (a3) ​​(hereinafter also referred to as "component (a3)"), and an inorganic filler (B) (hereinafter also referred to as "component (B)"). The bismaleimide adhesive composition of this embodiment may further contain an organic solvent (C) (hereinafter also referred to as "component (C)"). Furthermore, the bismaleimide adhesive composition of this embodiment may further contain a polymerization initiator (D) (hereinafter also referred to as "component (D)").

[0018] (Component A: Bismaleimide resin) Component (A) can be obtained by reacting components (a1), (a2), and (a3).

[0019] (a1) As components, those known as raw materials for polyimide can be used. Specifically, pyromellitic anhydride and compounds represented by the following general formula (1) can be used. [ka] [In formula (1), X represents a single bond or at least one group selected from the following group.] [ka]

[0020] Examples of compounds represented by formula (1) include 4,4'-oxydiphthalic acid dianhydride, 3,3',4,4'-diphenyl ether tetracarboxylic acid dianhydride, 3,3',4,4'-diphenyl sulfone tetracarboxylic acid dianhydride, 3,3',4,4'-biphenyl tetracarboxylic acid dianhydride, 2,2',3,3'-biphenyl tetracarboxylic acid dianhydride, 2,3,3',4'-biphenyl tetracarboxylic acid dianhydride, 2,3,3',4'-diphenyl ether tetracarboxylic acid dianhydride, 2,3,3',4'-diphenyl sulfone tetracarboxylic acid dianhydride, and 2,2-bis(3,3' Examples include 4,4'-tetracarboxyphenyl)tetrafluoropropane dianhydride, 2,2'-bis(3,4-dicarboxyphenoxyphenyl)sulfone dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, butane-1,2,3,4-tetracarboxylic acid, 2,3,5-tricarboxycyclopentylacetic anhydride, 4,4'-[propane-2,2-diylbis(1,4-phenyleneoxy)]diphthalic acid dianhydride, and 4,4'-(hexafluoroisopropylidene)diphthalic acid anhydride. These can be used individually or in combination of two or more.

[0021] (a2) The component is a compound derived from a dimer acid, which is a dimer of an unsaturated fatty acid such as oleic acid, as described in, for example, Japanese Patent Publication No. 9-12712. In this embodiment, known dimer amines can be used without particular limitation, but those represented by the following general formula (2) and / or general formula (2') are preferred.

[0022] [ka] [ka] [In equations (2) and (2'), m, n, p, and q represent integers of 1 or more selected such that m+n = 6 to 17 and p+q = 8 to 19, respectively. The dashed lines indicate carbon-carbon single bonds or carbon-carbon double bonds. However, if the dashed line indicates a carbon-carbon double bond, equations (2) and (2') will have a structure in which the number of hydrogen atoms bonded to each carbon atom constituting the carbon-carbon double bond is reduced by one from the number shown in equations (2) and (2').]

[0023] As for the dimer amine, those represented by the above general formula (2') are preferred from the viewpoint of solubility in organic solvents, heat resistance, heat adhesion, and low viscosity, and compounds represented by the following formula (3) are particularly preferred. [ka]

[0024] Examples of commercially available dimer amines include PRIAMINE 1075 and PRIAMINE 1074 (both manufactured by Croda Japan Co., Ltd.). These can be used individually or in combination of two or more.

[0025] Component (A) can be produced by various known methods. For example, first, component (a1) and component (a2) are subjected to a polyaddition reaction at a temperature of about 60 to 120°C, preferably 70 to 90°C, for about 0.1 to 2 hours, preferably 0.1 to 1.0 hours. Next, the obtained polyaddition is subjected to an imidation reaction, i.e., a dehydration ring-closing reaction, at a temperature of about 80 to 250°C, preferably 100 to 200°C, for about 0.5 to 30 hours, preferably 0.5 to 10 hours. Subsequently, the dehydrated ring-closing product and component (a3) ​​are subjected to a maleimidation reaction, i.e., a dehydration ring-closing reaction, at a temperature of about 60 to 250°C, preferably 80 to 200°C, for about 0.5 to 30 hours, preferably 0.5 to 10 hours, to obtain the desired component (A).

[0026] In the imidation reaction or maleimidation reaction, various known reaction catalysts, dehydrating agents, and organic solvents described later can be used. Examples of reaction catalysts include aliphatic tertiary amines such as triethylamine, aromatic tertiary amines such as dimethylaniline, heterocyclic tertiary amines such as pyridine, picoline, and isoquinoline, or organic acids such as methanesulfonic acid and p-toluenesulfonic acid monohydrate. These can be used individually or in combination of two or more. Examples of dehydrating agents include aliphatic acid anhydrides such as acetic anhydride and aromatic acid anhydrides such as benzoic anhydride. These can be used individually or in combination of two or more.

[0027] Furthermore, component (A) can be purified by various known methods to increase its purity. For example, first, component (A) dissolved in an organic solvent and pure water are placed in a separatory funnel. Next, the separatory funnel is shaken and allowed to stand. After the aqueous layer and organic layer separate, component (A) can be purified by recovering only the organic layer.

[0028] The molecular weight of component (A) can be controlled by the number of moles of component (a1) and component (a2). The smaller the number of moles of component (a1) compared to the number of moles of component (a2), the smaller the molecular weight can be. To facilitate achieving the effects of the present invention, the ratio of [number of moles of component (a1)] / [number of moles of component (a2)] is usually in the range of 0.30 to 0.85, preferably 0.50 to 0.80.

[0029] (A) Regarding the molecular weight of component (A), from the viewpoint of solubility in solvents and heat resistance, a weight-average molecular weight of 3,000 to 25,000 is preferred, and 7,000 to 20,000 is more preferred. When the weight-average molecular weight is 25,000 or less, solubility in organic solvents is good, and when it is 3,000 or more, a sufficient effect of improving heat resistance tends to be obtained.

[0030] Component (A) in this embodiment may be a commercially available compound. Specifically, for example, BMI-3000CG (synthesized from dimer amine, pyromellitic dianhydride, and maleic anhydride), BMI-1500, BMI-1700, BMI-5000, etc., manufactured by DESIGNER MOLECURES Inc., can be suitably used. Component (A) can be used alone or in combination of two or more.

[0031] ((B) Component: Inorganic filler) Component (B) can be any known inorganic filler that is suitable for use in bismaleimide adhesive compositions, without any particular limitations. Examples of component (B) include aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, calcium oxide, magnesium oxide, aluminum oxide, aluminum nitride, aluminum borate whiskers, boron nitride, silica, graphite powder, boehmite, etc. Among these, silica is particularly preferred because of its excellent low dielectric loss tangent. Component (B) can be used alone or in combination of two or more.

[0032] The average particle size of component (B) may be 50 nm or more, 100 nm or more, or 200 nm or more, and may be 10 μm or less, 5.0 μm or less, 3.0 μm or less, or 1.0 μm or less. The average particle size of component (B) is preferably 100 nm to 10 μm or 50 nm to 5.0 μm, more preferably 100 nm to 3.0 μm, and even more preferably 200 nm to 1.0 μm. When the average particle size of component (B) is within the above range, the surface roughness of the adhesive sheet can be reduced, and the adhesion to the substrate such as polyimide film and copper foil can be improved.

[0033] The average particle size of component (B) above is the median diameter (d50) value at which the integrated particle size in the volume integrated particle size distribution reaches 50%. The above average particle size can be measured using a laser diffraction scattering particle size distribution analyzer.

[0034] Component (B) is preferably surface-treated, preferably a surface-treated product with a coupling agent, and more preferably a surface-treated product with a silane coupling agent. Surface treatment of component (B) not only improves the dispersibility of component (B) in organic solvents, but also further reduces the surface roughness of the adhesive sheet, thereby improving adhesion to substrates such as polyimide film and copper foil.

[0035] Examples of the coupling agents mentioned above include silane coupling agents, titanium coupling agents, and aluminum coupling agents. Examples of the silane coupling agents include methacrylicsilane, acrylicsilane, aminosilane, phenylaminosilane, imidazolesilane, phenylsilane, vinylsilane, and epoxysilane. These can be used individually or in combination of two or more.

[0036] The content of component (B) is 5 to 55% by mass, preferably 5 to 50% by mass, more preferably 5 to 25% by mass, or 10 to 35% by mass, based on the total amount of solids (non-volatile content) of the adhesive composition (100% by mass). When the content of component (B) is 55% by mass or less, the decrease in adhesiveness tends to be suppressed, and when it is 5% by mass or more, the effect of reducing the dielectric loss tangent and the effect of improving heat resistance tend to be sufficiently obtained.

[0037] ((C) Component: Organic solvent) Component (C) is not particularly limited as long as it dissolves component (A). Examples of component (C) include aromatic hydrocarbons such as benzene, toluene, xylene, and mesitylene; alcohol-based solvents such as methanol, ethanol, isopropyl alcohol, butanol, pentanol, hexanol, propanediol, and phenol; ketone-based solvents such as acetone, methyl isobutyl ketone, methyl ethyl ketone, pentanone, hexanone, cyclopentanone, cyclohexanone, isophorone, and acetophenone; cellsolves such as methyl cellsolve and ethyl cellsolve; 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. These can be used individually or in combination of two or more. In a preferred embodiment, it is preferable to use a combination of toluene or mesitylene, an aromatic hydrocarbon with high solubility for component (A), and methyl ethyl ketone or methyl isobutyl ketone, a ketone-based solvent with high dispersibility for component (B).

[0038] The amount of component (C) used is not particularly limited, but it is generally sufficient to use it in a range where the non-volatile content of the adhesive composition of this embodiment is approximately 20 to 65% by mass.

[0039] (Component D: Polymerization initiator) (D) Specifically, examples of component (D) include organic peroxides, imidazole compounds, phosphine compounds, and phosphonium salt compounds. These can be used individually or in combination of two or more. Among these, imidazole compounds are particularly preferred because they have excellent function as polymerization initiators and also have excellent low dielectric properties.

[0040] Examples of organic peroxides include methyl ethyl ketone peroxide, methylcyclohexanone peroxide, methyl acetate peroxide, acetylacetone peroxide, 1,1-bis(t-butyl peroxy)3,3,5-trimethylcyclohexane, 1,1-bis(t-hexyl peroxy)cyclohexane, 1,1-bis(t-hexyl peroxy)3,3,5-trimethylcyclohexane, 1,1-bis(t-butyl peroxy)cyclohexane, and 2,2-bis(4,4-di-t-butyl (Turperoxycyclohexyl)propane, 1,1-bis(t-butylperoxy)cyclododecane, n-butyl 4,4-bis(t-butylperoxy)valerate, 2,2-bis(t-butylperoxy)butane, 1,1-bis(t-butylperoxy)-2-methylcyclohexane, t-butyl hydroperoxide, p-menthane hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, t-hexyl hydroperoxide, dicumyl peroxide, 2,5-dimethyl-2 ,5-bis(t-butylperoxy)hexane, α,α'-bis(t-butylperoxy)diisopropylbenzene, t-butylcumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexine-3, isobutyryl peroxide, 3,5,5-trimethylhexanoyl peroxide, octanoyl peroxide, lauroyl peroxide, cinnamate peroxide, m-toluyl peroxide, benzoyl peroxide, diisopropyl peroxide -Oxydicarbonate, bis(4-t-butylcyclohexyl)peroxydicarbonate, di-3-methoxybutyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, di-sec-butyl peroxydicarbonate, di(3-methyl-3-methoxybutyl)peroxydicarbonate, di(4-t-butylcyclohexyl)peroxydicarbonate, α,α'-bis(neodecanoylperoxy)diisopropylbenzene, cumylperoxyneodecanoate, 1,1,3,3,-Tetramethylbutyl peroxyneodecanoate, 1-cyclohexyl-1-methylethyl peroxyneodecanoate, t-hexyl peroxyneodecanoate, t-butyl peroxyneodecanoate, t-hexyl peroxypivalate, t-butyl peroxypivalate, 2,5-dimethyl-2,5-bis(2-ethylhexanoylperoxy)hexane, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, 1-cyclohexyl-1-methylethyl peroxy-2-ethylhexanoate, t-hexyl peroxy-2-ethylhexanoate, t-butyl peroxy-2-ethylhexanoate, t-butyl peroxyisobutyrate, t-butyl Examples include peroxymalic acid, t-butyl peroxylaurate, t-butyl peroxy-3,5,5-trimethylhexanoate, t-butyl peroxyisopropyl monocarbonate, t-butyl peroxy-2-ethylhexyl monocarbonate, 2,5-dimethyl-2,5-bis(benzoylperoxy)hexane, t-butyl peroxyacetate, t-hexyl peroxybenzoate, t-butyl peroxy-m-toluylbenzoate, t-butyl peroxybenzoate, bis(t-butylperoxy)isophthalate, t-butyl peroxyallyl monocarbonate, and 3,3',4,4'-tetra(t-butylperoxycarbonyl)benzophenone. These can be used individually or in combination of two or more. Among these organic peroxides, dicumyl peroxide, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, and α,α'-bis(t-butylperoxy)diisopropylbenzene are preferred.

[0041] Examples of imidazole compounds include 2-ethyl-4-methylimidazole, 2-methylimidazole, 2-ethylimidazole, 2,4-dimethylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 2-phenyl-4,5-dihydroxymethylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 1-vinyl-2-methylimidazole, 1-propyl-2-methylimidazole, 2-isopropylimidazole, 1-cyanomethyl-2-methylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, and 1-cyanoethyl-2-phenylimidazole. In particular, 1-cyanoethyl-2-phenylimidazole and 2-ethyl-4-methylimidazole are preferred due to their high solubility with the adhesive composition of this embodiment. These can be used individually or in combination of two or more.

[0042] Examples of phosphine compounds include primary phosphines, secondary phosphines, and tertiary phosphines. Specific examples of primary phosphines include alkyl phosphines such as ethyl phosphine and propyl phosphine, and phenyl phosphines. Specific examples of secondary phosphines include dialkyl phosphines such as dimethyl phosphine and diethyl phosphine, and secondary phosphines such as diphenyl phosphine, methylphenyl phosphine, and ethylphenyl phosphine. Tertiary phosphines include trialkyl phosphines such as trimethylphosphine, triethylphosphine, tributylphosphine, and trioctylphosphine, as well as tricyclohexylphosphine, triphenylphosphine, alkyldiphenylphosphine, dialkylphenylphosphine, tripenzylphosphine, tritrillylphosphine, tri-p-styrylphosphine, tris(2,6-dimethoxyphenyl)phosphine, tri-4-methylphenylphosphine, tri-4-methoxyphenylphosphine, and tri-2-cyanoethylphosphine. Among these, tertiary phosphines are preferred. These can be used individually or in combination of two or more types.

[0043] Examples of phosphonium salt compounds include compounds having tetraphenylphosphonium salts, alkyltriphenylphosphonium salts, and tetraalkylphosphonium. Specifically, these include tetraphenylphosphonium-thiocyanate, tetraphenylphosphonium-tetra-p-methylphenylborate, butyltriphenylphosphonium-thiocyanate, tetraphenylphosphonium-phthalic acid, tetrabutylphosphonium-1,2-cyclohexyldicarboxylic acid, tetrabutylphosphonium-1,2-cyclohexyldicarboxylic acid, and tetrabutylphosphonium-lauric acid. These can be used individually or in combination of two or more.

[0044] The content of component (D) is not particularly limited, but is preferably 0.1 to 10.0 parts by mass, and more preferably 1.0 to 5.0 parts by mass, per 100 parts by mass of component (A).

[0045] The adhesive composition of this embodiment is prepared according to generally accepted methods. Examples of preparation methods include melt mixing, powder mixing, and solution mixing. In addition, other components besides the essential components of this embodiment, such as mold release agents, flame retardants, ion trapping agents, antioxidants, adhesion promoters, stress reducers, colorants, and coupling agents, may be added within limits that do not impair the effects of the present invention. Furthermore, the adhesive composition of this embodiment may also contain resins other than the above-mentioned component (A), such as epoxy resins, acrylate compounds, vinyl compounds, benzoxazine compounds, and bismaleimide compounds.

[0046] (Release agent) Release agents are added to improve mold release properties. Known release agents can be used, such as carnauba wax, rice wax, candelilla wax, polyethylene, polyethylene oxide, polypropylene, montanic acid, montan wax (an ester compound of montanic acid with saturated alcohol, 2-(2-hydroxyethylamino)ethanol, ethylene glycol, glycerin, etc.), stearic acid, stearic acid esters, and stearic acid amides. These can be used individually or in combination of two or more.

[0047] (Flame retardant) Flame retardants are added to impart flame retardancy, and all known flame retardants can be used without particular limitation. Examples of flame retardants include phosphazene compounds, silicon compounds, zinc molybdate-supported talc, zinc molybdate-supported zinc oxide, aluminum hydroxide, magnesium hydroxide, and molybdenum oxide. These can be used individually or in combination of two or more.

[0048] (Ion trapping agent) Ion trapping agents are added to liquid resin compositions to capture ionic impurities and prevent thermal and hygroscopic degradation. Any known ion trapping agent can be used, and there are no particular limitations. Examples of ion trapping agents include hydrotalcites, bismuth hydroxide compounds, and rare earth oxides. These can be used individually or in combination of two or more.

[0049] <Cured product> The cured product of this embodiment is obtained by curing the adhesive composition of this embodiment. Specifically, it can be obtained by heating the adhesive composition at approximately 150 to 250°C for approximately 5 minutes to 3 hours.

[0050] The shape of the cured product in this embodiment is not particularly limited, but when used for bonding substrate sheets, the film thickness can usually be about 1 to 100 μm, preferably about 3 to 50 μm, and the film thickness can be adjusted as appropriate depending on the application.

[0051] <Adhesive Sheet> The adhesive sheet of this embodiment is obtained by applying the adhesive composition of this embodiment to a sheet substrate and drying it. Examples of suitable sheet substrates include organic substrates such as polyimide, polyimide-silica hybrid, polyamide, polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polymethyl methacrylate (PMMA), polystyrene resin (PSt), polycarbonate resin (PC), acrylonitrile-butadiene-styrene resin (ABS), ethylene terephthalate, phenol, phthalic acid, hydroxynaphthoic acid, and p-hydroxybenzoic acid (so-called liquid crystal polymers; such as "Vecter" manufactured by Kuraray Co., Ltd.). Among these, polyimide film, particularly polyimide-silica hybrid film, is preferred in terms of heat resistance and dimensional stability. The thickness of the sheet substrate can be appropriately set according to the application.

[0052] <Laminate> The laminate of this embodiment is obtained by further heat-pressing a sheet substrate onto the adhesive surface of the adhesive sheet. Suitable sheet substrates include metals such as glass, iron, aluminum, 42 alloy, and copper, as well as inorganic substrates such as ITO, silicon, and silicon carbide, and their thickness can be appropriately set according to the application. Furthermore, the laminate may be further heat-treated.

[0053] <Flexible printed circuit boards and flexible printed wiring boards> The flexible printed circuit board of this embodiment uses the above-mentioned laminate, and is obtained by further bonding the adhesive surface of the adhesive sheet to the inorganic substrate surface of the laminate. Preferably, the flexible printed circuit board uses a polyimide film as the organic substrate and a metal foil (particularly copper foil) as the inorganic substrate. A flexible printed circuit board is then obtained by soft etching the metal surface of the flexible printed circuit board to form a circuit, and then bonding the adhesive sheet on top of it and heat-pressing it. [Examples]

[0054] The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to these. In each example, parts and percentages are by mass unless otherwise specified.

[0055] <Manufacturing Example 1> In a 1 L flask equipped with a condenser, nitrogen inlet tube, thermocouple, and stirrer, 52.8 parts by mass of pyromellitic anhydride (manufactured by Daicel Corporation), 432.5 parts by mass of mesitylene (manufactured by Toyo Gosei Kogyo Co., Ltd.), and 94.0 parts by mass of ethanol (manufactured by Wako Pure Chemical Industries, Ltd.) were added. After adding the ingredients, the temperature was raised to 80°C and maintained for 0.5 hours, and 176.7 parts by mass of dimer amine (trade name "PRIAMINE 1075," manufactured by Croda Japan Co., Ltd.) was added dropwise. After the dropwise addition, 3.7 parts by mass of methanesulfonic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was added. The temperature was then raised to 165°C, and a dehydration and ring-closing reaction was carried out at 165°C for 1 hour to remove water and ethanol from the reaction solution and obtain the intermediate polyimide resin. Next, the obtained polyimide resin was cooled to 130°C, 23.4 parts by mass of maleic anhydride (manufactured by Fuso Chemical Industries, Ltd.) were added, the temperature was raised to 165°C, and a dehydration and ring-closing reaction was carried out at 165°C for 4 hours to remove water from the reaction solution and obtain bismaleimide resin.

[0056] The obtained bismaleimide resin was placed in a separatory funnel, 1000 parts by mass of pure water were added, the separatory funnel was shaken, and it was allowed to stand. After standing, the aqueous layer and the organic layer separated, and only the organic layer was recovered. The recovered organic layer was placed in a 1 L glass container equipped with a condenser, nitrogen inlet tube, thermocouple, stirrer, and vacuum pump, and the temperature was raised to 88-93°C to remove water. Then the temperature was raised to 130°C, and the solvent was removed under reduced pressure of -0.1 MPa for 1 hour. After the solvent was removed, it was cooled to 100°C and brought to atmospheric pressure, and then 135.9 parts by mass of toluene (manufactured by Yamaichi Chemical Industry Co., Ltd.) was added to obtain a solution of bismaleimide resin (A-1) (non-volatile content of 59.8% by mass).

[0057] <Manufacturing Example 2> In a reaction vessel similar to that used in Production Example 1, 66.7 parts by mass of 4,4'-oxydiphthalic anhydride (manufactured by Wako Pure Chemical Industries, Ltd.), 426.0 parts by mass of mesitylene (manufactured by Toyo Gosei Kogyo Co., Ltd.), and 91.2 parts by mass of ethanol (manufactured by Wako Pure Chemical Industries, Ltd.) were added. After adding the ingredients, the temperature was raised to 80°C and maintained for 0.5 hours, and 159.0 parts by mass of dimer amine (trade name "PRIAMINE 1075", manufactured by Croda Japan Co., Ltd.) was added dropwise. After the dropwise addition, 3.3 parts by mass of methanesulfonic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was added. The temperature was then raised to 165°C, and a dehydration and ring-closing reaction was carried out at 165°C for 1 hour to remove water and ethanol from the reaction solution and obtain the intermediate polyimide resin. Next, the obtained polyimide resin was cooled to 130°C, 21.1 parts by mass of maleic anhydride (manufactured by Fuso Chemical Industries, Ltd.) were added, the temperature was raised to 165°C, and a dehydration and ring-closing reaction was carried out at 165°C for 4 hours to remove water from the reaction solution and obtain bismaleimide resin.

[0058] The obtained bismaleimide resin was placed in a separatory funnel, 1000 parts by mass of pure water were added, the separatory funnel was shaken, and it was allowed to stand. After standing, the aqueous layer and the organic layer separated, and only the organic layer was recovered. The recovered organic layer was placed in a 1 L glass container equipped with a condenser, nitrogen inlet tube, thermocouple, stirrer, and vacuum pump, and the temperature was raised to 88-93°C to remove water. Then the temperature was raised to 150°C, and the solvent was removed under reduced pressure of -0.1 MPa for 1 hour. After the solvent was removed, it was cooled to 100°C and brought to atmospheric pressure, and then 122.3 parts by mass of toluene (manufactured by Yamaichi Chemical Industry Co., Ltd.) was added to obtain a solution of bismaleimide resin (A-2) (non-volatile content of 59.9% by mass).

[0059] <Manufacturing Example 3> In a reaction vessel similar to that used in Production Example 1, 63.2 parts by mass of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (manufactured by Wako Pure Chemical Industries, Ltd.), 419.6 parts by mass of mesitylene (manufactured by Toyo Gosei Kogyo Co., Ltd.), and 90.1 parts by mass of ethanol (manufactured by Wako Pure Chemical Industries, Ltd.) were added. After adding the ingredients, the temperature was raised to 80°C and maintained for 0.5 hours, and 159.0 parts by mass of dimeramine (trade name "PRIAMINE 1075", manufactured by Croda Japan Co., Ltd.) was added dropwise. After the dropwise addition, 3.3 parts by mass of methanesulfonic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was added. The temperature was then raised to 165°C, and a dehydration and ring-closing reaction was carried out at 165°C for 1 hour to remove water and ethanol from the reaction solution and obtain the intermediate polyimide resin. Next, the obtained polyimide resin was cooled to 130°C, 21.1 parts by mass of maleic anhydride (manufactured by Fuso Chemical Industries, Ltd.) were added, the temperature was raised to 165°C, and a dehydration and ring-closing reaction was carried out at 165°C for 4 hours to remove water from the reaction solution and obtain bismaleimide resin.

[0060] The obtained bismaleimide resin was placed in a separatory funnel, 1000 parts by mass of pure water were added, the separatory funnel was shaken, and it was allowed to stand. After standing, the aqueous layer and the organic layer separated, and only the organic layer was recovered. The recovered organic layer was placed in a 1 L glass container equipped with a condenser, nitrogen inlet tube, thermocouple, stirrer, and vacuum pump, and the temperature was raised to 88-93°C to remove water. Then the temperature was raised to 150°C, and the solvent was removed under reduced pressure of -0.1 MPa for 1 hour. After the solvent was removed, it was cooled to 100°C and brought to atmospheric pressure, and then 120.5 parts by mass of toluene (manufactured by Yamaichi Chemical Industry Co., Ltd.) was added to obtain a solution of bismaleimide resin (A-3) (non-volatile content of 59.3% by mass).

[0061] <Manufacturing Example 4> In a reaction vessel similar to that used in Production Example 1, 91.0 parts by mass of 4,4'-[propane-2,2-diyrbis(1,4-phenyleneoxy)]diphthalic acid dianhydride (trade name "BISDA1000", manufactured by SABIC Innovative Plastics Japan LLC), 415.3 parts by mass of mesitylene (manufactured by Toyo Gosei Kogyo Co., Ltd.), and 86.7 parts by mass of ethanol (manufactured by Wako Pure Chemical Industries, Ltd.) were added. After adding the ingredients, the temperature was raised to 80°C and maintained for 0.5 hours, and 129.6 parts by mass of dimeramine (trade name "PRIAMINE1075", manufactured by Croda Japan Co., Ltd.) was added dropwise. After the dropwise addition, 2.7 parts by mass of methanesulfonic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was added. The temperature was then raised to 165°C, and a dehydration and ring-closing reaction was carried out at 165°C for 1 hour to remove water and ethanol from the reaction solution and obtain the intermediate polyimide resin. Next, the obtained polyimide resin was cooled to 130°C, 17.2 parts by mass of maleic anhydride (manufactured by Fuso Chemical Industries, Ltd.) was added, the temperature was raised to 165°C, and a dehydration and ring-closing reaction was carried out at 165°C for 4 hours to remove water from the reaction solution and obtain bismaleimide resin.

[0062] The obtained bismaleimide resin was placed in a separatory funnel, 1000 parts by mass of pure water were added, the separatory funnel was shaken, and it was allowed to stand. After standing, the aqueous layer and the organic layer separated, and only the organic layer was recovered. The recovered organic layer was placed in a 1 L glass container equipped with a condenser, nitrogen inlet tube, thermocouple, stirrer, and vacuum pump, and the temperature was raised to 88-93°C to remove water. Then the temperature was raised to 150°C, and the solvent was removed under reduced pressure of -0.1 MPa for 1 hour. After the solvent was removed, it was cooled to 100°C and brought to atmospheric pressure, and then 119.3 parts by mass of toluene (manufactured by Yamaichi Chemical Industry Co., Ltd.) was added to obtain a solution of bismaleimide resin (A-4) (non-volatile content of 59.5% by mass).

[0063] <Comparative Manufacturing Example 1> In a reaction vessel similar to that used in Production Example 1, 36.5 parts by mass of pyromellitic anhydride (manufactured by Daicel Corporation), 429.0 parts by mass of mesitylene (manufactured by Toyo Gosei Kogyo Co., Ltd.), and 88.7 parts by mass of ethanol (manufactured by Wako Pure Chemical Industries, Ltd.) were added. After adding the ingredients, the temperature was raised to 80°C and maintained for 0.5 hours, and 191.6 parts by mass of α,ω-bis(3-aminopropyl)polydimethylsiloxane (trade name "KF-8010", manufactured by Shin-Etsu Chemical Co., Ltd.) was added dropwise. After the dropwise addition, 2.6 parts by mass of methanesulfonic acid (manufactured by Wako Pure Chemical Industries, Ltd.) was added. The temperature was then raised to 165°C, and a dehydration and ring-closing reaction was carried out at 165°C for 1 hour to remove water and ethanol from the reaction solution and obtain the intermediate polyimide resin. Next, the obtained polyimide resin was cooled to 130°C, 16.4 parts by mass of maleic anhydride (manufactured by Fuso Chemical Industries, Ltd.) was added, the temperature was raised to 165°C, and a dehydration and ring-closing reaction was carried out at 165°C for 4 hours to remove water from the reaction solution and obtain bismaleimide resin.

[0064] The obtained bismaleimide resin was placed in a separatory funnel, 1000 parts by mass of pure water were added, the separatory funnel was shaken, and it was allowed to stand. After standing, the aqueous layer and the organic layer separated, and only the organic layer was recovered. The recovered organic layer was placed in a 1 L glass container equipped with a condenser, nitrogen inlet tube, thermocouple, stirrer, and vacuum pump, and the temperature was raised to 88-93°C to remove water. Then the temperature was raised to 150°C, and the solvent was removed under reduced pressure of -0.1 MPa for 1 hour. After the solvent was removed, it was cooled to 100°C and brought to atmospheric pressure, and then 123.2 parts by mass of toluene (manufactured by Yamaichi Chemical Industry Co., Ltd.) was added to obtain a solution of bismaleimide resin (X) (non-volatile content of 59.7% by mass).

[0065] [Table 1]

[0066] PMDA: Pyromellitic anhydride ODPA: 4,4'-Oxydiphthalic anhydride BPDA: 3,3',4,4'-biphenyltetracarboxylic acid dianhydride BISDA: 4,4'-[propane-2,2-diirbis(1,4-phenyleneoxy)]diphthalic anhydride PRIAMINE: Dimer amine KF8010: α,ω-bis(3-aminopropyl)polydimethylsiloxane

[0067] <Method for evaluating physical properties> (Weight average molecular weight (Mw)) The weight-average molecular weight (Mw) was measured by GPC (gel permeation chromatography). A sample prepared by dissolving bismaleimide resin in tetrahydrofuran (THF) to a concentration of 3% by mass was injected in 50 μL into columns heated to 30°C (one GL-R420 (Hitachi High-Tech Fielding Co., Ltd.), one GL-R430 (Hitachi High-Tech Fielding Co., Ltd.), and one GL-R440 (Hitachi High-Tech Fielding Co., Ltd.)). THF was used as the developing solvent, and measurements were performed at a flow rate of 1.6 mL / min. An L-3350 RI detector (Hitachi, Ltd.) was used, and the weight-average molecular weight (Mw) was calculated from the elution time using a molecular weight / elution time curve prepared using standard polystyrene (Tosoh Corporation).

[0068] [Example 1] In a 225 ml cylindrical container, 100 parts by mass of a solution of bismaleimide resin (A-1) obtained in Production Example 1, 21.4 parts by mass of silica-containing slurry (manufactured by Admatex Co., Ltd., product name "SC2050-KNK", 70% silica by mass) as component (B), and 20.0 parts by mass of methyl isobutyl ketone (manufactured by Wako Pure Chemical Industries, Ltd.) as component (C) were placed. Subsequently, the container was covered, and the mixture inside was stirred at 70 rpm for more than 4 hours using a variable mix rotor (manufactured by AS ONE Corporation, product number "VMR-5R") to obtain an adhesive composition with a non-volatile content of 52.9% by mass.

[0069] [Examples 2-8] Each adhesive composition was obtained in the same manner as in Example 1, except that components (A), (B), (C), and (D) were of the types shown in Table 2, and used in the amounts shown in the same table.

[0070] [Comparative Example 1] An adhesive composition was obtained in the same manner as in Example 1, except that the solution of component (X) was used in the amount shown in Table 2 instead of the solution of component (A-1), and the types of components (B) and (C) shown in Table 2 were used in the amounts shown in the same table.

[0071] [Comparative Example 2] An adhesive composition was obtained in the same manner as in Example 1, except that the amount of component (B) used was changed to the amount shown in Table 2.

[0072] [Table 2]

[0073] SC2050-KNK: Silica-containing slurry (manufactured by Admatex Co., Ltd., 70% silica by mass, silica particles surface-treated with phenylaminosilane, average particle size 0.4 μm) MIBK: Methyl isobutyl ketone (manufactured by Wako Pure Chemical Industries, Ltd.) 2E4MZ: 2-Ethyl-4-methylimidazole (manufactured by Wako Pure Chemical Industries, Ltd.)

[0074] (Example 9) In a 225 ml cylindrical container, 100 parts by mass of a solution of bismaleimide resin (A-1) obtained in Production Example 1, 42.7 parts by mass of silica-containing slurry (manufactured by Admatex Co., Ltd., trade name "SC2050-KNK", 70% silica by mass) as component (B), and 25.0 parts by mass of methyl isobutyl ketone (manufactured by Wako Pure Chemical Industries, Ltd.) as component (C) were charged, and the mixture was stirred at 9000 rpm for 20 minutes using a homomixer (manufactured by Primix Co., Ltd., "TK Homomixer MARKII"). Then, 0.60 parts by mass of dicumyl peroxide (manufactured by NOF Corporation, trade name "Perkmyl D") was added as component (D), and the mixture was stirred at 70 rpm for more than 1 hour using a variable mix rotor (manufactured by AS ONE Corporation, model number "VMR-5R") to obtain an adhesive composition with a non-volatile content of 53.6% by mass.

[0075] [Examples 10-19] Each adhesive composition was obtained in the same manner as in Example 9, except that components (A), (B), (C), and (D) were of the types shown in Table 3, and were used in the amounts shown in the same table.

[0076] [Table 3]

[0077] 3SX-CX1: Silica-containing slurry (manufactured by Admatex Co., Ltd., 60.5% by mass of silica, silica particles surface-treated with phenylaminosilane, average particle size 0.3 μm) YA050C-KJK: Silica-containing slurry (manufactured by Admatex Co., Ltd., 51.0% silica by mass, silica particles surface-treated with phenylaminosilane, average particle size 50 nm) DCP: Dicumyl peroxide (manufactured by NOF Corporation)

[0078] <Preparation of adhesive sheet (1)> The adhesive composition of Example 1 was applied using an applicator onto a film vinyl (registered trademark) (PET film, manufactured by Fujimori Kogyo Co., Ltd., trade name "NS14", film thickness 75 μm) to a thickness of 30 μm after drying. The adhesive sheet (1) was then dried in an oven at 130°C for 20 minutes. The adhesive sheets (1) of the other examples and comparative examples were obtained in the same manner.

[0079] <Preparation of hardened sheet (1)> A polyimide film (product name "100EN", manufactured by Toray DuPont Ltd., film thickness 25 μm) was superimposed on the adhesive surface of the adhesive sheet (1) of Example 1, and heat-pressed in a vacuum laminator at 75°C, 0.5 MPa, and for 30 seconds. After heat-pressing, the PET film was peeled off, and a cured sheet (1) was obtained by heat treatment in a hot air dryer at 200°C for 2 hours. Cured sheets (1) were obtained in the same manner for the adhesive compositions of the other examples and comparative examples.

[0080] <Preparation of hardened sheet (2)> The adhesive composition of Example 1 was applied to Sepanium (manufactured by Toyo Aluminum Co., Ltd., trade name "50B2-EA(A)4G / M2", film thickness 50 μm) using an applicator to a thickness of 100 μm after drying, and then dried in an oven at 130°C for 20 minutes. After that, it was heated in an oven at 200°C for 1 hour. After the heat treatment, it was cooled to room temperature and peeled off from the Sepanium to obtain a cured sheet (2).

[0081] <Fabrication of laminate (1)> The adhesive sheet (1) from Example 1, obtained by peeling off the PET film, and two copper foils (product name "F2WS-18", manufactured by Furukawa Electric Co., Ltd., thickness 18 μm) were laminated so that the roughened surface of the copper foils faced the adhesive sheet. The laminates were then heat-pressed together at 200°C, 2 MPa, and 2 hours using a hot press to obtain a laminate (1) in which the copper foils, the cured adhesive sheet, and the copper foils were laminated in this order. Laminates (1) were obtained in the same manner for the adhesive compositions of the other examples and comparative examples.

[0082] <Fabrication of laminate (2)> The adhesive sheet (1) from Example 1, which had been peeled off the PET film, and two polyimide films (product name "100EN", manufactured by Toray DuPont, Ltd., 25 μm thick) were laminated with the adhesive sheet in the middle. The laminates were then heat-pressed at 200°C, 2 MPa, and 2 hours using a hot press to obtain a laminate (2) in which the polyimide film, the cured adhesive sheet, and the polyimide film were laminated in that order. Laminates (2) were obtained in the same manner for the adhesive compositions of the other examples and comparative examples.

[0083] <Evaluation of tuckiness> The glossy side of a copper foil (product name "F2WS-18", manufactured by Furukawa Electric Co., Ltd., 18 μm thick) was placed on the adhesive surface of a hardened sheet (1), and the copper foil was moved horizontally. If the copper foil was sticky and could not be moved, it was considered to have tackiness; if it could be moved horizontally, it was considered to have no tackiness.

[0084] <Adhesive strength> The adhesive strength between the polyimide film and copper foil was measured using laminate (1) and laminate (2). The adhesive strength was measured at room temperature and a tensile speed of 5 mm / s using a 90° peel tester (Yamaden Co., Ltd., RHEONERII CREEP METER RE2-3305B). The results are shown in Tables 4 and 5.

[0085] <Criteria for determining adhesive strength> A: Adhesion strength of 1.0 kN / m or more B: Adhesion strength of 0.5 kN / m or more, and less than 1.0 kN / m C: Adhesion strength less than 0.5 kN / m

[0086] <Dielectric constant and dielectric loss tangent> The copper foil on both sides of the laminate (1) was removed by etching, and after drying at 130°C for 30 minutes, a 10cm x 5cm test specimen was prepared. The relative permittivity and dielectric loss tangent at 10GHz were measured using an SPDR dielectric resonator (manufactured by Agilent Technologies). The results are shown in Tables 4 and 5. Note that for Comparative Example 1, measurement was not possible due to the difficulty in preparing the test specimen by etching.

[0087] <5% weight loss temperature> The copper foil on both sides of the laminate (1) was removed by etching, and after drying at 130°C for 30 minutes, 6.0 to 10.0 mg of the cured adhesive sheet was weighed into an open-type sample container (Seiko Electronics "P / N SSC000E030"), and the 5% weight loss temperature (Td5) was measured under conditions of a nitrogen flow rate of 300 mL / min and a heating rate of 10°C / min. The measuring device used was TG / DTA7200 (Hitachi High-Tech Science Corporation). The results are shown in Tables 4 and 5.

[0088] <Coefficient of linear thermal expansion (CTE) α1, α2> Test specimens measuring 30 mm x 4 mm were prepared from the cured sheet (2). The coefficient of linear thermal expansion (CTE) was measured using a thermomechanical analyzer (product name "TMA / SS7100", manufactured by Hitachi High-Tech Science Co., Ltd.) with these test specimens. The measurement mode was tensile mode, the measurement load was 20-49 mN, the measurement atmosphere was atmospheric, and the heating rate was 10°C / min for the first run and 5°C / min for the second run. The measurement result at 40-55°C in the second run was designated as α1, and the measurement result at 110-160°C was designated as α2. The results are shown in Tables 4 and 5.

[0089] [Table 4]

[0090] [Table 5]

[0091] As is clear from Tables 4 and 5, the adhesive composition (Example) of this embodiment, which contains bismaleimide resin (A) and inorganic filler (B), and in which the content of inorganic filler (B) is within the range of 5 to 55% by mass (based on the total solid content of the adhesive composition), was confirmed to exhibit not only excellent low dielectric properties but also high adhesive strength to copper foil and polyimide film. Furthermore, the cured product obtained using the adhesive composition of the Example was confirmed to have low tack, a high 5% weight loss temperature, and low outgassing. Moreover, the cured product obtained using the adhesive composition of the Example was confirmed to have a reduced coefficient of thermal expansion (CTE). In Examples 14 to 19, dielectric properties were found to be as effective as in the other examples. [Industrial applicability]

[0092] The adhesive composition of the present invention not only exhibits excellent low dielectric properties in the high-frequency range, but also excellent adhesion to substrates such as copper foil and polyimide sheets. Furthermore, the cured product (adhesive layer) obtained from this adhesive composition has low tack, a high 5% weight loss temperature, low outgassing, and a low coefficient of linear expansion (CTE). Therefore, it is useful not only as an adhesive for the manufacture of printed circuit boards (build-up boards, flexible printed wiring boards, etc.) and copper-clad boards for flexible printed wiring boards, but also as an electrical insulating material such as a semiconductor interlayer material, coating agent, resist ink, and conductive paste.

Claims

1. The material comprises a bismaleimide resin (A) obtained by reacting aromatic tetracarboxylic acids (a1), dimer amine (a2), and maleic anhydride (a3), and an inorganic filler (B). The weight-average molecular weight of the bismaleimide resin (A) is 7,000 to 25,000. A bismaleimide-based adhesive composition in which the inorganic filler (B) content is 15 to 55% by mass based on the total solid content of the adhesive composition.

2. The bismaleimide adhesive composition according to claim 1, wherein the aromatic tetracarboxylic acid (a1) is pyromellitic anhydride or a compound represented by the following general formula (1). 【Chemistry 1】 [In formula (1), X represents a single bond or at least one group selected from the following group.] 【Chemistry 2】

3. The bismaleimide adhesive composition according to claim 1 or 2, wherein the dimeramine (a2) is a compound represented by the following general formula (2) and / or general formula (2'). 【Transformation 3】 【Chemistry 4】 [In equations (2) and (2'), m, n, p, and q represent integers of 1 or more selected such that m+n = 6 to 17 and p+q = 8 to 19, respectively. The dashed lines indicate carbon-carbon single bonds or carbon-carbon double bonds. However, if the dashed line indicates a carbon-carbon double bond, equations (2) and (2') will have a structure in which the number of hydrogen atoms bonded to each carbon atom constituting the carbon-carbon double bond is reduced by one from the number shown in equations (2) and (2').]

4. The bismaleimide adhesive composition according to any one of claims 1 to 3, wherein the inorganic filler is silica.

5. A bismaleimide adhesive composition according to any one of claims 1 to 4, further comprising a polymerization initiator (D).

6. The bismaleimide adhesive composition according to claim 5, wherein the polymerization initiator (D) is at least one selected from the group consisting of organic peroxides, imidazole compounds, phosphine compounds, and phosphonium salt compounds.

7. The bismaleimide adhesive composition according to claim 5, wherein the polymerization initiator (D) is at least one selected from the group consisting of imidazole compounds, phosphine compounds, and phosphonium salt compounds.

8. The bismaleimide adhesive composition according to any one of claims 1 to 7, wherein the average particle size of the inorganic filler (B) is 100 nm to 10 μm.

9. The bismaleimide adhesive composition according to any one of claims 1 to 8, wherein the average particle size of the inorganic filler (B) is 200 nm to 1.0 μm.

10. The bismaleimide adhesive composition according to any one of claims 1 to 9, wherein the content of the inorganic filler (B) is 15 to 25% by mass based on the total amount of solids in the adhesive composition.

11. A cured product obtained by curing a bismaleimide-based adhesive composition according to any one of claims 1 to 10.

12. An adhesive sheet obtained by applying the bismaleimide adhesive composition according to any one of claims 1 to 10 to a sheet substrate and drying it.

13. A laminate obtained by further heat-pressing a sheet substrate onto the adhesive surface of the adhesive sheet described in claim 12.

14. A laminate obtained by further heating the laminate described in claim 13.

15. A flexible printed circuit board made using the laminate described in claim 14.

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