Resin composition, prepreg, resin-bearing film, resin-bearing metal foil, metal-clad laminate sheet, and wiring board

Abstract

One aspect of the present invention is a resin composition containing a pre-reaction product (A) obtained by pre-reacting a mixture containing a polyfunctional vinyl aromatic copolymer (a1) containing a repeating unit derived from a divinyl aromatic compound and a maleimide compound (a2) having a C6 or higher alkyl group and a C6 of higher alkylene group.

Description

Resin composition, prepreg, resin-coated film, resin-coated metal foil, metal-clad laminate, and wiring board

[0001] The present invention relates to a resin composition, a prepreg, a resin-coated film, a resin-coated metal foil, a metal-clad laminate, and a wiring board.

[0002] As the amount of information processed increases, integration technologies for various electronic devices are advancing, such as higher integration of semiconductor devices, higher density wiring, and multi-layering. Furthermore, wiring boards used in various electronic devices are required to be high-frequency compatible, such as millimeter-wave radar boards for automotive applications. Substrate materials for forming insulating layers of wiring boards used in various electronic devices are required to have low relative permittivity and dielectric loss tangent in order to increase signal transmission speed and reduce loss during signal transmission. Examples of substrate materials for forming insulating layers of such wiring boards include resin compositions described in Patent Documents 1 and 2.

[0003] Patent Document 1 describes a curable resin composition containing a modified polyphenylene ether in which a hydroxyl group present at the end of the main chain is modified with a (meth)acrylic acid compound, and a polyfunctional vinyl aromatic copolymer containing a repeating unit derived from a divinyl aromatic compound and a repeating unit derived from a monovinyl aromatic compound. Patent Document 1 discloses that the composition can provide a cured product or molded article with improved heat resistance, compatibility, dielectric properties, moist heat reliability, and thermal oxidative degradation resistance.

[0004] Patent Document 2 describes a resin composition containing a maleimide compound having an isopropylidene group bonded to two aromatic carbon atoms of different aromatic rings, and a resin having a vinylphenyl group and / or a (meth)acryloyl group. Patent Document 2 discloses that the minimum melt viscosity can be reduced, and a cured product having a low dielectric loss tangent and excellent copper plating peel strength can be obtained.

[0005] Metal-clad laminates and resin-coated metal foils used in manufacturing wiring boards and the like have not only an insulating layer but also a metal foil on the insulating layer. Similarly, wiring boards also have not only an insulating layer but also wiring on the insulating layer. Examples of the wiring include wiring derived from the metal foil provided on the metal-clad laminates and resin-coated metal foils.

[0006] Electronic devices, particularly small portable devices such as mobile communication terminals and laptops, are rapidly becoming more diverse, more powerful, thinner, and smaller. Accordingly, the wiring boards used in these products are also required to have even finer conductor wiring, more multi-layered conductor wiring layers, thinner wiring, and improved mechanical properties. Therefore, even if the wiring provided on the wiring board is finer, it is required that the wiring does not peel off from the insulating layer. To meet this requirement, the wiring board is required to have high adhesion between the wiring and the insulating layer. Therefore, the metal-clad laminate is required to have high adhesion between the metal foil and the insulating layer, and the substrate material for constituting the insulating layer of the wiring board is required to produce a cured product with excellent adhesion to the metal foil.

[0007] When a resin composition containing multiple components is used as a substrate material for constituting an insulating layer of a wiring board, if the compatibility of each component in the cured product obtained by curing this resin composition is low, each component will not be uniformly dispersed in the insulating layer obtained from the resin composition. As a result, the effects of each component cannot be fully exerted, and problems such as reduced durability may occur. For this reason, in order to obtain a suitable insulating layer, it is also required that the substrate material for constituting the insulating layer of a wiring board be able to obtain a cured product with excellent compatibility.

[0008] JP 2018-168347 A International Publication No. 2022 / 102756

[0009] The present invention has been made in view of the above circumstances, and aims to provide a resin composition that can give a cured product having excellent compatibility and adhesion to metal foil while maintaining excellent low dielectric properties. The present invention also aims to provide a prepreg, a resin-coated film, a resin-coated metal foil, a metal-clad laminate, and a wiring board that can be obtained using the resin composition.

[0010] One aspect of the present invention is a resin composition comprising a pre-reactant (A) obtained by pre-reacting a mixture containing a polyfunctional vinyl aromatic copolymer (a1) containing a repeating unit derived from a divinyl aromatic compound and a maleimide compound (a2) having an alkyl group having 6 or more carbon atoms and an alkylene group having 6 or more carbon atoms.

[0011] These and other objects, features, and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.

[0012] Fig. 1 is a schematic cross-sectional view showing an example of a prepreg according to an embodiment of the present invention. Fig. 2 is a schematic cross-sectional view showing an example of a metal-clad laminate according to an embodiment of the present invention. Fig. 3 is a schematic cross-sectional view showing an example of a wiring board according to an embodiment of the present invention. Fig. 4 is a schematic cross-sectional view showing an example of a resin-coated metal foil according to an embodiment of the present invention. Fig. 5 is a schematic cross-sectional view showing an example of a resin-coated film according to an embodiment of the present invention.

[0013] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these.

[0014] As a result of extensive investigations, the present inventors have found that the above object can be achieved by the present invention described below.

[0015] [Resin Composition] The resin composition according to an embodiment of the present invention is a resin composition comprising a preliminary reaction product (A) obtained by preliminarily reacting a mixture containing a polyfunctional vinyl aromatic copolymer (a1) containing a repeating unit derived from a divinyl aromatic compound and a maleimide compound (a2) having an alkyl group having 6 or more carbon atoms and an alkylene group having 6 or more carbon atoms.

[0016] The present inventors have conducted extensive research to provide a resin composition that maintains excellent low dielectric properties while exhibiting excellent adhesion to metal foil. Specifically, the present inventors focused on the polyfunctional vinyl aromatic copolymer (a1) and found that the cured product obtained by curing the copolymer has excellent low dielectric properties and heat resistance. Furthermore, they found that when the polyfunctional vinyl aromatic copolymer (a1) is cured using a maleimide compound, the glass transition temperature of the resulting cured product is higher and heat resistance is improved compared to when a compound other than a maleimide compound, such as a modified polyphenylene ether compound, is used, as in the resin composition described in Patent Document 1. However, the present inventors' research has revealed that, depending on the type of maleimide compound used, adhesion to metal foil may not be sufficiently improved. Specifically, the inventors have found that using the maleimide compound (a2) as the maleimide compound used in combination with the polyfunctional vinyl aromatic copolymer (a1) can improve adhesion to metal foil compared to using a maleimide compound that does not have an aliphatic skeleton, such as an alkyl group having 6 or more carbon atoms and an alkylene group having 6 or more carbon atoms (e.g., the resin composition described in Patent Document 2). The inventors have reasoned that this is because the maleimide compound (a2) has an alkyl group having 6 or more carbon atoms and an alkylene group having 6 or more carbon atoms, and therefore has higher flexibility than maleimide compounds that do not have an aliphatic skeleton, such as the maleimide compound described in Patent Document 2. Therefore, they have found that by incorporating the maleimide compound (a2) into a resin composition, a cured product with high adhesion to metal foil can be obtained. Further investigation has led the inventors to find that simply using the maleimide compound (a2) as the maleimide compound used in combination with the polyfunctional vinyl aromatic copolymer (a1) may result in insufficient compatibility in the resulting cured product. Therefore, the present inventors have found that by incorporating a pre-reactant (A) obtained by pre-reacting a mixture containing the polyfunctional vinyl aromatic copolymer (a1) and the maleimide compound (a2) into a resin composition, a cured product having high compatibility such that phase separation between the polyfunctional vinyl aromatic copolymer (a1) and the maleimide compound (a2) can be suppressed in the cured product obtained by curing the resin composition.Furthermore, the cured product obtained by curing the polyfunctional vinyl aromatic copolymer (a1) tends to be brittle, whereas the cured product obtained by curing a preliminary reaction product (A) in which the polyfunctional vinyl aromatic copolymer (a1) is reacted with the highly flexible maleimide compound (a2) in advance can have improved adhesion to a metal foil.

[0017] From the above, when the resin composition is cured, a cured product having excellent compatibility and adhesion to metal foil is obtained while maintaining excellent low dielectric properties. Furthermore, high compatibility also enhances the dispersibility of the inorganic filler contained in the resin composition. Therefore, when an inorganic filler is contained in the resin composition, a cured product having excellent dispersibility of the inorganic filler is obtained. In addition, wiring boards used in various electronic devices are required to be resistant to changes in the external environment, etc. For example, excellent heat resistance is required so that the wiring board can be used even in relatively high-temperature environments. For this reason, substrate materials for constituting the insulating layer of wiring boards are required to produce cured products having excellent heat resistance, such as a high glass transition temperature. Furthermore, in order to obtain wiring boards with excellent reliability over a wide temperature range, substrate materials for constituting the insulating layer of wiring boards are required to produce cured products having a high glass transition temperature. The resin composition is a resin composition that maintains excellent low dielectric properties while producing cured products having excellent heat resistance, compatibility, and adhesion to metal foil, and further having excellent heat resistance. Furthermore, as described above, multilayering is required for wiring boards. When insulating layers are configured in multiple layers, high interlayer adhesion is also required to prevent delamination between insulating layers. For this reason, substrate materials for configuring the insulating layers of wiring boards are required to provide a cured product with excellent adhesion between adjacent cured products, i.e., excellent interlayer adhesion. The resin composition not only provides excellent adhesion to metal foil, but also provides a cured product with excellent interlayer adhesion. Therefore, the resin composition is a resin composition that provides a cured product with excellent heat resistance, compatibility, and adhesion to metal foil while maintaining excellent low dielectric properties, and further excellent interlayer adhesion and heat resistance.

[0018] (Preliminary Reactant (A)) The preliminary reactant (A) is not particularly limited as long as it is a preliminary reactant obtained by preliminarily reacting a mixture containing the polyfunctional vinyl aromatic copolymer (a1) and the maleimide compound (a2). The preliminary reactant (A), for example, may be a mixture of the polyfunctional vinyl aromatic copolymer (a1) and the maleimide compound (a2) preliminarily reacted with each other. Furthermore, a compound (other raw material) (a3) ​​capable of reacting with at least one of the polyfunctional vinyl aromatic copolymer (a1) and the maleimide compound (a2) may also be preliminarily reacted with each other. The resin composition is cured by curing the preliminary reactant (A). The mixture may contain the polyfunctional vinyl aromatic copolymer (a1) and the maleimide compound (a2), and may also contain the other raw material (a3). The resin composition may contain, as the preliminary reactant (A), for example, a reaction product obtained by pre-reacting the polyfunctional vinyl aromatic copolymer (a1) with the maleimide compound (a2), or may also contain a reaction product obtained by pre-reacting the polyfunctional vinyl aromatic copolymer (a1), the maleimide compound (a2), and the other raw material (a3). Furthermore, the resin composition may contain, as the preliminary reactant (A), a reaction product obtained by pre-reacting the polyfunctional vinyl aromatic copolymer (a1) with the maleimide compound (a2), or may contain the unreacted polyfunctional vinyl aromatic copolymer (a1), the unreacted maleimide compound (a2), or the unreacted other raw material (a3).

[0019] (Polyfunctional vinyl aromatic copolymer (a1)) The polyfunctional vinyl aromatic copolymer (a1) is not particularly limited as long as it is a polyfunctional vinyl aromatic copolymer containing a repeating unit (a1-1) derived from a divinylaromatic compound. Examples of the polyfunctional vinyl aromatic copolymer (a1) include a polyfunctional vinyl aromatic copolymer containing a repeating unit (a1-1) derived from the divinylaromatic compound and a repeating unit (a1-2) derived from a monovinyl aromatic compound. More specifically, the polyfunctional vinyl aromatic copolymer (a1) is a polyfunctional vinyl aromatic copolymer containing the repeating unit (a1-1) and the repeating unit (a1-2), wherein, when the sum of the repeating units (a1-1) and the repeating units (a1-2) is taken as 100 mol%, the repeating unit (a1-1) accounts for 2 mol% or more and less than 95 mol% and the repeating unit (a1-2) accounts for 5 mol% or more and less than 98 mol%, and the repeating unit (a1-1) derived from the divinylaromatic compound is represented by the following formula ( and soluble polyfunctional vinyl aromatic copolymers which contain a repeating unit (a1-1-1) having an unsaturated group represented by formula (1), wherein the molar fraction of the repeating unit (a1-1-1) in the total of the repeating units (a1-1) and (a1-2) satisfies the following formula (2), have a number average molecular weight of 300 to 100,000, a molecular weight distribution represented by the ratio of the weight average molecular weight to the number average molecular weight of 100.0 or less, and are soluble in toluene, xylene, tetrahydrofuran, dichloroethane, or chloroform. The soluble polyfunctional vinyl aromatic copolymers are also simply referred to as copolymers.

[0020] In formula (1), R １ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms.

[0021] 0.02≦(a1-1-1) / [(a1-1)+(a1-2)]≦0.8 (2) The soluble polyfunctional vinyl aromatic copolymer contains a repeating unit (a1-1) derived from the divinylaromatic compound and a repeating unit (a1-2) derived from the monovinyl aromatic compound, and further contains a repeating unit (a1-1-1) represented by the above formula (1) as a part of the repeating unit (a1-1) derived from the divinylaromatic compound.

[0022] The soluble polyfunctional vinyl aromatic copolymer contains the repeating unit (a1-1) in an amount of 2 mol % or more and less than 95 mol % and the repeating unit (a1-2) in an amount of 5 mol % or more and less than 98 mol % when the total of the repeating unit (a1-1) and the repeating unit (a1-2) is taken as 100 mol %, and contains the repeating unit (a1-1-1) in an amount of 2 to 80 mol % when the total of the repeating unit (a1-1) and the repeating unit (a1-2) is taken as 100 mol %.

[0023] The soluble polyfunctional vinyl aromatic copolymer has a number average molecular weight Mn of 300 to 100,000, a molecular weight distribution expressed as the ratio of the weight average molecular weight Mw to the number average molecular weight Mn (Mw / Mn) of 100.0 or less, and is soluble in toluene, xylene, tetrahydrofuran, dichloroethane, or chloroform.

[0024] The soluble polyfunctional vinyl aromatic copolymer is not limited, but examples thereof include copolymers containing structural units derived from a repeating unit (a1-2) derived from the monovinyl aromatic compound represented by the following formula (3) and a repeating unit (a1-1) derived from the divinyl aromatic compound represented by the following formula (4) and formula (5). These structural units may be arranged regularly or randomly.

[0025]

[0026]

[0027] In the formula (3), R ２represents an aromatic hydrocarbon group having 6 to 30 carbon atoms derived from the monovinyl aromatic compound, and in the formulas (4) and (5), R １ represents an aromatic hydrocarbon group having 6 to 30 carbon atoms derived from the divinyl aromatic compound, and in the formulas (3) to (5), h to k each independently represent an integer of 0 to 200, provided that the total of these is 2 to 20,000.

[0028] Suitable examples of the soluble polyfunctional vinyl aromatic copolymer include those represented by the formulas (3) to (5) above, where R １ and R ２ and copolymers comprising repeating units which are aromatic hydrocarbon groups selected from the group consisting of an optionally substituted phenyl group, an optionally substituted biphenyl group, an optionally substituted naphthalene group, and an optionally substituted terphenyl group.

[0029] The soluble polyfunctional vinyl aromatic copolymer is solvent-soluble. The repeating units referred to in this specification are derived from monomers and include units that are present in the main chain of the copolymer and appear repeatedly, as well as units or terminal groups present at the end or side chain. Repeating units are also referred to as structural units. The terminal groups referred to in this specification include terminal groups derived from the above-mentioned monomers as well as terminal groups derived from the chain transfer agent described below.

[0030] The structural unit (a1-1) derived from the divinylaromatic compound is contained in an amount of 2 mol% or more and less than 95 mol% of the total of the structural unit (a1-1) derived from the divinylaromatic compound and the structural unit (a1-2) derived from the monovinyl aromatic compound. The structural unit (a1-1) derived from the divinylaromatic compound can have a variety of structures, such as one in which only one of two vinyl groups has reacted, or two in which two have reacted. Among these, the repeating unit (a1-1-1) represented by formula (1) in which only one vinyl group has reacted is preferably contained in an amount of 2 to 80 mol%, more preferably 5 to 70 mol%, even more preferably 10 to 60%, and particularly preferably 15 to 50%, of the total. By containing 2 to 80 mol% of the repeating unit (a1-1-1) represented by formula (1) in which only one vinyl group has reacted, the composition has a low dielectric tangent, high toughness, excellent heat resistance, and excellent compatibility with other resins. Furthermore, when formed into a resin composition, it has excellent moist heat resistance, thermal oxidative degradation resistance, and moldability. If the repeating units (a1-1-1) in which only one vinyl group represented by the formula (1) has reacted are less than 2 mol% relative to the total, heat resistance tends to decrease. On the other hand, if the repeating units (a1-1-1) in which only one vinyl group represented by the formula (1) has reacted are more than 80 mol% relative to the total, interlayer peel strength tends to decrease when formed into a laminate.

[0031] The soluble polyfunctional vinyl aromatic copolymer contains the structural unit (a1-2) derived from the monovinyl aromatic compound in an amount of 5 mol% or more and less than 98 mol%, preferably 10 mol% or more and less than 90 mol%, and more preferably 15 mol% or more and less than 85 mol%, based on the total amount. If the structural unit (a1-2) derived from the monovinyl aromatic compound is less than 5 mol% based on the total amount, molding processability tends to be insufficient. On the other hand, if the structural unit (a1-2) derived from the monovinyl aromatic compound is more than 98 mol% based on the total amount, the heat resistance of the cured product tends to be insufficient.

[0032] The vinyl group present in the formula (a1-1-1) acts as a cross-linking component and contributes to the development of heat resistance in the soluble polyfunctional vinyl aromatic copolymer. On the other hand, the structural unit (a1-2) derived from the monovinyl aromatic compound does not have a vinyl group because polymerization is generally believed to proceed via a 1,2-addition reaction of the vinyl group. In other words, the structural unit (a1-2) derived from the monovinyl aromatic compound does not act as a cross-linking component but contributes to the development of moldability.

[0033] Styrene is a preferred example of the monovinyl aromatic compound. Furthermore, as the monovinyl aromatic compound, a monovinyl aromatic compound other than styrene can also be used together with styrene. In this case, the content of the structural unit (a1-2-1) derived from styrene is preferably 99 to 20 mol%, more preferably 98 to 30 mol%, when the sum of the contents of the structural unit (a1-2-1) derived from styrene and the structural unit (a1-2-2) derived from a monovinyl aromatic compound other than styrene is taken as 100 mol%. A content of the structural unit (a1-2-1) derived from styrene within the above range is preferred because it combines thermal oxidative degradation resistance and moldability. When the structural unit (b1) derived from styrene is greater than 99 mol% of the total, heat resistance tends to decrease. Furthermore, when the structural unit (a1-2-2) derived from a monovinyl aromatic compound other than styrene is greater than 80 mol% of the total [when the structural unit (a1-2-1) derived from styrene is less than 20 mol% of the total], moldability tends to decrease.

[0034] The number-average molecular weight Mn of the soluble polyfunctional vinyl aromatic copolymer (measured using GPC in terms of standard polystyrene) is preferably 300 to 100,000, more preferably 400 to 50,000, and even more preferably 500 to 10,000. If the number-average molecular weight Mn of the soluble polyfunctional vinyl aromatic copolymer is less than 300, the amount of monofunctional copolymer components contained in the soluble polyfunctional vinyl aromatic copolymer increases, which tends to reduce the heat resistance of the cured product. If the number-average molecular weight Mn of the soluble polyfunctional vinyl aromatic copolymer exceeds 100,000, gel formation becomes more likely and the viscosity increases, which tends to reduce moldability.

[0035] The molecular weight distribution (Mw / Mn) of the soluble polyfunctional vinyl aromatic copolymer, expressed as the ratio of the weight average molecular weight Mw (weight average molecular weight Mw measured using GPC in terms of standard polystyrene) to the number average molecular weight Mn, is 100.0 or less, preferably 50.0 or less, more preferably 1.5 to 30.0, and even more preferably 2.0 to 20.0. If Mw / Mn exceeds 100.0, the processability of the soluble polyfunctional vinyl aromatic copolymer tends to deteriorate, and gel tends to form.

[0036] The soluble polyfunctional vinyl aromatic copolymer is soluble in toluene, xylene, tetrahydrofuran, dichloroethane or chloroform as a solvent, and is preferably soluble in any of the above-mentioned solvents.To be a solvent-soluble polyfunctional copolymer, it is necessary that a part of the vinyl group of divinylbenzene remains uncrosslinked and has an appropriate degree of crosslinking.Here, soluble in a solvent means that the soluble polyfunctional vinyl aromatic copolymer dissolves in 100g of the solvent in an amount of 5g or more, preferably 30g or more, more preferably 50g or more.

[0037] The divinyl aromatic compound serves to form a branched structure to impart multifunctionality, and also serves as a cross-linking component to impart heat resistance when the resulting soluble multifunctional vinyl aromatic copolymer is thermally cured.

[0038] The divinyl aromatic compound is not particularly limited as long as it is an aromatic compound having two vinyl groups, but for example, divinylbenzene (including each positional isomer or a mixture thereof), divinylnaphthalene (including each positional isomer or a mixture thereof), and divinylbiphenyl (including each positional isomer or a mixture thereof) are preferably used. These may be used alone or in combination of two or more. From the viewpoint of moldability, the divinyl aromatic compound is more preferably divinylbenzene (m-isomer, p-isomer, or a mixture of these positional isomers).

[0039] The monovinyl aromatic compound includes, for example, styrene and monovinyl aromatic compounds other than styrene. As the monovinyl aromatic compound, it is desirable to use styrene as an essential component and to use the monovinyl aromatic compound other than styrene in combination.

[0040] Styrene, as a monomer component, serves to impart low dielectric properties and thermal oxidative degradation resistance to the soluble polyfunctional vinyl aromatic copolymer, and also serves as a chain transfer agent to control the molecular weight of the soluble polyfunctional vinyl aromatic copolymer.

[0041] The monovinyl aromatic compound other than styrene improves the solvent solubility and processability of the soluble polyfunctional vinyl aromatic copolymer.

[0042] The monovinyl aromatic compound other than styrene is not particularly limited as long as it is an aromatic compound other than styrene having one vinyl group, but examples thereof include vinyl aromatic compounds such as vinylnaphthalene and vinylbiphenyl; and nuclear alkyl-substituted vinyl aromatic compounds such as o-methylstyrene, m-methylstyrene, p-methylstyrene, o,p-dimethylstyrene, o-ethylvinylbenzene, m-ethylvinylbenzene, and p-ethylvinylbenzene. The monovinyl aromatic compound other than styrene is preferably ethylvinylbenzene (including each positional isomer or a mixture thereof), ethylvinylbiphenyl (including each positional isomer or a mixture thereof), or ethylvinylnaphthalene (including each positional isomer or a mixture thereof) because they prevent gelation of the soluble polyfunctional vinyl aromatic copolymer, are highly effective in improving solvent solubility and processability, are low cost, and are easily available. The monovinyl aromatic compound other than styrene is preferably ethylvinylbenzene (m-isomer, p-isomer, or a mixture of these positional isomers) from the viewpoints of dielectric properties and cost.

[0043] In addition to the divinyl aromatic compound and the monovinyl aromatic compound, one or more other monomer components such as a trivinyl aromatic compound, a trivinyl aliphatic compound, a divinyl aliphatic compound, and a monovinyl aliphatic compound may be used, and structural units (a1-3) derived from these may be introduced into the soluble polyfunctional vinyl aromatic copolymer, provided that the effects of the present invention are not impaired.

[0044] Examples of the other monomer components include 1,3,5-trivinylbenzene, 1,3,5-trivinylnaphthalene, 1,2,4-trivinylcyclohexane, ethylene glycol diacrylate, butadiene, 1,4-butanediol divinyl ether, cyclohexanedimethanol divinyl ether, diethylene glycol divinyl ether, and triallyl isocyanurate. These can be used alone or in combination of two or more.

[0045] The molar fraction of the other monomer component relative to the sum of all monomer components is preferably less than 30 mol %. That is, the molar fraction of the repeating unit (a1-3) derived from the other monomer component relative to the sum of all monomer components constituting the soluble polyfunctional vinyl aromatic copolymer (the sum of the structural unit (a1-1), the structural unit (a1-2), and the structural unit (a1-3)) is preferably less than 30 mol %.

[0046] The soluble polyfunctional vinyl aromatic copolymer can be obtained by polymerizing a monomer containing the divinyl aromatic compound and the monovinyl aromatic compound in the presence of a Lewis acid catalyst. Furthermore, a known chain transfer agent (CTR) can be added during the polymerization to control the molecular weight.

[0047] (Maleimide Compound (a2)) The maleimide compound (a2) is not particularly limited as long as it is a maleimide compound having an alkyl group having 6 or more carbon atoms and an alkylene group having 6 or more carbon atoms. The maleimide compound (a2) preferably further has an alicyclic hydrocarbon group in the molecule. Note that the maleimide compound (a2) has not only an alkyl group having 6 or more carbon atoms and an alkylene group having 6 or more carbon atoms but also a maleimide group in the molecule.

[0048] The weight-average molecular weight Mw of the maleimide compound (a2) is not particularly limited, but is preferably 500 to 4000, and more preferably 500 to 1000. When the weight-average molecular weight Mw of the maleimide compound (a2) is within the above range, the resin composition has excellent reactivity with the polyfunctional vinyl aromatic copolymer (a1) and also has low dielectric properties, allowing for the production of an excellent cured product. Here, the weight-average molecular weight Mw may be measured by a general molecular weight measurement method, and specific examples include values ​​measured using gel permeation chromatography (GPC).

[0049] Examples of the maleimide compound (a2) include maleimide compounds in which an alkyl group having 6 or more carbon atoms and an alkylene group having 6 or more carbon atoms to which the maleimide group is bonded are bonded to the alicyclic hydrocarbon group. Examples of the maleimide compound (a2) include maleimide compounds represented by the following formula (6) and maleimide compounds represented by the following formula (7). Note that in the maleimide compound represented by the following formula (6) and the maleimide compound represented by the following formula (7), the alkylene group is a group bonded to the maleimide group and the alicyclic hydrocarbon group, and the alkyl group is a group bonded to the alicyclic hydrocarbon group without having a maleimide group bonded to it.

[0050] In formula (6), R １ represents an alkyl group having 6 or more carbon atoms. ２ represents an alkylene group having 6 or more carbon atoms. １ represents an alicyclic hydrocarbon group. １ b represents the degree of substitution of the group represented by [ ] in formula (6).

[0051] In formula (7), R ３ and R ４ R each independently represents an alkyl group having 6 or more carbon atoms. ５ ~R ７ each independently represents an alkylene group having 6 or more carbon atoms. ２ and Cy ３ each independently represents an alicyclic hydrocarbon group. ３ d indicates the degree of substitution of R ４ n indicates the number of repeating units.

[0052] a, b, c, and d each represent the degree of substitution. Specifically, a represents the degree of substitution of R １and, for example, from the viewpoint of further improving adhesion to a metal foil, it is preferably 0 to 4, and more preferably 0 to 2. As described above, b represents the degree of substitution of the group represented by [ ] in formula (6), and, for example, from the viewpoint of further improving adhesion to a metal foil, it is preferably 1 to 5, and more preferably 1 to 3. As described above, c represents the degree of substitution of R ３ For example, from the viewpoint of further improving the adhesion to the metal foil, it is preferably 0 to 4, and more preferably 0 to 2. As described above, d is the degree of substitution of R ４ For example, from the viewpoint of further enhancing adhesion to the metal foil, it is preferably 0 to 4, and more preferably 0 to 2.

[0053] n represents the number of repeating units of the repeating unit represented by [ ] in formula (7), and examples thereof include the number of repeating units such that the weight-average molecular weight Mw of the maleimide compound (a1) falls within the above-mentioned range. n is, for example, preferably 1 to 10, and more preferably 1 to 2, from the viewpoint of further improving adhesion to the metal foil.

[0054] The alkyl group is not particularly limited as long as it has 6 or more carbon atoms, and may be linear or branched, but is preferably linear. The number of carbon atoms in the alkyl group is 6 or more, preferably 6 to 20, and more preferably 6 to 12. When the number of carbon atoms is within the above range, the effects of the maleimide compound (a2) (e.g., the effect of improving adhesion to a metal foil) can be fully exhibited. Examples of the alkyl group include a hexyl group, an ethylhexyl group, a heptyl group, a methylheptyl group, an octyl group, a methyloctyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, a tridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, and an icosyl group. Among these, a hexyl group and an octyl group are preferred as the alkyl group.

[0055] The alkylene group is not particularly limited as long as it has 6 or more carbon atoms, and may be linear or branched, but is preferably linear. The number of carbon atoms in the alkylene group is 6 or more, preferably 6 to 20, and more preferably 6 to 12. When the number of carbon atoms is within the above range, the effects of the maleimide compound (a2) (e.g., the effect of improving adhesion to a metal foil) can be fully exhibited. Examples of the alkylene group include a hexylene group, an ethylhexylene group, a heptylene group, a methylheptylene group, an octylene group, a methyloctylene group, a nonylene group, a decylene group, an undecylene group, a dodecylene group, a tridecylene group, a tetradecylene group, a pentadecylene group, a hexadecylene group, a heptadecylene group, an octadecylene group, a nonadecylene group, and an icosylene group. Among these, an octylene group is preferred as the alkylene group.

[0056] The alicyclic hydrocarbon group is not particularly limited, and examples thereof include divalent or higher alicyclic hydrocarbon groups that bond the alkyl groups having 6 or more carbon atoms and the alkylene groups having 6 or more carbon atoms. The alicyclic hydrocarbon group is preferably, for example, an alicyclic hydrocarbon group having 6 to 24 carbon atoms, and more preferably an alicyclic hydrocarbon group having 6 to 12 carbon atoms. Furthermore, as described above, the alicyclic hydrocarbon group is preferably, for example, a divalent or higher alicyclic hydrocarbon group, and more preferably a tetravalent to hexavalent alicyclic hydrocarbon group. When such an alicyclic hydrocarbon group is further contained in the molecule [the maleimide compound (a2)], the effects of the maleimide compound (a2) (e.g., the effect of improving adhesion to a metal foil) can be fully exhibited. Examples of the alicyclic hydrocarbon group include cycloalkane groups (divalent or higher valent cycloalkane groups), and more specific examples include cyclopropane group, cyclobutane group, cyclopentane group, cyclohexane group, cycloheptane group, cyclooctane, cyclononane, cyclodecane, cycloundecane, cyclododecane, cyclotridecane, cyclotetradecane, cyclopentadecane, cyclohexadecane, cycloheptadecane, cyclooctadecane, cyclononadecane, and cycloicosane.

[0057] The maleimide compound (a2) contains at least one maleimide group in the molecule. The number of maleimide groups per molecule of the maleimide compound (a2) is 1 or more, and preferably 2 to 3.

[0058] Specific examples of the maleimide compound (a2) include a maleimide compound represented by the following formula (8) and a maleimide compound represented by the following formula (9). An example of the maleimide compound represented by the following formula (8) is BMI-689 manufactured by Designer Molecules Inc. An example of the maleimide compound represented by the following formula (9) is BMI-3000J manufactured by Designer Molecules Inc.

[0059]

[0060] In formula (9), n represents 1 to 10.

[0061] (Catalyst) A catalyst may be used in the reaction between the polyfunctional vinyl aromatic copolymer (a1) and the maleimide compound (a2). The catalyst is not particularly limited as long as it contributes to the progress of the reaction, and examples thereof include peroxides and azo compounds. Examples of the peroxide include organic peroxides such as α,α'-di(t-butylperoxy)diisopropylbenzene (PBP), 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne, benzoyl peroxide, 3,3',5,5'-tetramethyl-1,4-diphenoquinone, chloranil, 2,4,6-tri-t-butylphenoxyl, and t-butylperoxyisopropyl monocarbonate. Examples of the azo compound include organic azo compounds such as azobisisobutyronitrile, 2,2'-azobis(2,4,4-trimethylpentane), 2,2'-azobis(N-butyl-2-methylpropionamide), and 2,2'-azobis(2-methylbutyronitrile).

[0062] (Reactant) The resin composition according to this embodiment includes, as the preliminary reactant (A), a reactant obtained by reacting the polyfunctional vinyl aromatic copolymer (a1) with the maleimide compound (a2). Examples of the reactant include a reactant obtained by reacting the vinyl group of the polyfunctional vinyl aromatic copolymer (a1) with the maleimide group of the maleimide compound (a2). Examples of the reaction include radical copolymerization of the polyfunctional vinyl aromatic copolymer (a1) with the maleimide compound (a2).

[0063] The mass ratio of the polyfunctional vinyl aromatic copolymer (a1) to the maleimide compound (a2) is preferably 10:90 to 90:10, more preferably 70:30 to 90:10. The equivalent ratio of the maleimide group of the maleimide compound (a2) to the vinyl group of the polyfunctional vinyl aromatic copolymer (a1) (maleimide group of the maleimide compound (a2) / vinyl group of the polyfunctional vinyl aromatic copolymer (a1)) is preferably 1 to 7, more preferably 1 to 3. If the amount of the polyfunctional vinyl aromatic copolymer (a1) is too large, i.e., if the amount of the maleimide compound (a2) is too small, adhesion to the metal foil tends to decrease. If the amount of the polyfunctional vinyl aromatic copolymer (a1) is too small, i.e., if the amount of the maleimide compound (a2) is too large, heat resistance, such as a lowered glass transition temperature, tends to decrease. In addition, if the amount of the polyfunctional vinyl aromatic copolymer (a1) is too much or if the amount of the maleimide compound (a2) is too much, the compatibility tends to decrease. This is thought to be due to the fact that the reaction between the polyfunctional vinyl aromatic copolymer (a1) and the maleimide compound (a2) becomes difficult. Therefore, if the mass ratio is within the above range, the resin composition can be obtained with a cured product that has excellent low dielectric properties, heat resistance, compatibility, and adhesion to metal foil.

[0064] The weight average molecular weight Mw of the reaction product is the weight average molecular weight Mw of the reaction product obtained by reacting the polyfunctional vinyl aromatic copolymer (a1) with the maleimide compound (a2), and is, for example, preferably 25,000 to 95,000, and more preferably 30,000 to 50,000. Note that the weight average molecular weight Mw may be measured by a general molecular weight measurement method, and specific examples include values ​​measured using gel permeation chromatography (GPC).

[0065] The reaction conditions are not particularly limited as long as the reaction proceeds. For example, the reaction conditions are preferably such that the reaction rate is 30% or more, i.e., 30 to 100%. The reaction conditions can also be adjusted by sampling the reaction product over time while carrying out a preliminary reaction and checking the reaction rate.

[0066] Examples of the reaction rate include the rate of change of compounds having molecular weights that are present in the polyfunctional vinyl aromatic copolymer (a1) and the maleimide compound before the reaction but are not present in the compound (reactant) after the reaction. Specific examples of the reaction rate include the reaction rate at an elapsed time t from the start of the reaction, which is represented by the following formula. That is, the reaction rate at an elapsed time t from the start of the reaction can be exemplified by the ratio of the GPC area S(t) corresponding to the amount of compounds having a molecular weight of 600 to 1450 at the elapsed time t from the start of the reaction to the difference between the GPC area S(t) corresponding to the amount of compounds having a molecular weight of 600 to 1450 before the start of the reaction and the GPC area S(0) corresponding to the amount of compounds having a molecular weight of 600 to 1450 before the start of the reaction.

[0067] Reaction rate (%) = [(S(0) - S(t)) / S(0) × 100] As described above, the reaction conditions include conditions that result in a reaction rate of 30% or more. More specifically, the temperature during the reaction (reaction temperature) is preferably 80 to 110°C, and more preferably 90 to 100°C. If the reaction temperature is too low, the reaction tends to proceed slowly. If the reaction temperature is too high, polymerization between the preliminary reactants tends to proceed more easily, and the reaction between the polyfunctional vinyl aromatic copolymer (a1) and the maleimide compound (a2) tends to proceed slowly. Therefore, when the reaction temperature is within the above range, the polyfunctional vinyl aromatic copolymer (a1) and the maleimide compound (a2) can be reacted efficiently. Furthermore, the time for which the reaction is carried out (reaction time) is preferably 180 to 900 minutes, and more preferably 360 to 600 minutes. If the reaction time is too short, the reaction tends to proceed slowly. If the reaction time is too long, gelation may occur. Therefore, when the reaction time is within the above range, the reaction between the polyfunctional vinyl aromatic copolymer (a1) and the maleimide compound (a2) can proceed efficiently.

[0068] (Reactive Compound (B)) The resin composition according to this embodiment may further contain a reactive compound (B), and preferably contains the reactive compound (B). The reactive compound (B) is not particularly limited as long as it is a compound that reacts with the preliminary reactant (A). Examples of the reactive compound (B) include allyl compounds, methacrylate compounds, acrylate compounds, acenaphthylene compounds, vinyl compounds, isocyanurate compounds, polyphenylene ether compounds having a carbon-carbon unsaturated double bond in the molecule, and maleimide compounds other than the maleimide compound (a1).

[0069] The allyl compound is a compound having an allyl group in the molecule, and examples of the allyl compound include diallyl bisphenol compounds and diallyl phthalate (DAP).

[0070] The methacrylate compound is a compound having a methacryloyl group in the molecule. Examples of the methacrylate compound include a monofunctional methacrylate compound having one methacryloyl group in the molecule and a polyfunctional methacrylate compound having two or more methacryloyl groups in the molecule. Examples of the monofunctional methacrylate compound include methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate. Examples of the polyfunctional methacrylate compound include a dimethacrylate compound such as tricyclodecane dimethanol dimethacrylate (DCP).

[0071] The acrylate compound is a compound having an acryloyl group in the molecule. Examples of the acrylate compound include a monofunctional acrylate compound having one acryloyl group in the molecule and a polyfunctional acrylate compound having two or more acryloyl groups in the molecule. Examples of the monofunctional acrylate compound include methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate. Examples of the polyfunctional acrylate compound include a diacrylate compound such as tricyclodecane dimethanol diacrylate.

[0072] The acenaphthylene compound is a compound having an acenaphthylene structure in the molecule. Examples of the acenaphthylene compound include acenaphthylene, alkylacenaphthylenes, halogenated acenaphthylenes, and phenylacenaphthylenes. Examples of the alkylacenaphthylenes include 1-methylacenaphthylene, 3-methylacenaphthylene, 4-methylacenaphthylene, 5-methylacenaphthylene, 1-ethylacenaphthylene, 3-ethylacenaphthylene, 4-ethylacenaphthylene, and 5-ethylacenaphthylene. Examples of the halogenated acenaphthylenes include 1-chloroacenaphthylene, 3-chloroacenaphthylene, 4-chloroacenaphthylene, 5-chloroacenaphthylene, 1-bromoacenaphthylene, 3-bromoacenaphthylene, 4-bromoacenaphthylene, and 5-bromoacenaphthylene. Examples of the phenylacenaphthylenes include 1-phenylacenaphthylene, 3-phenylacenaphthylene, 4-phenylacenaphthylene, and 5-phenylacenaphthylene. The acenaphthylene compound may be a monofunctional acenaphthylene compound having one acenaphthylene structure in the molecule, as described above, or a polyfunctional acenaphthylene compound having two or more acenaphthylene structures in the molecule.

[0073] The vinyl compound is a compound having a vinyl group in its molecule. Examples of the vinyl compound include monofunctional vinyl compounds having one vinyl group in its molecule and polyfunctional vinyl compounds having two or more vinyl groups in its molecule. Examples of the monofunctional vinyl compound include vinylbenzene compounds having a phosphorus atom-containing skeleton in its molecule, such as 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). Examples of the polyfunctional vinyl compound include divinylbenzene and polybutadiene compounds. Examples of the polybutadiene compound include polybutadiene and hydrogenated styrene-butadiene copolymers, and more specifically, B-1000, B-2000, and B-3000 manufactured by Nippon Soda Co., Ltd., and Ricon manufactured by Cray Valley Chemical Industries, Ltd.

[0074] The isocyanurate compound is a compound having an isocyanurate structure in the molecule, and examples of the isocyanurate compound include trialkenyl isocyanurate compounds such as triallyl isocyanurate (TAIC).

[0075] The polyphenylene ether compound is not particularly limited as long as it is a polyphenylene ether compound having a carbon-carbon unsaturated double bond in the molecule. Examples of the polyphenylene ether compound include polyphenylene ether compounds having a carbon-carbon unsaturated double bond at a terminal, and more specifically, polyphenylene ether compounds having a substituent having a carbon-carbon unsaturated double bond at a molecular terminal, such as modified polyphenylene ether compounds whose terminals are modified with a substituent having a carbon-carbon unsaturated double bond. Examples of the substituent having a carbon-carbon unsaturated double bond include a vinylbenzyl group (ethenylbenzyl group), an acryloyl group, and a methacryloyl group.

[0076] The maleimide compound is not particularly limited as long as it is a maleimide compound other than the maleimide compound (a1). Examples of the maleimide compound include monofunctional maleimide compounds having one maleimide group in the molecule and polyfunctional maleimide compounds having two or more maleimide groups in the molecule. Examples of the modified maleimide compound include modified maleimide compounds in which a portion of the molecule is amine-modified, modified maleimide compounds in which a portion of the molecule is silicone-modified, and modified maleimide compounds in which a portion of the molecule is both amine-modified and silicone-modified.

[0077] Among the above, the curing agent is preferably, for example, the acenaphthylene compound or the polyphenylene ether compound, and more preferably, acenaphthylene or a polyphenylene ether compound having a methacryloyl group at the molecular end. The curing agent may be used alone or in combination of two or more. As the curing agent, it is preferable to use the acenaphthylene compound and the polyphenylene ether compound in combination, and more preferably, acenaphthylene and a polyphenylene ether compound having a methacryloyl group at the molecular end.

[0078] (Content) The content of the pre-reacted product (A) is preferably 30% by mass or more, and more preferably 60% by mass or more, based on the total mass of the pre-reacted product (A) and the curing agent (B). The resin composition may contain the pre-reacted product (A), but may or may not contain the curing agent (B). Therefore, the content of the pre-reacted product (A) may be 100% by mass, and is preferably 90% by mass or less, based on the total mass of the pre-reacted product (A) and the curing agent (B). Therefore, the content of the pre-reacted product (A) is preferably 30 to 100% by mass, and more preferably 60 to 90% by mass, based on the total mass of the pre-reacted product (A) and the curing agent (B).

[0079] (Inorganic filler) The resin composition according to the present embodiment may contain an inorganic filler as needed, as long as the effects of the present invention are not impaired. In addition, it is preferable to contain the inorganic filler in order to improve the heat resistance of the cured product of the resin composition. The inorganic filler is not particularly limited as long as it can be used as an inorganic filler contained in the resin composition. Examples of the inorganic filler include silica filler, alumina filler, titanium oxide filler, magnesium oxide filler and mica filler, metal hydroxide filler such as magnesium hydroxide filler and aluminum hydroxide filler, talc filler, aluminum borate filler, barium sulfate filler, aluminum nitride filler, boron nitride filler, barium titanate filler, strontium titanate filler, calcium titanate filler, aluminum titanate filler, magnesium carbonate filler such as anhydrous magnesium carbonate filler, calcium carbonate filler, molybdic acid compound filler such as zinc molybdate filler and calcium molybdate filler, and talc filler carrying the molybdic acid compound.Among these, silica filler, metal hydroxide filler such as magnesium hydroxide filler and aluminum hydroxide filler, aluminum oxide filler, boron nitride filler, strontium titanate filler, calcium titanate filler and zinc molybdate filler are preferred, and silica filler is more preferred. The silica filler is not particularly limited, and for example, crushed silica, spherical silica, silica particles, etc. can be mentioned, and spherical silica is preferred.As the inorganic filler, each of the exemplified inorganic fillers can be used alone, or two or more can be used in combination.When two or more of the inorganic fillers are used in combination, silica filler can be used in combination with one or more inorganic fillers other than silica filler, and it is preferred to use silica filler in combination with zinc molybdate filler.

[0080] The inorganic filler may be a surface-treated or untreated inorganic filler. Examples of the surface treatment include treatment with a silane coupling agent.

[0081] The silane coupling agent is not particularly limited, and examples thereof include silane coupling agents having at least one functional group selected from the group consisting of vinyl group, styryl group, methacryloyl group, acryloyl group, phenylamino group, isocyanurate group, ureido group, mercapto group, isocyanate group, epoxy group, and acid anhydride group. That is, the silane coupling agent has at least one reactive functional group selected from vinyl group, styryl group, methacryloyl group, acryloyl group, phenylamino group, isocyanurate group, ureido group, mercapto group, isocyanate group, epoxy group, and acid anhydride group, and further includes compounds having a hydrolyzable group such as a methoxy group or an ethoxy group.

[0082] Examples of the silane coupling agent include those having a vinyl group, such as vinyltriethoxysilane and vinyltrimethoxysilane. Examples of the silane coupling agent include those having a styryl group, such as p-styryltrimethoxysilane and p-styryltriethoxysilane. Examples of the silane coupling agent include those having a methacryloyl group, such as 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, and 3-methacryloxypropylethyldiethoxysilane. Examples of the silane coupling agent include those having an acryloyl group, such as 3-acryloxypropyltrimethoxysilane and 3-acryloxypropyltriethoxysilane. Examples of the silane coupling agent include those having a phenylamino group, such as N-phenyl-3-aminopropyltrimethoxysilane and N-phenyl-3-aminopropyltriethoxysilane.

[0083] The average particle size of the inorganic filler is not particularly limited, and is preferably 0.05 to 10 μm, and more preferably 0.1 to 8 μm. Here, the average particle size refers to the volume average particle size. The volume average particle size can be measured, for example, by a laser diffraction method.

[0084] When the inorganic filler is contained, the content thereof is preferably 40 to 120 parts by mass, and more preferably 50 to 100 parts by mass, relative to 100 parts by mass of the total mass of the preliminary reaction product (A) and the curing agent (B).

[0085] (Flame Retardant) The resin composition according to this embodiment may contain a flame retardant, if necessary, as long as the effects of the present invention are not impaired. The inclusion of a flame retardant can enhance the flame retardancy of the cured resin composition, so it is preferable to include the flame retardant. The flame retardant is not particularly limited. In fields where halogen-based flame retardants such as bromine-based flame retardants are used, preferred flame retardants include, for example, ethylene dipentabromobenzene, ethylene bistetrabromoimide, decabromodiphenyl oxide, tetradecabromodiphenoxybenzene, and bromostyrene-based compounds that react with the polymerizable compound, all of which have a melting point of 300°C or higher. It is believed that the use of a halogen-based flame retardant can suppress halogen elimination at high temperatures and thus prevent a decrease in heat resistance. Furthermore, in fields where halogen-free flame retardants are required, it is preferable to use a phosphorus-containing flame retardant (phosphorus-based flame retardant). The phosphorus-based flame retardant is not particularly limited as long as it contains phosphorus and can exhibit flame retardancy, and examples thereof include compatible phosphorus-based flame retardants that are compatible with the mixture of the preliminary reaction product (A) and the curing agent (B), and incompatible phosphorus-based flame retardants that are not compatible with the mixture.

[0086] The compatible phosphorus-based flame retardant is not particularly limited as long as it is compatible with the mixture. In this case, "compatible" refers to being finely dispersed in the mixture, for example, at the molecular level. Examples of compatible phosphorus flame retardants include phosphate ester flame retardants, phosphazene flame retardants, phosphite ester flame retardants, and phosphine flame retardants. Examples of phosphate ester flame retardants include triphenyl phosphate, tricresyl phosphate, xylenyl diphenyl phosphate, cresyl diphenyl phosphate, 1,3-phenylenebis(di-2,6-xylenyl phosphate), 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) flame retardants, condensed phosphate ester compounds such as aromatic condensed phosphate ester compounds, and cyclic phosphate ester compounds. Specific examples of the DOPO-based flame retardant include hydrocarbons having two DOPO groups in the molecule (DOPO derivative compounds) and DOPO having a reactive functional group. Examples of the phosphazene-based flame retardant include cyclic or chain phosphazene compounds, specifically xylylenebisdiphenylphosphine oxide. Cyclic phosphazene compounds, also known as cyclophosphazenes, are compounds having a double bond between phosphorus and nitrogen in the molecule and a cyclic structure. Examples of the phosphite-based flame retardant include trimethyl phosphite and triethyl phosphite. Examples of the phosphine-based flame retardant include tris-(4-methoxyphenyl)phosphine and triphenylphosphine. The compatible phosphorus-based flame retardants may be used alone or in combination of two or more.

[0087] The incompatible phosphorus-based flame retardant is not particularly limited as long as it is compatible with the mixture. In this case, compatibility refers to the incompatibility within the mixture, with the target substance (phosphorus-based flame retardant) dispersed in the mixture like islands. Examples of the incompatible phosphorus-based flame retardant include phosphinate-based flame retardants, polyphosphate-based flame retardants, phosphonium salt-based flame retardants, and phosphine oxide-based flame retardants. Examples of the phosphinate-based flame retardants include aluminum dialkylphosphinate, aluminum trisdiethylphosphinate, aluminum trismethylethylphosphinate, aluminum trisdiphenylphosphinate, zinc bisdiethylphosphinate, zinc bismethylethylphosphinate, zinc bisdiphenylphosphinate, titanyl bisdiethylphosphinate, titanyl bismethylethylphosphinate, and titanyl bisdiphenylphosphinate. Examples of the polyphosphate-based flame retardants include melamine polyphosphate, melam polyphosphate, and melem polyphosphate. Examples of the phosphonium salt-based flame retardants include tetraphenylphosphonium tetraphenylborate and tetraphenylphosphonium bromide. Examples of the phosphine oxide-based flame retardants include phosphine oxide compounds having two or more diphenylphosphine oxide groups in the molecule (diphenylphosphine oxide compounds). The incompatible phosphorus-based flame retardants may be used alone or in combination of two or more.

[0088] The flame retardant may be used alone or in combination of two or more thereof. As the flame retardant, it is preferable to use the compatible phosphorus-based flame retardant and the incompatible phosphorus-based flame retardant in combination, and it is more preferable to use an aromatic condensed phosphate ester compound and a diphenylphosphine oxide compound in combination.

[0089] When the flame retardant is contained, the content thereof is preferably 10 to 60 parts by mass, and more preferably 20 to 50 parts by mass, relative to 100 parts by mass of the total mass of the preliminary reaction product (A) and the curing agent (B).

[0090] (Reaction Initiator) The resin composition according to this embodiment may contain a reaction initiator as needed, provided that the effects of the present invention are not impaired. The curing reaction of the resin composition may proceed even without a reaction initiator. On the other hand, depending on the process conditions, it may be difficult to raise the temperature high enough for curing to proceed, so a reaction initiator may be added. The reaction initiator is not particularly limited as long as it can accelerate the curing reaction of the resin composition. Examples of the reaction initiator include peroxides and azo compounds. Examples of the peroxide include organic peroxides such as α,α'-di(t-butylperoxy)diisopropylbenzene (PBP), 2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne, benzoyl peroxide, 3,3',5,5'-tetramethyl-1,4-diphenoquinone, chloranil, 2,4,6-tri-t-butylphenoxyl, and t-butylperoxyisopropyl monocarbonate. Examples of the azo compound include organic azo compounds such as azobisisobutyronitrile, 2,2'-azobis(2,4,4-trimethylpentane), 2,2'-azobis(N-butyl-2-methylpropionamide), and 2,2'-azobis(2-methylbutyronitrile). The reaction initiator may be used alone or in combination of two or more. It is preferable to use the peroxide and the azo compound in combination as the reaction initiator. If necessary, a metal carboxylate or the like can also be used in combination. This can further accelerate the curing reaction. Among these, α,α'-di(t-butylperoxy)diisopropylbenzene and 2,2'-azobis(2,4,4-trimethylpentane) are preferred as the reaction initiator. Because α,α'-di(t-butylperoxy)diisopropylbenzene has a relatively high reaction initiation temperature, it is possible to suppress the acceleration of the curing reaction when curing is not necessary, such as during prepreg drying, and it is possible to suppress a decrease in the shelf life of the resin composition. Furthermore, because α,α'-di(t-butylperoxy)diisopropylbenzene has low volatility, it does not volatilize during prepreg drying or storage, and therefore has good stability.

[0091] When the reaction initiator is contained, the content thereof is preferably 0.1 to 2 parts by mass, and more preferably 0.5 to 1.5 parts by mass, relative to 100 parts by mass of the total mass of the preliminary reactant (A) and the curing agent (B).

[0092] (Free Radical Compound) The resin composition according to the present embodiment may contain a free radical compound as needed, as long as the effects of the present invention are not impaired. The free radical compound is a compound having a free radical group in its molecule, and is a compound different from the polyfunctional vinyl aromatic copolymer (a1), the maleimide compound (a2), and the curing agent (B). The free radical compound can delay the radical reaction by capturing radicals with the free radical group in its molecule, thereby slowing down the curing reaction of the resin composition. Examples of the free radical compound include a free radical compound having a 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) structure in its molecule. Specific examples of the free radical compound include 4-amino-2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 4-acetamido-2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 4-amino-2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 4-carboxy-2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 4-cyano-2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 4-glycidyloxy-2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxylbenzoate free radical, and 4-isothiocyanato-2,2,6,6-tetramethylpiperidine 1-oxyl Free radical, 4-(2-iodoacetamido)-2,2,6,6-tetramethylpiperidine 1-oxyl Free radical, 4-[2-[2-(4-iodophenoxy)ethoxy]carbonyl]benzoyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl Free radical, 4-methoxy-2,2,6,6-tetramethylpiperidine 1-oxyl Free radical, 4-methacryloyloxy-2,2,6,6-tetramethylpiperidine 1-oxyl Free radical, 4-oxo-2,2,6,6-Tetramethylpiperidine 1-oxyl free radical, 4-oxo-2,2,6,6-tetraethylpiperidine 1-oxyl free radical, 2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 2,2,6,6-tetramethyl-4-(2-propynyloxy)piperidine 1-oxyl free radical, 2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 4,5-dihydro-4,4,5,5-tetramethyl-2-phenyl-1H-imidazol-1-yloxy-1-oxide free radical, bis(2,2,6,6-tetramethyl-4-piperidyl-1-oxyl) sebacate free radical, 3-carboxy-2,2,5,5-tetramethylpyrrolidine 1-oxyl free radical, 4-(2-chloroacetamido)-2,2,6,6-tetramethylpiperidine 1-oxyl Examples of the free radical compound include 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl free radical, 2-(4-nitrophenyl)-4,4,5,5-tetramethylimidazoline-3-oxide-1-oxyl free radical, 2-(14-carboxytetradecyl)-2-ethyl-4,4-dimethyl-3-oxazolidinyloxy free radical, and 1,1-diphenyl-2-picrylhydrazyl free radical. Of these, 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl free radical is preferred. The free radical compounds may be used alone or in combination of two or more. Commercially available free radical compounds may be used, and examples of commercially available free radical compounds include LA-7RD manufactured by ADEKA Corporation.

[0093] When the free radical compound is contained, the content thereof is preferably 0.001 to 0.1 parts by mass, and more preferably 0.001 to 0.05 parts by mass, relative to 100 parts by mass of the total mass of the preliminary reactant (A) and the curing agent (B).

[0094] (Silane Coupling Agent) The resin composition according to this embodiment may contain a silane coupling agent, if necessary, as long as the effects of the present invention are not impaired. The silane coupling agent may be contained in the resin composition, or may be contained as a silane coupling agent that has been surface-treated in advance on an inorganic filler contained in the resin composition. Among these, the silane coupling agent is preferably contained as a silane coupling agent that has been surface-treated in advance on an inorganic filler, and it is more preferable to contain the silane coupling agent in advance on an inorganic filler in this way, and further to contain the silane coupling agent in the resin composition. In addition, in the case of a prepreg, the prepreg may contain the silane coupling agent that has been surface-treated in advance on a fibrous substrate. Examples of the silane coupling agent include the same silane coupling agents as those used when surface-treating the inorganic filler described above.

[0095] When the silane coupling agent is contained, the content thereof is preferably 0.1 to 2 parts by mass, and more preferably 0.3 to 1.2 parts by mass, relative to 100 parts by mass of the total mass of the preliminary reaction product (A) and the curing agent (B).

[0096] (Other Components) The resin composition according to this embodiment may contain components (other components) other than the pre-reactant (A) and the curing agent (B) as long as the effects of the present invention are not impaired. As described above, the resin composition may contain the flame retardant, the reaction initiator, the free radical compound, the silane coupling agent, and the inorganic filler as the other components. Examples of the other components include, in addition to the inorganic filler, organic components other than the pre-reactant (A) and the curing agent (B), curing accelerators, catalysts, polymerization retarders, polymerization inhibitors, dispersants, leveling agents, antifoaming agents, antioxidants, heat stabilizers, antistatic agents, UV absorbers, dyes and pigments, and additives such as lubricants.

[0097] As described above, the resin composition according to the present embodiment may contain an organic component other than the pre-reactant (A) and the curing agent (B). The organic component may be, for example, a compound that reacts with either the pre-reactant (A) or the curing agent (B), or a compound that does not react with either the pre-reactant (A) or the curing agent (B). Specific examples of the organic component include oxazine compounds, epoxy compounds, cyanate ester compounds, and active ester compounds.

[0098] The oxazine compound is not particularly limited as long as it is a compound having an oxazine group in the molecule. Examples of the oxazine compound include benzoxazine compounds having a phenolphthalein structure in the molecule (phenolphthalein-type benzoxazine compounds), bisphenol F-type benzoxazine compounds, and diaminodiphenylmethane (DDM)-type benzoxazine compounds. More specific examples of the oxazine compound include 3,3'-(methylene-1,4-diphenylene)bis(3,4-dihydro-2H-1,3-benzoxazine) (P-d-type benzoxazine compound) and 2,2-bis(3,4-dihydro-2H-3-phenyl-1,3-benzoxazine)methane (F-a-type benzoxazine compound).

[0099] The epoxy compound is a compound having an epoxy group in the molecule, and specific examples thereof include bisphenol-type epoxy compounds such as bisphenol A-type epoxy compounds, phenol novolac-type epoxy compounds, cresol novolac-type epoxy compounds, dicyclopentadiene-type epoxy compounds, bisphenol A novolac-type epoxy compounds, biphenyl aralkyl-type epoxy compounds, polybutadiene compounds having an epoxy group in the molecule, and naphthalene ring-containing epoxy compounds. The epoxy compound also includes epoxy resins, which are polymers of the above-mentioned epoxy compounds.

[0100] The cyanate ester compound is a compound having a cyanate group in the molecule, and examples thereof include 2,2-bis(4-cyanatephenyl)propane, bis(3,5-dimethyl-4-cyanatephenyl)methane, and 2,2-bis(4-cyanatephenyl)ethane.

[0101] The active ester compound is a compound having an ester group with high reactivity in the molecule, and examples thereof include benzenecarboxylic acid active ester, benzenedicarboxylic acid active ester, benzenetricarboxylic acid active ester, benzenetetracarboxylic acid active ester, naphthalenecarboxylic acid active ester, naphthalenedicarboxylic acid active ester, naphthalenetricarboxylic acid active ester, naphthalenetetracarboxylic acid active ester, fluorenecarboxylic acid active ester, fluorenedicarboxylic acid active ester, fluorenetricarboxylic acid active ester, and fluorenetetracarboxylic acid active ester.

[0102] As described above, the resin composition according to this embodiment may contain a curing accelerator. The curing accelerator is not particularly limited as long as it can accelerate the curing reaction of the resin composition. Specific examples of the curing accelerator include imidazoles and their derivatives, organophosphorus compounds, amines such as secondary amines and tertiary amines, quaternary ammonium salts, organoboron compounds, and metal soaps. Examples of the imidazoles include 2-ethyl-4-methylimidazole (2E4MZ), 2-methylimidazole, 2-phenyl-4-methylimidazole, 2-phenylimidazole, and 1-benzyl-2-methylimidazole. Examples of the organophosphorus compounds include triphenylphosphine, diphenylphosphine, phenylphosphine, tributylphosphine, and trimethylphosphine. Examples of the amines include dimethylbenzylamine, triethylenediamine, triethanolamine, and 1,8-diaza-bicyclo(5,4,0)undecene-7 (DBU). Examples of the quaternary ammonium salts include tetrabutylammonium bromide. Examples of the organoboron compounds include tetraphenylboron salts such as 2-ethyl-4-methylimidazole tetraphenylborate, and tetra-substituted phosphonium tetra-substituted borates such as tetraphenylphosphonium ethyltriphenylborate. The metal soap refers to a fatty acid metal salt, and may be either a linear fatty acid metal salt or a cyclic fatty acid metal salt. Specific examples of the metal soap include linear fatty acid metal salts and cyclic fatty acid metal salts having 6 to 10 carbon atoms. More specifically, examples of the curing accelerator include aliphatic metal salts composed of linear fatty acids such as stearic acid, lauric acid, ricinoleic acid, and octylic acid, or cyclic fatty acids such as naphthenic acid, and metals such as lithium, magnesium, calcium, barium, copper, and zinc. For example, zinc octylate is included. The curing accelerators may be used alone or in combination of two or more.

[0103] The resin composition according to the present embodiment is a resin composition that can give a cured product having excellent compatibility and adhesion to metal foil while maintaining excellent low dielectric properties. The resin composition also gives a cured product having excellent heat resistance, compatibility, and adhesion to metal foil while maintaining excellent low dielectric properties, and also excellent interlayer adhesion and heat resistance.

[0104] (Uses) The resin composition according to the present embodiment is used to produce a prepreg, as described below, and is also used to form a resin layer provided in a resin-coated metal foil or resin-coated film, and an insulating layer provided in a metal-clad laminate or wiring board.

[0105] (Production Method) The method for producing the resin composition according to the present embodiment is not particularly limited, and examples thereof include a method of mixing the preliminary reaction product (A), and, if necessary, the curing agent (B), and the other components to a predetermined content, etc. In addition, in the case of obtaining a varnish-like composition containing an organic solvent, the method described below, etc. can be used.

[0106] By using the resin composition according to this embodiment, a prepreg, a metal-clad laminate, a wiring board, a resin-coated metal foil, and a resin-coated film can be obtained as follows.

[0107] [Prepreg] FIG. 1 is a schematic cross-sectional view showing an example of a prepreg 1 according to an embodiment of the present invention.

[0108] 1, the prepreg 1 according to this embodiment comprises the resin composition or a semi-cured product of the resin composition 2, and a fibrous base material 3. This prepreg 1 comprises the resin composition or a semi-cured product of the resin composition 2, and the fibrous base material 3 present in the resin composition or the semi-cured product of the resin composition 2.

[0109] In this embodiment, the semi-cured product refers to a resin composition that has been partially cured to the extent that it can be further cured. That is, the semi-cured product refers to a resin composition that has been semi-cured (B-staged). For example, when a resin composition is heated, the viscosity initially gradually decreases, and then curing begins, and the viscosity gradually increases. In such a case, the semi-cured state may refer to a state between when the viscosity starts to increase and when the composition is completely cured.

[0110] The prepreg obtained using the resin composition according to this embodiment may comprise a semi-cured product of the resin composition as described above, or may comprise the uncured resin composition itself. That is, it may be a prepreg comprising a semi-cured product of the resin composition (the resin composition in B stage) and a fibrous base material, or a prepreg comprising the resin composition before curing (the resin composition in A stage) and a fibrous base material. Furthermore, the resin composition or the semi-cured product of the resin composition may be the resin composition that has been dried or heat-dried.

[0111] When producing the prepreg, the resin composition 2 is often prepared in a varnish form and used to impregnate the fibrous base material 3, which is a base material for forming the prepreg. That is, the resin composition 2 is usually often a resin varnish prepared in a varnish form. Such a varnish-like resin composition (resin varnish) is prepared, for example, as follows.

[0112] First, each component that is soluble in an organic solvent is added to the organic solvent and dissolved. Heating may be performed as necessary. Then, components that are insoluble in the organic solvent are added as needed, and the mixture is dispersed using a ball mill, bead mill, planetary mixer, roll mill, or the like until a predetermined dispersion state is achieved, thereby preparing a varnish-like resin composition. The organic solvent used here is not particularly limited as long as it dissolves the organic components and resin components in the resin composition and does not inhibit the curing reaction. Specific examples include toluene and methyl ethyl ketone (MEK).

[0113] Specific examples of the fibrous substrate include glass cloth, aramid cloth, polyester cloth, glass nonwoven fabric, aramid nonwoven fabric, polyester nonwoven fabric, pulp paper, and linter paper. Glass cloth can be used to obtain a laminate with excellent mechanical strength, and flattened glass cloth is particularly preferred. A specific example of the flattening process is a method in which glass cloth is continuously pressed with a press roll at an appropriate pressure to compress the yarns flat. The thickness of commonly used fibrous substrates is, for example, 0.01 mm or more and 0.3 mm or less. The glass fibers constituting the glass cloth are not particularly limited, and examples include Q glass, NE glass, E glass, S glass, T glass, L glass, and L2 glass. The surface of the fibrous substrate may be treated with a silane coupling agent. The silane coupling agent is not particularly limited, but examples thereof include silane coupling agents having at least one group selected from the group consisting of a vinyl group, an acryloyl group, a methacryloyl group, a styryl group, an amino group, and an epoxy group in the molecule.

[0114] The method for producing the prepreg is not particularly limited as long as it can produce the prepreg. Specifically, when producing the prepreg, the resin composition according to the present embodiment is often prepared in the form of a varnish, as described above, and used as a resin varnish.

[0115] Specific examples of methods for producing the prepreg 1 include a method in which the resin composition 2, for example, a resin composition 2 prepared in a varnish form, is impregnated into a fibrous substrate 3, followed by drying. The resin composition 2 is impregnated into the fibrous substrate 3 by immersion, coating, or the like. Impregnation can be repeated multiple times as necessary. In this case, by repeating the impregnation using multiple resin compositions with different compositions and concentrations, it is also possible to adjust the final composition and impregnation amount to the desired one.

[0116] The fibrous substrate 3 impregnated with the resin composition (resin varnish) 2 is heated under desired conditions, for example, at 40°C to 180°C for 1 minute to 10 minutes. This heating process results in a prepreg 1 in an uncured (A-stage) or semi-cured (B-stage) state. The heating process also volatilizes the organic solvent from the resin varnish, reducing or eliminating the organic solvent.

[0117] [Metal-clad laminate] FIG. 2 is a schematic cross-sectional view showing an example of a metal-clad laminate 11 according to an embodiment of the present invention.

[0118] As shown in FIG. 2 , the metal-clad laminate 11 according to this embodiment includes an insulating layer 12 containing a cured product of the resin composition and a metal foil 13 disposed on the insulating layer 12. Examples of the metal-clad laminate 11 include a metal-clad laminate composed of an insulating layer 12 containing a cured product of the prepreg 1 shown in FIG. 1 and a metal foil 13 laminated together with the insulating layer 12. The insulating layer 12 may be composed of a cured product of the resin composition or a cured product of the prepreg. The thickness of the metal foil 13 varies depending on the performance required of the final wiring board and is not particularly limited. The thickness of the metal foil 13 can be appropriately set depending on the desired purpose, and is preferably, for example, 0.2 to 70 μm. Examples of the metal foil 13 include copper foil and aluminum foil. When the metal foil is thin, it may be a carrier-attached copper foil equipped with a release layer and a carrier to improve handling.

[0119] The method for producing the metal-clad laminate 11 is not particularly limited as long as it can produce the metal-clad laminate 11. Specifically, a method for producing the metal-clad laminate 11 using the prepreg 1 can be used. Examples of such a method include stacking one or more prepregs 1, placing a metal foil 13 such as copper foil on both sides or one side of the prepreg 1, and then heat-pressing and molding the metal foil 13 and the prepreg 1 to form an integrated laminate. That is, the metal-clad laminate 11 can be obtained by laminating the metal foil 13 on the prepreg 1 and then heat-pressing and molding the laminate. The heat-pressing conditions can be appropriately set depending on the thickness of the metal-clad laminate 11, the type of resin composition contained in the prepreg 1, and other factors. For example, the temperature can be 170 to 230°C, the pressure can be 2 to 5 MPa, and the time can be 60 to 150 minutes. The metal-clad laminate can also be produced without using a prepreg. For example, a method may be used in which a varnish-like resin composition is applied onto a metal foil to form a layer containing the resin composition on the metal foil, and then the layer is heated and pressed.

[0120] [Wiring Board] FIG. 3 is a schematic cross-sectional view showing an example of a wiring board 21 according to an embodiment of the present invention.

[0121] As shown in Fig. 3, wiring board 21 according to this embodiment has insulating layer 12 containing a cured product of the resin composition, and wiring 14 provided on insulating layer 12. Examples of wiring board 21 include a wiring board configured from insulating layer 12 used by curing prepreg 1 shown in Fig. 1, and wiring 14 laminated together with insulating layer 12 and formed by partially removing metal foil 13. Furthermore, insulating layer 12 may be made of a cured product of the resin composition, or may be made of a cured product of the prepreg.

[0122] The method for manufacturing the wiring board 21 is not particularly limited as long as the wiring board 21 can be manufactured. Specific examples include a method of manufacturing the wiring board 21 using the prepreg 1. Examples of this method include a method of manufacturing the wiring board 21 in which wiring is provided as a circuit on the surface of the insulating layer 12 by etching the metal foil 13 on the surface of the metal-clad laminate 11 manufactured as described above. That is, the wiring board 21 is obtained by forming a circuit by partially removing the metal foil 13 on the surface of the metal-clad laminate 11. In addition to the above methods, examples of the method for forming a circuit include circuit formation by a semi-additive process (SAP) or a modified semi-additive process (MSAP).

[0123] [Resin-Coated Metal Foil] FIG. 4 is a schematic cross-sectional view showing an example of a resin-coated metal foil 31 according to this embodiment.

[0124] As shown in Fig. 4, the resin-coated metal foil 31 according to this embodiment comprises a resin layer 32 containing the resin composition or a semi-cured product of the resin composition, and a metal foil 13. The resin-coated metal foil 31 has the metal foil 13 on the surface of the resin layer 32. That is, the resin-coated metal foil 31 comprises the resin layer 32 and the metal foil 13 laminated together with the resin layer 32. The resin-coated metal foil 31 may also comprise another layer between the resin layer 32 and the metal foil 13.

[0125] The resin layer 32 may contain a semi-cured product of the resin composition as described above, or may contain the uncured resin composition. That is, the resin-coated metal foil 31 may comprise a resin layer containing a semi-cured product of the resin composition (the resin composition in B-stage) and a metal foil, or a resin layer containing the resin composition before curing (the resin composition in A-stage) and a metal foil. The resin layer may contain the resin composition or a semi-cured product of the resin composition, and may or may not contain a fibrous substrate. The resin composition or the semi-cured product of the resin composition may be the resin composition that has been dried or heat-dried. The fibrous substrate may be the same as the fibrous substrate of a prepreg.

[0126] The metal foil may be any metal foil used in a metal-clad laminate or a resin-coated metal foil, and examples of the metal foil include copper foil and aluminum foil.

[0127] The resin-coated metal foil 31 may be provided with a cover film or the like as necessary. By providing a cover film, it is possible to prevent the inclusion of foreign matter, etc. The cover film is not particularly limited, but examples thereof include polyolefin films, polyester films, polymethylpentene films, and films formed by providing these films with a release agent layer.

[0128] The method for producing the resin-coated metal foil 31 is not particularly limited as long as the resin-coated metal foil 31 can be produced. Examples of the method for producing the resin-coated metal foil 31 include a method of applying the varnish-like resin composition (resin varnish) to the metal foil 13 and heating the applied resin composition. The varnish-like resin composition is applied to the metal foil 13 using, for example, a bar coater. The applied resin composition is heated, for example, at 40°C or higher and 180°C or lower for 0.1 minutes or longer and 10 minutes or shorter. The heated resin composition is formed on the metal foil 13 as an uncured resin layer 32. The heating volatilizes the organic solvent from the resin varnish, thereby reducing or removing the organic solvent.

[0129] [Resin-Coated Film] FIG. 5 is a schematic cross-sectional view showing an example of a resin-coated film 41 according to this embodiment.

[0130] 5 , the resin-coated film 41 according to this embodiment includes a resin layer 42 containing the resin composition or a semi-cured product of the resin composition, and a support film 43. The resin-coated film 41 includes the resin layer 42 and the support film 43 laminated together with the resin layer 42. The resin-coated film 41 may also include another layer between the resin layer 42 and the support film 43.

[0131] The resin layer 42 may contain a semi-cured product of the resin composition as described above, or may contain the uncured resin composition. That is, the resin-coated film 41 may comprise a resin layer containing a semi-cured product of the resin composition (the resin composition in B-stage) and a support film, or a resin-coated film comprising a resin layer containing the resin composition before curing (the resin composition in A-stage) and a support film. The resin layer may contain the resin composition or a semi-cured product of the resin composition, and may or may not contain a fibrous substrate. The resin composition or the semi-cured product of the resin composition may be obtained by drying or heat-drying the resin composition. The fibrous substrate may be the same as the fibrous substrate of a prepreg.

[0132] Any support film used for a resin-coated film can be used without limitation as the support film 43. Examples of the support film include electrically insulating films such as polyester film, polyethylene terephthalate (PET) film, polyimide film, polyparabanic acid film, polyether ether ketone film, polyphenylene sulfide film, polyamide film, polycarbonate film, and polyarylate film.

[0133] The resin-coated film 41 may be provided with a cover film or the like as necessary. By providing a cover film, it is possible to prevent the inclusion of foreign matter, etc. The cover film is not particularly limited, but examples thereof include a polyolefin film, a polyester film, and a polymethylpentene film.

[0134] The support film and the cover film may be subjected to surface treatment such as matte treatment, corona treatment, release treatment, and roughening treatment, if necessary.

[0135] The method for producing the resin-coated film 41 is not particularly limited as long as it can produce the resin-coated film 41. Examples of methods for producing the resin-coated film 41 include a method in which the varnish-like resin composition (resin varnish) is applied to a support film 43 and heated. The varnish-like resin composition is applied to the support film 43 using, for example, a bar coater. The applied resin composition is heated, for example, at 40°C or higher and 180°C or lower for 0.1 minutes or longer and 10 minutes or shorter. The heated resin composition is formed on the support film 43 as an uncured resin layer 42. The heating volatilizes the organic solvent from the resin varnish, thereby reducing or removing the organic solvent.

[0136] The resin composition according to this embodiment is a resin composition that can provide a cured product that has excellent compatibility and adhesion to metal foil while maintaining excellent low dielectric properties. That is, when the resin composition is cured, a cured product that has excellent compatibility and adhesion to metal foil while maintaining excellent low dielectric properties is obtained. Therefore, when the prepreg is cured, a cured product that has excellent compatibility and adhesion to metal foil while maintaining excellent low dielectric properties is obtained. The resin-coated metal foil and resin-coated film are resin-coated metal foils and resin-coated films that include a resin layer that provides an insulating layer containing a cured product that has excellent compatibility and adhesion to metal foil while maintaining excellent low dielectric properties. The metal-clad laminate and wiring board are metal-clad laminates and wiring boards that include an insulating layer containing a cured product that has excellent compatibility and adhesion to metal foil while maintaining excellent low dielectric properties. The prepreg, the resin-coated metal foil, the resin-coated film, and the metal-clad laminate can be suitably used to manufacture a wiring board having an insulating layer containing a cured product that has excellent compatibility and adhesion to metal foil while maintaining excellent low dielectric properties. The prepreg, the resin-coated metal foil, the resin-coated film, and the metal-clad laminate can also be used to manufacture, for example, a multilayer wiring board. The resin-coated film can be manufactured, for example, by laminating it on a wiring board and then peeling off the support film, or by laminating it on a wiring board after peeling off the support film. The resin-coated metal foil can be manufactured, for example, by laminating it on a wiring board. In this way, by using the resin-coated film and the resin-coated metal foil, etc., a multilayer wiring board can be manufactured having an insulating layer containing a cured product that has excellent compatibility and adhesion to metal foil while maintaining excellent low dielectric properties. The wiring board obtained using the prepreg, the resin-coated metal foil, the resin-coated film, and the metal-clad laminate has an insulating layer containing a cured product that has excellent compatibility and adhesion to the metal foil while maintaining excellent low dielectric properties.

[0137] As described above, this specification discloses various aspects of the technology, the main technologies of which are summarized below.

[0138] The resin composition according to the first aspect of the present invention is a resin composition comprising a pre-reactant (A) obtained by reacting a polyfunctional vinyl aromatic copolymer (a1) containing a repeating unit derived from a divinyl aromatic compound with a maleimide compound (a2) having an alkyl group having 6 or more carbon atoms and an alkylene group having 6 or more carbon atoms.

[0139] A resin composition according to a second aspect of the present invention is a resin composition according to the first aspect of the present invention, wherein the polyfunctional vinyl aromatic copolymer further contains a repeating unit derived from a monovinyl aromatic compound.

[0140] A resin composition according to a third aspect of the present invention is the resin composition according to the first or second aspect of the present invention, wherein the mass ratio of the polyfunctional vinyl aromatic copolymer (a1) to the maleimide compound (a2) is 10:90 to 90:10.

[0141] A resin composition according to a fourth aspect of the present invention is the resin composition according to any one of the first to third aspects of the present invention, wherein the maleimide compound (a2) has a weight average molecular weight of 500 to 4,000.

[0142] A resin composition according to a fifth aspect of the present invention is the resin composition according to any one of the first to fourth aspects of the present invention, further comprising an inorganic filler.

[0143] A resin composition according to a sixth aspect of the present invention is the resin composition according to any one of the first to fifth aspects of the present invention, further comprising a flame retardant.

[0144] A resin composition according to a seventh aspect of the present invention is the resin composition according to any one of the first to sixth aspects of the present invention, further comprising a reactive compound (B) that reacts with the preliminary reactant (A), wherein the reactive compound (B) comprises at least one selected from the group consisting of allyl compounds, methacrylate compounds, acrylate compounds, acenaphthylene compounds, vinyl compounds, isocyanurate compounds, polyphenylene ether compounds having a carbon-carbon unsaturated double bond in the molecule, and maleimide compounds other than the maleimide compound (a2).

[0145] A prepreg according to an eighth aspect of the present invention is a prepreg comprising the resin composition according to any one of the first to seventh aspects of the present invention or a semi-cured product of the resin composition, and a fibrous base material.

[0146] The resin-coated film according to the ninth aspect of the present invention is a resin-coated film comprising a resin layer containing the resin composition according to any one of the first to seventh aspects of the present invention or a semi-cured product of the resin composition, and a support film.

[0147] A resin-coated metal foil according to a tenth aspect of the present invention is a resin-coated metal foil comprising a resin layer containing the resin composition according to any one of the first to seventh aspects of the present invention or a semi-cured product of the resin composition, and a metal foil.

[0148] A metal-clad laminate according to an eleventh aspect of the present invention is a metal-clad laminate comprising an insulating layer containing a cured product of the resin composition according to any one of the first to seventh aspects of the present invention, and a metal foil.

[0149] A metal-clad laminate according to a twelfth aspect of the present invention is a metal-clad laminate comprising an insulating layer containing a cured product of the prepreg according to the eighth aspect of the present invention and a metal foil.

[0150] A wiring board according to a thirteenth aspect of the present invention is a wiring board comprising an insulating layer containing a cured product of the resin composition according to any one of the first to seventh aspects of the present invention, and wiring.

[0151] A wiring board according to a fourteenth aspect of the present invention is a wiring board comprising an insulating layer containing a cured product of the prepreg according to the eighth aspect of the present invention and wiring.

[0152] According to the present invention, there is provided a resin composition that can give a cured product having excellent compatibility and adhesion to metal foil while maintaining excellent low dielectric properties. Furthermore, according to the present invention, there are provided a prepreg, a resin-coated film, a resin-coated metal foil, a metal-clad laminate, and a wiring board that can be obtained using the resin composition.

[0153] The present invention will be explained in more detail below with reference to examples, but the scope of the present invention is not limited to these examples.

[0154] Examples 1 to 3 and Comparative Examples 1 to 3 In these examples, each component used in preparing the resin composition will be described.

[0155] (Preliminary Reactant (A)) Preliminary Reactant 1: A preliminary reactant obtained by reacting a mixture containing the polyfunctional vinyl aromatic copolymer (a1) and the maleimide compound (a2) in advance. Specifically, the preliminary reactant 1 is a preliminary reactant obtained by the following reaction.

[0156] Each component used in producing the pre-reactant 1 will be described below.

[0157] Polyfunctional vinyl aromatic copolymer: The polyfunctional vinyl aromatic copolymer (a1) is specifically a polyfunctional vinyl aromatic copolymer obtained by the following reaction.

[0158] 2.25 mol (292.9 g) of divinylbenzene, 1.32 mol (172.0 g) of ethylvinylbenzene, 11.43 mol (1190.3 g) of styrene, and 15.0 mol (1532.0 g) of n-propyl acetate were charged into a 5.0 L reactor, and 600 mmol of a boron trifluoride diethyl ether complex was added at 70 °C, followed by a reaction for 4 hours. Thereafter, to terminate the reaction, an aqueous sodium bicarbonate solution was added to the resulting reaction solution, and the oil layer was washed three times with pure water. The mixture was then subjected to vacuum degassing at 60 °C, and the solid was recovered. The resulting solid was weighed, confirming that 860.8 g was obtained.

[0159] The molecular weight and molecular weight distribution of the obtained solid (polymer) were measured using GPC (HLC-8120GPC manufactured by Tosoh Corporation) with tetrahydrofuran as a solvent, a flow rate of 1.0 ml / min, a column temperature of 38°C, and a calibration curve with monodisperse polystyrene. As a result, the number average molecular weight Mn of the obtained solid was 2060, the weight average molecular weight Mw was 3070, and Mw / Mn was 14.9.

[0160] The structure of the obtained solid (polymer) was analyzed using a JNM-LA600 nuclear magnetic resonance spectrometer manufactured by JEOL Ltd. １３ C-NMR and １ The measurement was carried out by H-NMR analysis.１ was used, and the resonance line of tetramethylsilane was used as an internal standard. １３ C-NMR and １ The amount of a specific structural unit introduced was calculated from the data on the total amount of each structural unit introduced into the copolymer obtained by GC analysis in addition to the H-NMR measurement results, and the amount of pendant vinyl group units contained in the polyfunctional vinyl aromatic copolymer was calculated from the amount of the specific structural unit introduced at the terminal and the number average molecular weight obtained by the GPC measurement.

[0161] The resulting solid was subjected to the above-mentioned １３ C-NMR and １ By performing H-NMR analysis, resonance lines derived from each monomer unit were observed. Furthermore, based on the results of NMR measurement and GC analysis, it was found that this solid was the polyfunctional vinyl aromatic copolymer. Based on the results of NMR measurement and GC analysis, the constituent units of this polyfunctional vinyl aromatic copolymer were calculated as follows: 20.9 mol % (24.3 wt %) of structural units (a1-1) derived from divinylbenzene, 70.0 mol % (65.0 wt %) of structural units (a1-2) derived from styrene, 9.1 mol % (10.7 wt %) of structural units (a1-3) derived from ethylvinylbenzene, and 16.7 mol % (18.5 wt %) of structural units (a1-1-1) having residual vinyl groups derived from divinylbenzene.

[0162] Maleimide compound 1: the maleimide compound (a2) [BMI-689 manufactured by Designer Molecules Inc., a maleimide compound represented by the formula (8)]. 44.8 parts by mass of the polyfunctional vinyl aromatic copolymer and 5 parts by mass of the maleimide compound 1 were blended and diluted with toluene to a solids concentration of 50% by mass. This was stirred and mixed in a disper at a liquid temperature of 100°C for 8 hours. Volatiles were recovered each time using a cooler. By doing so, the polyfunctional vinyl aromatic copolymer and the maleimide compound 1 reacted to obtain a preliminary reaction product 1. The reaction rate was 60%.

[0163] Preliminary reactant 2: a preliminary reactant obtained by reacting a mixture containing the polyfunctional vinyl aromatic copolymer (a1) and the maleimide compound (a2) in advance. Specifically, the preliminary reactant 2 is a preliminary reactant obtained by the following reaction.

[0164] Preliminary reaction product 2 was obtained in the same manner as Preliminary reaction product 1, except that the amount of the polyfunctional vinyl aromatic copolymer was changed from 44.8 parts by mass to 42.4 parts by mass and the amount of the maleimide compound 1 was changed from 5 parts by mass to 10 parts by mass. The reaction rate was 50%.

[0165] Preliminary reactant 3: a preliminary reactant obtained by reacting in advance a mixture containing the polyfunctional vinyl aromatic copolymer (a1) and a maleimide compound other than the maleimide compound (a2). Specifically, the preliminary reactant 3 is a preliminary reactant obtained by the following reaction.

[0166] Preliminary reaction product 3 was obtained in the same manner as in the preparation of Preliminary reaction product 2, except that maleimide compound 2 (a maleimide compound not containing an alkyl group) below was used instead of maleimide compound 1. The reaction rate was 50%.

[0167] Maleimide compound 2 (alkyl-free maleimide compound): a maleimide compound other than the maleimide compound (a2) (a maleimide compound not having an alkyl group having 6 or more carbon atoms) [BMI-1500 manufactured by Designer Molecules Inc., a maleimide compound represented by the following formula (10)]

[0168] In formula (10), m represents 1 to 10.

[0169] (Reactive Compound (B)) Acenaphthylene compound: acenaphthylene (manufactured by JFE Chemical Corporation) Modified PPE: polyphenylene ether compound having a methacryloyl group at its terminal (SA9000 manufactured by SABIC Innovative Plastics, a modified polyphenylene ether in which the terminal hydroxyl group of polyphenylene ether is modified with a methacryloyl group, weight average molecular weight Mw 2000)

[0170] (Reaction initiator) Peroxide: α,α'-di(t-butylperoxy)diisopropylbenzene (Perbutyl P (PBP) manufactured by NOF Corporation) Azo compound: 2,2'-azobis(2,4,4-trimethylpentane) (VR-110 manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.)

[0171] (Free Radical Compound) Free Radical Compound: 4-Hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl Free Radical (LA-7RD manufactured by ADEKA Corporation)

[0172] (Silane Coupling Agent) Silane coupling agent: 3-methacryloxypropyltrimethoxysilane (a silane coupling agent having a methacryl group in the molecule, KBM503 manufactured by Shin-Etsu Chemical Co., Ltd.)

[0173] (Flame retardant) Compatible phosphorus-based flame retardant: aromatic condensed phosphate ester compound (PX-200 manufactured by Daihachi Chemical Industry Co., Ltd.) Incompatible phosphorus-based flame retardant: diphenylphosphine oxide compound (PQ60 manufactured by Shinichi Chemical Co., Ltd.)

[0174] (Inorganic filler) Silica filler: EQ2410-SMC (TAT) manufactured by Zhejiang Sanshiki New Material Technology Co., Ltd.

[0175] [Preparation Method] First, each component other than the inorganic filler was added to toluene and mixed to a solids concentration of 35% by mass in the composition (parts by mass) shown in Table 1. The mixture was stirred for 60 minutes. Thereafter, the inorganic filler was added to the resulting mixture in the composition (parts by mass) shown in Table 1, and the inorganic filler was dispersed using a bead mill. This resulted in a varnish-like resin composition (varnish).

[0176] Next, a prepreg was obtained as follows.

[0177] The resulting varnish was impregnated into a fibrous substrate (glass cloth: #1078 type, L2 glass, manufactured by Asahi Kasei Corporation) and then heated and dried at 130°C for 3 minutes to produce a prepreg. The content of the components that constitute the resin by the curing reaction (resin content) relative to the prepreg was adjusted to approximately 66% by mass. Furthermore, the thickness after curing was adjusted to 77 μm.

[0178] An evaluation substrate (metal-clad laminate) was obtained as follows.

[0179] Two sheets of the obtained prepreg were stacked, and 18 μm thick copper foil (CF-T4X-SV-18 manufactured by Fukuda Metal Foil & Powder Co., Ltd.) was placed on both sides. This was used as a pressure body, and heated to a temperature of 200°C at a temperature increase rate of 3°C / min, and then heated and pressurized at 200°C for 120 minutes under a pressure of 3 MPa, to obtain an evaluation substrate (metal-clad laminate) with copper foil bonded to both sides and a resin layer thickness of approximately 154 μm.

[0180] The evaluation substrate prepared as described above was evaluated by the following method.

[0181] [Dielectric Properties (Dielectric Constant Dk and Dielectric Loss Tangent Df)] The copper foil was removed from the evaluation board by etching. The resulting board was used as a test piece, and the dielectric constant and dielectric loss tangent at 10 GHz were measured using a cavity resonator perturbation method. Specifically, the dielectric constant (Dk) and dielectric loss tangent (Df) of the test piece at 10 GHz were measured using a network analyzer (N5230A manufactured by Keysight Technologies, Inc.). If the measured dielectric constant Dk was less than 3.5, it was judged as "passed." Furthermore, if the measured dielectric loss tangent Df was less than 0.00215, it was judged as "passed."

[0182] [Copper Foil Peel Strength] The metal foil (copper foil) was peeled from the evaluation substrate (metal-clad laminate), and the peel strength at this time was measured in accordance with JIS C 6481 (1996). Specifically, the copper foil was peeled from the evaluation substrate at a rate of 50 mm / min using a tensile tester, and the peel strength (N / mm) at this time was measured. This peel strength is the copper foil peel strength, and the higher this is, the higher the adhesion of the metal foil (copper foil). If the measured copper foil peel strength was more than 0.50 N / mm, it was judged to be "passed."

[0183] [Interlayer Peel Strength] The insulating layer (prepreg) on ​​the top surface of the evaluation substrate (metal-clad laminate) was peeled off at a rate of 50 mm / min using a tensile tester (i.e., the insulating layer on the top surface was peeled off from the insulating layer underneath), and the peel strength (N / mm) at this time was measured. This peel strength is the interlayer peel strength. It was found that the higher this peel strength, the higher the interlayer adhesion, and if the measured interlayer peel strength was more than 0.45 N / mm, it was judged to be "passed."

[0184] [Compatibility] First, an evaluation substrate for evaluating compatibility was prepared. Specifically, the evaluation substrate for evaluating compatibility was prepared by first applying a varnish-like resin composition (varnish) produced when producing the evaluation substrate (metal-clad laminate) to a glass plate so that the thickness after curing was 100 μm, and then placing it in a dryer set at 120 ° C. and heating it for 3 minutes to obtain an evaluation substrate (film). The haze of the evaluation substrate (film) formed on the glass plate (the haze of the evaluation substrate with the glass plate still attached) was measured using a spectrophotometer (Spectrophotometer CM-5 manufactured by Konica Minolta, Inc.). If the obtained haze was 2 or less, the compatibility was sufficiently high and judged to be "pass." In this case, it is shown as "pass" in Table 1. Furthermore, if the obtained haze was more than 2, it was judged to have insufficient compatibility. In this case, it is shown as "fail" in Table 1.

[0185] [Glass transition temperature (Tg)] An unclad plate obtained by etching away the metal foil (copper foil) from the evaluation substrate (metal-clad laminate) was used as a test piece, and the glass transition temperature Tg of the cured resin composition was measured using a viscoelasticity spectrometer "DMS6100" manufactured by Seiko Instruments Inc. At this time, dynamic viscoelasticity measurement (DMA) was performed with a bending module at a frequency of 10 Hz, and the temperature at which tan δ was maximized when the temperature was raised from room temperature to 340 ° C. at a heating rate of 5 ° C. / min was taken as the glass transition temperature Tg (° C.). The glass transition temperature Tg obtained at this time is shown in Table 1 as glass transition temperature 1. Thereafter, after cooling to room temperature, the glass transition temperature Tg (° C.) was measured using the same method as above. The glass transition temperature Tg obtained at this time is shown in Table 1 as glass transition temperature 2. If the measured glass transition temperature 1 and the measured glass transition temperature 2 were both 190 ° C. or higher, it was judged to be "passed."

[0186] The results are shown in Table 1.

[0187]

[0188] From Table 1, it was found that when the resin compositions contained a pre-reactant (A) obtained by pre-reacting a mixture containing the polyfunctional vinyl aromatic copolymer (a1) and the maleimide compound (a2) (Examples 1 to 3), they were excellent in low dielectric properties and adhesion to metal foil, and furthermore, they were resin compositions that gave cured products with excellent compatibility compared to when the pre-reactant (A) was not contained (Comparative Examples 1 to 3). Furthermore, it was found that the resin compositions according to Examples 1 to 3 were resin compositions that gave cured products with high glass transition temperatures, excellent heat resistance, and excellent not only in adhesion to metal foil but also in interlayer adhesion.

[0189] This application is based on Japanese Patent Application No. 2023-202050 filed on November 29, 2023, the contents of which are incorporated herein by reference.

[0190] In order to express the present invention, the present invention has been properly and sufficiently described through the embodiments in the above, but it should be recognized that those skilled in the art can easily change and / or improve the above-mentioned embodiments. Therefore, unless the changes or improvements made by those skilled in the art are at a level that causes departure from the scope of the claims described in the claims, such changes or improvements are interpreted as being included in the scope of the claims.

[0191] According to the present invention, there is provided a resin composition which can give a cured product having excellent compatibility and adhesion to metal foil while maintaining excellent low dielectric properties. Also, according to the present invention, there are provided a prepreg, a resin-coated film, a resin-coated metal foil, a metal-clad laminate, and a wiring board which can be obtained using the resin composition.

Claims

1. A resin composition comprising a pre-reactant (A) obtained by reacting in advance a mixture containing a polyfunctional vinyl aromatic copolymer (a1) containing a repeating unit derived from a divinyl aromatic compound and a maleimide compound (a2) having an alkyl group having 6 or more carbon atoms and an alkylene group having 6 or more carbon atoms.

2. The resin composition according to claim 1, wherein the polyfunctional vinyl aromatic copolymer further contains a repeating unit derived from a monovinyl aromatic compound.

3. The resin composition according to claim 1, wherein the mass ratio of the polyfunctional vinyl aromatic copolymer (a1) to the maleimide compound (a2) is 10:90 to 90:

10.

4. The resin composition according to claim 1, wherein the maleimide compound (a2) has a weight average molecular weight of 500 to 4,000.

5. The resin composition according to claim 1, further comprising an inorganic filler.

6. The resin composition according to claim 1, further comprising a flame retardant.

7. The resin composition according to claim 1, further comprising a reactive compound (B) which reacts with the preliminary reactant (A), wherein the reactive compound (B) comprises at least one selected from the group consisting of allyl compounds, methacrylate compounds, acrylate compounds, acenaphthylene compounds, vinyl compounds, isocyanurate compounds, polyphenylene ether compounds having a carbon-carbon unsaturated double bond in the molecule, and maleimide compounds other than the maleimide compound (a2).

8. A prepreg comprising the resin composition according to any one of claims 1 to 7 or a semi-cured product of said resin composition and a fibrous base material.

9. A resin-coated film comprising a resin layer containing the resin composition according to any one of claims 1 to 7 or a semi-cured product of said resin composition, and a support film.

10. A resin-coated metal foil comprising a resin layer containing the resin composition according to any one of claims 1 to 7 or a semi-cured product of said resin composition, and a metal foil.

11. A metal-clad laminate comprising an insulating layer containing a cured product of the resin composition according to any one of claims 1 to 7, and a metal foil.

12. A metal-clad laminate comprising an insulating layer containing the cured product of the prepreg according to claim 8 and a metal foil.

13. A wiring board comprising an insulating layer containing a cured product of the resin composition according to any one of claims 1 to 7, and wiring.

14. A wiring board comprising an insulating layer containing the cured product of the prepreg according to claim 8 and wiring.

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